MFDS Part 1 - Membership of Faculty of Dental Surgery Restorative and Adhesive Dentistry Questions and Answers

Question 1

In line with the UK's implementation of the Minamata Convention on Mercury, the use of dental amalgam is restricted. In which of the following patient groups is the use of dental amalgam prohibited, except where deemed strictly necessary by the practitioner for the specific medical needs of the patient?

Accepted Answer

Children under 15 years of age, and pregnant or breastfeeding women.

Answer

The Minamata Convention on Mercury is a global treaty to protect human health and the environment from mercury. In the UK, as in the EU, this has led to specific restrictions on the use of dental amalgam. From 1 July 2018, dental amalgam must not be used for the dental treatment of deciduous teeth, of children under 15 years, and of pregnant or breastfeeding women, unless there is a specific medical necessity.

Question 2

A dentist is preparing to permanently cement a lithium disilicate onlay. To achieve a strong and durable adhesive bond, what is the mandatory surface pre-treatment for the intaglio (fitting) surface of this specific type of ceramic restoration before applying a silane coupling agent?

Accepted Answer

Etching with approximately 5% hydrofluoric acid for 20 seconds.

Answer

Lithium disilicate is a silica-based ceramic. To create the micromechanical retention necessary for a strong adhesive bond, its fitting surface must be etched with hydrofluoric acid (HF). This process selectively dissolves the glassy matrix, creating a porous surface for the resin cement to penetrate. The typical manufacturer's recommendation for lithium disilicate (e.g., IPS e.max) is to use approximately 5% HF for 20 seconds. Phosphoric acid is ineffective, and sandblasting is the primary pre-treatment for zirconia, not lithium disilicate.

Question 3

A 24-year-old patient presents with a deep carious lesion in the mandibular first molar (LR6). The tooth is asymptomatic and responds normally to sensibility testing. A radiograph shows the lesion extending into the pulpal third of the dentine. According to contemporary minimally invasive dentistry principles widely accepted in the UK, what is the most appropriate management for the deepest part of the cavity?

Accepted Answer

Selective removal of caries to leave firm, leathery dentine in the pulpal aspect, having secured a peripheral seal on sound dentine.

Answer

Contemporary evidence supports selective caries removal to preserve pulp vitality in deep, asymptomatic lesions. The goal is to remove the outer, heavily infected and non-remineralisable dentine while preserving the deeper, affected but repairable dentine. This involves clearing the cavity walls and enamel-dentine junction to sound tissue to ensure an effective peripheral seal, but leaving firm or leathery dentine directly over the pulp to avoid iatrogenic exposure. Complete removal to hard dentine risks unnecessary pulp exposure, while leaving soft, wet dentine is not recommended.

Question 4

A conventional glass ionomer cement (GIC) is selected for a Class V restoration. Which of the following statements most accurately describes the primary bonding mechanism of this material to tooth structure?

Accepted Answer

It sets via an acid-base reaction and forms a true chemical bond through ionic exchange.

Answer

Conventional glass ionomer cements are self-adhesive materials. Their setting is an acid-base reaction between the polyalkenoic acid liquid and the basic fluoroaluminosilicate glass powder. Adhesion to the tooth occurs via a chemical bond, specifically an ionic exchange between the carboxyl groups of the polyacid and calcium ions in the hydroxyapatite of enamel and dentine.

Question 5

When planning a full coverage crown for a root-filled molar, which of the following factors is considered most critical for the long-term prognosis and fracture resistance of the tooth?

Accepted Answer

The presence of a circumferential ferrule of 1.5-2.0 mm of sound tooth structure.

Answer

The ferrule effect, which is a 360-degree collar of sound tooth structure coronal to the crown margin, is widely regarded as the most important determinant for the fracture resistance of a restored, root-filled tooth. A ferrule of at least 1.5-2.0 mm in height braces the tooth against functional forces, reducing stress on the post and within the root, thereby significantly improving the long-term prognosis. While other factors are important, the presence of an adequate ferrule is the most critical.

MFDS Part 1 Practice Test

MFDS Part 1 Practice Test

MFDS Part 1 - Membership of Faculty of Dental Surgery Restorative and Adhesive Dentistry Questions and Answers