Evaluation and comparison of root resorption between tooth-borne and tooth-tissue borne rapid maxillary expansion appliances: A CBCT study

Abstract

Objective: To compare volumetric root resorption after rapid maxillary expansion (RME) between tooth-borne and tissue-borne appliances using CBCT. Repair in resorption cavities after 6 months of fixed retention was also compared.

Materials and methods: A sample of 33 subjects were randomly divided into two groups: Hyrax (n = 16) and Haas (n = 17). CBCT scans were taken 6 months before expansion, immediately after expansion, and 6 months after fixed retention. Mimics Innovation V 16.0 software was used for segmentation and volumetric measurement of 198 teeth. Bland-Altman plots, independent samples t test, repeated measures analysis of variance, and the Friedman test were used for statistical analysis.

Results: Differences in root resorption after RME and repair after retention were not significant between the hyrax and Haas appliances or between male and female. Significant differences were found between preexpansion and postexpansion root volumes in the first premolars and molars--even in unattached second premolars. When the percentage of root volume loss is considered, no significant difference was found between the first premolar, second premolar, and first molar. Volumetric changes after 6 months of retention were not statistically significant.

Conclusions: More resorption was observed in the Hyrax expander group. But it was not statistically significant. Repair was observed after 6 months of retention. Heavy RME forces affected premolars and molar similarly.

Keywords: CBCT; Root resorption; Segmentation.

Figure 1.

(A) Tooth-borne expander (Hyrax-type) and (B) tooth-tissue–borne expander (Haas-type).

Figure 2.

Segmentation and volumetric measurement: (A) Selecting the optimal threshold; (B) Edit mask in 3-D; (C) Edit mask in 2-D; (D, E) 3-D reconstruction.

Figure 3.

Bland-Altman plots to observe intraobserver repeatability. Upper and lower lines show the agreement. A range of agreement was defined as mean bias ± 1.96 SD.