Journal of Oral Rehabilitation 2000 27; 142 – 148 The post-orthodontic prevalence of temporomandibular disorder and functional occlusion contacts in surgical and non-surgical cases A. MILOSEVIC* & R. H. A. SAMUELS † *Department of Clinical Dental Sciences, Academic Unit of Restorative Dentistry, University of Liverpool, Liverpool and † Department of Orthodontics and Restorative Dentistry, The Glenfield Hospital, Leicester, U.K. occlusal contacts were not different between surgi- SUMMARY This study aimed to assess mandibular mobility and the prevalence of functional occlusal cal and non-surgical groups. Non-working side con- tacts occurred in 30% of subjects, posterior contacts contacts in subjects treated to a Class 1 incisor relationship by fixed orthodontic appliance ther- on protrusion in 20% and RCP-ICP prematurities in 18% of subjects. Non-working side contacts were apy. Two hundred and thirty subjects participated (mean age =18 years) of whom 42 underwent or- significantly more frequent in post-graduate cases compared to staff cases (P 0·05). An overbite less thognathic surgery. All subjects were in retention than the mean of 2·4 mm resulted in a reduced with a mean time of 7 months between debond and examination. Maximal mandibular opening, lateral likelihood of canine guidance on the working side (P 0·001) and an increased frequency of non-work- and protrusive excursions were all significantly re- ing side contacts and posterior contacts on protru- duced in the surgical cases compared to the non- surgical group. Centric and eccentric non-ideal sion (P 0·001). Introduction The relationship between malocclusion and temporo- mandibular disorder (TMD) has been investigated widely since the medico-legal case described by Pollack (1988). Several researchers have reported a low preva- lence of severe mandibular dysfunction in orthodonti- cally assessed and treated subjects. The assessment of TMJ function has generally been made with the Helkimo indices of mandibular dysfunction and mandibular mobility. However, the dynamic or func- tional occlusal relationships are also important in pro- moting stomatognathic harmony. The ‘ideal’ dynamic occlusal relationships are controversial and broadly fall into supporters of a mutually protected occlusion (MPO) or supporters of a balanced occlusion and on the working side, canine guidance versus group func- tion (Mohl & Davidson, 1988; Ingervall, Ha ¨hner & Kessi, 1991). Mutual protection refers to intercuspal contact of posterior teeth but not the anterior teeth which on protrusion or lateral excursion disclude the posterior teeth. Moreover, an antero-posterior slide from retruded contact position (RCP) to intercuspal position (ICP) of no more than 1 mm without lateral deviation and the absence of non-working side con- tacts are regarded as desirable (Dawson, 1989). The working side may be canine guided (cuspid protected) or, when several teeth contact, there is group function. Terms such as balancing side should not be used in dentate subjects, since this is a prosthetic concept used to gain complete denture stability. Most of the studies on functional occlusion in or- thodontic subjects emanate from the U.S.A. Non-work- ing side contacts (unilateral balanced) occurred in 38% of orthodontic cases with extractions compared to only 12% in cases treated without extractions and 22% of the controls. Furthermore, the majority of these con- tacts occurred on the second molars (Rinchuse & Sas- souni, 1983). The prevalence of non-working side and © 2000 Blackwell Science Ltd 142