Mouth Ulcers and Canker Sores: When a Townsville Dentist Should Look

Most mouth ulcers are minor, painful, and self-limiting — and they account for one of the most common reasons people contact a dental practice between scheduled appointments. The vast majority heal on their own within two weeks. The clinical question is not how to make every ulcer go away faster (most do not need treatment beyond pain relief), but how to recognise the small number of ulcers that signal something more serious. The Australian Dental Association and Cancer Council Australia both publish guidance that any oral ulcer persisting beyond two to three weeks warrants assessment, primarily to exclude oral cancer and identify treatable underlying systemic causes.

This article, written by Dr. Kira San (BDSc, James Cook University), explains what mouth ulcers are, why they recur, the common and less common causes seen in Townsville patients, and the specific warning signs that should prompt a same-week dental appointment.

What a Mouth Ulcer Actually Is

The term “mouth ulcer” describes a break in the oral mucosa — the soft tissue lining of the mouth — that exposes the underlying connective tissue. Most are aphthous ulcers (recurrent aphthous stomatitis, RAS), a benign and very common condition affecting an estimated 20 per cent of Australians at some point in their lives. They are characterised by:

• A round or oval shape
• A white or yellow centre (the necrotic base)
• A red, inflamed border
• Tenderness disproportionate to size
• Spontaneous healing without scarring within 7 to 14 days

Aphthous ulcers occur on non-keratinised mucosa — the soft, mobile lining of the cheeks, the underside of the tongue, the floor of the mouth, the soft palate, and the inside of the lips. They do not typically appear on the hard palate, the gums attached to the teeth, or the dorsum (top surface) of the tongue, because these surfaces are keratinised and structurally tougher.

There are three clinical subtypes of aphthous ulcer:

Minor aphthous ulcers are the most common, smaller than 10 millimetres, and heal in 7 to 14 days. Most patients have one to three at a time, three to six episodes a year.

Major aphthous ulcers are larger than 10 millimetres, deeper, and significantly more painful. They may take three to six weeks to heal and can leave scarring. They are less common but disproportionately distressing for affected patients.

Herpetiform ulcers present as multiple small (1 to 3 millimetre) ulcers in clusters, often coalescing into larger irregular ulcers. Despite the name, they are not caused by herpes simplex virus.

Common Causes and Triggers

Aphthous ulcers are not contagious and not caused by a single pathogen. They reflect a multifactorial breakdown of the protective oral mucosal barrier. The triggers most commonly identified in clinical practice include:

Mechanical trauma. A bitten cheek, a sharp tooth edge, a fractured filling, a denture flange that rubs, an orthodontic bracket, or even an over-vigorous toothbrushing technique can break the mucosa and initiate an ulcer. These are the easiest causes to identify and resolve in a dental examination — a smooth restoration of a sharp tooth edge or adjustment of a denture often eliminates recurrent ulceration at that site entirely. For patients in orthodontic treatment, our adult braces guide covers the ulceration pattern that often appears in the first weeks after fitting.

Sodium lauryl sulfate (SLS) in toothpaste. SLS is a foaming agent in many mainstream toothpastes that has been shown to increase ulcer frequency in susceptible patients. Switching to an SLS-free toothpaste (Sensodyne ProNamel, Biotene, and several Colgate Total formulations are SLS-free; check the ingredient list) eliminates ulceration in a meaningful proportion of patients with frequent recurrence.

Nutritional deficiencies. Low iron, folate, vitamin B12, and zinc are independently associated with recurrent ulceration. In Australia, iron-deficiency anaemia is common in women of reproductive age, and B12 deficiency is increasingly recognised in older adults and in patients on long-term metformin or proton pump inhibitors. A simple GP-ordered blood panel — full blood count, iron studies, folate, B12, and zinc — identifies these causes definitively.

Food sensitivities. Some patients report consistent ulcer outbreaks after specific foods. Common culprits include nuts (particularly walnuts), tomatoes, citrus, chocolate, gluten in coeliac patients, and benzoates and cinnamaldehyde used as food preservatives and flavourings. A food diary tracked alongside ulcer episodes can identify triggers more reliably than guesswork.

Stress and hormonal cycles. Acute psychological stress is a well-documented trigger for many patients. In women, ulceration is often cyclical, appearing in the luteal phase before menstruation. Some women report complete remission during pregnancy and a return of ulceration postpartum.

Smoking cessation. Paradoxically, ex-smokers experience increased ulcer frequency in the months after quitting, before the rate normalises. The nicotine in tobacco appears to suppress aphthous ulceration, though the long-term harms of smoking far outweigh this minor benefit.

Systemic Conditions That Cause Recurrent Mouth Ulcers

A subset of patients with recurrent ulceration has an underlying systemic condition that the dental practice helps identify. The most clinically important are:

Coeliac disease — gluten-induced autoimmune enteropathy that affects approximately 1 in 70 Australians. Recurrent oral ulceration is a recognised extra-intestinal manifestation. A coeliac serology blood test is appropriate in any patient with frequent unexplained ulceration. A gluten-free diet often resolves the ulcers entirely.

Inflammatory bowel disease (Crohn’s disease and ulcerative colitis) — both can cause oral ulceration that mirrors gastrointestinal flares. Crohn’s disease can also present with deep linear ulcers in the buccal vestibule and a “cobblestone” mucosal appearance.

Behcet’s syndrome — a rare autoimmune vasculitis characterised by recurrent oral ulcers, genital ulcers, eye inflammation, and skin lesions. Severe and frequent oral ulceration without explanation in a young adult should prompt evaluation for Behcet’s, particularly in patients of Mediterranean, Middle Eastern, or East Asian heritage.

HIV infection — can present with recurrent and severe oral ulceration, often as the first sign of immunosuppression. Routine HIV testing is appropriate in any patient with severe persistent ulceration without obvious cause.

Lupus erythematosus — systemic and cutaneous lupus both cause oral ulceration, typically on the hard palate. The 2019 EULAR/ACR classification criteria for systemic lupus include oral ulceration as a clinical feature.

Drug reactions — non-steroidal anti-inflammatories (NSAIDs), ACE inhibitors, beta-blockers, alendronate, methotrexate, and several chemotherapy agents can all cause oral ulceration. In patients on multiple medications, a medication review is part of the workup.

For Townsville patients with recurrent ulceration, the standard approach is a dental examination to address local triggers, followed by GP referral for a structured systemic workup if ulceration persists. Our bleeding gums article covers a related set of systemic conditions that present in the dental chair.

Warning Signs: Ulcers That Need Urgent Assessment

The single most important reason mouth ulcers matter clinically is that oral cancer can mimic a benign ulcer in its early stages. The Cancer Council Australia reports approximately 5,000 new cases of head and neck cancer diagnosed in Australia each year, with five-year survival heavily dependent on early diagnosis. Late-stage oral cancer has a five-year survival around 30 per cent; early-stage disease detected at the ulcer stage has survival exceeding 80 per cent.

The clinical features that should prompt immediate dental or medical assessment include:

Duration. Any ulcer that has not begun to heal within 14 days, or that has fully persisted at 21 days, requires evaluation. Healing should be obvious by the third week — if the ulcer looks the same or worse, it is not behaving like an aphthous ulcer.

Painlessness or disproportionately mild pain. Aphthous ulcers are characteristically painful relative to their size. An ulcer that is large but only mildly tender is suspicious.

Raised or rolled edges. Benign ulcers typically have flat, soft edges. Rolled, indurated, or raised borders suggest a malignant or pre-malignant process.

Bleeding on contact. Aphthous ulcers do not typically bleed. An ulcer that bleeds easily on minor contact warrants prompt assessment.

Hard lump beneath the ulcer. Palpation revealing firm, tethered induration of the underlying tissue is a major red flag.

Unilateral persistent ulcer on the lateral tongue or floor of mouth. These are the highest-risk sites for oral squamous cell carcinoma and warrant a low threshold for biopsy.

Associated lymphadenopathy. A persistent enlarged lymph node in the neck on the same side as a non-healing ulcer requires urgent investigation.

Numbness or altered sensation. Loss of sensation in the lip, tongue, or face adjacent to a persistent ulcer suggests possible nerve involvement.

In Townsville, suspicious lesions are typically referred from a GP or dentist to the Maxillofacial Unit at Townsville University Hospital for biopsy and definitive diagnosis. Most referrals do not result in cancer diagnoses — but the system is designed so that the small minority that do are caught quickly.

Risk Factors for Oral Cancer in North Queensland

The major modifiable risk factors for oral cancer are well established:

Tobacco — every form (cigarettes, cigars, pipe, smokeless tobacco) carries elevated risk. Smoking remains higher in regional Queensland than in capital cities, according to AIHW national data.

Alcohol — heavy regular alcohol consumption is independently associated with oral cancer, and the combination with tobacco is multiplicative rather than additive.

HPV infection — particularly HPV-16 — is a growing cause of oropharyngeal cancer, especially in younger adults without traditional risk factors. Australian HPV vaccination programs are reducing this risk in younger cohorts.

Sun exposure — directly relevant in Townsville. Lip cancer (specifically the lower lip) is significantly more common in patients with chronic UV exposure. Outdoor workers, fishermen, sugarcane farmers, and others with cumulative sun exposure should be examined for any persistent lip lesion. Wearing SPF 30+ lip balm during outdoor work is a simple preventive measure.

Betel nut and areca chewing — relevant in some North Queensland communities with Pacific Islander or Southeast Asian heritage. These substances are independently carcinogenic to oral mucosa.

For Townsville patients in any of these risk categories, a six-monthly dental examination includes an oral cancer screen as standard. Our dental checkup page describes what an examination involves.

Practical Treatment for Aphthous Ulcers

The vast majority of mouth ulcers seen in Townsville Dental Clinic are routine aphthous ulcers that need symptomatic management while they heal. The evidence-based approach is:

Pain relief. Topical anaesthetic gels (benzocaine, lidocaine) provide short-term numbing. Apply directly to the ulcer 15 minutes before meals if eating is painful. Over-the-counter products such as Bonjela and SM-33 are widely available at Australian pharmacies. Avoid aspirin held against the ulcer — the practice of crushing aspirin onto a sore is an old folk remedy that causes additional chemical burn injury.

Antimicrobial mouthwash. Chlorhexidine 0.2 per cent rinsed for 30 seconds twice daily reduces bacterial colonisation and shortens healing. Use for no longer than two weeks at a time to avoid staining.

Topical corticosteroid. Triamcinolone 0.1 per cent in Orabase, applied 2 to 4 times daily directly to the ulcer, is the most effective topical treatment for moderate to severe ulcers. Available with a prescription from your GP or dentist.

Avoid irritants. Acidic foods (citrus, tomato, vinegar), salty snacks, spicy foods, sharp foods (chips, hard crusts), and very hot drinks all aggravate existing ulcers. Switching to soft, neutral, room-temperature foods until healing is complete reduces pain considerably.

Switch to SLS-free toothpaste. A simple intervention with strong evidence in patients with frequent recurrence. Continue indefinitely if ulcer frequency drops.

Identify and address local triggers. A dental examination to smooth a sharp tooth edge, replace a fractured filling, or adjust a rubbing denture often eliminates recurrence at that specific site.

Investigate systemic causes when warranted. Patients with frequent recurrence (more than three episodes a year), severe ulcers, or ulceration alongside other systemic symptoms (fatigue, weight loss, gastrointestinal symptoms, joint pain) should have a GP-ordered blood panel including full blood count, iron studies, folate, B12, zinc, and coeliac serology.

For severe and disabling recurrent ulceration that does not respond to topical management, referral to an oral medicine specialist for systemic immunomodulatory therapy (colchicine, prednisolone, dapsone) may be warranted.

When to Book a Townsville Dental Appointment

Most mouth ulcers do not need a dental visit. Book an appointment if:

• An ulcer has not begun to heal within 14 days
• You have more than three ulcer episodes a year
• Ulcers consistently appear in the same location
• An ulcer is unusually large (over 10 millimetres) or unusually painful
• You have associated systemic symptoms (fatigue, weight loss, gastrointestinal upset, joint pain)
• An ulcer has any of the warning features described above (raised edges, hard lump, painless persistence, easy bleeding)
• You are a smoker, heavy drinker, or have significant cumulative sun exposure and any persistent oral or lip lesion
• You suspect a sharp tooth, filling, or denture edge is causing recurrent ulceration

Townsville Dental Clinic offers same-week assessment for any persistent oral lesion. If we suspect anything more serious than an aphthous ulcer, we will refer you to the appropriate specialist promptly. For after-hours concerns where you are unable to wait, our emergency dentistry information outlines what to do.

Book through our contact page or call the practice during business hours. For most patients, a 20-minute consultation is enough to identify the cause, address local triggers, and provide a clear plan — whether that is reassurance and topical management, a referral for blood tests, or a prompt biopsy to settle a more concerning question.