Comparison of the accuracy of different types of bite recordings - an in vitro study.

OBJECTIVES: Reconstruction of a three-dimensional jaw position determined by a bite recording is an important aspect of prosthetic therapy. Different materials are used for this purpose. In the dental technical workflow, recordings are used to mount a lower jaw cast in a patient-like spatial position relative to the upper jaw cast. We evaluated the accuracy of positioning under the influence of different jaw positions and materials. MATERIALS AND METHODS: In an experimental setup, comprising an articulator, a pair of metal casts, and an optoelectronic measurement system, the spatial position of the incisal point and two condylar points were measured. To evaluate the accuracy of repeated repositioning of casts in the technical workflow, 324 measurements were taken from 108 recordings, consisting of silicone bite-stops made of addition curing silicone with 95 shore hardness, acrylic wafers, and wax recordings. The recordings were obtained in four jaw relations differing in vertical and protrusive components. RESULTS: Of the three materials/material combinations examined, silicone showed the most consistent results across all measurements, followed by the acrylic wafer system, and then wax recordings. Generally, recordings with smaller gaps between the jaws and no protrusive components showed greater deviations compared to jaw positions with greater protrusion and higher vertical dimensions. CONCLUSIONS AND CLINICAL RELEVANCE: To achieve reliable model mounting with high accuracy, recordings should include the use of a frontal jig and four small recording platelets made of silicone, especially if only a slight elevation of the vertical dimension is needed.

Impact of dental prosthetic treatment and patients' expectations on the seven domains and four-dimensional scale of the Oral Health Impact Profile.

BACKGROUND: Recently, recommendations were given for a new scoring of the Oral Health Impact Profile (OHIP). The original seven domain structure should be replaced by a four-dimensional scale. OBJECTIVES: To investigate the effect of dental prosthetic treatment on the seven domains and the four-dimensional scale of the OHIP-G49/53 questionnaire. METHODS: Seventy four patients were grouped according their pre- and post-treatment situation and the type of treatment they received. Patients completed the OHIP-G49/53 questionnaire before prosthetic treatment (T0), and at 1 week (T1), 3 months (T2) and 6 months (T3) after treatment. Treatment effects on the seven domains and the four dimensions of the OHIP scale were analysed, and the oral health-related quality of life (OHRQoL) was measured. Patients' expectations of their prosthetic treatment were also evaluated. Data were analysed using two-way Mixed ANOVA, regression analysis, and Cronbach's alpha test with a level of significance of α ≤ .017. RESULTS: OHRQoL significantly improved following prosthetic treatment compared with baseline. The largest improvement was found between T0 and T1 evaluations (all p ≤ .001). Unlike the seven-domain scale, the four OHIP dimensions demonstrated further significant improvements across the T1/T2/T3 evaluations (all p ≤ .017). Different pre-treatment findings had different treatment effects on the four OHIP dimensions and seven OHIP domains. Patients' expectations were mainly fulfilled. CONCLUSION: Compared with the seven-domain scale, the four dimensions showed significant follow-up changes, suggesting the four dimensions are suitable for evaluating treatment effects up to 6 months. Clinically meaningful effects of dental prosthetic treatment can be sensitively measured using the four-dimensional OHIP scale.

Influence of oral motor tasks on postural muscle activity during dynamic reactive balance.

BACKGROUND: Jaw clenching improves dynamic reactive balance on an oscillating platform during forward acceleration and is associated with decreased mean sway speed of different body regions. OBJECTIVE: It is suggested that jaw clenching as a concurrent muscle activity facilitates human motor excitability, increasing the neural drive to distal muscles. The underlying mechanism behind this phenomenon was studied based on leg and trunk muscle activity (iEMG) and co-contraction ratio (CCR). METHODS: Forty-eight physically active and healthy adults were assigned to three groups, performing three oral motor tasks (jaw clenching, tongue pressing against the palate or habitual lower jaw position) during a dynamic one-legged stance reactive balance task on an oscillating platform. The iEMG and CCR of posture-relevant muscles and muscle pairs were analysed during platform forward acceleration. RESULTS: Tongue pressing caused an adjustment of co-contraction patterns of distal muscle groups based on changes in biomechanical coupling between the head and trunk during static balancing at the beginning of the experiment. Neither iEMG nor CCR measurement helped detect a general neuromuscular effect of jaw clenching on the dynamic reactive balance. CONCLUSION: The findings might indicate the existence of robust fixed patterns of rapid postural responses during the important initial phases of balance recovery.

Modular training model for education of students in restorative and prosthodontic dentistry.

INTRODUCTION: At the moment, no commercial model solution is available for the individualisation of the dentition depending on the clinical case scenario. Furthermore, the realistic training of most restorative and prosthodontic procedures on a single dental study model is not possible. The aim of this study was the creation of a new training model to fill this gap. MATERIALS AND METHODS: Complete upper and lower jaw models were created based on existing scans and radiological data from a patient. All components for 100 complete models and 1128 teeth for the training were produced with a SLA-printer. Overall, 94 voluntary students attending the first and second preclinical course in prosthodontics tested the functionality of the model with three different tooth types against a standard dental study model and real teeth. After the training, the model was rated in a questionnaire. RESULTS: The production of the models and teeth was feasible. The overall rating of the different teeth was worse for type I (Ø 3.6 ± 1.1), significantly better for type II (Ø 2.5 ± 1.0) and type III (Ø 2.4 ± 1.0) than a standard typodont tooth (Ø 2.7 ± 1.1). The new model was rated significantly better overall (Ø 2.6 ± 1.0) than the standard training model (Ø 3.0 ± 1.1). CONCLUSIONS: The aim of this study was fulfilled. A superior training model was created with equivalent and better tooth types. The new teeth were outstanding in terms of cost-efficiency, appearance and feeling during preparation.

Variability of sleep bruxism-findings from consecutive nights of monitoring.

OBJECTIVES: To determine sleep bruxism (SB) behavior during five consecutive nights and to identify correlations between SB episodes per hour (SB index) and sleep-time masseter-muscle activity (sMMA). MATERIAL AND METHODS: Thirty-one participants were included in the study. Of these, 10 were classified as sleep bruxers (group SB-1) and nine as non-sleep bruxers (group non-SB). The bruxism status of these 19 patients was identified by means of questionnaires, an assessment of clinical symptoms, and electromyographic/electrocardiographic data (Bruxoff® device). The remaining 12 participants were also identified as bruxers, but based exclusively on data from the Bruxoff device (group SB-2). Data analysis included descriptive statistics and Spearman's correlation to assess the relationship between the SB index and sMMA. RESULTS: Participants in group SB-1 showed an overall mean SB index of 3.1 ± 1.6 and a mean total sMMA per night of 62.9 ± 38.3. Participants in group SB-2 had an overall mean SB index of 2.7 ± 1.5 and a mean total sMMA of 56.0 ± 29.3. In the non-SB group, participants showed an overall mean SB index of 0.8 ± 0.5 and a mean total sMMA of 56.8 ± 30.3. Spearman's correlation yielded values of - 0.27 to 0.71 for the correlation between sMMA and SB index. CONCLUSIONS: The data revealed variable SB activity and the absence of a reliable correlation between sMMA and the SB index. CLINICAL RELEVANCE: The high variation in SB activity and lack of correlation between sMMA and the SB index should be considered when diagnosing SB. TRIAL REGISTRATION: Clinical Trials [NIH], clinical trial no. NCT03039985.

Validity of patient self-reports and clinical signs in the assessment of sleep bruxism based on home-recorded electromyographic/electrocardiographic data.

BACKGROUND: Reliable and suitable bruxism assessment would be desirable, but available studies presented heterogeneous results. OBJECTIVE: To determine the agreement of patient self-reports and clinical signs of sleep bruxism (SB) with electromyographic/electrocardiographic data. METHODS: Two hundred individuals from a German dental clinic population (120 women and 80 men) participated in the study. Participants completed different SB questionnaires, had a clinical examination to evaluate bruxism signs and used the Bruxoff® device to record electromyographic/electrocardiographic data for five nights. To investigate interrater reliability for clinical diagnosis of bruxism, 126 of the 200 participants were assessed for clinical signs of bruxism by two independent uncalibrated examiners. Statistical evaluation included calculation of sensitivity, specificity and accuracy and of Cohen's kappa. RESULTS: Based on the Bruxoff® data, 106 participants were identified as bruxers and 94 as non-bruxers. The 106 bruxers were further classified into 47 moderate and 59 intense bruxers. The highest accuracy and sensitivity values were recorded for the overall score for clinical bruxism signs (accuracy: 72.0% and sensitivity: 70.8%). The best specificity (96.8%) was seen for the question regarding tooth grinding in the last two weeks reported by others, but concurrent sensitivity was very low (3.8%). Analysis of interrater reliability revealed a substantial agreement (Cohen's kappa of 0.6). CONCLUSION: The study results indicate that self-report questionnaires and clinical signs have moderate sensitivity, specificity and accuracy for diagnosing bruxism comparing with an ambulatory device for current SB (Bruxoff®). Regarding interrater reliability for clinical signs of SB, substantial agreement was found between the two examiners. CLINICAL TRIAL NO: NCT03039985.

Control of occlusal rehabilitation with 3D-printed crowns.

AIM: With the development of new materials, 3D printing has had an immense impact on dentistry. The latest innovations are the direct manufacturing of temporary and permanent crown and bridge restorations, inlays, onlays, and veneers. In the present case report, 3D-printing technology was used to control and adjust the occlusal rehabilitation with 3D-printed crowns. MATERIALS AND METHODS: A 44-year-old male patient with pathologic dental attrition visited the Department of Restorative Dentistry at the University of Würzburg (Würzburg, Germany). The attrition process was far advanced, and no conventional conservative therapy was indicated. For the rehabilitation of the tooth substance loss, dental height, and appearance, a permanent solution with dental crowns was elected. After the preparation, the restorations were constructed digitally. For the control of the occlusal height, appearance, and color, the restorations were fabricated with a 3D printer and temporarily cemented. The crowns showed a high precision, and only minimal occlusal corrections were needed. After a trial period of 2 weeks and another fine occlusal adjustment, the temporary crowns were removed and scanned. The data were matched to the original construction file, which could be used to optimize the final rehabilitation. The final restorations were made of monolithic zirconia, with only minimal occlusal corrections required. CONCLUSION: At the present time, dentistry is experiencing a great shift toward new and interesting production solutions with 3D-printing technologies. Such technologies give dentists the ability to create more predictable and cost-effective treatments. 3D printing is already being used to create temporary and definitive dental crowns as well as complex treatments, as is shown in the present case report. (Int J Comput Dent 2022;25(3):325-332; doi: 10.3290/j.ijcd.b3380909).

Effect of bone quality and quantity on the primary stability of dental implants in a simulated bicortical placement.

OBJECTIVES: Conventional dental implants inserted in the molar region of the maxilla will reach into the sinus maxillaris when alveolar ridge height is limited. When surgery is performed without prior augmentation of the sinus floor, primary stability of the implant is important for successful osseointegration. This study aimed at identifying the impact of bone quality and quantity at the implantation site on primary implant stability of a simulated bicortical placement. MATERIALS AND METHODS: In our in vitro measurements, bone mineral density, total bone thickness and overall cortical bone thickness were assessed by micro-computed tomography (µCT) of pig scapulae, which resembled well the bicortical situation found in human patients. Dental implants were inserted, and micromotion between bone and implant was measured while loading the implant with an axial torque. RESULTS: The main findings were that primary implant stability did not depend on total bone thickness but tended to increase with either increasing bone mineral density or overall cortical bone thickness. CLINICAL RELEVANCE: Limited bone height in the maxilla is a major problem when planning dental implants. To overcome this problem, several approaches, e.g. external or internal sinus floor elevation, have been established. When planning the insertion of a dental implant an important aspect is the primary stability which can be expected. With other factors, the dimensions of the cortical bone might be relevant in this context. It would, therefore, be helpful to define the minimum thickness of cortical bone required to achieve sufficient primary stability, thus avoiding additional surgical intervention.

Diagnostic accuracy of the Diagnostic Criteria for Temporomandibular Disorders for children aged 8-12 years.

BACKGROUND AND OBJECTIVE: Objective of this study was to determine whether the diagnostic accuracy of the Diagnostic Criteria for Temporomandibular Disorders (DC/TMD) is sufficient for use among schoolchildren aged 8-12 years. METHODS: This prospective cohort study on diagnostic accuracy with calibrated examiners was conducted among 533 children of both sexes aged 8-12 years, with and without TMD symptoms, selected randomly from the Rhein-Neckar district. Self-reporting of non-dental facial pain was used as the reference standard, against which we calculated the following for the pain-related items of the DC/TMD (index test): sensitivity, specificity, positive and negative likelihood ratios, diagnostic odds ratio, accuracy and 95% Wilson Score confidence intervals. We also calculated the area under the receiver-operating characteristic (AUROC) curve displaying sensitivity and specificity. RESULTS: Our final sample consisted of 282 children, half of whom reported having facial pain and 3.2% reported sounds from the temporomandibular joints (TMJs). Despite high specificity (90.78%; 95% confidence interval (CI): [84.86%; 94.53%]), sensitivity of the adapted DC/TMD for pain on maximum jaw opening was poor (37.59%; 95% CI: [30.02%; 45.81%]). For pain on palpation, more similar values were recorded for sensitivity (74.47%; 95% CI: [66.69%; 80.95%]) and specificity (70.21%; 95% CI: [62.21%; 77.14%]). The diagnostic odds ratio was >1 for both examinations. The AUROC for pain on opening was 68.39% (95% CI: [62.62%; 74.16%]), and for pain on palpation, it was 74.63% (95% CI: [69.45%; 79.81%]), whereas the combination of both resulted to an AUROC of 74.09% (95% CI: [68.96%; 79.21%]). It was not possible to measure the diagnostic accuracy of the DC/TMD regarding TMJ sounds or jaw-opening limitations, as they occurred too rarely in our sample. CONCLUSION: In this study, the diagnostic accuracy of the DC/TMD for TMD-related pain in children was lower than that recorded for adults in previous studies.

The "Painting by Numbers Method" for education of students in crown preparation.

INTRODUCTION: No commercially available solution to improve the teaching of a crown preparation directly on typodont teeth exists at the moment. To fill this gap and support the supervisors of dental courses, a printable and inexpensive tooth was created for structured self-assessment. The aim of this study was to test this printable tooth under realistic pre-clinical situations. MATERIALS AND METHODS: A two-coloured, double-layer practice tooth was developed. This tooth was consisting of a layer for a correct preparation and the crown. All printed teeth were produced with a stereolithographic printer. 35 voluntary second-year dental students in the second pre-clinical course in prosthodontics were randomly divided into two groups. All students had experience with typodont teeth and models. The first group was trained on four standard model teeth. The second group used model teeth for the first and fourth attempt and printed teeth for second and third attempt. The preparations of the students were scanned by an in-lab scanner and the surface deviations in contrast to a perfect preparation were measured. The differences between the first and fourth attempt were calculated. Benefits of the printed tooth were also evaluated by a questionnaire using German school grades completed by the students (1 = Excellent, 2 = Good, 3 = Satisfactory, 4 = Adequate, 5 = Poor, 6 = Unsatisfactory). RESULTS: The workflow was feasible and cost-effective regarding the production of the printed teeth. The overall rating of the printed tooth in the questionnaire was good (Ø 2.1 ± 0.22). Students reported different advantages of this method in the free text. The comparison of the preparation between the first and fourth attempt showed that there was a significant better preparation with the printed teeth. The complete preparation had median values of 0.05 mm (Group1: standard model tooth) and -0.03 mm (Group2: printed tooth) (P = .005). Divided into single surfaces, the vestibular and occlusal regions were significantly better. The vestibular surface was 0.11 mm (Group1) and -0.04 mm (Group2) (P = .018). The occlusal surface was 0.13 mm (Group1) and -0.05 mm (Group2) (P = .009). CONCLUSIONS: The aim of this study was fulfilled. The printed tooth was tested successfully in a pre-clinical course. The feasibility of this teaching concept was confirmed by the questionnaire and the analysis of the preparation form. A significant difference to a standard model tooth was measurable. The students had the possibility to learn a correct crown preparation on a standardised two-layered tooth with included preparation. This printed tooth enabled the students to control the crown preparation directly on their own.

3D Printed Teeth with Included Veneer Preparation Guide.

PURPOSE: The purpose of this study was the design, feasibility, and evaluation of a 3D printed tooth model with internal preparation for dental education in veneer preparation. MATERIAL AND METHODS: A tooth with two different colored layers for the crown and the preparation form was designed and printed by a stereolithographic printer. In a voluntary course, 40 third- to fifth-year dental students were trained with these printed teeth in the clinical course. They had the opportunity to prepare four 3D printed teeth with an integrated veneer preparation. During their studies, they used standardized model teeth. The students rated the advantage in a questionnaire according to German school grades (1 best to 6 worst). For reliability analysis, Cronbach's alpha was calculated. Significant differences between groups were calculated using the Mann-Whitney U-test. RESULTS: The production of the teeth was feasible and cost-effective. The overall mean rating of the printed teeth in the questionnaire was 1.8 ± 0.18. The students rated the learning results with the printed tooth as significantly better than the standard model tooth (mean 3.0 ± 0.86 vs. mean 2.1 ± 0.95; p < 0.001). The item "is a more suitable exercise option" in contrast to standard model teeth was evaluated with 1.9 ± 0.61. The item "the included preparation was clearly visible in color" was rated with 1.7 ± 0.71. "The tooth model illustrated visually an ideal preparation" was rated with 1.8 ± 0.65. Additionally, the students were interested in including more printed teeth into their studies (1.7 ± 0.86). In the open questions the students reported great benefits of this method. CONCLUSIONS: The feasibility of this teaching concept was confirmed. The students favored working on the innovative 3D-teeth with internal veneer preparation, emphasizing the usefulness of this technique in dental education. The tooth enabled the students to control their preparation permanently on their own.

Comparison of acupuncture on specific and non-specific points for the treatment of painful temporomandibular disorders: A randomised controlled trial.

BACKGROUND AND OBJECTIVE: The aim of this single-centre, two-arm, parallel-group, double-blinded, randomised controlled trial was to investigate the disputed specific effectiveness of acupuncture by comparing acupuncture on specific and non-specific points among patients with non-chronic, painful TMDs. METHODS: Following predefined eligibility criteria, 49 consecutive patients of both sexes were recruited to the study. All subjects were diagnosed with a non-chronic (Graded Chronic Pain Scale grade <3) painful TMD, as assessed using the Diagnostic Criteria for Temporomandibular Disorders (DC/TMD). Patients were randomly assigned to group A (acupuncture on specific points) or group B (acupuncture on non-specific points) after the initial examination (T0). Both acupuncture treatment sessions were conducted by a trained dentist once a week for four weeks. The examination was repeated five weeks (T5) after T0 by one calibrated examiner who was unaware of the study groups. Characteristic pain intensity (CPI) was evaluated as the main outcome criterion and compared between times and treatment groups by means of non-parametric tests (significance level set at P = .05). Secondary outcomes comprised the maximum corrected active mouth-opening without pain (MAO); patients' expectations regarding acupuncture treatment and pain development; depressivity; and oral health-related quality of life (OHRQoL). RESULTS: A total of 41 patients (38 female) successfully completed the study (mean age: 40.17 ± 16.61). The two groups did not differ significantly at any time in terms of age and CPI. However, CPI was significantly (P < .05) lower at T5 than at T0 for both groups (29.66 and 30.35% lower in group A and group B, respectively). An increase in MAO was observed at T5 for both groups but was significant for group B only (P = .016). All patients had positive expectations of acupuncture therapy, and the two groups did not differ significantly at T5 with regard to the extent to which their expectations had been fulfilled by the treatment (P = .717). Comparison of T0 and T5 showed a statistically significant reduction of depressivity for group A (P = .0205), but no significant change for group B (P = .329). At T5, OHRQoL had improved significantly for both groups (group A, P = .018; group B, P < .001) compared with at T0. CONCLUSIONS: Acupuncture on both specific and non-specific points reduces the non-dysfunctional pain of TMD patients. The effect of acupuncture on painful TMD cannot be attributed to the specific point selection.

Occlusal dysesthesia-A clinical guideline.

BACKGROUND: The diagnosis and management of patients suffering from occlusal dysesthesia (OD) remain a major challenge for dental practitioners and affected patients. OBJECTIVES: To present the results of a literature-based expert consensus intended to promote better understanding of OD and to facilitate the identification and management of affected patients. METHODS: In 2018, electronic literature searches were carried out in PubMed, Cochrane Library and Google Scholar as well as in the archives of relevant journals not listed in these databases. This approach was complemented by a careful assessment of the reference lists of the identified relevant papers. The articles were weighted by evidence level, followed by an evaluation of their contents and a discussion. The result represents an expert consensus. RESULTS: Based on the contents of the 77 articles identified in the search, the current knowledge about clinical characteristics, epidemiology, aetiology, diagnostic process, differential diagnosis and management of OD is summarised. CONCLUSIONS: Occlusal dysesthesia exists independently of the occlusion. Instead, it is the result of maladaptive signal processing. The focus should be on patient education, counselling, defocusing, cognitive behavioural therapy, supportive drug therapy and certain non-specific measures. Irreversible, specifically an exclusively dental treatment approach must be avoided.

Introduction of a new teaching concept for crown preparation with 3D printed teeth.

INTRODUCTION: For both students and teachers, it is challenging to learn and teach a correct crown preparation. The purpose of this study was the design, feasibility and evaluation of a 3D printed tooth model with internal preparation for dental education in crown preparation and to analyse the quality of the prepared printed teeth in comparison with prepared standard model teeth. MATERIALS AND METHODS: A printable tooth was designed and printed by a stereolithographic printer. 38 fourth-year dental students in the first clinical course in prosthodontics were trained in a voluntary course using printed teeth. Different aspects of the printed tooth were evaluated by a questionnaire using German school grades (1 best to 5 worst). The quality of the preparation with the printed teeth and standard training teeth was also rated in an evaluation form done by an expert group consisting of five experienced dentists. RESULTS: The workflow was feasible and cost-effective for the production of the teeth. The overall rating of the printed tooth was Ø 2.0 ± 0.34 in the questionnaire completed by the students. The students rated the printed tooth model (Ø 2.1 ± 0.85) as significantly better than the standard model tooth (Ø 3.3 ± 0.77; P = .000). The students reported great benefits in the use of this model tooth, for example valuable replacement of a standard model and real teeth, direct control of material loss. The quality of the preparation was evaluated by the expert group as significantly better with an overall mean grade of Ø 2.6 ± 0.37 for the printed teeth compared to Ø 2.9 ± 0.42 for the standard model teeth (P = .000). CONCLUSIONS: The feasibility of this teaching concept was confirmed. The students favoured to work on the innovative 3D-teeth with internal preparation, emphasising the usefulness of this technique in dental education. The expert group confirmed also the significant training effect of this tooth model in contrast to a standard model tooth.

Introduction of a new teaching concept for dentin post preparation with 3D printed teeth.

INTRODUCTION: The preparation for dentin posts is difficult and hard to learn. There are currently no reproducible simulation models to train this clinical procedure. The purpose of this study was the design, feasibility and evaluation of a three-dimensional (3D) printed tooth model for the pre-clinical teaching of students. MATERIALS AND METHODS: A printable tooth was designed and printed by a stereolithographic printer. A total of 48 fourth-year dental students in the first clinical course in prosthodontics were trained in a voluntary hands-on course on 4 similar printed teeth. The students used standard model teeth and real-teeth models during their education. They had experience in caries removement and root canal treatment on real patients. Root perforations were counted for every attempt. The different benefits of the 3D printed tooth were evaluated by a questionnaire using German school grades from 1 (best) to 6 (worst). RESULTS: The overall rating of the printed tooth was Ø1.9 ± 0.3. The item "suitable exercise option" was rated Ø2.0 ± 0.8, and the teeth were "easy to use" Ø1.9 ± 0.9. The item "realistic approach to dentin post preparation" was rated Ø2.1 ± 0.8, and the teeth showed the "shortcomings at a root perforation" Ø1.5 ± 0.6. The students reported to have much more motivation and enthusiasm to improve their skills with the printed teeth Ø2.1 ± 0.9. They had a strong desire to include these teeth in their pre-clinical education before the first patient treatment Ø1.6 ± 0.8. The success rate of the dentin post preparation was significantly better for the second 25% (P = .047) and fourth 48% (P = .04) attempt. CONCLUSIONS: The feasibility of this teaching concept was confirmed. The students had the possibility to learn a correct dentin post preparation on a printed tooth model. The learning effect with this tooth model was rated as good to very good by the questionnaire.

[Design and quality control of the oral health status examination in the German National Cohort (GNC)]. / Design und Qualitätskontrolle der zahnmedizinischen Untersuchung in der NAKO Gesundheitsstudie.

BACKGROUND: Caries and periodontitis are highly prevalent worldwide. Because detailed data on these oral diseases were collected within the framework of the German National Cohort (GNC), associations between oral and systemic diseases and conditions can be investigated. OBJECTIVES: The study protocol for the oral examination was designed to ensure a comprehensive collection of dental findings by trained non-dental staff within a limited examination time. At the mid-term of the GNC baseline examination, a first quality evaluation was performed to check the plausibility of results and to propose measures to improve the data quality. MATERIALS AND METHODS: A dental interview, saliva sampling and oral diagnostics were conducted. As part of the level­1 examination, the number of teeth and prostheses were recorded. As part of the level­2 examination, detailed periodontal, cariological and functional aspects were examined. All examinations were conducted by trained non-dental personnel. Parameters were checked for plausibility and variable distributions were descriptively analysed. RESULTS: Analyses included data of 57,967 interview participants, 56,913 level­1 participants and 6295 level­2 participants. Percentages of missing values for individual clinical parameters assessed in level 1 and level 2 ranged between 0.02 and 3.9%. Results showed a plausible distribution of the data; rarely, implausible values were observed, e.g. for measurements of horizontal and vertical overbite (overjet and overbite). Intra-class correlation coefficients indicated differences in individual parameters between regional clusters, study centres and across different examiners. CONCLUSIONS: The results confirm the feasibility of the study protocol by non-dental personnel and its successful integration into the GNC's overall assessment program. However, rigorous dental support of the study centres is required for quality management.

The flexural strength of CAD/CAM polymer crowns and the effect of artificial ageing on the fracture resistance of CAD/CAM polymer and ceramic single crowns.

OBJECTIVES: The purpose of this study was to investigate the fracture resistance, flexural strength and Weibull modulus of an innovative CAD/CAM polymer and to compare its fracture resistance with that of glass ceramics. MATERIALS AND METHODS: A total of 32 (n = 16 IPS e.max CAD (LIDI); n = 16 LuxaCam Composite (LUXA)) first mandibular molar crowns were fabricated and cemented onto metal dies by use of luting composite. Half of the specimens were loaded until fracture without prior artificial ageing. The other half were subjected to thermal (5°/55 °C) and mechanical (1,200,000 cycles, 80 N) cycling before fracture loading. Scanning electron microscopy was used to analyse fracture behaviour. A three-point bending test of the flexural strength of LUXA was performed according to ISO 6872:2008. Data were analysed by means of the Kolmogorov-Smirnov test, Mann-Whitney U-test (p < 0.05) and Weibull statistical analysis. RESULTS: Initial fracture resistance of LIDI was significantly higher than that of LUXA. However, the initial fracture resistance of LIDI decreased significantly after artificial ageing. After ageing, fracture resistance was 1050.29 ± 325.08 N for LUXA and 1250.09 ± 32.53 N for LIDI. Three-point bending test yielded a mean flexural strength value for LUXA of 145.28 ± 18.21 MPa and a Weibull modulus of m = 9.51. CONCLUSIONS: Polymer-based material tested in this study had a lower fracture resistance than that of the glass-ceramic material. Fracture resistance and flexural strength of LuxaCam Composite are sufficient for use in the first molar region. CLINICAL RELEVANCE: The mechanical properties of this innovative polymer-based material indicate it can be used in the first molar region as a suitable alternative to glass ceramics. Further clinical studies are required to confirm this. The study presents an innovative material as an alternative to glassceramic for the clinical use in dentistry. The materials investigated were differently affected by artificial aging. Clinical use for patients with bruxism may be considered.

Chronic stress and temporalis muscle activity in TMD patients and controls during sleep: a pilot study in females.

OBJECTIVES: The aim of this study was to assess the correlation between chronic stress and temporalis muscle activity during four nights. MATERIAL AND METHODS: Forty-four female subjects were recruited in five dental practices located in different areas of the federal state of Saarland, Germany (dental practice network in Saarland). The following inclusion criteria were used: female, aged between 18 and 65, no somatization or depression, and no pain medication, graded chronic pain status < 3. Both subjects reporting about sleep bruxism and subjects negating sleep bruxism during anamnesis were included. Anamnestic issues, sleep bruxism, anxiety, and chronic stress were assessed using validated questionnaires. Temporalis muscle activity was measured for four nights using a portable electromyographic device. Correlation coefficient was used to assess the correlation (Spearman-correlation) between chronic stress and number of temporalis muscle episodes/hour and between anxiety and the number of episodes/hour. RESULTS: The analysis showed that the factors "work overload" (adulthood chronic stress because of too many demands at work) and "pressure to perform" (necessity to be successful at work) were significantly correlated with the number of temporalis muscle episodes per hour. In contrast, anxiety was not correlated with temporalis muscle episodes per hour. CONCLUSIONS: Work-related chronic stress seems to be associated with an increased level of temporalis muscle activity during sleep. CLINICAL RELEVANCE: During anamnesis, work-related aspects should be assessed in females presenting with sleep-bruxism.

Postendodontic Restoration: Endodontic Post-and-Core or No Post At All?

PURPOSE: The objective of this systematic review was to assess the impact of endodontic post insertion on the clinical performance of endodontically treated teeth (ETT). MATERIALS AND METHODS: A specific PICO question was developed and a Medline search was performed in January 2017 using relevant terms in order to identify studies comparing the success/survival of dental restorations using endodontic posts or no posts. Additionally, the electronic databases "Opengrey", "BBO", "LILAC" and "IBECS" were assessed and a hand search of cross references from original articles and reviews was performed. The methodological quality of the included studies was assessed independently by three referees using (1) the critical appraisal skills program (CASP) and (2) Cochrane checklist (version 5.1.0). RESULTS: A total of 14 studies were included, among them 11 randomized controlled trials (RCT), two prospective clinical trials, and one retrospective clinical trial. The overall quality of the studies was good according to the CASP. However, the Cochrane rating showed that in seven studies, the risk of bias was high in > 40% of the items, indicating a relevant level of methodological flaws. Three studies showed a low risk of bias in > 80% of the items. The majority (10 out of 14) of the clinical studies included failed to show a positive effect of post placement. A post effect is possible when no cavity wall is present. CONCLUSION: There is no unequivocal clinical evidence to support or reject the use of posts even for no-wall cavities, either for direct or indirect restorations.

Fracture behavior of all-ceramic, implant-supported, and tooth-implant-supported fixed dental prostheses.

OBJECTIVES: In vitro investigation of the effects of fixed dental prosthesis (FDP) support and loading conditions on the fracture behavior of all-ceramic, zirconia-based FDP veneered with computer-aided design/computer-aided manufacturing (CAD/CAM)-manufactured lithium disilicate ceramic. MATERIALS AND METHODS: Based on a model for a 3-unit FDP in the molar region (tooth in region 15, implant in region 17), 16 identical zirconia frameworks were fabricated and veneered with milled lithium disilicate ceramic. Another 16 FDPs were manufactured similarly, using a model in which the tooth was replaced by an implant. The specimens underwent 10,000 thermal cycles between 6.5 and 60 °C and 1,200,000 chewing cycles with a force magnitude of 100 N. All were then subsequently loaded until fracture in a universal testing device. Half of the FDPs were subjected to centric and axial loading on the pontic, the others to eccentric and oblique loading on one cusp of the pontic. RESULTS: No failures were observed after artificial aging. Fracture loads of tooth-implant-supported restorations were 1636 ± 158 and 1086 ± 156 N for axial and oblique loading, respectively; implant-supported FDPs fractured at 1789 ± 202 and 1200 ± 68 N, respectively. Differences were significant for load application (P < 0.001) and support type (P = 0.020). For the two types of load application, fracture mode differed substantially: complete fracture was observed for centric and axial loading whereas mixed cohesive/adhesive failure was observed for many FDPs loaded eccentrically and obliquely. CONCLUSIONS: The high incidence of chipping of manually veneered implant-supported all-ceramics restorations might be reduced by use of CAD/CAM-manufactured lithium disilicate veneers. CLINICAL RELEVANCE: FDPs veneered with lithium disilicate resist occlusal forces of 500 N, irrespective of load application and support type. The fracture resistance of implant-supported FDPs was, however, higher than that of combined tooth-implant-supported FDPs. Their clinical use seems to be justified.