12 swallowed. If mastication is compromised, tougher foods are more difficult to process because they require a higher muscle force and more chewing cycles.28 Therefore, some patients switch their diet to softer foods, because the muscle force needed to break down food is too high. This can negatively affect orofacial muscle tonus or even nutritional status.2,8 Malnutrition is defined as a state of nutrition in which a deficiency of energy, protein and other nutrients cause measurable adverse effects on tissue and body form.29 Malnutrition can result in a higher morbidity, mortality, and care costs, because these patients are at a higher risk to develop diseases and infections, caused by the negative impact on the immune response.24,30 Surgical resection of the soft palate, floor of mouth, or base of tongue can cause severe problems by compromising lingual mobility, muscle strength, mastication, swallowing, muscle action, and muscle coordination.31-33 Surgery of the larynx (laryngectomy) is the optimal therapy for advanced stage IV local disease, resulting in severe effects on swallowing and speech. Over 40% of postoperative patients may experience subjective dysphagia in long term follow-up.34 Dysphagia is a significant toxicity resulting in difficulty in swallowing, caused by abnormalities in structure or function of cartilaginous, bony, muscular or neural anatomy involved in normal swallowing.33 Dysfunction of the pharynx can lead to impaired swallow initiation, ineffective bolus propulsion, and retention of a portion of the bolus in the pharynx after swallowing.25 In addition, patients need to re-learn how to speak after a laryngectomy, for example by using esophageal speech, pneumatic speech, tracheoesophageal speech, or an electrolarynx. Similarly to masticatory problems, swallowing problems may also affect nutritional status, because a change in diet is often recommended when swallowing problems occur, by changing the consistency of liquids and/or food in order to prevent dysphagia.24 Toxicity after radiotherapy and chemo radiation Radiotherapy of the oral cavity may result in acute effects such as pain, mucositis, dermatitis, a decrease in saliva production, or edema.3,35,36 RT can also lead to necrosis of irradiated bone, resulting in osteoradionecrosis of the jaw.3 To prevent this, some teeth may need to be extracted pre-treatment.3 Loss of teeth reduces masticatory performance, as chewing can be prolonged, and particle size of the bolus becomes larger due to lower efficiency of mastication.25 Saliva is needed to moisten the food, bind the particles into a bolus and transport the bolus. In addition, it dilutes flavor and alters food consistency during mastication.37 Salivary glands are particularly sensitive to ionizing radiation, with doses to the parotid gland between 28 and 39 Gy leading to a 50% complication probability.38 Doses
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