Introduction

The National Head and Neck Cancer audit 2011 stated that there are approximately 7,354 new cases of head and neck cancer diagnosed in England and Wales each year, of which the audit had received 6,879.1 Approximately 90% of all malignant head and neck tumours are squamous cell carcinomas (SCC). The disease burden of head and neck cancer is significant; patients require intensive multimodality treatments and prolonged rehabilitation with long term support to achieve an adequate recovery. The disease significantly impacts on eating, drinking, speech, swallowing, smell, breathing, social interaction and work capabilities. Most head and neck cancers are treated with surgery or radiotherapy or, a combination of both. Chemotherapy alone is rarely appropriate for these forms of cancer, but chemotherapeutic agents are increasingly used to enhance the effects of radiotherapy; this is known as chemoradiation.

When a diagnosis of head and neck cancer is made, each individual case is discussed at a multi-disciplinary team (MDT) meeting to consider which treatment(s) may be the best option. Optimum management of patients with head and neck cancer requires the active involvement of experts from a particularly wide variety of fields. The members of the team consist of: maxillofacial consultant surgeons; ENT consultant surgeons; consultant oncologists; consultant radiologists; consultant pathologists; consultants in restorative dentistry; head and neck cancer specialist nurse; speech and language therapist and dieticians as well as other doctors and health professionals with an interest in cancer. The restorative consultant has a key role to report and treat any dental problem which may interrupt or compromise the course of cancer treatment. There is an increasing body of evidence demonstrating that unplanned interruptions of radical radiotherapy treatment results in prolonged overall treatment time, which can detrimentally affect local control and cure rates for patients with certain tumours. The tumour types reported in the literature as being most affected by interruptions include head and neck squamous cell carcinomas2,3 and cancer of the oesophagus.4,5 The consultant in restorative dentistry also has a key role in helping to improve quality of life post-cancer treatment by maximising oral rehabilitation opportunities before and following oncological care.

The role of the general dental practitioner

General dental practitioners (GDPs) play an important role in the primary prevention of oral cancer through patient education and lifestyle counselling in relation to smoking and alcohol consumption. Patients should be made aware that smoking and regularly drinking in excess can increase their risk of oral cancer. The importance of attending dental appointments must be highlighted to all patients. They should be mindful that dental visits are not only about treating dental disease but to prevent, screen and manage other conditions of the mouth such as mouth cancer, which may be life threatening.

Awareness and diagnosis of oral cancer is one of the primary responsibilities of any dentist, as the earlier the lesion is found the better the outcome. A diagnosis of intraoral carcinoma is primarily clinical but should always be confirmed histologically; however, this should not be undertaken in general dental practice because a biopsy will alter the appearance of the lesion and consequently makes it more difficult for a hospital specialist to examine and assess it. GDPs should immediately refer a patient with a suspicious lesion to the local oral and maxillofacial department.

The MDT are responsible for ensuring that specialised dentistry is available for head and neck cancer patients who require it. The British Association of Head and Neck Oncologists' recommend that every patient, not just those planned for radiotherapy, should have a dental assessment. Many of these patients have complex needs which cannot be satisfactorily met by the primary care dental services. It is essential that expert dental care is provided before, during and after radiotherapy.

It is important that dental practitioners have an understanding not only of the effects of malignant disease on their patient, but also the specific problems and side-effects from the cancer treatments. Patients undergoing radiotherapy can experience several unwanted oral side effects, which have both short- and long-term implications. GDPs should be aware of these implications and should liaise closely with the restorative consultants and the oncology team to establish the best oral care pathway.

The side-effects of radiotherapy on the oral environment

Therapeutic radiation to the head and neck causes both immediate sequelae such as cellulitis, mucositis, dysphagia, dysguesia, weight loss and severe pain of varying intensities, as well as long term sequelae such as rampant caries, trismus, xerostomia and osteoradionecrosis.6,7

The effects are variable and often difficult to predict. The effects are dose-related and are significant above an absorbed dose of 60 Grays (Gy). Intensity-modulated radiation therapy (IMRT) can help to reduce the side-effects of radiation by producing a custom tailored radiation dose that maximises dose to the tumour while also minimising the dose to adjacent normal tissues. IMRT allows for the radiation dose to conform more precisely to the 3D shape of the tumour by modulating or controlling the intensity of the radiation beam in multiple small volumes. IMRT also allows higher radiation doses to be focused to regions within the tumour while minimising the dose to surrounding normal critical structures. Treatment is carefully planned by using 3D computed tomography or magnetic resonance images of the patient in conjunction with computerised dose calculations to determine the dose intensity pattern that will best conform to the tumour shape. The disadvantages of IMRT are apparent; it is not only more complex to plan and deliver but is much more costly. None the less, the advantages of IMRT are such that it is increasingly used for delivery of head and neck radiotherapy.

Mucositis

Mucositis is a particularly distressing and painful condition arising from damage to the oral mucosal lining. It presents as a widespread oral erythema, pain, bleeding and ulceration. Oral mucositis is a common and often debilitating complication of cancer treatment. The symptoms of mucositis may occur during the second or third week of radiation therapy. The symptoms are common, temporary and gradually subside within two or three weeks of completing treatment.

Xerostomia

Xerostomia is defined as a dry mouth resulting from reduced or absent saliva flow. Xerostomia is not a disease, but it may be a symptom of various medical conditions, and is a side effect of radiation to the head and neck (Fig. 1). Xerostomia is accountable for the most common long-standing problems following orofacial radiotherapy. Salivary flow is reduced from the first week of radiation treatment and this may result in long-term or permanently dry mouth. Xerostomia is particularly severe when both parotid glands are in the radiotherapy field.

Figure 1
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Xerostomia due to radiotherapy

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The Challacombe Scale is a clinical oral dryness score which was developed from research conducted at King's College London Dental Institute and its purpose is to visually identify and quantify xerostomia. It uses a simple numeric system which enables the clinician to quantify the severity of the xerostomia and to decide if the condition needs treatment or not.

The Challacombe Scale works as an additive score of one to ten, with one being the least severe xerostomia and ten being the most severe xerostomia (Table 1). Each of the ten aspects observed scores one point, providing a total score. Symptoms of xerostomia will not necessarily progress in the order listed, but any cumulative score higher than three is likely to be a high-risk patient.

Table 1 Clinical oral dryness score
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Recording the Challacombe for every patient before, during and after radiotherapy is desirable as it can be a great benefit for both the clinician and the patient

Currently the scale is being targeted at all medical professionals who may have to diagnose xerostomia. This will include all members of the dental team, GPs and practice nurses, all care assistants and many more.

Radiation-associated caries

Caries has been seen as an important problem in head and neck radiation patients for many years (Fig. 2). It is well documented that 'radiation caries' can start within three months of the completion of radiation.7,8,9

Figure 2
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Radiation-associated caries

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Head and neck radiation therapy patients are at high risk of developing caries due to the amalgamation of permanent diminution of saliva, high sugar consumption and the high level of cariogenic flora.8

Oral candidal infections

Radiation induced xerostomia can result in increased oral candida counts (thrush). This may persist for several months after treatment, thus increasing susceptibility to candidiasis, particularly when dentures are worn.8

Loss or alteration of taste and weight loss

Many head and neck oncology patients experience problems with swallowing either as a result of surgery (for example, to the tongue or pharynx) or as a result of fibrosis and scarring secondary to radiotherapy. This can result in difficulties or an inability to eat certain foods. A diet consisting of only fluids, pureed or mashed foods may be required. This can result in difficulties with gaining adequate nutritional intake. Patients are subsequently often prescribed high-sugar-containing food supplements to aid in calorie intake and are encouraged to add sugar and fats to foods when possible.

Alteration of taste sensation occurs as a result of the direct effect of radiation on taste buds and due to changes in the saliva. This ranges from the inability to taste (ageusia), decreased ability to taste (hypogeusia) or distorted taste (dysgeusia). Dysgeusia occurs rapidly and exponentially up to 30 Gy, after this taste diminishes at a slower rate until reaching ageusia. Taste acuity is partially restored in 20–60 days after the completion of radiation and in most patients is restored almost completely within four months.10 However, some patients may experience life-long alteration or loss of taste.10 Dysgeusia or ageusia generally causes malaise in patients as they quickly lose interest in food, which may lead to compromised nutritional status and weight loss.

Trismus

Trismus occurs as a side effect of radiotherapy, especially in cases where the tumour invades the muscles of mastication and in cases requiring surgical intervention. Surgery may induce scar tissue which reduces mouth opening due to scar contraction in the muscles of mastication (Fig. 3). Additionally, radiotherapy may induce fibrosis in these muscles as a late radiation effect.11,12,13 Seventy-eight percent of patients experience severe difficulties in mastication following major head and neck surgery with implications for normal social adaptation.14 The most decisive factor in whether trismus develops or not is probably the inclusion of the medial pterygoid muscles in the treatment portals.13 There is some evidence that osteoradionecrosis and trismus risk may be genetically determined by alleles of the TGFß1 gene.15

Figure 3
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Trismus – Patient shown is at maximal opening

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Osteoradionecrosis

Osteoradionecrosis (ORN) is a potential long term and arguably the most serious side effect of radiotherapy (Fig. 4). The definition of osteoradionecrosis is an area of exposed devitalised irradiated bone that fails to heal over a period of three to six months in the absence of local neoplastic disease.16,17,18,19,20

Figure 4
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Osteoradionecrosis (ORN)

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Early presentation of ORN, within two years, is thought to be related to high doses of radiotherapy (>70 Gy) whereas late presentation is usually secondary to trauma and delayed wound healing within compromised tissue.21 Tooth extraction has been considered one of the main risk factors for the development of ORN. The incidence of ORN varies widely in the literature ranging from 1–37%.22 The exact incidence of ORN after post-irradiation extraction is unknown. In general the data showed a downward trend of the risk of developing ORN after extractions in recent years. The incidence of ORN after post-irradiation extractions performed after 1990 was 2%, compared with 16% before then.21 The risk of post-extraction ORN is widely reported to be greater for the mandible compared with the maxilla.21 The pattern of blood supply to the mandible has been implicated as a primary reason for this finding.25 Other more simple explanations claim that the mandible is included in the radiation field more often than the maxilla.

Patients are at particular risk of ORN when:26

  • The total radiation dose exceeded 60 Gy

  • The dose fraction was large with a high number of fractions

  • There is local trauma as the result of a tooth extraction, uncontrolled periodontal disease or an ill-fitting prosthesis

  • The patient is immune-deficient

  • The patient is malnourished

  • Proximity of tumour to bone27

  • Primary site of tumour. Posterior mandible is more commonly affected by ORN because of its compact and dense nature28

  • State of dentition – odontogenic and periodontal disease29

  • Poor oral hygiene29

The oral management of oncology patients before radiotherapy

It is imperative that certain head and neck cancer patients have a pre-radiotherapy assessment before the commencement of any radiotherapy treatment. The pre-radiotherapy assessment must include a radiographic survey for dentate patients and careful clinical assessment of any prosthesis worn by the patient.6 The aim of the pre-radiotherapy dental assessment is to maximise the patients quality of life following oncological treatment. Maximising quality of life may involve retaining teeth for function, aesthetics and speech. Conversely, multiple pre-radiotherapy extractions may be more appropriate to avoid the complication of ORN developing from extracting teeth post-radiotherapy. Where IMRT is to be used, it is essential to arrange the assessment and management of the patient as swiftly as possible to allow the oncologist the maximum time to plan the therapy.

Oral hygiene instruction

The importance of general dental care and oral hygiene, especially for head and neck cancer patients, cannot be over emphasised and a proactive preventative/preventive treatment plan is mandatory. In order to resolve any gingivitis and to maintain a relatively plaque free mouth, dentate patients should use 10 ml of chlorhexidine gluconate mouth rinse at a concentration of 0.2% (Corsodyl) twice daily for a week before radiotherapy and chemotherapy.30,31

Which teeth to extract and timing of extractions

Dental extractions in the field of radiation put patients at risk of ORN and consequently it is advisable to extract teeth with a poor long-term prognosis that will be within the radiotherapy field. All viable teeth should be retained for aesthetics and functional needs, denture stability and maintain quality of life. The less motivated the patient, the more aggressive one should be in extracting teeth before radiotherapy.

It is generally agreed that teeth with a poor prognosis must be extracted before radiotherapy.32 This includes:

  • Advanced caries lesions with questionable pulpal status or pulpal involvement

  • Extensive periapical lesions

  • Moderate or advanced periodontal disease (extensive attachment loss), especially with advanced bone loss and mobility or furcation involvement

  • Residual root tip if not fully covered by alveolar bone or showing radiolucency

  • Impacted or incompletely erupted teeth, particularly third molars that are not fully covered by alveolar bone or that are in contact with the oral environment.16,32,33

The extractions should be performed as atraumatically as possible and with primary closure.34

Ideally, any extractions should be done as soon as possible before radiotherapy starts, however, this is not always practicable due to time constraints. Preferably the extraction should be undertaken up to three weeks before commencement of radiotherapy. If this is not possible then the minimum healing time for the socket before radiotherapy is ten days for maxillary teeth and one week for mandibular teeth.30,31

Restorative treatment

The effects of irradiation and chemotherapy make the soft tissues very susceptible to trauma. It is therefore important to make sure that all irregular teeth and sharp areas on restorations are smoothed down and dentures suitably adjusted to avoid irritation.6 Where time permits it is preferable to restore teeth with a permanent restorative material.

The maximum mouth opening (inter-arch or inter-incisal distance) should be measured before radiotherapy is started, and the patient and/or clinician should measure this distance frequently thereafter to ensure it is maintained (Fig. 5). However, growth of the tumour can sometimes restrict mouth opening even before radiotherapy is commenced.

Figure 5
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Therabite measurer

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Appliance wear

When maxillary surgery is to be combined with radiotherapy, an obturator may be an option for rehabilitation of the maxillary defect and this would need to be planned in liaison with the surgical team. Applicator trays may be constructed for dentate or partially dentate patients for fluoride or chlorhexidine gel delivery later in the management process.6 An assessment of the patients existing dentures should be made to ensure that it is not going to cause trauma to the mucosa during radiotherapy. In reality, the majority of patients may stop wearing their dentures during treatment and therefore advice may be required on overcoming potential difficulties when returning to wear the prosthesis.

Summary

Head and neck radiotherapy may result in multiple unpleasant early and late oral side effects, which can impact on general wellbeing and quality of life. Prevention or reduction of these side effects are a matter of increasing importance especially because of the increase in aged and dentate head and neck cancer patients. It is imperative that certain head and neck cancer patients have a pre-radiotherapy dental assessment to help maximise the patient's quality of life following oncological treatment. Additionally the medical complexity of these patients affects dental treatment planning, prioritisation, and timing of dental care and such patients require significant support from the dental team before, during and after radiotherapy. The patient's GDP, in communication with the restorative consultant on the oncology core team, can deliver much of the advice and treatment required. A planned team approach is the most effective way to maintain the oral and dental health of this vulnerable patient group and can also help to minimise some of the inconveniences that these patients face (for example, travel to the core team and the delay that this incurs) and ultimately improve their quality of life.