BDS Conservative Dentistry Syllabus

Why are high-copper amalgams superior to conventional low-copper amalgams?

They eliminate the weak, corrosion-prone $\gamma_2$ (Sn-Hg) phase by forming $\ce{Cu6Sn5}$ ($\eta'$ phase) instead, giving higher strength, better corrosion resistance, and less creep.

Define the main organic components of a resin composite (matrix and diluent).

The resin matrix is typically Bis-GMA (bisphenol A glycidyl methacrylate) or UDMA, with low-viscosity diluent monomers like TEGDMA to control viscosity.

What is the function of the filler particles in composite resin?

Inorganic fillers (quartz, silica, glass) increase strength and wear resistance, reduce polymerization shrinkage and thermal expansion, and improve esthetics/radiopacity. Higher filler loading generally improves mechanical properties.

What is the setting/curing mechanism of light-cured composite resin?

Free-radical addition polymerization initiated by a photoinitiator (camphorquinone) activated by blue light (~$468\,\text{nm}$), which reacts with an amine accelerator to generate radicals that polymerize the methacrylate monomers.

What is polymerization shrinkage in composites and its main clinical consequence?

Volumetric contraction (typically $2\text{–}5\%$) as monomers convert to polymer. It generates stress at the tooth-restoration interface, potentially causing gap formation, microleakage, marginal staining, and postoperative sensitivity.

What is the acid-etch technique and which acid/concentration is standard?

Applying $37\%$ phosphoric acid to enamel (~$15$–$30\,\text{s}$) to create microporosities into which resin flows and forms mechanical resin tags, providing micromechanical bonding. Dentin etching also removes the smear layer.

What is the acid-base setting reaction of glass ionomer cement?

An acid-base reaction between polyacrylic acid (liquid) and fluoroaluminosilicate glass (powder). Acid attacks the glass releasing $\ce{Ca^2+}$ and $\ce{Al^3+}$ ions that crosslink polyacid chains to form a hydrogel salt matrix.

State two major clinical advantages of glass ionomer cement.

(1) Chemical adhesion to enamel and dentin without a separate bonding agent, and (2) sustained fluoride release providing anticariogenic (remineralizing) action; it also has a thermal expansion similar to tooth structure.

What is a resin-modified glass ionomer (RMGIC)?

A GIC with added resin monomers (e.g., HEMA) and photoinitiators, setting by both the acid-base reaction and light-activated polymerization. It has improved strength, reduced early moisture sensitivity, and retains fluoride release.

State G.V. Black's classification of carious lesions/cavities (Class I–V).

Class I: pits/fissures (occlusal, buccal/lingual grooves). Class II: proximal surfaces of posterior teeth. Class III: proximal of anteriors NOT involving incisal angle. Class IV: proximal of anteriors involving incisal angle. Class V: gingival third (cervical) of all teeth.

What is a Class VI cavity (added to Black's classification)?

A lesion on incisal edges of anterior teeth or the cusp tips of posterior teeth (occurring on self-cleansing, wear-prone areas).

List the fundamental steps/stages of cavity preparation according to G.V. Black.

1) Outline form, 2) Resistance form, 3) Retention form, 4) Convenience form, 5) Removal of remaining carious dentin, 6) Finishing of enamel walls/margins, 7) Toilet (debridement) of the cavity.

Distinguish resistance form from retention form in cavity design.

Resistance form is the shape/thickness that enables both restoration and tooth to withstand masticatory forces without fracture (e.g., flat pulpal floor, adequate bulk). Retention form is the shape that prevents dislodgement of the restoration (e.g., dovetails, undercuts, parallel walls).

Define 'outline form' in cavity preparation.

The external shape/boundary of the cavity on the tooth surface, established by extending margins to include all carious tissue, defective pits/fissures, and placing margins on sound structure ('extension for prevention' in classic design).

What is the difference between the design principles for amalgam versus composite cavity preparations?

Amalgam requires mechanical retention (undercuts, defined resistance/retention form, ~$90^{\circ}$ cavosurface margins) because it is non-adhesive. Composite bonds adhesively, so preparations are more conservative, retention-independent, with beveled enamel margins and no need for extension for prevention.

Why is a cavosurface angle of about $90^{\circ}$ preferred for amalgam margins?

Amalgam is brittle in thin sections; a butt-joint $90^{\circ}$ margin gives amalgam adequate bulk/edge strength and avoids weak, feather-edged margins that fracture (amalgam requires a marginal angle near $70\text{–}80^{\circ}$ of amalgam, giving ~$90^{\circ}$ cavosurface).

Name the classes/types of instruments in the operative dentistry armamentarium.

Cutting hand instruments (excavators, chisels, hatchets, gingival margin trimmers, hoes), rotary cutting instruments (burs in high-/low-speed handpieces), and non-cutting instruments (condensers/pluggers, carvers, burnishers, matrices).

According to G.V. Black's instrument formula, what do the three (or four) numbers designate?

For a three-number formula: 1st = width of blade (tenths of mm), 2nd = length of blade (mm), 3rd = angle of blade to long axis of handle (centigrades/hundredths of a circle). A four-number formula inserts the cutting-edge angle as the 2nd number.

Differentiate high-speed from low-speed dental handpieces by rotational speed and use.

High-speed: $>200{,}000\,\text{rpm}$ (up to ~$400{,}000$), water-cooled, used for gross tooth reduction/caries removal. Low-speed: $<12{,}000\,\text{rpm}$, used for caries excavation near pulp, finishing, and polishing with greater tactile control.

What is trituration and why is proper trituration of amalgam important?

Trituration is the mechanical mixing (amalgamation) of alloy powder with mercury. Correct trituration ensures a workable, homogeneous mass; undertrituration gives a dry, grainy, weak mix, and overtrituration gives a hot, soupy mix with increased setting contraction and reduced strength.

What is condensation of amalgam and its purpose?

Packing the triturated amalgam into the cavity with pressure using condensers. It adapts amalgam to walls/margins, reduces voids/porosity, and expresses excess mercury toward the surface, improving strength and marginal seal.

Define creep as it relates to amalgam restorations.

Creep is the time-dependent plastic (permanent) deformation of amalgam under sustained load. High creep is associated with the $\gamma_2$ phase and leads to marginal breakdown ('ditching'); high-copper amalgams have much lower creep.

What is a matrix band and why is it needed for Class II amalgam/composite restorations?

A metal or clear band (e.g., Tofflemire matrix with retainer, or sectional matrix) that temporarily provides a missing proximal wall. It confines the restorative material, enables condensation, and helps establish proper contour and a tight proximal contact.

Compare amalgam and composite on three key clinical properties.

Esthetics: composite is tooth-colored, amalgam is metallic. Adhesion: composite bonds to tooth, amalgam does not. Technique sensitivity/durability: amalgam is more forgiving of moisture and highly durable in stress-bearing areas; composite is moisture-sensitive but conserves tooth structure and bonds.

What is the C-factor (configuration factor) in composite restorations?

The ratio of bonded to unbonded (free) surfaces of a restoration: $$C = \frac{\text{bonded surfaces}}{\text{unbonded surfaces}}$$ A higher C-factor means greater polymerization shrinkage stress; incremental layering reduces effective C-factor and stress.

Differentiate an inlay from an onlay.

An inlay is an indirect intracoronal restoration that fits within the prepared cavity without covering cusps. An onlay is an indirect restoration that covers (caps) one or more cusps, protecting weakened cusps while still being partial coverage.

When is a full crown indicated over a direct restoration?

When there is extensive loss of tooth structure, weakened/fractured cusps, following root canal treatment on posterior teeth, need for a full-coverage abutment, severe wear/erosion, or when esthetic/functional demands exceed what a direct filling can provide.

What is a dental veneer and what are the two main types?

A thin layer of restorative material bonded to the facial surface of a tooth to improve esthetics. Types: direct composite veneers (chairside) and indirect porcelain/ceramic veneers (laboratory-fabricated, bonded with resin cement).

Differentiate reversible from irreversible pulpitis.

Reversible pulpitis: brief, sharp pain to stimuli (cold/sweet) that stops when the stimulus is removed; pulp can heal if the irritant is removed. Irreversible pulpitis: spontaneous, lingering, often throbbing pain (may worsen with heat/lying down); the pulp is damaged beyond recovery and requires RCT or extraction.

Compare acute apical periodontitis and an apical (periapical) abscess.

Acute apical periodontitis: inflammation of periapical tissues causing pain to percussion/biting, tooth tender, often no swelling, minimal radiographic change early. Apical abscess: localized collection of pus with swelling, possible fever/lymphadenopathy, severe pain, and eventual periapical radiolucency.

What is root canal treatment (RCT) and its objective?

An endodontic procedure that removes infected/inflamed pulp, then cleans, shapes, disinfects, and obturates (fills) the root canal system to eliminate infection and prevent reinfection, thereby saving the natural tooth.

List the main sequential steps of root canal treatment.

Diagnosis and anesthesia, isolation with rubber dam, access cavity preparation, working length determination, cleaning and shaping (biomechanical preparation) with irrigation, obturation (commonly gutta-percha with sealer), and coronal restoration.

What is the most common irrigant used in RCT and why?

Sodium hypochlorite ($\ce{NaOCl}$, typically $1\text{–}5.25\%$) because it dissolves organic/necrotic tissue, is broadly antibacterial, and lubricates canals. EDTA is used adjunctively to remove the inorganic smear layer.