Oral health in patients with different sites of head and neck squamous cell carcinoma is not different.

Oral health might not only act as risk factor for head and neck squamous cell carcinoma (HNSCC), but might also have a predictive value for the patients' survival. Currently, information on the effect of oral health on survival of patients with different sites of HNSCC is lacking. This single-center retrospective study aimed to compare oral health in patients with different sites of HNSCC and to analyse whether oral health is associated with survival in the different subsets of HNSCC patients. Dental records of HNSCC patients referred for dental assessment prior to radio(chemo)therapy were included. Patient-related parameters (age at time of diagnosis, sex, tobacco exposure, alcohol consumption, HPV status), treatment data (primary treatment, intent), performance status, tumor demographics (anatomical site, TNM staging), and oral health parameters (DMFT, periodontal health, teeth with/without root canal treatment and with/without periodontitis apicalis) were obtained. Oral health parameters were compared between different anatomical sites. Survival of all HNSCC patients and of individual subsets was assessed using Kaplan-Meier statistics, and the effect of tumor demographics, patient-related parameters, and oral health on survival was analysed by cox regression analyses (α = 5%). 371 patients with HNSCC (oral: n = 86, oropharyngeal: n = 174, hypopharyngeal: n = 59, laryngeal: n = 15, other: n = 37) were included. Oral health parameters did not differ between subsets (padj.≥0.199). Five-year cumulative survival of HNSCC patients amounted to 78.6%. Only for HNSCC originating in the oral cavity and oropharynx, survival was associated with the treatment intent (p = 0.015) or performance status (p = 0.007) in the multivariable analyses, respectively. Within the limitations of this study, oral health was not different between different subsets and had no significant effect on survival of HNSCC patients.

Risk Factors for and Clinical Presentations Indicative of Vertical Root Fracture in Endodontically Treated Teeth: A Systematic Review and Meta-analysis.

INTRODUCTION: The aim of this study was to identify specific clinical signs or symptoms and potential risk factors which are most likely associated with the presence of a vertical root fracture (VRF) in endodontically treated teeth (ETT). METHODS: Electronic databases (MEDLINE via PubMed, EMBASE via Ovid, Scopus, and Web of Science) were searched by 2 reviewers in October 2022 for clinical studies, in which at least either the clinical presentation or potential risk factors associated with a VRF were assessed. Risk of bias was assessed using the Newcastle-Ottawa scale. Meta-analyses of odds ratios (ORs) were performed separately for several signs or symptoms and risk factors. RESULTS: Fourteen sources reporting on 2877 teeth (489 with VRF and 2388 without VRF) were included in the meta-analyses. Regarding the clinical presentation, the presence of sinus tracts (OR = 4.87; 95% confidence interval [CI], 1.58-15.0), increased periodontal probing depths (OR = 13.24; 95% CI, 5.44-32.22), swelling/abscess (OR = 2.86; 95% CI, 1.74-4.70), and tenderness to percussion (OR = 1.76; 95% CI, 1.18-2.61) were significantly associated with the presence of a VRF (Padj. value < .05). None of the assessed risk factors (sex, type of teeth, tooth location, posts, indirect restoration, and apical extension of the root canal filling) were found to be significantly associated with the presence of a VRF (Padj. value > .05). CONCLUSIONS: Four clinical presentations were identified to be the most significant signs or symptoms for a VRF in ETT: presence of sinus tracts, increased probing depths, swelling/abscess, and tenderness to percussion. None of the assessed risk factors pointed out to be significantly associated with a VRF. REGISTRATION: CRD42022354108 (PROSPERO).

The Relation Between Students' Theoretical Knowledge and Practical Skills in Endodontics: Retrospective Analysis.

BACKGROUND: Dental undergraduate students are required to show sufficient practical skills prior to treating patients. Practical skills and the underlying theoretical knowledge are taught in preclinical courses. Usually, the learning outcome is assessed in written multiple-choice examinations (theoretical knowledge) and practical skills tests. However, students' assessment of practical skills is more time consuming and prone to bias than objective multiple-choice examinations. OBJECTIVE: This study aims to analyze the relation between students' theoretical knowledge and practical skills in endodontics. Furthermore, the predictive validity of a theoretical knowledge assessment on students' practical skills was assessed. METHODS: Examination results from all students who participated in the preclinical phantom course in Operative Dentistry (sixth semester of the undergraduate dental curriculum in Germany) between the 2015 summer term and the 2022 summer term were retrospectively evaluated (N=447). The effects of age, sex, previous course participation, and theoretical knowledge on students' practical skills were assessed, using Pearson correlations, Wilcoxon rank sum tests, and a linear regression analysis. Subsequently, students' theoretical knowledge and practical skills were compared via a Fisher exact test to identify a suitable pass mark for students' theoretical knowledge that was associated with sufficient practical skills (≥60%). RESULTS: Students' theoretical knowledge was significantly associated with practical skills (Padjusted=.02; r=0.13). By using the current pass mark for theoretical knowledge (ie, 60%), a significant differentiation between insufficient practical skills (<60%) and sufficient practical skills (≥60%) was achieved (P=.02). However, for the discrimination between students with sufficient practical skills and students with insufficient practical skills, an adapted pass mark for theoretical knowledge would be more appropriate. The ideal pass mark amounted to 58% (P=.02). CONCLUSIONS: Students' practical skills and theoretical knowledge are significantly correlated. By objectively measuring students' theoretical knowledge, a rough estimation of students' practical skills (ie, a differentiation between sufficient and insufficient practical skills) is possible.

Effect of preparation size on the removal of accumulated hard-tissue debris from the mesial root canal system of mandibular molars using SWEEPS technology.

OBJECTIVES: This study assessed the influence of preparation size on the efficacy of shock wave-enhanced emission photoacoustic streaming (SWEEPS) and conventional irrigation (CI) on removal of accumulated hard tissue debris (AHTD) from isthmus-containing mandibular molars using micro-computed tomographic analysis. MATERIALS AND METHODS: Sixty extracted mandibular molars with two mesial canals connected by an isthmus were selected. Canals were shaped with Mtwo instruments (VDW, Munich, Germany) up to sizes 25/.06, 40/.04 or 40/.06 (n = 20), and specimens were distributed into 2 final irrigation groups (n = 10): SWEEPS and CI. Roots were scanned at a resolution of 10.5 µm before and after preparation and final irrigation. Data sets were co-registered, and the percentage reduction of AHTD calculated for each specimen was statistically compared using analysis of variance with a of 5% significance level. RESULTS: The preparation size did not significantly influence the percentage reduction of AHTD (p < 0.05), whereas the final irrigation technique had a significant effect on debris removal (p < 0.05). A significant reduction of AHTD was achieved after final irrigation in all groups (p < 0.05); however, SWEEPS was associated with a significantly greater percentage reduction of debris than CI (p < 0.05). None of the specimens presented a completely clean isthmus. CONCLUSIONS: Removal of AHTD was not significantly affected by the preparation size. SWEEPS was associated with significantly less debris than CI. CLINICAL RELEVANCE: SWEEPS performed significantly better than CI regarding the removal of AHTD from isthmus-containing mandibular molars irrespective of the preparation size.

Micro-CT evaluation of frozen and embalmed human cadavers on the effect of root canal preparation on microcrack formation in old dentin.

The aim of this study was to evaluate the existence of preoperative dentinal defects among differently preserved dentoalveolar bone-blocks (frozen vs. embalmed) and to investigate the effect of varying apical forces (low: <4 N, high: 4-8 N) during root canal preparation on microcrack formation using micro-computed tomography (micro-CT). Thirteen embalmed and seven frozen bone-blocks containing 1-3 single rooted teeth were collected. The teeth were evenly divided into three groups (n = 10): FLow (frozen, <4 N), ELow (embalmed, <4 N), EHigh (embalmed, 4-8 N). After working length determination all specimens were scanned preoperatively. Root canal preparation was performed using nickel-titanium instruments sizes 25/.06 and 40/.06 (F6 SkyTaper; Komet, Lemgo, Germany). A postoperative scan was performed and image stacks were co-registered. All cross-sectional images were screened to identify the presence of dentinal defects. The results were expressed as the percentage of teeth/slices presenting dentinal defects. The statistical analyses were performed with Kruskal-Wallis-Test and Mann-Whitney-U-Test (α = 5%). Embalmed specimens presented a significantly higher percentage of slices with preoperative microcracks (p<0.05) than frozen specimens. No significant difference between groups was observed regarding the induction of microcracks (p>0.05). Root canal preparation does not induce microcracks in dentoalveolar bone-blocks from donors of old age, irrespective of the preservation method and the apically directed forces.

Survival analysis of fragment reattachments and direct composite restorations in permanent teeth after dental traumatic injuries.

BACKGROUND/AIM: In case of crown fractures after traumatic dental injuries, the affected teeth can be restored either with reattachment of the fractured fragment or with a direct composite restoration. So far, longevity data for reattachments and direct composite restorations with regard to different failure types (pulp necrosis and infection, restoration loss) are scarce. Therefore, the aim of this retrospective study was to evaluate the restorative and biological survival of reattached fragments and composite restorations after crown fractures in permanent teeth. MATERIAL AND METHODS: Dental records of patients treated between 2000 and 2018 were retrospectively analysed regarding the restoration (reattachment or direct composite restorations) of teeth with crown fractures. Survival (no further intervention) and restorative and/or biological failure of all restored teeth were recorded. Statistical analysis was performed using Kaplan-Meier statistics, and the mean annual failure rates for two and 5 years were calculated. Furthermore, the effect of potential risk factors on survival was assessed. Log-rank tests and univariate Cox regression models (likelihood ratio tests) were used to assess the univariate effect of all variables of interest. Variables with a p-value ≤.10 were included in a multivariate Cox regression model with shared frailty (p < .05). RESULTS: Overall, 164 patients with 235 teeth (uncomplicated crown fracture: N = 201, complicated crown fracture: N = 34) were included (1.6 ± 2.5 years observation time). Of these, 59 teeth were restored with reattachment of the fragment and 176 with a composite restoration. Overall, composite restorations had a significantly higher survival rate than reattachments (p = .002). The cumulative survival after 2 years was 42.9% and 65.0% for teeth treated with a reattachment (mAFR = 34.5%) and a composite restoration (mAFR = 19.3%), respectively. When differentiating between failure types, restoration failure and pulp necrosis were significantly more frequently detected in reattached crown fractures compared to composite restorations (restorative failure: p = .001; biological failure: p = .036). In the multivariate Cox regression model, the variable jaw and luxation significantly influenced the survival when the tooth was restored with a composite restoration. The survival was not influenced by the fracture type. CONCLUSIONS: Restorative and biological failures were more frequently detected when the tooth was restored with a reattached fragment compared to a direct composite restoration. Both, restoration failure and pulp necrosis with infection should be considered as frequent complications after restoration of crown-fractured teeth which emphasizes the necessity of regular and short follow-up intervals throughout the first 2 years.

Influence of moisture content of frozen and embalmed human cadavers for identification of dentinal microcracks using micro-computed tomography.

The aim of this study was to investigate the influence of moisture content in frozen and embalmed human cadavers on the detection of dentinal microcracks using micro-computed tomography (micro-CT). The group of embalmed specimens included three mandibular and two maxillary segments each containing one tooth. The group of frozen cadavers consisted of two frozen mandibular bone-blocks with two teeth and one mandibular segment containing one tooth. The final number of teeth for each preservation method was n = 5. All specimens were scanned with eight different moisture conditions: 48 h wet, 2 h dry, 48 h wet, 24 h dry, 48 h wet, 1 wk dry, 48 h wet, 1 wk dry. Micro-CT images were screened for the presence of dentinal microcracks. Statistical analysis was performed by nonparametric analysis of variance (α = 5%). Only few microcracks were observed in wet and in 2 h dried bone-blocks with no significant differences (p = 0.63 and p = 0.23, respectively). There was a significant and steady increase of microcracks within the groups of dried specimens as follows: 2 h dry < 24 h dry < first wk dry < second wk dry (all p < 0.008). Preservation method had no significant influence on the visibility of microcracks (p = 0.98). Identification of dentinal microcracks on micro-CT images is influenced by moisture content of cadaveric bone-blocks irrespective of the preservation method.

Effectiveness of different fiber post removal techniques and their influence on dentinal microcrack formation.

OBJECTIVES: The aim of this study was to evaluate the effectiveness of different fiber post removal techniques and to correlate dentinal loss with microcrack formation. MATERIALS AND METHODS: Forty-five extracted single-rooted teeth were root canal treated and fiber posts were adhesively luted. Specimens were divided into three groups (n = 15) according to the removal technique: long-shaft round bur (EndoTracer #08, Komet, Lemgo, Germany), SonicFlex Endo (KaVo, Biberach, Germany), DT Post Removal Kit (VDW, Munich, Germany). Roots were scanned before post cementation and after post removal using micro-computed tomography. Dentin loss, residual luting material, working time, and the induction of microcracks were assessed. Statistical analysis was performed by using multiple contrast tests (max-t tests, α = 0.05). Correlations between parameters dentin loss/new microcracks and dentin loss/residual material were calculated using Kendall's tau. RESULTS: Post removal with SonicFlex Endo resulted in the highest amount of removed dentin with significant differences to the round bur and the DT Post Removal Kit. No technique was found to completely remove the post and luting material. All techniques induced microcracks with the DT Post Removal Kit presenting the highest number of new defects. No correlation between dentin loss and new microcracks was observed. Deviations from the original root canal occurred in all groups, but no perforation was observed. CONCLUSIONS: All techniques resulted in dentin loss, residual luting material, and the formation of microcracks. However, no correlation between dentin loss and the induction of microcracks was observed. CLINICAL RELEVANCE: As all techniques resulted in microcrack formation and dentin loss, this study emphasizes the risk of iatrogenic damage due to post removal procedures.

Micro-computed Tomographic Evaluation of the Shaping Ability of 3 Reciprocating Single-File Nickel-Titanium Systems on Single- and Double-Curved Root Canals.

INTRODUCTION: We performed a micro-computed tomographic assessment of the preparation of moderately single- and double-curved root canals using 3 single-file reciprocating nickel-titanium systems: S1 Plus Standard (Sendoline, Täby, Sweden), WaveOne Gold Primary (Dentsply Sirona, Ballaigues, Switzerland), and Reciproc R25 (VDW, Munich, Germany). METHODS: Seventy-five moderately curved mandibular molars with 2 separate mesial root canals were assigned to 3 experimental groups (n = 25) (ie, S1 Plus Standard, WaveOne Gold Primary, and Reciproc 25 groups) by forming matched triples according to curvature (15°-40°), radius (≤18 mm), and type of curvature (single or double curved). Teeth were scanned before and after root canal preparation with a resolution of 10.5 µm using micro-computed tomographic imaging (Bruker SkyScan 1272; Bruker microCT, Kontich, Belgium). The following parameters were assessed: changes in root canal volume and surface area, percentage of unshaped canal walls, structure model index, canal transportation, and centering ratio. Data were analyzed using 2- and 3-way analysis of variance with Tukey and Scheffé post hoc tests (significance level of 5%). RESULTS: No significant differences among groups were observed concerning all parameters. The type of curvature had no significant effect on all tested parameters. Within all experimental groups, canal transportation increased significantly from the apical to the coronal region, of which the majority was directed toward the furcational area. CONCLUSIONS: Preparation with the 3 nickel-titanium systems did not result in significantly different dimensional changes, and there was no significant effect of the type of curvature on all tested parameters.

Effectiveness of different activated irrigation techniques on debris and smear layer removal from curved root canals: a SEM evaluation.

This study evaluates the effectiveness of different activated irrigation techniques on removal of debris and smear layer from curved root canals. Ninety mandibular molars with a root canal curvature between 20 and 40 degrees were assigned to 4 groups (n = 20): syringe irrigation (SI), passive ultrasonic activation (PUI), sonic activation with EDDY (ED) or EndoActivator (EA) and a control group. Mesiobuccal root canals were prepared to size 40, 0.04 and irrigated with NaOCl (3%) according to the respective technique. Roots were split longitudinally and subjected to scanning electron microscopic analysis. Presence of debris and smear layer was evaluated using 5-grade scoring systems with 200× and 1000× magnification, respectively. Data were analysed with nonparametric analysis for ordinal longitudinal data (α = 5%). Activation of the irrigant significantly improved smear layer removal (P < 0.05). Regarding debris, only activation with EA and ED was significantly more effective than SI (P < 0.05). No activation technique was able to eliminate debris and smear layer completely from curved root canals.

Incidence of microcracks after preparation of straight and curved root canals with three different NiTi instrumentation techniques assessed by micro-CT.

This study evaluated the effect of three different NiTi instrumentation techniques on the incidence of microcracks after the preparation of straight and curved root canals using micro-CT. Roots from mandibular premolars and maxillary molars (n = 66) with the same mean canal curvatures were assigned to three groups of straight and three groups of curved roots (n = 11). After preoperative micro-CT scans, root canals were prepared with Reciproc, OneShape and ProTaper Next to size 25. Specimens were scanned again, and pre- and post-operative cross-sectional images (n = 75 263) were screened to identify the presence of dentinal microcracks. Overall, microcracks were detected in 2.97% (n = 2236) of the cross-sectional images. No new dentinal microcracks were observed after root canal instrumentation of straight and curved canals with the tested NiTi systems. Instrumentation with Reciproc, OneShape and ProTaper Next did not induce the formation of dentinal microcracks irrespective of canal curvature.

Diameter and Taper Variability of Single-file Instrumentation Systems and Their Corresponding Gutta-percha Cones.

INTRODUCTION: Manufacturers offer single-file instrumentation systems with matching gutta-percha (GP) cones to simplify root canal preparation and obturation. The purpose of this study was to determine whether file diameters and tapers match with corresponding cone diameters and tapers (precision) as well as industry standards (accuracy). METHODS: Twenty files and corresponding GP cones from each size of F360 (#25, #35, #45, #55 with .04 taper) and Reciproc (#25, #40, #50 with variable tapers) instruments were examined by using optical microscopy (×32) to determine their diameter and taper. Precision was evaluated by using one-way analysis of variance (α = 0.05) with Scheffé post hoc tests and t tests with Bonferroni correction. Accuracy was calculated by subtracting the nominal values from the measured values of all files and GP cones, and mean diameter and taper differences were compared by using one-way analysis of variance (α = 0.05) and Scheffé post hoc test for pairwise comparison. RESULTS: For F360, the majority of file and cone diameters were within the tolerance levels, but most of the file diameters were significantly larger than GP cone diameters (P < .05), but the majority of all measured values were within the tolerance levels. For Reciproc, file and cone diameters at D1 and D3 mostly approached the nominal values. At the coronal end, file diameters #25 and #50 were significantly smaller than cone diameters (P < .05). For both instrumentation systems, almost all file and cone tapers matched with the preset tolerance ranges. For Reciproc, significant differences between file and GP cone demonstrated either smaller cone or smaller file diameters and tapers, depending on the size. Most of the measured values were within the acceptable range, but diameters at the coronal end exhibited the highest percent difference from the nominal values. CONCLUSIONS: Despite the call for standardization, variability in diameter and taper dimensions between single-file instrumentation systems and their corresponding GP cones can be expected.

Consistency of electronic measurements of endodontic working length when using multiple devices from the same manufacturer-an in vitro study.

OBJECTIVES: To assess the consistency of electronic determination of endodontic working length obtained from four identical electronic root canal length measurement devices (ERCLMD) from five different types of ERCLMD each under various in vitro conditions. MATERIALS AND METHODS: Eight extracted teeth, seven single-rooted teeth, and one molar were accessed. Root length was measured and instruments were inserted and fixed with the tip placed beyond and short of the apical constriction, in roots with an artificial perforation or an open apex. Devices tested were Root ZX (Morita, Kyoto, Japan), Dentaport ZX (Morita), Apex ID (SybronEndo, Glendora, USA), ProPex II (Dentsply Maillefer, Victoria, Australia), and Raypex 6 (VDW-Antaeos, Munich, Germany). Teeth were irrigated with different solutions (NaOCl, EDTA, CHX). ERCLMDs were connected and measurements were recorded. Consistency was classified by the scores 0-4. Comparisons were carried out using the Kruskal-Wallis test (α = 0.05). For multiple testing, the level of significance was adjusted and analysis was performed using the Mann-Whitney U test. RESULTS: Among the five types of ERCLMD, Apex ID and Raypex 6 showed the highest consistency. There was no statistically significant difference between the settings and conditions. Raypex 6 showed the highest consistency for measurements in case of a perforation. CONCLUSION: Different devices from one type of ERCLMD show a high consistency. Nevertheless, general statements on the accuracy of one type of ERCLMD taken from studies investigating only one device per type should be drawn with caution. CLINICAL RELEVANCE: The study refers to the reliability and repeatability of determination of endodontic working length by using ERCLMDs.

A comparative in vitro study of different techniques for removal of fibre posts from root canals.

This study evaluates the effectiveness of different techniques to remove fibre posts from root filled teeth in vitro. One hundred and fifty-three extracted single-rooted teeth were decoronated, root-canal treated and divided into three groups (n = 51). Post spaces were prepared for different types of fibre posts: glass fibre, quartz fibre, carbon fibre. Each group was divided into three subgroups with regard to the post removal technique (n = 17): SonicFlex Endo, long-shaft round bur, DT-Post removal kit. Residual material, loss of dentine, working time and procedural errors were assessed using computed tomography. Statistical analysis was performed with a one-way anova (α = 0.05). The highest effectiveness was achieved with the sonic tip and the round bur. A high prevalence of perforations or severe deviations from the root axis was observed for all groups. No technique presented favourable results in all assessed parameters. There is a high risk of perforations.