Alterations in the gustatory papillae after anterior bite plate insertion in growing rats

Abstract

Objectives: To determine whether the modification of dental occlusion, without molar extraction, affected the gustatory papillae located in the tongue of growing rats.

Materials and methods: Five-week-old male Wistar rats were randomly divided into an anterior bite plate (ABP) group and a control group. Under general anesthesia, ABPs were placed on the occlusal surfaces of the maxillary incisors, while metal caps covered the mandibular incisal edges of the rats in the ABP group. The control group rats underwent a sham operation. The rats in both groups were euthanized 14 days after the procedure. The circumvallate papillae and taste buds were analyzed by immunohistochemical methods, and the fungiform papillae were observed and counted after immersion of the tongue in 1% methylene blue.

Results: Two weeks after ABP insertion and mandibular incisal cap placement, the gustatory papillae exhibited morphological and structural changes. The rats in the ABP group had exhibited significantly fewer fungiform papillae, and narrower circumvallate papillae, with greater trench depths, larger trench profile areas, smaller taste bud profile areas, lower ratios of the taste bud profile area to the trench profile area, and more taste buds than those in the control group.

Conclusions: Our findings support the association between occlusal and taste functions and provide a basis for further studies on the gustatory function. In conclusion, loss of molar occlusion, resulting from the ABP and metal cap insertion, altered the peripheral gustatory receptors in the growing rats.

Keywords: Growing rat; gustatory papillae; occlusion; taste.

Figure 1

Schematic drawing of the rat tongue. The dotted line depicts the division of the tongue into laryngeal and apical tongue segments

Figure 2

Assessment methods of fungiform and circumvallate papillae. (a) Arrowheads showing fungiform papillae. Scale bar: 1 mm. (b) Horizontal line defining circumvallate papilla width. Short arrows representing keratinized epithelium thicknesses. Vertical lines indicating trench depths. (c) Arrowheads indicating “trench openings.” Outlines illustrating trench areas. (d) Circles delimit taste bud areas. Scale bar: 100 μm

Figure 3

Changes after anterior bite plate insertion in rats. (a) Body weight trend. (b) Fungiform papillae numbers after anterior bite plate insertion. (c-f) Circumvallate papilla width, trench depth, and keratinized epithelium thickness (c), trench and taste bud areas (d), taste bud area to trench area ratios (e), taste bud numbers per trench (f). *P < 0.05, **P < 0.01, NS: Not significant

Figure 4

Methylene-blue-stained dorsal surfaces of the rat tongue obtained from control (a) and experimental rats (b). The black arrowheads indicate the fungiform papillae. Scale bar: 1 mm

Figure 5

Rat circumvallate papillae immunoreactive for cytokeratin 8 and counterstained with hematoxylin in the control (a) and experimental groups (b). An atypical ectopic taste bud (black arrowhead in b). Scale bar: 100 μm