AACD Sample Questions & Answers

The diagnosis of altered passive eruption, confirmed by the apical position of the CEJ relative to the gingival margin with adequate bone support, indicates that excess soft and hard tissue is covering the anatomical crowns. The definitive treatment is surgical crown lengthening, which involves a gingivectomy to expose the CEJ and osseous recontouring to re-establish a proper biologic width (approximately 3mm from the proposed gingival margin to the alveolar crest). This procedure will expose the correct tooth proportions and reduce the gingival display. Orthodontic intrusion is for vertical maxillary excess, veneers would create overly long teeth, and Botox is a temporary solution for a hyperactive lip, not a tissue problem.

A rocking or fulcrum effect is most commonly caused by a single point of contact on the internal (intaglio) surface of the restoration that prevents it from seating fully and stably. This is often a small positive bleb or nodule resulting from a minor imperfection in the die or the milling process. Using a fit-checking material (e.g., silicone paste or occlusal spray) will quickly identify the precise location of the interference, which can then be carefully adjusted. An over-tapered prep would lead to poor retention but not necessarily a specific rock. Sintering distortion is possible but less common. A die spacer issue would typically cause a universally loose or tight fit.

The Golden Proportion (approximately 1.618:1) suggests that, when viewing the smile from the front, each tooth should be about 61.8% of the size of the tooth immediately mesial to it. If the central incisor (the larger element) is 1.618, the lateral incisor (the next element) would be 1.0. Following this, the visible portion of the canine would be approximately 0.618.

The selective-etch (or selective enamel etch) technique combines the benefits of both self-etch and etch-and-rinse systems. By using the universal adhesive in self-etch mode on dentin, the smear layer is modified rather than completely removed, and the dentinal tubules are not exposed as aggressively, which significantly reduces the risk of post-operative sensitivity. Concurrently, selectively etching the enamel margins with phosphoric acid creates a deeper, more retentive etch pattern on the highly mineralized enamel, resulting in a stronger and more durable marginal seal. This hybrid approach optimizes the bond to both substrates.

A youthful and natural smile displays a progressive increase in the size of the incisal embrasures moving distally from the midline. The embrasure between the central incisors is the smallest, the one between the central and lateral is larger, and the one between the lateral and canine is the largest. This graduation helps to delineate the individual teeth and avoid a monolithic, unnatural appearance.

The most effective and conservative approach is to address the source of the discoloration first. By performing internal bleaching, the dark stump shade of tooth #9 can be lightened to match the adjacent teeth. This creates a uniform underlying color foundation, allowing for the use of the same high-translucency (HT) ceramic material across all veneers for a consistent and vital appearance. Relying solely on opaque cements or more opaque ceramics for just one tooth can lead to a devitalized, 'flat' look for tooth #9 that does not match the lifelike translucency of the other veneers.

The main difference between HT and LT lithium disilicate is the level of translucency. HT blocks are more translucent, allowing more light to pass through. This creates a chameleon effect, where the restoration picks up the color of the underlying tooth, resulting in a very natural and vital appearance, ideal for veneers on well-colored teeth. LT blocks are more opaque. While they appear less vital than HT restorations, their lower translucency is advantageous for masking moderately discolored underlying tooth structure or metal posts. Flexural strength and bonding properties are similar between the two.

Canine-guided occlusion is a protective occlusal scheme where, during lateral movements of the mandible, the canines on the working side are the only teeth that touch. Specifically, the lingual surface (or lingual incline) of the maxillary canine glides along the buccal incline of the mandibular canine. This contact effectively separates, or 'discludes,' all posterior teeth on both the working and non-working sides, preventing potentially damaging lateral forces on them.

Sharp internal line angles, such as a 90-degree angle at the junction of the axial wall and the gingival margin (shoulder), are major stress concentrators for brittle materials like ceramics. During function and thermal cycling, forces are focused on this sharp point, which can lead to crack initiation and eventual fracture of the porcelain veneer. All internal line angles in a ceramic preparation must be rounded to distribute stresses over a wider area.

It is a fundamental principle of restorative dentistry that a healthy periodontal foundation must be established before initiating definitive restorative treatment. Placing veneers in the presence of gingivitis will compromise the outcome due to bleeding during the procedure (contaminating the bond) and changes in the gingival margin position after healing (exposing margins or creating an unesthetic appearance). The correct sequence is to treat the gingivitis, establish excellent oral hygiene, and wait for the gingival tissues to become healthy and stable before proceeding with the cosmetic restorations.