ABSTRACT

This study is intended to review previous case reports on identical twins treated differently and to demonstrate the effects of two different treatment modalities on a pair of 11-year-old identical twin boys with dental Class III malocclusion and hyperdivergent face type. The identical twins had dental Class III malocclusion with significantly increased SN/GoGn angle and negative overjet, although they presented skeletal borderline Class II malocclusion. Twin no 1 was treated by chin cup and mandibular 2 by 4 fixed Edgewise mechanics while; Twin no 2 was treated by face mask. The negative overjet, in both brothers, was eliminated and a significant improvement in facial esthetics and function was achieved. While the mandibular rotation was controlled with an occipital-pull chin cup, posterior mandibular rotation was observed in the face mask treatment protocol. For retention, Twin no 1 is wearing his chin cup 1 and Twin no 2 is wearing his face mask during night time. Twin studies are one of the most important tools to evaluate the interaction between genetic and environmental factors, but growth trends of the twins and their responses to different treatment modalities still carry individuality.