Dealing with posterior crossbite in young patients

Abstract

In the past quarter century, over 5000 articles and abstracts about maxillary expansion have been published. That amount of ink devoted to a single subject is overwhelming, and yet questions remain. Does posterior crossbite in the deciduous dentition self-correct? If not, should something be done before the permanent teeth erupt? What long-term outcomes can be expected after rapid palatal expansion in the mixed dentition? How does this increase in maxillary width compare with normal growth in untreated subjects? Does unilateral posterior crossbite lead to TMJ disc displacement when not corrected early? For help in answering these questions, please read 4 excellent articles on maxillary expansion in this issue of the Journal. But as a member of the AAO's Council of Scientific Affairs (COSA), I must admit that these articles will not answer all your questions. Dr Greg Huang was recently appointed to chair a COSA committee to identify published systematic reviews. His committee compiled a list of 44 reviews or meta-analyses representing 8 categories of orthodontic care; some of the reviews have also been identified by the Cochrane Collaboration. I looked at the short list of 3 reviews on posterior crossbite. The first 2 assess the orthodontic correction of unilateral posterior crossbite in the deciduous and early mixed dentition; the third, a meta-analysis, relates to treatment in the late mixed dentition. Petren and Bondemark1Petren S. Bondemark L.A. Systematic review concerning early orthodontic treatment of unilateral posterior crossbite.Angle Orthod. 2003; 73: 588-596PubMed Google Scholar identified 1001 pertinent articles published between January 1966 and October 2002; 12 met their inclusion criteria. In 2 studies, grinding the deciduous canines was the treatment of choice for correcting crossbite in the primary dentition. Insufficient evidence was available to show which of the alternative treatment modalities—quad-helix, expansion plates, or rapid maxillary expansion—was next most effective. Most studies were limited by a lack of power due to small sample size, bias, or confounding variables. To obtain reliable scientific evidence, better-controlled RCTs with sufficient sample sizes are needed. Future studies should also assess long-term outcomes and analyze costs and possible side effects of the interventions. Harrison and Ashby2Harrison JE, Ashby D. Orthodontic treatment for posterior crossbites. Cochrane Database Systematic Rev 2001;(1):CD000979.Google Scholar searched controlled clinical trials and concluded that “The removal of premature contacts in the primary teeth is effective in preventing a posterior crossbite from being perpetuated to the mixed dentition and permanent teeth.” They found that, when grinding alone is not effective, an upper removable expansion plate to expand the maxillary teeth decreases the risk that a posterior crossbite will be perpetuated. They found no evidence of a difference in treatment effect for banded versus bonded slow maxillary expansion, transpalatal arch with or without buccal root torque, or upper removable expansion appliance versus the quad-helix. Insufficient data were provided to compare 2-point and 4-point rapid maxillary expansion appliances. Schiffman and Tuncay3Schiffman P.H. Tuncay O.C. Maxillary expansion: a meta analysis.Clin Orthod Res. 2001; 4: 86-96Crossref PubMed Scopus (55) Google Scholar published a meta-analysis in 2001 based on a Medline search from 1978 to 1999 for studies examining the stability of transverse maxillary expansion. They reduced more than 5000 articles to 12 based on the defined inclusion criteria. The mean expansion after adjustment was 6.00 mm (±1.29 mm [SD]). During the retention period, 4.89 mm of the expansion was maintained, but it fell to 3.88 mm during the short-term postretention period and to 2.4 mm in the long-term postretention period—an amount no greater than normal growth.4Marshall S. Dawson D. Southard K.A. Lee A.N. Casko J.S. Southard T.E. Transverse molar movements during growth.Am J Orthod Dentofacial Orthop. 2003; 124: 615-624Abstract Full Text Full Text PDF PubMed Scopus (41) Google Scholar The evidence suggests that the best choice for treating posterior crossbite in a young child is selective grinding of the primary dentition, but this will not correct all posterior crossbites. Unfortunately, despite the thousands of articles on posterior crossbites, there appears to be no clear consensus on the most efficient, effective, and stable method to correct.them. The long-term results of Schiffman and Tuncay3Schiffman P.H. Tuncay O.C. Maxillary expansion: a meta analysis.Clin Orthod Res. 2001; 4: 86-96Crossref PubMed Scopus (55) Google Scholar seem to suggest that, although some expansion holds up during retention, relapse eventually occurs. Perhaps the take-home message is that many treatments appear to be successful in the short term, but challenges remain in the search for better long-term outcomes.