MJDF Clinical Dentistry — Questions and Answers
Question 1: A patient presents with a deep carious lesion on a lower first molar with symptoms of reversible pulpitis. What is the most appropriate treatment approach?
- Immediate root canal treatment
- Stepwise excavation or selective caries removal to avoid pulp exposure, followed by placement of a well-sealed restoration (Correct answer)
- Extraction and replacement with an implant
- Prescribe antibiotics and review in one month
Correct answer: Stepwise excavation or selective caries removal to avoid pulp exposure, followed by placement of a well-sealed restoration
For deep carious lesions with reversible pulpitis, current evidence supports selective (incomplete) caries removal or stepwise excavation to avoid pulp exposure. Complete excavation of all carious dentine in deep lesions carries a high risk of pulp exposure. By leaving affected (but not infected) dentine over the pulp and sealing the cavity with a well-bonded restoration, the pulp can recover and produce reactionary dentine. This approach has shown higher success rates in maintaining pulp vitality than complete excavation.
Question 2: When assessing a patient for a fixed dental prosthesis (bridge), what is Ante's Law and what is its clinical significance?
- It states that the number of pontics must equal the number of abutments
- It states that the total periodontal ligament area of the abutment teeth should be equal to or greater than that of the teeth being replaced — it helps determine whether abutment teeth can support the bridge (Correct answer)
- It determines the shade selection for the bridge
- It specifies the minimum connector dimensions for a bridge
Correct answer: It states that the total periodontal ligament area of the abutment teeth should be equal to or greater than that of the teeth being replaced — it helps determine whether abutment teeth can support the bridge
Ante's Law (1926) states that the total root surface area (periodontal ligament area) of the abutment teeth must be equal to or exceed that of the teeth to be replaced by pontics. This ensures the abutment teeth can support the additional occlusal load. While widely taught, it is considered a general guideline rather than an absolute rule — clinical factors such as crown-to-root ratio, bone support, occlusion, and abutment tooth condition also influence treatment planning.
Question 3: What are the essential features of an ideal Class II cavity preparation for a composite resin restoration?
- Flat floor, undercuts for retention, 90-degree cavosurface angles, and maximum extension
- Conservative preparation following the extent of caries, rounded internal line angles, enamel bevels at the occlusal margin (no bevel gingivally), adequate access for placement and curing, and a clear gingival margin for matrix adaptation (Correct answer)
- No cavity preparation is needed — composite bonds to any surface
- Sharp internal line angles, dovetail retention, and extension for prevention to all fissures
Correct answer: Conservative preparation following the extent of caries, rounded internal line angles, enamel bevels at the occlusal margin (no bevel gingivally), adequate access for placement and curing, and a clear gingival margin for matrix adaptation
Modern Class II composite preparations differ from traditional amalgam preparations: they follow the caries extent conservatively (minimal intervention), have rounded internal line angles (reduces stress concentration), feature enamel bevels occlusally (increases enamel bonding surface area) but NOT at the gingival margin (thin composite fractures), require adequate access for incremental placement and light curing, and need a clear, well-adapted matrix band at the gingival margin for a tight proximal contact. Extension for prevention and mechanical retention features are unnecessary with adhesive restorations.
Question 4: A patient presents with localised aggressive periodontitis affecting the first molars and incisors in a 22-year-old. What microorganism is most commonly associated with this condition?
- Streptococcus mutans
- Aggregatibacter actinomycetemcomitans (Correct answer)
- Candida albicans
- Staphylococcus aureus
Correct answer: Aggregatibacter actinomycetemcomitans
Aggregatibacter actinomycetemcomitans (formerly Actinobacillus actinomycetemcomitans) is the microorganism most strongly associated with localised aggressive periodontitis (now classified as 'periodontitis' Grade C, Molar-Incisor Pattern under the 2017 classification). It produces leukotoxin that destroys neutrophils, collagenase, and other virulence factors. The condition characteristically affects first permanent molars and incisors in otherwise healthy young adults, with rapid bone loss disproportionate to the amount of plaque present.
Question 5: What is the difference between a removable partial denture designed with a bounded saddle versus a free-end saddle, and how does this affect support?
- There is no clinical difference between bounded and free-end saddles
- A bounded saddle has abutment teeth on both sides of the edentulous span (tooth-supported); a free-end saddle extends distally with no posterior abutment (mucosa-supported distally), requiring careful consideration of support, retention, and path of insertion to manage differential tissue support (Correct answer)
- A free-end saddle is always contraindicated in partial denture design
- Bounded saddles require implants for support; free-end saddles do not
Correct answer: A bounded saddle has abutment teeth on both sides of the edentulous span (tooth-supported); a free-end saddle extends distally with no posterior abutment (mucosa-supported distally), requiring careful consideration of support, retention, and path of insertion to manage differential tissue support
A bounded saddle has natural teeth on both sides, providing tooth support at each end via rests. A free-end (distal extension) saddle has no distal abutment, so the saddle base rests on mucosa which is more compressible than the periodontal ligament. This differential support creates biomechanical challenges: the saddle tends to rotate around the last abutment under occlusal load. Design features to manage this include mesial rests (rather than distal), RPI (rest-plate-I bar) clasp systems, and altered cast techniques for optimal mucosal fit.
Question 6: During root canal treatment, sodium hypochlorite is the most widely used irrigant. What are its properties and the main risk associated with its use?
- It is a mild antiseptic with no significant risks
- It dissolves organic tissue (necrotic pulp and biofilm), has a broad antimicrobial spectrum, and lubricates the canal; the main risk is extrusion beyond the apex causing severe tissue damage, pain, swelling, and potentially paraesthesia (Correct answer)
- It only removes the smear layer and has no antimicrobial properties
- It is used solely to lubricate the files and has no chemical action
Correct answer: It dissolves organic tissue (necrotic pulp and biofilm), has a broad antimicrobial spectrum, and lubricates the canal; the main risk is extrusion beyond the apex causing severe tissue damage, pain, swelling, and potentially paraesthesia
Sodium hypochlorite (NaOCl, typically 1-5.25%) is the gold standard endodontic irrigant due to its unique ability to dissolve organic tissue (necrotic pulp, biofilm matrix), its broad-spectrum antimicrobial activity (including against Enterococcus faecalis in biofilms), and its lubricating effect. The main risk is extrusion beyond the apical foramen, causing a 'sodium hypochlorite accident' with severe pain, rapid swelling, ecchymosis, possible tissue necrosis, and paraesthesia. Prevention requires correct working length, passive irrigation with side-vented needles, and avoiding wedging the needle in the canal.
MJDF Clinical Dentistry
A patient presents with a deep carious lesion on a lower first molar with symptoms of reversible pulpitis.
What is the most appropriate treatment approach?