Dental Education during the COVID-19 Pandemic in a German Dental Hospital.

Due to the SARS-CoV-2 pandemic, dental treatment performed by undergraduate students at the University of Marburg/Germany was immediately stopped in spring 2020 and stepwise reinstalled under a new hygiene concept until full recovery in winter 2020/21. Patient treatment in the student courses was evaluated based on three aspects: (1) Testing of patients with a SARS-CoV-2 Rapid Antigen (SCRA) Test applied by student assistants (SA); (2) Improved hygiene regimen, with separated treatment units, cross-ventilation, pre-operative mouth rinse and rubber dam application wherever possible; (3) Recruitment of patients: 735 patients were pre-registered for the two courses; 384 patients were treated and a total of 699 tests with the SCRA test were performed by SAs. While half of the patients treated in the course were healthy, over 40% of the patients that were pre-registered but not treated in the course revealed a disease being relevant to COVID (p < 0.001). 46 patients had concerns to visit the dental hospital due to the increase of COVID incidence levels, 14 persons refused to be tested. The presented concept was suitable to enable patient treatment in the student course during the SARS-CoV-2 pandemic.

Apical debris removal of CanalBrushes with different tip modifications.

OBJECTIVE: In this study the apical debris score regarding the rotary use of the CanalBrush (Coltène-Whaledent) with three different tip variations was compared to that of sole needle irrigation. METHOD AND MATERIALS: Sixty straight roots of human teeth with one canal were instrumented to size 45/.04. Roots were split into halves, reassembled, and embedded in model resin to form separable tooth models. Artificially manufactured dentin debris was packed into the apical 2 mm of the roots to form a relatively consistent debris challenge to be assessed. Then, the debris of each root half was evaluated apically using a modified Hülsmann-score under a light microscope. After remounting the models, root canals were irrigated with NaOCl 3% (2 mL): group 1 with sole needle irrigation, in groups 2 to 4 additionally agitated with different versions of the CanalBrush for 30 s at 600 rpm; group 2, one straight bristle ("old"); group 3, two additional diagonal bristles ("new"); group 4, central straight bristle of the new version removed ("experimental"). Following this, all root halves were reevaluated. RESULTS: Irrigation reduced debris scores in all groups (Wilcoxon tests, P < .001). Mean debris scores were reduced from a pre-irrigation score of about 4 for all groups to a score of around 2 to 3 in groups 1 and 2, and to scores around 1 in groups 3 and 4. Samples of groups 3 and 4 were significantly cleaner than of groups 1 and 2 (Mann-Whitney tests, P < .05). CONCLUSION: CanalBrushes with diagonal bristles achieved an improved apical cleaning ability.

Sealing ability of different versions of GuttaFlow2 in comparison to GuttaFlow and AH Plus

Introduction and objective: GuttaFlow2 is a further development of the silicone sealer GuttaFlow, exhibiting a stiffer consistency. This is intended to overcome possible problems regarding retention of the apical part of the root canal filling when preparing for a fiber post. GuttaFlow2 is delivered within a capsule, like GuttaFlow, or within an automix syringe. This study compared apical dye leakage of GuttaFlow2 in comparison to GuttaFlow and AH Plus. The null hypothesis tested was that different sealers exhibited similar microleakage. Material and methods: Seventy extracted human lower premolars with fully mature apices were root canal prepared to 45/.04 and divided into seven groups: group 1: AH Plus sealer, group 2: "normal" setting GuttaFlow, group 3: "fast" setting GuttaFlow, group 4: GuttaFlow2 within a capsule, group 5: GuttaFlow2 within an automix syringe, group 6: positive control, group 7: negative control (n = 10 each). Root canals were filled with sealer (except group 7) and a master gutta-percha cone size 40/.04 using the non-compaction technique. A dye penetration test was carried out by centrifugation for 3 min at 30 G within 5 % methylene blue dye. Linear dye penetration was recorded. Statistical evaluation was carried out with IBM SPSS 19.0 (α = 0.05). Results: The positive control was significantly different from all other groups (ANOVA, p < 0.001; Student-Newman-Keuls post-hoc test p < 0.05). When the control groups were disregarded, no significant differences were apparent. Groups 1 to 5 showed low leakage values when compared with results of earlier studies using a similar methodology. Conclusion: All sealers tested exhibited low dye leakage values.

Retrospective evaluation of perforation repairs in 6 private practices.

INTRODUCTION: The purpose of this study was to investigate retrospectively the clinical outcome of 70 perforation repairs performed by 6 endodontic specialists. METHODS: Endodontic specialists performed a total of 70 perforation repairs (69 patients) between 1998 and 2010 using a nonsurgical or combined nonsurgical/surgical approach. Treatments were performed with the aid of a dental operating microscope. Recalls of at least 6 months were obtained on 49 patients (50 teeth). Two calibrated observers evaluated the radiographic results on recalls up to 116 months, with a mean of 37 months. Pre-, intra-, and postoperative data were evaluated with respect to treatment outcomes and possible prognostic factors. RESULTS: Successful results were obtained in 45 of 50 perforation repairs, a success rate of 90%. Significant prognostic factors included the location of the perforation, sex of the patient, and restorative status of the tooth before perforation repair. The overall success rate of this study was higher than reported in other studies. CONCLUSIONS: Perforation repairs can be performed with a high level of success at least in the short- to medium-term.

Bond strength of adhesive cements to root canal dentin tested with a novel pull-out approach.

INTRODUCTION: A novel approach to the pull-out test using silica-coated and silanized steel spreaders was designed to avoid influence from the post-cement interface. In this study, this test was applied to compare the post retention of adhesive versus conventional cements. METHODS: Canals of 90 single-rooted human teeth were prepared to size 60 taper .02; trimmed to an 8-mm root canal length; irrigated with 40% citric acid, 3% NaOCl, and 70% ethanol; and randomly divided into 9 groups (n = 10). Steel spreaders (size 55, taper .02) were silica coated and silanized with the Rocatec system (3M-Espe, Seefeld, Germany), except for a control group using GCem, and cemented with one of these adhesive luting materials (RelyX Unicem [3M-Espe], Clearfil SA Cement [Kuraray Medical, Okayama, Japan], Bifix SE [Voco GmbH, Cuxhaven, Germany], NX3 [Kerr, Orange, CA], GCem [GC Corp, Tokyo, Japan], or SmartCem2 [Dentsply De Trey GmbH, Konstanz, Germany]) or conventional cements (Hoffmann's cement [Hoffmann Dental Manufaktur GmbH, Berlin, Germany] or Ketac Cem [3M-Espe]). After storage in distilled water (24 h/37°C), the spreaders were pulled out in a universal testing machine at a crosshead speed of 2 mm/min. RESULTS: The failure mode was cohesive or adhesive at the cement-dentin interface in more than 80% of the experimental samples (control group: adhesive to the post: 9/10 samples). Adhesive luting materials retained posts better than conventional cements (t test, P < .001) but with a wide range in variation. RelyX Unicem displayed significantly higher values except when compared with Bifix SE and Clearfil SA (analysis of variance/Student-Newman-Keuls, P < .05). NX3, SmartCem2, and GCem showed no significant differences to Hoffmann's cement and Ketac Cem. CONCLUSIONS: The novel pull-out approach served well in testing the bond strength of different cements to root canal dentin. The bonding effectiveness of adhesive cements varied significantly and was material specific.

Secondary protective seal of root canal fillings performed under simulated clinical conditions

Objective: This study evaluated sealing properties of root canal fillings with an additional composite barrier. The null hypothesis tested was that different sealers and different methods of sealer removal did not influence microleakage. Material and methods: Eighty extracted human molars with fully mature apices had root canal prepared to size 60 taper .02 and divided into eight groups: three experimental groups for each sealer and negative/positive control (n = 10 each). Teeth of experimental groups were mounted into the molar region of a training puppet to simulate clinical conditions. Root canals were filled with AH Plus or GuttaFlow and gutta-percha. Excess sealer was removed with: ethanol-moistened foam pellet only, additional preparation with a water-cooled diamond bur or additional etch-and-rinse procedure (37% phosphoric acid gel). All procedures were carried out until clean as judged by the naked eye. In all groups except the positive control Syntac was applied to the access cavity. Tetric flow was applied in two increments of 1 mm each. A dye penetration test was carried out by centrifugation for 3 min at 30 G within 5% methylene blue dye. Statistical evaluation was carried out with PASW 18.0 (α = 0.05). Results: Although the two sealers had different chemical composition, sealer exhibited no influence on the results, whereas technique of sealer removal did (Two-way-ANOVA, p < 0.001). Groups with "foam pellet" or "bur preparation" showed significantly more leakage than groups with "etch-and rinse" (SNK, p < 0.05). Conclusion: Applying an etch-and-rinse procedure prior to Syntac may be beneficial for the adhesive seal over root canal fillings.

Performance of a fluorescence camera for detection of occlusal caries in vitro.

The aim of this study was to assess inter- and intra-examiner reproducibility and accuracy in the detection and assessment of occlusal caries in extracted human teeth using the newly developed fluorescence based camera VistaProof. Serial sectioning and microscopy are considered the gold standard. The occlusal surfaces of 53 teeth (99 investigation sites) were examined by two examiners with different levels of experience in cariology (one experienced dentist, one final-year dental student) and the VistaProof. Thereafter, the teeth were serially sectioned and assessed for lesion depth. The intraclass correlation coefficients for inter- and intra-examiner reproducibility for the fluorescence-based examinations were 0.76-0.95. There was a significant correlation between the fluorescence and histological examinations for both examiners (r (s) = 0.47 and 0.55, P < 0.01). At the D1 diagnostic threshold (enamel and dentin lesions), sensitivity was 0.71-0.86 and specificity was between 0.32 and 0.76 at different cutoff values. At the D3 diagnostic threshold (dentin lesions), sensitivity was 0.04-0.91 and specificity was 0.56-0.99 for both examiners. When the areas under the receiver-operating characteristic curves were compared, there was no significant difference in the performance between the examiners (P = 0.52 at the D1 threshold, P = 0.81 at the D3 threshold). The VistaProof demonstrated high reproducibility and good diagnostic performance for the detection of occlusal caries at various stages of the disease process. Novice and experienced examiners were able to apply this system as a supportive device for caries diagnostic and monitoring purposes. Sensitivity and specificity values varied depending on the cutoff values.

Adhesive coronal seal of Syntac and Tetric flow following different dentine pretreatment protocols

Introduction: The purpose of this study was to test different sealerremoval protocols following root canal filling before adhesive seal ofaccess cavities. Material and methods: Forty single root teeth wereselected for the study, prepared to size 60 taper .02, and filled withAH plus and a single gutta-percha cone size 55 taper .02. Excesssealer was removed with: ethanol-moisturised foam pellet (group 1),pellet and additional etch-and-rinse procedure (group 2), pellet andadditional preparation with a water-cooled diamond bur (group 3) orby etch-and-rinse following temporary filling for one week (group 4).Syntac and Tetric flow were used as a secondary protective seal. Adye penetration test (centrifugation 3min / 30G; 5% methylene blue)was carried out. Results were analyzed statistically using PASW 18.0(Kolmogorov-Smirnov-test, Kruskal-Wallis-test, Mann-Whitney-test;p < 0.05). Results: Groups 2, 3 and 4 revealed less leakage than group 1(p < 0.05; Mann-Whitney-tests) and displayed no coloration exceedingthe adhesive seal. Teeth with immediate (group 2) or delayed (group4) adhesive seal showed similar results. Conclusion: Acid etching orbur preparation may be recommended before adhesively sealing theaccess cavity in single-rooted teeth. There is no need to wait until thesealer has set.

Clinical adhesive sealing of the pulp chamber following endodontic treatment: influence of thermomechanical loading on microleakage.

PURPOSE: To test the influence of thermomechanical loading and mode of cleaning the pulp chamber on coronal microleakage of adhesive sealings over root canal fillings. MATERIALS AND METHODS: Root canals of molars were instrumented to size 60 taper .02 and filled with AH plus (Dentsply DeTrey) and a single gutta-percha cone size 55 taper .02. After removal of residual sealer with an alcoholmoistened foam pellet, different pretreatments were performed: groups 1 and 5: no further pretreatment; groups 2 and 6: use of a water cooled high-speed diamond bur; groups 3 and 7: etch-and-rinse with 37% H3PO4 for 10 s; groups 4 and 8: diamond bur and etching. Then Syntac (Ivoclar Vivadent) and two consecutive layers of Tetric flow (Ivoclar Vivadent) were applied. After placing glass-ionomer cement as a provisional restoration, teeth of groups 5 to 8 were additionally subjected to thermomechanical loading (chewing simulation of 200,000 cycles/50 N) and thermocycling (2880 cycles between 5 degrees C and 55 degrees C). A dye penetration test (methylene blue dye 5%, centrifugation for 3 min at 30 G) was used to evaluate linear dye penetration and dye penetration area. Statistical tests were performed using SPSS Win 12.0 (Kolmogorov-Smirnov test, two-way ANOVA, t-test). RESULTS: Thermomechanical loading (TML) had a negative impact on coronal seal (two-way ANOVA, p < 0.001). Among TML groups, group 7 (etch-and-rinse) performed best, exhibiting the least influence of TML. CONCLUSION: For adhesive sealing of the pulp chamber floor, the etch-and-rinse technique combined with a flowable resin composite showed promising results. Nevertheless, a stabilizing restoration should be placed as soon as possible.

Influence of moisture on the apical seal of root canal fillings with five different types of sealer.

The aim of this study was to evaluate the influence of moisture on apical leakage using five different types of sealer. There were 120 single-rooted teeth instrumented to .02/#60 and randomly assigned to 10 experimental groups, one control group (AH Plus, lateral condensation) (n = 10) or positive/negative controls (n = 5). Before obturation teeth were dried thoroughly, followed by recontamination with moisture in a wet chamber (moist groups; 37 degrees C for 7 days). The teeth of the experimental groups (a, dry; b, moist) were obturated with sealer (groups 1, AH Plus; 2, Apexit; 3, Ketac-Endo; 4, RoekoSeal; 5, Tubli-Seal) and a single gutta-percha cone .02/#55. Teeth were centrifuged (30 x g for 3 minutes) in 5% methylene blue. Linear dye penetration was measured under a stereomicroscope. Moisture led to less microleakage for Apexit, RoekoSeal, and Tubli-Seal and higher values for AH Plus and Ketac-Endo. Multifactorial ANOVA displayed a significant dependence of leakage on sealer (p < 0.001) and the combination sealer or moisture (p < 0.01). It depends on the sealer type in which way moisture affects the apical seal.