[Fibre-type differences in masseter muscle of Beagle dogs with implanted functional appliance therapy].

PURPOSE: To observe the changes of MyHC-I expression in masseter muscle of Beagle dogs with implanted functional appliance therapy，and to investigate the adaptive remodeling of masticatory muscle. METHODS: Eight, seven-month-old, male Beagle dogs were randomly assigned to experimental group and control group and were killed at 4,8,12 weeks during treatment and 4 weeks after the appliance removed(16 weeks). Serial cross-sections of superficial masseter muscle were cut and stained with MyHC-I antibodies.SPSS11.5 software package was used for statistical analysis. RESULTS: The positive expression rate of MyHC-I was 7.61% in the control group, and 20.43% in the experimental groups at 4 weeks﹙P<0.01﹚. The amount of type I fibres reached to peak at 8 weeks. With increase of treatment time, the amount of type I fibres gradually reduced. At 16 weeks, the amount of type I fibres was similar to the control groups. CONCLUSIONS: The expression of MyHC-I is significantly changed in masseter muscles of Beagle dogs with implanted functional appliance therapy. Implanted functional appliance forward mandibular displacement therapy can obviously promote the adaptive remodeling of masticatory muscle.

[Assessment of facial skeletal growth and response to implanted functional appliance therapy with three-dimensional images].

PURPOSE: To evaluate the facial skeletal growth and response to implanted functional appliance therapy with three-dimensional images. METHODS: Eleven male Beagle dogs (7 months old and in late mixed dentition) were randomly divided into four groups: implanted functional appliance group, semi-implanted functional appliance group, modified Forsus(TM) group and the control group. After the appliances were inserted in the experimental groups for 4, 8, 12 weeks and 4 weeks after the appliances were removed, the facial skeleton and teeth of the Beagle dogs digital information was obtained by using spiral computed tomography, then Mimics 8.1 software and a kind of retro-engineering software called qualify V8.0 were used to establish three-dimensional facial skeletal and dental images of the Beagle dogs. Three-dimensional structure changes of the facial skeleton and teeth in each group at different stages were assessed by the Bjork method, i.e. the superimposition technique based on the "best fit" of anterior cranial base structure and mandible metallic implants. RESULTS: Mandibles in the groups with implanted functional appliance, semi-implanted functional appliance, and modified ForsusTM were obviously displaced forward, while the growth of the maxilla was inhibited in some degree. The displacement of upper teeth in the group with implanted functional appliance was not obvious, while the distal movement of upper teeth in the group with semi-implanted functional appliance and modified ForsusTM was significant compared with that in the control group. CONCLUSIONS: The implanted functional appliance can significantly stimulate the growth of the mandible and avoid the unwanted movement of teeth which is frequently found in other functional appliances. Supported by Wenzhou International Cooperative Research Project (Grant No. B00260027).