Novel Digital Technique to Quantify the Area and Volume of Cement Remaining and Enamel Removed after Fixed Multibracket Appliance Therapy Debonding: An In Vitro Study

Abstract

The aim of this study was to construct a novel, repeatable, reproducible, and accurate measurement protocol for the area and volume of the remaining cement after removal of fixed multibracket appliances, the area and volume of remaining cement after cement removal, the area and volume of enamel removed after cement removal, and the volume of cement used to adhere fixed multibracket appliances. A total of 30 brackets were cemented and removed with over 30 extracted teeth embedded into three experimental models of epoxy resin. The models were scanned before and after bracket placement, bracket debonding, and polishing the remaining cement. The brackets were submitted to micro-computed tomography. The standard tessellation language digital files were aligned, segmented, and re-aligned using geomorphometric software. The digital measurement technique accuracy, repeatability, and reproducibility were analyzed using Gage R&R statistical analysis. The variability attributable to the area and volume measurement techniques of the total variability of the samples was 0.70% and 0.11% for repeatability, respectively, and 0.79% and 0.01% for reproducibility, respectively. The re-alignment procedure is a repeatable, reproducible, and accurate technique that can be used to measure the area and volume of the remaining cement after removal of fixed multibracket appliances, the area and volume of remaining cement after cement removal, the area and volume of enamel removed after cement removal, and the volume of cement used to adhere the fixed multibracket appliance.

Keywords: alignment; cement remaining; digital impression; enamel removed; geomorphometry; orthodontics.

Figure 1

(a) Frontal view of the experimental model of extracted teeth; (b) experimental model with cemented fixed multibracket appliance; (c) experimental model with fixed multibracket appliance removed; and (d) experimental model with cement removed.

Figure 2

(a) Frontal view of the standard tessellation language (STL)1, (b) STL2, (c) STL3, and (d) STL4.

Figure 3

Frontal view of the individually segmented (a) STL1, (b) STL2, (c) STL3, and (d) STL4.

Figure 4

Palatal view of the three-dimensional comparison of the alignment of the segmented tooth 2.3 between (a) STL1 and STL2, (b) STL1 and STL3, and (c) STL1 and STL4. (d) Spectrum values used in (a–c). Warm colors represent a volume increase, cold colors represent a volume decrease, and green represents an accurate alignment.

Figure 5

Palatal view of the three-dimensional comparison of the re-alignment of segmented tooth 2.3 between (a) STL1 and STL2, (b) STL1 and STL3, and (c) STL1 and STL4. (d) Spectrum values used in Figure 4a–c. Warm colors represent a volume increase, cold colors represent a volume decrease, and green represents an accurate alignment.

Figure 6

Buccal view of segmented tooth 2.3 of (a) STL1, (b) STL2, (c) STL3, and (d) STL4. (e) STL of the bracket 2.3 obtained from the micro-computed tomography.

Figure 7

(a) Buccal view of segmented tooth 2.3 of STL1 and (b) STL3; slight overcontouring of (c) STL1 and (d) STL3; (e) boundary of the volumetric comparison between STL1 and STL3 over STL1; (f) boundary of the volumetric excess comparison between STL1 and STL3 over STL3; (g) new mesh with the remaining cement over the STL1 digital file; (h) new mesh with the remaining cement over the STL1 digital file; and (i) combined meshes with the remaining cement after bracket removal of STL1 and STL3, obtaining a closed polygon.

Figure 8

Mesh of the remaining cement after bracket removal in (a) STL3 and (b) STL4, and (c) excess remaining cement after removal in STL4.

Figure 9

Buccal view of the segmented tooth 2.3 of (a) STL1 and (b) STL4; slight overcontouring of (c) STL1 and (d) STL4; (e) boundary of the volumetric comparison between STL1 and STL4 over STL1; (f) boundary of the volumetric defect comparison between STL1 and STL4 over STL4; new mesh with the enamel removed over the (g) STL1 and (h) STL4 digital files; and (i) combined meshes with the enamel removed of STL1 and STL4, obtaining a closed polygon.

Figure 10

Proximal view of (a) the segmented tooth 2.3 of STL2 and (b) the solid mesh of tooth 2.3 of STL2. The mesh is not only in the perimeter, the inside is also filled. (c) STL5 and (d) solid mesh of tooth 2.3 of STL2 with the volume of the cement used to adhere and without the bracket.

Figure 11

(a) Buccal view of segmented tooth 2.3 of STL1; (b) STL2 without bracket; slight overcontouring of (c) STL1 and (d) STL2 without bracket; boundary of the volumetric comparison between (e) STL1 and STL2 without bracket over STL1 and (f) STL1 and STL2 without bracket over STL2 without bracket; new mesh with the volume of the cement used over the (g) STL1 digital file and (h) STL2 without bracket digital file; and (i) combined meshes with the volume of cement used for STL1 and STL2 without bracket, obtaining a closed polygon.

Figure 12

(a) Box plot of the total mean and standard deviation (SD) values and (b) mean and SD values of the aligned and re-aligned samples of each measurement.

Figure 13

(a) Box plot of the mean and SD values of the area and (b) volume measured after the re-alignment of the STL digital files.

Figure 14

(a) Box plot of the mean and SD values of the area and (b) volume measured after the re-alignment of the STL digital files between two operators.