DBT-BET cheat sheet

Universal numbering: 1–32 begins at maxillary right third molar (1) and ends at mandibular right third molar (32); FDI uses two digits (quadrant 1–4 + tooth 1–8).

Permanent dentition chronology: first molars erupt ~6 years, central incisors 6–7, canines 11–12, second molars 12–13, third molars 17–21 years.

Primary dentition: 20 teeth; FDI quadrants 5–8; incisors erupt 6–10 months, first molars 12–16 months, second molars 20–30 months.

Maxillary first molar: 3 roots, 4 canals in ~60–70% of cases (MB2), rhomboidal occlusal outline; mandibular first molar: 2 roots, 3 canals, 5 cusps.

Mandibular central incisor is the smallest permanent tooth; maxillary canine has the longest root and is the longest tooth overall.

Curve of Spee: anteroposterior occlusal curve from canine tip through buccal cusps; Curve of Wilson: mediolateral curve, concave in maxilla, convex in mandible.

Overjet = horizontal distance from maxillary incisal edge to labial surface of mandibular incisor (normal 2–3 mm); overbite = vertical overlap (normal 2–3 mm, ~20–30%).

Cusp of Carabelli is a supplemental cusp on the mesiolingual surface of maxillary molars, most common on the first molar.

Amalgam: high-copper (>30% Cu) is admixed or spherical; low-copper is gamma-2 prone. Creep <3% and compressive strength ~400–500 MPa.

Composite: Bis-GMA (rigid, viscous), UDMA (lower viscosity), TEGDMA (diluent, increases shrinkage); filler load 60–87 wt% reduces shrinkage and wear.

Polymerization shrinkage: bulk-fill and flowable composites shrink 2–6% by volume; C-factor = bonded/unbonded surface area; incremental layering ≤2 mm controls stress.

Glass ionomer: acid-base reaction of fluoroaluminosilicate glass with polyacrylic acid; releases fluoride, chemical bond to tooth, low flexural strength (~15–25 MPa).

Zirconia: 3Y-TZP is metastable tetragonal; transformation toughening occurs on stress; high flexural strength (~900–1200 MPa); low-temperature degradation (aging) is a risk.

Eugenol inhibits polymerization of resin; zinc oxide-eugenol is a sedative temporary luting agent, contraindicated under composite restorations.

Elastomeric impression materials: addition silicone (polyvinyl siloxane) is most dimensionally stable; condensation silicone releases alcohol and shrinks; polyether is hydrophilic but stiff.

Dental porcelain CTE ~13–14 ×10⁻⁶/°C; metal-ceramic alloys require CTE mismatch within ~1–2 ×10⁻⁶/°C to avoid chipping/tension.

Tooth preparation convergence for fixed prostheses: ideally 4–6° total taper (per wall ~2–3°); >10–12° lowers retention significantly.

Minimum occlusocervical height for retention: ~4 mm for anterior, ~4–5 mm posterior; resistance form requires a flat occlusal floor and axial wall height.

Finish line selection: chamfer for metal/ceramic (0.5–1.0 mm), shoulder for all-ceramic (1.0–1.5 mm), knife-edge contraindicated for zirconia.

Ferrule effect: ≥1.5–2 mm of circumferential dentin coronal to the finish line improves fracture resistance of endodontically treated teeth.

Cementation: resin cement for zirconia and glass-ceramics after HF etching + silane (glass-ceramic) or MDP primer (zirconia); RMGI for metal-based restorations.

Pontic design: modified ridge lap and ovate preserve esthetics and tissue health; sanitary (hygienic) pontic is used in posterior non-esthetic areas.

Occlusal adjustment: aim for light, even contacts in centric occlusion and disclusion in excursions; avoid heavy contacts on inclined planes.

Implant crown: screw-retained preferred when retrievability or angulation allows; cement-retained requires meticulous cement cleanup to prevent peri-implantitis.

Complete denture: primary impression with irreversible hydrocolloid or stock tray; final impression with border molding using modeling compound and light-body elastomer.

Posterior palatal seal: 1–1.5 mm of compression at the junction of hard/soft palate (vibrating line), placed within the denture base to improve retention.

Neutral zone: space where forces from tongue, lips, and cheeks balance; teeth should be placed in this zone to improve stability.

Balanced occlusion: bilaterally simultaneous contacts in centric and eccentric movements; lingualized occlusion is common for resorbed ridges.

RPD Kennedy classification: Class I bilateral posterior edentulous; Class II unilateral posterior; Class III unilateral bounded; Class IV anterior crossing midline.

Applegate's rules refine Kennedy classification; the most posterior edentulous area determines the class; third molars not replaced are not counted.

RPD components: rests (occlusal/cingulum) provide support; clasps (circumferential, RPI, RPA) provide retention; major connector (lingual bar, palatal plate) provides rigidity.

Denture base acrylic (PMMA) polymerization shrinkage ~6–8% by volume; processing with heat-cured resin minimizes residual monomer vs. autopolymerizing.

Angle classification: Class I = mesiobuccal cusp of maxillary first molar in buccal groove of mandibular first molar; Class II = MB cusp mesial to groove; Class III = distal.

Cephalometric landmarks: Sella, Nasion, A-point, B-point, ANS, PNS, Gonion, Menton; SNA ~82°, SNB ~80°, ANB ~2° (adult norms).

Frankfort horizontal vs. SN plane: FMA ~25°; IMPA ~90°; interincisal angle ~130–135°.

Crowding/space analysis: arch length discrepancy; mixed dentition uses Tanaka–Johnston (half of mesiodistal width of mandibular incisors + 10.5 mm per quadrant).

Force levels: light continuous forces ~50–100 g for intrusion, ~100–200 g for translation; heavy forces cause hyalinization and root resorption.

Anchorage: maximum (multiple teeth), moderate, minimum; TADs (miniscrews) provide absolute anchorage for en masse retraction.

Retention: fixed lingual bonded retainer or removable Hawley/essix; relapse risk highest in the first 6–12 months; lower incisor relapse is common.

Clear aligners: attachments improve rotation and extrusion control; interproximal reduction (IPR) creates space; aligner wear ≥20–22 h/day is required.

Hand hygiene: soap and water when visibly soiled or after C. difficile exposure; alcohol-based rub for routine non-soiled hands; wash 40–60 s, rub 20–30 s.

Spaulding classification: critical items (surgical, bone) require sterilization; semicritical (mirrors, impression trays) require high-level disinfection or sterilization; noncritical (surfaces) require low-level disinfection.

Sterilization monitoring: physical (autoclave gauge), chemical (indicator strips), biological (Geobacillus stearothermophilus for steam, Bacillus atrophaeus for dry heat/EO).

Autoclave cycles: 121°C at 15 psi for 15–30 min (gravity) or 132°C for 4 min (flash); wrapped instruments stored up to 6 months if integrity intact.

Bloodborne pathogens: HBV is most infectious; post-exposure prophylaxis for HBV and HIV; PEP for HIV started within 2 h, ideally ≤72 h.

PPE: gloves, mask, eye protection, and gown; change gloves between patients; masks should be changed when wet or after ~1 procedure.

Surface disinfection: EPA-registered hospital disinfectant with tuberculocidal claim; barriers preferred for high-touch surfaces (light handles, chair controls).

Sharps: no recapping by two hands; use one-handed scoop or needle-holding device; place in puncture-resistant sharps container filled to ¾.

Prescription requirements: dentist must provide written prescription including patient ID, material, shade, design, and date; lab must retain records per jurisdiction.

OSHA Bloodborne Pathogens Standard (29 CFR 1910.1030) applies to dental labs; Hazard Communication Standard (1910.1200) requires SDS for chemicals.

Lab case tracking: log-in/log-out with patient name, dentist, date, and case type; traceability supports recalls and liability defense.

Infection control in lab: incoming impressions/items treated as potentially infectious; disinfect before handling; use separate receiving area.

Ethical principles: autonomy, beneficence, nonmaleficence, justice; informed consent requires capacity, disclosure, understanding, and voluntariness.

Scope of practice: lab technicians cannot diagnose or treat patients; only licensed dentists may prescribe or alter intraoral appliances.

Record retention: commonly 7–10 years for adults, longer for minors; check state/provincial dental board rules.

Advertising and fee splitting: prohibitions vary by jurisdiction; fee splitting for patient referrals without disclosure is generally unethical.

Intraoral scanner (IOS) accuracy: trueness ~20–50 µm for full arch; accuracy degrades with span length, so full-arch scans need strategic stitching.

STL stores surface geometry (triangles); PLY can store color; 3MF supports color, materials, and metadata; DICOM is for CBCT and must be merged with STL for implant planning.

CAD design: occlusal clearance typically 1.0–1.5 mm for zirconia, 1.5–2.0 mm for porcelain; cement space 30–80 µm for resin cement.

Milling: subtractive; zirconia green state machined then sintered (~1450–1500°C), shrinkage ~20–25% compensated by CAM.

3D printing: vat photopolymerization (SLA/DLP/LCD) for models and surgical guides; layer thickness 25–100 µm; post-cure and wash steps affect accuracy and biocompatibility.

Digital shade and color: spectrophotometers convert to CIELAB; ΔE <1 is imperceptible, ΔE 1–2 is clinically acceptable, ΔE >3.3 is visibly different.

Implant planning software merges DICOM and STL; surgical guides require ≥3 mm safety offset from vital structures and sleeve height for drill control.

CAM nesting: sprue placement and support placement affect fit; zirconia crowns require uniform wall thickness (≥0.5 mm) to avoid fracture during sintering.