Retained primary tooth in unusual ages in southern Iran: A population-based study

BACKGROUND AND AIM: The retained primary tooth (RPT) is a tooth that remains beyond its exfoliation time, which can cause some problems. This study aimed to evaluate the prevalence of RPT in unusual ages in Larestan, a city in Fars Province, southern Iran. METHODS: In this cross-sectional population-based study (April-October 2015), clinical and radiological evaluations were done for all patients referred to Larestan dentistry clinics. The characteristics of RPT were evaluated. All data were analyzed statistically using SPSS and MedCalc software (α = 0.05). RESULTS: Among 2106 patients, 145 (6.88%) had at least one RPT. The most frequent RPT were primary canine in the maxilla (42.45%) and second primary molar in the mandible (33.01%). The main cause of RPT was absence of permanent successor tooth congenitally (67.45%) and impaction of it (33.54%). The most tooth mobility was class III (17.92%) and the second molar in mandible had the most mobility (6.60%). Root resorption was seen in about 45% of patients, which level 3 was the most (24.76%), mostly in second molar in mandible. Infra-occlusion was seen only in 5.18% of patients. There were significant correlations between root resorption and age (r = 0.175, P = 0.0360) and gender (r = 0.171, P = 0.0400), mobility and decay (r = 0.470, P < 0.0010), as well as infra-occlusion (r = 0.262, P = 0.0010). CONCLUSION: The prevalence of RPT in unusual ages was not high in this study, but exact examination can detect the RPT earlier, to prevent the related problems by suitable treatments. Studies in larger population are recommended.