The Effect of Various Fluoride Products on Dentine Lesions during pH-Cycling.

This study compared the effect of topically applied fluoride products on dentine lesions in an in vitro experiment. Demineralized bovine dentine specimens were treated once with either SDF solution (35,400 ppm F), NaF varnish (22,600 ppm F), TiF4 solution (9,200 ppm F), SnF2 gel (1,000 ppm F), no treatment (control), or preserved as baseline lesions. After the application and subsequent removal of the fluoride products, the specimens were subjected to pH-cycling. Calcium loss and uptake in the de- and remineralization buffers were assessed daily. Fluoride release into the buffers was analyzed on days 1, 2, 3, 5, 8, and 13. After the pH-cycling period, mineral distribution throughout the lesion depth was analyzed using transversal microradiography (TMR). X-ray energy-dispersive spectroscopy (EDS) examined the deposition of silver, titanium, and tin after application of SDF, TiF4, and SnF2, respectively. Overall, calcium loss and uptake analysis in the de- and remineralization buffers revealed that the SDF product was the most effective in inhibiting lesion progression, followed by the TiF4, NaF, and SnF2 products. Fluoride analysis disclosed a steep reduction of the amount of fluoride released into de- and remineralization buffers with time. The fluoride effects on de- and remineralization continued beyond the days that fluoride was released into the buffers. TMR analysis showed significant remineralization in the outer zone of the dentine lesions for all fluoride products, with SDF giving hypermineralization in this zone. In the inner zone, lesions developed in all fluoride groups, with the smallest in the SDF group. EDS showed silver and titanium deposition in depth up to 85 µm and 8 µm, respectively, while no tin deposition was observed. The silver in the dentine lesions did not contribute significantly to the density of the TMR profiles in the SDF group. In conclusion, all topical fluoride products protected the dentine lesions against lesion progression, but at different degrees. SDF showed a superior effect in protection against further demineralization and enhancement of remineralization. This was probably attributed to its fluoride concentration that was the highest among the fluoride products.

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.

Anti-erosive effects of fluoride and phytosphingosine: an in vitro study.

A selection of commercially available products containing stannous fluoride (SnF2 )/sodium fluoride (NaF), SnF2 /amorphous calcium phosphate (ACP), SnF2 /NaF/ACP, tin (Sn)/fluorine (F)/chitosan were compared with phytosphingosine (PHS) with respect to their anti-erosive properties in vitro. One-hundred and twenty bovine enamel specimens were immersed in the respective product slurries for 2 min, twice daily. The formulations were diluted with either remineralization solution or artificial saliva. After each treatment, an erosive challenge was performed for 10 min, twice daily, using citric acid, pH 3.4. The specimens were stored in remineralization solution or artificial saliva until the next treatment-erosion challenge. After 10 d, tissue loss was determined using profilometry. Enamel softening was determined through surface microhardness measurements. Tissue-loss values (measured in µm and expressed as mean ± SD) for PHS, SnF2 /NaF, SnF2 /ACP, SnF2 /ACP/NaF, and Sn/F/chitosan treatment groups and for the negative-control group, were, respectively, 35.6 ± 2.8, 15.8 ± 1.8, 22.1 ± 2.0, 22.9 ± 1.8, 16.2 ± 1.2, and 51.2 ± 4.4 in the presence of remineralization solution and 31.7 ± 3.3, 15.6 ± 2.9, 16.5 ± 2.7, 16.8 ± 2.1, 13.1 ± 3.0, and 50.7 ± 2.8 in the presence of artificial saliva. There were no significant differences in surface microhardness measurements between the treatment groups. In conclusion, PHS resulted in a significant reduction of tissue loss compared with the negative control, but in comparison, the toothpastes containing Sn(2+) and F(-) ions were significantly more effective compared with PHS.

Assessment of predictive performance of caries risk assessment models based on a systematic review and meta-analysis.

OBJECTIVES: To assess the predictive performance of caries risk assessment (CRA) models for prediction of caries increment for individuals based on a systematic review and meta-analyses. DATA/SOURCES: We included external validation studies assessing the predictive performance of CRA models for prediction of caries increment for individuals, using discrimination and calibration as the outcome parameters. PubMed, EMBASE, and CINAHL were searched electronically on 10th September 2020 to identify prediction modeling studies on external validation of CRA models. The risk of bias of the included studies was assessed using the Prediction model Risk Of Bias ASsessment Tool (PROBAST). STUDY SELECTION: A total of 22 studies with seven different CRA models were included. As for full Cariogram, the pooled area under the receiver operating characteristic curve (AUC) was 0.78 (95 %CI: 0.68; 0.85) based on eight studies regardless of the risk of bias levels, and 0.82 (95 %CI: 0.58; 0.93) based on four studies with low risk of bias only. The pooled observed: expected ratio (O:E ratio) of full Cariogram was 0.91 (95 %CI: 0.72; 1.14) based on 12 studies regardless of the risk of bias levels, and 0.89 (95 %CI: 0.71; 1.12) based on five studies with low risk of bias only. As for reduced Cariogram, the pooled AUC was 0.72 (95 %CI: 0.67; 0.77) based on six studies regardless of the risk of bias levels, and 0.74 (95 %CI: 0.45; 0.91) based on two studies with low risk of bias only. The pooled O:E ratio of reduced Cariogram was 0.84 (95 %CI: 0.59; 1.18) based on six studies regardless of the risk of bias levels, and 1.05 (95 %CI: 0.43; 2.59) based on two studies with low risk of bias only. Based on an insufficient number of studies for the other CRA models, the pooled AUCs ranged from 0.50 to 0.88, while the pooled O:E ratio ranged from 0.38 to 1.00. CONCLUSION: The average predictive performance of both full and reduced Cariogram seems to be acceptable. However, the evidence from research does not allow a firm conclusion on the performance of the other included CRA models, due to the insufficient number of high-quality studies. CLINICAL SIGNIFICANCE: Both full and reduced Cariogram were found to be reliable CRA models for prediction of caries increment in clinical practices for dental patients and communities for general populations. The reduced Cariogram showed better predictive performance and less burden in terms of time and resources to individuals than the full Cariogram. Therefore, the reduced Cariogram could be more recommended than the full Cariogram.

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.

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.

On the ecosystemic network of saliva in healthy young adults.

A dysbiotic state is believed to be a key factor in the onset of oral disease. Although oral diseases have been studied for decades, our understanding of oral health, the boundaries of a healthy oral ecosystem and ecological shift toward dysbiosis is still limited. Here, we present the ecobiological heterogeneity of the salivary ecosystem and relations between the salivary microbiome, salivary metabolome and host-related biochemical salivary parameters in 268 healthy adults after overnight fasting. Gender-specific differences in the microbiome and metabolome were observed and were associated with salivary pH and dietary protein intake. Our analysis grouped the individuals into five microbiome and four metabolome-based clusters that significantly related to biochemical parameters of saliva. Low salivary pH and high lysozyme activity were associated with high proportions of streptococcal phylotypes and increased membrane-lipid degradation products. Samples with high salivary pH displayed increased chitinase activity, higher abundance of Veillonella and Prevotella species and higher levels of amino acid fermentation products, suggesting proteolytic adaptation. An over-specialization toward either a proteolytic or a saccharolytic ecotype may indicate a shift toward a dysbiotic state. Their prognostic value and the degree to which these ecotypes are related to increased disease risk remains to be determined.