Histological study of rat masseter muscle following experimental occlusal alteration

Abstract

It has been suggested that occlusal interference results in masticatory muscle dysfunction. In our previous study, occlusal interference reduced the rat masseter energy level during masticatory movements. The purpose of this study was to investigate the histological alterations of rat masseter muscles following experimental occlusal alteration with unilateral bite-raising. A total of eight male adult Wistar rats were equally divided into control and experimental groups. The experimental rats wore bite-raising splints on the unilateral upper molar. However, 4 weeks after the operation, the anterior deep masseter muscles were removed and then stained for succinic acid dehydrogenase (SDH), haematoxylin eosin (HE) and myofibrillar ATPase. Most of the muscle fibres in experimental rats remained intact, although partial histological changes were observed, such as extended connective tissue, appearance of inflammatory cells in the muscle fibres and existence of muscle fibres with central nuclei and central cores. Moreover, the fibre area-fibre frequency histograms of experimental muscle indicated a broad pattern than that of controls. These results indicated that occlusal interference caused histological changes in masseter muscles and that this may be related to the fact that the masseter energy level was reduced during masticatory movements in unilateral bite-raised rats.

Ultrastructural and biochemical changes of the medial pterygoid muscle induced by unilateral exodontia

“…Nevertheless, controversial opinions still exist on specific roles of different muscular alterations appearing during treatment with functional orthodontic appliances (Eckardt et al, 2001). Unilateral occlusal alterations in animal experimental models have shown adaptation of the masseter muscle caused by unilateral exodontias (Maeda et al, 1990), by unilateral occlusal abrasion (Bani et al, 1999;Bani and Bergamini, 2002), or by insertion of an unilateral occlusal splint (Muller et al, 2000;Nishide et al, 2001). However, physiopathological mechanisms of muscular adaptation are still poorly understood and studies related to pathways to morphofunctional changes are scarce (Gendrage et al, 2003) in special on medial pterygoid muscle.…”

Morphological and histological effects on the medial pterygoid muscle after unilateral exodontia in gerbils

“…These alterations, which occur at macroscopic (Miehe et al, 1999), microscopic (Nishide et al, 2001) and ultrastructural levels (Bani et al, 1999;Bani and Bergamini, 2002) are different for each occlusal-induced alteration. Morphofunctional aspects of the medial pterygoid muscle, as well as its relationship with occlusal alterations are scarcely reported although the muscle has an important function in the stomatognathic system.…”

Expression of respiratory chain enzyme mRNA and the morphological properties of mitochondria in the masseter muscles of klotho mutant mice

“…Additionally, the concentrations of mitochondria-encoded mRNAs found in skeletal muscle also decrease as an animal ages (Barazzoni et al, 2000;Welle et al, 2000Welle et al, , 2003. In contrast, the masseter muscle displays specific profiles for the various enzymes (cytochromes b, c, c1, a, and a3; ATP synthase; and succinate and NADH dehydrogenases) (Guelinckx et al, 1986;Kiliaridis et al, 1988;Easton and Carlson, 1990; Miyata et al, 1993;Miehe et al, 1999;Nishide et al, 2001). In rat heart muscle, the activities of NADH-dehydrogenase and the ATP synthase are reduced, as is the capacity for oxygen utilization and ATP synthesis (Preston et al, 2008); however, there is no reduction in mitochondrial integral membrane protein during aging (Navarro and Boveris, 2007) and no change in ATPase activity in the liver, heart, or skeletal muscle (Barogi et al, 1995).…”