Accreditation Written Examination Practice Questions

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.

The incisal 'halo' is a bright, whitish line seen at the very incisal edge of unworn anterior teeth. It is created by the anatomical structure of the enamel rods being oriented perpendicular to the incisal edge surface. This orientation causes the light that enters the tooth to be scattered, creating an optical effect of a higher value, opaque line right at the edge, framed by the translucency of the facial and lingual enamel surfaces. A ceramist replicates this by using a small amount of high-value, opaque porcelain at the incisal edge.

A successful intraoral repair requires proper surface treatment for each substrate. The correct sequence is: 1) Microetch (air abrade) both the exposed metal and the fractured porcelain to increase surface area and clean the surfaces. 2) Apply a silane coupling agent to the porcelain surface to chemically bond the resin. 3) Apply an opaque resin layer over the metal substructure to block its color and bond to it (often via a metal primer within the opaque resin system). 4) Apply a universal bonding agent over all prepared surfaces. 5) Layer the final restorative composite. Using hydrofluoric acid without proper isolation is hazardous, and failing to use an opaquer will result in a gray show-through from the metal.

A 'lifeless' appearance in a technically correct shade is often due to a lack of natural optical effects. Opalescent porcelains, which appear bluish in reflected light and reddish-orange in transmitted light, mimic the natural opalescence of enamel, especially in the incisal third. Translucent effect porcelains replicate the transparency of enamel between the mamelons. Adding these characterizations breaks up the light in a more natural way, creating depth and vitality that a monolithic shade cannot achieve.

The success of long-term provisionals hinges on a meticulous 'shrink-wrap' fit and finish. After initial fabrication, all excess material (flash) must be removed, especially in the interproximal and cervical areas. The embrasures must be carefully opened and shaped to allow for proper oral hygiene (flossing). Finally, all surfaces and margins must be highly polished. This process prevents plaque accumulation, promotes gingival health, and creates a smooth, stain-resistant surface that mimics the final restorations, satisfying the patient's high esthetic demands. The choice of material viscosity or cement thickness is secondary to the final contouring and polishing.

The core issue is the incorrect axial position of the posterior teeth, not just their surface contour. Orthodontic treatment is the most biologically sound and comprehensive solution to physically move the teeth into the correct position, thereby filling the buccal corridor naturally. While veneers can add buccal volume, they cannot correct the underlying axial inclination and may lead to bulky, unhygienic restorations if the problem is severe. Direct bonding is a temporary and less durable solution. Simply whitening teeth does not address the spatial issue.

With translucent ceramics like feldspathic porcelain, the final shade is a combination of the underlying tooth structure, the cement, and the veneer itself. To significantly shift the shade from A3.5 to A1, the resin cement must have sufficient opacity to block out the dark underlying tooth color while also contributing to the lighter target shade. Using a shaded and opaque try-in paste and corresponding cement is essential for a predictable esthetic outcome. Bond strength, cement thickness, and cure type are important for longevity but do not primarily control the final shade modification.

Restoring a lost VDO is a complex process that requires careful verification. The most predictable and reversible method is to use a diagnostic tool like a removable acrylic splint or provisional restorations. This allows the patient to function at the new VDO for several weeks, enabling the clinician to assess phonetics (e.g., 'S' sounds), comfort of the masticatory muscles, and TMJ health. This trial period confirms the appropriateness of the new VDO before committing to definitive restorations. Relying solely on facial proportions, arbitrary measurements, or phonetics alone is not sufficient and can lead to failure.