Factors Affecting Mandibular Growth and Displacement and Their Effect on Treatment Outcome

Abstract

Orthodontists often have difficulty distinguishing between growth and displacement when it comes to the mandible and often the two are merged into one and referred to as just mandibular growth. It is clinically important to distinguish between the two as it can greatly affect the choice of treatment protocol and mechanics. In this review we shall attempt to clarify the issue with clinical examples in the hope of bringing more understanding to the problem. Controlling the factors that are involved in determining the outcome of orthodontic treatment in a growing patient can often be a difficult task and is affected by the stage of maturation. This is particularly problematic if the patient is in a slow growth phase. In some instances, this has led to the unfortunate conclusion that early or interceptive treatment is a waste of time and not only has it caused frustration for the clinician and family but also as it may result in extra cost when two phases of treatment may be needed to correct the malocclusion. With a better understanding of the factors that determine growth and displacement of the mandible better choices of treatment time and mechanics can be made and the correction of a particular malocclusion can be more successful. In the following we shall discuss the factors that affect mandibular displacement and how growth and orthodontic tooth movement affect the outcome. We shall show examples of patients where the lack of adequate condylar growth results in unfavorable displacement of the chin and others where pronounced forward displacement of the chin is the result of excessive condylar growth. We shall further discuss the role of vertical control in cases where the inherited mandibular growth pattern does not favor forward mandibular growth.