01
Pathophysiology of Oral Complications
The oral cavity — a target tissue for systemic toxicities
The oral mucosa is one of the body's most sensitive tissues due to its high cellular turnover rate — basal epithelial cells divide approximately every 7 to 14 days. This rapid kinetics makes it a prime target for cytotoxic agents.
The management of oral complications must no longer be regarded as an accessory comfort measure, but as a therapeutic imperative conditioning the continuation of oncological treatment, the prevention of serious systemic infections, and the maintenance of the patient's nutritional integrity.
Direct toxicity — Cellular mechanisms
Antimetabolites, alkylating agents, spindle poisons
- Targeting of nucleic acids in actively dividing cells
- Inhibition of basal keratinocyte mitosis
- Progressive epithelial thinning
- Loss of barrier integrity → erosive zones
Indirect toxicity — Myelosuppression
Neutropenia + thrombocytopenia
- White cell line collapse → immune deficiency
- ANC <500/mm³: minor odontogenic infection → possible septicaemia
- Thrombocytopenia → spontaneous gingival bleeding
- Impaired oral hygiene due to pain and bleeding
The 5 phases of mucositis pathophysiology (Sonis model)
| Phase | Mechanism | Timeframe |
|---|---|---|
| 1. Initiation | Reactive oxygen species (ROS) production | Immediate |
| 2. Signalling | NF-κB activation and transcription factors | D1–D3 |
| 3. Amplification | Pro-inflammatory cytokine cascade (TNF-α, IL-1β) | D3–D5 |
| 4. Ulceration | Mucosal breakdown + bacterial colonisation | D5–D14 |
| 5. Healing | Epithelial regeneration and tissue remodelling | D14–D21 |
02
Dental Clearance — Pre-Treatment Assessment
Objectives of the pre-chemotherapy dental assessment
- Sanitise the oral cavity by eliminating all infectious or irritative foci
- Complete the assessment as early as possible after the cancer diagnosis
- Prevent any infectious emergency during the immunosuppression phase
- Reduce risks of MRONJ, odontogenic septicaemia and severe mucositis
Clinical and radiographic diagnostic protocol
- Meticulous inspection of mucosae and periodontal tissues
- Comprehensive periodontal probing — pockets ≥ 4 mm to be treated systematically
- Orthopantomogram (OPT) — indispensable baseline
- Periapical radiographs for suspicious periapical lesions
- CBCT when root proximity to the mandibular canal requires assessment before extraction
- Particular attention to partially impacted third molars and old root canal treatments with bone rarefaction
Dental preparation — Indications table
| Type of care | Recommendation | Justification |
|---|---|---|
| Calculus and plaque | Full scaling + polishing | Reduction of overall bacterial load |
| Enamel caries | Definitive restoration | Prevention of pulpal involvement |
| Pulpal pathology | Endodontic treatment or extraction | Elimination of abscess risk under aplasia |
| Grade III tooth mobility | Systematic extraction | Avoid acute periodontal infections |
| Removable prostheses | Adjustment or rebasing | Prevention of mucosal trauma (mucositis) |
| Periodontal pockets | Full periodontal debridement | Elimination of silent infectious foci |
03
Timing of Interventions
Mandatory minimum interval — 14 days
Consensus establishes a minimum interval of 14 days between any invasive procedure and the start of cytotoxic chemotherapy. This interval allows stable clot formation and the onset of mucosal closure. Failure to respect it exposes the patient to osteoradionecrosis and absence of re-epithelialisation.
Strategy in oncological emergency — Interval not achievable
When chemotherapy cannot be deferred and the 14-day interval is not available.
Priority — Non-invasive
- Temporisation with targeted antibiotherapy on the infectious focus
- Non-invasive local care (supragingival scaling, gentle polishing)
- Avoid any extraction or surgery before the nadir
Multidisciplinary consultation
- Shared decision with the medical oncology team
- Prioritise care according to the level of immediate infectious risk
- Plan invasive care during inter-cycle windows (ANC > 1,500/mm³)
Therapeutic windows during chemotherapy
Optimal timing for dental care
- D8 to D14 of a standard cycle: rising ANC — safe window
- FBC required < 48 h before any procedure
- ANC > 1,500/mm³ and platelets > 50,000/mm³: ambulatory care feasible
- Planning with the haematologist or referring oncologist
Nadir period — Absolutely avoid
Maximum aplasia phase
- D7 to D14 after most conventional chemotherapy regimens
- No elective invasive care during this phase
- Emergencies only: drainage without extraction, curative antibiotics
- Hospitalisation if sepsis of odontogenic origin
04
Nadir and Haematological Parameters
Interpreting blood counts — Decision-making thresholds
Any intervention must be preceded by a recent FBC (less than 48 hours old). The clinician must calculate the Absolute Neutrophil Count (ANC) = % neutrophils × total white cell count.
Neutropenia classification — Grades and risks
| Grade | ANC (neutrophils/mm³) | Infectious risk | Dental management |
|---|---|---|---|
| Mild | 1,000 to 1,500 | Moderate | Conservative care feasible — antibiotic prophylaxis per procedure |
| Moderate | 500 to 1,000 | High | Defer non-urgent care — symptomatic treatment only |
| Severe | < 500 | Very high | Emergencies only — hospital setting — IV antibiotics |
| Profound | < 100 | Critical | No dental care — absolute medical stabilisation |
Platelet thresholds — Clinical decisions
Haemorrhagic risk
- > 50,000/mm³: invasive care feasible in outpatient setting
- 20,000 to 50,000/mm³: urgent procedures in hospital with enhanced local haemostasis
- < 20,000/mm³: no invasive procedure — platelet transfusion if emergency
- Haemostatic measures: sutures, biological glues, prolonged compression
Emergencies during the nadir — Preferred procedures
Decompression without aggression
- Pulp chamber opening for drainage — avoids extraction
- Mucosal abscess incision — immediate decompression
- Broad-spectrum antibiotics: Amoxicillin/Clavulanate + Metronidazole
- No extraction during aplasia — defer until haematological recovery
05
Oral Mucositis — Grades and Protocols
Epidemiology and clinical impact
Oral mucositis affects up to 40% of patients on conventional chemotherapy and up to 100% of those receiving high-dose conditioning before bone marrow transplantation. It manifests as intense pain, speech and swallowing difficulties, potentially leading to dehydration and malnutrition.
WHO / CTCAE grading — Standardised assessment
| Grade | Clinical manifestations | Functional impact | Management |
|---|---|---|---|
| Grade 0 | No signs | Normal diet | Prevention only (BOC) |
| Grade 1 | Erythema and tenderness | Normal diet | Reinforced BOC + bicarbonate rinse |
| Grade 2 | Erythema + isolated ulcers | Solid food possible | Analgesia + Magic Mouthwash |
| Grade 3 | Confluent ulcers | Liquids only | Systemic analgesics + nutritional support |
| Grade 4 | Extensive necrosis + bleeding | Tube feeding or IV | Hospitalisation — intensive care |
Oral cryotherapy — Proven prevention
MASCC/ISOO 2024 — Strong recommendation
- Indications: 5-FU or Melphalan bolus infusion
- Maintain ice chips or sorbet in the mouth throughout the entire infusion (≈ 30 min)
- Local vasoconstriction → reduced drug delivery to the mucosa
- Demonstrated efficacy — significant reduction in mucositis incidence
Photobiomodulation (PBM) — Low-level laser
MASCC/ISOO 2024 — For HSCT patients
- Low-energy laser (630–1000 nm) applied to at-risk sites
- Reduces oxidative stress and accelerates tissue repair
- Indicated for high-dose chemotherapy before HSCT
- Protocol: daily applications during the risk phase
Basic Oral Care (BOC) — MASCC/ISOO 2024
Cornerstone of prevention — to be initiated from the first day of oncological treatment.
Brushing — Technique and equipment
- Extra-soft nylon bristle toothbrush — mandatory
- Non-abrasive toothpaste, without whitening agents or strong menthol
- Gentle brushing after each meal and before bed
- Tongue cleaning with a soft brush or tongue scraper
Mouthrinses — Permitted products
- 1.4% sodium bicarbonate solution — alkalinising and cleansing action
- Avoid alcohol-containing mouthrinses (exacerbate dryness)
- Avoid chlorhexidine during acute ulceration (toxic to regenerating keratinocytes)
- Magic Mouthwash (viscous lidocaine + corticosteroid + sucralfate) for grade ≥ 2
Products strictly contraindicated during active mucositis
Alcohol-containing mouthrinses exacerbate dryness and pain. Chlorhexidine during acute ulceration is toxic to keratinocytes undergoing regeneration. Both products are strictly banned during mucositis of grade ≥ 2.
06
Xerostomia and Caries Prevention
Impact of chemotherapy-induced xerostomia
Chemotherapy may induce salivary gland dysfunction. Reduced salivary flow causes a rapid drop in oral pH, promoting rampant caries development, particularly at the cervical margins and exposed root surfaces. Saliva plays an essential protective role through its buffering capacity and antimicrobial properties.
Palliative measures — Saliva substitutes
Symptomatic relief
- Constant hydration: small sips of water throughout the day
- Saliva substitutes: gels, sprays, hydrating rinses (Biotène®, BioXtra®)
- Nocturnal use is a priority (severe night-time dryness)
- Avoid alcohol, tobacco and acidic or sugary foods
Sialagogues — Residual secretion stimulation
If residual secretion is present
- Pilocarpine: 5 mg × 3/day — stimulates residual salivary glands
- Anetholtrithione: alternative to pilocarpine
- CI: asthma, narrow-angle glaucoma, bradycardia, Parkinson's disease
- Sugar-free gum (xylitol): residual mechanical stimulation
Custom Fluoride Tray Protocol — Mandatory for persistent hyposalivation
Indicated for any patient with persistent hyposalivation following chemotherapy.
Equipment and product
- Soft custom-thermoformed trays on patient models
- High-fluoride gel: Fluogel® 2000 or equivalent (20,000 ppm fluoride)
- Place gel in the trays without overfilling
Daily usage protocol
- Standard brushing first — then insert the trays
- Wear for 5 minutes every evening after the last meal
- Gentle mouth rinse after removal — avoid vigorous spitting
- No eating or drinking for 30 minutes after the treatment
- Continue until salivary flow has returned to normal
07
MRONJ — Medication-Related Osteonecrosis of the Jaw
Diagnostic definition
MRONJ is diagnosed when exposed bone in the maxillofacial region persists for more than 8 weeks in a patient receiving at-risk agents, in the absence of prior radiotherapy to that area.
At-risk drugs and classification
| Class | Representative drug | Retention duration | MRONJ risk |
|---|---|---|---|
| IV Bisphosphonates | Zoledronate (Zometa®) | Very long (years) | 1–5% (cancer) |
| RANK-L inhibitor | Denosumab (Xgeva®) | Intermediate (6 months) | Comparable to Zoledronate |
| Anti-angiogenics | Bevacizumab (Avastin®) | Short (weeks) | <1% (alone) |
| mTOR inhibitors | Everolimus (Afinitor®) | Short (days) | Low but reported |
Extraction protocol under MRONJ risk agents
When extraction is unavoidable — the most atraumatic surgery possible.
Peri-operative antibiotic prophylaxis
- Begin the day before the extraction
- Amoxicillin 2 g/day in the absence of allergy
- If allergic: Clindamycin 600 mg/day
- Continue until complete mucosal closure
Atraumatic surgical technique
- Gentlest possible extraction — progressive luxation without force
- Sharp bony edge regularisation
- Primary closure without tension
- Resorbable sutures — no immediate post-operative prosthetic compression
Anti-angiogenics — Peri-operative management
- Short half-life → temporary interruption possible (4–8 weeks)
- Suspension decision in consultation with the referring oncologist
- IV bisphosphonates: suspension not feasible — same maximum precaution protocol
Prevention — The priority strategy
No elective surgery on irradiated jaws or under IV bisphosphonates without prior consultation with the oncological team. The best MRONJ strategy is prevention through excellent hygiene control and elimination of prosthetic trauma.
08
Critical Drug Interactions
⚠
Methotrexate + NSAIDs — Potentially fatal interaction
⚠ Mechanism
NSAIDs inhibit the active tubular secretion of methotrexate, reducing its renal clearance. Blood accumulation causes fulminant aplasia and severe haemorrhagic mucositis.
✓ Clinical management
NSAIDs are absolutely contraindicated in any patient receiving methotrexate at oncological doses (>20 mg/week). Use paracetamol (acetaminophen) exclusively as first-line analgesic.
⚠
5-FU / Capecitabine + DPD deficiency
⚠ Risk
Even a partial DPD (dihydropyrimidine dehydrogenase) deficiency can provoke lethal toxicity after a single 5-FU dose. Profuse oral ulcerations appearing very early may be the first sign of metabolic overdose.
✓ Alert the oncologist
DPD screening (uracilemia) is mandatory before initiation. If severe oral ulcers from D1–D3 → immediately contact the oncologist — suspected metabolic overdose.
⚠
Metronidazole + Chemotherapy agents
⚠ Dual interaction
Metronidazole increases 5-FU toxicity (reduced clearance) and doubles busulfan plasma concentrations (risk in transplant conditioning). Disulfiram-like effect — prohibits alcohol in any form, including mouthrinses.
✓ Alternative
Substitute with Amoxicillin/Clavulanate for anaerobic infections. If metronidazole is essential → prior oncological consultation. Always prescribe alcohol-free mouthrinses.
⚠
Azole antifungals + Anticoagulants / Cytotoxics
⚠ CYP3A4 enzymatic inhibition
Miconazole and fluconazole are potent CYP3A4 inhibitors. They increase plasma levels of many cytotoxics and anticoagulants (warfarin) — risk of overdose and severe haemorrhage.
✓ Biological monitoring
If azole antifungals are necessary → close INR monitoring in patients on warfarin. Prefer amphotericin B mouthrinse for localised oral candidiasis (no significant systemic interaction).
Common dental drugs with interaction risk in oncology
| Dental drug | Interacts with | Consequences | Management |
|---|---|---|---|
| NSAIDs (ibuprofen, ketoprofen) | Methotrexate | Fatal aplasia | Absolute CI — paracetamol |
| Metronidazole | 5-FU, Busulfan | Severe toxicity | Oncological consultation |
| Fluconazole / Miconazole | Warfarin, cytotoxics | Overdose / haemorrhage | Topical amphotericin B |
| Aspirin | Methotrexate, chemotherapy | Haematological toxicity | Contraindicated — paracetamol |
09
Paediatric Oncology and Oncogeriatrics
Paediatric oncology — Long-term sequelae
Children treated before age 5 — high risk
- Tooth agenesis, microdontia, taurodontism, severe enamel hypoplasia
- Regular orthodontic and paediatric dental follow-up is essential
- Aspirin strictly prohibited — Reye's syndrome risk
- Tetracyclines (doxycycline) contraindicated before age 8 — irreversible staining and enamel fragility
Oncogeriatrics — Elderly patient under chemotherapy
Systemic frailty and polypharmacy
- Weight loss → prosthetic instability → traumatic ulceration
- Unstable prosthesis on mucositis = major infectious entry portal
- Temporary rebasing or suspension of prosthesis wear during critical phases
- Erythematous candidiasis frequent under prosthesis + chemotherapy
- Prior periodontal debridement — elimination of silent foci
Home oral chemotherapy — Enhanced vigilance
The current trend towards oral therapies (capecitabine, ibrutinib, olaparib…) may lead to a normalisation of treatment and reduced vigilance. A quarterly dental assessment is recommended for these patients.
- Hand-foot syndrome and acneiform rashes linked to anti-EGFR agents may be accompanied by persistent stomatitis
- Patient education to detect early signs of mucositis or xerostomia
- City-hospital circuit (Onkolink type): GP + pharmacist + community dentist
- Cervical caries related to prolonged iatrogenic hyposalivation: preventive fluoride therapy mandatory
10
Clinical FAQ
The ANC is calculated as follows: ANC = % neutrophils × total white cell count. For example, if the FBC shows 3,000 WBC/mm³ with 40% neutrophils, ANC = 1,200/mm³ (mild neutropenia). To perform an extraction in an outpatient clinic, minimum thresholds are: ANC > 1,500/mm³ and platelets > 50,000/mm³. Below these thresholds, invasive procedures must be deferred or performed in a hospital setting with enhanced local haemostasis. The FBC must be less than 48 hours old.
This is a high-risk MRONJ situation requiring prior multidisciplinary consultation with the oncologist. The strategy is: (1) assess whether extraction can be deferred; (2) if unavoidable, antibiotic prophylaxis with amoxicillin 2 g/day from the day before until complete mucosal closure; (3) the most atraumatic surgical technique possible, sharp bony edge regularisation, primary closure without tension; (4) weekly clinical follow-up. Unlike anti-angiogenics, IV bisphosphonates bind quasi-irreversibly to bone — short-term suspension is not feasible.
For grade 3 mucositis (liquids only): (1) Local analgesia — Magic Mouthwash: 2% viscous lidocaine + methylprednisolone + sucralfate, rinse 4 times daily before meals; (2) 1.4% sodium bicarbonate rinse after each meal and at bedtime; (3) Strictly avoid alcohol and chlorhexidine; (4) Ultra-gentle brushing (dampened extra-soft brush) with non-irritating toothpaste; (5) Liquid diet at room temperature; (6) If pain is uncontrolled — systemic analgesics (paracetamol first, never NSAIDs); (7) If ANC < 500 → hospitalisation for infectious risk assessment.
No, never without verifying the ongoing oncological treatment. The general rule is to systematically request the complete list of oncological medications before any prescription. Ibuprofen (and all NSAIDs) is absolutely contraindicated in patients receiving methotrexate at oncological doses (>20 mg/week) — risk of fatal aplasia. It is also contraindicated in thrombocytopenic patients (worsens haemorrhagic risk) and in those on anticoagulants. Paracetamol (acetaminophen) is the systematic first-line analgesic in oncological patients, provided there is no hepatic insufficiency.
Candidiasis is frequent (Candida albicans) in a context of immunosuppression and xerostomia. Management: (1) Amphotericin B oral suspension 100 mg/mL — rinse and swallow, 4 times/day × 7 to 14 days: local action with no significant systemic interaction — first choice; (2) If refractory or pharyngeal extension: systemic fluconazole 200 mg D1 then 100 mg/day × 7–14 days — monitor INR (warfarin interaction); (3) Always treat the removable prosthesis simultaneously (soak in antifungal solution or replace); (4) Correct concurrent xerostomia — the major predisposing factor.
The five pillars of 2024-2025 recommendations (MASCC/ISOO + HAS): (1) Systematic pre-treatment dental assessment with a minimum 14-day interval for any extraction before chemotherapy; (2) Mandatory biological thresholds before any invasive care: ANC > 1,500/mm³ + platelets > 50,000/mm³ in outpatient settings; (3) BOC + oral cryotherapy for mucositis prevention — avoidance of chlorhexidine and alcohol-based rinses during active phase; (4) Mandatory fluoride tray prophylaxis for any persistent hyposalivation (20,000 ppm); (5) Pharmacological vigilance: paracetamol alone as analgesic, systematic checking of NSAID/methotrexate and azole/warfarin interactions.