ORE Part 1 Oral Biology & Pathology 3 — Questions and Answers
Question 1: What is the mechanism of action of fluoride in preventing dental caries?
- Fluoride incorporates into hydroxyapatite to form fluorapatite (more acid-resistant); enhances remineralisation; inhibits bacterial enzymes (Correct answer)
- Fluoride kills all oral bacteria
- Fluoride dissolves calculus deposits
- Fluoride strengthens enamel by increasing its thickness
Correct answer: Fluoride incorporates into hydroxyapatite to form fluorapatite (more acid-resistant); enhances remineralisation; inhibits bacterial enzymes
Fluoride's anti-caries effect is multi-factorial: (1) substitution into hydroxyapatite forming fluorapatite (acid-resistant), (2) enhancing remineralisation post-acid attack, and (3) inhibiting bacterial enolase enzymes reducing acid production.
Question 2: What is a 'radicular cyst' (periapical cyst) and what stimulates its formation?
- An inflammatory odontogenic cyst arising from the rests of Malassez, stimulated by inflammatory mediators from a non-vital infected tooth (Correct answer)
- A developmental cyst around an unerupted tooth
- A cyst arising from salivary gland tissue
- A traumatic cyst following tooth extraction
Correct answer: An inflammatory odontogenic cyst arising from the rests of Malassez, stimulated by inflammatory mediators from a non-vital infected tooth
The radicular (periapical) cyst is the most common odontogenic cyst overall. It develops from epithelial rests of Malassez in the PDL, stimulated to proliferate by inflammatory mediators from pulp infection/necrosis.
Question 3: What is the significance of 'dark zones' in enamel caries histology?
- Dark zones contain small pores filled with organic material and represent an area of remineralisation activity at the advancing front of early caries (Correct answer)
- Dark zones are the most demineralised, active destruction areas
- Dark zones represent bacterial invasion of enamel
- Dark zones are normal developmental features
Correct answer: Dark zones contain small pores filled with organic material and represent an area of remineralisation activity at the advancing front of early caries
In the histology of early enamel caries, the dark zone (beneath the translucent zone at the lesion front) shows small pores with remineralisation activity — it is a zone of repair. This underpins the concept of treating early lesions by remineralisation.
Question 4: What is 'amelogenesis imperfecta'?
- A hereditary condition affecting enamel formation causing hypoplasia, hypomineralisation, or hypomaturation — teeth affected throughout the dentition in both dentitions (Correct answer)
- A condition caused by fluoride excess only
- A form of dentine dysplasia
- Enamel dissolution caused by acid erosion
Correct answer: A hereditary condition affecting enamel formation causing hypoplasia, hypomineralisation, or hypomaturation — teeth affected throughout the dentition in both dentitions
Amelogenesis imperfecta (AI) is a group of hereditary conditions affecting enamel formation genes (AMELX, ENAM, MMP20 etc.). It causes enamel defects ranging from hypoplasia (thin) to hypomineralisation (soft/discoloured) affecting all teeth.
Question 5: What cells initiate the inflammatory response in gingivitis?
- Neutrophils and lymphocytes responding to bacterial biofilm products at the gingival margin (Correct answer)
- Osteoclasts at the alveolar crest
- Fibroblasts in the PDL
- Odontoblasts in the pulp
Correct answer: Neutrophils and lymphocytes responding to bacterial biofilm products at the gingival margin
Early gingivitis is characterised by neutrophil migration from the junctional epithelium vasculature in response to bacterial LPS and other virulence factors. Lymphocytes (T cells) accumulate in the established lesion.
Question 6: What is 'denture stomatitis' and what is its most common cause?
- Erythematous mucositis under a denture, most commonly caused by Candida albicans overgrowth facilitated by continuous denture wear and poor denture hygiene (Correct answer)
- A bacterial infection under dentures
- An allergic reaction to denture acrylic
- A viral infection specific to denture wearers
Correct answer: Erythematous mucositis under a denture, most commonly caused by Candida albicans overgrowth facilitated by continuous denture wear and poor denture hygiene
Denture stomatitis (Newton type I–III) is erythema under an upper denture, predominantly caused by Candida albicans overgrowth. Risk factors include continuous wear, poor denture hygiene, and dry mouth.
ORE Part 1 Oral Biology & Pathology 3
What is the mechanism of action of fluoride in preventing dental caries?