Relationship between Oral Sensitivity and Masticatory Performance

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Relationship between Oral Sensitivity and Masticatory Performance
2004
L. Engelen1,2,*, A. van der Bilt2, and F. Bosman2
Journal of Dental Research

© 2004 International and American Associations for Dental Research

1 Wageningen Centre for Food Sciences, 6700 AN Wageningen, the Netherlands; and
2 Department of Head and Neck, Oral Physiology Group, University Medical Centre Utrecht, PO Box 85060, 3508 AB Utrecht, the Netherlands;

* corresponding author, l.engelen@med.uu.nl

ABSTRACT

The size of a bolus determines how it will be manipulated in the mouth and swallowed. We hypothesized that mucosal sensitivity would be important for masticatory function. The accuracy of solid object size perception, spatial acuity, and food particle size reduction during mastication were measured in 22 healthy adults with/without topical anesthesia of their oral mucosa. Topical anesthesia had no effect on the perception of sphere sizes, but significantly reduced spatial sensitivity. Without anesthesia, there was a correlation between an individualÌs ability to perceive the sizes of steel spheres (diameter, 4Ò9 mm) and the sizes of food particles chewed for 15 cycles and at swallowing. There was no correlation between spatial sensitivity and food particle size. We suggest that the stimuli used to test two-point discrimination stimulates only superficial receptors, which involve light touch and are easily anesthetized, while the spheres might excite more deeply-set receptors. The latter appear to be more important for masticatory performance and swallowing.


KEY WORDS: oral sensitivity Ô human Ô size perception Ô topical anesthesia Ô masticatory performance

INTRODUCTION

Sensitivity of the mouth includes the ability to assess shape, size, and surface texture. Oral sensitivity has often been measured to track damage and rehabilitation after strokes (Pow et al., 2001), prosthodontic treatment (Berry and Mahood, 1966; Muller et al., 1995), and for speech disorders (Speirs and Maktabi, 1990). Various methods to measure oral sensitivity have been used, including oral form recognition (Berry and Mahood, 1966; Litvak et al., 1971; Landt and Fransson, 1975; Grasso and Catalanotto, 1979; Garrett et al., 1994), interdental size and weight discrimination tests (Williams and La Pointe, 1972), intra-oral size judgments of small holes (Anstis and Loizos, 1967; Lamey et al., 1996; Bittern and Orchardson, 2000; Melvin and Orchardson, 2001), cylinders (Dellow et al., 1970), spheres (Engelen et al., 2002), and two-point discrimination (Ringel and Ewanowski, 1965). The last-named method has been standard since the 1860s and remains the most commonly used method for determining a subjectÌs tactile spatial resolution.

Information on the significance of various oral components in oral size perception and sensitivity is required if we are to understand their role in controlling mastication and swallowing. In the present study, we were specifically interested in oral sensitivity to size. Size can be sensed by pressure and stretch receptors in tongue and palate mucosa, in addition to mechanoreceptors in the periodontal ligament (Jacobs and van Steenberghe, 1994). Oral perception of size does not depend on the density or material of an object, but solely on its actual size and shape, and results from a combination of sensory inputs from the tongue and palate (Engelen et al., 2002). In the present study, we excluded input from the superficial layers of mucosa by applying topical anesthesia to the tongue and palate.

Masticatory function has been studied in various groups of subjects, such as dentate subjects (van der Bilt et al., 1994), partial- and complete-denture wearers (Slagter et al., 1993), and subjects with implant-retained overdentures (Fontijn-Tekamp et al., 2000). Masticatory performance is significantly reduced when dentures replace natural teeth. The most common way to study masticatory function is to determine an individualÌs capacity to grind or pulverize a test food by analyzing the chewed material (Lucas and Luke, 1983). For safe swallowing to be ensured, the particle sizes in the bolus of the chewed food need to be detected. It has been suggested that the main site for detecting food particles is not between the teeth, but on oral mucosa (Prinz and Lucas, 1995). In addition, tongue motor skill is significantly correlated with masticatory performance (Koshino et al., 1997). Thus, information from oral mucosa, e.g., oral sensitivity, may be related to measurements of masticatory performance. If median swallowing particle size is related to oneÌs ability to assess objective size, the question arises whether a subject with good discriminative abilities also chooses to swallow smaller particles.

The aim of the present study was three-fold: First, we were interested in how size is perceived in the mouth and whether oneÌs ability to assess size is related to spatial sensitivity. Second, we studied how these features are influenced by topical anesthesia. Finally, we wanted to study how the median particle size at swallowing and masticatory performance are related to the subjectÌs ability to assess the sizes of objects and sensitivity in the mouth.

We hypothesized that topical anesthesia would affect oral perception of size and spatial acuity, and that the particle size at swallowing would depend on oral mucosal sensitivity.

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