The treatment of severe 'gummy' Class II division 1 malocclusion using the maxillary intrusion splint

This paper describes a modified Maxillary Intrusion Splint (M.I.S.) system which incorporates a near vertical pull headgear, and its use in the management of severe 'gummy' Class II division 1 malocclusion. The appliance was designed to reduce the visibility and vulnerability of the maxillary incisors in this difficult clinical situation by achieving the intrusion of maxillary teeth, restraining maxillary growth, and encouraging an element of subsequent forward mandibular rotation. The authors' initial experience using this system is presented in a retrospective cephalometric analysis of the lateral skull films of 26 treated patients contrasted with a similar number of comparable controls. The results showed that the principal effects of the M.I.S. were on the maxillary teeth giving decisive overjet control and incisor retraction with actual maxillary incisor intrusion. There was a similar effect on the maxillary molar and the M.I.S. provided effective en masse vertical control of the maxillary dentition. There was some degree of maxillary restraint in the M.I.S. group, but no noticeable difference in the change of mandibular position between the groups at the end of treatment. The possible reasons for this are discussed and suggestions made to improve this aspect of treatment in these patients.