Iran Dental Board - Prosthodontics cheat sheet

Occlusal convergence: 6° total taper is the classic ideal; taper above 20° reduces retention, and auxiliary grooves or pins are indicated when taper cannot be controlled.

Finish lines: chamfer for cast metal and PFM; rounded shoulder for ceramic; feather edge is contraindicated because it gives an indistinct margin and inadequate ceramic support.

Reduction targets: full metal 0.5–1.0 mm; PFM 1.5–2.0 mm occlusal and 1.2–1.5 mm axial; monolithic zirconia at least 1.0 mm; lithium disilicate at least 1.5 mm occlusal.

Ferrule: 1.5–2.0 mm axial height and at least 1 mm dentin thickness, 360° ideal; improves fracture resistance of endodontically treated abutments.

PFM design: metal framework 0.3–0.5 mm; porcelain 1.0–1.5 mm; facial cutback provides porcelain support and esthetics.

Provisional restoration: stable centric stops, correct contours, and marginal seal; eugenol-containing temporary cement can inhibit resin bonding if used before adhesive cementation.

Cementation: resin cement for etched glass-ceramic and zirconia with appropriate primer; glass-ionomer for metal-based crowns; clean and isolate the field.

Try-in: verify marginal fit, proximal contacts, occlusion, and esthetics; heavy centric stops and excursive interferences are reduced before final cementation.

Freeway space: 2–4 mm at physiologic rest; planned occlusal vertical dimension must preserve this clearance.

Posterior palatal seal: between vibrating line and hard/soft palate junction, to hamular notches; about 1 mm displacement improves border seal.

Maxillary border: cover tuberosities and pterygomaxillary notch, stop at vibrating line; mandibular border covers retromolar pad and retromylohyoid space.

Balanced occlusion: bilateral simultaneous centric contacts plus eccentric contacts; lingualized occlusion concentrates forces on central fossae.

Retention: adhesion, cohesion, atmospheric pressure, and border seal; xerostomia and excessive resorption reduce retention.

Christensen phenomenon: in protrusion, posterior teeth separate when incisal guidance is steep; compensate with appropriate compensating curve and tooth arrangement.

Processing: PMMA linear shrinkage is about 0.5%; remount and refine occlusion after processing.

Neutral zone: tooth placement within tongue, lip, and cheek balance improves stability; verify with functional movements.

Kennedy: I bilateral distal extension; II unilateral distal; III unilateral bounded posterior; IV anterior crossing midline; Applegate rules determine final class.

Occlusal rest: 1.0–1.5 mm deep, 2.5 mm buccolingual, rounded triangular; floor inclined toward marginal ridge.

Lingual bar: at least 4 mm height, 1.5–2 mm thickness, 3 mm below gingival margin; insufficient space requires lingual plate or cingulum bar.

RPI: mesial rest, proximal plate, I-bar; reduces torque on distal extension abutments by allowing rotation around a mesial fulcrum.

Indirect retention: auxiliary rest on opposite side of fulcrum; indicated for distal extension and long-span RPDs.

Altered cast: functional impression of distal extension after framework try-in; captures tissue under load.

Combination syndrome: maxillary anterior resorption, mandibular posterior resorption, anterior occlusal plane changes; stable occlusion and tissue support reduce risk.

Major connector: rigid; avoid gingival and frenal impingement; relief under lingual bar.

Albrektsson success: no mobility or pain, less than 0.2 mm annual bone loss after first year, no peri-implant radiolucency.

Spacing: at least 1.5 mm implant-to-tooth, at least 3 mm between implants, at least 1 mm buccal/lingual bone.

Immediate loading: insertion torque at least 35 N·cm, good bone, no micromotion; splinting may be needed for multiple implants.

Single implant crown: light centric contact, no working or nonworking excursive contacts; avoids overload.

Impression: open tray splinted for multiple implants; closed tray for single well-aligned implants.

Cantilever: keep within anterior-posterior spread; increasing length raises screw, bone, and prosthetic stress.

Platform switching: narrower abutment shifts implant-abutment junction inward and may reduce crestal remodeling.

Peri-implantitis: bleeding or suppuration, probing depth at least 6 mm, bone loss at least 3 mm; treat with debridement and assess implantoplasty.

Centric relation: condyles anterior-superior against posterior slope of articular eminence, discs interposed, tooth-independent.

OVD at rest = OVD + freeway space; maintain 2–4 mm freeway space.

Mutually protected occlusion: posterior teeth protect anterior in centric; anterior teeth disclude posterior in excursion.

Canine guidance: working-side canine disclusion; group function shares contacts; nonworking interferences are harmful.

DC/TMD disc displacement with reduction: reproducible reciprocal click; MRI is reference for disc position.

Stabilization splint: full-arch flat plane, even centric contacts, anterior guidance; not a definitive cure for all TMD.

Maximum opening: 40–50 mm normal; less than 35 mm indicates limitation; deviation may reflect disc or joint pathology.

Imaging: CBCT for osseous changes; MRI for disc and soft tissue; avoid routine imaging for simple myalgia.

Amalgam: high compressive strength, creep, corrosion; avoid in esthetic zones and when isolation is inadequate.

Composite: polymerization shrinkage stress rises with C-factor; incremental layering and adequate light curing reduce marginal gaps.

Glass ionomer: fluoride release and chemical adhesion; lower fracture toughness, use in low-stress areas.

Zirconia: transformation toughening; flexural strength about 900–1200 MPa; opaque, often monolithic or veneered.

Lithium disilicate: flexural strength about 300–400 MPa; HF acid etch plus silane for adhesive bonding.

Addition silicone: accurate, hydrophobic, dimensionally stable; polyether: hydrophilic but stiff and moisture-sensitive.

Type IV stone: low setting expansion, high strength for dies; type III for casts.

Enamel etch: 37% phosphoric acid 15 s; dentin 10–15 s; over-etching dentin increases collagen collapse risk.

Shade selection: value first, then hue and chroma; neutral gray background and daylight; dehydration lightens teeth.

VITA classical: shades ordered by value; incisal translucency and surface texture affect perception more than chroma alone.

Digital workflow: intraoral scan → CAD → milling or printing; STL is the standard tessellation format.

Minimum thickness: monolithic zirconia about 0.5–1.0 mm; lithium disilicate about 1.0–1.5 mm; connector dimensions are critical.

CIE Lab*: L* lightness, a* red-green, b* yellow-blue; used for objective color difference.

Smile design: dental midline, incisal edge position, smile line, buccal corridor, gingival zenith; cross-check with facial landmarks.

Mock-up from wax-up: verifies esthetics, phonetics, and occlusion before final preparation.

Print orientation and post-curing affect resin restoration accuracy and mechanical properties; follow manufacturer parameters.

Obturator: surgical, interim, definitive; hollow bulb reduces weight; seal defect for speech and swallowing.

Aramany classification I–VI organizes edentulous maxillary resection defects by defect location and abutment distribution for framework design.

Facial prosthesis: silicone elastomer, adhesive or implant retention; color match and thin margins improve acceptance.

Radiation caries: xerostomia and fluoride deficiency; daily fluoride and 3-month recall; minimize trauma.

Denture stomatitis: Candida albicans; antifungal therapy plus denture hygiene and nighttime removal.

Geriatric xerostomia: polypharmacy common; root caries risk; fluoride varnish and chlorhexidine as indicated.

Mandibular two-implant overdenture: locator or bar retention; improves retention and function versus complete denture.

Residual ridge resorption: mandible greater than maxilla; greatest loss in anterior maxilla and posterior mandible.