Comparing accuracy in guided endodontics: dynamic real-time navigation, static guides, and manual approaches for access cavity preparation - an in vitro study using 3D printed teeth.

OBJECTIVES: To assess root canal localization accuracy using a dynamic approach, surgical guides and freehand technique in vitro. MATERIALS AND METHODS: Access cavities were prepared for 4 different 3D printed tooth types by 4 operators (n = 144). Deviations from the planning in angle and bur positioning were compared and operating time as well as tooth substance loss were evaluated (Kruskal-Wallis Test, ANOVA). Operating method, tooth type, and operator effects were analyzed (partial eta-squared statistic). RESULTS: Angle deviation varied significantly between the operating methods (p < .0001): freehand (9.53 ± 6.36°), dynamic (2.82 ± 1.8°) and static navigation (1.12 ± 0.85°). The highest effect size was calculated for operating method (ηP²=0.524), followed by tooth type (0.364), and operator (0.08). Regarding deviation of bur base and tip localization no significant difference was found between the methods. Operating method mainly influenced both parameters (ηP²=0.471, 0.379) with minor effects of tooth type (0.157) and operator. Freehand technique caused most substance loss (p < .001), dynamic navigation least (p < .0001). Operating time was the shortest for freehand followed by static and dynamic navigation. CONCLUSIONS: Guided endodontic access may aid in precise root canal localization and save tooth structure. CLINICAL RELEVANCE: Although guided endodontic access preparation may require more time compared to the freehand technique, the guided navigation is more accurate and saves tooth structure.

Impact of a virtual prosthetic case planning environment on perceived immersion, cognitive load, authenticity and learning motivation in dental students.

INTRODUCTION: The application of virtual reality (VR) presents a big trend in medical education. The aim of this investigation was the presentation and assessment of a multi-user virtual prosthetic case planning environment using criteria such as perceived immersion, cognitive load, authenticity and students´ learning motivation during a virtual seminar. MATERIALS AND METHODS: The virtual case planning environment consisted of two different virtual environments - the entrance area and the case planning environment. Students and lecturers visited it with the used VR glasses Oculus Quest 2 (Meta Quest). All participants appeared as tooth avatars (molars) during the prosthetic case planning seminar and were able to communicate. These voluntary virtual case planning seminars took place in the clinical prosthetic courses (4th and 5th year). Students were asked to fill in the questionnaire comprising 15 questions separated into four categories, each assessed by a 11-point Likert scale: perceived presence/immersion, cognitive load, motivation and authenticity. A negative and a positive focus group were built, each consisting of three students answering three guiding questions. An exploratory data analysis was performed with the significance level set at p = .05. RESULTS: A total of 64 students out of 98 participated in the virtual seminars. The results demonstrated that the students felt very comfortable in the virtual seminar environment and were able to focus well on the content, demonstrated in predominantly positive results for presence/immersion. Cognitive load and authenticity presented positive results. In particular, the motivation of the students showed a high score (median: 2.1-2.6; IQR: 3.9). The cognitive load should be reduced if necessary to increase focus. The cyber sickness is a challenge for some students as well as the technical requirements of the internet connection, which needs to be addressed. Nevertheless, virtual case planning seminars are an essential tool for motivating the new generation of students. CONCLUSIONS: The results of the investigation demonstrate that the students felt very comfortable in the virtual seminar environment and were able to focus well on the content. The prosthetic case plannings were well understood and the students quickly become familiar with the environment. The cognitive load could be reduced to increase focus. In particular, the motivation of the students showed a high score. The cyber sickness is a challenge for some students as well as the technical requirements of the internet connection, which needs to be addressed.

Impact of material combinations and removal and insertion cycles on the retention force of telescopic systems.

OBJECTIVES: A variety of dental materials are available for the fabrication of telescopic crowns. The aim was to investigate the impact of material combinations and removal and insertion cycles on their retention forces. MATERIALS AND METHODS: CAD/CAM-fabricated cobalt-chromium-molybdenum (CoCr) and zirconia (ZrO2) primary crowns were combined with polyetheretherketone (PEEK), polyetherketoneketone (PEKK), CoCr, and ZrO2 secondary crowns (four combinations included PEEK/PEKK secondary crowns in a thickness of 0.5 mm bonded to the CoCr tertiary construction), resulting in 12 different material combinations: CoCr-PEEK; CoCr-PEKK; CoCr-ZrO2; CoCr-CoCr; CoCr-PEEK 0.5; CoCr-PEKK 0.5; ZrO2-PEEK; ZrO2-PEKK; ZrO2-ZrO2, ZrO2-CoCr; ZrO2-PEEK 0.5; and ZrO2-PEKK 0.5 (n = 15 pairings per material combination). Pull-off tests were performed with a universal testing machine initially and after 500, 5000, and 10,000 removal and insertion cycles in a mastication simulator. Descriptive statistics with the Kolmogorov-Smirnov, Kruskal-Wallis, and Mann-Whitney U tests were computed (α = 0.05). RESULTS: The tested parameters, material combination, and removal and insertion cycles had significant impact on the retention force values (p < 0.001). An increase in removal and insertion cycles was associated with a decrease in retention forces within CoCr and ZrO2 secondary crowns, regardless of the primary crown material. In contrast, PEEK and PEKK secondary crowns presented higher retention load values after 10,000 cycles than initially. CONCLUSION: Different material combinations behaved differently after simulated removal and insertion regimens. This difference should be considered during treatment planning. CLINICAL RELEVANCE: Telescopic crown systems should be made of materials with predictable retention forces that do not deteriorate with time. The implementation of new materials and technologies facilitates reproducibility and time-saving fabrication.

A comprehensive in vitro comparison of the biological and physicochemical properties of bioactive root canal sealers.

OBJECTIVES: To evaluate the biological and physicochemical features of bioactive root canal sealers. MATERIALS AND METHODS: Human periodontal ligament fibroblasts (hPDLF) and human osteoblasts (hOB) were exposed to eluates of three bioactive root canal sealers, GuttaFlow® bioseal (GF), BioRoot™ RCS (BR), and TotalFill® BC Sealer (TF), and the epoxy resin-based sealer AH plus® (AH). Cytotoxicity and cellular inflammatory response were evaluated. The osteogenic potential was examined using human mesenchymal stem cells (hMSC). Film thickness, flowability, and pH were assessed. Root canal treatment was performed on human extracted teeth to evaluate the sealers' tightness towards bacterial penetration. The antibacterial activity against common pathogens in primary root canal infections was tested. RESULTS: AH was severely cytotoxic to hPDLF and hOB (p < 0.001). The bioactive sealers were generally less cytotoxic. IL-6 levels in hPDLF were elevated in the presence of AH (p < 0.05). AH and GF suppressed IL-6 production in hOB (p < 0.05). AH and BR stimulated the PGE2 production in hPDLF and hOB (p < 0.05). BR was the only sealer that led to calcium deposits in hMSC (p < 0.05). TF and AH showed the lowest film thickness and the highest flowability. Bacterial tightness was best in teeth filled with AH and BR. All sealers showed similar antimicrobial activity, but the overall antimicrobial efficacy was moderate as the bacteria were reduced by just one log scale (p < 0.05). CONCLUSIONS: This study revealed favorable in vitro results regarding the biocompatibility of the bioactive root canal sealers. CLINICAL RELEVANCE: Bioactive root canal sealers may be a useful alternative to epoxy resin-based sealers.

Targeting antibiotic tolerance in anaerobic biofilms associated with oral diseases: Human antimicrobial peptides LL-37 and lactoferricin enhance the antibiotic efficacy of amoxicillin, clindamycin and metronidazole.

Antimicrobial peptides are receiving increasing attention as potential therapeutic agents for treating biofilm-related infections of the oral cavity. Many bacteria residing in biofilms exhibit an enhanced antibiotic tolerance, which grants intrinsically susceptible microorganisms to survive lethal concentrations of antibiotics. In this study, we examined the effects of two endogenous human antimicrobial peptides, LL-37 and human Lactoferricin, on the antibiotic drug efficacy of amoxicillin, clindamycin and metronidazole in two types of polymicrobial biofilms, which aimed to represent frequent oral diseases: (1) facultative anaerobic (Streptococcus mutans, Streptococcus sanguinis, Actinomyces naeslundii) and (2) obligate anaerobic biofilms (Veillonella parvula, Parvimonas micra, Fusobacterium nucleatum). LL-37 and Lactoferricin enhanced the anti-biofilm effect of amoxicillin and clindamycin in facultative anaerobic biofilms. Metronidazole alone was ineffective against facultative anaerobic biofilms, but the presence of LL-37 and Lactoferricin led to a greater biofilm reduction. Obligate anaerobic biofilms showed an increased drug tolerance to amoxicillin and clindamycin, presumably due to metabolic downshifts of the bacteria residing within the biofilm. However, when combined with LL-37 or Lactoferricin, the reduction of obligate anaerobic biofilms was markedly enhanced for all antibiotics, even for amoxicillin and clindamycin. Furthermore, our results suggest that antimicrobial peptides enhance the dispersion of matured biofilms, which may be one of their mechanisms for targeting biofilms. In summary, our study proves that antimicrobial peptides can serve as an auxiliary treatment strategy for combatting enhanced antibiotic tolerance in bacterial biofilms.

Inhibitory effect of LL-37 and human lactoferricin on growth and biofilm formation of anaerobes associated with oral diseases.

This study was conducted to evaluate the antimicrobial potential of the antimicrobial peptides (AMP) LL-37 and human Lactoferricin (LfcinH) on the planktonic growth and biofilm formation of oral pathogenic anaerobes related to caries and periodontitis. Multi-species bacterial suspensions of either facultative anaerobic bacteria (FAB: Streptococcus mutans, Streptococcus sanguinis, Actinomyces naeslundii) or obligate anaerobic bacteria (OAB: Veillonella parvula, Parvimonas micra, Fusobacterium nucleatum) were incubated with different concentrations of AMP solutions for 8 h. Planktonic growth was registered with an ATP-based cell viability assay for FAB and via plate counting for OAB. Biofilms were grown on ZrO2 discs for 4 days in a mixture of the multi-species bacterial suspensions and AMP solutions. Biofilm mass was quantified using a microtiter plate biofilm assay with crystal violet staining. An overall planktonic growth inhibition and biofilm mass reduction of FAB and OAB was registered for LL-37 and LfcinH. Significant inhibitory threshold concentrations of LL-37 were observed in all experiments (p < 0.0001). No significant threshold was observed for LfcinH. Biofilm mass of OAB was barely reduced by LfcinH. The complete mechanisms of the AMPs are not fully understood yet. While LL-37 shows promising features as potential therapeutic for biofilm-associated oral diseases, LfcinH seems unsuitable for this particular indication. For clinical AMP use, further investigations will be necessary.

Effect of polyhexanide as antiseptic mouth rinse against oral pathogens in an in vitro biofilm model.

OBJECTIVE: The aim of this study was to evaluate the anti-biofilm effect of polyhexanide mouth rinses against oral pathogens in vitro. MATERIAL AND METHODS: Biofilms of Candida albicans, Streptococcus mutans, Actinomyces naeslundii, Aggregatibacter actinomycetemcomitans, methicillin-resistant Staphylococcus aureus and Fusobacterium nucleatum were grown on 10 mm diameter hydroxyapatite discs for 5 days. Biofilms were exposed to test substances for 30 s (ProntOral, polyhexanide 0.15%, chlorhexidine 0.2%). Another test set simulating blood contamination in the oral cavity was performed by submerging the discs in defibrinated sheep blood prior to antimicrobial exposure. Biofilm mass was determined via crystal violet staining. The proliferation potency of the cells after antimicrobial exposure was evaluated by plating serially diluted suspensions from extracted biofilms on agar plates and determining the number of colony-forming units (CFU/ml). Mann-Whitney-U, Kruskal-Wallis and Dunn's test were used for statistical analyses. RESULTS: Regardless of blood contamination ProntOral led to a significant reduction of biofilm mass in all strains. Chlorhexidine and polyhexanide reduced biofilm mass in five out of six strains and in only four strains after blood contamination. All agents significantly reduced CFU/ml from S. mutans, A. actinomycetemcomitans and F. nucleatum biofilms. C. albicans and S. aureus biofilms were only affected by ProntOral and polyhexanide. None of the antiseptics significantly reduced the CFU/ml for A. naeslundii biofilms. After blood contamination ProntOral and polyhexanide significantly reduced CFU/ml in all strains, whereas CHX tended to increase the CFU/ml. CONCLUSIONS: Polyhexanide mouth rinses seem to be suitable disinfectants against oral pathogens without their anti-biofilm potential being impaired by blood.

First comparison of a new dynamic navigation system and surgical guides for implantology: an in vitro study.

AIM: The transfer of 3D implant position planning to the clinical site is challenging. The aim of this study was to compare in vitro this transfer accuracy by using dynamic real-time navigation or static surgical guides. MATERIALS AND METHODS: Deviations between planned and actual pilot drill positions were calculated (Denacam and NobelGuide; each n = 90), matching pre- and postoperative CBCT images: entry point, angle, tip (each 3D); depth, mesiodistal/bucco-oral entry points, and angles (each 1D). The influence of the maxilla and mandible, implant region (anterior/posterior), and marker position (ipsilateral/contralateral, Denacam only) was investigated (Mann-Whitney U test). RESULTS: No significant differences occurred regarding entry point (3D), mesiodistal/bucco-oral entry points (1D) or mesiodistal angle (1D) (P > 0.05). The angular and tip deviations (3D) were significantly smaller using Denacam (2.16 ± 0.59 degrees, 0.80 ± 0.55 mm; NobelGuide 2.54 ± 1.19 degrees, 1.09 ± 0.56 mm; P = 0.024, P < 0.0001). The deviations in depth and bucco-oral angle (1D) were significantly smaller using NobelGuide (1.05 ± 0.50 mm, 1.02 ± 1.16 degrees; Denacam 1.50 ± 0.64 mm, 1.51 ± 0.82 degrees; P < 0.0001). Significantly smaller deviations occurred within the mandible (Denacam, 5/8 parameters). Region and marker position showed no influence. No distinct influences were found with the use of NobelGuide. CONCLUSION: Denacam might possibly be a promising alternative to static surgical guides.

Sensitivity of caries pathogens to antimicrobial peptides related to caries risk.

OBJECTIVES: Antimicrobial peptides (AMPs) represent important facets of the immune system controlling infectious diseases. However, pathogens show varying susceptibilities to AMPs. This study investigates the susceptibilities of strains of Streptococcus mutans (SM), Actinomyces naeslundii (AN), and Lactobacillus spp. (LB) towards AMPs and if there are correlations between the appearance of such high-risk strains and clinical caries status. MATERIAL AND METHODS: Plaque samples were collected from patients along with clinical examinations. Bacterial strains were identified via selective media, matrix-assisted laser desorption/ionization analysis-time of flight (MALDI-TOF), and arbitrary-primed-PCR (AP-PCR). Each strain was tested for susceptibility to LL-37, HBD-2, HNP-1, and HNP-3 or phosphate-buffered saline as negative control in a biofilm model on hydroxylapatite discs. Survival rates and resulting risk classification for each strain were determined. Correlations were calculated between the number of high-risk strains (all/S. mutans) appearing in patients and their clinical caries status. RESULTS: Forty-seven patients were included with mean DMFT values of 11.4 ± 8.7. A total of 8 different SM, 30 LB, and 47 AN strains were detected. One-way ANOVA indicated that type/concentration of AMPs had major influence on reductions of Lactobacilli and Actinomyces. Seventeen strains of AN, 2 of SM, and 6 of LB had low susceptibilities to AMPs. The number of such strains in patients showed significant positive correlations to the DMFT values (all p = 0.001; r = 0.452; S. mutans p < 0.0001, r = 0.558). CONCLUSION: The occurrence of low susceptible strains to AMPs seems to correlate with the individual caries status. CLINICAL RELEVANCE: The results may lead to new ways to identify individuals with increased caries risk.

Comparison of ozone gas and sodium hypochlorite/chlorhexidine two-visit disinfection protocols in treating apical periodontitis: a randomized controlled clinical trial.

OBJECTIVES: In this single-blinded, prospective, randomized, controlled clinical trial, the effectiveness of an ozone gas or NaOCl/CHX disinfection protocol was compared within the root canal treatment of apical periodontitis. MATERIALS AND METHODS: Sixty permanent teeth were randomly allocated to one technique. The clinical/radiographic assessment criteria included clinical symptoms, periapical index (PAI), and size of the apical lesion. In both groups, the root canal was mechanically cleaned and irrigated with NaCl and EDTA. Ozone gas (32 g m-3) or NaOCl (3 %) was applied followed by a 1-week inter-appointment dressing (Ca(OH)2). As final disinfection, ozone gas (ozone group) or CHX 2 % (NaOCl group) was applied. Microbial samples were taken after preparing the access cavity, after chemo-mechanical treatment and after inter-appointment dressing by sterile paper points. Microbial identification was performed by mass spectroscopy (MALDI-TOF-MS) and 16S-rRNA gene sequencing. The treated teeth were blindly re-evaluated after 6/12 months. Success rates, the decrease in PAI, the size of apical lesions and bacterial reduction were compared between groups (Fischer's exact test, Mann-Whitney U test). RESULTS: There were no significant differences between the success rates (ozone group: 96.2/95.5 % after 6/12 months; NaOCl group: 95.5/95.2 % after 6/12 months). The differences in the decreases in PAI values and apical lesion sizes were also insignificant after 6 and 12 months. The bacterial reduction showed no significant differences between groups after chemo-mechanical treatment and after inter-appointment dressing. The most commonly found bacterial genera were Streptococcus spp., Parvimonas spp. and Prevotella spp. CONCLUSIONS: The here used ozone gas and NaOCl/CHX protocols showed no difference in bacterial reduction in the sampled areas of the root canals. CLINICAL RELEVANCE: Within the limitations of the study, ozone gas seems to be a possible alternative disinfection agent within the root canal treatment of apical periodontitis.

Differences in physical characteristics and sealing ability of three tricalcium silicate-based cements used as root-end-filling materials.

PURPOSE: To evaluate differences in physical characteristics and sealing ability of root-end-fillings made with these materials compared to the gold standard (ProRoot MTA). METHODS: The physical characteristics of ProRoot MTA, Medcem MTA and Biodentine were evaluated regarding setting time, flow, film thickness, solubility and radiopacity according to the German Institute for Standardization (EN-ISO 6878). To investigate their sealing ability as root-end-fillings, a glucose penetration model was used. 60 human extracted single-rooted teeth were endodontically treated, root-end resections performed and divided in three groups of 20 teeth, using either ProRoot MTA, Medcem MTA or Biodentine as root-end-filling material. After 30 days, glucose concentrations were determined photometrically, followed by statistical analysis (Kruskal-Wallis test, Mann-Whitney U-test). RESULTS: Biodentine showed the fastest setting time (< 12 minutes) and lowest film thickness (0.11± 0.01 mm), whereas Medcem MTA showed the best values regarding solubility (< 0.1%) and flow (9.5± 0.02 mm). ProRoot MTA revealed the highest radiopacity (7.58± 0.1 mm aluminum equivalent). The glucose leakage in the Medcem MTA group was significantly lower than in the ProRoot MTA group (P= 0.011). Biodentine showed lower leakage than ProRoot MTA (P= 0.031). CLINICAL SIGNIFICANCE: As Medcem MTA showed significantly lower leakage than the other materials tested, it may be an alternative for root-end-fillings with comparable physical characteristics to the current gold standard. With the exception of the high solubility, Biodentine performed well regarding leakage and setting time.

Comparison of chairside and laboratory CAD/CAM to conventional produced all-ceramic crowns regarding morphology, occlusion, and aesthetics.

OBJECTIVES: There are many ways to produce all-ceramic crowns. Computer-aided design and computer-aided manufacturing (CAD/CAM) procedures compete against conventional fabricated restorations. As different methods of production may produce variable results, this study aims to compare chairside and laboratory-based CAD/CAM systems to conventional crowns regarding their similarity to original tooth morphology, number of occlusal contacts, occlusal adjustment time, and subjective aesthetic perception. MATERIAL AND METHODS: Impressions of caries-free jaws were taken, and the resulting gypsum casts were scanned with a laboratory scanner. Preparations for all-ceramic full crowns were performed on first molars, and three different restorations were made: CEREC restorations (CER), laboratory-produced CAD/CAM crowns (LABCAD), and conventional waxed-up/pressed ceramic crowns (CONV). Time for occlusal adaptation and the number of occlusal contacts were noted. Two dentists performed aesthetic gradings of restorations. Statistical analysis included one-way ANOVA with least significant difference (LSD) post hoc test, t test, and Kruskal-Wallis test. RESULTS: Metrical deviations of the re-scanned crowns to the original, unprepared tooth surface were 220.55 ± 54.31 µm for CER, 265.94 ± 61.39 for LABCAD, and 252.44 ± 68.77 µm for CONV group. One-way ANOVA showed significant lower deviations for the CER group. LABCAD crowns showed significantly more occlusal contacts, whereas CONV crowns required the least time for occlusal adaptation and showed excellent aesthetic gradings. CONCLUSION: All three methods had pros and cons regarding different parameters. Further improvements of CAD/CAM software shall lead to restorations comparable to conventional restorations in all aspects, especially in aesthetics. CLINICAL RELEVANCE: All tested methods of production for all-ceramic crowns produced clinically acceptable results. Thus, in an individual case, the method chosen can be determined by the dentist's preference.

Evaluation of the effect of bracket-periphery treatment on prevention of enamel demineralization by consecutive µCT scans.

OBJECTIVES: The aim of this study was to assess the effect of two sealants and two varnishes on the prevention of enamel demineralization, as well as the effect of inattentive surplus enamel-etching by a self-etching primer (SEP). MATERIALS AND METHODS: The sealants ProSeal and Clinpro and the varnishes Protecto and FluorProtector were investigated. For inattentive surplus enamel-etching, Transbond Plus SEP was used. The teeth (N = 75) underwent a pH-cycling for 4 weeks and were examined by weekly consecutive µCT scans (t1-t4) to determine mineral loss (ΔZ Equivalent) and lesion depth (Ld). At t4, we also assessed the fluorescence change (ΔF). RESULTS: For ProSeal, no lesions could be detected. In contrast, we found isolated lesions in the area treated with Clinpro. Teeth with inattentive surplus enamel-etching showed always a higher ΔZ Eqivalent. However, this was not statistically significantly different compared to the teeth treated with the varnishes. The adjacent untreated enamel (except the SEP-treated teeth) always showed significantly more demineralization than any of the treated areas. The ΔF partially confirmed these results. CONCLUSION: No lesions were shown in the area of application of ProSeal. The other materials did not sufficiently protect the enamel; however, a protective effect of all materials was obvious when comparing the bracket-periphery with the adjacent untreated enamel. Additionally, the area of SEP application showed almost always a significantly less demineralization in comparison to that found on the adjacent untreated enamel. CLINICAL RELEVANCE: The bracket-periphery was not always sufficiently protected. The adjacent untreated enamel did not benefit from the bracket-periphery treatment.

Antimicrobial effect of gaseous and aqueous ozone on caries pathogen microorganisms grown in biofilms.

PURPOSE: To evaluate the anti-microbial effect of gaseous and aqueous ozone on biofilms of caries pathogen microorganisms with regard to concentration and time dependency. METHODS: Biofilm cultures of Actinomyces naeslundii, Streptococcus mutans and Lactobacillus paracasei were grown on nitro-cellulose-membranes for 48 hours. The membranes were cut into equal-sized pieces and exposed to chlorhexidine digluconate (CHX) (positive control; 0.1-20%), gaseous (1-64 g m3) and aqueous ozone (1.25-20 microg ml(-1)) for 60 seconds. The influence of exposure time (30-120 seconds) was tested for exemplary concentrations of the three agents. Colony forming units of bacteria were counted. The bacteria survival rate was given as percentage of the negative control (PBS for CHX/aqueous ozone, ambient air for gaseous ozone). RESULTS: There was no difference in bacterial reduction of different species with general reduction close to zero for high concentrations of all agents. Univariate ANOVA with partial eta-squared (Eta2) statistics showed major effects for concentration/contact time of the agent on bacteria survival. High concentrated gaseous and aqueous ozone seem to be potential alternatives to CHX with equivalent antimicrobial activity.

Comparison of biogenerically reconstructed and waxed-up complete occlusal surfaces with respect to the original tooth morphology.

OBJECTIVES: Recently, it has become possible to reconstruct complete occlusal surfaces using the biogeneric tooth model. This study aimed to mathematically assess and compare the morphologic agreement between original morphology and CAD-reconstructed, waxed-up and CAM partial crowns. MATERIALS AND METHODS: Thirty-nine intact first permanent molars (39 participants) were included. Impressions, bite registrations and three gypsum replicas were made. Preparations for CAD/CAM partial crowns were performed and scanned. The restorations were biogenerically reconstructed (CEREC® v3.80) and milled. Wax-ups of these preparations were scanned as well as the milled restorations and original teeth. Discrepancies were evaluated by matching the scans with the original morphologies (Match3D, output: volume/area, z difference) and by contact patterns. The discrepancies were compared between CAD-reconstructions and either wax-ups or milled restorations (paired t test, α = 0.025 for two multiple tests). RESULTS: The mean differences between natural tooth morphology (triangular stabilisation 71.8%) and biogeneric reconstructions, wax-ups and milled restorations (triangular stabilisation 87.2%) were: 184 ± 36 µm (volume/area), 187 ± 41 µm (z difference); 263 ± 40 µm (volume/area), 269 ± 45 µm (z difference) and 182 ± 40 µm (volume/area), 184 ± 41 µm (z difference). Differences associated with biogeneric reconstructions were significantly less than those of wax-ups (volume/area and z difference, p < 0.0001), but not significantly different than those of milled restorations (p = 0.423 (volume/area), p = 0.110 (z difference)). CONCLUSIONS: CAD software enables a closer reconstruction of teeth than do wax-ups, even when no cusps remain. The milling device is precise enough to transfer CAD into the final restoration. CLINICAL RELEVANCE: This study shows that state of the art CAD/CAM can effectively produce natural tooth morphology and may be ideal for fixed partial dentures.

Autotransplantation and surgical uprighting of impacted or retained teeth: A retrospective clinical study and evaluation of patient satisfaction.

OBJECTIVES: This retrospective clinical study aimed to determine the success rate of autotransplanted impacted or retained teeth along with a patient satisfaction survey and to analyze the influence of relevant clinical and radiographic parameters. SUBJECTS AND METHODS: Fifty-seven teeth (37 canines, 10 molars, seven premolars, three incisors) in 45 patients (median 15 years) were evaluated over a mean of 1.6 years. The success criteria were pocket probing depth ≤3.5 mm, mobility grade ≤ II, Periotest ≤30 and complete alveolar bone healing. The influencing parameters were oral hygiene, smoking, periodontal screening index, occlusal/proximal contacts, horizontal position, dental age, pulp obliteration and degree of displacement. Furthermore, bone height was measured. RESULTS: The overall success rate was 74%, along with a high patient satisfaction. The survival rate was 96% after a mean follow-up of 1.6 years. The favorable factors were proper oral hygiene, non-smoking, good general periodontal condition, proximal contacts and pulp obliteration. An increase in or maintenance of bone level was found in 96%. CONCLUSIONS: Autotransplantation of impacted or retained teeth is an appropriate treatment, if orthodontic alignment has failed, especially in growing patients.

Differences in clinical reasoning between female and male medical students.

OBJECTIVES: In undergraduate medical education virtual patients (VPs) are a suitable method to teach clinical reasoning and support the visualization of this thinking process in a safe environment. The aim of our study was to investigate differences in the clinical reasoning process and diagnostic accuracy of female and male medical students. METHODS: During the summer term 2020, we provided access to 15 VPs for undergraduate students enrolled in a medical school in Bavaria, Germany. All interactions of the 179 learners within the VP system CASUS were recorded, exported, and analyzed. RESULTS: We found significant differences in the clinical reasoning of female and male learners. Female students documented more findings, differential diagnoses, tests, and treatment options and more often created a summary statement about the VP. Their overall performance was higher than those of their male peers, but we did not see any significant differences in diagnostic accuracy. CONCLUSIONS: The significant differences between male and female medical students should be considered when planning teaching and research activities. A future study should investigate whether these differences can also be found in physicians.

Light Transmission Characteristics and Cytotoxicity within A Dental Composite Color Palette.

Modern light-cured, resin-based composites are offered in a wide range of shades and translucencies. This large variation, created by varying the amount and type of pigmentation and opacifiers, is essential to enable an esthetic restoration in each patient situation, but may affect light transmission in the deeper layers during curing. We quantified optical parameters and their real-time variation during curing for a 13-shade composite palette of identical chemical composition and microstructure. Incident irradiance and real-time light transmission through 2 mm thick samples were recorded to calculate absorbance, transmittance, and the kinetic of transmitted irradiance. Data were supplemented by the characterization of cellular toxicity to human gingival fibroblasts up to 3 months. The study highlights a strong dependence of light transmission and its kinetic as a function of shade, with the largest changes occurring within the first second of exposure; the faster changes, the darker and more opaque the material. Transmission differences within progressively darker shades of a pigmentation type (hue) followed a hue-specific, non-linear relationship. Shades with similar transmittance but belonging to different hues were identified, while the corresponding kinetic was identical only up to a transmittance threshold. A slight drop in absorbance was registered with increasing wavelength. None of the shades were cytotoxic.

Recording the maxillomandibular relationship with the Aqualizer system prior to occlusal splint therapy for treating temporomandibular disorders: a randomized controlled trial.

Temporomandibular disorders (TMD) present a public health issue and are one of the most common musculoskeletal conditions causing chronic pain. This study compares the outcomes of occlusal splint therapy in patients with TMD following two different maxillomandibular relationship (MMR) registration techniques. 40 TMD patients were randomly allocated to MMR registration with the Aqualizer system (AQU) or with chin point guidance (CPG) prior to fabricating occlusal splints. TMD symptoms, subjective pain intensity, and quality of life (QoL) were recorded at baseline and after 3 and 6 months. The treatment led to an overall reduction of TMD symptoms in both groups (Conover test, p < 0.00001). TMJ sounds, TMJ pain with palpation and muscle pain with palpation subsided regardless of the type of MMR registration method used (Cohen's d > 0.8). AQU-based occlusal splints led to a better improvement of TMJ pain with maximum opening compared to CPG-based occlusal splints (Cohen's d = 0.9; CPG d = 0.13). In both groups, occlusal splint treatment had little to no effect on correcting lateral mandible deviation or improving restricted jaw opening. After 6 months occlusal splints in both groups had a large effect on improving subjective pain intensity (Cohen's d > 0.8), however, patients reported a higher QoL in the AQU group compared to the CPG group (Mann-Whitney-U-test, p < 0.05). The results of this study support the premise that occlusal splints are effective in relieving pain-related TMD symptoms. The Aqualizer can be considered for determining MMR in cases, where guided registration techniques are not possible.Trial registration: DRKS00031998.

Fracture toughness of dental restorative materials.

The ability of a restorative material to withstand fracture is of crucial importance especially in stress-bearing area. Therefore, the study aims to analyse the fracture toughness of a large number of dental restorative materials categories. The fracture toughness (K(IC)) of 69 restorative materials belonging to ten materials categories-micro-hybrid, nanofilled, microfilled, packable, ormocer-based, and flowable resin-based composites (RBC), compomers and flowable compomers, as well as glass ionomer cements (GIC) and resin-modified GIC was measured by means of the single-edge notched-beam method after storing the samples (n = 8) for 24 h in distilled water. Data were analyzed with the one-way analysis of variance (ANOVA) followed by the Tukey's test and partial eta-squared statistics (p < 0.05). Large variations between the tested materials within a material category were found. The lowest fracture toughness was reached in the GIC group, followed by the microfilled RBCs, resin-modified GIC, and flowable compomers, which do not differ significantly among each other as a material group. The ormocer-based, packable, and micro-hybrid RBCs performed statistically similar, reaching the highest fracture toughness values. Between the two categories of flowables-composites and compomers-no differences were measured. The correlation between K(IC) and filler volume (0.34) and respective filler weight (0.40) was low. K(IC) increased with the volume fraction of fillers until a critical value of 57%, following with a plateau, with constant values until ca. 65% volume fraction. Above this value, K(IC) decreased slightly. Due to the very large variability of the fracture toughness within a material type, the selection of a suitable restorative material should have not been done with respect to a specific material category, especially in stress-bearing areas, but by considering the individual measured material properties.