L2 Radiography in Periodontology

Radiography In Periodontology¹

DR ANNA HUGHES / Dr Rincon / Prof Abbott

Introduction And Clinical Objectives²

AIM OF THE LECTURE

• To understand the diagnostic benefit and biological cost of radiographic imaging
• To understand the prerequisites for prescribing a radiological test
• Discuss the imaging modalities used in periodontology
• Interpreting radiographs for periodontal diagnosis

Principles Of Radiographic Imaging

Benefits And Limitations³⁴

BENEFITS OF RADIOLOGY IN PERIODONTOLOGY

• Evaluation of health and pathology of hard tissues - teeth and surrounding bone.
• Essential aid in diagnosis in addition to the clinical periodontal assessment.
• Important in determining prognosis.
• Facilitates treatment planning.
• Important to exclude non-inflammatory conditions.
• Prerequisite for pre-surgical planning.
• Assists in monitoring treatment outcomes.

LIMITATIONS OF RADIOLOGICAL IMAGING

• Ionizing radiation mostly only reveals alteration in calcified tissues.
• It doesn’t reveal cellular (disease) activity.
• Shows only historical bone destruction.
• Limited value in soft tissue analysis.
• After regenerative procedures, difficult to distinguish between bone graft and regenerated bone.

Biological Costs And Radiation Effects⁵

BIOLOGICAL COSTS and the effects of ionizing radiation

Ionizing radiation can induce cellular and chromosomal damage in 2 main ways:

• Deterministic effect – dose has to be over a certain threshold to cause damage, severity then increases with dose – fetal abnormality, skin damage, hair loss.
• Stochastic effect – not dose dependent but risk increases with higher dose – induction of chromosomal damage which can develop into specific cancers, leukemias, salivary gland, thyroid, breast, brain. Can occur years after radiation.
• Radiation dose protection principles very important – justification, optimization (Alara), dose limitation.

Prerequisites For Radiographic Prescription⁶

PREREQUISITES

• Sound knowledge of anatomy and radiological anatomy in the field of view of your radiograph.
• Knowledge of the disease conditions you are looking for and its radiographic presentation.
• The principle of Alara (as low as reasonably achievable) and pros and cons of each imaging modality.
• Training in taking a good radiograph.

Imaging Modalities And Techniques

Overview Of Modalities⁷⁸

• Ionizing radiation – intra/extraoral sensors

• Bitewings, periapicals, occlusal

• Panoramic, cephalometric views

• 3D imaging – cone beam computed tomography

• Multislice / multidetector computed tomography

• Non-ionizing radiation

• Ultrasound

• MRI

• Bone destruction, bone loss pattern and bone defect morphology.

• Roots – anatomy, length, crown/root ratio, hypercementosis

• Restorations – deficiencies, caries, overhangs

• Calculus if abundant

• Pulp/periapical conditions, perio-endo conditions

• Furcations

• Periodontal ligament space

• Tooth impactions, root remnants, unerupted teeth

• Any pathology of the root or adjacent structures

• Bone deficiencies

Intraoral Radiography⁹¹⁰

• Standard imaging modality for periodontal evaluation, mostly diagnostic of interdental bone changes
• Periapical and bitewings use various sized films / digital sensors intraorally attached to a localising ring.
• Not as accurate as 3D imaging but much lower radiation dose.
• Ideally aim to standardize technique – exposure time, film size, angulation

Periapical And Bitewing Views¹¹¹²¹³

• Various sized small digital sensors positioned ideally parallel to the tooth being examined – ideal for viewing the whole root, used for evaluating periapical and periodontal/peri-implant status – even with holders you can over- or underestimate calculations

Used for caries detection and early crestal bone loss

More accurate than PAs because x-ray projection more perpendicular to teeth but records only coronal third of tooth

Ideally no overlap of teeth, cusp tips clear

• How do you know it’s a good intraoral radiograph?
  • Clear cusps of molars
  • Enamel and pulp chambers seen and distinct.
  • Interproximal spaces should be open.
  • Interproximal contacts should not overlap (unless crowding present)

Limitations And Distortions¹⁴¹⁵

• Superimposition
• Buccal/lingual bone and roots

Effect of varying the angulation

Vertical and horizontal shifting of the x-ray tube will change the configuration of the PDL space, furcation, interdental bone, position of roots

An endodontic infection? Or a severe periodontal infection?

• Or a root perforation?

Radiographic Techniques And Tube Shifts¹⁶

Distortions – by vertical/horizontal shifting

Bisection technique:

• Increases projection
• Bone closer to crown
• Distortion of facial and lingual bone
• Long cone technique better

Mesial or distal shifting:

• Changes the shape of interdental bone
• Changes PDL space width
• Changes lamina dura
• Furcation involvement changes

Long cone parallel technique

Vertical Shift

• Increased angle
• Decreased angle

Horizontal shifts

• Mesial

• Distal

• Used to separate objects that are otherwise superimposed over each other

• Can help to indicate the “3rd dimension”

Extraoral And 3D Imaging

Panoramic And Cephalometric Radiology^1718192021

• Extraoral rotating x-ray source and image receptor moves around the patient’s head – produces a curved image of patient’s jaws, teeth, TMJ.
• Useful as a screening tool, especially if intraoral views not possible/uncomfortable.
• Problems – image magnification, ghost and double images, distortion, superimposition, low resolution
• Lower radiation dose compared to full mouth periapical radiographs

Variations in panoramic machines – magnifications are uneven and unpredictable

Image distortions, variable shortening and elongations, lingual objects more superior

Occlusal radiographs – used in perio to locate impacted / unerupted teeth (also in dental trauma, locate bone lesions, fractures)

• More useful in orthodontic therapy and orthognathic surgery
• Occasionally used in perio for full arch implant rehabilitation

1. Superimposition of structures
2. Geometric alteration
   • Elongation & foreshortening, even with holders
3. Anatomic obstacles
   • Unable to show complex root morphology

Cone Beam And Multidetector Computed Tomography^22232425

• Introduced into the dental field in 1998, rapidly growing in popularity.
• Uses a cone beam to capture image in one rotation around a patient – less radiation compared to MDCT
• Spatial resolution lower than 2D images but higher by 2-8 times than a MDCT.
• Radiation dose higher than an OPG by 5-10 times (machines in envision)
• But low contrast resolution (poor for soft tissues and low density structures) – big problems with movement and metallic artifacts.

Already commonly used in medicine – fan beam x-rays to take axial slices from top to bottom.

Superior soft tissue contrast compared with cone beam.

Less accessible for dentists, high cost and radiation dose (up to 15 times more than a CBCT)

• To determine the extent and pattern of periodontal bone loss, including infrabony defects, dehiscences, fenestrations

• Furcation morphology – i.e. width of entrance, pattern of bone loss in furcations

• Root morphology

• Root fractures

• Periapical status

• Origin of infection

• Pre-surgical / implant planning

• Pre-ortho in thin phenotypes / perio patients

• BUT INTRAOPERATIVE ANALYSIS MOST ACCURATE

• Software available to manipulate the axial images into other planes and views (sagittal, coronal…) – MPR or multiplanar reformation

• Software can be used to plan and form an implant surgical guide pre-op along with computer assisted treatment planning

• CBCT not useful to monitor peri-implant bone loss (metallic artifacts) – OPG and periapicals better for interproximal bone evaluation

Comparative Radiation Doses²⁶

• IO PA / BW = 2 uSv
• OPG = 20 uSv
• CBCT = 40-80 uSv
• Chest x-ray = 14 uSv
• Background radiation in the UK = 7 uSv/daily
• Flight – UK to US = 80 uSv

Non Ionizing Radiation Modalities²⁷²⁸²⁹

• Radiofrequency pulse used in a chamber with a static magnetic field

• Excellent for TMJ and soft tissue analysis

• However expensive, claustrophobic, severely affected by metal artifacts

• Increasing interest in developing its use for perio because of ability to differentiate between healthy and inflamed soft tissue

• Uses sound waves and a transducer to generate an image.

• Large transducer head limits current application to TMJ, salivary glands, lymph nodes, head and neck muscles, thyroid gland, carotid vessels

• Smaller transducers more useful intraorally and currently being developed – useful for teeth and implant soft tissue measurements.

• Not affected by metal artifacts so useful for peri-implant evaluation.

• Useful for cosmetic injectables (fillers) to avoid vascular occlusion and evaluate longevity and migration of fillers.

FILLER COMPLICATIONS – VASCULAR OCCLUSION AND TISSUE NECROSIS

Radiographic Interpretation And Diagnosis

Normal Radiographic Features³⁰³¹

Normal Radiographical Features on a 2D Image (PA and BWS)

• Interdental bone/septa width varies between different teeth, but should be radiopaque and smooth and horizontal.
• Alveolar crest 0.5 to 2 mm to CEJ.
• Lamina dura – dense cortical bone – appears as a white line, which may or not be continuous.
• Periodontal ligament space may be widened if the teeth are mobile.
• Buccal/lingual bone not possible to examine on 2D imaging – buccal bone deficiencies may be present in health (dehiscences/fenestrations).
• If teeth have supraerupted, distance between CEJ and crestal bone is more.

Assessment Of Bone Destruction³²

Interpreting bone destruction in periodontal disease

Periodontal bone loss starts at the alveolar crest.

Initial phase, reduced density of cortical bone.

Slight radiographic changes in bone height means progression to early stages of periodontitis.

• Hence the earliest signs are easier to detect clinically by probing.
• X-ray underestimates bone loss compared with clinical assessment.
• Average distance from CEJ to interproximal alveolar crest is 1.5 to 2 mm hence bone loss is determined by measuring the distance from the crest to the CEJ.

Severity And Classification Stages^333435363738

Severity and the Classification Stages

• Mild - stage I (less than 15%)
• Moderate - stage II (15-33%)
• Stage III and Stage IV (extends to mid 1/3 and beyond)
• Advanced bone loss - stage III - IV
• % of bone loss and root length

Severity and the Radiographic Report in Your Perio Eform

• Mild - less than 33% bone loss
• Moderate – between 33 and 66%
• Severe - more than 66%
• Pattern - horizontal / vertical
• Distribution - localized or generalized.

Stage 2 Periodontal Disease (mandibular + maxillary left posterior) bitewing radiograph: Radiographic bone loss limited to the coronal third (15%-33%). Image provided by authors.

Peri Implant Conditions^39404142

Normal implant bone levels

Fig. 23 Mucositis (maxillary anterior incisor) periapical radiograph: Alveolar crest levels appear radiopaque. Bone level appears normal at level of implant platform. Image provided by authors.

Peri-implantitis

Fig. 29. Peri-implantitis, Lack of Keratinized Tissue Etiology (mandibular right premolar) periapical radiograph: Alveolar crest levels appear diffuse. Horizontal bone loss pattern noted. Image provided by authors.

Fig. 27. Peri-implantitis, Bacterial Etiology (maxillary anterior incisor) periapical radiograph: Alveolar crest levels appear radiopaque. Severely reduced abrupt vertical bone loss noted at mesial and distal aspect of implant housing. Image provided by authors.

Occlusal trauma - widened PDL space, thickened lamina dura

STAGE	CAL PERSPECTIVE	POCKET PERSPECTIVE	BONE LOSS PERSPECTIVE
Stage I	CAL 1-2 mm	4 mm POCKET	1-15%
Stage II	CAL 3-4 mm	5 mm POCKET	15-33%
Stages III & IV	CAL 5 mm +	6 mm + POCKET	33 to 100%

Copyright © 2008 Wolters Kluwer Health | Lippincott Williams & Wilkins

Morphology And Pattern Of Bone Loss⁴³⁴⁴

Radiographic Interpretation - Morphology of Bone Loss

• Bone loss type
• Horizontal bone loss
• Vertical bone loss

Assessing bone loss more difficult on 2D images.

Intrabony And Crater Defects^4546474849

Vertical/angular/intrabony/infrabony/crater bone defects - different types

Pattern of Intrabony Defects; 1, 2, 3 Walled Defects

Number of Remaining Walls

Crater Defects

Buccal and lingual plate higher than the base of a defect - difficult to detect on 2D imaging - may appear as more radiolucent except if B/L bone very thick.

Images of teeth showing crater defects, one intraoperative and one on a dental model.

Radiopaque Horizontal Line for Labial or Lingual Bone Level

Distribution

• Localised less than 30%
• Generalised more than 30%

Furcation Involvement⁵⁰⁵¹⁵²

Furcation Defects

• In multirooted teeth, hard to see bone loss in furcations on 2D images because of superimpositioning of bone and roots.
• Variations in radiolucency may help detect bone loss.
• Inverted J shape on maxillary molars - sign of distal furcation bone loss.
• Unless the radiograph is standardised and reproducible, very hard to compare before and after treatment/deterioration.
• CBCT more accurate as a diagnostic tool but not recommended for follow-up and monitoring.

Interpretation of Furcation Defects in 2D Imaging

Fig. 23-18 Various stages of furcation involvement as depicted on periapical images. (a) The radiograph shows a slight radiolucency in the most coronal aspect of the furcation of tooth 46. (b) This periapical radiograph shows radiolucency in the furcation of tooth 36 that reaches the middle-third of the root. Different crestal bone levels may mimic no radiolucency in the furcation of tooth 37. (c) This radiograph exhibits a radiolucency of the furcation of tooth 26 that extends up to the apex of the respective roots.

Fig. 23-19 A periapical image demonstrating a radiolucent triangle superimposed over the distal roots of tooth 26 and demonstrating the hooks of the “J” shaped radiolucency on the distal root of tooth 27, both of which indicate bone destruction extending into the furcation of the respective regions (yellow circles).

Fig. 23-20 This periapical image shows an extended radiolucency from the alveolar crest to the periapical region of tooth 46. This points towards the presence of periodontal and periapical inflammatory pathologies (perio-endo lesion).

Periodontitis Radiographic Appearance

• Depends on radiographic technique, tube angulation and film placement.
• Also depends on anatomical variations thickness and density of interdental bone, position of teeth.
• Presence of an intact lamina dura indicates health but its absence doesn’t mean disease.
• Furcations may appear as a wedge shaped radiolucent area mesial and or distal with apex pointing to the crown.

Systemic Manifestations And Healing⁵³⁵⁴⁵⁵

Healing After Treatment

Some Systemic conditions can present with periodontal manifestations radiographically

• OSTEITIS FIBROSA
• PAGET’S DISEASE
• FIBROUS DYSPLASIA
• HISTIOCYTOSIS
• OSTEOPETROSIS
• SCLERODERMA
• MALIGNANCY
• CARCINOMA OF THE JAW
• OSTEOSARCOMA

Distribution

Clinical Recommendations And Conclusion

Recommendations for Periodontal disease assessment⁵⁶

• OPG is sufficient for an overview – occasionally and alternatively full-mouth periapicals can be used.
• Additional intraoral views can be used for more detail on bone levels and root morphology – however limited detail on furcation and intrabony defects.
• CBCT/MDCT provides a lot more detail if accuracy is important in evaluation of prognosis and treatment planning – but not recommended for follow-up examinations.

When is volumetric analysis useful in perio⁵⁷

• To determine the extent and pattern of periodontal bone loss, including infrabony defects, dehiscences, fenestrations
• Furcation morphology i.e. width of entrance, pattern of bone loss in furcations
• Root morphology
• Root fractures
• Periapical status
• Origin of infection
• Pre-surgical / implant planning
• Pre-ortho in thin phenotypes / perio patients

To conclude⁵⁸

• Justification – Prescribe radiological exam only if clinical exam does not provide sufficient diagnostic information
• Optimization – Follow the lowest dose protocol to achieve the diagnosis

Keep updated in theories and techniques of radiological assessment.

References⁵⁹

• THANK YOU!

RECOMMENDED READING

Lindhe’s Clinical Periodontology and Implant Dentistry 7th edition Chapter 23.

Periodontal and Implant Radiology

Joseph P. Fiorellini, DMD, DMSc^a,^b^*, Dennis Sourvanos, BBDH, DDS^a,^b, Hector Sarimento, DMD, MSOB^a,^b, Nadeem Karimbux, DMD, MMSc^a,^b, Kevin W. Luan, BDS, MSOB, MEd^a,^b^c^

Dent Clin N Am 65 (2021) 447–473

https://doi.org/10.1016/j.cden.2021.02.003

0011-8532/21/© 2021 Elsevier Inc. All rights reserved.

Footnotes

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