Do “oversized” Hall Technique crowns affect intra-arch dimensions? A split-mouth quasi experimental pilot study

Abstract

Abstract Background: The Hall-Technique preformed-metal-crowns (HT-PMCs) are allegedly oversized, temporarily altering inter-arch relationships. Intra-arch dimensions/Leeway-space (LWS) HT effects are unknown. Aim: To study single HT-PMC intra-arch effects and treated tooth dimensional changes. Materials and Methods: Split-mouth quasi-experimental pilot study. Intra oral scans (iTeroII®) were taken pre-orthodontic separator placement (scan1), immediately post single HT-PMC (scan2) and 1-month later (scan3) in 13 children. Control/ study quadrants’ lengths (“arcs”), and HT-PMC/control tooth dimensions [mesiodistal (MD), buccopalatal/lingual (BP/L), diagonal (Diag1/Diag2)] were recorded in mm (OrthoCad® software). Paired t-test, repeated ANOVA post-hoc analysis statistics (p<0.05). Results: Compared to scan1, the mean study-arc increased by 0.69mm (±0.54) [(n=13, t-test, p<0.001) at scan2, while at scan3, it increased by 0.787mm (±0.34) [(n=8, Repeated ANOVA, p=0.008)]. The HT-PMC treated tooth mean dimensions increased at scan2 by 0.86mm (MD), 0.8mm (BP/L), 0.5mm (Diag1) and 0.69mm (Diag2) (t-test, p<0.001) with similar observations at scan3. There were no significant changes in the control arc nor the control tooth measurements. Conclusion: HT-PMCs increased the intra-arch quadrant length by approximately >1mm. The HT-PMC treated tooth was marginally oversized. This may potentially increase the LWS and contribute to impaction of unerupted first permanent molars, if more than one PMC was used in the quadrant/arch.