13 1 over 50 Gy cause irreversible hypofunction and permanent xerostomia.39 When salivary glands are in the RT field, this will negatively affect saliva quantity and quality, exacerbating masticatory problems.25 The submandibular glands are responsible for most of the saliva production (60-65%) in the non-stimulated state,39 and are mainly responsible for flow rate during sleep. Most patients with HNC complain of a dry mouth at night caused by irradiation of the submandibular glands, with 65% of patients having severe complaints 1 year after RT.40 Long term RT damage may consist of fibrosis, periodontal disease, ulcers, or vascular toxicity. These effects can be attributed to hypoxic, hypo-vascular, or hypocellular tissue. RT often leads to fibrotic tissue and hyposalivation, which can also lead to trismus, xerostomia, and radiation-induced caries.41-43 Chemotherapy can add to these effects, because it causes immunosuppression and is not tumor specific but acts on all cells in the body. As a result, patients exhibit acute toxicity with oral manifestations, such as oral mucositis, nausea, vomiting, renal insufficiency, loss of hearing and appetite, cytopenia, xerostomia, neurotoxicity, and stomatotoxicity.37 In addition, it can enhance radiationinduced fibrosis of the muscles and cause edema.35 Irradiation of swallowing related normal tissues may lead to dysphagia, fibrosis, edema, ulcers, vascular toxicity, and osteoradionecrosis.44,45 Complications such as malnutrition, aspiration and subsequent pneumonia can occur.33 Irradiation of swallowing tissues may result in a thick, viscid saliva that impairs deglutition, resulting in significantly longer oral transit times and a delayed swallow initiation, a greater pharyngeal residue and decreased pharyngeal transport, a lower swallowing efficiency, a shorter cricopharyngeal opening duration, and ineffective laryngeal protection.25 This also puts the patient at risk for coughing and aspiration.3 Chemotherapy can add to the effects of RT and cause edema, mucositis and fibrosis of the swallowing structures.33 Food processing measurements To measure food processing, objective and subjective measures can be used. Objective measures are based on how well a person can perform a task, irrespective of what they experience while performing the task. Subjective measures depend on individual values and priorities, and thus reflect a patients’ expectation and personal importance of oral functioning on daily life satisfaction. Objective masticatory performance can be measured with, for example, comminution methods, sieving and optical scanning methods, gummy jelly as test food, and mixing ability methods.46 One method using the mixing ability method (the Mixing Ability Test (MAT)) has