Mastery Learning in Preclinical Endodontics Using Customized 3D-Printed Tooth Models for Deliberate Practice: An Application of Educational Design Research.

INTRODUCTION: This study, conducted within an educational design research (EDR) framework, assessed the use of customized 3D-printed tooth models at various difficulty levels to enhance mastery learning and deliberate practice in preclinical endodontic training. METHODS: The EDR was conducted in a preclinical endodontic training involving 42 third-year students. The study focused on developing and evaluating 3D-printed tooth models customized into 3 difficulty levels to facilitate mastery learning for the access opening procedure on upper anterior teeth. To promote deliberate practice, we ensured ample availability of these models. The evaluation combined quantitative analysis, using Friedman and Wilcoxon Signed-Rank tests to assess practice volume and performance, with qualitative feedback from interviews and focus groups, analyzed via content analysis. RESULTS: There was a significant reduction in practice time across the different model levels, with students using an average of 1.5-1.8 models per level. No significant differences in performance scores were observed across levels and natural tooth (P = .333). Feedback highlighted the models' educational value in enhancing dental training, indicating their effectiveness in improving learning experiences and skill development in endodontic education. CONCLUSIONS: The innovative design of a 3D-printed tooth model system, which features 3 levels of difficulty and was developed within an EDR framework, allowed for tailored learning progressions and ample practice opportunities. This significantly enhanced the endodontic training experience and skill development by providing varied and realistic challenges.

Prevalence and virulence factors of haemolytic Enterococcus faecalis isolated from root filled teeth associated with periradicular lesions: A laboratory investigation in Thailand.

AIM: Previous endodontic research has provided limited understanding of the prevalence and roles of haemolytic and non-haemolytic Enterococcus faecalis strains in root filled teeth. This study aimed to determine the prevalence of these strains in root filled teeth with periradicular lesions and investigate their associated virulence factors. METHODOLOGY: A total of 36 root canal samples were collected from 36 subjects. The prevalence of E. faecalis was determined using culture and PCR methods. Antibiotic susceptibility of haemolytic and non-haemolytic E. faecalis strains was assessed using the broth dilution assay. The cytokine stimulation in periodontal ligament (PDL) cells and neutrophil migration were evaluated using real-time PCR and migration assay, respectively. Cell invasion ability of the strains was assessed using a cell culture model. Additionally, the virulence gene expression of the haemolytic and non-haemolytic strains was investigated using real-time PCR. The Mann-Whitney U and Spearman's ρ tests were used to examine the significant difference between the two strains and to analyse the correlation between phenotype and gene expression, respectively. RESULTS: Enterococcus faecalis was detected in 33.3% and 88.9% of samples by culture and real-time PCR, respectively. Haemolytic strains were found in 36.4% of subjects. Non-haemolytic strains exhibited susceptibility to erythromycin and varying susceptibility to tetracycline, while all haemolytic strains were resistant to both antibiotics. Haemolytic strains significantly upregulated the expression of IL-8, OPG and RANKL in PDL cells (p < .05). Notably, the fold increases in these genes were higher: IL-8 (556.1 ± 82.9 vs. 249.6 ± 81.8), OPG (2.2 ± 0.5 vs. 1.3 ± 0.2) and RANKL (1.8 ± 0.3 vs. 1.2 ± 0.1). Furthermore, haemolytic strains had a greater effect on neutrophil migration (68.7 ± 15.2% vs. 46.9 ± 11.4%) and demonstrated a higher level of internalization into oral keratinocyte cells (68.6 ± 0.4% vs. 33.8 ± 0.5%) (p < .05). They also showed enhanced expression of virulence genes associated with haemolysin, surface proteins, collagen-binding and aggregation substances. Gelatinase activity was only detectable in non-haemolytic strains. CONCLUSIONS: This study revealed that haemolytic strains E. faecalis possessed enhanced abilities in host invasion and a higher abundance of virulence factors, suggesting their potential contribution to more severe disease manifestations.

Assessing methodological quality in dental education research using MERSQI: Analysis of publications from two journals.

PURPOSE: The Medical Education Research Study Quality Instrument (MERSQI) has been used frequently to assess the methodological quality of medical education but not for dental education. The present study aimed to assess the methodological quality using MERSQI scores of articles published in the Journal of Dental Education (JDE) and the European Journal of Dental Education (EJDE). METHODS: A cross-sectional assessment of the quality of manuscripts published in 2012, 2017, and 2022 JDE and EJDE was conducted. MERSQI data, numbers of authors, first and corresponding author degrees, geographic origins, and funding information were also extracted for each included study. Descriptive and analytical statistics were conducted, and significance level was set at α < 0.05. RESULTS: Four hundred ninety-five articles met the inclusion criteria. The most common study design was a single-group cross-sectional or single-group posttest and conducted in one institution for all studied years. In all journals and years, studies were assessed mainly by participants. The study outcome was mostly satisfaction, attitudes, perceptions, opinions, and general facts. The total mean MERSQI score for each journal and year varied. Year and geographic origin significantly affected the total MERSQI score. Papers originating from Asia had the highest score, followed by South America, Europe, North America, Oceania, and Africa. CONCLUSION: MERSQI score is applicable to the assessment of the methodological quality of dental educational research. The MERSQI score for most of the domains was similar for both journals. The MERSQI score was affected by publication years and geographic origins.

The effect of incomplete crown ferrules on fracture resistance and failure modes of endodontically treated maxillary incisors restored with quartz fiber post, composite core, and crowns.

AIM: To investigate the fracture resistance of restored endodontically treated teeth (RETT) with fiber posts, cores, and crowns with limited ferrules. MATERIALS AND METHODS: Sixty maxillary anterior teeth were endodontically treated and decoronated 2 mm above the cemento-enamel junction, and then divided into 6 groups of 10 teeth each; Group circumferential ferrule (2FR), Group ferrule in the labial, mesial, and palatal region (2FR-LaMPa), Group ferrule in the labial, and palatal region (2FR-LaPa), Group 2FR-Pa and 2FR-La respectively, and Group 0FR (no ferrule). All 60 prepared teeth were then restored with quartz fiber posts, resin composite cores, and metal crowns. The specimens were subjected to load until failure occurred. Data were analyzed using one-way analysis of variance and Tukey's tests (α = 0.05). The mode of failure was determined under a stereoscope. RESULTS: A statistical significant difference was found among groups 2FR-LaMPa, 2FR-Pa, 2FR-LaPa, and 2FR from the group 2FR-La, and from the group 0FR (P < 0.01). The predominant mode of failure was an oblique palatal to labial root fracture for the groups with remaining ferrules. CONCLUSION: For RETT that have incomplete crown ferrules, the location of the ferrules may affect their fracture resistance.

Effectiveness of Artocarpus lakoocha extract, poloxamer 407, on Enterococcus faecalis in vitro.

AIM: The antiviral activities of Artocarpus lakoocha (A. lakoocha) extract have been reported in a number of studies; however, data regarding its antibacterial capability are limited. The aim of the present study was to examine the effectiveness of A. lakoocha extract, poloxamer 407, on Enterococcus faecalis (E. faecalis). METHODS: The effect of the antimicrobial activity of A. lakoocha extract and A. lakoocha extract, poloxamer 407, against E. faecalis was investigated. The antibacterial efficacy of A. lakoocha extract, poloxamer 407, against E. faecalis was compared to calcium hydroxide in a tooth model. RESULTS: The minimal inhibitory concentration and minimal bactericidal concentration (MBC) of A. lakoocha extract against E. faecalis were 0.39 ± 0 mg/mL and 3.12 ± 0 mg/mL, respectively; the MBC of calcium hydroxide against E. faecalis was 31.25 ± 0 mg/mL. In the tooth model, the E. faecalis count in all groups significantly decreased as the depth into the dentin increased compared to the control. There were no significant differences between 4% A. lakoocha extract poloxamer and UltraCal XS at any time period (P > 0.05) with one exception: at a depth of 0.6 mm on day 5, UltraCal XS had a significantly greater colonization than 4% A. lakoocha extract poloxamer. CONCLUSION: A. lakoocha extract, poloxamer 407, might be a useful alternative for antimicrobial medication in endodontic treatment. However, controlled clinical studies to evaluate its efficacy are needed.

Simvastatin induces apoptosis and disruption of the actin cytoskeleton in human dental pulp cells and periodontal ligament fibroblasts.

OBJECTIVE: Simvastatin, a competitive inhibitor of 3-hydroxy-3-methylglutaryl coenzyme A reductase, and widely used as cholesterol-lowering agent, has been suggested for its beneficial effects on alveolar bone formation, regeneration of dental pulp tissue and periodontal ligament. High doses of simvastatin appear to induce apoptosis in several cell types, but little is known about its possible effect on tooth-associated cells. Therefore, the effects of simvastatin were studied on apoptosis and cell morphology of human dental pulp cells (HDPCs) and periodontal ligament fibroblasts (HPLFs). METHODS: HDPCs/HPLFs obtained from 4 patients were cultured with or without various concentrations of simvastatin (0.1, 1, and 10µM) for 24, 48, and 72h. The 3-(4,5-dimethyl-thiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay was performed to evaluate cell viability. The levels of apoptosis of HDPCs and HPLFs were measured by flow cytometry after Annexin V/propidium iodide double staining. Phalloidin-FITC and 4',6-diamidino-2-phenylindole dihydrochloride (DAPI) staining was used to examine differences in the actin cytoskeleton and nuclear morphology, respectively. RESULTS: The viability of HDPCs and HPLFs was significantly reduced after simvastatin treatment in a dose- and time-dependent manner (p<0.05). The apoptosis of HDPCs and HPLFs was significantly increased in 10µM simvastatin-treated cells (p<0.05). The effect on apoptosis was comparable for HDPCs and HPLFs. Nuclear staining showed typical apoptotic nuclear condensation and fragmentation in simvastatin-treated HDPCs/HPLFs. A dose- and time-dependent simvastatin-induced disruption of the actin cytoskeleton was observed in both cell types. CONCLUSION: Our data demonstrated that simvastatin decreases the viability of HDPCs and HPLFs, probably by inducing apoptosis.

Optimal acidulated phosphate fluoride gel etching time for surface treatment of feldspathic porcelain: on shear bond strength to resin composite.

OBJECTIVES: This in vitro study evaluated the shear bond strength (SBS) of resin composite to feldspathic porcelain after acidulated phosphate fluoride (APF) gel treatment over different periods of time. METHODS: One hundred and fifty-six feldspathic specimens were divided into 12 groups. Group C received no treatment (control group). Groups APF1 through APF10, ten experimental groups, were treated with 1.23% APF gel. Each group obtained 1 to 10 minutes of etching time in 1 minute increments, respectively. Group HF2 was treated with 9.6% hydrofluoric acid (HF) for 2 minutes. All specimens were then bonded to a resin composite cylinder using Adper Scotchbond Multi-purpose (3M ESPE) after silane (Monobond-S, Ivoclar Vivadent AG) application. Specimens were stored at 37ºC for 24 hours before the SBS was performed and were recorded in MPa at fracture. Data were analyzed using one-way ANOVA and Tukey's test (α=.05). RESULTS: HF etching yielded the highest SBS (18.0 ± 1.5 MPa), which was not significantly different from APF gel etching for 6 to 10 minutes (16.0 ± 2.1 to 17.2 ± 1.6 MPa) (P>.05). CONCLUSIONS: APF gel etching for 6 minutes might be used as an alternative etchant to HF acid for bonding resin composite to silanized feldspathic porcelain.

Effect of novel chitosan-fluoroaluminosilicate glass ionomer cement with added transforming growth factor beta-1 on pulp cells.

INTRODUCTION: Vital pulp therapy might benefit from the sustained release of transforming growth factor beta-1 (TGF-ß1) from dental restorative materials. Chitosan has previously been shown to enable sustained release of bovine serum albumin (BSA) from glass ionomer cement (GIC). Because BSA can prolong release of growth factor, chitosan-fluoroaluminosilicate GIC with albumin (BIO-GIC) should sustain the effect of growth factor. This study investigated the effect of BIO-GIC with added TGF-ß1 on pulp cells. METHODS: BIO-GIC was prepared from GIC (conventional type) incorporated with 15% of chitosan and 10% of BSA. TGF-ß1 (100 ng) was added in BIO-GIC+TGF-ß1 and GIC+TGF-ß1 groups during each disk specimen (10 mm diameter, 1 mm high) preparation. Two control groups were BIO-GIC and GIC. The effect of each specimen on pulp cells was investigated by using the Transwell plate technique. Cell proliferation was determined by MTT assay at 2 time periods (each period lasting 3 days). Pulp cell differentiation was examined by alkaline phosphatase activity and also by cell mineralization, which was measured by calculating the area of mineralization with von Kossa staining. RESULTS: Percentage of viable cells of GIC+TGF-ß1 group was the highest after the first period. This might suggest an initial rapid release of TGF-ß1 from GIC. After the second period, BIO-GIC, BIO-GIC+TGF-ß1, and GIC+TGF-ß1 had more than 90% cell survival. It was significantly greater than GIC (82% ± 2%). There was no significant difference in alkaline phosphatase activity. BIO-GIC+TGF-ß1 had the highest mineralization area during 21 days. CONCLUSIONS: BIO-GIC could retain the effect of TGF-ß1.

Students' perceptions of prosthodontics in a PBL hybrid curriculum.

PURPOSE: A survey was distributed to the Harvard School of Dental Medicine (HSDM) predoctoral student classes of 2005 and 2006 to assess their perceptions regarding preclinical prosthodontics laboratory exercises. Prosthodontics curriculum clock hours, prosthodontics teaching participation, and plans for specialization were also analyzed. We hypothesized that reduced hours and perceived stress in the prosthodontics curriculum might impact students' choice of specialty at HSDM. MATERIALS AND METHODS: HSDM preclinical prosthodontics clock hours were compared with national means from published data. A survey was distributed to the HSDM classes of 2005 and 2006 (n = 70) at the end of their preclinical prosthodontics laboratory exercises, prior to students seeing their first patient in the clinics. RESULTS: A 100% response rate was achieved. Results from this study show that HSDM preclinical prosthodontics clock hours are on average shorter than other schools. The majority of the students felt stressed during the laboratory exercises, and they felt they did not gain adequate knowledge from the lectures, resulting in low self-esteem (confidence) in treating patients in the clinic. Despite this perception, HSDM students do just as well, if not better, than other students, as judged by external and internal outcome measures. Graduate prosthodontics specialization is still a specialty of choice among the graduates when compared to national data. CONCLUSIONS: The shortened preclinical didactic and laboratory exercises in prosthodontics at HSDM affect student anxiety, but not their didactic and clinical performances or their decisions in choosing their graduate program. Problem-based learning (PBL) tutorials help the students to integrate preclinical and clinical knowledge and skills in prosthodontics.

The impact of targeted shortened preclinical exercises on student perceptions and outcomes.

The Harvard School of Dental Medicine (HSDM) introduced problem-based learning (PBL) into the dental curriculum in 1994 as a part of curriculum reform. During the reorganization, departments were consolidated, and courses were taught in an interdisciplinary fashion rather than in a discipline-based approach. The changes required a reduction in lecture and preclinical clock hours, which might have affected student performance and anxiety levels. The objectives of this study were to 1) compare the HSDM didactic and laboratory preclinical hours in Endodontics, Operative, and Prosthodontics before and after PBL implementation; 2) compare the HSDM didactic and laboratory preclinical hours in Endodontics, Operative, and Prosthodontics with other schools nationwide; 3) measure students' perceptions of their levels of stress and self-confidence at two time points during their preclinical and clinical years; 4) investigate the correlation between the number of preclinical hours and the students' stress level and self-confidence; and 5) evaluate the impact of shortened preclinical hours on the performance of HSDM students on the National Board Dental Examination Parts I and II. A survey regarding the students' level of stress, self-confidence, and preparation to treat patients during preclinical laboratory exercises was distributed to the HSDM classes of 2005 and 2006 (n=70). The HSDM preclinical curriculum hours were compared to national data as reported by the American Dental Association (ADA). Cross-tabulations were constructed, and the Fisher's exact test was conducted to examine the relationships between the variables. We found that HSDM preclinical hours in Endodontics, Operative, and Prosthodontics were significantly lower than at other schools. During the preclinical exercises, the Prosthodontics preclinical exercises were found to be the most stressful and provided the lowest self-confidence in treating patients as compared to the other preclinical subject areas. HSDM students' scores on the National Board Part I and II examinations continue to be among the highest in the nation and have not been affected by the change in curriculum. We conclude that the change in HSDM's curriculum that resulted in targeted, shorter preclinical exercises has not affected clinical and didactic outcomes, but may have affected the anxiety that students feel when entering the clinic.

Problem-based learning at the Harvard School of Dental Medicine: self-assessment of performance in postdoctoral training.

Problem-based learning (PBL) was implemented into the dental curriculum at the Harvard School of Dental Medicine (HSDM) in 1994 with an expectation that this pedagogy would enhance students' critical thinking and communication skills as well as general professional competencies. Previous studies have described several aspects of the outcome of PBL curricula at the predoctoral level. However, there is no information available on the perceptions and performance of PBL graduates during their postdoctoral training in dentistry. The purpose of this study was to evaluate the effect of PBL methodology on the performance of HSDM graduates during their postdoctoral training in comparison with their non-HSDM (traditional) co-residents. Surveys containing traditional knowledge-based criteria, preclinical and clinical criteria, and PBL criteria were sent to HSDM graduates from the classes of 2002 through 2004 who were in postgraduate training programs. The HSDM and traditional graduates were asked to evaluate and compare their performance in selected areas with those of their co-residents from either a PBL curriculum or a traditional curriculum. The directors of each program were also asked to assess HSDM graduates relative to other graduates in the program based on the same aspects. Overall, HSDM graduates rated themselves more highly than non-HSDM graduates on all competencies. No significant difference between HSDM and non-HSDM responses was found in general dental knowledge, specialty specific knowledge, preclinical skills, clinical skills, communication with staff, and patient education, whereas significant differences (p<0.05) were found for communication with patients, critical thinking, independent learning, performance in small group settings, self-assessment, and teamwork. The data obtained from the program directors revealed corresponding results. The HSDM graduates' capacity for independent learning was rated as "excellent" by 65.31 percent of the directors and 80.95 percent of the HSDM graduates themselves. These findings suggest that the performance of HSDM graduates during their postdoctoral training met expectations and were similar to non-HSDM graduates for traditional residency program competencies. However, the PBL training appears to provide HSDM graduates with enhanced abilities in independent learning, communication, and cooperation skills.

The effect of different etching times of acidulated phosphate fluoride gel on the shear bond strength of high-leucite ceramics bonded to composite resin.

STATEMENT OF PROBLEM: A 10-minute treatment with acidulated phosphate fluoride (APF) gel has been used as an alternative in ceramic surface etching before repairing with composite resin. However, the optimal etching time for APF gel is still unknown. PURPOSE: The purpose of this study was to determine the in vitro shear bond strengths of composite resin on high-leucite ceramics after APF gel treatment over different time periods. MATERIAL AND METHODS: One hundred and twenty high-leucite ceramic (Empress 1) specimens (12 mm in diameter and 1.5 mm thick) were prepared and divided into 12 groups (n=10). Ten experimental groups were surface treated with 1.23% APF gel, each group receiving 1 to 10 minutes of etching time in 1 minute increments. One group was treated with 9.6% hydrofluoric acid for 4 minutes and the final group received no treatment and served as a control. The surface condition of the treated specimens was analyzed under a scanning electron microscope (SEM). All specimens received a silane application and were bonded to a composite resin Filtek (Z250) cylinder with an adhesive system (Scotchbond Multi-Purpose Plus adhesive) and then stored in 100% humidity at 37 degrees C for 24 hours before shear bond strength testing in a universal testing machine. Mean bond strengths (MPa) were analyzed with 1-way ANOVA and the Tukey HSD test (alpha=.05). RESULTS: Hydrofluoric acid etching produced the highest mean shear bond strength (SD) between composite resin and the ceramic (17.64 (1.48) MPa). Overall, APF gel etching produced lower bond strengths. No significant difference in mean bond strength (SD) was observed between etching with hydrofluoric acid and etching with APF gel for 7 to 10 minutes (15.21 (1.93) to 17.33 (1.43)). The lowest mean shear bond strengths (SD) were recorded in the untreated group (7.61 (1.03) MPa) (P<.05). CONCLUSIONS: Within the limitations of this study, shear bond strength values between composite resin and high-leucite ceramics after etching with 1.23% APF gel for 7 to 10 minutes were not significantly different than that after etching with 9.6% hydrofluoric acid for 4 minutes.

Role of macrophages in LPS-induced osteoblast and PDL cell apoptosis.

In periradicular lesions and periodontal disease, bacterial invasion leads to chronic inflammation resulting in disruption of the structural integrity of the periodontal ligament and progressive alveolar bone destruction. The pathogenesis of these conditions has been attributed not only to bacterial-induced tissue destruction but also to a defect in periodontal tissue repair. Accumulated data have also shown that lipopolysaccharide (LPS) can directly induce cell death or apoptosis in many cell types, including macrophages, osteoblasts, vascular endothelial cells, hepatocytes and myocytes. The present study hypothesized that bacterial LPS-induced apoptosis in osteoblasts and periodontal ligament fibroblasts (PDL cells) is an important contributing factor to the defect in periodontal tissue repair in periodontal and periapical disease. Macrophages have been shown to respond to bacterial LPS by increasing the production of proinflammatory cytokines. In addition, large numbers of macrophages are present in inflamed periodontal tissue. We speculated that macrophages were a potential candidate cell for mediating apoptosis in osteoblasts and PDL cells in response to bacteria-derived LPS. The macrophage-like cell line, RAW 264.7, was stimulated with LPS, and the conditioned medium was used to treat osteoblasts and PDL cells. Bacterial LPS had no direct apoptotic effect on mouse osteoblasts or PDL cells, whereas the conditioned medium from LPS-activated macrophages was able to induce apoptosis in these cells. To evaluate the contribution of tumor necrosis factor-alpha (TNF-alpha) released from macrophages on osteoblast and PDL cell apoptosis, cells were incubated with conditioned medium from LPS-treated macrophages in the presence and absence of anti-TNF-alpha neutralizing antibodies. TNF-alpha neutralizing antibody pretreatment inhibited the effect of conditioned medium from LPS-treated macrophages on osteoblast and PDL cell apoptosis in a dose-dependent manner. These results suggest that LPS could indirectly induce apoptosis in osteoblasts and PDL cells through the induction of TNF-alpha release from macrophages. These studies provide insight into a potential mechanism by which bacterial-derived LPS could contribute to defective periodontal and bone tissue repair in periodontal and periapical disease.