Dentofacial changes after maxilla retraction with zygomatic implant anchorage-a rhesus monkey study

Abstract

Objective To study the dentofacial changes caused by retractive force with zygomatic implant to the maxilla of rhesus monkeys.Methods 4 yound male rhesuses were employed,3 experimented(1 for 1.5 month and 2 for 3 months),and 1 as control.Titanium miniplates were fixed on the bilateral zygomatic bones as an anchorage,the maxillary cast splint was anchored in cisors,second deciduous molars and firsr molars.A retractive force of 150g was exerted on each side with a direction parallel to an occlusal plane.Cephalometric Comparison was analysed between the beginning and the end of experiment.Results A point was moved backward as measured by A-OLP distance,which was decreased by 1 mm(1.5M)and 2.5 mm(3M).SNA angle was decreased by 1 degree(1.5M) and 3.5 degree (3M).SNA angle was decreased by 3.5 mm(1.5M) and average 6.25 mm(3M) with the ratio of skeletal to dental effects 2.5:1(1.5M) and 1.8:1(3M); the molar occlusal changes were found to develop 5 mm distalization with the ratio of skeletal to dental effects 5:1(1.5M) and 4:1(3M);maxillary effects stronger than mandibular effects in the ratio of 2.5 to 1(1.5M) and 5.7 to 1 (3M).Conclusions Zygomatic implant can be utilized as an anchorage not only to inhibit maxilla from growing forward but also to retract maxilla distally with som counter-clocwise rotation. Key words: Implant anchorage; Maxilla; Retractive Forces; Animal experiment