The effects of gradually induced backward movement of the mandible by a Twin Inclined Plane Device in rats

Abstract

Objective: To develop a model of gradually induced backward movement of the mandible under normal masticatory action and to examine morphological changes in the mandible and condylar cartilage in rats. Materials and Methods: The newly developed Twin Inclined Plane Device (TIPD) was composed of upper and lower posterior metal crowns with a long inclined plane on both sides separately and was applied in experimental groups of 6-week-old male Wister rats. After 3, 14, 30, and 60 days, the rats were euthanatized and samples were collected. Various measurements and hematoxylinand-eosin stains were performed. Results: From day 30 on, the length of the condylar process was shorter in the TIPD groups than in the control groups (P , .05). The angulation of the condylar process axis to the mandibular plane was greater in the TIPD groups (P , .01). The thickness of the condylar cartilage in the posterior part of the posterior region was thinner in the TIPD groups (P , .05) on day 30 and even thinner (P , .01) on day 60; from day 30 on, the thickness in the anterior part of the posterior region was thicker in the TIPD groups (P , .01). Conclusion: TIPD can successfully induce backward movement of the mandible under normal masticatory action. TIPD can cause region-specific changes in condylar cartilage and leads to a continuous remodeling. (Angle Orthod. 2012;82:839-845.)

Three-Dimensional Analysis of Posterior Mandibular Displacement in Rats

“…Asano appears to have faced the same challenge in highlighting similar landmarks [ 57 ]. Such developmental restriction is in agreement with the observations of Desai et al [ 62 ] and Cholasueksa et al [ 8 ], and the conclusions of Asano [ 57 ], Farias-Neto et al [ 81 ], and Hua et al [ 82 ].…”

“…It was introduced by Desai et al [ 62 ], although their research did not report many details on osseous mandibular change, but focused mainly on the temporomandibular joint. It was adopted by Cholasueksa et al [ 8 ] and Farias-Neto et al [ 81 ], whereas Hua et al [ 82 ] and Wang et al [ 59 ] used modified upper/lower devices, unlike Asano [ 57 ], Tsolakis [ 15 ] and Teramoto et al [ 10 ], who selected extra-oral appliances. Teramoto et al mention that the magnitude of the traction was excessive, and thus ended up traumatic [ 10 ].…”

“…In addition, the oblique osseous and dento-osseous measurements, as depicted by Coronoid–Menton, Condylion–Menton, Condylion–Id, were also found to be significantly different. Interestingly, Hua et al found their respective oblique measurement, namely the angle between the axis of the condylar process to the mandibular plane, also changing spatial orientation [ 82 ].…”

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

“…The horizontal component of the chewing force, F s, is transmitted to the posterior region of the condyle (Figure 1(a)). Therefore, the posterior region was determined as the focus of the present study [14]. The expression of VEGF (Figure 2(c)), type II collagen (Figure 2(d)), and osteoclasts (Figure 2(e)) was semiquantified using an Olympus DP72 microscope (Olympus DP72 microscope, Olympus Corporation, Japan) and the Image-pro plus 6.0 software (Media Cybernetics, USA).…”

“…In addition, it was found that the posterior margin of the condyle was significantly flattened after the TIPD treatment. It was speculated that TIPD can cause persistent remolding in the posterior region of the condylar cartilage [14]. However, the condylar changes in rats, which trigger the mechanism, remain unclear.…”