Virtual reality and haptics in dental education: Implementation progress and lessons learned after a decade.

INTRODUCTION: The search for alternative training environments in dentistry responded mainly to scarcity and lack of standardisation of training material and non-availability of specific clinical procedures. The development of haptic virtual reality (VR) dental trainers provides a platform where irreversible procedures can be safely and unlimitedly practised. The aim of this study was to assess the educational implementation of these devices and evaluate schools' satisfaction. METHODS: Dental schools that were using haptic VR dental trainers, were approached. The Dental Trainer User Inventory (DTUI), addressing the educational implementation and users' satisfaction, was developed and distributed. RESULTS: Twenty-seven schools completed the DTUI. The total number of VR dental trainers available varied from one to 42 devices with a mean of 7 devices. The dental trainer was mostly made available from the first year (63.0%) of the undergraduate program, but it was mostly integrated into the curriculum by the third year (70.4%). Curricular integration was reported by 18 schools (66.7%), while nine schools (33.3%) indicated that they had not yet achieved integration. Twenty-one schools (69.4%) were 'satisfied' or 'very satisfied' with the devices, while two schools (7.4%) were dissatisfied and six schools (22.2%) were neither satisfied nor dissatisfied. CONCLUSION: VR haptic dental trainers are implemented in multiple dental programs and are also being used for educational research and clinical training. Even though curricular changes and teachers' acceptance remain a challenge, most schools are satisfied with VR haptic dental trainers and would recommend the device to other schools.

Students' learning environment perception and the transition to clinical training in dentistry.

INTRODUCTION: The learning environment (LE) influences students' behaviour, and predicts academic achievement, satisfaction and success. Measuring students' perception of the LE provides relevant information for curricular quality assurance. In this study, a LE assessment was used to observe variations in students' LE perception throughout the curriculum, to illustrate the possible influence that preclinical training (Pt) and clinical training (Ct) have on students' learning experience. MATERIALS AND METHODS: All students in the six-year undergraduate dental programme (n = 849) at the Academic Centre for Dentistry Amsterdam (ACTA) were approached and divided into Pt and Ct groups according to their training phase in the curriculum. The LE was assessed using the Dundee Ready Educational Environment Measure (DREEM), and the results were evaluated using the Statistical Package for the Social Sciences (SPSS) software for distribution (Kolmogorov-Smirnov normality test), internal reliability (Cronbach's alpha) and comparative analysis (one-way ANOVA). RESULTS: The questionnaire was completed by 216 (response rate=65%) Pt students and by 379 (response rate=75%) Ct students. With a general DREEM score of 124.3, significantly higher scores were found during Pt (DREEM=133.4) in comparison with the Ct phase of the curriculum (DREEM=119.2). DREEM scores steadily decreased throughout the 6-year curriculum, with the highest drops in LE perception observed in the second and third years of the programme. Significant differences in all DREEM domains were observed, with lower scores for Ct. CONCLUSION: Students' LE perception deteriorates throughout the curriculum, especially within the Pt-Ct transition, during the second and third years of the programme. An inferior LE perception was observed in every domain of the LE questionnaire within this transition showing a learning experience, which requires an educational intervention. Further research is required to better understand the educational needs of the Pt-Ct transition at this school.

Effectiveness of the new mandatory mouthguard use and orodental injuries in Dutch field hockey.

ObjectivesUp to 68% of field hockey players have experienced at least one orodental injury in their sport career. Therefore, the Royal Dutch Hockey Association (KNHB) made mouthguard use mandatory for field hockey players during competition and training from August 2015 onwards.This study evaluates the effects of the new regulations on mouthguard use and the occurrence of injuries in Dutch field hockey.MethodsA 35-item online questionnaire about mouthguard use and orodental injuries was sent to 13 field hockey clubs in the Netherlands. Absolute numbers and percentages of mouthguard ownership, mouthguard use, number and type of injuries were assessed. The results were related to comparable data before mandatory mouthguard use. Associations of gender and training frequency with the number of injuries were analysed with logistic regression.ResultsIn total, 1169 hockey players were included in the study and almost all owned a mouthguard (females:99.6%, males:93.7%), which significantly increased after implementation (p < 0.001). 90.6% of the respondents wore a mouthguard during matches and 70.1% during training. Of the 1169 players, 68(5.8%) experienced at least one orodental injury after the implementation with a total of 100 injuries. Injuries happened more often during matches (63.2%) than during training (36.8%). Lip cuts account for most of the injuries, the number of broken (p = 0.116) and knocked out teeth (p = 0.026) decreased.ConclusionAlthough mouthguard use already increased in recent years, the new regulations led to an additional increase and a successful change of attitude towards mouthguard use. Most importantly, the severity of orodental injuries decreased measurable.

First experiences with patient-centered training in virtual reality.

CONTEXT: In preclinical dental education, plastic and extracted teeth have been broadly used for skills training without specific focus on the patient behind the procedure. A patient-centered approach remains challenging in traditional simulation, which does not resemble realistic clinical situations. OBJECTIVE: This article describes the development and first experiences with a patient-centered virtual reality training module (PC-VR) that allows dental care providers to prepare, beforehand and in virtual reality (VR), specific procedures required by their patients. Experiences with this patient-centered practice are described to reflect on its value for clinical training in dentistry. DESIGN: Using an intraoral scanner, digital impressions of 10 patients were made; these served as stereolithography (STL) digital files, which were converted into volumetric haptic models for display in a VR dental simulator. In this study, students' experiences were investigated through a short open-answer survey in 2018. Atlas.ti was used for qualitative analysis of the answers through the inductive methodology of the grounded theory approach. RESULTS: Drillable virtual models of real patients were made available for training using VR. Inductive analysis of the experiences identified 5 dimensions describing the main features of PC-VR: added value, competence development, self-efficacy, outcomes, and room for development. CONCLUSION: This article provides a general overview of the possibilities and challenges of the implementation PC-VR in dental education. Although concrete effects on trainees' self-confidence and performance are yet to be determined, all participants appreciated the opportunity to explore clinical situations before experiencing them in the context of a real patient.

The Effect of Variations in Force Feedback in a Virtual Reality Environment on the Performance and Satisfaction of Dental Students.

INTRODUCTION: The aim of this study was to investigate the transfer of skills between various levels of force feedback (FFB) using the Simodont dental trainer (Moog, Nieuw-Vennep, the Netherlands). Students practiced a manual dexterity exercise in a virtual reality environment at a standard level of FFB and then were tested at the standard and an altered level of FFB. In addition, the students' satisfaction with the training exercise was evaluated. METHODS: One hundred twenty-six first-year dental students were randomly distributed into four groups and underwent a manual dexterity test in the virtual reality environment with automatic assessment after a 3-month period of practicing with standard FFB. The test consisted of drilling with the standard FFB and an altered level of FFB to evaluate the effect on performance. After the test, the participants completed a questionnaire. RESULTS: The results showed that 74% of the students who passed completed between one of three and three of three successful attempts at FFB levels at which they had not previously practiced. CONCLUSIONS: The results of this study imply that if students practice a sufficient amount of time at one level of FFB, a skill is transferable from one level of FFB to another.

Acidic and alkaline chemicals' influence on a tricalcium silicate-based dental biomaterial.

Bioactive hydraulic tricalcium silicate materials are commonly used in several dental procedures. Mineral Trioxide Aggregate (MTA) is one such material, which is used in a variety of clinical applications, the most recent of which is root canal sealing material, during which, the MTA potentially comes in contact with remnants of the chemical agents used for disinfecting root canals. The effects of commonly used root canal irrigating solutions on MTA have not been investigated in depth, thus far. The aim of this study was to determine the effect of five common chemical agents used in root canal preparation (sodium hypochlorite/NaOCl, ethylene diaminetetraacetic acid/EDTA, mixture of sodium hypochlorite and etidronic acid/NaOCl + EA, mixture of EDTA and Chlorhexidine/QMix, or saline) on a commercial tricalcium silicate (MTA Plus). Samples were analyzed using scanning electron microscopy with energy dispersive spectroscopy, X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy and Inductively coupled plasma techniques to see effects of phases formed and calcium ion release. Specimens immersed in NaOCl and NaOCl + EA had strong peaks for calcium hydroxide, but materials exposed to EDTA and QMix had lesser XRD peaks for calcium hydroxide. The calcium hydroxide peak in the XRD indicates hydration of tricalcium silicate and formation of amorphous calcium silicate hydrate. Calcium released from samples immersed in EDTA and NaOCl was less than in NaOCl + EA and QMix solutions. Fewer calcium phosphate crystals and less calcium hydroxide were observed with the samples in NaOCl, EDTA and QMix, which could have an important impact as it negatively influences the bioactivity. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 107B: 377-387, 2019.

The Effect of Force Feedback in a Virtual Learning Environment on the Performance and Satisfaction of Dental Students.

INTRODUCTION: This study investigated the effect of force feedback (FFB) on student performance in a virtual learning environment (VLE) using the Simodont dental trainer (Moog, Nieuw-Vennep, the Netherlands) and evaluated the students' satisfaction with and without FFB. METHODS: The Simodont dental trainer, which was used as a VLE, was randomly assigned to 101 first-year dental students with no previous experience in cutting a tooth or working in a VLE with FFB. This study was designed as a crossover study. One half of the students practiced without FFB, whereas one half practiced with FFB. Both groups practiced four sessions lasting 45 minutes on a cross preparation. In the fifth session, test 1 was scheduled. After test 1, the same practicing and testing protocol was followed, although the environment was switched. After test 2, participants filled out a questionnaire. For the statistical analysis, only the questionnaires of the students who participated in both tests were processed. RESULTS: The results of test 1 and test 2 revealed that only students who used FFB were able to pass the tests. The questionnaire outcomes supported the results of both tests; 100% of the students preferred working with FFB. CONCLUSIONS: The results suggest that FFB is important for performance in a VLE and essential for satisfaction.

Calcium Hydroxide Treatment Does Not Alter the Susceptibility of Enterococcus faecalis Biofilms to Sodium Hypochlorite.

OBJECTIVE: To investigate the influence of calcium hydroxide (Ca(OH)2) on susceptibility to disinfection with sodium hypochlorite (NaOCl) of biofilm bacteria. METHODS: Monospecies biofilms of eight Enterococcus faecalis strains were subjected to a 2-h challenge with Ca(OH)2. After a recovery phase, the biofilms were treated with a concentration of NaOCl that was lower than the minimum inhibitory concentration. In a metabolic assay, the efficacy of NaOCl disinfection in Ca(OH)2-challenged biofilms and unchallenged biofilms was evaluated. The data were analyzed with Mann-Whitney U and Kruskall- Wallis tests. A P value of less than 0.05 was considered statistically significant. RESULTS: There were marginal differences in susceptibility to NaOCl among the E. faecalis strains. After the Ca(OH)2 challenge, seven strains remained equally susceptible to NaOCl disinfection whereas one strain became more resistant to NaOCl (P=0.03). CONCLUSION: After a Ca(OH)2 challenge, in general E. faecalis remained equally susceptible to disinfection with NaOCl.

Patterns of orodental injury and mouthguard use in Dutch field hockey.

BACKGROUND: Orodental injuries in field hockey are a growing cause of concern that requires attention. OBJECTIVE: The objective of this cross-sectional study was to investigate the patterns of orodental injury, and the use of mouthguards in Dutch national field hockey. MATERIALS AND METHODS: In the period from 1 May to 31 July 2014, a 33-item questionnaire about orodental injury and mouthguard use was sent to 7 field hockey clubs in the Netherlands. Data were analysed using 2 multivariable logistic (non-)linear regression per outcome measurement: (1) orodental injury and (2) type of mouthguard. RESULTS: Out of 6585 players, 1299 (20%) responded sufficiently and were eligible for the study. In total, 214 hockey players (16%) experienced at least 1 orodental injury in their career. The injuries were less severe in athletes who wore a mouthguard during an accident than in those who did not, OR=2.1 to 3.3, p≤0.05. Players without mouthguard sustained broken and knocked out teeth more frequently, while players with a mouthguard had more lip cuts (p≤0.05). Players complained less about custom-made than about mouth-moulded mouthguards (p≤0.05). Also, males were more at risk for an orodental injury, OR=1.4 (95% CI 1.0 to 1.9), and were less likely to have a custom-made mouthguard, OR=0.7 (95% CI 0.6 to 0.9), than females. CONCLUSIONS: A substantial number of field hockey players suffers from orodental injury. Mouthguards should be included in prevention strategies as they are associated with less severe injuries and patterns of injury are to be taken into account when targeting specific groups.

Additional disinfection with a modified salt solution in a root canal model.

OBJECTIVES: The aim of this study is to investigate the disinfecting properties of a modified salt solution (MSS) and calcium hydroxide (Ca(OH)2) in a non-direct-contact ex-vivo model. METHODS: Seventy-four single-canal roots infected with Enterococcus faecalis were treated with 1% sodium hypochlorite (NaOCl) irrigation or with NaOCl irrigation with subsequent dressing with MSS or Ca(OH)2. After removal of the dressings, the roots were filled with bacterial growth medium and incubated for seven days to enable the surviving bacteria to repopulate the root canal lumen. Growth was determined by sampling the root canals with paper points before treatment (S1), after treatment (S2) and incubation after treatment (S3). The colony forming units were counted at S1 and S2. At S3, growth was determined as no/yes regrowth. The Kruskal-Wallis, McNemar and χ(2) test were used for statistical analyses. RESULTS: At S2, in the NaOCl group, growth was found in 5 of 19 root canals. After the removal of MSS or Ca(OH)2 bacteria were retrieved from one root canal in both groups. At S3, repopulation of the root canals had occurred in 14 of 19 roots after sole NaOCl irrigation, 6 of 20 roots after MSS-dressing and in 14 of 20 roots after Ca(OH)2-dressing. MSS was more effective in preventing regrowth than Ca(OH)2 (P=0.009). CONCLUSIONS: The modified salt solution prevented regrowth in roots which indicates that it can eliminate persistent bacteria. Dressing the root canals with Ca(OH)2 did not provide additional disinfection after NaOCl irrigation.

Influence of Irrigation Sequence on the Adhesion of Root Canal Sealers to Dentin: A Fourier Transform Infrared Spectroscopy and Push-out Bond Strength Analysis.

INTRODUCTION: There is a lack of evidence on the chemical interaction between sealers and dentin. The influence of irrigation on the chemical interaction between root canal sealers and dentin was analyzed by using Fourier transform infrared spectroscopy (FTIRS) and measurement of dislocation resistance. METHODS: Single-rooted teeth (n = 120) were instrumented with 3% NaOCl as the irrigant and divided into 4 groups (n = 30) on the basis of irrigation protocol: group 1, 3% NaOCl, 17% EDTA, water; group 2, 17% EDTA, 3% NaOCl, water; group 3, 3% NaOCl, QMix, water; group 4, 3% NaOCl, water. Each group was divided into 3 subgroups (n = 10) on the basis of the root canal sealer: A, epoxy resin (AH Plus); B, silicone (RoekoSeal); C, calcium hydroxide (Sealapex). The dislocation resistance was assessed by using push-out bond strength test. The data were statistically analyzed by three-way analysis of variance and Holm-Sidak tests (P = .05). Dentin powder treated as per the conditioning protocols mentioned was mixed with the sealers and analyzed by FTIRS. RESULTS: A significant interaction was observed between irrigation protocol, type of sealer, and root segment (P < .001) for AH Plus but not for RoekoSeal and Sealapex (P > .05). AH Plus showed the highest bond strength (P < .05). FTIRS showed chemical bonding between AH Plus and dentinal collagen. In groups 2 and 4, no chemical bonding was observed. CONCLUSIONS: Bond strength of sealers is differentially affected by the irrigation protocol. The epoxy resin sealer AH Plus chemically bonds to dentinal collagen. This interaction is influenced by the irrigation protocols.

Outcome of Direct Pulp Capping with Mineral Trioxide Aggregate: A Prospective Study.

INTRODUCTION: The aim of this experimental study was to assess the outcome of direct pulp capping with mineral trioxide aggregate (MTA) after complete excavation of caries in permanent dentition with a 2-visit treatment protocol. METHODS: Sixty-four teeth with deep carious lesions were consecutively selected. The mean age of the patients was 36.1 ± 15 years. An initial diagnosis of deep caries, with no irreversible pulp involvement, was made. Excavation of caries was performed under a rubber dam and operating microscope magnification. White MTA was applied, and a provisional restoration was placed. At the following appointment, positive sensibility testing and the MTA setting were confirmed. Bonded composite restorations were placed afterward. The patient was recalled at least 1 year after treatment for clinical and radiographic control. Outcome was described as success or failure. Success was defined as lack of complaints from the patient, positive reaction to cold testing, no sensitivity to percussion, and no widening of the periodontal ligament on the recall periapical radiograph. RESULTS: Forty-six teeth (77.9%) were recalled after 3.6 years (standard deviation = 1.1 years). The overall success rate was 91.3%. The success rate in occlusal caries was 100% and 89.7% in proximal caries (difference = 10.3%; 95% confidence interval [CI], 8.5-89.1). The success rate in initial caries was 94.7% and 88.9% in secondary caries (difference = 5.8%; 95% CI, -48.1 to 59.7). The success rate in patients younger than 40 years was 100% and 80% in patients aged 40 years or older (difference = 20%; 95% CI, 4.2-35.8). CONCLUSIONS: Direct pulp capping with MTA after pulp exposure during excavation of deep caries could maintain pulp vitality in permanent teeth when a 2-visit treatment protocol is observed.

Effect of a two-step placement procedure on the dislocation resistance of a methacrylate resin-based root canal sealer: a proof of concept.

PURPOSE: To investigate whether the placement of a methacrylate root canal sealer or a conventional epoxy root canal sealer in two steps increases their dislocation resistance when compared to a one-step placement procedure. MATERIALS AND METHODS: Eighty single-rooted teeth were randomly allocated to 4 groups (n=20). All canals were instrumented to size 40, 0.06 taper and irrigated according to a standardized protocol. Root canal filling was conducted as follows: group 1: methacrylate sealer placed in two steps; group 2: methacrylate sealer placed in one step; group 3: epoxy sealer placed in two steps; group 4: epoxy sealer placed in one step. After setting, thin slices at different root levels were obtained and submitted to push-out testing. RESULTS were analyzed with non-parametric tests to compare the two-step procedures to their one-step counterparts. Failure modes were determined by stereomicroscopy. Random untested methacrylate sealer specimens were also examined with scanning electron microscopy. RESULTS: At each root level, dislocation resistance was significantly higher for the two-step procedure than for the one-step procedure using the methacrylate sealer (p=0.003, p=0.005, p<0.001) but not the epoxy sealer (p=0.83, p=0.1, p=0.06). Among root levels, there were no significant differences in dislocation resistance in the methacrylate sealer two-step group, while all other groups showed differences. CONCLUSION: A two-step placement procedure resulted in significantly higher dislocation resistance for the methacrylate sealer but not for the epoxy sealer.

The validity of cone-beam computed tomography in measuring root canal length using a gold standard.

INTRODUCTION: The distance between a coronal reference point and the major apical foramen is important for working length determination. The aim of this in vitro study was to determine the accuracy of root canal length measurements performed with cone-beam computed tomographic (CBCT) scans using a gold standard. METHODS: A total of 162 teeth (198 root canals) in 16 dry human dentulous mandibles were scanned using a 3DX-Accuitomo CBCT scanner (Morita 3DX; J Morita Mfg Corp, Kyoto, Japan). The root canal length was measured with CBCT data. All teeth were extracted atraumatically and endodontically accessed; the root canal length was measured blindly using a #10 K-file (Dentsply Maillefer, Ballaigues, Switzerland) and served as the gold standard. RESULTS: The mean absolute difference of the CBCT-based root canal length from the gold standard was 0.46 mm (95% confidence interval, 0.41-0.50 mm). Only in 9 of 198 (4.5%) roots did the difference between the CBCT-based root canal length and the gold standard exceed 1 mm. CONCLUSIONS: CBCT-based root canal length measurements are accurate and reliable when compared with a gold standard.

Antimicrobial effect of a modified vanadium chloroperoxidase on Enterococcus faecalis biofilms at root canal pH.

INTRODUCTION: Previous research showed an antimicrobial effect of vanadium chloroperoxidase (VCPO) on in vitro Enterococcus faecalis biofilms. The current study aimed to optimize the use of this enzyme at the root canal pH using a modified VCPO (mVCPO) that was adapted to function at a higher pH and to explore the biocompatibility of mVCPO. METHODS: The activity of the original and modified VCPO was assessed using the monochlorodimedone assay. For antimicrobial assessment, 48-hour biofilms of E. faecalis OS-16 were incubated 5 or 30 minutes with mVCPO, bromide, and hydrogen peroxide, and colony-forming units were determined. A metabolic activity assay was used to evaluate the cytotoxic effect of mVCPO on oral fibroblasts. RESULTS: Reaction products generated by mVCPO at a root canal pH of 7.7 significantly inactivated the biofilm after 5 minutes and even more after 30 minutes (Mann-Whitney U test, P < .05). The mVCPO reaction products showed less cytotoxic effects than control solutions and 0.5% sodium hypochlorite (Kruskal-Wallis test, P < .05). CONCLUSIONS: The incubation of mVCPO in the presence of its substrates with in vitro E. faecalis biofilms showed a significant antimicrobial effect at the root canal pH. Also, cytotoxicity tests showed preliminary biocompatibility. Therefore, an interappointment dressing containing mVCPO could aid in improving current endodontic treatment through continuous and local generation of antimicrobials.

The incidence of root microcracks caused by 3 different single-file systems versus the ProTaper system.

INTRODUCTION: The aim of this study was to compare the incidence of root cracks observed at the apical root surface and/or in the canal wall after canal instrumentation with 3 single-file systems and the ProTaper system (Dentsply Maillefer, Ballaigues, Switzerland). METHODS: One hundred mandibular incisors were selected. Twenty control teeth were coronally flared with Gates-Glidden drills (Dentsply Maillefer). No further preparation was made. The other 80 teeth were mounted in resin blocks with simulated periodontal ligaments, and the apex was exposed. They were divided into 4 experimental groups (n = 20); the root canals were first coronally flared with Gates-Glidden drills and then instrumented to the full working length with the ProTaper, OneShape (Micro-Mega, Besancon, France), Reciproc (VDW, Munich, Germany), or the Self-Adjusting File (ReDent-Nova, Ra'anana, Israel). The apical root surface and horizontal sections 2, 4, and 6 mm from the apex were observed under a microscope. The presence of cracks was noted. The chi-square test was performed to compare the appearance of cracked roots between the experimental groups. RESULTS: No cracks were found in the control teeth and teeth instrumented with the Self-Adjusting File. Cracks were found in 10 of 20 (50%), 7 of 20 (35%), and 1 of 20 (5%) teeth after canal instrumentation with the ProTaper, OneShape, and Reciproc files, respectively. The difference between the experimental groups was statistically significant (P < .001). CONCLUSIONS: Nickel-titanium instruments may cause cracks on the apical root surface or in the canal wall; the Self-Adjusting File and Reciproc files caused less cracks than the ProTaper and OneShape files.

Effects of self-adjusting file, Mtwo, and ProTaper on the root canal wall.

INTRODUCTION: The purpose of this ex vivo study was to observe the incidence of cracks in root dentin after root canal preparation with hand files, self-adjusting file (SAF), ProTaper, and Mtwo. METHODS: One hundred extracted mandibular premolars with single canals were randomly selected. Two angulated radiographs were taken for each tooth, and the width of the canal was measured at 9 mm from the apex. Five groups of 20 teeth each were comparable in canal width. The control group was left unprepared. Four experimental groups were instrumented with hand files, ProTaper, Mtwo, and SAF. Roots were then sectioned horizontally and observed under a microscope. The presence of dentinal cracks and their location were noted. The difference between the experimental groups was analyzed with a χ(2) test. RESULTS: No cracks were observed in the control group. In the experimental groups, ProTaper, Mtwo, and SAF caused cracks in 35%, 25%, and 10% of teeth, respectively. The hand-file group did not show any dentinal cracks (P < .0001). ProTaper and Mtwo caused more cracks than hand files (P < .05), but SAF did not (P > .05). CONCLUSIONS: Instrumentation of root canals with SAF, Mtwo, and ProTaper could cause damage to root canal dentin. SAF has a tendency to cause less dentinal cracks as compared with ProTaper or Mtwo.

Incidence of apical root cracks and apical dentinal detachments after canal preparation with hand and rotary files at different instrumentation lengths.

INTRODUCTION: The aim of this study was to compare the incidence of apical root cracks and dentinal detachments after canal preparation with hand and rotary files at different instrumentation lengths. METHODS: Two hundred forty mandibular incisors were mounted in resin blocks with simulated periodontal ligaments, and the apex was exposed. The root canals were instrumented with rotary and hand files, namely K3, ProTaper, and nickel-titanium Flex K files to the major apical foramen (AF), short AF, or beyond AF. Digital images of the apical surface of every tooth were taken during the apical enlargement at each file change. Development of dentinal defects was determined by comparing these images with the baseline image. Multinomial logistic regression test was performed to identify influencing factors. RESULTS: Apical crack developed in 1 of 80 teeth (1.3%) with hand files and 31 of 160 teeth (19.4%) with rotary files. Apical dentinal detachment developed in 2 of 80 teeth (2.5%) with hand files and 35 of 160 teeth (21.9%) with rotary files. Instrumentation with rotary files terminated 2 mm short of AF and did not cause any cracks. Significantly less cracks and detachments occurred when instrumentation with rotary files was terminated short of AF, as compared with that terminated at or beyond AF (P < .05). The AF deviated from the anatomic apex in 128 of 240 teeth (53%). Significantly more apical dentinal detachments appeared in teeth with a deviated AF (P = .033). CONCLUSIONS: Rotary instruments caused more dentinal defects than hand instruments; instrumentation short of AF reduced the risk of dentinal defects.

Sodium chloride and potassium sorbate: a synergistic combination against Enterococcus faecalis biofilms: an in vitro study.

Incomplete disinfection of the root canal system is a major cause of post-treatment disease. This study aimed to investigate the disinfecting property of organic acid salts and sodium chloride (NaCl), in a double-hurdle strategy, on Enterococcus faecalis biofilms. First of all, the high-throughput resazurin metabolism assay (RMA) was used to test a range of organic acid salts. Then, to gain more insight into the efficacy of sorbate salt solutions, 48-h E. faecalis biofilms were evaluated in colony-forming unit (CFU) assays. Chlorhexidine (CHX) and calcium hydroxide [Ca(OH)(2) ] were tested in parallel as controls. Sorbate salt produced the largest and most significant reduction of fluorescence intensity in the RMA assay. Neither NaCl nor potassium sorbate (KS) alone induced a clinically relevant reduction of CFU counts after 1 h. Surprisingly, the combination of the two in a single solution had a synergistic effect on the inactivation of E. faecalis. Potassium sorbate amplified the efficacy of NaCl. Of the salts tested, NaCl with KS eradicated E. faecalis biofilms within 1 h. This study showed that the double-hurdle strategy indeed leads to synergistic efficacy and is a possible next step in the complete disinfection of endodontic infections.

Removal of gutta-percha from root canals using the self-adjusting file.

INTRODUCTION: The aim of this study was to compare the percentage of the residual gutta-percha-occupied area (PRGPA) in root canals after retreatment using ProTaper retreatment files (Dentsply Maillefer, Ballaigues, Switzerland) with or without the additional use of Self-Adjusting Files (SAFs; ReDent-Nova, Ra'anana, Israel). METHODS: Root canals in 33 curved mesiobuccal roots of the first maxillary molars were cleaned and filled with gutta-percha and AH26 sealer (Dentsply De Trey, Johnson City, TN). Retreatment instrumentation was performed in 28 roots with ProTaper retreatment files and Hedström files. The Additional use of SAF was performed in 14 of the 28 roots. Five roots were not retreated. All roots were sectioned horizontally at 2, 4, and 6 mm from the apex. PRGPA was measured at each section. Scores 1 through 5 were used to represent the increasing extent of PRGPA; score 1 was 0%, and score 5 was >30%. The data were analyzed with nonparametric tests. RESULTS: Score 5 was recorded in all sections from roots that were not retreated. In retreated roots, the scores for the group using SAF were significantly lower than that without using SAF (P = .045); however, scores were higher at 2 mm than at other levels of the root regardless of whether the SAF had been used (P = .03). CONCLUSIONS: The complete removal of gutta-percha from the apical portion of curved canals remains a challenge. The additional use of SAF removed more gutta-percha than ProTaper alone.