Dental and skeletal changes after intra-oral molar distalization using a “Distal Driver” appliance: a pilot study

Abstract

Introduction. Loss of space in the maxillary arch is a frequent consequence of early loss of deciduous molars indicating distalisation of the mesialised molar tooth. A number of methods using either extra-oral appliances or intra oral appliances of various types have been suggested. While extra-oral appliances exert a high but intermittent force many of the intraoral ones deliver a modest, though constant, force and demands no patient cooperation. Aim of study. To investigate the effect of an intra-oral fixed appliance (Distal Driver) based on a NiTi spring incorporating also a standardised anchorage unit on the position of the maxillary first molar as well as on the facial skeleton and the dentition in general. Material and methods. The experimental group comprised 6 child patients exhibiting a distal molar relationship (Unilateral or Bilateral) of at least ½ premolar unit. The mesialised molars were distalised by means of a “Distal driver” exerting a force of 150 gm for a period of 3-4 weeks. Anchorage was created by a fixed modified palatal bar cemented on the premolars supporting an acrylic palatal button ad modum Nance. The clinical situation was recorded before and after molar distalisation by means of study casts, cephalograms, panoramic radiographs as well as intra-oral photographs. The distalisation of the molars as well as the effect on anchorage teeth was quantitated on digital models derived from the plaster casts. Evaluation of the observed distal and vertical changes in molar position was performed on the lateral cephalogram. Results. Cast analysis showed a clear distalising effect on the maxillary first molars ranging from 1.25 mm to 6.18 mm as well as mesial movement of the premolar anchorage teeth from 0.46 mm to 5.55mm. The cephalometric analysis revealed a first molar distalisation of 0.9 mm to 5.6 mm though again with a mesial movement of the first premolar varying from 0.5 mm to 3.7 mm. A clear distal tipping of the first and second molars simultaneously with a mesial tipping of the first premolars was also recorded. Conclusion. The Distal Driver constitutes an efficient method of maxillary molar distalisation though is often accompanied by a distal rotation of these teeth and a mesial tipping of the anchorage premolars. Careful monitoring of anchorage loss is necessary if good results are to be achieved.