Abstract
BackgroundTo evaluate how the amount of expansion of the primary second molars, the patient’s age, and the skeletal maturation stage influence the amount of expansion at the level of the permanent first molars.Material and MethodsFifty-five patients aged between 6 and 11 years with a cervical vertebral maturation stage of CS1 or CS2 were retrospectively selected. The intermolar width was measured before and after expansion to evaluate the amount of expansion achieved at the level of the primary second molars and the permanent first molars. Stepwise multiple linear regression was used to evaluate how the amount of primary molars expansion, the patient’s age, and the cervical vertebral maturation stage predict the amount of permanent molar expansion.ResultsA significant regression equation was found, and for every 1 mm of primary molar expansion, 0.91 mm of permanent molar expansion can be expected. An age between 6 and 11 years and the CS1 or CS2 skeletal maturation stage were not significant predictors of permanent molar expansion.ConclusionsA rapid maxillary expansion appliance anchored on primary second molars is effective in expanding the permanent molars to correct a transverse maxillary deficiency in prepubertal patients, transferring the risks associated with the large forces used to the primary teeth. Key words:Maxillary expansion, transversal deficiency, primary molars.
Highlights
Maxillary transverse deficiency is a relatively common feature and can lead to a posterior unilateral or bilateral crossbite
Material and Methods The records of patients treated with rapid maxillary expansion (RME) at the Orthodontic Department of the University of L’Aquila from January 2013 to September 2017 were screened for the following inclusion criteria: -Age between 6 and 11 years -Prepubertal stage of growth assessed through the cervical vertebral maturation (CVM) method [16] between CS1 and CS3 -Treatment with an RME appliance with two bands bonded on the primary second molars -Intra-oral photographs recorded before and after the active expansion phase -High quality of occlusal photographs of the upper arch, which should have been perfectly perpendicular to the occlusal plane
Sample size calculation to perform a linear regression with a standard deviation of permanent molar expansion of 3, an estimated correlation coefficient of 0.4, and a slope estimate obtained from regressing deciduous molar expansion against a permanent molar expansion of 0.9 — as retrieved from a pilot study — revealed that 43 subjects would be needed to be able to reject the null hypothesis that this slope equals zero with a power of 0.8 and a type I error probability of 0.05. -Error of the method Twenty-five subjects out of the entire study group were randomly selected using an online tool, and the measurements were repeated by the same observer after a two-week interval
Summary
Maxillary transverse deficiency is a relatively common feature and can lead to a posterior unilateral or bilateral crossbite. To evaluate how the amount of expansion of the primary second molars, the patient’s age, and the skeletal maturation stage influence the amount of expansion at the level of the permanent first molars Material and Methods: Fifty-five patients aged between 6 and 11 years with a cervical vertebral maturation stage of CS1 or CS2 were retrospectively selected. Stepwise multiple linear regression was used to evaluate how the amount of primary molars expansion, the patient’s age, and the cervical vertebral maturation stage predict the amount of permanent molar expansion. Conclusions: A rapid maxillary expansion appliance anchored on primary second molars is effective in expanding the permanent molars to correct a transverse maxillary deficiency in prepubertal patients, transferring the risks associated with the large forces used to the primary teeth
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