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Missing teeth are often replaced by fixed or removable prosthodontic appliances to improve masticatory function. However, there have been few studies directly determining the influence of prosthodontic treatment on masticatory function. Our aim was to obtain information on the objective and subjective masticatory function of partially edentulous subjects before and after prosthetic restoration. In this way, the improvement of the masticatory function as a result of the treatment could be quantified. The objective and subjective masticatory function of a group of 15 subjects was determined before and after replacement of an average of 3.1 post-canine teeth. The results were compared with data from a control group of 26 subjects having a complete dentition. The total number of occluding post-canine teeth increased as a result of the prosthodontic treatment, yielding a significantly improved objective masticatory function. The average masticatory performance was found to approach the level of the control group if all occlusal units of the longest posterior side were replaced. Subjects with an incomplete dentition tended to chew predominantly on the side of the longest posterior arch. The average subjective masticatory function improved as a result of the treatment. The appreciation of the masticatory function after treatment was equal to that of the control group, despite an average of 2.7 missing teeth. However, no correlation was found between the additional number of occlusal units and the change in subjective masticatory performance. Rehabilitation of post-canine teeth restores some objective masticatory function and leads to an increased appreciation of the masticatory function, although no correlation was found between the changes in objective and subjective masticatory function.

The masticatory performance of a group of subjects missing on average 5.7 postcanine teeth and of a control group with complete dentitions were compared. There were significant differences in performance between the two groups. Within the patient group the number of occluding units significantly influenced performance. The average number of chewing cycles needed to prepare the food for swallowing was significantly larger for the patient than for the control group. Despite this, subjects in the patient group swallowed, on average, significantly larger food particles. Correlations between chewing performance and the number of chews up to swallowing within each of the two groups did not reach significance. However, combining the data from the two groups and thus increasing the range of chewing performances yielded a highly significant correlation. Subjects with reduced performance needed more chewing cycles before swallowing the food. Significant correlations were also found between chewing performance and the size of the swallowed food; subjects with poor performance swallowed larger particles. The numbers of chewing cycles made to swallow a natural (peanut) and an artificial (Optosil) test food were highly correlated, indicating that both foods are suitable for testing chewing performance.

The impact of loss of teeth on chewing ability was investigated in three groups of patients. One group already had missing teeth replaced by partial dentures, which were taken out during the tests. This group was taken as not being adapted to chew without a complete dentition. A second group had their missing teeth not replaced by partial dentures. During the test they were considered adapted to chew without a complete dentition. A third group had a complete natural dentition and they acted as control group. Tests were carried out regarding chewing ability and swallowing threshold. In addition, a clinical examination was carried out. It was found that the loss of molars significantly reduced chewing performance. Moreover the number of chewing-strokes before swallowing the food-bolus and the mean of the particle size at the point of swallowing were increased. Loss of molars resulted in less positive feelings concerning chewing. Both groups of persons with missing molars showed a similar chewing performance. The group of not adapted patients felt on average more negative about their chewing ability and they indicated more changes in daily activities because of missing teeth.

The perception and significance of dental appearance was investigated in three groups of patients. One group had a missing front tooth replaced by partial dentures, which were taken out during the tests. A second group had some missing (pre-)molars. A third group had a complete natural dentition and they acted as control group. Color photographs of the teeth were made and a clinical examination was carried out. The psychological impact of dental appearance was measured by way of a scale of words with affective connotations. Social impact was assessed by way of changes in daily activities. Dentists and lay-persons were asked to give an opinion of the dental appearance on the basis of the pictures. It was found that a missing front tooth resulted in less positive feelings and more negative feelings and also that this condition affected daily life activities strongly. Missing (pre-)molars caused less of an aesthetic problem. Dentists and lay-persons were quite alike in their appreciation of dental appearance, whereas the respondents themselves had different opinions. An explanation for these differences and their implications for dentists are discussed.

A hypothesis was developed that the impact or importance of oral health problems may be reflected in a person's ability to remember these problems occurring in a given period spontaneously. That means that the recollection should occur on a nonspecific stimulant, i.e. a general question regarding recall of health problems. This hypothesis was first tested on existing data. A representative sample (n = 1622) of the Dutch population was asked to list all the health problems they had experienced the preceding year. Only 13 persons mentioned an oral health problem. From more specific questions on dental matters it appeared that about 15% of the sample had experienced oral health problems in this period. One hundred and forty-six respondents indeed had received dental care because of acute pain. These data indicate that the impact of oral health problems on a person's daily life is small. Otherwise the oral health problem would have been mentioned spontaneously more often. Three possible explanations for this phenomenon are discussed.

A group of 109 subjects received a short questionnaire concerning their general health status. The subjects were invited to recall all the (health) problems experienced in the foregoing 6 months. Every participant in this study had visited the dentist, in the 6 months preceding the investigation, because of a dental problem. If these dental problems were important for the respondents they would recall them spontaneously, when a general question regarding health problems was posed. Only eight subjects mentioned dental problems spontaneously, of which seven concerned "pain-complaints". Only in two cases had the dental complaints been experienced more than 3 months ago. Eighteen respondents said that they could not remember the dental visit or their specific dental problem. Thirteen of these 18 persons visited their dentist because of an aesthetic problem. The results indicate that the impact of (some) dental problems on a person's feeling of being healthy was small. On the other hand, this study shows that the comparability of (most) dental problems and general health problems is limited. A typology of the significance of dental problems for the public and comparability with the concept of general health is presented and discussed in this study.