Creation of well‐balanced experimental groups for comparative endodontic laboratory studies: a new proposal based on micro‐CT and in silico methods

Abstract

Aim To introduce a new method to select anatomically matched teeth using micro‐computed tomographic (micro‐CT) technology. Methodology Single‐rooted mandibular incisors with a single root canal (n = 60) were selected and distributed into three experimental groups according to the method used for matching 10 pairs of teeth in each group. In group 1, the pairs of mandibular incisors were randomly selected from a pool of teeth. In group 2, teeth were paired based on the measurement of canal width 5 mm from the root apex using radiographs taken from buccolingual and mesiodistal directions. In group 3, teeth were scanned (pixel size of 14.25 μm) and pair‐matched based on the anatomical aspects of the root canal, named aspect ratio (AR), volume and three‐dimensional canal geometry. After allocating the specimens into groups 1 and 2, the teeth were scanned and the canal morphology evaluated as in group 3. A bivariate Pearson’s regression analysis was performed correlating the individual AR values of each pair, and the correlation coefficient was used to estimate the strength of the pair‐matching process. One‐way anova post hoc Tukey’s tests were applied for pairwise comparisons at a significance level of 5%. Results The micro‐CT revealed that 100% of the samples had strong (80%) or very strong (20%) correlations with respect to AR values. Analysis of the radiographic method revealed strong correlation in two pairs (20%), but most of the samples had weak (30%) or negligible (30%) correlation coefficients. The randomization method resulted in three pairs (30%) with very strong correlations, whilst 50% had weak or negligible rates. A significant difference in correlation coefficients was observed in the micro‐CT method compared to the other groups (P < 0.05), whilst no difference was detected between radiographic and randomized methods (P > 0.05). Eta‐squared (η2) calculations demonstrated a very high effect size in the micro‐CT group for selecting pairs (0.99) and lower effect sizes in the radiographic (0.67) and randomized (0.66) groups. Conclusions Use of Micro‐CT was able to provide better control of the confounding effect that anatomical variances in tooth morphology may have on the results in experiments with matched‐pair design.

Influence of minimally invasive endodontic access cavities on root canal shaping and filling ability, pulp chamber cleaning and fracture resistance of extracted human mandibular incisors

“…The degree of homogeneity of the groups was confirmed with regard to length, volume and surface area of the root canals in relation to baseline parameters (P > 0.05). Moreover, careful pairing of specimens reduces the risk of bias associated with a heterogeneity of root canal anatomy in mandibular incisors which can lead to false results and improve the internal validity of the present study (De-Deus et al 2020, Silva et al 2020).…”

“…It has been recently pointed out anatomical matching using micro‐CT technology is the better method to control the confounding effect that anatomical variance in tooth morphology may have on the results in experiments with matched design (De‐Deus et al . 2020). Then, the samples were randomly assigned to the four experimental groups ( n = 10) according to the endodontic access cavity (TEC or MIEC) and root canal preparation protocol (MTwo or TRUShape).…”

“…Moreover, careful pairing of specimens reduces the risk of bias associated with a heterogeneity of root canal anatomy in mandibular incisors which can lead to false results and improve the internal validity of the present study (De‐Deus et al . 2020, Silva et al . 2020).…”

Current status on minimal access cavity preparations: a critical analysis and a proposal for a universal nomenclature

“…Overall, these findings suggest that the percentage of untouched walls after the mechanical preparation of root canals in different groups of teeth may not be compromised by minimal access cavity preparations; however, further studies using micro‐CT and contralateral pair‐matched teeth (De‐Deus et al . 2020) are recommended.…”

Contrast‐enhanced micro‐CT to assess dental pulp tissue debridement in root canals of extracted teeth: a series of cascading experiments towards method validation

“…To verify the canal morphology, the cross‐sectional images were segmented using an automatic routine (De‐Deus et al . 2020) in the FIJI/ImageJ software (Fiji v.1.51n; Madison, WI, USA), and the aspect ratio of the root canal, defined as the ratio of the major to the minor diameters, was measured in each slice from the orifice to the apical foramen. Then, canal volume (in mm 3 ) was calculated as the volume of binarized root canal within the volume of interest.…”