Systematic review of chincup therapy for Class III malocclusion
Liu ZP, Li CJ, Hu HK, Chen JW, Li F, Zou SJ. Efficacy of short-term chincup therapy for mandibular growth retardation in Class III malocclusion. Angle Orthod 2011;81:162-8
In this systematic review, the authors searched 4 databases. There was no language restriction, hand searching was performed, and authors of unpublished data were contacted. Two reviewers independently assessed the abstracts of potential studies. Those relevant were examined further in full text. Disagreements were resolved by discussion or by a third reviewer. The reviewers focused on the SNB angle, the ANB angle, the gonial angle, and the mandible length in each study. After an extensive search with clear inclusion and exclusion criteria, 4 cohort studies were included and analyzed for the review. A meta-analysis was performed for the SNA and SNB angles, and there was great clinical heterogeneity in the reporting outcomes. The meta-analysis showed that chincup therapy increased the ANB angle and decreased the SNB angle. In addition, the results indicated that the gonial angle increased after chincup therapy, yet there was no significant change in mandibular length. These results indicate that chipcup therapy can improve the maxillomandibular relationship by decreasing the SNB angle and increasing the ANB angle. The amounts of decrease in the SNB and increase in the ANB angles were not specified; the authors only indicated that the values were “significant.” The authors were unsure whether these results can be sustained in the long term and concluded that there are not enough data to recommend the use of chincups to retard mandibular growth. Although only 5% of the white population develops a skeletal Class III pattern, these patients are commonly treated in an orthodontic office. It is important to try to correct a skeletal Class III pattern in the early phases by stimulating maxillary growth and delaying mandibular growth.
Reviewed by Emily Driesman
Differences in chewing force in patients with implant-supported bridges
Grigoriadis A, Johansson RS, Trulsson M. Adaptability of mastication in people with implant-supported bridges. J Clin Periodontol 2011;38:395-404
The purpose of this study was to determine whether people with implant-supported bridges in both jaws adjust muscle activity to food hardness during mastication. One group (A, n = 13) had osseointegrated implant bridges in both jaws, and the other group (B, n = 13) had at least 28 permanent teeth. Each participant was connected to an electromyograph, and the vertical, lateral, and anteroposterior movements of the mandible were recorded along with the activity of the masseter and temporalis muscles. Participants were given 4 soft and 4 hard viscoelastic food samples. The experiment took place on 2 consecutive days, and data from the second day were used in the analysis. Although both groups adjusted muscle activity to the hardness of the food, group A showed a significantly weaker increase in activity measured with the electromyograph with harder food early during the masticatory sequence than did group B. Group A showed significantly less reduction of muscle activity during the progression of the masticatory sequence than did group B. The authors concluded that implant-supported bridges cause impaired adaptation of muscle activity to food hardness during mastication. Although implant-supported prostheses can restore a person’s esthetics and masticatory functions, they lack periodontal receptors and thus do not send sensory signals to the central nervous system. The main take-home message from this study is that, even though implant-supported bridges are an adequate replacement for missing teeth, they still do not function exactly like natural teeth. During treatment-plan discussions with patients, it is important to inform them of these differences of implant-supported prostheses, and that their adaptability during mastication might be altered.
Reviewed by Justin Bair