Stability of unilateral posterior crossbite correction in the mixed dentition: A randomized clinical trial with a 3-year follow-up

Meghan Sullivan Walsh June 15, 2011
Literature Review – St. Joseph/LMC Pediatric Dentistry



Stability of unilateral Posterior cross bite correction in the mixed dentition: A randomized clinical trial with a 3-year follow-up

Resident: Meghan Sullivan Walsh

Program: Lutheran Medical Center –Providence

Article Title: Stability of unilateral posterior cross bite correction in the mixed dentition: A randomized clinical trial with a 3-year follow-up

Authors: Sofia Petren, Kristen Bjerklin, and Lars Bondemark

Journal: American Journal of Orthodontics and Dentofacial Orthopedics

Volume (number), Year, Page #’volume 139, Issue 1, January 2011 Pgs. e73-81

Major topic: To discuss and determine long-term stability of treatment for posterior cross bite.

Overview of Method of Research: 60 Subject: (33 girls and 27 boys), 40 with unilateral posterior cross bite and 20 controls with normal occlusion were used for this study. 20 were treated with a quad helix appliance and 20 with expansion plates. The sample size was also distributed by sex and age. Patients had to meet the following criteria – mixed dentition, unilateral posterior cross bite, no sucking habit or sucking habit discontinued at least one year before trial and no previous ortho treatment. Study casts made at baseline, post treatment and three years post treatments. Measurements were made of the casts including maxillary and mandibular intercanine and intermolar changes at the shortest linear distance at gingival margins and the cusps tips of the teeth. Overbite, overjet, midline deviation and arch length were also measured. Treatment for both sets of crossbite patients was retained for six months post treatment. Later in the study 10 more patients were added to the follow-up study.

Findings: No significant differences between the two groups with respect to age, sex or side of cross bite between the two groups and the control. Cross bite subjects at baseline had significantly smaller values for all maxillary variables. Midline deviation was more prevalent in the quadhelix and expansion plate groups than the normal group. During treatment, maxillary intermolar and intercanine distances increased significantly in both treatment groups. Mandibular intermolar expansion was significantly greater in the expansion plate group than in the quad-helix. After treatment, a correct midline was achieved in more than half the cross bite patients. At three years post treatment all 15 patients in the expansion-plate group and 19 of the 20 patients in the quad-helix group had normal transverse relationships: in other words the treatment was longitudinally stable. However, during the post treatment period, significant decreases in maxillary and mandibular transverse dimensions occurred in both treatment groups. For overbite, overjet, and arch length, there were no differences within or between groups.

Key points: This study confirms the hypothesis that patients with cross bite who are treated and corrected successfully have long term stability. However, at the end of the follow-up period the maxillary transverse width of patients with previous cross bite had significantly smaller transverse width. The width of the maxilla in a former cross bite patient group never reaches the mean maxillary width of the normal group. Midline deviation is frequently seen in posterior cross bite patients however, the long term effects are unpredictable. Overbite and Overjet showed no differences between the treated patients and the controls. There was no increase in the maxillary arch length in the treatment groups. Therefore this study does not support the assumption that cross bite correction by quad-helix or expansion plate treatment will increase the available tooth space.

Assessment of the Article: Great study to support early and successful correction of cross bite stability. Interesting to note that the study did not support an increase in available tooth space.