A discrete time-to-event model for the meta-analysis of full ROC curves.

The development of new statistical models for the meta-analysis of diagnostic test accuracy studies is still an ongoing field of research, especially with respect to summary receiver operating characteristic (ROC) curves. In the recently published updated version of the "Cochrane Handbook for Systematic Reviews of Diagnostic Test Accuracy", the authors point to the challenges of this kind of meta-analysis and propose two approaches. However, both of them come with some disadvantages, such as the nonstraightforward choice of priors in Bayesian models or the requirement of a two-step approach where parameters are estimated for the individual studies, followed by summarizing the results. As an alternative, we propose a novel model by applying methods from time-to-event analysis. To this task we use the discrete proportional hazard approach to treat the different diagnostic thresholds, that provide means to estimate sensitivity and specificity and are reported by the single studies, as categorical variables in a generalized linear mixed model, using both the logit- and the asymmetric cloglog-link. This leads to a model specification with threshold-specific discrete hazards, avoiding a linear dependency between thresholds, discrete hazard, and sensitivity/specificity and thus increasing model flexibility. We compare the resulting models to approaches from the literature in a simulation study. While the estimated area under the summary ROC curve is estimated comparably well in most approaches, the results depict substantial differences in the estimated sensitivities and specificities. We also show the practical applicability of the models to data from a meta-analysis for the screening of type 2 diabetes.

Erosive tooth wear and caries experience in children and adolescents with obesity.

CLINICAL SIGNIFICANCE: A large consumption of fermentable carbohydrates, for instance the high intake of sweetened beverages, is an important risk factor for overweight and obesity. As lemonades and fruit juices present high sugar content and quite low pH-values, overweight and obese children might also have an increased risk for dental caries and erosive tooth wear. OBJECTIVES: The aim was to analyze the prevalence and severity of erosive tooth wear and caries experience in children and adolescents with overweight, obesity and extreme obesity compared to children with normal weight and to determine a possible association between erosive tooth wear and caries experience. METHODS: 223 children (4-17 years, n = 1476 primary and n = 4110 permanent teeth) were examined using standardized dental indices (BEWE, ICDAS, DMFT). Demographic and socio-economic data, eating habits, oral hygiene, fluoride supply and details of medical history were obtained from a questionnaire. Weight classification was based on age- and gender-specific relative body mass indices (BMI). Statistical analyses were done by Chi2-tests, Kruskal-Wallis tests, logistic and linear regressions. To determine a possible association between erosive tooth wear and caries experience Chi2-tests (prevalence to prevalence) and Spearman correlations (severity to severity) were performed (p < 0.05). RESULTS: Erosive tooth wear and caries experience in primary and permanent teeth were significantly increased in children with obesity and extreme obesity compared to normal weight children (p < 0.05). Higher BMI, age, gender, and the consumption of erosive snacks/beverages were identified as statistically significant risk factors for erosive tooth wear. Higher BMI, age, socio-economic factors, poor toothbrushing habits, and consumption of cariogenic beverages were identified as significant caries risk factors. Erosive tooth wear and caries showed a weak correlation in children with (extreme) obesity (Φ = 0.110 to 0.248). CONCLUSIONS: Higher BMI of children and adolescents is significantly associated with a higher risk for erosive tooth wear and caries.

Dental Students' Factual and Procedural Knowledge Retention in Operative Dentistry in a Clinical Dental Curriculum.

The aim of this study was to evaluate dental students' retention of factual and procedural knowledge gained in a preclinical course in operative dentistry during a clinical dental curriculum. In 2017, all 157 seventh- to tenth-semester dental students at a dental school in Germany were asked to repeat the same written examination performed at the end of the preclinical course in the sixth semester. The examinations consisted of 30 multiple-choice questions covering factual and procedural knowledge. The percentage of correctly answered questions per exam and differences in correct answers between the original examination and the re-examination (per question) were analyzed. Students were also asked to self-rate their percentage of correctly answered questions and their knowledge in various disciplines of operative dentistry at the times of the original examination and the re-examination. After exclusions, data were analyzed for 129 students, for a participation rate of 82%. For the seventh- and tenth-semester students, the results on the original examination and the re-examination were not significantly different, while the eighth- and ninth-semester students performed significantly better on the original examination than the re-examination. In all semesters, procedural knowledge remained stable between the original examination and the re-examination, while factual knowledge decreased slightly. Their performance on the original examination was underestimated by the eighth- and ninth-semester students. All the students underestimated their performance on the re-examination. Students mostly rated their knowledge level significantly higher on the original examination than on the re-examination. Overall, this study found that factual and procedural knowledge gained in a preclinical course in operative dentistry was not increased during the clinical dental curriculum.

Perception of children with visible untreated and treated caries.

OBJECTIVES: This study aimed to analyse if children with untreated or treated caries (restorations/missing teeth) are perceived differently compared to children with healthy teeth and to explore possible differences in the perception by laypersons and dental experts. METHODS: Eye movements of female experts (n = 20) and laypersons (n = 18) were recorded by eye-tracking while paired images (neutral expression/teeth not visible; emotional expression/smiling, teeth visible) of children with healthy teeth, with visible untreated or treated caries (restorations/missing teeth as a consequence of caries treatment), each n = 13, were presented. First fixation, total fixation time and number of fixations on the areas of interest (eyes, nose, mouth) in the first two seconds of presentation were determined. Furthermore, the images were rated regarding arousal, valence and attractivity. Statistical analysis was performed using Mann-Whitney-U- and Kruskal-Wallis-tests (α = 0.05). RESULTS: Generally, laypersons spent more time exploring and fixating the eye region than the mouth, while dental experts more often first percept and longer and more often fixated the mouth region, especially in images with emotional expression. Dental experts, but not laypersons, were significantly longer fixating the mouth of children with untreated caries than the mouth of children with healthy teeth in images with emotional expression. When evaluating images with emotional expression, both dental experts and laypersons rated children with healthy teeth to be more attractive, pleasant and calm than children with untreated or treated caries. CONCLUSIONS: Children with visible treated and untreated caries were differently perceived by laypersons and dental experts than children with healthy teeth.

Premolar autotransplantation in juvenile dentition: quantitative assessment of vertical bone and soft tissue growth.

OBJECTIVE: Premolar autotransplantation represents an effective therapeutic option for the treatment of juvenile dentition with either aquired or congenital hypodontia. The objective of this prospective clinical study was to quantitatively assess bone and soft tissue levels after autogenous premolar transplantation by clinical and radiographic parameters. STUDY DESIGN: In the study, 26 premolars were transplanted in 20 patients after traumatic tooth loss (n = 16) or congenital aplasia (n = 10) in the anterior maxilla. Based on standardized photographic documentation, the relative soft tissue level was measured compared to the healthy adjacent teeth. Radiographic findings included evaluation of root resorption, pulp canal obliteration, and relative bone height. RESULTS: Average survival rate of transplanted premolars (n = 26) was 100% over a follow-up period of 29 months (range 10-60 months). The relative soft tissue level significantly increased by +1.1 mm (P < .01). Radiographs showed a tendency toward vertical bone growth. Continuous root development and signs of pulpal healing were observed postoperatively in 18 transplants (69.2%). CONCLUSIONS: Autogenous premolar transplantation represents a safe method to ensure functional and aesthetic rehabilitation in the anterior maxilla irrespective of the nature of tooth loss.

Enamel wear by antagonistic restorative materials under erosive conditions.

OBJECTIVES: This study aimed to analyse loss of enamel worn against composite, leucite glass ceramic or enamel antagonists under non-erosive and alternating or simultanuous erosive-attritive conditions. MATERIALS AND METHODS: Flat human enamel specimens were loaded (1 Hz, 300 g loading weight, each subgroup n = 12) with antagonists made from a hybrid-composite (Z250, 3 M Espe), a nano-composite (Filtek Supreme XTE, 3 M Espe), leucite glass ceramic (IPS Empress CAD LT, Ivoclar Vivadent) or enamel. Specimens were either submitted to mechanical loading in mineral solution (60 s) or to loading under alternating or simultaneous erosive conditions. For alternating erosion-attrition, specimens were eroded by citric acid (pH 2.6, 60 s) and then loaded with the respective antagonist for 60s. For simultaneous erosion-attrition, specimens were loaded with the respective antagonist while being immersed in citric acid (pH 2.6, 60 s). After each cycle, specimens were stored in water for 1 h. After 18 cycles, enamel loss was calculated profilometrically and statistically analysed by two-way ANOVA and Tukey's post-hoc tests (p < 0.05). RESULTS: Enamel loss (µm, mean ± standard deviation) was significantly highest for simultaneous erosion-attrition (ceramic 9.4 ± 1.1, hybrid-composite 8.3 ± 0.7, nano-composite 7.8 ± 1.2, enamel 7.4 ± 0.8) followed by alternating erosion-attrition (ceramic 3.5 ± 0.5, hybrid-composite 2.1 ± 0.8, nano-composite 1.0 ± 0.2, enamel 2.5 ± 0.7) and attrition in mineral solution (ceramic 0.5 ± 0.3, hybrid composite 0.3 ± 0.1, nano composite 0.1 ± 0.2, enamel 0.1 ± 0.1). Ceramic antagonists resulted in significantly higher loss than the remaining antagonistic materials when alternating or simultaneous erosion-attrition was performed. CONCLUSION: Erosive conditions had a massive impact on enamel worn against different antagonistic materials, with simultaneous erosive-attritive conditions being more detrimental than alternating erosive-attritive conditions. CLINICAL RELEVANCE: Enamel wear by antagonistic restorative materials is significantly influenced by erosive conditions.

Attitudes, practice, and experience of German dentists regarding repair restorations.

OBJECTIVES: The aim of the present study was to perform a representative survey among German dentists about attitudes, practice, and experience regarding single-tooth repair restorations. MATERIALS AND METHODS: An anonymous questionnaire was designed and mailed to all registered dentists in Lower Saxony (n = 6600). Twenty-eight percent were returned (n = 1852), and n = 1805 could be analyzed. Statistical analyses were done by Wilcoxon signed-rank tests, Kruskal-Wallis tests, and ordered logistic regressions (p < 0.05). RESULTS: Only 2.2 % of the dentists declared to never perform repair restorations. Composite restorations were repaired significantly more often than all other materials. Frequency of performing repair restorations was partially associated to dentist-related factors. The decision for repairing a restoration was dependent on several tooth- and restoration-associated variables. The main indications for repair were the partial loss of restoration or adjacent tooth structure as well as chipping and endodontic access cavities of crowns. Repair restorations were mostly done with composite using various different preconditioning techniques. Overall patients' acceptance was reported to be high. Most of the dentists considered repair restorations as permanent restoration with a moderate to high longevity. Estimated success of repair restorations depended significantly on the dentists' experiences (frequency and techniques of repair restorations). CONCLUSIONS: Repair restorations were often performed and were well accepted by dentists and patients, but indications for repair restorations as well as applied materials and techniques varied distinctly. CLINICAL RELEVANCE: Repairs of single-tooth restorations are well accepted and frequently performed, but indications, techniques, and materials require further research.

Prevalence and risk factors of erosive tooth wear in 3-6 year old German kindergarten children-A comparison between 2004/05 and 2014/15.

OBJECTIVES: The aims of this study were (1) to investigate prevalence, severity and distribution of erosive tooth wear in German kindergarten children aged 3-6 years in 2014/15 in comparison to an earlier survey from 2004/05 and (2) to identify and compare possible risk factors. METHODS: 775 children aged 3-6 years from 27 kindergartens were examined in 2014/15 and compared to the data from 2004/05 (432 children/21 kindergartens). Erosive tooth wear was examined using the O'Sullivan-Index. Additionally, data were converted into the Basic Erosive Wear Examination (BEWE)-index. Information about dietary habits, chronic illness and oral hygiene practices were obtained by questionnaires. Statistical analyses were done by Chi(2)-, Mann-Whitney U Tests and regression analyses (p<0.05). RESULTS: Compared to 2004/05 (31.3%) prevalence of erosive tooth wear was significantly increased in 2014/15 (45.4%). In 2004/05 and 2014/15, prevalence increased significantly with increasing age of the children: 3-year-olds: 22.5%/14.2%; 4-year-olds: 27.4%/32.9%; 5-year-olds: 30.5%/58.8%; 6-year-olds: 38.1%/71.7%. Children with erosive tooth wear presented more affected teeth and a higher severity of erosive tooth wear, respectively, in 2014/15 compared to 2004/05. The BEWE score sum was significantly higher in 2014/15 (3-year-olds: 3.4±2.1, 4-year-olds: 4.2±3.1, 5-year-olds: 4.6±2.9, 6-year-olds: 5.9±3.3) than in 2004/05 (3-year-olds: 2.0±1.2, 4-year-olds: 2.7±1.8, 5-year-olds: 2.7±2.4, 6-year-olds: 4.2±4.2). In 2014/15, age and male gender were significant with respect to the presence of erosive tooth wear. Severity of erosive tooth wear was dependent on the regular consumption of fruit juices and lemonade/coke. CONCLUSION: The prevalence of erosive tooth wear in German kindergarten children has increased in the last ten years.

Primary canine auto-transplantation: a new surgical technique.

OBJECTIVE: The aim of this study was to investigate whether the growth of soft tissue and bone in children with traumatic tooth loss or agenesis of teeth can be developed reliably, using a new technique of autogenous primary canine transplant. STUDY DESIGN: A total of 10 patients (age range, 7-13 years) were treated either for trauma or for agenesis (n = 14 primary canine transplants). In addition to the clinical examination, patients were subjected to radiologic examinations with regard to root resorption, bone height, and soft tissue level. RESULTS: With an average survival rate of 87%, the average survival time of the transplants using the Kaplan-Meier estimator was 5.2 years. In all cases, soft tissue and bone growth was effectively developed. CONCLUSIONS: Autogenous primary canine transplant is a reliable surgical method for rehabilitating children in the early mixed dentition after traumatic tooth loss, enabling adequate soft tissue and bone growth.