Abstract
The aim of this study was to evaluate the post-treatment anteroposterior and vertical alterations in skeletal Class II malocclusion with different maxillary patterns in patients treated with modified Thurow appliance. Forty-five patients (22 girls and 23 boys) with skeletal Class II and angle SN.GoGn ≤ 35 and different maxillary patterns (n = 15), as follows: retrusive (SNA<80°), normal (SNA = 80°- 84°) or protrusive (SNA>84°) maxilla; mean age 9 years at pre-treatment (T1) and 9 years and 10 months at post-treatment (T2), were treated with modified Thurow cervical traction appliance, with expander screw and extraoral face bow with 10° to 20° fold in relation to the intraoral arch. Force of 500 gf was applied and use for 12 to 14 h/day, with fortnightly adjustments. Analysis of variance ANOVA followed by post-hoc Tukey and Kruskal-Wallis test, followed by Mann-Whitney were used (α = 5%). In changes obtained from stage T1 to T2, no statistically significant differences were found among the groups Protrusive, normal and retrusive maxilla for the variables SNB, SN.GoGn, 1.NA, overjet, overbite and Class II discrepancy (right and left) (p>0.05). Angular measurements SNA and ANB in the protrusive maxilla group were significantly greater than in the normal and retrusive maxilla groups (p<0.01). However, in the normal maxilla group these values did not differ significantly from those of the retrusive maxilla group (p>0.05). Within the limits of this study, it may be concluded that the modified Thurow cervical traction appliance was efficient for the correction of skeletal Class II irrespective of the maxillary pattern. The mandible had no significant rotation during treatment.
Highlights
Class II malocclusion may be caused by bone dysplasia or by movement of the dental arch, or by a combination of skeletal and dental factors [1]
Among the orthopedic appliance that propose to redirect the growth of the maxillary complex [8], special mention is made of the Thurow [6] extraoral appliance (1975), coupled to a maxillary splint, which is capable of redirecting the maxilla spatially, in addition to providing improvements in the position of the teeth
The purpose of the present study was to fill this gap in the literature by evaluating the post-treatment anteroposterior and vertical alterations in skeletal Class II malocclusion with different maxillary patterns in patients treated with modified Thurow cervical traction appliance
Summary
Class II malocclusion may be caused by bone dysplasia or by movement of the dental arch, or by a combination of skeletal and dental factors [1]. The period of mixed dentition is the most indicated stage for the treatment of this malocclusion [4,5,6], in which at least half of the children go through a growth spurt and a speed to a level of at least 50% related to pubertal changes [7]. Up to now, no investigation has been made to evaluate the behavior of these devices, with respect to patients with different anteroposterior positioning of the maxilla, considering that these devices are routinely used for the purpose of correcting maxillomandibular discrepancy, without worrying about the maxillary position in relation to the base of the skull. The purpose of the present study was to fill this gap in the literature by evaluating the post-treatment anteroposterior and vertical alterations in skeletal Class II malocclusion with different maxillary patterns in patients treated with modified Thurow cervical traction appliance
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