Investigating the Factors Affecting the Need for Unilateral Space Maintainer for First Primary Molars in Late Mixed Dentition

Abstract

Background. Premature loss of deciduous teeth can lead to loss of space and have a negative effect on occlusion. The use of space maintainers can reduce the severity of problems such as crowding. However, the literature is controversial regarding the effects of early loss of primary first molars The aim of this study was to determine the factors affecting the need for unilateral space maintainer for the first deciduous molars in late mixed dentition. In this cross-sectional study, fifty children between 6 to 8 years who had lost a primary first molar unilaterally later than 6 months ago were randomly selected. Midline deviation, molar and canine relationships at both sides, facial growth pattern, and the amount of space loss were all assessed. Data were analyzed using SPSS version 25 via one-sample t-test, paired t-test, and linear regression ( $\text{alpha}=0.05$ ). Methods. In this cross-sectional study, 47 children aged 8 to 10 years with early unilaterally loss of first primary molar in the past 6 months were randomly selected. First, the type of occlusion based on the angle molar relationship and the growth pattern of face based on the Hall and Farkas and midline were assessed. Anterior crowding was measured. SPSS 25 program and Chi-square, t-test, ANOVA, and linear regression were used to analyze the data. A significance level of 0.05 was considered. Results. The results showed that the amount of space loss is 0.56 mm ( $\text{maxilla}=0.54$ and $\text{mandible}=0.58$ ), which is not clinically significant, and there is no need for space maintainer. Increasing age ( $p=0.021$ ) and increasing the percentage ratio of facial pattern ( $p=0.009$ ) significantly reduced the space loss and increased the duration of tooth loss ( $p=0.002$ ), and molar relationship in the control side ( $p=0.05$ ) and increasing the canine to lateral distance ( $p=0.016$ ) significantly increased the space loss. Other factors such as crowding, midline deviation, and canine relationship on the control side did not have significant effects on space loss. Conclusion. Space loss due to extraction of the first primary molars in late mixed dentition was neither statistically nor clinically significant. However, in cases of severe crowding, the vertical growth pattern of the face, and molar relationship, further studies are needed, and follow-up of patients is recommended.