To assess the impact of access cavity design on instrumentation effectiveness in three-dimensional (3D)-printed mandibular incisors with Vertucci Type III canal configuration. Two extracted mandibular incisors with Vertucci Type III anatomy, which presented contrasting morphologies (a spacious canal system with isthmuses in Specimen 1 versus a restricted morphology without in Specimen 2), were replicated via 3D printing. This process yielded 48 resin replicas per specimen (total n = 96), evenly distributed into six groups (n = 8 per group). Each group underwent instrumentation with either WaveOne Gold (WOG) or ProTaper Next (PTN) nickel-titanium (NiTi) systems via one of three access approaches: traditional lingual (TLAC), incisal ridge (IAC), or labial (LaAC). Pre- and post-instrumentation micro-computed tomographic scans were analyzed for iatrogenic errors, canal volume/surface area changes, unprepared areas, and apical diameter. Data were statistically evaluated using three-way analysis of variance (ANOVA) with LSD post hoc test, with the significance level set at p < 0.05. Canal straightening occurred only in the LaAC and IAC groups (9 cases each), whereas apical perforations (22 cases) were exclusive to Specimen 2 replicas. Three-way ANOVA revealed that percentage increases in canal volume and surface area, proportion of unprepared area, and maximum apical diameter following instrumentation were all significantly affected by tooth prototype (all p < 0.001), accessing cavity design (all p < 0.01), and the instrument used (all p < 0.01). In Specimen 1 replicas (spacious canals), PTN with TLAC resulted in a lower proportion of unprepared areas than PTN with LaAC (36.7% ± 8.9% vs. 47.6% ± 7.8%; p < 0.05); however, both techniques preparing only one canal. In contrast, PTN with IAC prepared both canals and achieved the most complete preparation (18.8% ± 3.2% unprepared, p < 0.05). The use of WOG significantly improved outcomes in the LaAC group, reducing unprepared areas to 13.9% ± 4.8% (p < 0.05). Similar trends emerged in Specimen 2 replicas, though the narrower anatomy increased procedural difficulty. WOG consistently outperformed PTN: IAC prepared both canals in all cases (8/8), while LaAC succeeded in 87.5% (7/8). Unprepared surfaces were significantly lower with IAC (8.0% ± 5.5%) and LaAC (9.3% ± 8.2%) than with TLAC (34.2% ± 5.1%; both p < 0.01). IAC demonstrated superior efficacy for instrumentation of mandibular incisors with Vertucci Type III canals compared to TLAC and LaAC. WOG enhanced LaAC performance and surpassed PTN overall. Access design and instrument selection critically influence procedural success.
Wang et al. (Sat,) studied this question.