Possible Short answers

Retraction cord (mechanical displacement packed into the sulcus).
Astringent / hemostatic agent — e.g. Traxodent / aluminium chloride.
Expasyl (combined chemical + mechanical, aluminium chloride with kaolin).
Electrosurgery (surgical widening).
Laser (surgical widening).

📌 Name the clinical procedures of FDP / List ALL the steps of the systematic try-in procedure. (Very high yield)

The try-in follows a 3-stage systematic approach:

Evaluation of the restoration on the die (ideally done 1–2 working days before the appointment to allow lab corrections without wasting chair time):
1. Die and opposing model
2. Internal surface of the restoration
3. Restoration on the model (die) — external surface and occlusion on articulator
Seating the crown on the prepared tooth:
1. Proximal contact
2. Internal fit
3. Marginal fit
Assessment of the seated crown:
1. Stability
2. Contour
3. Occlusion
4. Aesthetics

The final goal of all stages is to confirm the restoration is suitable for permanent cementation.

L1 — Fixed Dental Prosthesis Components

List the four core components of a fixed dental prosthesis (FPD) and briefly state the function of each.

Abutments — the supporting natural teeth.
Retainers — the crowns placed over the abutment teeth.
Pontics — the artificial teeth replacing the missing natural teeth.
Connectors — the elements joining pontics to retainers, creating a single rigid unit.

An FPD functions like a structural bridge, requiring support at both ends (except cantilever designs).

List the biological requirements of an abutment tooth preparation.

Conservation of tooth structure
Avoidance of overcontouring
Supragingival margins
Harmonious occlusion
Protection against tooth fracture
A common path of insertion shared by all abutments (achieved by visually averaging the long axes of all abutments during preparation)

State the mechanical and aesthetic requirements of an abutment tooth preparation.

Mechanical requirements:

Retention form
Resistance form
Deformation resistance

Aesthetic requirements:

Minimum display of metal
Maximum thickness of porcelain
Porcelain occlusal surfaces
Subgingival margins

What is meant by a “common path of insertion,” and why is it required for bridge abutments?

A common path of insertion is a shared direction of seating that all abutments must permit so the rigid prosthesis can be fully seated.
It is required because the bridge is a single rigid unit — if abutments diverge, the prosthesis cannot seat.
Achieved by visually averaging the long axes of all abutments during tooth preparation.

Describe the difference between full-coverage and partial-coverage retainers, giving examples.

Full-coverage restoration: All-metal, PFM (porcelain-fused-to-metal), or all-ceramic crowns.
Partial-coverage restoration: 4/5 or 7/8 crowns.

What is a pontic, and what functions does it serve?

An artificial tooth that replaces a missing natural tooth; it is suspended and tooth-supported.
Restores aesthetics and function.
Prevents tilting and drifting of adjacent teeth and super-eruption of opposing teeth.

List the design parameters that must be considered when designing a pontic.

Height and width of the residual ridge.
Dimensions of the edentate space.
Shape and texture of the soft tissues.
Comfort and support of the adjacent tissues.
Aesthetic requirements.
Ridge form — ideal ridges are smooth and regular with attached gingiva; horizontal or vertical defects may require surgical modification.

Classify the pontic designs according to mucosal contact.

Mucosal contact
- Ridge-lap (saddle)
- Modified ridge-lap
- Ovate
- Conical
No mucosal contact
- Sanitary (hygienic)
- Modified sanitary (hygienic)

Why is the saddle (full ridge-lap) pontic contraindicated under all circumstances?

It has a concave tissue surface and overlaps the residual ridge bucco-lingually.
It is contraindicated under all circumstances because the tissue surface is inaccessible to cleaning devices, leading to plaque accumulation and tissue inflammation.

Describe the modified ridge-lap pontic and its indications.

Lingual modification opens the cervical embrasures to facilitate hygiene.
Gentle concavity linguo-facially but always convex mesio-distally.
Ideally suited to a convex gingival profile with no concavities.
High aesthetic value — a primary aesthetic pontic design.

Describe the ovate (spheroidal) pontic, including its advantages and a key limitation.

Best aesthetics — appears to emerge/“grow” out of the ridge.
Convex tissue surface in both bucco-lingual and mesio-distal directions.
Relatively easy hygiene despite a large tissue-contact area.
A strong pontic design (supported ceramic) — eliminates unsupported porcelain in the cervical portion of an anterior pontic.
Limitation: may need surgical augmentation (costly).
Tip: after atraumatic extraction, a provisional ovate pontic encourages gingiva to heal into a concave, scalloped shape, preserving the interdental papillae.

Compare the conical and sanitary (hygienic) pontic designs and state where each is used.

Conical:

Bullet-/egg-shaped; convex with only one point of contact with the residual ridge.
Used in the posterior region.
Not suitable for broad residual ridges (food trapping).

Sanitary (hygienic):

Sits 2–3 mm clear off the ridge (no mucosal contact); easy to clean.
Used in posterior regions.
Not recommended / rarely used today — traps food, irritates the tongue, poor aesthetics, sharp line angles.

List the biologic, mechanical, and esthetic goals of an optimal pontic design.

Biologic:

Cleansable tissue surface
Access to abutment teeth
No pressure on the ridge

Mechanical:

Rigid (to resist deformation)
Strong connectors (to prevent fracture)
Metal-ceramic framework (to resist porcelain fracture)

Esthetic:

Shaped to look like the tooth it replaces
Appears to “grow” out of the edentulous ridge
Sufficient space for porcelain — maximum veneering porcelain thickness ≈ 1.2 mm, with framework support to prevent bulk fracture.

Describe the types of connectors and explain the Law of Beams as it applies to connector design.

Types of connectors:

Rigid: cast or soldered.
Non-rigid.

Law of Beams (deflection creates tensile stresses that fracture connectors):

Height (depth): doubling the height reduces deflection to one-eighth (inverse-cube relationship) — height is the most critical dimension.
Span length: doubling the span increases deflection eightfold.

When are non-rigid connectors indicated?

When a common path of placement/insertion is impossible.
To accommodate mandibular flexure.
They act as stress breakers.
(Also useful as a solution for an extremely tilted abutment tooth.)

Explain the biomechanics of a cantilever FPD and why a single-abutment cantilever is mechanically disadvantageous.

Forces on a cantilever are resisted on only one side, creating imbalance.
Vertical forces cause tipping; horizontal forces cause rotation of the abutment.
Including both adjacent teeth resists forces far better, because the teeth must be moved bodily rather than merely tipped or rotated.
The periodontal ligament poorly resists tipping/rotational forces compared to axial forces.
“To be successful, single-abutment cantilevers require a very favourable occlusion.”

State the advantages, disadvantages, and favourable applications of a cantilever FPD.

Advantages:

Easier preparation (no strict common path of insertion on both sides).
More conservative — preserves tooth structure (e.g., avoids preparing a canine to replace a lateral incisor).

Disadvantages:

Induces lateral and rotational forces on the single abutment.
PDL poorly resists these non-axial forces.

Favourable applications:

Cantilevering a lateral incisor from a maxillary canine (with good bone support).
Cantilever implant-supported prostheses.
Prefer anterior placement (lower occlusal load) or in an open bite; distal cantilevers in the posterior should generally be avoided.

List the indications for a fixed partial denture (FPD).

Patient unable/unwilling to accept removable options.
Orthodontic reasons (e.g., replacing missing lateral incisors).
When adjacent teeth would also benefit from indirect restorations.
Patient not suited for implants (e.g., insufficient bone height/dimensions, or limited space — implants need ≥2 mm bone between implant and adjacent teeth).
Young patients with congenitally missing teeth where implants are contraindicated by continued jaw growth (wait until ≥18 years).
Resin-bonded bridges as a conservative temporary option when canine substitution is unsuitable.

List the contraindications and cautions for a fixed partial denture.

Poor periodontal status of abutments (crown–root ratio, Ante’s law).
Absence of a distal abutment in posterior sections.
Long-span bridges.
Poor oral hygiene.
Extremely tilted teeth (careful assessment rather than firm contraindication — options: partial crown for common path, orthodontic uprighting, or non-rigid connectors).
Single point of failure — failure of one abutment usually means remaking the entire prosthesis (unlike independent implants).
Distal cantilevers in the posterior — highly undesirable due to leverage forces.

Compare PVS monophase and dual-phase impression techniques, and state which gives better margin detail.

PVS Monophase: medium/heavy-body PVS used in both the tray and on the preparation. Not recommended due to lower definition.
PVS Dual-phase: heavy/medium-body in the tray with light-body expressed on the tooth.
Dual-phase is more accurate for fine margin detail — the low-viscosity wash captures fine anatomy while the heavier body provides dimensional stability/support.

Compare the one-step and two-step putty-wash techniques and rank their accuracy.

1-Step (simultaneous): putty placed in the tray while light-body wash is syringed on the preparation; the tray is seated immediately so putty and wash set together. A common error is describing it as a two-step sequence — it must be simultaneous.
2-Step (sequential): an initial putty impression is taken and removed, a cut-out/relief is created for the wash, then light-body wash is applied and the tray re-seated.
The 2-step technique is more accurate, because a controlled, uniform wash thickness improves detail reproduction and reduces distortion.

From most to least accurate, how do the impression techniques rank, and what is required for full marks when describing the material?

L2 Classification and Clinical rationale_integrated

Two-step putty-wash — good accuracy (controlled uniform wash space).
PVS dual-phase (light-/heavy-body) — accurate for fine margins.
One-step putty-wash — significantly lower accuracy than two-step.
PVS monophase — lowest definition; not recommended.
For full marks, specify the exact material used (e.g., light-body vs heavy-body), not the generic term “impression material.”

L2 — Classification & Clinical Rationale

Describe the two main branches of fixed dental prostheses and how each is retained.

Fixed dental prostheses divide into:

Tooth-supported (crown & bridge) — retained as either cement-retained or resin-bonded.
Implant-supported (crown & bridge) — retained as either screw-retained or cemented.

FPDs are one of several tooth-replacement options, alongside complete dentures, removable partial dentures, and implant-supported prostheses.

Compare the Rochette and Maryland bridges in the evolution of resin-bonded techniques.

L2 Classification and Clinical rationale_integrated

Rochette bridge (1970s) — an early design using macroscopic mechanical retention via perforations in the metal wing. Limitation: the perforations weakened the metal structure, leading to long-term failures.
Maryland bridge — a refinement using electrochemical (electrolytic) etching to create micromechanical retention without perforations, improving the resin bond.

List the advantages of resin-bonded bridges.

L2 Classification and Clinical rationale_integrated

Minimal tooth preparation — minimal removal of tooth structure (typically a wing thickness of 0.8 mm).
Supragingival preparation — allows easy impression making.
Efficiency — an interim restoration is not usually required between preparation and cementation.

List the disadvantages of resin-bonded bridges.

L2 Classification and Clinical rationale_integrated

Reduced longevity compared with conventional FPDs (survival ~87% at 5 years vs >90% for conventional bridges).
Nickel allergies (specifically for metal wings).
Limited ability to correct space discrepancies.
Requirement for good alignment of abutment teeth.
Compromised anterior esthetics (potential metal show-through).

List the indications and contraindications for a resin-bonded bridge.

L2 Classification and Clinical rationale_integrated

Indications:

Short edentulous spaces (single tooth replacement).
Healthy/unrestored abutments with sufficient enamel surface for bonding.
Significant clinical crown length (adequate surface area).
Temporary restoration / space maintenance — e.g. young patients with continued growth where implants are contraindicated, or after orthodontic treatment before implant placement.
Open bite.

Contraindications:

Damaged or heavily restored abutments.
Large edentulous areas (multiple missing teeth).
Unfavourable angulation or rotation of abutment teeth.
Parafunctional habits or heavy occlusal forces.
Deep bite (insufficient clearance).
Mobile teeth.
Known alloy allergy.

Describe the preparation design features of a metal-ceramic resin-bonded bridge.

L2 Classification and Clinical rationale_integrated

The design must achieve stability, retention, and a single path of insertion, using:

Guide planes — maximum enamel contact, definitive POI, resistance to horizontal movement.
Axial grooves — increase resistance against horizontal displacement.
Rest seats — resist vertical occlusal forces, preventing gingival displacement.
Palatal preparation — extend approximately 2 mm from the incisal edge to avoid the “grey line” (metal show-through); use a dark object behind the incisor to evaluate translucency.
Cementation protocol — sandblast the metal retainers and use a dual-cure or chemical-cure adhesive resin cement containing MDP (e.g. Panavia).

State the connector dimensions and the role of interproximal wrap-around for all-ceramic RBBs.

L2 Classification and Clinical rationale_integrated

Connector dimensions — minimum 2 mm horizontal width and 3 mm vertical height to prevent fracture.
Interproximal wrap-around — essential to maximise bonded surface area; failure to incorporate it may result in a 50% failure rate within 3 years.

Other all-ceramic preparation principles: intra-enamel preparation, supragingival margins, maximised retainer surface area, bracing of abutments, single path of insertion, clearance for retainers, and rest seats.

State the survival data for all-ceramic resin-bonded bridges.

L2 Classification and Clinical rationale_integrated

5-year survival rate of 88–92%.
Debonding rate of 12.2%.
Fracture rate of 4.8%, typically occurring at the connector.

Describe fibre-reinforced bonded bridges, including the commercial systems and fibre types used.

L2 Classification and Clinical rationale_integrated

Fibre-reinforced bonded bridges can use either a natural tooth or an acrylic tooth as the pontic.

Commercial systems:
- everStick® range — NET, ORTHO, POST 1.2, PERIO, C&B.
- Ribbond® — uses a “lock stitch Leno weave” designed to prevent fibre pull-out (the weave tightens under tension rather than separating).
Fibre types: glass, polyethylene, Kevlar.
Structural configurations: woven, braided, unidirectional.
Minimum thickness/width: 3 mm.

List the 5 steps of the direct fibre-reinforced technique.

L2 Classification and Clinical rationale_integrated

Measurement — cut the ribbon using sharp scissors and an aluminium strip guide.
Base layer — apply 0.5 mm of packable composite (not flowable) to the etched tooth.
Fibre placement — soak the ribbon in unfilled resin (dipping resin) before adapting it to the composite.
Pontic attachment — use a 3 mm groove with an undercut in the pontic tooth for mechanical retention.
Finishing — overlay the ribbon with flowable composite to prevent tongue irritation (the ribbon is not polishable).

Describe the Shortened Dental Arch (SDA) concept and how occluding units are calculated.

L2 Classification and Clinical rationale_integrated

Per Witter et al. (1999), the SDA concept evaluates functional requirements by the number of occluding pairs:

A functional dentition is defined as no more than 20 teeth with intact anterior teeth but reduced posterior occluding pairs.
Modern soft diets do not require a complete 32-tooth arch.
Occluding units: premolars count as 1 unit each; molars count as 2 units each.
Distal extension cantilevers to replace second molars (7s) or bilateral free-end RPDs may represent overtreatment if functional goals are already met.

List the consequences of tooth loss.

L2 Classification and Clinical rationale_integrated

Masticatory efficiency — reduced chewing ability, which can affect systemic health.
Bone structure — loss of alveolar bone quality, width, and height.
Soft tissue — loss of soft tissue volume.
Aesthetics — compromised facial and dental appearance.
Phonetics — compromised speech, especially dental consonants.
Occlusal instability — migration of adjacent teeth, supereruption of opposing teeth, and loss of vertical dimension; can produce occlusal interferences, unbalanced muscle contraction, and TMD.

State Ante’s Law and explain how it guides abutment selection.

L2 Classification and Clinical rationale_integrated

Ante’s Law (Irvin Ante, 1926): “The root surface area (periodontal membrane) of the abutment teeth for an FPD must be equal to or greater than the root surface area of the teeth being replaced with pontics.”

Favourable example: the combined root surface area of the second premolar + second molar is greater than that of the first molar being replaced.
Contraindicated example: the combined area of the canine + second molar is exceeded by the teeth being replaced (1st premolar + 2nd premolar + 1st molar) — an FPD would be a poor choice here.

State the crown-to-root ratio requirements and how they are assessed.

L2 Classification and Clinical rationale_integrated

Minimum acceptable crown-to-root ratio: 1:1 (Shillingburg 1997).
Optimal crown-to-root ratio: 2:3.
Assessment: measured on periapical radiographs from the alveolar crest to the incisal edge versus the crest to the apex.

Describe how root shape, angulation, and surface area influence abutment suitability.

L2 Classification and Clinical rationale_integrated

Root configuration principle: the more difficult a tooth is to extract, the better it functions as an abutment. Favourable features include broad roots labiolingually, multi-rooted teeth, and divergent or curved roots rather than conical formations.
Root surface area governs Ante’s Law; e.g. mandibular first molar ≈ 431 mm², canine ≈ 268 mm², central incisor ≈ 154 mm². Larger-area teeth make stronger abutments.

Explain the biomechanics of secondary retention and arch shape in bridge design.

L2 Classification and Clinical rationale_integrated

Secondary retention (R) must extend a distance from the primary interabutment axis equal to the distance the pontic lever arm (P) extends in the opposite direction.
During pontic flexion the primary abutments act as fulcrums and the secondary retainers are placed in tension; therefore secondary retainers must be equally or more retentive than the primary retainers, and these teeth face an increased risk of undetected caries (debonding first).
V-shaped arches: replacing four incisors using only the canines as abutments creates lever arms that produce heavy torquing forces.
Opposing arch management: overerupted teeth may require opening the vertical dimension, reduction, or orthodontic intrusion to create prosthetic space.

Describe the double-cord retraction technique for soft tissue management.

L2 Classification and Clinical rationale_integrated

First cord — size 000 or 00, placed with a rotational motion to avoid hooking the fibres.
Second cord — a larger size (0 or 1) placed over the first.
Timing — leave in place for 5 minutes for adequate displacement.
Note — use a single cord for shallow sulci in the anterior region.

L3 — Impressions & Soft Tissue Management

What are the three main objectives of a fixed-prosthodontic impression?

Exact duplication of the prepared tooth and the uncut tooth structure beyond the preparation, to allow evaluation of the location and configuration of the finishing line.
Duplicate the other teeth and soft tissue to permit proper articulation of the cast and correct contouring of the restoration.
The impression must be free of bubbles, especially at the finishing line and prepared surfaces.

The overall aim is to produce a dimensionally stable “negative” that serves as a mould for an analogue model or is scanned for a CAD/CAM (milled or 3D-printed) model.

List the principles of tooth preparation for an ideal impression.

Supragingival margins if possible.
Only minimally subgingival or intra-crevicular when subgingival placement is required.
Well-defined, smooth and continuous margins.
Well-finished and tidy preparation.
Atraumatic to the gingival tissues.

Supragingival or equigingival margins are preferred because they make tissue management and impression-taking significantly easier; subgingival margins may be needed for aesthetics (anterior teeth) or to cover existing deep restorations.

What is biologic width violation, and how is it assessed?

Violation occurs when a restoration margin is placed too deep within the sulcus, impinging on the biologic width.
Consequences: persistent chronic inflammation, and clinical attachment loss including alveolar bone loss and gingival recession.
Assessment — bone sounding: under local anaesthetic, a periodontal probe is pushed to the alveolar crest to measure the distance to bone; the sulcus depth is subtracted from this measurement.
A violation is diagnosed if the resulting distance is less than 2 mm.

Describe the three bone-sounding crest categories, including their percentages, measurements, and margin tolerance.

Normal Crest (85% of patients): gingival margin–to–bone crest = 3–4.5 mm. Tissues are stable and tolerate a subgingival margin of about 0.5 mm; they recover well from minor trauma (e.g. retraction cord).
High Crest (2% of patients): measurement < 3 mm. Biologic width is narrow, so a subgingival margin will almost certainly impinge on the biologic width, causing persistent inflammation.
Low Crest (13% of patients): measurement > 4.5 mm. Large biologic width with a fragile attachment susceptible to retraction-cord damage, often producing recession as the tissue heals back to a “normal crest” position.

State the margin placement guidelines for a normal-crest patient based on sulcus depth.

If sulcus probing depth is 1.5 mm or less → the margin may be placed 0.5 mm below the gingival crest.
If sulcus depth is more than 1.5 mm → place the margin in the sulcus at a depth that is half its probing depth.
If sulcus depth is greater than 2 mm → consider a gingivectomy to extend the tooth and create a 1.5 mm sulcus.
For an intra-crevicular margin, the maximum subgingival depth is around 0.7 mm.

These must be weighed against aesthetic concerns, especially anteriorly.

What are the aims of gingival displacement during impression taking?

Enlargement of the gingival sulcus.
Tissue deflection horizontally and vertically to display the margin and root surface.
Display the finishing line for the restoration.
Development of an adequate emergence profile.
Control of gingival bleeding and exudate.

List the four categories of gingival displacement methods with an example of each.

Mechanical — retraction cord; copper band.
Chemical — astringents (aluminium chloride, ferric sulfate); adrenaline (transient ischemia and epithelial shrinkage).
Combined — retraction cord + chemical; Expasyl (Kerr).
Surgical widening — electrosurgery; laser.

Describe retraction cord types, sizing, and the packing technique.

Action: cord is packed into the sulcus, stretching the circumferential periodontal fibres 0.3–0.4 mm.
Types: braided, knitted (e.g. Ultrapak, commonly used), twisted; medicated or non-medicated (Ultrapak-E contains epinephrine).
Sizes: 000, 00, 0, 1, 2 — chosen to suit sulcus depth and tissue biotype.
Technique: cut a length about 1.5× the tooth circumference; form a loop and use a rotational, tucking motion (not a straight up-and-down push), angling the instrument towards the tooth and the already-packed cord; leave the ends accessible on the buccal/lingual surface, not interproximally.
Leave the cord in place 3–5 minutes per manufacturer’s instructions.

Compare the single cord and double cord techniques.

Single cord — Indications: shallow sulcus, thin periodontium. Advantages: least traumatic, limited risk of gingival recession. Disadvantages: haemorrhage and exudate.
Double cord — Indications: deeper sulcus, when superior bleeding/fluid control is needed. Advantages: excellent lateral displacement, superior fluid control. Disadvantages: more time-consuming, more traumatic, unpredictable response in high/low crest patients.
Double cord method: 1st (thin, 000/00) cord placed deep below the margin for vertical displacement and left in during the impression; 2nd (larger, 0/1) cord on top for horizontal displacement, left ~5 min and removed just before injecting material.

Describe the chemical hemostatic agents used for gingival displacement.

Metallic salts act by causing transient ischemia, shrinkage of gingival tissues, and reduced gingival fluid flow.
Examples: aluminium chloride (Hemadent), aluminium sulfate, potassium sulfate, ferric chloride, ferric sulfate (Astringedent).
Adrenaline can cause tachycardia — use with caution in patients with sensitivity or cardiovascular disorders, as it can raise blood pressure and heart rate, especially on lacerated tissue.

What is Expasyl, and how is it used?

Composition: aluminium chloride with kaolin.
Provides both chemical and mechanical displacement — the kaolin clay expands as it sets, giving mechanical retraction.
Use: dispensed from a syringe, expands on setting, left for 1–2 minutes, then washed away with a water spray.
Can be combined with a small retraction cord placed at the base of the sulcus. (Traxodent is a related aluminium chloride paste.)

Compare electrosurgery and laser for surgical tissue management, including contraindications.

Electrosurgery — Advantages: lower cost than lasers, cuts rapidly, immediate hemostasis at proper intensity, nearly painless wound. Disadvantages: contraindicated with any electrical device (PACEMAKERS!), requires anaesthesia, burning smell, risk of overcutting, and must not be used around implants (high heat).
Laser — Advantages: minimal anaesthetic needed, does not harm dental hard tissue, can be used around implants and full-metal/PFM/amalgam/gold restorations. Disadvantages: costly, cuts much slower, time-consuming for large tissue, danger of the laser beam — requires protective eyewear for patient and team.
Surgical techniques remove the inner epithelial lining for better access/haemostasis but risk permanent damage (recession) and should be avoided on thin gingiva.

Why is impression timing important, and how long should provisional healing last?

Inflamed gingivae are swollen, making it impossible to prepare a predictable intra-crevicular margin and producing impressions complicated by uncontrolled haemorrhage.
Once periodontal inflammation resolves there will be recession, which can expose a margin captured while tissues were swollen.
Therefore achieve gingival health before definitive impressions, allowing 3–4 weeks of healing with a well-fitting provisional restoration.

Compare PVS, polyether, and alginate across the key impression-material properties.

Dimensional accuracy/stability: PVS and polyether stay accurate 1–2 weeks and are dimensionally stable; alginate is very unstable and must be poured immediately.
Hydrophilicity/wettability: Polyether is hydrophilic and copes better with oral moisture; PVS is hydrophobic and may form voids with poor moisture control (PVS has a moderately high contact angle, so surfactant sprays are sometimes used). A low contact angle / low wetting angle lets material flow into fine crevices and stone pour bubble-free.
Tear strength: polyether very high, PVS moderate, alginate very low.
Rigidity/elastic recovery: PVS has superior elastic recovery and is less stiff than the even more rigid polyether (hard to remove from undercuts); alginate is the least rigid.

List the historical order of elastomeric/impression materials.

Reversible hydrocolloid (and alginate, an irreversible hydrocolloid).
Polysulfides.
Condensation silicone.
Polyether.
Addition silicone (PVS).

Reversible hydrocolloid (e.g. agar) has excellent accuracy if poured immediately; polysulfides have good tear strength but an unpleasant odour and ~10 min set; condensation silicone releases water as a by-product (accuracy/stability issues) and is very hydrophobic.

Describe the available impression techniques (monophase, dual-phase, putty-wash).

Monophase: the same material is syringed on the prep and loaded in the tray — not recommended due to lower definition.
Dual-phase (light & heavy body) — the recommended single-stage technique: light body (low viscosity) is syringed around the prep for fine detail, heavy body (high viscosity) in the tray for support; they bond and set together.
Dual-phase putty-wash (1-step): light body on the prep, putty in the tray inserted simultaneously — significantly lower accuracy than two-step.
Two-step putty: a putty impression is taken first, a cut-out/spacer creates room, then light-body wash is applied — good accuracy (a spacer is recommended). Both 1- and 2-stage are clinically acceptable (marginal gap < 120 µm).

Describe the clinical steps for intra-oral impression material application.

Remove the second cord (double-cord technique) / rinse off Expasyl.
Adequately dry the preparation and ensure good isolation (tongue, etc.).
Inject material starting from the hardest area (interproximals), keeping the tip submerged in the material.
Inject on top of the margins/sulcus areas in one continuous direction, covering the entire prep and part of the adjacent teeth.
Optionally air-thin the material with the triplex.
Seat the tray with a slow, continuous movement from back to front to direct excess forward, and hold steady for the full setting time.

Troubleshoot common impression defects: bubbles, drag lines, and incomplete set.

Bubbles — Cause: moisture/blood contamination or air incorporated during application. Solution: ensure a dry field with good hemostasis and keep the syringe tip submerged.
Drag lines — Cause: material began setting before the tray was fully seated, or the tray moved (working too slowly). Solution: improve workflow efficiency and have all materials ready.
Marginal tears — relate to inadequate tear strength / thin margins of material at the finish line.
Incomplete set — Cause: removing too soon, contamination with latex/sulfur, or an incorrect mix ratio from a blocked cartridge. Solution: time the set accurately, use nitrile gloves, and bleed the cartridge before use.

L4 — Try-In

What are the features of an ideal fixed indirect restoration (crown)?

An ideal crown should be:

Easily seated (seats without forcing)
Stable (no rocking or rotation under force)
Accurate occlusal contact
Adequate proximal contacts
Accurate marginal fit
Aesthetic

Why is thorough evaluation BEFORE cementation so critical?

Once a crown or FPD is cemented with permanent cement, there is no quick “undo” button for large modifications. Failure to properly evaluate the restoration before cementation risks:

Debonding
Recurrent caries
Patient dissatisfaction

A pre-appointment evaluation on the master cast should occur 1–2 working days before the patient appointment to allow for laboratory corrections without wasting chair time.

Describe how you evaluate the die and opposing model. What do specific defects indicate?

Inspect both die and opposing model under good lighting and magnification for: poor pouring, overtrimming, fracture, scratches, and wear. Key interpretations:

Over-trimming around proximal surfaces → may result in over-contoured crowns.
Wear on opposing models → may indicate artificially high occlusion, necessitating more clinical adjustment.
Sectioning and pinning: the die should be removable so interproximal margins can be visualised from all angles.

What do you look for when inspecting the INTERNAL surface of a casting on the die?

Casting problems: check for air bubbles.
Surface irregularities: identify casting nodules or blebs.
Seating principle: ideally the casting should touch the die at the margins only.
Die spacer: ensure appropriate application to accommodate the cement lute.

Complete the laboratory error checklist: state the cause and remedy for each common lab error found on the die.

Tight proximal contacts — Cause: imprecise die location or abrasion of stone contact points. Remedy: check for die displacement, identify with articulating paper, grind and polish.
Casting blebs on fit surface — Cause: air bubbles trapped during investment. Remedy: identify under magnification and remove with a small round bur.
Over-extended margins — Cause: poor impression, trimming, or surplus wax/porcelain. Remedy: trim from axial surface and polish; consider returning to lab.
Under-extended margins — Cause: poor impression or difficulty identifying finish line. Remedy: if obvious, have crown remade; alternatively retake impression.
Damaged dies — Cause: chipped finish line or abrasion from reseating faulty castings. Remedy: determine cause; if fit fails after adjusting blebs, return to lab.
No die spacer — Cause: technician error/lack of awareness. Result: tight fit; crown may not seat or may ‘lift’ after cementation.

List the potential causes of a crown FAILING TO SEAT on the prepared tooth (single crowns and FPDs).

The crown should seat without forcing. Causes of seating failure:

Single crowns:

Proximal contact issues
Internal fit discrepancies
Inaccurate margins / over-extensions
Retained temporary cements
Trapped gingival tissue

Fixed partial dentures (FPDs) — all of the above plus:

Tissue contact under pontics
Location and shape of connectors

Describe the instruments and technique for removing the provisional restoration.

Instruments:

Excavator, sickle probe
Hemostat, Backhaus forceps, pliers
Crown removers: back-action, automatic, Richwill

Technique:

Gauze and forceps: apply a gentle rocking motion to break the temporary cement bond.
Vertical sectioning: if the preparation is too parallel, section the provisional vertically from buccal to lingual; ensure cuts only penetrate the temporary material (identified by the white opaque cement layer).
Cleaning: use an ultrasonic scaler to remove all residual temporary cement from the prepared tooth.

How do you assess proximal contacts of the seated crown? Give the relevant material thicknesses.

Assess tightness with dental floss — there should be some resistance but not excessive.
Use articulating paper (20 μm), marking liquid (Accufilm), or sprays (Occlude) to identify and visualise the contact.
Shim stock (8 μm): should just pass through the contact.
Make minor adjustments incrementally; adjust one side at a time and check frequently (mobile adjacent teeth may affect the opposite contact).
Proximal contacts should be in the same location as the natural proximal contacts.
Open/missing contacts: return the crown to the lab for material addition.

How is internal fit assessed and adjusted? What if the crown fits the model but not the mouth?

The restoration must seat completely without interference from occlusal or axial surfaces.

Detection methods: disclosing medium (Fit Checker, light-body impression material) or aerosol indicators (Occlude spray).
Interpreting Fit Checker: areas where the medium is penetrated/thinned out indicate high spots / interference and should be adjusted to allow full seating.
Adjustment: relieve high spots with a diamond bur.
Fits model but not mouth → suspect an impression error: early impression removal, distortion, or latex contamination. Action: take a new impression.

What marginal gap is acceptable, and what are the visual classifications of margins?

A gap of 100 microns is the borderline for acceptability (detectable by probe).

Visual classification of margins:

Ideal: perfect adaptation to the finish line.
Overextended: material extends beyond the finish line.
Underextended: material stops short of the finish line.
Overhang: excess material creating a shelf.
Open margin: a visible gap between restoration and tooth.

List the effects of open margins.

Open margins can lead to:

Sensitivity
Dissolution of cement
Plaque retention
Secondary caries
Gingival inflammation

When can a marginal error be adjusted, and when must the restoration be REMADE? From which surface do you adjust?

Poor marginal fit often stems from the technician’s inability to clearly identify the finish line.

Overhangs / overextensions: can typically be adjusted.
Underextensions: usually require a remake.
Gaps: require a remake.

Adjustment rule: adjust overextended margins/overhangs from the external surface only. Never adjust the fitting (internal) surface, as this compromises the seal. If marginal fit remains inadequate, a new impression is necessary.

How do you assess the STABILITY of the seated crown, and what causes instability?

The restoration should not rotate or rock when force is applied.
Instability often leads to cementation failure.
Cause: internal surface misfit due to distortion in the impression or fabrication process.

Describe the shim stock procedure for assessing occlusion and how you interpret a “high” restoration.

Shim stock (8–10 μm) determines whether an occlusal contact is present. The crown must be fully seated before checking occlusion.

Procedure:

Assess occlusion on all teeth without the prosthesis.
Assess occlusion with the prosthesis in place.
Specifically assess the contact on the crown itself.

Interpretation: if adjacent teeth held shim stock before insertion but no longer do while the restoration holds it, the restoration is too high.

Goal (completed adjustment): posterior — prosthesis and remaining dentition hold shim stock equally; anterior — prosthesis should lightly hold shim stock if other anterior teeth do.

Explain articulating paper colour coding and the occlusal adjustment guidelines (including key constraints).

Colour coding (distinguishes mandibular movements):

Dark paper (e.g. Blue): Centric Relation (CR) / Maximal Intercuspation (MIC).
Lighter paper (e.g. Red): eccentric positions (protrusion, lateroprotrusion).

Adjustment guidelines:

Premature contact (centric): adjust grooves or cusp inclines. Never adjust the tip of a functional cusp.
Interferences (eccentric): adjust cusp inclines; adjust cusp tips only if absolutely necessary.
Anaesthesia caveat: numb patients have unreliable proprioception → schedule a review appointment in 1–2 weeks for fine-tuning.
Opposing tooth: if a cusp tip must be modified to preserve a scheme like canine guidance, consider adjusting the opposing tooth slightly instead of the new restoration.

L5 — Clinical Examination of Occlusion

Define occlusion according to the Glossary of Prosthodontic Terms.

Occlusion is defined as:

The act or process of closure, or of being closed or shut off.
The static relationship between the incising or masticating surfaces of the maxillary and mandibular teeth (or tooth analogues).

Describe the components of the masticatory system.

The masticatory system is composed of:

Teeth
Periodontium
Articulatory system — which specifically includes the TMJ and the muscles (of mastication).

These components are interconnected, so isolated teeth cannot be treated separately.

List the indications for occlusal analysis.

Prosthodontic treatment
TMJ/muscles assessment
Periodontal assessment
Mobility assessment
Functional discomfort
Mechanically failed restorative treatment
Bruxism diagnosis
Orthodontic treatment

A single crown with a stable, functional occlusal scheme may not require a detailed assessment session, whereas complex oral rehabilitation always does.

Why is obtaining a good occlusal record important? List its purposes.

An occlusal record serves a function similar to a periodontal chart (monitoring health and disease) and is essential for:

Establishing a baseline record
Monitoring occlusal changes
Monitoring disease development
Assessing treatment implications and evaluating treatment success over time

What three components are assessed during clinical examination of occlusion, and how are extra-oral vs intra-oral assessments divided?

The three components are the TMJ, masticatory muscles, and dental occlusion.

Extra-oral: masseter, temporalis, medial pterygoid, cervical and suprahyoid muscles; TMJ.
Intra-oral: lateral pterygoid, medial pterygoid; dental occlusion.

What does TMJ examination aim to identify, and how is the TMJ palpated?

Examination aims to identify:

Pain (chronic or acute)
Sound (clicking or crepitus)
Limited movement (locking or trismus)
Midline deviation and deflection

Palpation techniques:

TMJ capsules — palpating the joint area.
Posterior palpation — index fingers in the ears as the patient opens and closes.
Lateral palpation — external assessment of the joint; palpate anterior to the auricular tragi to assess for symmetrical condylar movement. Asynchronous movements suggest disc displacement.

Evaluation criteria: pain, joint sound, and disc movement.

Compare midline deviation and midline deflection, and link each to a disc-displacement pattern.

Midline deflection: continuous displacement of the mandibular midline (the mandible does not return to centre). A sign of Anterior Disc Displacement (ADD) WITHOUT reduction.
Midline deviation: the mandible returns to the centred position; indicates interference during condyle movement, often a jagged transition on opening/closing. A prominent sign of ADD WITH reduction.

What does the evidence say about using occlusal adjustment to manage TMD?

Altering occlusion to treat TMD/facial arthromyalgia was common historically but is NOT supported by evidence.
Any TMD-related occlusal treatment should be conservative and reversible (e.g., occlusal splint, removable prosthesis).
TMD should be stabilised before extensive prosthodontic treatment.
The patient must be informed that prosthodontic treatment is not aimed at restoring TMJ health.

Describe the palpation findings and anatomy (actions/nerve) of the masseter and temporalis muscles.

Masseter:

Tenderness on palpation may suggest occlusal interferences or nighttime bruxing; hypertrophy indicates strong clenching.
Actions: elevation (closing) and protrusion of the mandible. Nerve: mandibular nerve (V3).

Temporalis:

Pain often reported as headaches or pain behind the eye.
Actions: elevation and retraction of the mandible. Nerve: deep temporal nerves (V3).

How are the medial and lateral pterygoid muscles assessed, and what are their actions?

Medial pterygoid:

Palpated medial to the mandibular angle; intra-orally behind the molars along the buccal surface of the ramus. Tenderness here is a dependable landmark for occluso-muscular imbalance.
Actions: elevates mandible, closes jaw, assists in side-to-side movement.

Lateral pterygoid:

Difficult to palpate directly; assessed by resistance testing — the patient protrudes the chin against the clinician’s fist. Pain suggests lateral pterygoid involvement.
Actions: depresses and protrudes the mandible; facilitates side-to-side movement.

Which muscle group is examined for forward mandibular posturing, and name the four suprahyoid muscles.

The suprahyoid muscles are palpated; they are often involved when the mandible is postured forward to avoid deflective occlusal interferences. The four are:

Digastric — depresses mandible, elevates hyoid.
Stylohyoid — initiates swallowing (pulls hyoid posteriorly/superiorly).
Geniohyoid — depresses mandible, elevates hyoid.
Mylohyoid — elevates hyoid and the floor of the mouth.

State the normal functional ranges of mandibular motion.

Opening: 40–50 mm (an inter-incisal opening of < 40 mm may hinder prosthodontic treatment).
Lateral movements: 7–15 mm
Protrusive: 7–15 mm

A quick clinical screen for normal opening is the “three-finger width” rule.

Distinguish static and dynamic occlusal parameters assessed during dental occlusion examination.

Static parameters:

Centric occlusion and MIP (long centric / eccentric)
Freedom in centric
Extent of posterior tooth support
Angle’s classification
Overbite and overjet
Cross bite

Dynamic parameters:

Protrusion
Lateral movements (canine guidance, group function)
Balanced occlusion
Interferences

Define the three types of occlusal interference.

Centric interference: premature contact during closure to the optimal position.
Working/Non-working interference: contacts on the side of (working) or opposite to (non-working) the direction of mandibular movement — non-working interferences are particularly destructive.
Protrusive interference: premature posterior contacts during forward movement.

What is fremitus, how is it assessed, and what does it indicate?

Definition: vibration or movement of teeth during light tapping.
Method: place a finger across the tooth while the patient taps the teeth together and observe movement.
Significance: indicates the presence of deflective contacts — i.e., excessive loading or premature contacts.

List the clinical signs of bruxism.

Worn teeth
Muscle tenderness
Muscle hypertrophy
Cracked teeth
TMJ pain, locking, or clicking

State the Miller classification of tooth mobility (degrees 0–3).

Degree 0: “Physiological” mobility (0.1–0.2 mm horizontal).
Degree 1: ≤ 1 mm horizontal mobility.
Degree 2: > 1 mm horizontal mobility.
Degree 3: Both horizontal and vertical mobility.

How can loss of posterior support lead to tooth migration?

Posterior deflective contacts or loss of posterior support can cause drifting of maxillary incisors, leading to open contacts and food impaction.
Other positional changes include over-eruption of unopposed teeth and drifting/tilting of teeth.
Occlusal trauma may appear radiographically as a thickened PDL or blunted root tips.

Define RVD, OVD and freeway space, and state the typical freeway space value.

Rest Vertical Dimension (RVD) — the vertical dimension at rest; can be measured after the patient says the word “Emma”.
Occlusal Vertical Dimension (OVD) — the vertical dimension in occlusion.
Freeway Space (FWS) — the difference between RVD and OVD; usually approximately 3 mm.

List the five criteria of ideal occlusion.

Mandibular stability
Axial occlusal load
No interference on the working side during lateral excursions
Disocclusion on the non-working side during lateral excursions
Disocclusion of posterior teeth during protrusion

Compare the conformative and reorganised approaches to prosthetic treatment.

Feature	Conformative	Reorganised
Principle	Restorations made in harmony with existing jaw relations	Alters the occlusal scheme to establish ideal/near-ideal occlusion
Reference position	MIP (Maximal Intercuspal Position)	Centric Relation (CR)
Effect on other teeth	Occlusal contacts on unrestored teeth remain unaltered	New occlusion established (via provisionals) before definitive prosthesis
Stages	Fewer; fits existing scheme	Additional stages; mock-ups (e.g., Luxatemp) first

CR is used in the reorganised approach because it is a reproducible position independent of tooth contact.

List the advantages of the conformative approach.

Most cost-effective restorative method.
Requires the least restorative intervention.
Most common method in restorative dentistry.
Applicable for single or multiple restorations.
Easiest and safest — less likely to introduce new problems to the teeth, periodontium, muscles, or TMJ.

It should be considered the first treatment option as it is easier and more predictable.

List the indications for the reorganised approach.