Morphological Changes in the Mandible of Male Mice Associated With Aging and Biomechanical Stimulus

Abstract

Degenerative changes in the temporomandibular joint (TMJ) associated with aging can affect mandibular shape and reduce growth potential when stimulated by functional appliance therapy. This study was designed to evaluate the morphological changes in the mandibles of male mice associated with aging and biomechanical stimulus. Every 3 days over the course of 1 month, the lower incisors were trimmed by 1 mm to induce mandibular advancement (MA) when the animal was feeding. The left mandibles of the 23 experimental and 27 control animals were subsequently dissected, and digital images were obtained to analyze nine linear/angular measurements. Because mandibular morphology depends on the maintenance of condylar cartilage, the surfaces of the condylar cartilage and the ascending ramus of the mandible were also analyzed by scanning electron microscopy (SEM). The linear measurements of the mandible showed changes according to age in the control group and a growth response in the mandibular condyle in 7-and 15-month-old mice after MA. Moreover, SEM analysis revealed depressions in the anterior region of the condylar cartilage and inclined vascular grooves in the ascending ramus in the 7-and 15-month-old experimental mice. Although the growth potential is reduced in mice after 6 months of age, the results showed that continuous growth of the mandible occurs after maturation, except in the condyle, and that biomechanical stimulus of the TMJ of male mice leads to condylar growth. These results suggest that mature and old individuals can favorably respond to maxillary functional orthopedic therapy.

Effects of growth hormone and functional appliance on mandibular growth in an adolescent rat model

“…Male rats have also been used in previous studies on bone development because estrogen may potentially affect bone density. 21 However, mandibular advancement therapy is often used before the growth spurt, during which the level of estrogen does not differ significantly between genders. Therefore, female rats have also been used for research on mandibular growth in previous publications, 3,4,14 as well as in the current study.…”

Mathematical Analysis of Mandibular Morphogenesis by Micro‐CT‐Based Mouse and Alizarin Red S‐Stained‐Based Human Studies During Development

“…This study has shown not only age-related but also stress-related changes in the morphological characteristics of the mandible. Many studies have been published regarding the morphological changes of the mandible during normal development (Bodner et al, 1998;Franchi et al, 2001;Lee et al, 2001;Ramaesh and Bard, 2003;Radlanski et al, 2003;Monteiro and Reis, 2005;Tagliaro et al, 2006Tagliaro et al, , 2009Pessa et al, 2008;Leamy et al, 2008). However, it remains unclear how to precisely detect abnormal morphology.…”

Bilateral asymmetry favours the left hemimandibular side in companion rabbits

“…All these points were chosen according to their potential accuracy of digitization and because points were homologous through the structures, furthermore they would represent the mandible and its parts as good as possible: the mandible body ( corpus mandibulae, horizontal part, landmarks 1 to 5, and 15 to 18, these latter utilizing perpendicular projected points on the ventral border in relation to dental position, and 1, 4 and 5 recorded at the alveolar edges adjacent to the teeth) and ramus (ramus mandibulae, vertical part, landmarks 6 to 14). The chosen landmark configurations occupy different regions of the theoretical morphology defined by mandibular apparatus (11). No differences according to coat were considered.…”