Jörg Philipp Tchorz

Background/Objectives: To compare mechanical behavior, shaping performance, and safety of an original reciprocating endodontic instrument (Reciproc^® Blue) with two visually similar replicas obtained from an online marketplace. Methods: The original Reciproc^® Blue and two replica (designated Replica 1 and Replica 2) instruments purchased from AliExpress were tested. Evaluations included torque resistance, bending resistance, cyclic fatigue resistance (all according to ISO 3630-1 standards, n = 10 per group per test), and an in vitro shaping procedure using artificial root canals in plastic blocks (5 canals per instrument, n = 10 instruments per group) were carried out. Preparation time, number of pecks, procedural errors (blockages, ledges, deformations), and instrument fractures were recorded. Surface characteristics of unused (n = 2) and used instruments (n = 2) were examined using scanning electron microscopy (SEM). Statistical analysis used one-way ANOVA, Welch ANOVA, or Kruskal–Wallis tests according to the distribution and variance pattern of each endpoint, followed by the corresponding post hoc test. Repeated use was analyzed with a linear mixed effects model and checked with a robust generalized estimating equation sensitivity analysis. Deformation-free and fracture-free event curves were compared with exploratory log rank tests. Results: The original instrument showed the highest Mf/D³ and Mt/D³ values. Overall group differences were significant for Mf/D³ (Welch p < 0.001) and Mt/D³ (Welch p = 0.001), with significant Games Howell contrasts between the original and Replica 2. Replicas showed longer cyclic fatigue life (Original 407.1 s, Replica 1 490.2 s, Replica 2 607.8 s; ANOVA p < 0.001). The original instrument had a lower average preparation time for each canal than both replicas (72.8 s vs. 95.8 s and 92.3 s; Kruskal–Wallis p < 0.001) and a lower average number of pecks (8.64 vs. 9.71 and 10.00; p = 0.008). Exploratory log rank comparisons also showed group differences in the deformation-free and fracture-free event curves (Holm adjusted p = 0.005 and p = 0.024, respectively). Both replicas failed to reach working length in 4 out of 10 cases each, with high rates of blockages (Replica 1: 7/10; Replica 2: 2/10), ledges (Replica 1 only), and deformations. The limited SEM subsample revealed severe wear of cutting edges in Replica 1. Conclusions: Both tested replicas exhibited significant deviations in mechanical behavior and markedly inferior shaping safety compared to the original Reciproc^® Blue instrument, despite superficial visual similarity. Therefore, dental practitioners should be aware that low-cost imitations may compromise clinical safety.

Objective: This study aims to comprehensively demonstrate the diverse applications an Objective: Positioning an endodontic laser tip near the working length is important for laser-assisted disinfection of the apical root canal region. The aim of this proof-of-concept study was to investigate the achievable penetration depth of an endodontic diode laser tip in root canals prepared using different methods and to analyse the potential influences of canal geometry and user experience. Methods: Two identical artificial molars were prepared using different instrumentation systems and tapers. The penetration depth of an EasyTip Endo laser tip was examined in the Mesiobuccal (MB), Distobuccal (DB) and Palatal (P) canals by both an inexperienced and an experienced user. A total of 180 measurements were taken and the penetration depth was determined using ImageJ as the distance to the working length. Results: In the DB and P canals, the working length was reached in all measurements. In the MB canals, this was considerably less frequently, occurring in 13-33% of cases. There was no statistically significant difference between the two users. In the MB canal of tooth 2, which had a smaller taper, the distance to the working length was significantly greater than in tooth 1 (median 1.779 mm vs. 0.155 mm; p < 0.001; FDR-adjusted p = 0.006). Conclusion: The achievable penetration depth of an endodontic diode laser tip does not appear to depend solely on the preparation size. Particularly in MB canals, anatomical or geometric factors may limit positioning near the working length.

Background: Cone-beam computed tomography (CBCT) is increasingly applied for the assessment of periodontal bone levels. However, its measurement reliability and consistency depend strongly on image quality parameters such as voxel size, noise, and reconstruction sharpness. With the growing use of CBCT datasets for artificial intelligence (AI)-based diagnostics, it is essential to understand how image degradation conditions affect examiner-derived measurement outcomes and the reliability of reference data used for AI training. Methods: An anonymized CBCT dataset containing one periodontally healthy tooth (31) and one tooth with pronounced periodontal bone loss (41) was analyzed. The original DICOM data were systematically degraded using controlled voxel enlargement (double and triple voxel size) and simulated image blur (Gaussian and median filtering). Six dentists (n = 6) independently performed standardized linear bone-level measurements, with three repeated measurements per tooth and image condition. Data were analyzed using the Shapiro–Wilk test for normality assessment, the Kruskal–Wallis H test for group comparisons, Bonferroni-adjusted Mann–Whitney U tests for post hoc pairwise comparisons, and intraclass correlation coefficients (ICC (2,1)) for inter-examiner reliability assessment. Results: A total of 180 measurements were evaluated. Image degradation conditions were associated with statistically significant differences in bone-level measurements for both teeth (tooth 31: p = 0.017; tooth 41: p = 0.0049). Significant pairwise differences were primarily observed between the original dataset and specific degraded conditions involving blur and reduced spatial resolution, while several comparisons remained non-significant. Inter-examiner reliability varied across image groups and decreased notably with pronounced voxel enlargement, particularly in the periodontally compromised tooth. Conclusions: Controlled image degradation conditions of CBCT image quality significantly affect measurement outcomes and inter-examiner reproducibility of periodontal bone measurements. These findings demonstrate that image quality is a critical determinant of measurement reliability and examiner-dependent interpretation. From both a clinical and AI-development perspective, maintaining adequate CBCT resolution may contribute to more consistent measurement behavior and more reliable training datasets.

Background/Objectives: Cone beam computed tomography (CBCT) is vital in endodontics but suffers from beam-hardening artifacts caused by metallic restorations, which can obscure diagnostic details. This study evaluated a novel patient positioning protocol—a controlled head tilt—designed to mitigate these artifacts by moving contralateral metallic structures outside the primary X-ray path in small field of view (FoV) CBCTs. Methods: Using a skull phantom with metallic restorations CBCT scans were acquired in three positions: standard alignment, a 12° tilt toward the region of interest (ROI), and a 12° tilt to the opposite side. Fifty experienced dentists, blinded to the protocol, subjectively compared image quality and artifact severity between the tilted and reference images. Results: The tilt away from the ROI was rated as providing better image quality significantly more often than the tilt towards the side of the ROI (442 of 585 non-tied comparisons; p < 0.001). A complementary rater-clustered GEE analysis adjusted for slide confirmed higher odds of “better” ratings under head tilt away from the ROI for image quality (OR = 4.16, 95% CI 3.12–5.56) and artefacts (OR = 2.87, 95% CI 1.93–4.26). An individual head tilt significantly improves subjective small-FoV CBCT image quality, most evidently in the longitudinal plane, by reducing artifact interference from contralateral metals, and should be considered a practical strategy for clinical use, and may serve as a practical chairside strategy, pending clinical validation.

Objectives: Two-dimensional intraoral radiographs often obscure canals due to superimposition, especially in mandibular molars with complex anatomy. This cone-beam computed tomography (CBCT) study identified the horizontal beam angles at which first and second molar canals overlap and derived clinically applicable angulations for enhanced canal separation.Methods: Eighty-five CBCT datasets from 100 patients met the inclusion criteria, yielding 318 mandibular molars (160 first, 158 second). Using ImageJ, absolute horizontal overlap angles (α) were measured to determine the corresponding theoretical separation angles defined as δ* = 90° – α. Separability was modeled across horizontal beam angulation increments from −45° to +45° in five steps, and Wilson’s 95% confidence intervals were computed. Group comparisons used the Mann-Whitney U and independent t-tests (p ≤ 0.05)Results: Minimal mesial beam angulations for effective canal separability (δ* = 90° − α) ranged from approximately 7° to 15° for mesial roots and approximately 10° to 13° for distal roots. No significant mesial differences were observed between first and second molars (p > 0.30). Distal roots of second molars exhibited significantly higher angulations (p = 0.003 coronal, p < 0.001 apical). Mesial canals achieved ≥95% separability at approximately 25° and ≥99% at approximately 35°; distal canals required approximately 30° and approximately 40°.Conclusions: A mesial beam angulation of 30° to 35° provides probable canal differentiation in mandibular molars, separating mesial canals in ≥99% and distal canals in ≥95% of cases. This range refines previous recommendations and supports the as low as reasonably achievable (ALARA) principle.

Objectives: The Covid‐19 pandemic increased stress, which may have led to more bruxism, TMDs, and thus tooth fractures. While previous studies, primarily from specialized clinics, reported an increase in cracked teeth during the pandemic, this retrospective study aimed to assess whether similar trends were observed in a general dental practice in Bavaria, Germany, which remained fully operational throughout the pandemic.Material and Methods: Patient records from 2018 to 2023 (n = 4709 patients, 10,018 visits) were analyzed for symptomatic tooth fractures, categorized as wall/cusp fractures, incomplete cracks, or complete fractures.Results: Statistical analysis using the Mann–Whitney U test revealed no significant differences in fracture incidence between pre‐pandemic (2018–2019), pandemic (2020–2021), and post‐pandemic (2022–2023) periods. Mandibular molars were the most frequently affected teeth (7.94%–12.43%), and composite restorations were most associated with fractures (51.85%).Conclusions: Contrary to previous findings from endodontic practices, this study found no pandemic‐related surge in tooth fractures, suggesting that referral bias or patient selection in specialized settings may influence reported trends.

The aim of this study was to analyse cone‐beam computed tomography (CBCT) images to determine the ideal horizontal X‐ray beam angulations for maxillary first and second molars. CBCT scans from 85 patients were retrospectively analysed to measure the angles at which buccal root canals (MB, DB) of maxillary first ( n = 170) and second ( n = 157) molars superimpose the palatal one (P) at coronal and apical levels. The mean angles and standard deviations for both tooth types combined at which MB1 and MB2 overlap with P, as well as the angle at which DB overlaps with P, were 114.01° (±9.30), 119.47° (±11.05) and 87.48° (±12.02), respectively. Angles at coronal levels were higher for both tooth types and all canals. If maxillary molar teeth show no signs of tilt, rotation or unusual anatomy, a distal tube shift of > 18°, based on the orthoradial direction (90°), should be chosen to achieve ideal visual canal separation.

Background/Objectives: Intraoral (IO) radiographs are critical for endodontic diagnostics, yet conventional orthoradial imaging often results in superimposition, limiting the visibility of individual root canals. Maxillary first premolars pose challenges due to their anatomical characteristics and positioning within the dental arch. This study aimed to retrospectively analyze cone-beam computed tomography (CBCT) data to determine the horizontal X-ray beam angulations for maxillary first premolars at which root canals overlap and neighboring tooth superimposition occur, providing clinically relevant guidance for optimizing IO radiographic techniques. Methods: CBCT scans from 85 patients were analyzed using ImageJ software to measure the angles at which maxillary first premolar root canals overlap or become obscured by adjacent teeth. The mean angles for canal overlap and neighboring tooth superimposition were determined. Statistical analysis was performed using SPSS Version 29.0, and the level of significance was set to 5%. Results: The mean angle for root canal overlap was 93.56° (±10.08). The angles at which neighboring teeth began to superimpose were 124.38° (±9.91) for the distal contour of the canine and 63.46° (±9.38) for the mesial root contour of the second premolar. No significant differences were observed between apical and coronal measurements for root canal overlap but tapering of the roots led to significant differences in neighboring tooth superimposition (p < 0.05). Conclusions: A mesial beam shift within a calculated safe corridor (98.5–129.5°) optimizes canal separation without superimposition from adjacent teeth. For ideal visualization, a mesial angulation close to 40° is recommended. These findings support improved IO radiographic techniques while minimizing the risk of retakes in adherence to the ALARA principle.

The aim of this study was to evaluate the influence of root canal size and curvature on the insertion depth of three different endodontic irrigation needles. Four root canals with curvatures ranging from 0° to 69.72° were first enlarged to size .04/25. The insertion depths of a standard open-ended irrigation needle (SI), a single side-vented needle (SV), and a TruNatomy irrigation needle (TN) were then measured repeatedly in the chosen root canals and recorded as distances short of the working length. In curved canals, the SI and SV were tested with and without pre-bending. After enlargement to a greater taper (.06/25), these measurements were repeated. For a descriptive analysis, means and standard deviations were computed, and comparison was performed using the Wilcoxon test and formulated using a Monte-Carlo approximation with the level of significance set to 5%. Due to its flexible material, the best overall results in terms of insertion depth close to the working length were observed for the TN. The SI and SV could be inserted deeper in straight root canals and after enlargement to a greater taper (p < 0.05). In curved root canals, pre-bending of the SI and SV resulted in statistically significantly higher insertion depths (p < 0.05). In conclusion, cannula material properties, preparation size, and insertion depth mainly depend on each other. In curved root canals, a more flexible cannula like the TN should be favored to achieve better insertion depths. If using stainless-steel cannulas, they should be pre-bent to facilitate an insertion closer to the working length.