Effects of Twin Inclined Plane Device on Adaptation and Ultrastructure Variations in Condyle of Growing Rats

Abstract

Objective This study investigates the effects of using a twin inclined plane device (TIPD) on the remolding and ultrastructure variation of mandibular condyle in growing rats. Materials and Methods Forty-eight male Wistar rats (six weeks old, body weight of approximately 190–210 g) were divided into experimental group (wearing appliance, n = 32) and control group (no appliance, n = 16). Samples were collected on days 3, 14, 30, and 60. The immunohistochemical analysis for vascular endothelial growth factor (VEGF) and type II collagen was carried out. Tartrate-resistant acid phosphatase (TRAP) reaction was performed to evaluate the osteoclastic activity. Three-dimensional morphometric images were reconstructed for morphometric analysis by microcomputed tomography (micro-CT). The ultrastructure of the condylar surface was observed by scanning electron microscopy (SEM). Results The expression of VEGF significantly increased, while the expression of type II collagen decreased in the experimental group at days 30 and 60. Furthermore, the enhanced osteoclast activity was observed under the subchondral bone, which was highest at day 30, and decreased to the lowest at day 60 in the experimental group. In addition, adaptive subchondral bone remolding in the posterior part of the condyle was observed at day 60 in the experimental group, and the SEM revealed the ultrastructure variations after installation of the TIPD. However, these changes began to reverse after 30 days. Conclusion Condylar tissue changes point to the osteoclastic activity in the posterior region of the condyle. These adaptive changes point to bone resorption in the posterior condyle. Type II collagen and VEGF contribute to the MCC remolding induced by the TIPD. The ultrastructural changes in the posterior condylar area in response to mechanical stresses are recoverable at the initial stage.

Posterior Mandibular Displacement—A Systematic Review Based on Animal Studies

“…From the remaining 12 studies, 5 were excluded, due to absence of radiologic macroscopic data following posterior displacement of the mandible. Finally, 7 full-text records comprised the systematic review [ 12 , 16 , 18 , 42 , 44 , 59 , 60 ].…”

“…Orthodontic/orthopedic treatment was induced by adapting intraoral or/and extraoral appliances. Orthopedic collar appliances were used by Asano [ 59 ], Desai et al [ 44 ] cemented castings on maxillary incisors, Teramoto et al [ 18 ] manufactured a collar from acrylic plate and rubber band connected to the mandibular incisors with wire jig and coil, and occlusal guiding appliances were attached to the maxillary incisors by Cholasueksa et al [ 16 ] and by Farias-Neto et al [ 12 ], while both Hua et al [ 60 ] and Wang et al [ 42 ] introduced a twin inclined plane device.…”

“…The outcomes of the risk of bias assessment are summarized in Table 2 . Four studies were deemed as being of high [ 18 , 42 , 44 , 59 ], and three of unclear risk of bias [ 12 , 16 , 60 ]. Regarding allocation sequence, four of them were found to be of high risk of bias, while unclear risk of bias was detected for the rest of them.…”

“…Eventually, the decrease in mandibular length in experimental animals was attributed to the remodeling of the condyle [ 60 ]. Ultimately, Wang et al [ 42 ] found in the rat that a twin inclined device resulting in posterior mandibular displacement may lead to adaptive bone resorption at the posterior region of the condyle. In their control group, the posterior margins of the condylar bone remained round, whereas in the experimental group the lower part of the posterior margin of the condyle appeared significantly flattened by the end of the observation period as highlighted by 3D reconstruction [ 42 ].…”

“…Customary mastication consists a physiological stress to the TMJ, of great importance for its development in adolescence and the remodeling in adulthood [ 41 ]. The lateral condylar displacement in the glenoid fossa as observed in the therapeutic approach of skeletal discrepancies may culminate in abnormal loading of adjacent structures, affecting the physiologic dynamics of condylar cartilage and triggering the release of growth factors [ 19 , 42 ] and inflammatory mediators [ 43 ], to unknown extent and of unspecified clinical significance, a long-standing controversy.…”