Medical History in Dentistry: Assessment, Risk Stratification, and Treatment Modification
ASA Classification · Drug Interactions · High-Risk Conditions · Treatment Modification
TL;DR
Medical history-taking is the cornerstone of safe dental practice. It identifies patient risk factors, guides treatment modification, prevents medical emergencies, reveals drug interactions, and forms the basis of the medicolegal record. Every new patient requires a comprehensive written medical history; all patients require an updated medical history at each visit. The ASA Physical Status Classification is the internationally accepted system for pre-procedure risk stratification in dentistry and medicine.
- The ASA Physical Status Classification stratifies patient risk from ASA I (normal healthy patient) to ASA VI (brain-dead organ donor) — dental practice typically manages ASA I–III patients, with ASA IV requiring specialist or hospital referral: The ASA classification (American Society of Anesthesiologists Physical Status Classification System) was originally designed for surgical anaesthetic risk assessment but is widely used in dentistry. ASA I: normal healthy patient — no systemic disease; no smoking; no or minimal alcohol use. ASA II: patient with mild systemic disease — well-controlled type 2 diabetes; mild hypertension (SBP <160/DBP <100); mild obesity (BMI 30–40); well-controlled epilepsy; non-smoking asthma; social alcohol use; pregnancy. ASA III: patient with severe systemic disease — poorly controlled type 2 diabetes or type 1 diabetes with complications; morbid obesity (BMI >40); active hepatitis; alcohol dependence; history of MI, CVA, or TIA >3 months ago; well-controlled COPD. ASA IV: patient with severe systemic disease that is a constant threat to life — recent AMI or stroke (<3 months); severe COPD; poorly controlled congestive heart failure; end-stage renal disease on dialysis. ASA V: moribund patient not expected to survive without the operation. ASA VI: declared brain-dead patient for organ donation. For dental board examinations, the key thresholds are: ASA III in general practice (proceed with care, modification, consultation); ASA IV refers to specialist or hospital dentistry.
- Patients on warfarin undergoing simple dental extractions should NOT have their anticoagulation stopped — extractions can be performed safely with INR ≤3.5 using local haemostatic measures: Current guidelines from the British Society for Haematology, the Scottish Dental Clinical Effectiveness Programme (SDCEP), and the ADA all agree that warfarin should not be stopped before dental extractions. The risk of thromboembolic events (stroke, DVT, pulmonary embolism, prosthetic valve thrombosis) from stopping anticoagulation exceeds the risk of haemorrhage from dental extraction when local haemostatic measures are used. Safe dental extraction protocol: (1) Check INR within 72 hours pre-operatively — if INR ≤3.5, proceed; if INR >3.5, liaise with the anticoagulation clinic (do not adjust warfarin yourself); (2) Use local haemostatic measures: oxidised cellulose (Surgicel), tranexamic acid 5% mouthwash (10mL, swish for 2 minutes and spit, 4× daily for 5 days), absorbable gelatin sponge (Gelfoam), or resorbable sutures; (3) Avoid NSAIDs (displace warfarin from protein binding, enhance anticoagulant effect); (4) Avoid erythromycin, metronidazole, and fluconazole (inhibit CYP2C9 → raise INR). DOACs (direct oral anticoagulants — apixaban, rivaroxaban, dabigatran, edoxaban): for simple extractions, most guidelines now recommend taking the morning DOAC dose after the procedure rather than stopping it (timing-based approach). For major oral surgery, specialist liaison is required.
- Adrenaline (epinephrine) in local anaesthetics can safely be used in patients with controlled cardiovascular disease — the systemic dose from dental anaesthesia is lower than endogenous adrenaline released by anxiety and pain: The maximum recommended dose of epinephrine in patients with cardiovascular disease (angina, controlled hypertension, previous MI) is 0.04mg per appointment — equivalent to 2 cartridges of 1:80,000 epinephrine or 4 cartridges of 1:100,000 epinephrine. In a healthy patient, the limit is 0.2mg per appointment (10 cartridges of 1:100,000). The rationale: epinephrine in LA provides profound anaesthesia, reducing the need for repeated injections, and reducing the pain response — which itself releases significant endogenous epinephrine. Anxiety and pain in an unanesthetised dental patient generate far more epinephrine than the controlled amount in 2 LA cartridges. Epinephrine is NOT contraindicated in patients with well-controlled hypertension or stable angina. Epinephrine IS effectively contraindicated in: uncontrolled hypertension (SBP >180); recent MI (<6 months); unstable or refractory angina; severe arrhythmia; and patients on non-selective beta-blockers (propranolol — additive pressor effect via unopposed alpha-receptor stimulation).
- Patients on bisphosphonate therapy (oral or IV) are at risk of MRONJ — this risk must be assessed before any oral surgical procedure involving bone: Medication-related osteonecrosis of the jaw (MRONJ) is exposed necrotic bone in the jaw that fails to heal within 8 weeks in a patient who has received anti-resorptive or anti-angiogenic therapy. Bisphosphonates (alendronate, risedronate, zoledronic acid, pamidronate) and denosumab inhibit osteoclast activity — in the jaws, where bone is subjected to trauma (extractions, implant placement) and oral bacterial contamination, reduced osteoclast remodelling leads to avascular necrosis. Risk stratification: oral bisphosphonates for osteoporosis (<3–5 years, no steroids) — low risk; dental extraction can proceed with informed consent and preventive measures (pre-extraction good oral hygiene, chlorhexidine rinse, atraumatic extraction, primary closure, no periosteal stripping). Oral bisphosphonates (>4 years) or with concurrent steroids — higher risk; consider drug holiday (consult prescribing physician — may cease bisphosphonate 2 months before and resume 3 months after if systemic condition allows). IV bisphosphonates (cancer patients — zoledronic acid, pamidronate) — HIGH risk (MRONJ incidence up to 6–10% after dental extraction) — specialist management; extract only if absolutely essential; consider conservative management (antibiotics, debridement) over extraction if viable.
- Pregnancy modifies dental treatment planning throughout all trimesters — the safest window for elective dental treatment is the second trimester (weeks 14–28): Pregnancy is associated with: gingivitis (pregnancy epulis — pyogenic granuloma on the gingival margin from progesterone effect on capillary permeability — bleeds easily; resolves after delivery in most cases); increased dental caries risk (dietary change, acid reflux, morning sickness); and dry mouth. Treatment considerations: first trimester (weeks 1–12) — avoid elective procedures where possible (organogenesis; morning sickness); emergency treatment only. Second trimester (weeks 14–28) — safest window for elective dental treatment; local anaesthesia is safe; no general anaesthetic without obstetric liaison. Third trimester (weeks 28–40) — avoid elective treatment after week 28; supine hypotensive syndrome (aortocaval compression by the gravid uterus in the supine position → hypotension and syncope — tilt the dental chair slightly to the left or place a wedge under the right hip to relieve IVC compression). Drug safety in pregnancy: lidocaine (Class B — safe); articaine (limited data — generally used cautiously); epinephrine (safe in dental doses — avoid prolonged supraperiosteal injection near uterine vasculature — theoretical risk); amoxicillin and metronidazole are considered safe. Avoid: tetracyclines (enamel hypoplasia, bone growth inhibition); metronidazole in first trimester (some data suggesting teratogenicity — use with caution); NSAIDs in third trimester (premature closure of ductus arteriosus).
Key Facts
What Is Medical History?
Medical history-taking in dentistry is the systematic process of identifying a patient’s current and past medical conditions, medications, allergies, and social history — all of which have the potential to affect dental treatment planning, drug prescribing, anaesthetic choices, and the risk of adverse events. It is a legal requirement in most jurisdictions and an ethical obligation in all. A medical history must be: current (obtained at every visit and updated — conditions and medications change); comprehensive (covering all body systems, not just “relevant” conditions); documented (signed and dated — the patient confirms the information); and acted upon (not merely collected — the clinician must review the history and modify treatment accordingly).
Why It Matters
Board examinations test medical history through clinical scenario questions: a patient with a heart murmur requires extraction — what antibiotic prophylaxis, if any, is required? A patient takes warfarin — can you extract teeth, and what precautions are necessary? A patient on metformin is scheduled for IV contrast — what drug interaction must be addressed? A patient on clindamycin develops profuse diarrhoea — what is the diagnosis? A pregnant patient in the third trimester needs emergency dental treatment — what position is required and what drugs are safe? These questions test the application of medical knowledge to clinical dentistry.
ASA Physical Status Classification
The ASA classification provides a standardised, objective language for communicating patient risk across the dental team and with medical colleagues. It guides the decision of whether dental treatment can be performed safely in a general dental practice setting, whether specialist referral is required, and whether hospital-based dental treatment under general anaesthesia is indicated.
| ASA Class | Definition | Dental Examples | Dental Management |
|---|---|---|---|
| ASA I | Normal healthy patient | No medical problems; non-smoker; minimal alcohol | Routine dental treatment — no modification |
| ASA II | Mild systemic disease | Well-controlled HTN; controlled DM2; mild asthma; current smoker; pregnancy; BMI 30–40; well-controlled epilepsy | Routine dental treatment with awareness — minimal modification; anxiety management may be beneficial |
| ASA III | Severe systemic disease | Poorly controlled DM; DM1 with complications; prior MI/CVA (>3 months); class I–II angina; morbid obesity; alcohol dependence; active hepatitis; COPD | Treat in general practice with modification; short morning appointments; medical liaison if needed; anxiety management; careful monitoring |
| ASA IV | Severe systemic disease, constant threat to life | Recent MI/CVA (<3 months); class III–IV angina; severe COPD; decompensated HF; end-stage renal failure on dialysis; hepatic failure | Refer to specialist / hospital dentistry. Emergency treatment only in general practice — only to relieve pain. |
| ASA V | Moribund, not expected to survive 24h without operation | Ruptured aortic aneurysm; massive trauma; multiorgan failure | Emergency treatment only in hospital setting |
| ASA VI | Brain-dead for organ donation | N/A in clinical dental context | N/A |
Key Medical Conditions and Dental Management
Cardiovascular Disease
Hypertension: Record BP before treatment. SBP >180 or DBP >110 → defer elective treatment; refer to GP for review. SBP 160–179 or DBP 100–109 → proceed with caution; short appointments; adequate pain control; epinephrine limit 0.04mg. Infective endocarditis (IE) prophylaxis: The 2007 NICE guidance (UK) and 2008 AHA guidelines removed routine antibiotic prophylaxis for most cardiac conditions. Antibiotic prophylaxis is NOW recommended only for: patients with prosthetic cardiac valves or prosthetic material used for cardiac valve repair; patients with a previous episode of IE; patients with certain types of congenital heart disease (unrepaired cyanotic CHD; repaired CHD with residual defect; first 6 months after complete repair). Standard UK prophylaxis: amoxicillin 3g orally 1 hour before (or clindamycin 600mg if penicillin allergic). Pacemakers and ICDs: Avoid ultrasonic scalers and electrosurgery/diathermy on these patients — electromagnetic interference risk (bipolar electrosurgery is safer than monopolar). Defibrillators should not be placed over or near ICDs.
Diabetes Mellitus
Diabetes affects oral health profoundly (increased periodontal disease severity; impaired wound healing; dry mouth from medication; candidiasis susceptibility) and dental treatment affects diabetes (infection raises blood glucose; stress raises blood glucose). Key dental considerations: morning appointments (blood glucose more stable; patient will have eaten breakfast); short appointments; ensure patient has eaten and taken medication; have glucose gel/tablets available; monitor for hypoglycaemia throughout appointment. HbA1c <8% = well-controlled (ASA II); HbA1c 8–9% = moderately controlled (ASA III); HbA1c >9% = poorly controlled (ASA III–IV) — elective surgery should be deferred. Impaired wound healing in poorly controlled diabetes: extractions, implants, and periodontal surgery carry higher risk of infection and delayed healing — perioperative antibiotic cover may be considered. Metformin and iodinated IV contrast media: metformin must be stopped 48 hours before IV iodinated contrast (e.g., for CT with contrast) — contrast can cause acute kidney injury → metformin accumulates → lactic acidosis. Not directly a dental issue but commonly tested in the board context of drug interactions.
Anticoagulant and Antiplatelet Therapy
| Drug / Class | Mechanism | Monitoring | Dental Extraction Management | Key Interactions |
|---|---|---|---|---|
| Warfarin | Vitamin K antagonist (inhibits factors II, VII, IX, X) | INR (target 2–3 for AF; 2.5–3.5 for mechanical valves) | Do NOT stop. Check INR ≤3.5 within 72h. Local haemostasis (tranexamic acid mouthwash, Surgicel, Gelfoam, resorbable sutures). | Metronidazole, erythromycin, fluconazole, NSAIDs all raise INR. Avoid. |
| Apixaban (Eliquis) | Direct factor Xa inhibitor | No routine monitoring | Take morning dose after extraction (simple). Major surgery: specialist liaison. | Azole antifungals (fluconazole): increase apixaban levels. Avoid. |
| Rivaroxaban (Xarelto) | Direct factor Xa inhibitor | No routine monitoring | Take morning dose after extraction (simple). Major surgery: specialist liaison. | Same as apixaban. Clarithromycin/erythromycin increase levels. |
| Dabigatran (Pradaxa) | Direct thrombin inhibitor | No routine monitoring | Take morning dose after extraction. Renal function monitoring important (renally excreted — impairment raises levels). | Clarithromycin significantly raises dabigatran levels. Avoid. |
| Aspirin 75–150mg | Irreversible COX-1 inhibitor → inhibits TXA2 platelet aggregation | No monitoring | Do NOT stop for simple extractions. Increased oozing — local haemostasis. | NSAIDs displace aspirin; combined antiplatelet + NSAID = higher GI bleed risk. |
| Clopidogrel (Plavix) | P2Y12 ADP receptor antagonist — irreversible platelet inhibition | No monitoring | Do NOT stop for simple extractions. Major surgery: specialist liaison. | Omeprazole reduces clopidogrel activation (CYP2C19 inhibition). PPIs should be switched if clopidogrel is used. |
Corticosteroid Therapy
Long-term systemic corticosteroid use (>5mg prednisolone/day for >1 month) causes HPA axis suppression and adrenal atrophy. The patient cannot mount an adequate cortisol stress response to surgery, infection, or significant psychological stress. Threshold for supplementation: most current guidelines state that additional steroid supplementation (“steroid cover”) is NOT routinely required for dental procedures performed under local anaesthesia — the physiological stress is manageable for most patients on stable doses. For major oral surgery under GA or significant surgical stress: double the morning dose on the day of surgery. For patients who are nil-by-mouth for GA: IV hydrocortisone is given perioperatively. Additionally, patients on high-dose long-term steroids are at risk of: candidiasis (steroid inhaler users — rinse mouth after use); impaired wound healing; increased susceptibility to infection; adrenal crisis (if steroid dose is missed perioperatively or under significant additional stress).
Bisphosphonates and MRONJ
MRONJ risk factors: route of administration (IV >> oral); dose and duration; indication (cancer treatment > osteoporosis); concurrent steroids (significantly increase risk); poor oral hygiene; dentoalveolar surgery (extraction, implant placement). Prevention: dental assessment and treatment completion before IV bisphosphonate therapy begins (teeth of poor prognosis should be extracted before starting IV bisphosphonates — once therapy has started, extractions carry high MRONJ risk). If a patient on IV bisphosphonates needs a dental extraction: conservative non-surgical management preferred where possible; if extraction essential — atraumatic technique; primary closure; perioperative antibiotics; chlorhexidine rinses; no periosteal stripping.
Pregnancy
Dental radiographs during pregnancy: can be taken when clinically necessary — the radiation dose from dental X-rays (particularly with modern digital sensors and lead apron) is negligible. A periapical radiograph delivers approximately 0.01 mGy — well below any threshold for teratogenic risk. Dental infections during pregnancy should be treated promptly — untreated dental infection carries higher risk to the foetus than dental treatment. The thyroid lead collar should be used in addition to the standard lead apron for all dental radiographs during pregnancy. Oral health changes in pregnancy: gingivitis affects up to 70–100% of pregnant patients; third-trimester discomfort from the supine dental position; increased caries risk from dietary change and acid reflux; pyogenic granuloma (pregnancy epulis) on the gingival margin.
Renal and Hepatic Disease
Renal disease: Impaired renal function reduces drug excretion — drugs that are renally excreted accumulate. Dental relevance: NSAIDs are nephrotoxic and contraindicated in moderate-to-severe renal failure; metronidazole dose adjustment in severe renal failure; dabigatran accumulates in renal impairment (direct thrombin inhibitor — renally cleared). Patients on renal dialysis: treat on non-dialysis days (heparin given during dialysis → bleeding risk on dialysis day); risk of infective endocarditis from vascular access; anaemia and bleeding tendency from platelet dysfunction (uraemia). Hepatic disease: The liver synthesises clotting factors (II, V, VII, IX, X, fibrinogen) and metabolises most drugs. Severe liver disease causes: coagulopathy (elevated PT/INR from reduced clotting factor synthesis); thrombocytopaenia (portal hypertension → splenic sequestration); impaired drug metabolism (LA toxicity risk elevated — lidocaine is hepatically metabolised; accumulation in severe liver failure). Avoid NSAIDs (reduced prostaglandin production → gastric mucosal damage + renal blood flow impairment). Paracetamol (acetaminophen) is hepatotoxic in overdose and in alcoholic liver disease — use with caution at standard doses.
Immunosuppression
Immunosuppressed patients (organ transplant recipients on cyclosporin, tacrolimus; chemotherapy patients; HIV/AIDS with CD4 <200; patients on biologic therapies) have impaired immune responses — dental infections may progress rapidly and atypically, and opportunistic organisms (Candida, herpes, unusual bacteria) may cause oral disease. Cyclosporin causes gingival hyperplasia (drug-induced gingival overgrowth — along with calcium channel blockers [amlodipine, nifedipine] and phenytoin). Drug interactions: azithromycin and fluconazole significantly raise cyclosporin levels (CYP3A4 inhibition) — avoid or use with specialist liaison. HIV: current antiretroviral therapy (ART) has normalised the oral manifestations of HIV for most patients in developed countries — major opportunistic infections (oral hairy leukoplakia, Kaposi’s sarcoma, acute necrotising ulcerative gingivitis in the immunosuppressed) are now rare in patients with controlled HIV on ART.
Key Drug Interactions for Dental Prescribing
| Dental Drug | Interacting Drug | Mechanism | Effect | Management |
|---|---|---|---|---|
| Metronidazole | Warfarin | CYP2C9 inhibition → reduced warfarin metabolism | Raised INR → bleeding risk | Avoid; or monitor INR closely; warn patient |
| Erythromycin / Clarithromycin | Warfarin, DOACs, statins, cyclosporin | CYP3A4 inhibition → reduced metabolism of multiple drugs | Raised drug levels → toxicity (statin myopathy, cyclosporin nephrotoxicity) | Prefer amoxicillin or clindamycin over macrolides in these patients |
| NSAIDs (ibuprofen, diclofenac) | Warfarin, aspirin, lithium, ACE inhibitors/diuretics, methotrexate | Protein displacement (warfarin); synergistic antiplatelet; reduced renal prostaglandins (lithium excretion ↓, ACE inhibitor failure, methotrexate toxicity) | Bleeding risk; hypertensive crisis; lithium toxicity; acute kidney injury; methotrexate toxicity | Avoid NSAIDs in patients on warfarin, lithium, methotrexate. Use paracetamol as first-line analgesic instead. |
| Epinephrine in LA | Non-selective beta-blockers (propranolol, nadolol) | Beta-2 receptors blocked → unopposed alpha stimulation from epinephrine | Hypertensive response + reflex bradycardia | Limit epinephrine to 0.04mg; use cardioselective beta-blockers are less of a concern |
| Epinephrine in LA | Tricyclic antidepressants (amitriptyline) | Inhibit norepinephrine reuptake → epinephrine-like effects potentiated | Exaggerated cardiovascular response to epinephrine | Limit epinephrine to 0.04mg (same as cardiovascular patients) |
| Fluconazole (antifungal) | Warfarin, apixaban, rivaroxaban, cyclosporin | Potent CYP2C9 and CYP3A4 inhibitor → reduced drug metabolism | Raised drug levels | Avoid fluconazole in patients on warfarin/DOACs/cyclosporin — use topical antifungal (miconazole gel, nystatin) preferentially |
| Clindamycin | Neuromuscular blocking agents | Potentiates neuromuscular blockade | Prolonged paralysis (anaesthesia context) | Inform anaesthetist if prescribing clindamycin perioperatively |
Local Anaesthesia Implications
The medical history directly determines the choice of local anaesthetic agent, the type and concentration of vasoconstrictor, and the maximum dose permitted. Key conditions affecting LA choice: Methaemoglobinaemia or G6PD deficiency: prilocaine and benzocaine cause methaemoglobinaemia — avoid; use lidocaine or articaine. Sulphite allergy: LA cartridges containing epinephrine include sodium metabisulphite as antioxidant — patients with sulphite allergy (particularly severe asthma patients with aspirin sensitivity — Samter’s triad) may react to the sulphite preservative rather than the LA itself. Use plain LA (without vasoconstrictor) or articaine (which uses different stabilisers) after allergy investigation. Cocaine use: epinephrine-containing LA is contraindicated within 24 hours of cocaine use — cocaine blocks catecholamine reuptake → synergistic vasopressor effect → hypertensive crisis, arrhythmia, MI. Malignant hyperthermia: rare pharmacogenetic condition triggered by volatile anaesthetics and suxamethonium — amide local anaesthetics (lidocaine, articaine, bupivacaine) are safe in MH-susceptible patients; ester LAs (procaine, benzocaine) — also safe. Dentally relevant because the patient should be flagged and GA avoided in favour of LA-based treatment.
Clinical Considerations
- A new or updated medical history must be taken at every dental appointment — not just at the first registration visit: Medical conditions change — patients are newly diagnosed with diabetes, start warfarin after atrial fibrillation, begin bisphosphonate therapy, become pregnant, or undergo chemotherapy between dental appointments. A medical history taken at registration and never reviewed is a medicolegal liability and a patient safety risk. The standard of care requires at minimum a verbal check (“Has anything changed with your health or medications since your last visit?”) at every appointment, with a full written update when significant changes are identified. Written medical histories should be signed by the patient and dated — if the history is reviewed and unchanged, the clinician should document “medical history reviewed and unchanged” with a date and signature.
- Infective endocarditis prophylaxis is no longer routinely recommended for most cardiac conditions in the UK and US — the indications have been significantly narrowed since 2007–2008: The 2007 NICE guideline and 2008 AHA guideline fundamentally changed IE prophylaxis practice. The key change: antibiotic prophylaxis does NOT prevent IE from dental bacteraemia in the vast majority of at-risk patients, because: (1) bacteraemia from normal daily oral activities (toothbrushing, eating) exceeds the cumulative bacteraemia from dental procedures; (2) the absolute risk of IE from any single dental procedure is very low; (3) the potential harms of widespread antibiotic use (allergy, Clostridium difficile, antibiotic resistance) outweigh the uncertain benefit. Current indications (UK/US): prosthetic valves; previous IE; certain congenital heart conditions (unrepaired cyanotic CHD; repaired with residual defect at or adjacent to the site of prosthetic material; repairs within 6 months). Maintaining good oral hygiene and regular dental attendance is now considered the most important preventive measure for IE in at-risk patients.
- Patients taking monoamine oxidase inhibitors (MAOIs) require special precautions — although rarely encountered, the interactions with vasoconstrictors and some analgesics are potentially fatal: MAOIs (phenelzine, tranylcypromine — old antidepressants; selegiline — for Parkinson’s disease) inhibit the enzymatic breakdown of catecholamines and serotonin. Drug interactions: sympathomimetics including epinephrine — MAOIs inhibit the intraneuronal breakdown of catecholamines — exaggerated pressor response is possible (though the risk with dental doses of epinephrine is considered low by most authorities, caution is warranted). Pethidine (meperidine) — ABSOLUTE contraindication with MAOIs — serotonin syndrome (hyperthermia, rigidity, myoclonus, autonomic instability, coma). Codeine should also be used with caution. Most dental analgesics are safe (paracetamol, NSAIDs), but always verify with the prescribing physician before adding any drug to the regimen of a patient on an MAOI.
- Gingival hyperplasia from certain medications must be distinguished from inflammatory gingival enlargement — the treatment approach differs: Drug-induced gingival overgrowth (DIGO) occurs with three drug classes: calcium channel blockers (most commonly nifedipine, also amlodipine, diltiazem); phenytoin (antiepileptic); and cyclosporin (immunosuppressant). DIGO begins in the anterior labial gingiva in the interdental papillae and spreads — it is characterised by fibrotic, pale-pink, firm hyperplastic tissue that may partially or completely cover the tooth crowns. Inflammatory gingival enlargement (from plaque) overlaps and worsens DIGO. Management: (1) meticulous plaque control (removing the inflammatory component improves DIGO significantly); (2) liaison with the prescribing physician about substituting to a less hyperplasia-prone alternative (e.g., switching from nifedipine to amlodipine [less DIGO], or from cyclosporin to tacrolimus); (3) surgical gingivectomy if medical management insufficient — high recurrence rate if the causative drug is continued.
- The dentist has a duty to maintain patient confidentiality but also a duty to protect third parties in exceptional circumstances — understanding the limits of patient confidentiality is essential: Medical information obtained during the medical history is confidential and governed by law (HIPAA in the US; Data Protection Act/GDPR in the UK). It must not be shared without patient consent — including with other members of the patient’s family, their employer, or other healthcare providers without consent (except in the specific context of a referral letter, for which implicit consent exists). Exceptions where disclosure without consent may be justified or required: serious risk of harm to a third party (e.g., a patient driving a vehicle who has uncontrolled epilepsy and refuses to disclose this to the DVLA — the dentist may have a duty to report); notifiable diseases; court order; sharing within the immediate treating dental team. Good documentation practice: the medical history and all treatment decisions based upon it should be contemporaneously recorded in the clinical notes.
Common Mistakes & Misconceptions
- Misconception: “Warfarin should be stopped before dental extractions to reduce bleeding risk.”
Correction: Stopping warfarin before dental extractions increases the risk of life-threatening thromboembolic events (stroke, PE, prosthetic valve thrombosis) without meaningfully reducing the risk of post-extraction bleeding, provided local haemostatic measures are used. Current guidelines unanimously recommend continuing warfarin for simple dental extractions when INR ≤3.5. Local haemostasis (tranexamic acid 5% mouthwash × 5 days, absorbable haemostatic material, resorbable sutures) is effective in controlling post-extraction bleeding. Dentists who stop warfarin before extractions do so unnecessarily and expose patients to serious harm. - Misconception: “Patients with an allergy to penicillin should receive clindamycin for infective endocarditis prophylaxis.”
Correction: This was the previous guidance, but current NICE and AHA guidelines do not recommend routine antibiotic prophylaxis for dental procedures in most patients — including those with most cardiac conditions. Therefore, the question of which antibiotic to use for penicillin-allergic patients has become largely moot for routine dental practice. For the narrow group in whom prophylaxis IS still indicated (prosthetic valves, previous IE, specific CHD), the current alternatives in penicillin-allergic patients are: clindamycin 600mg (UK) or azithromycin/clarithromycin 500mg (US). The key point is that routine antibiotic prophylaxis has been stopped — not simply changed. - Misconception: “All patients with heart murmurs require antibiotic prophylaxis before dental procedures.”
Correction: Heart murmurs are extremely common (particularly functional/innocent murmurs in children and young adults) and the vast majority do NOT confer risk of infective endocarditis following dental procedures. The IE risk is related to the specific underlying cardiac anatomy — not the presence of a murmur per se. Prophylaxis is indicated only for the specific high-risk conditions listed above (prosthetic valves, previous IE, specific CHD). A patient with a functional flow murmur, mitral valve prolapse (without regurgitation), or even mitral valve prolapse with regurgitation does NOT require antibiotic prophylaxis under current guidelines — this was changed in 2007/2008 and is a very common board examination topic. - Misconception: “Epinephrine-containing local anaesthetics are absolutely contraindicated in all patients with heart disease.”
Correction: Epinephrine in dental local anaesthetics is safe in patients with controlled cardiovascular disease, provided the dose is limited to 0.04mg per appointment (2 cartridges of 1:80,000 or 4 cartridges of 1:100,000). The key evidence: adequate pain control reduces the patient’s endogenous catecholamine release (from stress and pain), which would otherwise be far greater than the exogenous dose from 2 LA cartridges. True contraindications to epinephrine in LA: uncontrolled hypertension (SBP >180); unstable angina; recent MI (<6 months); severe cardiac arrhythmia; patients on non-selective beta-blockers (propranolol, nadolol) — risk of hypertensive crisis. Well-controlled hypertension, stable angina, and remote MI are NOT absolute contraindications. - Misconception: “Second-generation antihistamines (loratadine, cetirizine) are safe in dental practice without any interactions.”
Correction: While second-generation antihistamines are far less sedating than first-generation agents and are generally well-tolerated, they do have clinically relevant interactions in the dental context. Clarithromycin and erythromycin (both CYP3A4 inhibitors) increase plasma levels of some antihistamines (particularly terfenadine and astemizole — now withdrawn — but also loratadine and to a lesser extent cetirizine). The most important interaction is with terfenadine-class antihistamines and macrolide antibiotics → QT prolongation → potentially fatal ventricular arrhythmia (Torsades de Pointes) — this led to the withdrawal of terfenadine from most markets. Additionally, antihistamines cause xerostomia (dry mouth) — which, combined with dental anxiety and treatment, can significantly worsen patient comfort and increase caries risk in long-term users.
Related Topics
References & Sources
- American Society of Anesthesiologists (2020). ASA Physical Status Classification System. asahq.org. [Current ASA classification with updated examples for each class]
- Scottish Dental Clinical Effectiveness Programme (2015). Management of Dental Patients Taking Anticoagulants or Antiplatelet Drugs. SDCEP. [Current UK guidance on warfarin, DOACs, and antiplatelet therapy for dental procedures]
- NICE Clinical Guideline CG64 (2008, updated 2016). Prophylaxis Against Infective Endocarditis. National Institute for Health and Care Excellence. [UK guideline removing routine antibiotic prophylaxis for most at-risk patients]
- Wilson W, Taubert KA, Gewitz M, et al. (2007). Prevention of infective endocarditis. JADA, 138(6):739–745. [AHA guideline reducing IE prophylaxis indications]
- Ruggiero SL, Dodson TB, Fantasia J, et al. (2014). AAOMS Position Paper on MRONJ — 2014 Update. Journal of Oral and Maxillofacial Surgery, 72(10):1938–1956. [MRONJ staging and management — bisphosphonate and denosumab risk]
- Malamed SF (2020). Handbook of Local Anesthesia, 7th ed. Elsevier. [Comprehensive LA reference — doses, drug interactions, medical conditions]
- Greenberg MS, Glick M, Ship JA (2008). Burket’s Oral Medicine, 11th ed. PMPH-USA. [Standard dental medicine reference — systemic disease and oral health interactions]
- British National Formulary (BNF, current edition). Joint Formulary Committee. BMJ Group and Pharmaceutical Press. [UK drug reference — interactions, contraindications, pregnancy safety]
Summary
Medical history is the foundation of safe dental practice — it must be taken comprehensively at first visit and updated at every subsequent appointment. The ASA classification (I–VI) provides standardised risk stratification: general dental practice manages ASA I–III; ASA IV+ requires specialist or hospital dental care. Key prescribing principles from medical history: warfarin should NOT be stopped for simple extractions (INR ≤3.5 is safe with local haemostasis); epinephrine is safe in cardiovascular patients up to 0.04mg; bisphosphonates create MRONJ risk with oral surgery; pregnancy — second trimester is the safest treatment window; GTN is contraindicated with PDE5 inhibitors. Drug interactions most tested: metronidazole + warfarin (raised INR); NSAIDs + warfarin/lithium/methotrexate; macrolides + statins/cyclosporin (CYP3A4 inhibition); propranolol + epinephrine (hypertensive crisis).
Key Takeaways
- ASA classification: I = healthy; II = mild disease (controlled); III = severe disease (stable); IV = life-threatening (constant threat). General practice: I–III. Hospital dentistry: IV+.
- Warfarin: Do NOT stop. INR ≤3.5 = safe for simple extractions with local haemostasis (tranexamic acid mouthwash, Surgicel, sutures). Avoid: metronidazole, NSAIDs, erythromycin, fluconazole (all raise INR).
- Epinephrine in LA: Cardiovascular patients = max 0.04mg (2 × 1:80,000 cartridges). Healthy patients = max 0.2mg. Contraindicated in: uncontrolled HTN, unstable angina, propranolol use, cocaine use, pheochromocytoma.
- Bisphosphonates: IV (cancer) = high MRONJ risk — avoid extraction; specialist management. Oral (osteoporosis) = low risk — proceed with informed consent and atraumatic technique. Prevention before starting IV bisphosphonates — extract all hopeless teeth first.
- IE prophylaxis: Now only for: prosthetic valves; previous IE; specific unrepaired/recently repaired congenital heart disease. NOT for: heart murmurs, MVP, rheumatic heart disease (unless prosthetic valve). Good oral hygiene is the primary prevention strategy.
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