American Board of Prosthodontics (ABP) Section A Written Examination

Correct: The lingual nerve, a branch of the mandibular nerve (V3), passes into the sublingual space and is located in the soft tissues on the lingual aspect of the mandibular third molar. Anatomical studies indicate that the nerve is in close proximity to the lingual cortical plate and, in approximately 10-15% of individuals, it may actually be positioned superior to the alveolar crest. This makes it highly susceptible to damage during the reflection of lingual flaps, distal relieving incisions, or the use of lingual retractors.

Incorrect: The lingual nerve is not protected by the medial pterygoid muscle in the third molar region; it passes between the muscle and the ramus before moving medially toward the tongue. The nerve does not travel within the inferior alveolar canal; that is the path of the inferior alveolar nerve. Finally, the lingual nerve is located on the medial (lingual) side of the mandible, not the lateral (buccal) side, so it is not at risk during standard buccal suturing.

Takeaway: The lingual nerve’s variable position, often at or above the alveolar crest, requires careful surgical technique and flap management on the lingual aspect of the mandibular third molar to prevent neurosensory deficits.

Correct: Electric Pulp Testing (EPT) relies on the conduction of an electrical current through the tooth structure to stimulate the A-delta fibers at the pulp-dentin junction. Porcelain is an effective electrical insulator; therefore, placing an EPT probe on a porcelain surface will not complete the circuit to the pulp, leading to a false-negative result. Thermal testing (especially cold) is more reliable in these cases because the temperature change can be conducted through the restoration or applied to the cervical margin where natural tooth structure may be exposed.

Incorrect: Electric pulp testing measures sensibility (nerve response), not vitality (vascular supply). Porcelain has extremely high electrical resistance, not low resistance, making it an insulator rather than a conductor. EPT does not penetrate porcelain effectively. Furthermore, EPT is more likely to cause false positives if the current leaks to the gingiva or adjacent metallic restorations, rather than being used to avoid them.

Takeaway: Sensibility tests like EPT and thermal testing are limited by the conductive properties of restorative materials, with EPT being particularly ineffective when applied directly to insulating materials like porcelain.

Correct: Current clinical guidelines, such as those from the Scottish Dental Clinical Effectiveness Programme (SDCEP), recommend that for patients taking Direct Oral Anticoagulants (DOACs) like Rivaroxaban, minor oral surgery (including the extraction of up to three teeth) should be performed without interrupting the medication. The risk of a significant thromboembolic event (like a stroke) resulting from medication cessation is far more dangerous than the risk of a localized post-operative bleed, which can be effectively managed with local hemostatic agents (e.g., Surgicel) and primary closure with sutures. Scheduling the appointment early in the day allows the patient to return if delayed bleeding occurs.

Incorrect: Instructing a patient to omit a dose of a DOAC is generally discouraged for minor oral surgery as it increases the risk of thromboembolism without a significant reduction in clinically relevant bleeding. Bridging with low-molecular-weight heparin is a complex protocol typically reserved for high-risk patients on Warfarin, not DOACs, and DOACs do not require INR monitoring as they have a predictable pharmacodynamic profile. Transitioning a patient from a DOAC to Warfarin solely for a dental extraction is clinically inappropriate, increases systemic risk, and ignores the fact that DOACs are often preferred for their safety profile in atrial fibrillation.

Takeaway: For minor oral surgery in patients on stable anticoagulant therapy, local hemostatic measures are preferred over systemic medication adjustments to minimize the risk of life-threatening thromboembolic events.

Correct: Systemic antimicrobials are not a substitute for mechanical therapy because they cannot effectively penetrate the complex subgingival biofilm in the absence of physical disruption. Clinical guidelines specify that systemic antibiotics should only be used as an adjunct to scaling and root surface debridement (RSD), typically reserved for aggressive forms of the disease (Grade C) or specific conditions like necrotizing periodontitis where tissue invasion by pathogens is present.

Incorrect: Using antibiotics as a standalone therapy is clinically ineffective against biofilm and promotes antimicrobial resistance. Routine use for gingivitis is inappropriate as gingivitis is reversible through mechanical plaque control alone. Prophylactic use for all healthy adults during routine cleanings is not supported by current health guidelines and deviates from antimicrobial stewardship principles.

Takeaway: Systemic antimicrobials in periodontology are strictly adjuncts to mechanical debridement and are reserved for specific, severe, or rapidly progressing disease phenotypes to ensure clinical efficacy and stewardship.

Correct: For lesions larger than 1 cm or those exhibiting suspicious clinical features such as erythroleukoplakia, an incisional biopsy is the gold standard. It allows for the assessment of tissue architecture and the relationship between the lesion and normal tissue, which is vital for identifying invasive characteristics and providing a definitive diagnosis without compromising the site for future definitive surgery.

Incorrect: Excisional biopsy is generally reserved for small, clinically benign lesions; for larger suspicious lesions, it may compromise future management or result in inadequate margins if malignancy is confirmed. Cytological smears have high false-negative rates and do not provide the architectural information necessary for a definitive diagnosis of dysplasia or carcinoma. Sampling only the center of a lesion, especially if it is necrotic or hyperkeratotic, may not provide the most diagnostic cellular information often found at the advancing edge or the transition zone.

Takeaway: Incisional biopsy including a margin of healthy tissue is the definitive diagnostic step for large or clinically suspicious oral mucosal lesions to assess tissue architecture.

Correct: Motivational interviewing (MI) is a patient-centered, collaborative conversation style for strengthening a person’s own motivation and commitment to change. When a patient identifies a barrier such as a busy schedule or lack of perceived benefit, the clinician must move beyond didactic instruction. By exploring the patient’s own values and identifying specific obstacles, the clinician helps the patient develop internal motivation, which is more effective for long-term behavior change than simply repeating technical instructions.

Incorrect: Repeating or expanding mechanical demonstrations assumes the failure is due to a lack of knowledge or manual dexterity, which contradicts the patient’s stated issue of time and motivation. Using fear-based tactics regarding systemic health risks often results in defensive reactions or temporary compliance rather than sustained habit formation. Increasing the frequency of professional cleanings treats the clinical symptom of plaque accumulation but fails to address the behavioral root cause, potentially making the patient dependent on the clinician rather than taking ownership of their oral health.

Takeaway: Effective oral hygiene instruction requires a shift from a didactic, clinician-led approach to a collaborative, patient-centered dialogue that addresses individual barriers to behavior change.

Correct: In maxillary first molars, the MB2 canal is present in a high percentage of cases, often exceeding 70-90% in clinical and laboratory studies. Failure to locate, negotiate, and disinfect this canal allows bacteria to persist in the root canal system, which is the most common reason for the failure of initial endodontic therapy in these teeth. During retreatment, locating the MB2 is a primary objective to resolve the infection.

Incorrect: While accessory canals in the apical delta and lateral canals in the distobuccal root can harbor bacteria and contribute to failure, they are statistically less common as the primary cause of failure compared to a completely missed main canal like the MB2. C-shaped canals are an anatomical variation primarily associated with mandibular second molars and are extremely rare in maxillary first molars, making it an unlikely cause for failure in this scenario.

Takeaway: The most common anatomical cause for endodontic failure in maxillary first molars is the failure to identify and treat the second mesiobuccal canal (MB2).

Correct: In periodontal patients, nicotine’s vasoconstrictive properties suppress the inflammatory response, specifically bleeding on probing, which can lead to a false sense of health. The most appropriate clinical approach is to educate the patient on this masking effect to improve their understanding of the disease, followed by the evidence-based Very Brief Advice (VBA) model (Ask, Advise, Act). Referring to specialist services significantly increases the success rate of quit attempts compared to advice given in the dental chair alone.

Incorrect: Deferring periodontal treatment until a patient quits smoking is not recommended as it allows the disease to progress; treatment should be provided alongside cessation support. While aesthetics are a factor, they are secondary to the biological risks of tooth loss and bone destruction in Stage III periodontitis. Recommending electronic cigarettes as a primary cessation tool is not the standard of care for dental professionals, who should instead refer to evidence-based cessation services and approved pharmacotherapies.

Takeaway: Clinicians must explain how smoking masks periodontal symptoms and use the Very Brief Advice framework to refer patients to specialist cessation services for the best periodontal outcomes.

Correct: Relining is the indicated procedure when the framework of a Removable Partial Denture (RPD) fits the abutment teeth but the base has lost contact with the ridge due to resorption. In distal extension cases (Kennedy Class I and II), using a functional impression technique (such as the altered cast technique or functional reline materials) is critical. This ensures the base is adapted to the tissues in their functional, supportive state, which prevents the ‘rocking’ motion around the fulcrum line that otherwise stresses abutment teeth and causes instability.

Incorrect: Re-basing is an extensive laboratory process that replaces the entire acrylic base; it is generally reserved for cases where the base material is damaged, stained, or porous, rather than simple loss of fit. Adjusting clasps and rests addresses retention (resistance to vertical displacement) but does not address the loss of support (stability); over-tightening clasps without restoring base support can lead to excessive torque and mobility of the abutment teeth. Chairside hard relines often suffer from poor longevity, potential chemical irritation from the monomer, and the risk of inadvertently increasing the occlusal vertical dimension if the material is not managed correctly during the setting phase.

Takeaway: For distal extension RPDs experiencing ridge resorption, relining with a functional impression is the standard approach to restore stability and protect the health of the abutment teeth.

Correct: For monolithic zirconia restorations, a chamfer margin of approximately 0.5 mm is the gold standard. This design provides sufficient bulk for material strength at the margin while being more conservative of tooth structure compared to shoulder preparations. Placing the margin at the gingival crest or supragingivally facilitates easier impression taking, better moisture control during cementation, and superior long-term periodontal health by allowing for easier plaque removal.

Incorrect: A 1.5 mm shoulder is unnecessarily aggressive for monolithic zirconia and is typically reserved for porcelain-fused-to-metal (PFM) or traditional glass-ceramic crowns; furthermore, bevels are contraindicated for ceramic materials as they result in thin, fragile edges prone to chipping. Feather-edge margins are generally avoided because they do not provide a distinct finish line for the laboratory technician, often resulting in over-contoured restorations that trap plaque. Placing a margin 1.0 mm apical to the sulcus risks violating the biological width (junctional epithelium and supracrestal connective tissue), which leads to chronic inflammation and potential bone resorption.

Takeaway: The selection of margin design must balance the minimum thickness requirements of the restorative material with the biological necessity of preserving tooth structure and maintaining the integrity of the periodontium.