ADC - Australian Dental Council Prosthodontics and Dental Implants Questions and Answers

Question 1

A 55-year-old patient requires a full coverage crown for tooth 25, which has had root canal treatment and a large MOD amalgam restoration. Clinical examination reveals 1.5mm of sound coronal tooth structure above the gingival margin circumferentially. What is the most critical factor for the long-term fracture resistance of the final restoration?

Accepted Answer

Achieving an adequate ferrule effect.

Answer

The ferrule effect, which is the 360-degree collar of a crown encircling the parallel walls of sound dentine, is crucial for protecting a root-treated tooth from fracture. A minimum of 1.5-2mm of ferrule height is widely recommended to provide a bracing action that resists functional lever forces and dissipates occlusal stresses. While other factors like cement and post material are important, the ferrule is considered the most critical structural feature for improving fracture resistance and long-term prognosis.

Question 2

When taking a final impression for multiple, non-parallel implants intended for a splinted, screw-retained bridge, which technique is generally considered more accurate for capturing the precise three-dimensional orientation of the implants?

Accepted Answer

Open-tray impression technique.

Answer

The open-tray (or pick-up) technique is generally more accurate for multiple, angulated (non-parallel) implants. The impression copings are directly connected to the impression material and are unscrewed from the implants while the tray is still in the mouth. This method minimizes errors from the potential malpositioning of copings when re-seating them into the impression, which is a risk with the closed-tray (transfer) technique, especially where implant angulation prevents a clear path of insertion.

Question 3

A 72-year-old patient received new complete maxillary and mandibular dentures one week ago. They return complaining that the lower denture lifts every time they move their tongue. Which of the following is the most likely cause?

Accepted Answer

The mandibular lingual flanges are overextended.

Answer

Overextension of the lingual flanges of a mandibular complete denture will impinge on the mylohyoid muscle and the floor of the mouth. When the patient lifts or moves their tongue, these muscles contract and dislodge the denture. An inadequate posterior palatal seal affects the maxillary denture, and incorrect vertical dimension or tooth position typically causes different issues like muscle fatigue or cheek biting.

Question 4

Which of the following is the primary function of a major connector in a mandibular removable partial denture?

Accepted Answer

To unite all components and distribute forces across the arch.

Answer

The primary function of a major connector (e.g., lingual bar or plate) is to provide rigidity and unite all other components of the RPD on one side of the arch with those on the other. This unification allows for the effective distribution of functional stresses to the supporting teeth and tissues, providing cross-arch stability and preventing the overloading of any single area.

Question 5

A 60-year-old patient with an implant-supported crown on tooth 46, placed 5 years ago, presents for a routine check-up. Probing around the implant reveals a 6mm pocket with bleeding on probing. What is the most crucial additional diagnostic information required to differentiate between peri-mucositis and peri-implantitis?

Accepted Answer

Comparison with a baseline radiograph.

Answer

The key feature that distinguishes peri-implantitis from peri-mucositis is radiographic evidence of progressive bone loss beyond initial remodelling. Peri-mucositis is inflammation confined to the soft tissues without bone loss. While bleeding on probing indicates inflammation (present in both) and suppuration is a strong sign of infection, the definitive diagnosis of peri-implantitis requires confirmation of bone loss by comparing current radiographs to baseline or previous radiographs.

ADC - Australian Dental Council Practice Test

ADC - Australian Dental Council Practice Test

ADC - Australian Dental Council Prosthodontics and Dental Implants Questions and Answers