Occlusion and TMJ + Tooth Replacement By Dr Cheryl Fu Occlusion and TMJ + Tooth Replacement By Dr Cheryl Fu # Learning Outcomes **THE UNIVERSITY OF** **WESTERN** **AUSTRALIA** * Recap on key concepts of occlusion: Centric Relation, Maximum Intercuspation Position (see 2025 occlusion lectures for full slides) * Discuss clinical implications of pathological adaptations caused by malocclusion. * Recap the envelope of function * Review the criteria for the ideal occlusion and how to assess clinically. * Tooth replacement options (including immediate replacement options) Whilst theoretical background knowledge is important, as this module focuses on the “clinical” aspects, we will try to keep the topic relevant. **As these lectures are given as a guest for “Clinical Practice 3”, these concepts will not be directly assessed for the FPD/RPD module, unless the content is also covered in the prosthodontic module. However, you are expected to retain knowledge from previous years.** #### Core Objectives - Recap on key concepts of occlusion: Centric Relation, Maximum Intercuspation Position (see 2025 occlusion lectures for full slides) - Discuss clinical implications of pathological adaptations caused by malocclusion - Recap the envelope of function - Review the criteria for the ideal occlusion and how to assess clinically - Tooth replacement options (including immediate replacement options) #### Clinical Focus and Assessment Whilst theoretical background knowledge is important, as this module focuses on the "clinical" aspects, we will try to keep the topic relevant. As these lectures are given as a guest for "Clinical Practice 3", these concepts will not be directly assessed for the FPD/RPD module, unless the content is also covered in the prosthodontic module. However, you are expected to retain knowledge from previous years. # Occlusion **[JPD]** **THE JOURNAL OF PROSTHETIC DENTISTRY** **[THE GLOSSARY OF PROSTHODONTIC TERMS]** **Ninth Edition** *** \+Occlusion <sup>[Univ of WA]</sup> **occlusion \a-klō' shun\** <sup>n</sup> (1645): **1.** the act or process of closure or of being closed or shut off; **2.** the static relationship between the incising or masticating surfaces of the maxillary or mandibular teeth or tooth analogues; <sub>comp</sub>: **ARTICULATION**, **CENTRIC OCCLUSION**, **COMPONENTS OF OCCLUSION**, **ECCENTRIC OCCLUSION**, **LINE OF OCCLUSION**, **LINEAR OCCLUSION**, **MONOPLANE OCCLUSION**, **PATHOGENIC OCCLUSION**, **SPHERICAL FORM OF OCCLUSION**   #### Definition of Occlusion **occlusion \ə-klō' zhən\** *n* (1645): 1. The act or process of closure or of being closed or shut off. 2. The static relationship between the incising or masticating surfaces of the maxillary or mandibular teeth or tooth analogues. **Related Components:** - Articulation - Centric Occlusion - Components of Occlusion - Eccentric Occlusion - Line of Occlusion - Linear Occlusion - Monoplane Occlusion - Pathogenic Occlusion - Spherical Form of Occlusion Logo for 'JPD THE JOURNAL OF PROSTHETIC DENTISTRY' featuring stylized red letters 'JPD' above the full journal name. Title block text: 'THE GLOSSARY OF PROSTHODONTIC TERMS' in orange and black fonts, indicating the source of the definition. Occlusion An ideal occlusion is defined as “the maxillary and mandibular teeth contact simultaneously when the condylar processes are fully seated in the mandibular fossae, and the teeth do not interfere with harmonious movement of the mandible during function. Ideally, in the fully bilateral seated position of the condyle– articular disk assemblies, the maxillary and mandibular teeth exhibit maximum intercuspation. This means that the maxillary lingual and mandibular buccal cusps of the posterior teeth are evenly distributed and in stable contact with the opposing occlusal fossae. These functional cusps can then act as stops for vertical closure without excessively loading any one tooth, while left and right TMJs concurrently are in an unstrained position.” Contemporary Fixed Prosthodontics An ideal occlusion is defined as "the maxillary and mandibular teeth contact simultaneously when the condylar processes are fully seated in the mandibular fossae, and the teeth do not interfere with harmonious movement of the mandible during function. Ideally, in the fully bilateral seated position of the condyle–articular disk assemblies, the maxillary and mandibular teeth exhibit maximum intercuspation. This means that the maxillary lingual and mandibular buccal cusps of the posterior teeth are evenly distributed and in stable contact with the opposing occlusal fossae. These functional cusps can then act as stops for vertical closure without excessively loading any one tooth, while left and right TMJs concurrently are in an unstrained position." *Source: Contemporary Fixed Prosthodontics* **Importance of Occlusion** Occlusal disharmony can cause a variety of issues: * Attrition * Splayed teeth * Sore/sensitive teeth * Mobility/occlusal fremitus * Re-occurring failure of restorations/ cracked teeth * + more Occlusal disharmony can cause a variety of issues: - Attrition - Splayed teeth - Sore/sensitive teeth - Mobility/occlusal fremitus - Re-occurring failure of restorations/cracked teeth **Attrition** Defined as wear due to “tooth-on tooth” friction Usually from bruxism    #### Definition Attrition is defined as wear due to "tooth-on-tooth" friction. It usually results from bruxism. Clinical intraoral photograph showing anterior teeth with significant attrition (wear). The image demonstrates flattened incisal edges and loss of tooth structure consistent with 'tooth-on-tooth' friction from bruxism as defined in the slide. Clinical intraoral photograph showing a lateral view of posterior teeth exhibiting severe attrition. The occlusal surfaces are worn down, demonstrating the extent of tooth-on-tooth contact damage. Clinical intraoral photograph showing another angle of posterior teeth with extensive wear facets on the occlusal surfaces, consistent with bruxism-induced attrition. <!-- **Attrition** The University of Western Australia -->  The University of Western Australia Clinical intraoral photograph showing the mandibular anterior teeth with visible wear facets on the incisal edges. Red arrows point to specific areas of attrition or restorations. The image is relevant to the text's discussion on diagnosing attrition patterns, such as those caused by deflective interferences or poorly shaped restorations. **Splayed Teeth** Same type of forces that cause tooth wear can also force anterior teeth forwards. Possible causes: * Loss of posterior support (posterior teeth are better at supporting the occlusal forces) * Anterior teeth take excessive occlusal load   The same type of forces that cause tooth wear can also force anterior teeth forwards. #### Possible Causes - **Loss of posterior support:** Posterior teeth are better at supporting occlusal forces. - **Excessive load:** Anterior teeth take excessive occlusal load. Clinical photo of a patient's anterior teeth showing splayed (flared) incisors and canines. The upper arch is crowded and the teeth are not aligned in a straight line. Close-up clinical photo of a patient's lower anterior teeth demonstrating splaying due to excessive occlusal load or lack of posterior support. Note the proclination of the lower central and lateral incisors. Sore/Sensitive Teeth Compression of periodontal ligament can cause tenderness during percussion/pressure Occlusal overload can also cause hypersensitivity of the pulp **May be due to occlusal** interferences from **restorations**, or general occlusal overload/bruxism. If you recently placed a restoration on the tooth or opposing tooth, please check bite again. Sometimes patient fail to do their full envelope of motion when you check with articulating paper. Also hard to tell when they are numb.  #### Clinical Presentation - **Periodontal Tenderness:** Compression of the periodontal ligament can cause tenderness during percussion or pressure. - **Hypersensitivity:** Occlusal overload can cause hypersensitivity of the pulp. #### Etiology and Management - May be due to occlusal interferences from restorations, or general occlusal overload/bruxism. - If a restoration was recently placed on the tooth or opposing tooth, check the bite again. - Patients may fail to perform their full envelope of motion during checks with articulating paper, especially when numb. Lateral skull anatomical diagram illustrating the temporomandibular joint (TMJ) and associated musculature. The image depicts the condyle within the glenoid fossa, with surrounding muscle groups shaded to indicate tension or involvement. This visual supports the OCR text regarding occlusal overload and bruxism affecting the periodontal ligament and pulp hypersensitivity. **Hypermobility** The University of Western Australia * Occlusal fremitus from occlusal overload * Can usually see widening of the PDL, with absence of apical radiolucency consistent with infections. * Should check occlusal contacts for deflective contacts or occlusal overload and adjust if required.  #### Clinical Observations - Occlusal fremitus resulting from occlusal overload. - Radiographic evidence usually shows widening of the PDL, with an absence of apical radiolucency consistent with infections. #### Management - Check occlusal contacts for deflective contacts or occlusal overload. - Adjust occlusion if required. Clinical radiograph demonstrating Hypermobility findings. The image shows two teeth with a red arrow pointing to occlusal fremitus from occlusal overload and black arrows indicating the widening of the Periodontal Ligament (PDL). Yellow lines trace the PDL space, illustrating the absence of apical radiolucency consistent with infections. **Cracked teeth/restorations** * Fracture of cusps or other restorative material from heavy loading. * Often seen in occurring to the last couple of teeth in the arch which takes considerable occlusal forces. **THE UNIVERSITY OF WESTERN AUSTRALIA** > J Endod. 2016 Apr;42(4):557-62. doi: 10.1016/j.joen.2016.01.014. Epub 2016 Mar 2. **Cracked Teeth: Distribution, Characteristics, and Survival after Root Canal Treatment** Sung Hyun Kang 1, Bom Sahn Kim 2, Yemi Kim 3 **Results:** One hundred seventy-five teeth were diagnosed with cracks. Most of the patients were aged 50-60 years (32.0%) or over 60 (32.6%). The lower second molar was the most frequently (25.1%) affected tooth. Intact teeth (34.3%) or teeth with class I cavity restorations (32.0%) exhibited a higher incidence of cracks. The 2-year survival rate of 88 cracked teeth after RCT was 90.0%. A probing depth of more than 6 mm was a significant prognostic factor for the survival of cracked teeth restored via RCT. The survival rate of root-filled cracked teeth with a probing depth of more than 6 mm was 74.1%, which is significantly lower than that of teeth with probing depths of less than 6 mm (96.8%) (P = .003).  #### Clinical Characteristics - Fracture of cusps or restorative material from heavy loading. - Often occurs on the last teeth in the arch, which sustain considerable occlusal forces. #### Research Findings (J Endod. 2016) - **Demographics:** Most patients were aged 50–60 (32.0%) or over 60 (32.6%). - **Frequency:** The lower second molar was the most frequently affected tooth (25.1%). - **Tooth Condition:** Intact teeth (34.3%) or teeth with Class I restorations (32.0%) showed a higher incidence of cracks. - **Survival:** The 2-year survival rate after Root Canal Treatment (RCT) was 90.0%. - **Prognosis:** Probing depth >6 mm is a significant negative prognostic factor (74.1% survival vs. 96.8% for depths <6 mm). Clinical intraoral photo showing a molar tooth with a visible fracture of the occlusal surface and restorative material. A dental explorer probe is inserted into the crack to demonstrate the extent of the fracture. The image visually demonstrates the 'Fracture of cusps or other restorative material from heavy loading' described in the slide text. **Determinants of Occlusion** Have you ever wondered why the the opening of the mouth has both a hinge and translatory movement? **Disclaimer:** This fantastic explanation is by Peter Dawson in the textbook “Functional Occlusion”, I did not invent it    #### Determinants of Occlusion The opening of the mouth involves both hinge and translatory movements. This explanation is based on Peter Dawson's "Functional Occlusion." Lateral view diagram of a human skull with a red circle highlighting the temporomandibular joint (TMJ) area. This panel appears to be part of a sequence illustrating the mechanics of jaw movement. Lateral view diagram of a human skull showing the mandible in an open position. A red arrow points towards the TMJ region, likely indicating the hinge axis or initial movement point during mouth opening. Lateral view diagram of a human skull and cervical spine. Red arrows indicate translatory (sliding) movement of the condyle forward within the glenoid fossa, demonstrating the second phase of mouth opening alongside the hinge movement shown previously. # TMJ <table><tbody><tr><td>The temporomandibular joint is comprised of:<br/>Condyle head<br/>Articular disc (dense connective tissue)<br/>Glenoid fossa<br/><br/>You have already been delivered lectures on the TMJ (in previous years such as anatomy units). I will not be going over this topic in great detail for today. Please revise in your own time if you have forgotten!</td></tr></tbody></table>  #### Components of the TMJ - Condyle head - Articular disc (dense connective tissue) - Glenoid fossa Labelled anatomical diagram of the temporomandibular joint (TMJ). The image shows a cross-section with red arrows pointing to specific structures. Visible labels include 'articular disc', 'retrodiscal attachment (bilaminar zone)', 'anterior ligamentous attachment', and 'posterior ligamentous attachment'. Also labeled is the 'superior head of lateral pterygoid muscle'. TMJ The temporomandibular joint is capable of both hinging and gliding motions (ginglymoathrodial). • During the first part of opening (<2cm), the condyle rotates WITHIN the glenoid fossa about the intra-condylar axis    #### Ginglymoarthrodial Motion The joint is capable of both hinging and gliding motions. - **Initial Opening (<2cm):** The condyle rotates within the glenoid fossa about the intra-condylar axis. Labelled anatomical diagram of the temporomandibular joint (TMJ) showing internal structures. Labels include 'articular disc', 'retrodiscal attachment (bilaminar zone)', 'posterior ligamentous attachment', 'anterior ligamentous attachment', and 'superior head of lateral pterygoid muscle'. A white arrow indicates the direction of muscle contraction or movement. Illustration demonstrating the hinging motion of the TMJ during opening. Shows the condyle rotating within the glenoid fossa about an intra-condylar axis, indicated by a curved blue arrow with a red outline. Illustration continuing to demonstrate the first part of mouth opening (<2cm). The condyle is shown in its initial position within the glenoid fossa, with a large blue arrow indicating the direction of rotation about the intra-condylar axis as described in the text. # TMJ The temporomandibular joint is capable of both hinging and gliding motions (ginglymoathrodial). * During the second part of opening(>2cm), there is a translational movement as the condyle glides against the articular eminence.    #### Translational Movement - **Advanced Opening (>2cm):** A translational movement occurs as the condyle glides against the articular eminence. Anatomical diagram of the temporomandibular joint (TMJ) showing key structures: superior head of lateral pterygoid muscle, anterior ligamentous attachment, articular disc, retrodiscal attachment (bilaminar zone), posterior ligamentous attachment, and condyle. Arrows indicate movement direction. Illustration demonstrating hinging motion in the TMJ during jaw opening. A blue curved arrow shows rotational movement of the mandibular condyle within the glenoid fossa without translation. Illustration demonstrating translational motion in the TMJ during wide mouth opening (>2cm). A blue straight arrow indicates forward glide of the condyle against the articular eminence, as described in OCR text. **TMJ – Excursive movements** Other than just opening and closing that would produce static occlusal contacts, a wide array of excursive movements are possible through different movements of the condyles **Protrusive movements:** Both condyles move in gliding motion forwards **Lateral movements:** * **Working side rotates about the vertical axis without leaving the glenoid fossa** * **Non-working side has a gliding path against the articular eminence.** </img>  #### Movement Types - **Protrusive movements:** Both condyles move in a forward gliding motion. - **Lateral movements:** - **Working side:** Rotates about the vertical axis without leaving the glenoid fossa. - **Non-working side:** Follows a gliding path against the articular eminence. Lateral movements diagram: Shows the mandible and TMJ anatomy with a vertical axis line passing through the condyles. Arrows indicate rotational movement on one side and gliding motion on the other, illustrating working side rotation about the vertical axis without leaving the glenoid fossa and non-working side gliding path against the articular eminence. **Protrusive Movements** The angle of the movement downwards is hence determined by the articular eminence. This termed “condylar angle” or “guidance inclination”. **FIGURE 4-10** ✦ Protrusive mandibular movement in the horizon- tal plane. **FIGURE 4-12** ✦ Protrusive movement in the frontal plane. Images from Contemporary Fixed Prosthodontics    #### Condylar Guidance The angle of downward movement is determined by the articular eminence. This is termed the "condylar angle" or "guidance inclination." - Protrusive mandibular movement occurs in both the horizontal and frontal planes. Anatomical diagram of the temporomandibular joint (TMJ) illustrating protrusive movement. A blue arrow indicates the downward and forward path of the condyle relative to the articular eminence. Red lines trace the trajectory within the joint space. FIGURE 4-10: Diagram showing the mandible in a horizontal plane with red arrows indicating protrusive movement at the condyles. Caption: 'Protrusive mandibular movement in the horizontal plane'. FIGURE 4-12: Diagram showing the mandible in a frontal plane with red arrows indicating protrusive movement at the condyles. Caption: 'Protrusive movement in the frontal plane'. TMJ – Condylar Angle/Inclination THE UNIVERSITY OF WESTERN AUSTRALIA Condylar angle (guidance inclination) Slide by Dr Matsubara and Dr Nedelcu  #### Condylar Angle Condylar angle (guidance inclination) refers to the path established by the TMJ during excursive movements. Labelled diagram showing a human mandible with two red rectangular boxes highlighting the condylar regions. Inside each box are yellow circles and arrows indicating movement or orientation of the condyle. Blue and yellow arrows outside the boxes point to angular relationships. A legend in the bottom-left shows an angle labeled 'Condylar angle (guidance inclination)' with colored lines matching those in the main image. The diagram visually demonstrates the concept of condylar guidance inclination as described in the OCR text. **Excursive Movements** During lateral excursive movements, the principal movement is on the non-working side. * Head of condyle of the non-working side moves forward, downward and medially * The downward angle is limited by the articular eminence (condylar angle) * The maximal angle of medial movement is the Bennet angle. (Formal definition “angle formed between the sagittal plane and the average path of the advancing condyle as viewed in horizontal plane during lateral mandibular movement.) * The angle between the protrusive movement and lateral excursive movement of the non-working side is the Fisher angle. It is thought that the lateral condylar path is steeper than the protrusive path (glenoid fossa/condyle isn’t a sphere). #### Lateral Excursive Dynamics During lateral movements, the principal movement occurs on the non-working side: - **Non-working condyle path:** Moves forward, downward, and medially. - **Condylar Angle:** The downward angle limited by the articular eminence. - **Bennett Angle:** The angle formed between the sagittal plane and the average path of the advancing condyle as viewed in the horizontal plane. - **Fisher Angle:** The angle between the protrusive path and the lateral excursive path of the non-working side. The lateral path is typically steeper than the protrusive path. # TMJ – Bennet Angle **Bennet angle** **Fisher angle** Slide by Dr Matsubara and Dr Nedelcu  #### Angular Relationships - Bennett angle - Fisher angle Annotated anatomical diagram of a human mandible with two red wireframe boxes highlighting the temporomandibular joint (TMJ) regions. Left box shows multi-directional colored arrows (blue, yellow, green, magenta) indicating movement vectors; right box shows a single green curved arrow around the condyle, illustrating rotational motion. Yellow circles mark key points at the TMJ articulation. Below the image, labeled legends identify 'Bennet angle' and 'Fisher angle' with corresponding directional arrow graphics. The diagram visually demonstrates angular movements of the jaw during occlusion, critical for understanding Bennett shift mechanics. **Excursive Movements** The lateral movement of the non-working condyle (**Bennett side shift**) is also not a linear movement. It is comprised of: * **Immediate side shift** (The non-working condyle moves straight medially) * **Progressive side shift** (The non-working condyle moves from where it end up in immediate side shift, and translates laterally in a curve) **Fundamentals of Fixed Prosthodontics**  #### Components of Side Shift The lateral movement of the non-working condyle is non-linear and consists of: 1. **Immediate side shift:** The non-working condyle moves straight medially. 2. **Progressive side shift:** The non-working condyle translates laterally in a curve from the end of the immediate side shift. Lateral schematic diagram illustrating 'Excursive Movements' and the 'Bennett side shift'. The image depicts two mandibular rami: the left labeled 'NW' (Non-Working) and the right labeled 'W' (Working). It shows the condyle C on the NW side moving to position B via a shaded trajectory, indicating an immediate medial shift followed by a progressive lateral curve. Key labels include 'THA', 'S', 'S'', and 'HTS', with arrows indicating movement directions. Bennett Side Shift Progressive Bennett side shift Immediate Bennett side shift Slide by Dr Matsubara and Dr Nedelcu THE UNIVERSITY OF WESTERN AUSTRALIA  #### Bennett Side Shift Types - Progressive Bennett side shift - Immediate Bennett side shift Diagram illustrating the Bennett Side Shift of the mandible. It shows a lateral view of a human skull with the condyle highlighted within red bounding boxes representing the glenoid fossa. Arrows indicate movement: yellow arrows show translation, green arrows show rotation, and a purple line indicates the axis of rotation. Labels 'Progressive Bennett side shift' and 'Immediate Bennett side shift' are present in a blue inset box with colored vectors. # Excursive Movements **FIGURE 4-9** Right lateral mandibular movement in the horizontal plane. **FIGURE 4-11** Lateral movement in the frontal plane.   #### Mandibular Movement Planes - Right lateral mandibular movement in the horizontal plane. - Lateral movement in the frontal plane. FIGURE 4-9: Diagram showing right lateral mandibular movement in the horizontal plane. The illustration depicts a side view of the mandible with condyles shown in green and red arrows indicating downward and forward rotation at the TMJ. FIGURE 4-11: Diagram illustrating lateral movement in the frontal plane. The image shows a frontal view of the mandible with blue shaded regions on both sides and a red arrow pointing downward from above to indicate the direction of movement. Condylar Angle and Bennet Angle THE UNIVERSITY OF WESTERN AUSTRALIA To accurately reflect the relationship and movement of the patient’s jaw, we may wish to replicate the condylar angle and the Bennet angle.  #### Clinical Replication To accurately reflect patient jaw relationships, clinicians may replicate the condylar angle and the Bennett angle. Labelled diagram of a dental articulator (specifically a semi-adjustable type) demonstrating the replication of condylar and Bennett angles. The central image shows the mechanical structure with red arrows pointing to specific components and callouts describing their functions: 'Condyle guide inclination: -20~60° adjustable', 'Bennett angle is adjustable from 0 to 30° (with Gilbach's condyle)', 'The cutting guide pin is adjustable from 5 to 10mm on the bottom', 'Cutting guide disc 15°, 0° flat disc 5°/10°/20° equal slope cutting guide disc can be customized', and 'Can be installed with Gilbach trapezoidal magnetic plate, general circular magnetic plate and other accessories'. Smaller inset photos show close-ups of the adjustment knobs and positioning screws. Angle of Bennet Average of 15 degree Slide by Dr Matsubara and Dr Nedelcu  #### Average Values - The Bennett angle averages approximately 15 degrees. Diagram illustrating the Bennett angle in a mandibular movement model. Features red curved lines representing muscle or ligament paths connecting two red circular nodes at the top (representing condyles) to a central junction point below. A yellow curved arrow indicates the direction of movement. On the right side, blue and yellow lines converge at the lower node, indicating the angle measurement. Text annotations include 'Bennett Angle' at the top left, 'Bennett angle Average of 15 degree' at the bottom right, and 'Slide by Dr Matsubara and Dr Nedelcu' at the bottom.  The University of Western Australia logo featuring a shield with a swan and text 'SEEK WISDOM'. **Posselts Envelope** Posterior and anterior determinants of mandibular movements: * **Posterior:** Shape of the articular eminence, configuration of the condyles, etc. (Not affected by dentist) * **Anterior:** The palatal surface of maxillary anterior teeth and labial surfaces of mandibular incisors. Review in your own time if needed, this was covered last year in DMD2  #### Determinants of Movement - **Posterior Determinants:** Shape of the articular eminence and configuration of the condyles (anatomical factors not affected by the dentist). - **Anterior Determinants:** The palatal surface of maxillary anterior teeth and labial surfaces of mandibular incisors. Posselt's Envelope diagram illustrating mandibular movements. The visual shows a curved boundary representing the range of motion starting from 'True Hinge Axis Rotation' and extending to 'Maximal Opening'. Labels along the curve include 'Centric Relation', 'MIP' (Maximum Intercuspation), 'Edge to Edge', and 'Maximum Protrusion'. Arrows indicate translational and rotational components. **Anterior teeth** When you are placing restorations that involve a large portion of the incisal area, please be aware of the **SHAPE** of the tooth. The incisors are not a “rectangle”, but have various curves/bends that serve for anterior guidance. #### Incisal Morphology When placing restorations in the incisal area, the specific shape of the tooth is critical. Incisors are not simple rectangles; they possess curves and bends essential for anterior guidance. **Anterior teeth** Note all the planes to the tooth The top half of the labial plane emerges with a prominent curve at the gingival embrasure, but overall follows the contours of the alveolar process Please note we are not covering all aspects of smile design. Comprehensive smile design is out of the scope of all of us. I just want to draw your attention to the shape of the incisors for the purpose of direct restorations (that do not require any changes in occlusion) Image from “Functional occlusion” textbook  #### Tooth Planes - The labial plane has multiple contours. - The top half emerges with a prominent curve at the gingival embrasure, following the alveolar process contours. - Proper contouring is necessary for direct restorations to maintain existing occlusion. Labelled diagram of an anterior tooth outline overlaid on a grid. The diagram illustrates the planes of the tooth with specific annotations: red arrows point to the labial plane and gingival embrasure curve; blue arrows indicate the vertical alignment along the alveolar process contours. Text context identifies this as a visual aid for direct restorations focusing on incisor shape. **Anterior teeth** **The University of Western Australia** **FIGURE 17-6** Modification of the provisional restorations can sometimes require major reduction of the labial contour. **A**, On this patient with a tight neutral zone from strong lower-lip pressure, the reduction obliterated the labial embrasure contours to achieve an unstrained lip-closure path. There is no way to know this contour from the articulator mounting. If the original diagnostic wax-up had been accepted, the incisal edges would have been too far forward. After the labial contours are determined to be satisfactory (**B**), the vertical position of the incisal plane can be established and the labio-incisal contours can be further refined within a correct matrix of functional anatomy. Image from “Functional occlusion” textbook The lower half of the labial surface is in a **DIFFERENT PLANE** to the gingival half. The surface should be contoured in a way that allows the lower lip to comfortably slide by the incisal third of the tooth, to contact the top lip. Have you noted that when we prepare an anterior tooth for a crown, we also have **TWO planes**?  #### Labial Contours and Function - The lower half of the labial surface exists in a different plane than the gingival half. - Contouring must allow the lower lip to slide comfortably by the incisal third to contact the top lip. - Crown preparations for anterior teeth should reflect these two distinct planes. - Adjustments to provisional restorations may be required to achieve an unstrained lip-closure path. Labelled clinical diagram (FIGURE 17-6) illustrating the modification of provisional restorations for anterior teeth. The figure is split into two panels: Panel A shows a patient with a tight neutral zone where strong lower-lip pressure has obliterated labial embrasure contours; Panel B depicts the corrected state after reduction, showing satisfactory labial contours and proper vertical position of the incisal plane. Green arrows indicate the lip-closure path and contact points. **Anterior teeth** FIGURE 17-7 The incisal plane should follow the contour of the lower lip when the patient smiles.  #### Esthetic Alignment The incisal plane should follow the contour of the lower lip when the patient smiles. Figure 17-7: A grid-based diagram of lips with red lines indicating the incisal plane following the contour of the lower lip when the patient smiles. # Terminology **maximal intercuspal position** \măkˈsə-mal ˈin-ˌter-ˌküs-ˈpal ˌpa-zishˈan\: **acronym** is MIP; the complete intercuspation of the opposing teeth independent of condylar position, sometimes referred to as the best fit of the teeth regardless of the condylar position; *comp*, CENTRIC OCCLUSION **centric relation** \sen¨ˈtrik ˈrī-lāˈshun\: **acronym** is CR; a max-illomandibular relationship, independent of tooth contact, in which the condyles articulate in the anterior-superior position against the posterior slopes of the articular eminences; in this position, the mandible is restricted to a purely rotary movement; from this un-strained, physiologic, maxillomandibular relationship, the patient can make vertical, lateral or protrusive movements; it is a clinically useful, repeatable reference position University of Western Australia #### Key Definitions **Maximal Intercuspal Position (MIP):** The complete intercuspation of opposing teeth independent of condylar position. Also known as the "best fit" of teeth. **Centric Relation (CR):** A maxillomandibular relationship, independent of tooth contact, where condyles articulate in the anterior-superior position against the posterior slopes of the articular eminences. It is a repeatable, unstrained reference position where the mandible is restricted to purely rotary movement. When to use CR or MIP? Because CR is reproducible, and independent of dentition: • Complete dentures (patient HAS no MIP to start with) • Current occlusal scheme is to be changed (attrition etc) In the case of where you are using the existing occlusal scheme, MIP is more than sufficient. Slide by Dr Matsubara and Dr Nedelcu #### Clinical Application **Use Centric Relation (CR) when:** - Constructing complete dentures (no existing MIP). - Changing the current occlusal scheme (e.g., due to attrition). **Use Maximal Intercuspal Position (MIP) when:** - Utilizing the existing occlusal scheme for restorative procedures. **Dynamic occlusion** Dynamic occlusion: occlusal contacts when the mandible is moving. This is powered by the muscles of mastication, and the pathways are guided by the TMJ and dentition. This should make sense based on what we have just talked about in the first half of lecture regarding posselt’s envelope and the anterior and posterior determinants of occlusion! #### Definition Dynamic occlusion refers to occlusal contacts during mandibular movement. It is powered by masticatory muscles and guided by both the TMJ (posterior determinant) and dentition (anterior determinant). # **Occlusion** THE UNIVERSITY OF WESTERN AUSTRALIA An ideal occlusion is defined as “the maxillary and mandibular teeth contact simultaneously when the condylar processes are fully seated in the mandibular fossae, and the teeth do not interfere with harmonious movement of the mandible during function. Ideally, in the fully bilateral seated position of the condyle– articular disk assemblies, the maxillary and mandibular teeth exhibit maximum intercuspation. This means that the maxillary lingual and mandibular buccal cusps of the posterior teeth are evenly distributed and in stable contact with the opposing occlusal fossae. These functional cusps can then act as stops for vertical closure without excessively loading any one tooth, while left and right TMJs concurrently are in an unstrained position.” Contemporary Fixed Prosthodontics #### Ideal Occlusal State Ideal occlusion occurs when maxillary and mandibular teeth contact simultaneously while condyles are fully seated in the fossae. In this state, teeth do not interfere with harmonious mandibular movement. Functional cusps (maxillary lingual and mandibular buccal) should be evenly distributed in stable contact with opposing fossae to act as vertical stops. # Occlusion > An ideal occlusion is defined as "**the maxillary and mandibular teeth contact simultaneously when the condylar processes are fully seated in the mandibular fossae, and the teeth do not interfere with harmonious movement of the mandible during function.**" Ideally, in the fully bilateral seated position of the condyle–articular disk assemblies, the maxillary and mandibular teeth exhibit **maximum intercuspation**. This means that the maxillary lingual and mandibular buccal cusps of the posterior teeth are evenly distributed and in stable contact with the opposing occlusal fossae. These **functional cusps** can then act as stops for vertical closure without **excessively loading any one tooth**, while left and right **TMJs concurrently are in an unstrained position.** Contemporary Fixed Prosthodontics #### Summary of Ideal Criteria - Simultaneous tooth contact in the seated condylar position. - Maximum intercuspation coincides with the seated position. - Functional cusps provide stable stops for vertical closure. - No excessive loading on any single tooth. - TMJs remain in an unstrained position. **Ideal Occlusion** 1. Mandibular stability 2. Axial load 3. No interferences #### Primary Goals 1. Mandibular stability 2. Axial load 3. Absence of interferences # Ideal Occlusion **THE UNIVERSITY OF WESTERN AUSTRALIA** **Axial load:** * Occlusal forces distributed down the long axis of teeth for even distribution on the periododontal ligament fibres. #### Axial Loading Occlusal forces should be distributed down the long axis of the teeth. This ensures even distribution of forces across the periodontal ligament fibers. **Ideal Occlusion** Lateral excursive interferences. • Occlusal schemes: • Canine guidance (dentate) • Group function or unilaterally balanced occlusion (dentate) • Balanced occlusion (edentate) THE UNIVERSITY OF WESTERN AUSTRALIA  #### Occlusal Schemes - **Canine guidance:** Typical for dentate patients. - **Group function (Unilaterally balanced):** Alternative for dentate patients. - **Balanced occlusion:** Used for edentate patients. Anatomical figure of a human skull showing the dentition and jaw muscles. A red circle highlights the lower right canine tooth (C), illustrating its role in lateral excursive movements as part of the 'Canine guidance' occlusal scheme mentioned in the text. Canine guidance THE UNIVERSITY OF WESTERN AUSTRALIA Canine guidance: * **A form of mutually protective articulation in** which the vertical and horizontal overlap of canine teeth disengage posterior teeth in excursive movements of the mandible * Widely used and accepted concepted within restorative dentistry * Canine are long and well designed to act as “guiding teeth” * Easy to achieve * Not indicated if canines are endodontically or periodontically compromised   #### Characteristics - A form of mutually protective articulation. - Vertical and horizontal overlap of canines disengages posterior teeth during excursive movements. - Canines are well-designed as "guiding teeth" due to their length and root support. - **Contraindications:** Not indicated if canines are endodontically or periodontally compromised. Annotated diagram of a dental arch (Figure 17-4). The caption explains that 'dots in back signify centric relation contact only' on posterior teeth and 'lines in front signify the role of anterior teeth to disclude posterior teeth'. Red arrows point to specific canine contacts demonstrating the concept of canine guidance. Clinical photograph of a human mandible with upper and lower dentition. A red circle highlights the right maxillary canine, illustrating its anatomical position as a 'guiding tooth' during excursive movements. # Ideal occlusion From "Functional occlusion" textbook **FIGURE 17-1** **Keep this formula in mind as you analyze the anterior guidance: *Dots in back* signify centric relation contact only, on posterior teeth. *Lines in front* signify the role of the anterior teeth to disclude the posterior teeth in all excursions. A principal role of the anterior guidance is to protect the posterior occlusion.**  #### Functional Formula - **Dots in back:** Signify centric relation contact only on posterior teeth. - **Lines in front:** Signify the role of anterior teeth in discluding posterior teeth during excursions. - **Primary Role:** Anterior guidance protects the posterior occlusion. Labeled diagram labeled 'FIGURE 17-1' illustrating ideal occlusion. The image shows a dental arch with teeth marked by red dots and green arrows. The caption explains that 'Dots in back signify centric relation contact only, on posterior teeth' and 'Lines in front signify the role of the anterior teeth to disclude the posterior teeth in all excursions.' # Group function ## Group function: * **Multiple contacts** between the maxillary and mandibular teeth in lateral movements on the working side whereby simultaneous contacts of several teeth **act as a group to distribute occlusal forces.** * Avoids contact on non-working side (non-working interferences are particularly destructive) * Also widely accepted concept * But difficult to establish group function * And may be more destructive/additional load on posterior teeth  #### Characteristics - Multiple contacts between maxillary and mandibular teeth on the working side during lateral movements. - Simultaneous contacts of several teeth act as a group to distribute forces. - **Advantages:** Avoids destructive non-working side interferences. - **Disadvantages:** Difficult to establish; may place additional load on posterior teeth. Anatomical diagram illustrating the concept of 'Group function' in dentistry. It depicts a lateral view of maxillary and mandibular teeth. Red dots are placed at specific points on the posterior teeth to indicate 'Working contacts' as labeled by the legend below. Red arrows point towards these contact areas to demonstrate simultaneous occlusal force distribution during lateral movement on the working side. **Bilateral occlusion** * Bilateral, simultaneous, anterior and posterior occlusal contact of teeth in centric and eccentric positions (At least 3 contact points: 2 posterior and 1 anterior) * Too destructive for natural teeth. But cross arch balanced occlusion can be used in complete denture cases to help stabilize the denture and stop it from flipping over. The University of Western Australia #### Characteristics - Bilateral, simultaneous anterior and posterior contact in both centric and eccentric positions. - Requires at least three contact points (two posterior, one anterior). - **Clinical Use:** Too destructive for natural teeth; primarily used in complete dentures to stabilize the prosthesis and prevent tipping. **Criteria for Ideal Occlusion** **THE UNIVERSITY OF WESTERN AUSTRALIA** **Criteria for Ideal Occlusion** 1) Mandibular stability 2) Axial occlusal load 3) During lateral excursions: no interference in the working side 4) During lateral excursions: disocclusion in the non-working side 5) During protrusion: disocclusion of posterior teeth #### Summary Checklist 1. Mandibular stability. 2. Axial occlusal load. 3. No interference on the working side during lateral excursions. 4. Disocclusion on the non-working side during lateral excursions. 5. Disocclusion of posterior teeth during protrusion. # Interferences Interferences are undesirable occlusal contacts that may produce mandibular deviation during closure to maximal intercuspation or may hinder smooth passage to and from the intercuspal position. There are four types of occlusal interferences. - **Centric** - **Working** - **Non-working** - **Protrusive** Interferences are undesirable contacts that produce mandibular deviation during closure or hinder smooth movement to and from the intercuspal position. #### Types of Interferences - Centric - Working - Non-working - Protrusive Occlusal analysis **THE UNIVERSITY OF WESTERN AUSTRALIA**  Occlusal analysis Clinical occlusal photograph of the maxillary arch (upper teeth) showing the palatal view. Several posterior teeth display multiple blue and red dots on their chewing surfaces, indicating a bite registration or articulating paper analysis to check occlusion. The image is part of a slide titled 'Occlusal analysis'. # Tooth replacement Second lecture of the combined lecture Second lecture of the combined lecture # Importance of Teeth - One of the components of the masticatory system - Teeth are important for acquisition and chewing of food - Loss of masticatory efficiency may impact diet ## Masticatory System Components 1. Teeth 2. Periodontal tissues 3. Articulatory apparatus Interconnected biomechanical system  #### Importance of Teeth - One of the components of the masticatory system - Teeth are important for acquisition and chewing of food - Loss of masticatory efficiency may impact diet #### Masticatory System Components 1. Teeth 2. Periodontal tissues 3. Articulatory apparatus These components form an interconnected biomechanical system. Labeled anatomical diagram of the masticatory system showing a side profile of a human head with highlighted components: CNS (Central Nervous System), Muscles, Articulation, and Teeth. The image illustrates an interconnected biomechanical system as described in the slide context. # Impacts of tooth loss: Diet The University of Western Australia There are inconsistent reports of dietary changes + nutritional deficiencies associated with tooth loss. Theorized that tooth loss reduces masticatory function and chewing ability, which in turn can limit food choices and variety in the diet. For these reasons, dietary intake has been regarded as an intermediate in the pathway between tooth retention and a number of diet-related chronic diseases. <br> ### Comparison of Two Review Articles | Feature | Left Column (Red Highlight) | Right Column (Green Highlight) | | :--- | :--- | :--- | | **Type** | Review Article Abstract | Review Article Conclusion | | **Title** | The nutritional effects of tooth loss$^{1}$ | Does tooth loss affect dietary intake and nutritional status? A systematic review of longitudinal studies | | **Authors** | Catherine A Geissler$^{2}$, BDS, PhD and John F Bates$^{3}$, DDS, Dr Odont | Piyada Gaewkhiew$^{a\;b\;}\;\; \oplus\;,$ Wael Sabbah$^{a}$, Eduardo Bernabé$^{a}$ | | **Abstract Summary** | • 1984 study.<br>• Mixed results: *Reduced* consumption linked to lower Hb and Vit C; *No* striking differences in digestion/nutritional status.<br>• Confounding factors missed. | • Systematic review of longitudinal studies.<br>• **Conclusion:** **No strong evidence** on the effect of tooth loss on diet and *nutrition*, with inconsistent results.<br>• Calls for high-quality longitudinal studies. | | **Key Findings** | $^{1}$Am J Clin Nutr 1984;39:478–489.<br>$^{2}$Tooth loss, mortality, food choice, gastrointestinal irritation, digestion, nutritional status | There is at present no strong evidence on the effect of tooth loss on diet and nutrition, with inconsistent results among the few studies identified. Additional high-quality longitudinal studies should address the limitations of previous studies identified in this review. | There are inconsistent reports of dietary changes and nutritional deficiencies associated with tooth loss. It is theorized that tooth loss reduces masticatory function and chewing ability, which in turn can limit food choices and variety in the diet. For these reasons, dietary intake has been regarded as an intermediate in the pathway between tooth retention and a number of diet-related chronic diseases. #### Comparison of Review Articles **Study 1: The nutritional effects of tooth loss (Geissler & Bates, 1984)** - Mixed results: Reduced consumption linked to lower Hemoglobin and Vitamin C. - No striking differences found in digestion or nutritional status. - Noted that confounding factors were often missed. **Study 2: Systematic review of longitudinal studies (Gaewkhiew et al.)** - Conclusion: There is at present no strong evidence on the effect of tooth loss on diet and nutrition, with inconsistent results among the few studies identified. - Additional high-quality longitudinal studies are required to address previous limitations. Research ARTICLE Open Access **Relationship between tooth loss, low masticatory ability, and nutritional indices in the elderly: a cross-sectional study** Nozomi Okamoto¹*, Nobuko Amano²,³, Tomiyo Nakamura⁴ and Motokazu Yanagi⁵ See the extract on the right for the key descriptions. *Because occlusal contact area is highly correlated with masticatory performance, **the loss of molar teeth would be expected to have a greater impact on measures of performance in that the molar has a larger occlusal contact area**. This effect has been demonstrated in individuals with missing molars who reveal **a greater number of chewing strokes required and a greater mean particle size before swallowing**. The point at which an individual is prepared to swallow the food bolus is another measure of performance and is described as the **swallowing threshold**. Superior masticatory ability that is highly correlated with occlusal contact area also achieves greater food reduction at the swallowing threshold. Conversely, a diminished ability to chew is reflected in **larger particles at the swallowing threshold**.* Conclusions: **A low number of teeth was associated with low masticatory ability in both males and females. Low masticatory ability was associated with low plasma albumin levels and low BMI in females.** Not smoking, maintaining grip strength, preventing cancer, and masticatory ability are important for preventing undernutrition. McCracken’s Removable partial prosthodontics #### Masticatory Performance and Swallowing Because occlusal contact area is highly correlated with masticatory performance, the loss of molar teeth would be expected to have a greater impact on measures of performance in that the molar has a larger occlusal contact area. This effect has been demonstrated in individuals with missing molars who reveal: - A greater number of chewing strokes required. - A greater mean particle size before swallowing. #### Swallowing Threshold The point at which an individual is prepared to swallow the food bolus is described as the swallowing threshold. - Superior masticatory ability (correlated with occlusal contact area) achieves greater food reduction at the swallowing threshold. - Diminished ability to chew is reflected in larger particles at the swallowing threshold. #### Study Conclusions (Okamoto et al.) - A low number of teeth was associated with low masticatory ability in both males and females. - Low masticatory ability was associated with low plasma albumin levels and low BMI in females. - Factors important for preventing undernutrition include not smoking, maintaining grip strength, preventing cancer, and maintaining masticatory ability. <details> <summary>Mastitory Deficiency as a Relevant Factor for Cognitive Functioning</summary> Francesco Bruno Technology, Luanna de Melo Pereira Fernandes, Patricya Assis Tavares Noroña, Alan Antonio Riéti dos Santos, Jerônimo de Castro Leal, Cristiane do Socorro Ferrari, Rafael Rodrigues Lima </details> Impacts of tooth loss: Cognitive ## Cognitive dysfunction - Regular sensory stimulation of mastication is essential for maintaining the learning and memory functions of the aged hippocampus. - The decrease of masticatory stimulation may reduce synaptic density in the cerebral cortex by decreasing sensory input to the cerebral cortex. - **Cerebellar** functions also seem to be influenced by masticatory activity: the increase in cerebellar activity during chewing may improve certain motor functions ## The University of Western Australia ## Tooth loss, chewing efficiency and cognitive impairment in geriatric patients ### Fanny Elsig, Martin Schimmelalela Duvernay, Sandra V. Giannelli, Christoph Graf, Sabrina Carlíer, Ranaid Herrigal, Jean-Pierre Michel, Gabriel Gold, Dina Zekry and Frauke Müller 1Division of Gerontology and Relevant Prosthetics, University of Geneva School of Human Medicine, Geneva, Switzerland; 2Department of Internal Medicine, Rehabilitation and Geriatrics, University Hospitals Geneva, Thônex, Switzerland doi:10.1154/15.12893 ## Tooth loss, chewing efficiency and cognitive impairment in geriatric patients ### Background: Patients with dementia have poorer oral health and fewer teeth than their peers without cognitive impairment. ### Objective: The hypothesis of this study is that the number of natural teeth and the chewing efficiency are associated with cognitive functioning. ### Methods: This cross-sectional study included 28 patients diagnosed with dementia aged 75 years or older and 22 controls who were either cognitively normal (n = 17) or with mild cognitive impairment (n = 3). Nutritional and dental assessments were performed. The chewing efficiency was assessed with a two-colour mixing test. ### Results: Demented patients and controls presented with a mean of 4.9 (+/- 4.2) and 6.5 (+/- 2.5) teeth, respectively (p = 0.553). The number of natural teeth was not associated with dementia (p = 0.553). Same risks were found for age (p = 0.726) and sex (p = 0.901). The chewing efficiency by visual inspection proved worse in participants with dementia than in the controls (p = 0.011) and explained 9.3% of the variance in the diagnosis of dementia. Neither the degree of attrition nor chewing efficiency was related to the nutritional state. ### Conclusion: Chewing functions seem more strongly related to cognitive impairment than the number of teeth. Hence, in a more holistic approach for the geriatric assessment, the dental examination may be complemented by a chewing efficiency test. Keywords: elderly, chewing, dementia, geriatrics, mild cognitive impairment, risk factor. Accepted 14 September 2015 #### Mechanisms of Cognitive Impact - **Hippocampal Function:** Regular sensory stimulation of mastication is essential for maintaining the learning and memory functions of the aged hippocampus. - **Synaptic Density:** A decrease in masticatory stimulation may reduce synaptic density in the cerebral cortex by decreasing sensory input. - **Cerebellar Activity:** Cerebellar functions seem influenced by masticatory activity; increased activity during chewing may improve certain motor functions. #### Study: Tooth loss, chewing efficiency and cognitive impairment in geriatric patients (Elsig et al.) - **Background:** Patients with dementia often have poorer oral health and fewer teeth than peers without cognitive impairment. - **Methods:** Cross-sectional study of patients aged 75+ (28 with dementia, 22 controls). Chewing efficiency was assessed with a two-colour mixing test. - **Results:** - Demented patients (4.9 teeth) and controls (6.5 teeth) showed no statistically significant difference in tooth number (p = 0.553). - Chewing efficiency was significantly worse in participants with dementia (p = 0.011) and explained 9.3% of the variance in dementia diagnosis. - **Conclusion:** Chewing functions seem more strongly related to cognitive impairment than the number of teeth. Dental examinations for geriatric assessment should be complemented by chewing efficiency tests. **Impacts of tooth loss: Cognitive** Good news: partial dentures (or other teeth replacement options may help) **Results:** Compared to non-denture users, dentate participants who used dentures had better baseline cognitive function (β, 1.032; 95% CI, 0.813–1.251; p < 0.001) and a slower annual decline in cognitive function (β, 0.127; 95% CI, 0.047–0.206; p < 0.01). For edentulous participants, denture use was associated with higher baseline cognitive function (β, 3.063; 95% CI, 2.703–3.423; p < 0.001) but not with the rate of cognitive decline (β, 0.011; 95% CI, −0.082 to 0.105; p = 0.818). Results remained consistent across subgroups of dentate participants with various degrees of missing teeth. **Conclusions:** Denture use may help protect against cognitive decline in older adults with partial tooth loss. This study highlights the potential importance of prosthodontic rehabilitation in preserving cognitive health. Further research is needed to establish a causal relationship between denture use and cognitive function. Denture use and a slower rate of cognitive decline among older adults with partial tooth loss in China: A 10-year prospective cohort study Xiang Qi¹ | Zheng Zhu¹,² | Yaolin Pei¹ | Bei Wu¹ THE UNIVERSITY OF WESTERN AUSTRALIA #### Benefits of Prosthetic Rehabilitation Partial dentures or other teeth replacement options may help mitigate cognitive decline. **Study Results (Qi et al., 10-year prospective cohort):** - **Dentate Participants:** Those using dentures had better baseline cognitive function and a slower annual decline in cognitive function (p < 0.01) compared to non-users. - **Edentulous Participants:** Denture use was associated with higher baseline cognitive function but not with the rate of cognitive decline. - **Conclusion:** Denture use may help protect against cognitive decline in older adults with partial tooth loss. This highlights the potential importance of prosthodontic rehabilitation in preserving cognitive health. Impacts of tooth loss: Cognitive However, may be influenced by other confounding variables **Abstract** Dementia is a major contributor to dependence and disability in older people, with aging societies characterized by growing numbers of people living with the condition. Dementia rates are highest in those with low education early in life, midlife hypertension, midlife hearing loss, depression, obesity, loneliness, a sedentary lifestyle, or sustained exposure to smoking or diabetes. Tooth loss is a putative risk factor for dementia which has received increasing research attention, but systematic review findings are mixed. Three main mechanisms have been proposed, involving 1) tooth loss leading to compromised nutrition and then leading to poorer central nervous system (CNS) function; 2) tooth loss resulting in fewer interocclusal contacts and so less somatosensory feedback to the CNS, leading to impaired cognition; and (3) chronic periodontitis resulting in tooth loss, but not before the inflammation has affected the CNS, impairing cognition. None of these is supported by compelling empirical evidence. Here, we use the life course approach to propose a plausible, empirically supported explanation for the associations between missing teeth and poorer cognitive function in older people. Evidence from longstanding cohort studies demonstrates that the putative association arises from cognitive function much earlier in life, in childhood. People with better childhood cognitive function have better oral health and access to routine dental care as they go through life, losing fewer teeth along the life course. They are also much more likely to have better cognitive function in old age. Their less cognitively able childhood counterparts will experience higher disease rates and poorer access to care, resulting in greater incremental tooth loss. Comparison of the 2 groups at any age from the mid-20s on will show greater numbers of missing teeth in the group who were less cognitively able in childhood. Those differences will be most pronounced in old age. **Tooth Loss and Dementia:** **A Critical Examination** W.M. Thomson and Y. Barak #### Confounding Variables and Life Course Approach While tooth loss is a putative risk factor for dementia, systematic review findings are mixed. Three main proposed mechanisms include: 1. Compromised nutrition leading to poorer Central Nervous System (CNS) function. 2. Reduced somatosensory feedback to the CNS due to fewer interocclusal contacts. 3. Chronic periodontitis causing systemic inflammation that affects the CNS. **Critical Examination (Thomson and Barak):** Evidence from cohort studies suggests the association may arise from cognitive function earlier in life (childhood). - Individuals with better childhood cognitive function tend to have better oral health and access to care throughout life, losing fewer teeth. - Those with lower childhood cognitive ability experience higher disease rates and poorer access to care, resulting in greater incremental tooth loss. - The observed correlation in old age may reflect a lifelong trajectory rather than a direct causal link between tooth loss and dementia. <a name="page-1"></a> # Impacts of tooth loss: Anatomical After tooth loss occurs: * The residual ridge no longer benefits from the functional stimulus it once experienced. * Results in a loss of ridge volume—both **height and width** * However, the ridge volume loss is not predictable for all individuals with tooth loss * In general, bone loss is greater in the mandible than in the maxilla and more pronounced posteriorly than anteriorly, and it * Produces a broader mandibular arch while constricting the maxillary arch. (As you have likely learned in complete denture module) **Tooth loss** Loss of quality, width and height of bone  #### Residual Ridge Resorption After tooth loss occurs: - The residual ridge no longer benefits from functional stimulus. - There is a loss of ridge volume in both height and width. - Ridge volume loss is not predictable for all individuals. #### Patterns of Bone Loss - Bone loss is generally greater in the mandible than in the maxilla. - Loss is more pronounced posteriorly than anteriorly. - Resorption produces a broader mandibular arch while constricting the maxillary arch. Anatomical diagram illustrating the progressive effects of tooth loss on alveolar bone. The sequence from left to right shows: (1) a healthy tooth with intact surrounding bone; (2) early stage of bone resorption around the root; (3) further reduction in ridge height and width; (4) more pronounced flattening and volume loss; (5) final stage showing significant atrophy of the residual ridge. Blue arrows indicate the direction of bone loss, and small downward arrows highlight the diminishing ridge height. This visual demonstrates the anatomical changes described in the text—loss of quality, width, and height of bone. Impacts of tooth loss: anatomical Where would you be able to place implants for this patient? The rise and fall of the alveolar process: Dependency of teeth and metabolic aspects **Article** **Full-text available** Sep 2018 Grethe Jonasson , Ingmarie Skoglund , Marianne Rythén  The alveolar process is dependent on the presence of teeth and metabolic aspects. Its "rise and fall" dictates the available bone for future interventions, such as implant placement. Clinical radiograph (panoramic X-ray) of the mandible showing extensive tooth loss and severe alveolar bone resorption. The red circles highlight areas where implant placement is being considered or evaluated based on remaining bone structure. **Reasons for tooth loss** • Congenitally missing teeth • Periodontal disease • Caries • Trauma • Resection due to cancers etc  #### Common Etiologies - Congenitally missing teeth - Periodontal disease - Caries - Trauma - Resection (e.g., due to oral cancers) Clinical intraoral photograph showing anterior teeth with visible spacing (diastema) between central incisors and lateral incisors. The image demonstrates congenitally missing or extracted teeth in the maxillary anterior region, consistent with 'Congenitally missing teeth' listed under Reasons for tooth loss. Tooth replacement **THE UNIVERSITY OF WESTERN AUSTRALIA** ## Prosthesis to replace missing or lost teeth ### DENTURES (RPD) | BRIDGES (FPD) | IMPLANTS --- **Fixed Prosthodontics** Replace coronal portion of teeth and are rigidly fixed to the remaining teeth or implants **Removable Prosthodontics** Replacement of missing teeth and supporting tissues which is designed to be removed by the patient    #### Prosthetic Categories **Fixed Prosthodontics** - Replace the coronal portion of teeth. - Rigidly fixed to remaining teeth or implants. - Examples: Bridges (FPD), Implants. **Removable Prosthodontics** - Replacement of missing teeth and supporting tissues. - Designed to be removed by the patient. - Example: Dentures (RPD). Clinical photo of a fixed partial denture (bridge) in situ. The image shows an upper dental arch with multiple teeth and a prosthetic bridge replacing missing central incisors, rigidly fixed to the remaining natural teeth. Photo of a Removable Partial Denture (RPD). It is a metal framework with acrylic teeth and clasps designed to attach to existing teeth for tooth replacement. Photo of a complete removable denture (full denture). The image displays a pink gum-colored base with artificial teeth, representing the replacement of all supporting tissues and teeth in one jaw. # “Management” of tooth replacement Loss of teeth represent a non-reversible medical condition, and the managing the expectations of the patient may be harder than the “technical skills” we have to learn If patient has never had any replacement options, their experiences are limited to their own natural teeth ```mermaid graph LR A[Fixed \(implants\)] --> B[Fixed \(tooth supported\)] B --> C[Removeable] ``` ```mermaid graph LR A[most “similar” to a “real” tooth] --> B[least “similar” to a “real” tooth] ``` ### Which one is the correct choice?  #### Managing Patient Expectations Loss of teeth represents a non-reversible medical condition. Managing patient expectations is often more challenging than the technical skills required for the procedure. If a patient has never had replacements, their only experience is with natural teeth. #### Hierarchy of Similarity to Natural Teeth 1. **Fixed (Implants):** Most similar to a "real" tooth. 2. **Fixed (Tooth supported):** Intermediate similarity. 3. **Removable:** Least similar to a "real" tooth. A horizontal flowchart-style diagram illustrating a spectrum of tooth replacement options. It shows three stages: 'Fixed (implants)', 'Fixed (tooth supported)', and 'Removeable', connected by blue rightward arrows. Below this sequence is a secondary label indicating that the first option is 'most “similar” to a “real” tooth' and the last is 'least “similar” to a “real” tooth', also linked by a blue arrow, visually demonstrating the trade-off between similarity to natural teeth and removability. # “Management” of tooth replacement Loss of teeth represent a non-reversible medical condition, and the managing the expectations of the patient may be harder than the “technical skills” we have to learn If patient has never had any replacement options, their experiences are limited to their own natural teeth **Fixed (implants)** $\rightarrow$ **Fixed (tooth supported)** $\rightarrow$ **Removeable** most “similar” to a “real” tooth $\rightarrow$ least “similar” to a “real” tooth **Which one is the correct choice?**  Loss of teeth is a non-reversible condition. Managing expectations is a critical component of treatment, as patients often compare prostheses to their natural teeth. **Continuum of Treatment Options:** Fixed (implants) $\rightarrow$ Fixed (tooth supported) $\rightarrow$ Removable This progression moves from the option most similar to a natural tooth to the option least similar. Flowchart diagram illustrating the hierarchy of tooth replacement options. It shows a progression from 'Fixed (implants)' to 'Fixed (tooth supported)' and finally to 'Removeable'. Below these terms are corresponding descriptions indicating similarity to a real tooth: 'most similar' for implants and 'least similar' for removable dentures. Blue arrows indicate the direction of comparison or progression. Shared decision making It’s up to you AND the patient to decide together You need to involve the patient in the shared decision making by providing crucial information outlining the differences: - Technical outcomes - Physical outcomes - Esthetic outcomes - Various maintenance needs - Initial and future costs - Physiologic outcomes that suggest to what extent prostheses *feel* like teeth. Treatment decisions must be made collaboratively between the clinician and the patient. Involve the patient by providing information on the following differences: - **Technical and Physical Outcomes:** Durability and function. - **Esthetic Outcomes:** Visual appearance. - **Maintenance:** Initial and future costs, plus cleaning requirements. - **Physiologic Outcomes:** To what extent the prosthesis "feels" like natural teeth. **Shared decision making** The University of Western Australia **It’s up to you AND the patient to decide together** You need to involve the patient in the shared decision making by providing crucial information outlining the differences: * Technical outcomes * Physical outcomes * Esthetic outcomes * Various maintenance needs * Initial and future costs * Physiologic outcomes that suggest to what extent prostheses “feel” like teeth. Shared decision making involves outlining crucial differences to the patient: - Technical outcomes - Physical outcomes - Esthetic outcomes - Various maintenance needs - Initial and future costs - Physiologic outcomes (proprioception and "feel") Immediate replacement of teeth Immediate replacement of teeth (usually referring to immediate replacement after extraction, although the listed options can also be used as a temporary prosthesis as patient awaits further definitive treatment) **Why is it important?** • Aesthetics (Patients may feel self conscious of missing tooth/teeth) • Maintaining function (such as cases of full clearance) • Preserving soft tissues (we will discuss this further in FPDs) **IF IMMEDIATE TOOTH REPLACEMENT IS REQUIRED, ENSURE YOU MAKE PATIENT AWARE OF ADDITIONAL COSTS (if applicable)**  Immediate replacement usually refers to restoration immediately after extraction, or temporary prostheses used while awaiting definitive treatment. #### Rationale for Immediate Replacement - **Aesthetics:** Preventing self-consciousness regarding missing teeth. - **Function:** Maintaining masticatory ability (especially in full clearance cases). - **Soft Tissue Preservation:** Maintaining architecture (to be discussed further in FPDs). *Note: Ensure patients are aware of any additional costs associated with immediate replacement.* Clinical photo of a patient's open mouth showing the maxillary anterior region. The image displays missing central incisors (likely upper front teeth), revealing the underlying alveolar ridge and soft tissue gap. Adjacent teeth are visible, demonstrating the aesthetic and functional concern addressed in the text regarding immediate replacement. # Immediate replacement The University of Western Australia **Some examples of immediate replacement prosthesis:** **Vacuform stent** Essix retainer + tooth (also known as “suspension bridge”) Immediate FPD (temporary) Immediate denture **Figure 4.** Temporary abutment inserted on the immediate implant. Immediate replacement via implant     #### Examples of Immediate Replacement Prostheses - **Vacuform Stent:** Essix retainer with a tooth (also known as a "suspension bridge"). - **Immediate FPD:** Temporary fixed partial denture. - **Immediate Denture:** Removable option inserted at extraction. - **Immediate Implant:** Placement and temporary abutment/crown at the time of extraction. Clinical photo of a 'Vacuform stent' (Essix retainer + tooth), also known as a 'suspension bridge'. The image shows a transparent plastic dental retainer with an artificial tooth integrated into the occlusal surface. Photo of an 'Immediate FPD (temporary)' prosthesis. The image displays a small temporary dental bridge consisting of two crowns and a pontic on a blue surgical drape. Clinical photo labeled 'Figure 4', showing a 'Temporary abutment inserted on the immediate implant'. The image depicts a patient's upper anterior teeth with a healing cap/abutment placed in the edentulous space. Clinical photo of an 'Immediate denture'. The image shows a full lower denture being held by a retractor, revealing the fit against the gums and underlying remaining natural teeth. **Suspension bridge- example** **THE UNIVERSITY OF WESTERN AUSTRALIA** **DMD patient: A.S.** * **Presenting complaint was missing lower teeth, bleeding gums and “bad breath”** * **Due to timing of picking up patient (August), unable to proceed to “definitive” treatment before the end of the year.** * **Patient offered an essix retainer as a temporary solution**    #### Case Study: Suspension Bridge - **Patient Presentation:** Missing lower teeth, gingival bleeding, and halitosis. - **Clinical Context:** Unable to proceed to definitive treatment before year-end due to timing. - **Solution:** Patient was offered an Essix retainer (suspension bridge) as a temporary solution. Clinical intraoral photograph showing the mandibular arch of a patient with multiple missing lower teeth. The image reveals significant gingival recession and inflammation (bleeding gums) in the edentulous regions, consistent with the 'missing lower teeth' and 'bleeding gums' complaints mentioned in the OCR text. Several remaining teeth exhibit extensive carious lesions and restorations. Clinical intraoral photograph showing the maxillary and mandibular anterior dentition. The upper arch shows yellowish discoloration of the teeth. The lower arch displays an Essix retainer covering the missing anterior teeth, serving as the temporary solution described in the text ('Patient offered an essix retainer'). This visual confirms the presence of the temporary appliance used due to treatment timing constraints. Orthopantomogram (OPG) radiograph displaying the maxillofacial skeletal structures and dentition. It clearly visualizes the extent of tooth loss in the mandibular anterior region, confirming the clinical presentation of missing lower teeth. The radiograph also shows dental restorations and caries on various teeth, providing diagnostic context for the patient's condition. **Suspension bridge** Good option for short term replacement (with only several teeth requiring replacement) Very cheap and quick Patient not able to eat on the prosthesis (not strong) Eg: replacement of missing front tooth whilst awaiting implant healing #### Characteristics of Suspension Bridges - **Indications:** Good for short-term replacement of a few teeth (e.g., front tooth replacement while an implant heals). - **Advantages:** Very inexpensive and quick to fabricate. - **Disadvantages:** Not strong; the patient cannot eat on the prosthesis. <img>Immediate (temporary bridge) dental prosthesis - top left shows palate socket, top right shows the bridge on blue pad, bottom left shows two red arrow marks on gums, bottom right shows bridge on live patient We will talk more about this in our FPD module. Just be aware this exists. It is a relatively uncommon immediate prosthesis.     Immediate temporary bridges are a relatively uncommon form of immediate prosthesis. They serve as a fixed interim solution during the healing phase. Clinical intraoral photo of a maxillary arch showing an edentulous ridge with a socket (indicated by red arrow) and adjacent teeth. Photo of a temporary dental bridge on a blue textured pad, featuring a red arrow pointing to the pontic area. Intraoral view of gums with two red arrows indicating specific areas or soft tissue conditions in the anterior region. Clinical photo showing the immediate temporary bridge seated on a patient's upper jaw. # Immediate denture * RPD vs complete denture * Denture inserted at date of extraction * Requires pre-planning of denture, with accommodations for potential tissue inflammation during healing * Easy to maintain and modify (eg relines) * Dependance on the skill of technicians * Not able to do a real “try-in” with the patient. Fit is unpredictable * Lab is estimating what the extraction site looks like * Requires good communication with patient (you need to tell them what to expect, and set the bar low low) * Significant chairside time (adjustments) This lecture is not going to be able to cover all aspects of immediate dentures, there’s simply too much to discuss. I can organize another lecture on this if you want. It might also be covered in the RPD module? #### Clinical Considerations - Can be a Removable Partial Denture (RPD) or a Complete Denture. - Inserted on the same day as extractions. - Requires pre-planning and accommodations for tissue inflammation during healing. #### Advantages and Challenges - **Maintenance:** Easy to modify with relines. - **Technical Limitations:** Fit is unpredictable as there is no "try-in" phase; the lab estimates the extraction site contour. - **Patient Management:** Requires setting realistic (low) expectations. - **Clinical Time:** Significant chairside time is required for adjustments. # Immediate denture * RPD vs complete denture * Denture inserted at date of extraction * Requires pre-planning of denture, with accommodations for potential tissue inflammation during healing * **Easy to maintain and modify (eg relines)** * **Dependance on the skill of technicians** * Not able to do a real “try-in” with the patient. Fit is unpredictable * Lab is estimating what the extraction site looks like * Requires good communication with patient (you need to tell them what to expect, and set the bar low low) * **Significant chairside time (adjustments)** This lecture is not going to be able to cover all aspects of immediate dentures, there’s simply too much to discuss. I can organize another lecture on this if you want. It might also be covered in the RPD module? #### Key Features of Immediate Dentures - Inserted at the date of extraction. - Requires pre-planning for tissue changes. - **Modification:** Easy to maintain and modify via relines. - **Technician Dependence:** Fit is unpredictable because a real "try-in" is impossible. - **Chairside Time:** Requires significant time for adjustments post-insertion. # **Immediate denture** *(Top right logo:)* **THE UNIVERSITY OF WESTERN AUSTRALIA** - At treatment planning stage, go over all options with the patient - This includes the option of immediate denture (if applicable) - Explain the benefits and the disadvantages to patient and let them participate in the decision **Option 1: Immediate denture** - Immediate replacement of teeth (patient won’t have to walk around no teeth, which some people will really care about) - The immediate denture will NOT fit well - Further steps required after the immediate denture completed (either relined, or a new separate denture made) **Option 2: Denture fabrication after healing** - Delayed replacement of teeth, may be non-aesthetic - Potentially cheaper cost of treatment (relines not required shortly after insert) #### Treatment Planning Options **Option 1: Immediate Denture** - **Benefit:** Immediate replacement; no period without teeth. - **Drawback:** The denture will not fit well initially. - **Follow-up:** Requires subsequent relines or the fabrication of a new definitive denture. **Option 2: Denture Fabrication After Healing** - **Benefit:** Potentially lower cost (no immediate relines needed). - **Drawback:** Delayed replacement; patient remains edentulous during healing (non-aesthetic). # Immediate denture This case is taken from a published article: **Prosthodontic Rehabilitation and Follow-Up Using Maxillary Complete Conventional Immediate Denture** Conson Yeung, Katherine Chiu Man Leung, Ollie Yiru Yu, Walter Yu Hang Lam, Amy Wai Yee Wong & Chun Hung Chu     #### Case Study: Maxillary Complete Conventional Immediate Denture Reference: Prosthodontic Rehabilitation and Follow-Up (Yeung et al.). Clinical photo showing the maxillary arch of a patient's mouth. The image displays multiple teeth with significant caries (dark brown/black decay) and restorations. A central anterior tooth appears to be an artificial crown or bridge abutment. This visual demonstrates the pre-operative condition requiring prosthodontic rehabilitation. Clinical photo of the anterior view of the patient's mouth, focusing on the upper dentition. Several teeth show extensive decay and existing fillings. The central incisors appear restored or replaced, consistent with the 'Immediate denture' context mentioned in the slide title. Panoramic dental radiograph (OPG) of the maxilla and mandible. The image reveals the skeletal structure, remaining natural teeth, and areas of edentulism. It provides diagnostic information regarding bone levels and root integrity for the planned immediate denture case. Clinical photo of the mandibular arch of the patient's mouth. The lower teeth exhibit varying degrees of wear, discoloration, and caries. This image documents the contralateral arch condition alongside the primary focus on the maxilla. - Immediate denture - After discussion with patient, all parties agreed to full clearance of maxillary teeth and immediate denture. (Mandibular teeth restored and RPD made) Figure 8 Maxillary irreversible hydrocolloid impression. Figure 10 Maxillary occlusal rim. Figure 12 The wax-up denture try-in. Figure 13 The trimmed maxillary cast.     #### Clinical Workflow 1. Discussion and agreement on full maxillary clearance and immediate denture. 2. Maxillary irreversible hydrocolloid impression. 3. Fabrication of maxillary occlusal rim. 4. Wax-up denture try-in (for aesthetics/records). 5. Trimming of the maxillary cast to simulate extractions. Clinical photo of a dental cast showing the maxillary arch with a perforated base. Red annotations highlight the structure. Close-up clinical photo labeled 'Figure 10 Maxillary occlusal rim'. Shows a pink wax rim on a cast with white self-cured acrylic material applied to the anterior region. Red arrows point to specific areas of interest. Intraoral clinical photo labeled 'Figure 12 The wax-up denture try-in.' Shows a patient's mouth with teeth and gums, demonstrating the fit of a waxed denture. Red arrows indicate specific tooth positions or contact points. Clinical photo labeled 'Figure 13 The trimmed maxillary cast.' Shows a beige-colored dental cast representing the upper jaw. Red lines and arrows trace the contour and trimming area of the cast. # Immediate denture Special instructions: **Denture to be kept in for 24hr (or overnight) if possible. Swelling may occur.**   #### Post-Extraction Instructions - The denture should be kept in the mouth for the first 24 hours (or overnight) if possible. - This helps manage initial swelling. Figure 14: Clinical photo showing the maxillary alveolar ridge immediately after extraction. The area is sutured with black sutures to assist haemostasis. A red arrow points to a specific site on the gum line. Figure 16: Clinical photo of a patient wearing an upper immediate denture in situ. The denture covers the extraction sites, and a clear cheek retractor is visible. A red arrow indicates the midline of the palate. # Immediate denture: relines * Direct relines may be required until healing complete (~3 months for bone remodeling) * Indirect reline once healing complete. * Denture roughened * Relining material mixed, applied to area of denture * Denture inserted, patient to bite down in MIP * Border molding completed * After material is set, excess material removed (eg scalpel) #### Reline Protocols - **Direct Relines:** Required periodically until healing is complete (approx. 3 months for bone remodeling). - **Indirect Reline:** Performed once healing is finalized. #### Procedure for Relining 1. Roughen the denture surface. 2. Mix and apply relining material to the tissue surface of the denture. 3. Insert denture; patient bites down in Maximum Intercuspation (MIP). 4. Perform border molding. 5. Remove excess material after the set. Product photograph of a 'SOFT-LINER' immediate denture reline material kit. The image displays the packaging box alongside component bottles (liquid and powder), measuring cups, and application tools, visually supporting the OCR text describing the relining procedure steps. # Immediate replacement: Implants  ## Immediate Restoration of Single implants Placed Immediately After tooth Extraction  ## **Figure 1.** *Clinical view of the compromised left central incisor.*  ## **Figure 2.** *Periapical radiograph of the compromised incisor.* [Speaker icon](img) Antonio Barone,* Lorena Rispoli,† Iole VoZZa,‡ Alessandro Quaranta,† and Ugo Covanisis   #### Immediate Restoration of Single Implants This involves placing an implant immediately after tooth extraction. Clinical assessment includes evaluating the compromised tooth (e.g., left central incisor) via visual inspection and periapical radiographs before proceeding with extraction and immediate placement. Clinical photograph showing the anterior maxillary teeth. The image focuses on a compromised left central incisor which appears discolored and has gingival recession compared to adjacent healthy teeth. Periapical radiograph of the compromised incisor showing a dental implant placed in the socket (indicated by a red arrow). The root canal filling is visible within the tooth structure. **Immediate replacement: Implants** Figure 3. Fresh extraction site and immediate implant placement. Figure 4. Temporary abutment inserted on the immediate implant. Figure 5. Temporary crown in place at the time of implant insertion. Figure 6. Soft tissue healing 6 months after implant placement and temporary restoration.     #### Clinical Stages of Immediate Implants 1. Fresh extraction site preparation. 2. Immediate implant placement. 3. Insertion of a temporary abutment. 4. Placement of a temporary crown at the time of insertion. 5. Evaluation of soft tissue healing (typically reviewed at 6 months post-placement). Clinical photo showing a fresh extraction site with an implant placed. Yellow arrows point to the implant and surrounding tissue. Caption: 'Figure 3. Fresh extraction site and immediate implant placement.' Clinical photo showing a temporary abutment inserted on the immediate implant in the lower jaw. Red arrow points to the abutment. Caption: 'Figure 4. Temporary abutment inserted on the immediate implant.' Clinical photo showing a temporary crown in place at the time of implant insertion. Red arrow points to the crown. Caption: 'Figure 5. Temporary crown in place at the time of implant insertion.' Clinical photo showing soft tissue healing 6 months after implant placement and temporary restoration. Red arrow points to the healed gingiva around the crown. Caption: 'Figure 6. Soft tissue healing 6 months after implant placement and temporary restoration.' # **Thanks for listening!** > THE UNIVERSITY OF # **WESTERN AUSTRALIA** ## Any questions? 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