Nalbantoğlu AM, et al. J Periodontal Implant Sci. 2023 Jun;53:e28. https://doi.org/10.5051/jpis.2204320216

This study aims to compare the shaping ability of three systems using micro‐computed tomography (micro‐CT). Moderately‐curved mesial canals of 36 mandibular molars were assigned to three groups (n = 24); Protaper Next (PTN, 0.25, 0.06), WaveOne Gold (WOG, 0.25, 0.07), TruNatomy (TRN, 0.25, 0.04), and instrumentation was performed. Pre‐ and post‐micro‐CT scans were obtained. Canal volume and surface, structure model index (SMI), centroid shift, canal transportation, and untouched canal were analyzed. One‐way ANOVA and Student's t‐test were used for statistics. There was no difference in SMI, centroid shift, and centering ability between the study groups (p > .05). Removed dentin and canal surface changes were lower in TRN, while untouched dentin walls were higher (p < .05). Cross‐sections became more rounded (p < .05), but not significant between groups (p > .05). Considering the removed dentin by TRN, it can be used in critical dentin thickness, such as the danger zone (DZ). PTN, WOG, and WOG kept the original canal course similarly. Untouched dentin by TRN (41%) was wider than PTN and WOG, consequently, meticulous irrigation is recommended. TRN, which provides a controlled increase in canal volume, can be used in thin dentin such as the DZ, however, its use should be supported by copious irrigation and brushing considering the rate of untouched dentin walls.Research Highlights: TRN presented a higher untouched dentin wall compared to PTN and WOG. Canal volume and surface changes were the lowest in the TRN group. The centering abilities were similar in PTN, WOG, and TRN.

Objectives: To evaluate the presence of radicular groove and dentin thickness on the palatal aspect of the buccal root of maxillary first premolars using cone-beam computed tomography (CBCT). Materials and methods: Images of 312 maxillary first premolars belonging to 187 patients (between 18-69 years, 94 females and 93 males) who were referred to the clinic were retrospectively reviewed. Root canal treatment, periapical lesion, and post-core were excluded. One and three-rooted premolars were also excluded. CBCT images were viewed on the axial plane to detect grooves. The concave area on the palatal aspect of the buccal root was recorded as a groove. Buccal and palatal dentin thicknesses were measured by two observers at the level of 3 mm below furcation. Statistical analyses were performed. Results: Buccal and palatal thicknesses were 1.28(±0.25) and 0.87(±0.13) mm, respectively. According to Student’s t-test, buccal dentin thickness was statistically higher than palatal dentin (p=0.016). The prevalence of groove was 82.05%. While palatal thickness without groove was 0.93(±0.14) mm, palatal thickness corresponding to groove was 0.82(±0.12) mm. One-way ANOVA showed palatal and buccal thickness in group 1 (18-35 years) was statistically lower than group 3 (>65 years) (p=0.012 and p=0.003). No statistical difference in thickness was observed between sex and left or right side (p>0.05). Conclusions: Palatal thickness related to groove can be considered a “danger zone” for post-core and endodontic treatment. Considering the high prevalence (82.05%) and thin dentin of the groove, more conservative canal and post space preparation and CBCT examination are recommended to avoid perforation.