Panoramic radiographic analysis of primary tooth fusion and associated permanent successor anomalies in 2989 Chinese children: a retrospective epidemiological study.

BACKGROUND

This study investigated the clinical characteristics of primary tooth fusion, identified the most frequently involved sites, and examined fusion patterns associated with permanent successor agenesis to facilitate early clinical management.

METHODS

This retrospective study analyzed 2989 panoramic radiographs of children aged 3-6 years in the primary dentition from Beijing Children's Hospital (January 2022-December 2023). Data on age, sex, fusion location, and successor outcomes were collected. Descriptive statistics, chi-square test and multivariable logistic regression were applied.

RESULTS

Primary tooth fusion was identified in 2.98% (89/2989) of children. Among the 89 cases, the most common patterns were mandibular primary lateral incisor-canine (P-LI-C, 50.56%), mandibular primary central-lateral incisors (P-CI-LI, 29.21%), and maxillary P-CI-LI (20.22%). Unilateral involvement predominated (89.9%, p < 0.001), with no sex difference (p = 0.117). Among the 98 fused pairs, mandibular involvement was more frequent (78.57%, p < 0.001), with no left-right difference (p = 0.541). Successor agenesis occurred in 56.12% of pairs and varied by fusion pattern. Successor agenesis was significantly associated with maxillary P-CI-LI fusion (aOR = 38.85, 95% CI: 8.58-244.35) and mandibular P-LI-C fusion (aOR = 29.30, 95% CI: 7.96-149.87), compared to mandibular P-CI-LI fusion.

CONCLUSIONS

Primary tooth fusion prevalence was 2.98%, predominantly presenting unilaterally in the anterior mandible with no sex or laterality predilection. Maxillary P-CI-LI and mandibular P-LI-C fusion patterns were strongly associated with successor agenesis (aOR: 29-39), underscoring the need for early radiographic monitoring and intervention.