AGD Operative and Restorative Dentistry Questions and Answers — Questions and Answers
Question 1: A 45-year-old patient presents with a large, failing amalgam restoration on tooth #30 with recurrent decay on the mesial-occlusal-distal (MOD) surfaces. The facial and lingual cusps are undermined but intact. The patient has a history of bruxism. Which of the following is the most appropriate definitive restoration?
- A large MOD composite restoration
- A full gold crown
- A ceramic onlay (Correct answer)
- A new, larger MOD amalgam restoration
Correct answer: A ceramic onlay
A ceramic onlay is the most appropriate choice because it provides cuspal coverage to protect the undermined cusps from fracture, which is crucial for a patient with bruxism. Unlike a full crown, it conserves more tooth structure. A large direct composite or amalgam restoration would not adequately protect the weakened cusps and would be more prone to fracture under heavy occlusal forces.
Question 2: Which of the following components of a dental adhesive system is primarily responsible for dissolving the smear layer and demineralizing the enamel and dentin to create microporosities for bonding?
- Primer
- Adhesive resin
- Silane coupling agent
- Acid etchant (Correct answer)
Correct answer: Acid etchant
The acid etchant, typically a 30-40% phosphoric acid solution, is used to demineralize the tooth structure. This process removes the smear layer and creates a porous surface on both enamel and dentin, which allows the primer and adhesive resin to penetrate and form a micromechanical bond.
Question 3: When preparing a Class II slot preparation for a posterior composite restoration, which principle of cavity preparation is de-emphasized compared to a traditional amalgam preparation?
- Removal of all carious dentin
- Achievement of a 90-degree cavosurface margin
- Creation of convergent occlusal walls for retention (Correct answer)
- Establishing adequate moisture control
Correct answer: Creation of convergent occlusal walls for retention
Modern adhesive dentistry relies on micromechanical bonding for retention, not mechanical undercuts. Therefore, the creation of convergent occlusal walls for retention, a key principle for amalgam restorations, is de-emphasized or eliminated in composite preparations. Instead, preparations for composites often have divergent or parallel walls to conserve tooth structure.
Question 4: A patient presents for a routine check-up. Radiographs reveal an incipient carious lesion confined to the enamel on the distal surface of tooth #12. The patient has low caries risk and excellent oral hygiene. What is the most appropriate initial management?
- Initiate topical fluoride varnish application and monitor the lesion. (Correct answer)
- Perform a Class II composite restoration immediately.
- Place a preventive resin restoration (sealant).
- Prescribe a high-fluoride toothpaste and restore in six months.
Correct answer: Initiate topical fluoride varnish application and monitor the lesion.
For an incipient, non-cavitated carious lesion limited to enamel in a low-risk patient, the most conservative and appropriate approach is non-invasive treatment. This involves attempts to remineralize the lesion through topical fluoride application and patient education, with radiographic monitoring at subsequent appointments. Restoring the tooth immediately would be overly aggressive.
Question 5: The 'C-factor' (Configuration factor) in operative dentistry is a ratio of bonded to unbonded surfaces in a cavity preparation. Which of the following preparation types has the highest C-factor, increasing the risk of polymerization shrinkage stress?
- Class IV
- Class III
- Class I (Correct answer)
- Class V
Correct answer: Class I
A Class I preparation is a 'box' with five bonded surfaces (mesial, distal, facial, lingual, and pulpal) and only one unbonded (occlusal) surface. This creates a high ratio of bonded-to-unbonded surfaces, leading to the highest C-factor. High C-factors concentrate the stress from polymerization shrinkage at the adhesive interface, increasing the risk of bond failure, marginal gaps, and postoperative sensitivity.
Question 6: Which of the following materials is classified as a glass ionomer but has been modified with the addition of a resin component to improve its physical properties and allow for light-curing?
- Traditional glass ionomer
- Resin-modified glass ionomer (RMGI) (Correct answer)
- Compomer
- Giomer
Correct answer: Resin-modified glass ionomer (RMGI)
Resin-modified glass ionomers (RMGIs) are hybrid materials that combine the chemistry of traditional glass ionomers (acid-base reaction, fluoride release) with that of composite resins (light-cured polymerization). This modification enhances their strength, wear resistance, and esthetics while simplifying the setting process compared to conventional glass ionomers.
AGD Operative and Restorative Dentistry Questions and Answers
A 45-year-old patient presents with a large, failing amalgam restoration on tooth #30 with recurrent decay on the mesial-occlusal-distal (MOD) surfaces.
The facial and lingual cusps are undermined but intact.
The patient has a history of bruxism.
Which of the following is the most appropriate definitive restoration?