| Early treatment of Class II malocclusion with functional appliance can not only stimulate dental, occlusal, skeletal and facial growth, but also benefit psychological development greatly. Usually fixed functional appliances, e.g. the Herbst appliance, have more satisfying effect on the patients with these kinds of malocclusions. The present research is to evaluate the clinical effects of the modified MARA appliance. In this study, 16 randomly chosen Classâ…¡division 1 patients with retrusive mandible were treated with the modified MARA appliance, and compared with 11 Class II subjects in the control group without orthodontic treatment. Cephalometric headfilms were taken at the beginning and the end of the treatments. Moreover, to investigate the differences in functioning mechanism and clinical effects between the modified MARA appliance and the Herbst appliance, the experimental results of the MARA treatments were compared with the data of the other 17 Classâ…¡division 1 patients accepting the Herbst appliance.Results:1. After 5~10 months (average 7.8 months) of the modified MARA appliance therapy, the Class II malocclusal relationships were corrected to Class I or slight Class III occlusal relationships. The molar correction averaged 6.9 mm, of which 45.90% were caused by skeletal changes (totally due to mandibular effects) and 54.10% were caused by dental changes (33.33% due to upper molar and 66.67% due to lower molar effects). In other words, 38.20% of the molar correction was due to maxillary effects and 61.80% was due to mandibular effects.2. Similar to the effects of the Herbst appliance, the mandible changed significantly using the modified MARA therapy. All the values of the SNB angle, the mandibular ramus height (Co-Go), the mandibular length (Co-Gn) and the mandibular body length (Go-Pg) increased apparently. The amount of growth was beyond natural growth and was significant in clinic. And the decrease of Pg-N perp. distance also indicated acceleration of the mandible growth. Furthermore, there were no apparent side-effects observed on inhibiting the maxillary growth, since the changes of the SNA angle and the location of point A were negligible. Sagittally, changes appeared with the value of angle ANB decreased by 3.16 degree after the modified MARA therapy. In the vertical direction, statistically significant differences were observed in the anterior and posterior face heights (ANS-Me and Ar-Go). In conclusion, these results showed that the modified MARA appliance stimulated the growth of lower facial hard tissue and corrected the discrepancy in the relationship between sagittal and vertical skeletons.3. After the modified MARA therapy, the maxillary molar displaced backward by about 1.26 mm on average, and the mandibular molar and incisor moved forward by 1.67 mm and 1.22 mm, respectively. The differences were statistically significant compared with the control group. In the vertical direction, however, no significant difference was found between the experimental and the control groups in the displacements of either the mandibular molar or the incisor.4. In contrast to the Herbst appliance, the modified MARA appliance led to little maxillary inhibition and intrusion of the upper molar and the mandibular incisors. As shown in the maxillary skeletal measurements, the A-Na perp. distance was distalized and the value of the SNA angle reduced, indicating a restriction of maxillary growth caused by the Herbst appliance. In addition, the upper molar and mandibular incisors appeared intrusion to some extent in the Herbst group. However, these changes were not apparently observed in the MARA group. And the measurement on other variables showed no significant differences among the modified MARA, the Herbst and the control groups.5. Compared with the original MARA appliance, the modified MARA appliance presented obvious advantages on both clinical seperation and production in lab. It was easy to implement and apply by the dentists independently. It also helped to relieve the pain of the patients. Since it is effective while affordable, it may be worth popularization. The present study showed that the modified MARA appliance was effective in treating patients with Class II malocclusions through dental and skeletal changes in the craniofacial complex. It kept the mandible in constant forward position for 24 hours a day, which stimulated the mandible growth, increased the mandibular length, distalized the upper dentition and led to mesial movement of the lower dentition.Compared with the Herbst appliance, the modified MARA appliance causes no restriction of the maxillary growth and a slighter lower incisor labioclination. Moreover, the modified MARA appliance is cost-effective, and easy to make and apply. Thus, it could be a better method in the treatment of Class II malocclusion patients with mandible retrusion. |
PDF Full Text Request