Use of Micro-Computed Tomography and Computer-Aided Design in Comparative Volumetric Analyses of Endodontic Armamentarium

Abstract

Use of Micro-Computed Tomography and Computer-Aided Design in Comparative Volumetric Analyses of Endodontic Armamentarium

Department of Dental Biomaterials Science Seoul National University School of Dentistry Anna Hwayoung Yi (Supervisor: Prof. Shin Hye Chung)

1. Objectives The purpose of root canal treatment (RCT) is to chemo-mechanically disinfect and shape the canal space, and thereafter create hermetic seal of the canal system using obturant and sealer. Part one of the present study is a comparative analysis of the root canal morphological changes induced by the two different file systems, ProTaper Next (PN) (Dentsply Maillefer, Ballaigues, Switzerland), the conventional rotary full sequence system (RFSS), and the newly introduced WaveOne Gold (WG) (Dentsply Maillefer), which is a reciprocating file (RF) system. This is represented by the volumetric changes before and after the shaping of canals with varying degrees of curvature severity. Part two of the present study is a comparative analysis of the volumetric changes of the three different sealers spanning 8 weeks post-obturation ex vivo. The sealers studied include the conventional epoxy resin-based AH Plus (AP) (Dentsply Maillefer), a calcium silicate-based EndoSeal MTA (ES) (Maruchi, Wonju, Republic of Korea), and a cold flowable gutta-percha (GP) named Guttaflow 2 (G2) (Coltène Whaledent, GmBH+Co KG, Langenau, Switzerland).

2. Material and Methods The sample teeth were selected following the inclusion criteria: no root caries, un-treated root canals, and complete apexification. To compare the effect of the two different file systems, the mesiobuccal and distobuccal canals were randomly categorized into two groups (n = 32/group) – the rotary PN group and the reciprocating WG group. To compare the effect of the three different sealers, the palatal canals were randomly classified into three groups (n = 12/group) and were named the AP group, ES group, and G2 group respectively for AH Plus, EndoSeal MTA and Guttaflow 2. In part one, the canal preparation was executed to the pre-determined working length up to the apical size of 25 (PN: X2 25/06

WG: Primary 25/07) following the respective manufacturers protocols. In part two, the canals were prepared up to the apical size of ISO 40 with Protaper NEXT X4 for standardization. In part two, each AP, ES, G2 sealer was prepared whilst adhering to the corresponding manufacturers instructions, and single-cone technique with ISO 40 GP cone (Meta Biomed, Chungju, South Korea) was used. After the canal filling, the coronal cavity was sealed with Fuji II LC (GC, Tokyo, Japan). All root surfaces, except for the 2 mm radius encircling the apical foramen, were covered with varnish before being stored in a separate sealed container with 5 mL of phosphate-buffered saline solution at 37 C. The micro-computed tomography (microCT) images (SkyScan1172, SkyScan, Aartselaar, Belgium) were taken at 24 hours, 1 week, 2 weeks, 4 weeks and 8 weeks post-obturation. The scanned images were reconstructed using NRecon version 1.6.2.0 (SkyScan, Belgium). The reconstructed images were visualized into three-dimensional (3D) models for volumetric analyses using two medical computer-aided design (CAD) software programs (Mimics, Materialise N.V., Leuven, Belgium

3-matic, Materialise N.V.). All used PN and WG files, as well as the obturated specimen were prepared for viewing under field emission scanning electron microscopy and energy dispersive x-ray spectroscopy. The statistical analyses was performed using SPSS version 24 (SPSS, Chicago, USA) with the statistical significance set at P < 0.05, whilst using Levene's test, one-way analysis of variance, Tukey's HSD test, Dunnett's T3 test and independent samples t-test for different comparison types.

3. Results In part one, WG group resulted in statistically significant canal deviation at coronal-third of straighter canals compared to that of curved canals, which may clinically translate to the risk of cervical canal transportation during relatively routine root canal treatments of straight canals. Its shaping ability, however, was not significantly different from that of ProTaper Next at a given canal-third at a given curvature severity. In part two, ES group showed a statistically significant increase in the total volume at 8-weeks, compared to that of the AH group. There was an increase in volume of the G2 group, but without statistical significance compared to the ES group. The volumetric increase in the ES group, further supported by the FE-SEM observations, clinically translates to the potential for ES to provide continued filling of the canal wall interface as an endodontic sealer, via continued hydroxyapatite (HA) crystal growth in the presence of bodily fluid.