The pattern of movement and stress distribution during retraction of maxillary incisors using a 3-D finite element method / 대한치과교정학회지

OBJECTIVE: The purpose of this study was to evaluate the displacement pattern and the stress distribution shown on a finite element model 3-D visualization of a dry human skull using CT during the retraction of upper anterior teeth. METHODS: Experimental groups were differentiated into 8 groups according to corticotomy, anchorage (buccal: mini implant between the maxillary second premolar and first molar and second premolar reinforced with a mini implant, palatal: mini implant between the maxillary first molar and second molar and mini implant on the midpalatal suture) and force application point (use of a power arm or not). RESULTS: In cases where anterior teeth were retracted by a conventional T-loop arch wire, the anterior teeth tipped more postero-inferiorly and the posterior teeth moved slightly in a mesial direction. In cases where anterior teeth were retracted with corticotomy, the stress at the anterior bone segment was distributed widely and showed a smaller degree of tipping movement of the anterior teeth, but with a greater amount of displacement. In cases where anterior teeth were retracted from the buccal side with force applied to the mini implant placed between the maxillary second premolar and the first molar to the canine power arm, it showed that a smaller degree of tipping movement was generated than when force was applied to the second premolar reinforced with a mini implant from the canine bracket. In cases where anterior teeth were retracted from the palatal side with force applied to the mini implant on the midpalatal suture, it resulted in a greater degree of tipping movement than when force was applied to the mini implant between the maxillary first and second molars. CONCLUSION: The results of this study verifies the effects of corticotomies and the effects of controlling orthodontic force vectors during tooth movement.

Correlationship of skeletodental factors to a relapse in Class II correction / 대한치과교정학회지

The purpose of this study was to evaluate the postretention change of class II malocclusion treatment and to examine which factors were related to the relapse. Seventy-eight treated cases were divided into two groups according to the stability of treatment results. Various measurements in pre-treatment and post-treatment lateral cephalograms were evaluated and comparisons were drawn between the stable and relapse group by t-test and correlation analysis. 1. There were only a few differences in the skeletodental relationship in the pre-treatment phase between the stable and the relapse group. 2. Mandibles in the stable group were repositioned more anteriorly than those in the relapse group. 3. Mandibular incisors were more uprighted to the basal bone and maxillary incisors were less lingualized in the stable group than in the relapse group. 4. Occlusal plane was inclined forward and downward in the relapse group.