Posterior Mandibular Displacement—A Systematic Review Based on Animal Studies

Abstract

Treating extreme mandibular growth is challenging. The mandible is pushed backwards to address itsprotrusion. Nevertheless, conclusions after such displacement in animals have been contradictory. The aim of the present review is to present measurable alterations of the mandible and the condyle following retractionin healthy rats or rabbits. PubMed, Scopus and Web of Science were accessed for relevant studies up to October 2020. Eligibility was determined by the PICOS process, while the risk of bias was estimated with SYRCLE’s risk of bias tool. Retraction resulted in a more distal molar occlusion and the condyle rested more posteriorly. Mandibular anteroposterior bilateral growth restriction was achieved, the condylar process measured smaller and its angulation increased. The condylar neck thickened, its posterior surface flattened, the coronoid process was measured longer, and enlarged retromolar density was registered. Differences in the ramus height and the intercondylar distance were insignificant. Changes persisted for the period of study and subsequently the mandible resumed its inherited growth pattern. The timing of mandibular shaping and TMJ outcomes might depend on the properties of the applied force. Stability is of concern and well-structured, long-term studies are expected to resolve the issue and further clarify the results of posterior mandibular displacement.

Anterior Mandibular Displacement in Growing Rats—A Systematic Review

“…There is the possibility of having to surpass a certain threshold to achieve a response of the bone [ 8 , 39 ]. On the other hand posterior displacement of the mandible in rats affects bone modeling under a minimum strain threshold that controls mandibular growth [ 40 , 41 ].…”

Three-Dimensional Analysis of Posterior Mandibular Displacement in Rats

“…It would be interesting to assess the osseous alterations effected by an intraoral device causing distal mandibular displacement and, potentially, growth restriction on the molecular or cellular level [ 8 , 9 , 10 , 11 ]. Despite the fact that such appliances were introduced early in the 20th century [ 12 ], the exact skeletal effect of the loading is still elusive, and it has been the subject of a recent systematic review [ 13 ]. Understanding the pathway of bone remodeling may have repercussions on treatment planning and the stability of the intervention.…”