Effect of occlusal functional forces on incisor socket morphology and location in the rat mandible

Abstract

The effect of functional occlusal stress on dimensional alterations of the rat incisor socket and mandible were studied from roentgenograms. In 12 rats, the lower left incisor was shortened twice weekly, whereas the lower right incisor was allowed to remain in contact with both upper incisors. Thus, the right incisors were subjected to hyperfunction, and the left ones, to hypofunction. The lower incisors of 16 rats with normal occlusal contact served as control. Following an experimental period of 3 months, the animals were killed and standardized radiographs were taken of the cleaned mandibles. Socket and mandibular dimensions were measured on magnified tracings of the roentgenograms. Socket area, its posterior length, posterior mandibular length, and gonial angle changed in the same direction under both hyper- and hypofunction. The anterior socket was relocated in opposite directions: under hyperfunction, it assumed a more inferior position, whereas in hypofunction, it moved superiorly. The angulation of the socket became significantly more acute under hyperfunction, whereas in hypofunction, this parameter remained unchanged. It is concluded that altered functional demands affect the morphology of the incisor socket and its location within the mandibular borders.

A comparison between a conventional optical method and image-analysis for measuring the unimpeded eruption rate of the rat mandibular incisor

“…There are several established methods for measuring the eruption rate of the rat incisor; some involve the taking of measurements over a period of several days (Tsuruta et al 1974), or even weeks (Burn-Murdoch 1995, Risnes et al 1995; another way is to use non-contacting displacement detectors over a period of hours (Chiba et al 1995, Ohyama andYamaguchi 1999). For the taking of measurements over a long time period, the most commonly used method is the optical microscope with a graticule in the eyepiece which produces a direct measurement; other methods include the use of calipers connected to a digital voltmeter , Pitaru et al 1976, Weinreb et al 1985, Michaeli et al 1985, Steigman et al 1988, Brin et al 1990, radiographs (Ness 1954, 1956, 1965, Adams and Main 1962, Main and Adams 1966, Chiba et al 1968, Lavelle 1968, 1969 and photographs (Chiba et al 1973, 1980, Tsuruta et al 1974, Robins and Spicer 1981, Chiba and Ohshima 1985. However, none of the currently used methods is entirely satisfactory.…”

Long-term Effects of Orthodontic Forces on the Morphology of the Rat-incisor Socket and its Location in the Mandible

“…The sequelae of the mechanical forces applied in the present investigation closely resemble the conditions actually existing under excessive occlusal forces, or hyperfunction (Brin et al, 1989), implying that both types of stress trigger a biological process that finds its expression in changes in tooth socket and in mandibular growth.…”

“…Animal studies have revealed retarded eruption (Steigman et al, 1983(Steigman et al, , 1988, as well as structural derangements of the rat incisor and its periodontal ligament (PDL) (Michaeli et al, 1985;Engstrbm and Noren, 1986;Michaeli et al, 1987;Steigman et al, 1987), following force application to teeth. Reports also exist on the adjustment of the continuously erupting incisor, its socket, and mandible to retarded and accelerated eruption (Moxham and Berkovitz, 1981;Brin et al, 1989;Steigman et al, 1989), or to other functional demands (Beecher and Corruccini, 1981;Bondevik, 1984;Kiliaridis et al, 1985;McFadden et al, 1986;Kjellberg et al, 1987). Both elimination and increase of functional occlusal forces were found to induce changes in morphology, dimensions, and location of the socket (Brin et al, 1989).…”

“…Reports also exist on the adjustment of the continuously erupting incisor, its socket, and mandible to retarded and accelerated eruption (Moxham and Berkovitz, 1981;Brin et al, 1989;Steigman et al, 1989), or to other functional demands (Beecher and Corruccini, 1981;Bondevik, 1984;Kiliaridis et al, 1985;McFadden et al, 1986;Kjellberg et al, 1987). Both elimination and increase of functional occlusal forces were found to induce changes in morphology, dimensions, and location of the socket (Brin et al, 1989). Little is known, however, about structural adjustment of the socket following orthodontic force application, particularly when coupled with changed functional demands.…”

Ontogenetic integration between force production and force reception: a case study inCtenomys(Rodentia: Caviomorpha)

“…Similar regulatory effects may be expected from occlusal loading acting upon teeth and mandibular morphogenesis (Brin et al . ). As it was summarized by Kablar (), the key feature that connects the vertebrate skeleton and the musculature appears to be their ability to react to mechanical stimuli, which has important implications for both adaptation and morphogenesis.…”