Biaxial flexural strength of 3D-printed 3Y-TZP zirconia using a novel ceramic printer.

OBJECTIVES: To compare the strength and reliability of 3D-printed 3Y-TZP zirconia manufactured with various printing orientations and staining. MATERIALS AND METHODS: A total of one-hundred cylindrical zirconia specimens were designed and fabricated using 3D printing and processed according to ISO 6872 standards. Of these specimens, 80 were 3D printed using the new ZIPRO-D (ZD) 3D ceramic printer. In this ZD group, 60 specimens were printed in a vertical orientation and were either stained after debinding (ZD1, x-orientation, n = 20) or not stained (ZD2, x-orientation, n = 20; ZD3, y-orientation, n = 20) and the remaining 20 specimens out of n = 80 were printed in a horizontal orientation (ZD4). Further 20 specimens out of the entire sample N = 100 were printed vertically with the CeraFab7500 3D ceramic printer (LC). All completed specimens were loaded until fracture using a universal testing machine. Biaxial flexural strengths and Weibull parameters were computed for the ZD groups and for the LC group. Group and sub-group effects were evaluated using Welch ANOVA (alpha = 0.05). RESULTS: The mean (standard deviation, SD) biaxial flexural strengths of vertically oriented ZD samples with (ZD1) and without (ZD2/ZD3) staining were 811 (197) and 850 (152) MPa, respectively (p > 0.05). The ZD4 (horizontally printed), 1107 (144) MPa, and LC (1238 (327)) MPa samples had higher mean (SD) flexural strengths than the ZD1-3 specimens. No difference was observed between the ZD4 and LC group (p > 0.05). Weibull moduli were between m = 4.6 (ZD1) and 9.1 (ZD4) in the ZD group and m = 3.5 in the LC group. CONCLUSIONS: All tested 3D-printed zirconia specimens exceeded the flexural strengths required for class 5 restorations according to ISO 6872 standards. While the flexural strengths of zirconia printed using the novel ZD device in the vertical orientation are lower than those of zirconia printed using the LC printer, the ZD printer shows at least comparable reliability. CLINICAL RELEVANCE: 3D-printing of zirconia is a new technology in dental application. Based on the presented strengths values, clinical application of 3D-printed zirconia for fixed dental protheses can be recommended.

A German version of the Oral Impacts of Daily Performances-reliability and validity.

OBJECTIVE: The Oral Impact of Daily Performances (OIDP) is a dental patient-reported outcome measure (dPROM) for the estimation of oral health-related quality of life (OHRQoL) and takes the frequency as well as the severity of problems into account; however, it is not available in German language. The aim of this study was, therefore, to evaluate the reliability and validity of the German version of the OIDP in patients of a private practice. MATERIAL AND METHODS: Translation of the original OIDP version was performed by a forward-backward process. Reliability was evaluated in terms of construct stability (test-retest) for the single items and the sum scores. The responsiveness to change in oral health status was assessed by pre- and post-treatment comparison, in addition. Validity was assessed as convergent validity in comparison with other dPROMs (OHIP-14; GOHAI) and objective dental findings. RESULTS: A total of 330 patients participated in this study (mean age: 42.0 (18.0)). The OHRQoL of the participants was relatively high (OIDP score 4.3 (SD 14.3), OHIP score 4.8 (SD 5.3), GOHAI score 54.2 (SD 5.4)). A moderate construct stability for the total OIDP-score (ICC 0.686) was found whilst reliability for the single items varied between 0.179 (social contact) to 0.559 (showing teeth). Significant correlations were found for OIDP and OHIP (p < 0.001; r = 0.361) and OIDP and GOHAI (p < 0.001; r = - 0.391) indicating moderate validity with a tendency to even stronger correlations for OIDP-s and OIDP-f (r ≥ 0.500). CONCLUSIONS: The German version of the OIDP demonstrated sufficient reliability and validity. OIDP's general performance should be interpreted cautiously as the outcome was detected in a specifically healthy population. CLINICAL RELEVANCE: The OIDP is yet the only dPROM that evaluates both severity as well as frequency which makes validation interesting regarding specific target populations.

Fracture Resistance of Posterior Tooth-Supported Cantilever Fixed Dental Prostheses of Different Zirconia Generations and Framework Thicknesses: An In Vitro Study.

The rehabilitation of free-end situations is a frequent indication in prosthetic dentistry. Cantilever fixed dental prostheses (cFDPs) made of 1st and 2nd generation zirconia are one treatment option. Due to a unique gradient technology, combinations of different zirconium dioxide generations are thus feasible in one restoration. However, data about these materials are rare. The purpose of this study was therefore to investigate the fracture resistance and fracture modes of tooth-supported cFDPs fabricated from different zirconia materials (gradient technology) and different framework thicknesses. A total of 40 cFDPs were fabricated using the CAD/CAM approach and belonged to five test groups. The different groups differed in the yttria content, the proportion of the tetragonal/cubic phases, or in wall thickness (0.7 mm or 1 mm). After completion, the cFDPs were subjected to thermal cycling and chewing simulation (1.2 × 106 load cycles, 108 N load). Afterwards, cFDPs were statically loaded until fracture in a universal testing machine. A non-parametric ANOVA was compiled to determine the possible effects of group membership on fracture resistance. In addition, post-hoc Tukey tests were used for bivariate comparisons. The mean fracture loads under axial load application ranged from 288 to 577 N. ANOVA detected a significant impact of the used material on the fracture resistances (p < 0.001). Therefore, the use of cFDPs fabricated by gradient technology zirconia may not be unreservedly recommended for clinical use, whereas cFPDs made from 3Y-TZP exhibit fracture resistance above possible masticatory loads in the posterior region.

A new CAD/CAM tooth mobility simulating model for dental in vitro investigations.

OBJECTIVES: To validate a new tooth mobility simulating in vitro model for biomechanical tests of dental appliances and restorations. MATERIAL AND METHODS: Load-deflection curves for teeth in CAD/CAM models (n = 10/group, 6 teeth/model) of the anterior segment of a lower jaw with either low tooth mobility (LM) or high tooth mobility (HM) were recorded with a universal testing device and a Periotest device. All teeth were tested before and after different ageing protocols. Finally, vertical load capacity (Fmax) was tested in all teeth. RESULTS: At F = 100 N load, vertical/horizontal tooth deflections before ageing were 80 ± 10 µm/400 ± 40 µm for LM models and 130 ± 20 µm/610 ± 100 µm for HM models. Periotest values were 1.6 ± 1.4 for LM models and 5.5 ± 1.5 for HM models. These values were within the range of physiological tooth mobility. No visible damage occurred during ageing and simulated ageing had no significant effect on tooth mobility. Fmax values were 494 ± 67 N (LM) and 388 ± 95 N (HM). CONCLUSION: The model is practical, easy to manufacture and can reliably simulate tooth mobility. The model was also validated for long-term testing, so is suitable for investigating various dental appliances and restorations such as retainers, brackets, dental bridges or trauma splints. CLINICAL RELEVANCE: Using this in-vitro model for high standardised investigations of various dental appliances and restorations can protect patients from unnecessary burdens in trials and practice.

The Impact of the SARS-CoV-2 Pandemic on Stress and Anxiety of Dental Students.

OBJECTIVES: To investigate the impact of the severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) pandemic on stress and anxiety of preclinical and clinical dental students. MATERIALS AND METHODS: Dental students (participants) in their clinical course (CC; n = 64) or preclinical course (PCC; n = 53) were included in the study. The subjective perceived levels of stress and anxiety were evaluated using the Dental Environment Stress (DES) questionnaire and the Depression, Anxiety and Stress Scales (DASS) questionnaire. Cortisol levels were measured in saliva samples collected from participants. Knowledge of the pandemic was evaluated using a 100-mm visual analog scale. All data were collected twice: once during the university holidays and once during term time. STATISTICAL ANALYSIS: Results from DES, DASS, and salivary cortisol tests were compared between baseline and follow-up using descriptive and bivariate statistics. Multivariate linear regression models were computed with DES, DASS, and cortisol values as dependent variables to analyze possible influencing factors. RESULTS: Participants showed medium levels of stress and anxiety at baseline and follow-up. The DASS score in the "anxiety" subdomain was significantly higher in the PCC group than in the CC group at baseline (p < 0.001) and increased during term time. DASS scores in the "stress" subdomain also increased during term time. However, both subdomain scores were lower than the cutoff value for a psychological disorder. The mean total DES scores were 615.9 ± 97.7 in the CC group and 580.40 ± 98.9 in the PCC group. These scores indicated medium stress levels and were not significantly different between the groups, nor did they change during the study period. Mean saliva cortisol levels were higher in the CC group (9.2 ± 5.2) than in the PCC group (4.9 ± 2.2) at baseline (p < 0.001) but converged by follow-up. Multivariate regression models showed that intraindividual perception of stress at baseline was consistently the most important aspect for changes in stress and anxiety levels during term time. The SARS-CoV-2 pandemic affected stress and anxiety levels in some participants, but this was not ubiquitous. CONCLUSION: Intraindividual differences in stress perception seem to be more relevant than course affiliation (preclinical or clinical) or the SARS-CoV-2 pandemic to stress and anxiety levels in dental students.

Comparison of six different CAD/CAM retainers vs. the stainless steel twistflex retainer: an in vitro investigation of survival rate and stability.

PURPOSE: To compare failure rates and maximum load capacity (Fmax) of six different computer-aided design/computer-aided manufacturing (CAD/CAM) retainers with those of the hand-bent five-stranded stainless steel twistflex retainer. MATERIALS AND METHODS: Six groups (n = 8 per group) of commercially available CAD/CAM retainers (cobalt-chromium [CoCr], titanium grade 5 [Ti5], nickel-titanium [NiTi], zirconia [ZrO2], polyetheretherketone [PEEK], and gold) and twistflex retainers were tested for long-term sufficiency and for Fmax using a self-developed in vitro model. All retainer models underwent a simulated ageing process of about 15 years (1,200,000 chewing cycles with a force magnitude of 65 N at 45° followed by storage in water at 37 °C for 30 days). If retainers did not debond or break during ageing, their Fmax was determined in a universal testing machine. Data were statistically analysed using Kruskal-Wallis and Mann-Whitney U­tests. RESULTS: Twistflex retainers did not fail (0/8) during ageing and had the highest Fmax (445 N ± 51 N). Ti5 retainers were the only CAD/CAM retainers that also did not fail (0/8) and had similar Fmax values (374 N ± 62 N). All other CAD/CAM retainers had higher failure rates during ageing and significantly lower Fmax values (p < 0.01; ZrO2: 1/8, 168 N ± 52 N; gold: 3/8, 130 N ± 52 N; NiTi: 5/8, 162 N ± 132 N; CoCr: 6/8, 122 N ± 100 N; PEEK: 8/8, 65 ± 0 N). Failure was due to breakage in the NiTi retainers and debonding in all other retainers. CONCLUSION: Twistflex retainers remain the gold standard regarding biomechanical properties and long-term sufficiency. Of the CAD/CAM retainers tested, Ti5 retainers seem to be the most suitable alternative. In contrast, all other CAD/CAM retainers investigated in this study showed high failure rates and had significantly lower Fmax values.

Prevalence of temporomandibular disorders and bruxism in seniors.

BACKGROUND: Information on the prevalence of temporomandibular disorders (TMD) or possible/probable bruxism in seniors is heterogeneous and sparse. OBJECTIVES: To elucidate the prevalence of TMD and possible/probable bruxism in German adults aged 60 years and older. METHODS: Participants of the Interdisciplinary Longitudinal Study of Adult Development and Aging (ILSE) born between 1950-1952 (C1) and 1930-1932 (C2) were examined in 2014-2016 (fourth wave). The participants were surveyed and clinically examined by one calibrated examiner. Two questions of the Patient Health Questionnaire (PHQ) were utilised to evaluate self-reported bruxism. The clinical examination included signs of probable bruxism and the RDC/TMD examination protocol. RESULTS: Data from 191 participants were available. No RDC/TMD diagnosis was made in 83.2%. Of the participants, 15.2% received a single diagnosis and 1.6% multiple diagnoses that included disc displacements (9.4%) and degenerative joint diseases (8.9%). A total of 24.7% reported bruxism that included self-reported awake bruxism in 11.9% and sleep bruxism in 16.2%. Wear was clinically identified in 27.2% of the participants. No sex-related differences were observed. Significant differences were detected for probable bruxism between C1 (14.1%) and C2 (54.3%). CONCLUSION: In the German population aged 60 years and older, the prevalence of TMD is 16.8%. TMD is characterised by temporomandibular joint disorders, including disc displacements and degenerative joint disorders. Bruxism was observed in a quarter of the old population.

Influence of geometric dimensions on early failures of adhesively retained composite resin core build-ups.

OBJECTIVE: To determine the influence of the geometric dimensions of core build-ups on early core build-up failure, that is, loss before definitive prosthesis cementation. MATERIALS AND METHODS: Adhesive core build-ups of exclusively vital teeth in 114 participants were evaluated (n materials: 40 Rebilda DC, 38 Multicore Flow, 36 Clearfil DC Core; n teeth: 8 incisors, 54 premolars, 52 molars). Impressions of the abutment teeth were made (1) after removal of insufficient restorations/caries and (2) after core build-up and preparation for a fixed prosthesis. Digitized model surfaces of both situations were aligned (Geomagic Design X) and core build-up volume (VCBU ), remaining hard tissue volume (VAbut ), and size of the adhesive surface (Aadh ) were assessed. The derived measure dCBU  = VCBU /Aadh can be interpreted as mean arithmetic core build-up thickness. Associations between participant or core build-up design characteristics and the occurrence of early failures were statistically evaluated (SPSS v27, α = 0.05). RESULTS: A total of six (5.3%) core build-up failures were registered. Higher participant age, greater core build-up volume VCBU and greater arithmetic uniform thickness dCBU were associated with a greater incidence of failure in bivariate and univariate, however, not in multivariate statistics. CONCLUSIONS: Core build-up volume and thickness were associated with early success or failure. CLINICAL SIGNIFICANCE: In the case of voluminous/thick core build-ups in relation to the adhesive surface, additional measures, such as the preparation of retentive elements to increase the bonding area, might be considered to reduce the risk of early core build-up failure.

Fit of anterior restorations made of 3D-printed and milled zirconia: An in-vitro study.

OBJECTIVES: To evaluate the fit of zirconia veneers made by either 3D printing or milling. METHODS: A typodont maxillary central incisor was prepared for a 0.5-mm-thick veneer and was reproduced 36 times from resin. Restorations were designed with a 20-µm-wide marginal and a 60-µm-wide internal cement gap, and were made from 3D-printed zirconia (LithaCon 3Y 210, Lithoz, n = 24) and milled zirconia (Cercon ht, DentsplySirona, n = 12). For milled zirconia, a drill compensation was needed to give the milling bur access to the intaglio surface. The restorations were cemented, cross-sectioned, and the cement gap size was analyzed by two raters. Inter-rater reliability was studied at 12 3D-printed veneers (intraclass correlation coefficient, ICC, mixed model, absolute agreement). Twelve remaining 3D-printed restorations were compared with 12 milled restorations regarding fit at three locations: marginally, labially, and at the incisal edge (Mann-Whitney U-tests, α<0.05). RESULTS: Inter-rater reliability was excellent, with an ICC single-measure coefficient of 0.944 (95%-confidence interval: [0.907; 0.966]). Gap sizes (mean ± SD / maximum) were 55 ± 9 / 143 µm at the margins, 68 ± 14 / 130 µm labially, and 78 ± 19 / 176 µm at the incisor edge for 3D-printed veneers. For milled veneers, gap sizes were 44 ± 11 / 141 µm at the margins, 85 ± 19 / 171 µm labially, and 391 ± 26 / 477 µm at the incisor edge. At the margins, the milled veneers outperformed the 3D-printed restorations (p = 0.011). The cement gap at the incisor edge was significantly smaller after 3D printing (p < 0.001). CONCLUSIONS: 3D-printed zirconia restorations showed clinically acceptable mean marginal gaps below 100 µm. Because drill compensation could be omitted with 3D printing, the fit at the sharp incisal edge was significantly tighter than with milling. CLINICAL SIGNIFICANCE: The fit of 3D-printed ceramic anterior restorations meets clinical standards. In addition, 3D printing is associated with a greater geometrical freedom than milling. With regard to fit this feature allows tighter adaptation even after minimally invasive preparation.

Adapting the German version of the dental environment stress questionnaire.

AIMS: To develop a German version of the Dental Environment Stress (DES) questionnaire, and to evaluate its reliability and validity. METHODS: The original English DES questionnaire was translated into German using a forward-backward translation process. To evaluate construct stability, a subgroup of dental students (n = 43) completed the DES twice (interval: 1 week). To evaluate how the DES responds to anticipated changes in stress, all dental students' (n = 64) DES scores and saliva cortisol levels administered from a clinical study were compared between holiday and term time. Furthermore, the Depression, Anxiety and Stress Scale (DASS) and a stress self-assessment were used to determine the validity of the DES. Reliability analyses were calculated using Kendall's tau correlations. To estimate reliability strength, correlation coefficients and intraclass correlations (ICCs) were used. RESULTS: Regarding construct stability, 24 of 25 DES items had at least moderate correlations, and most items showed strong correlations. Correlations for the seven subdomains were good (range: 0.778-1.000). The same was true for the total DES score (ICC: 0.944). Correlations for response to term-time stress were weaker and more varied. Validity analyses revealed fair correlations between the DES and students' self-assessment (Pearson's r = .592) and DASS score (Pearson's r = .392), suggesting satisfactory validity. Stress levels were quite similar between baseline and follow-up. CONCLUSION: The German DES is a reliable tool for evaluating stress in dental students. Because it can be used to identify individual stressors in various categories, it might enable the detection of specific stress situations in educational situations and facilitate solutions (adjustment of curricula, tailored consulting services).

Predictability and outcome of titanium color after different surface modifications and anodic oxidation.

To investigate the predictability and the outcome of surface modification techniques, including anodization. Four surface modification techniques were evaluated in this in-vitro study: sandblasting (S), polishing+anodizing (PA), sandblasting+anodizing (SA), polishing+etching+ anodizing (PEA). Color coordinates L*, a* and b* were collected using a spectroradiometer. Color differences between all groups were quantified by use of ΔE00. A possible influence of group membership was evaluated using 1-way ANOVA. Pair-wise inter-group comparisons were performed using post-hoc Tukey tests. PA specimens were the brightest and showed a pronounced yellowish and reddish hue. S and SA groups were significantly darker and predictability of outcome was higher compared to another groups. The most predictable surface treatment method is sandblasting. Anodizing techniques come along with the brightest and most chromatic color impression of the titanium.

Strength and reliability of zirconia fabricated by additive manufacturing technology.

OBJECTIVES: To test strength and reliability of 3D printed compared to milled zirconia. METHODS: Cylindrical specimens were fabricated from milled (group G1; e.max ZirCAD LT) and from 3D printed (group G2; LithaCon 3Y 230) 3-mol% yttria-stabilized tetragonal zirconia polycrystal (3Y-TZP). While G1 and G2 were sintered in one step, a further series (G3) of 3D printed 3Y-TZP was sintered in two steps including intermediate color infiltration. In each group, two different conditioning strategies were applied (n ≥ 20 samples/subgroup): (1) final polishing with #1200 diamond discs according to ISO 6872, and (2) final polishing with #220 diamond discs resulting in imperfectly polished surfaces. All samples were tested to fracture with a universal testing device (cross-head speed: 1 mm/min). Characteristic strengths and Weibull moduli were calculated. Effects were analyzed by means of either ANOVA (homocedastic data) or Welch ANOVA (heterocedastic data). RESULTS: For samples conditioned according to ISO 6872, mean flexural strengths were 1462 ± 105 MPa (G1), 1369 ± 280 MPa (G2), and 1197 ± 317 MPa (G3). For the imperfectly polished subgroups, strength values were 1461 ± 121 MPa (G1), 1349 ± 332 MPa (G2), and 1271 ± 272 MPa (G3). Although all groups showed high mean strength values, the reliability of milled zirconia (Weibull moduli 14 < m <16) outperformed that of the 3D-printed material (3 < m <6). SIGNIFICANCE: Even after color infiltration in a partially sintered state, the tested 3D printed zirconia exceeded the ISO flexural strength criteria for all types of fixed ceramic restorations by far (800 MPa for class 6, ISO 6872), indicating its high potential for clinical use. Further optimization of the internal material structure after sintering might improve the reliability of 3D printed zirconia which is currently inferior to that of milled zirconia.

Orthodontic shear bond strength and ultimate load tests of CAD/CAM produced artificial teeth.

OBJECTIVES: To investigate whether artificial CAD/CAM processed (computer-aided design/manufacturing) teeth could be a feasible option for the production of dental in vitro models for biomechanical testing. MATERIAL AND METHODS: Disks (n = 10 per group) made from two different CAD/CAM-materials, one fiber-reinforced composite (FRC; Trinia, Bicon) and one polymethylmethacrylate-based resin (PMMA; Telio CAD, Ivoclar Vivadent), as well as bovine teeth (n = 10), were tested for their shear bond strength (SBS) and scored according to the adhesive remnant index (ARI). In addition, CAD/CAM-manufactured lower incisor teeth were tested for their ultimate load (Fu). RESULTS: With regard to SBS, both PMMA (17.4 ± 2.2 MPa) and FRC (18.0 ± 2.4 MPa) disks showed no significant difference (p = 0.968) compared to bovine disks (18.0 ± 5.4 MPa). However, the samples differed with regard to their failure mode (PMMA: ARI 4, delamination failure; FRC: ARI 0 and bovine: ARI 1.6, both adhesive failure). With regard to Fu, FRC-based teeth could withstand significantly higher loads (708 ± 126 N) than PMMA-based teeth (345 ± 109 N) (p < 0.01). CONCLUSION: Unlike PMMA-based teeth, teeth made from FRC showed sufficiently high fracture resistance and comparable SBS. Thus, FRC teeth could be a promising alternative for the production of dental in vitro models for orthodontic testing. CLINICAL RELEVANCE: CAD/CAM-processed teeth made from FRC enable the use of standardized geometry and constant material properties. Using FRC teeth in dental in vitro studies has therefore the potential to identify differences between various treatment options with rather small sample sizes, while remaining close to the clinical situation.

Laboratory and clinical reliability of two spectrophotometers.

OBJECTIVE: To evaluate the repeatability, interexaminer, and interdevice reliability of two clinically applicable spectrophotometers under laboratory and clinical conditions. MATERIAL AND METHODS: For the in vitro part of the study, measurements were performed by the use of Vita Easyshade Advance 4.0 (ES-A) and the Easyshade V (ES-V) at identical positions on different shade tabs (3D-Master; Vita Zahnfabrik, Bad Säckingen, Germany). To test repeatability, one shade tab was measured 50 times by one operator. To determine interrater and interdevice agreement, two operators used both devices to perform 10 measurements on five different shade tabs. Clinical interdevice and interexaminer reliability was checked with a positioning jig used (15 participants). Measurement accuracy of both devices was evaluated for the recommended color of shade tabs. RESULTS: Repeatability of results from both Easyshades was excellent for all color components (maximum deviation between measurements was ≤0.1 units). Interrater agreement was also perfect (intraclass correlation, ICC = 1.000). Interdevice agreement was lower, but still good (ICC ≥ 0.834). In the clinical environment, interrater and interdevice agreements were similar (ICC > 0.964 and ICC > 0.873). Accuracy was satisfactory for both devices, with both observers in full agreement for nearly 80% of ratings. CONCLUSIONS: Both Easyshades produced reliable and accurate measurements and can therefore be recommended for clinical determination of tooth color. CLINICAL SIGNIFICANCE: The outcome of this study might help clinicians estimate the performance of a new digital shade determination device.

In-vitro fit of experimental full-arch restorations made from monolithic zirconia.

PURPOSE: Fabrication inaccuracies can compromise the fit of large-span monolithic zirconia restorations. Sintering distortion is a particular problem. This study aimed to assess the fit of full-arch restorations made from monolithic zirconia for different abutment configurations. METHODS: To quantify fit inaccuracies created during the fabrication of experimental large-span restorations, an in-vitro model with eight abutment teeth was equipped with strain gauges. Ten 14-unit restorations were made from monolithic zirconia and seated on the model in turn. For each of the ten restorations, measurements were taken for three different abutment configurations-polygonal, quadrangular, and unilaterally shortened. Strains exerted during seating were recorded in the anterior-posterior and buccal-palatal directions, and the resulting horizontal forces (rhF) were calculated along with the respective abutment deflection (ad). Data were analyzed using Kruskal-Wallis tests at a significance level of 0.05. RESULTS: All restorations could be seated on the multi-abutment model. The restorations exhibited fabrication misfits, tending to be too wide. Mean rhF/ad were largest for the quadrangular configuration (16.8±2.9 N/0.065 mm) and smallest for the polygonal configuration (13.6±4.5 N/0.053 mm). The largest rhF/ad were measured on abutments of the unilaterally shortened configuration, with a maximum deflection of 0.126 mm. For two of three configurations, rhF/ad were significantly larger for the distal abutments than for the other abutments. CONCLUSION: Even if milling and sintering procedures are optimum, misfit-induced horizontal forces cannot be avoided. Because of the natural tooth mobility, however, the fit of full-arch restorations made from monolithic zirconia might be clinically acceptable.

[Prevalence of temporomandibular disorders in seniors-Symptom-related analyses in younger and older seniors]. / Prävalenz kraniomandibulärer Dysfunktionen bei Senioren ­ symptombezogene Analysen bei jüngeren und älteren Senioren.

BACKGROUND: Temporomandibular disorders (TMD) are common in the general population even in old age. Information on the prevalence of TMD in older people is sparse. OBJECTIVE: To present prevalence values for symptoms and signs of TMD in old people according to the research diagnostic criteria for temporomandibular disorders (RDC/TMD). To compare prevalence values between the age groups of 60-74 years (younger seniors) and ≥ 75 years (older seniors). MATERIAL AND METHODS: Subjects of the interdisciplinary longitudinal study of adult development (ILSE), a representative sample of old people in Germany, were examined between 2014-2016. Subjects of the urban area of Leipzig were chosen to examine symptoms and signs of TMD. RESULTS: The most prevalent symptom was orofacial pain (13.0%) in the aged participants (n = 192). Temporomandibular joint (TMJ) sounds were the most prevalent sign with values up to 35.5%. Gender comparisons revealed higher prevalence values for the symptom headache/migraine as well as for the signs TMJ sounds (especially clicking sounds) and limited mouth opening in females. Regarding age groups, significant differences were only observed for self-reported headache/migraine. CONCLUSION: Orofacial pain was reported by 13.0% of the subjects and TMJ sounds were observed in every third participant. Similar prevalence values for TMD symptoms and signs in younger and older seniors were found.

Early failures when using three different adhesively retained core build-up materials-a randomized controlled trial.

OBJECTIVES: To compare the failure rates for three different adhesively retained core build-up composites up to the incorporation of a permanent fixed dental prosthesis (FDP), and to identify potential failure risk factors. MATERIAL AND METHODS: A randomized controlled trial of 300 participants in need of a core build-up to restore a vital abutment tooth before prosthetic treatment was conducted. Participants were assigned by stratified block randomization to one of three study groups: Rebilda DC (RDC), Clearfil DC Core (CDC), or Multicore Flow (MF). Test teeth were prepared by use of the respective manufacturer's adhesive system. The total-etch technique was used for RDC and MF, and the self-etch technique for CDC. Participants were treated by dentists (n = 150) or dental students (n = 150). Failure rates of core build-ups before incorporation of FDPs were investigated using univariate and multiple logistic regression. RESULTS: The overall failure rate was 8% (n = 23). Rate differences between the three investigated groups did not reach statistical significance (p > 0.05). The mean time between placement of core build-ups and placement of fixed dental prostheses was 12.2 (SD: 14.2) weeks. Conversely, larger cavities (> 3 surfaces) and treatment by dental students were independently associated with an increased failure risk (p < 0.05). CONCLUSIONS: The main risk factors for early failure seem to be the size of the core build-up and clinical experience of the operator, whereas failure rates of core build-up materials combined with a self-etch approach seem to be similar to the rates of materials combined with the total-etch technique. CLINICAL SIGNIFICANCE: This research article should give clinicians an impression of the short-term performance of different adhesively retained core build-ups using different adhesive techniques/materials. Moreover, predominant influencing factors for the success or failure should be pictured.

Association of Dental and Prosthetic Status with Oral Health-Related Quality of Life in Centenarians.

To date, there is little evidence on centenarians' dental and prosthetic status or their oral-health-related quality of life (OHRQoL). Therefore, the aim of this study was to assess possible associations between sociodemographic and oral health factors, including prosthetic needs in this special age group and their potential influence on OHRQoL. Persons born before 1920 were recruited from population registries in south-western Germany. Fifty-five centenarians participated and underwent a comprehensive oral examination. Cognitive capacity was evaluated using the short Mini-Mental State Examination (S-MMSE, max. 21 points). At an S-MMSE > 10, an analysis of OHRQoL by means of the Geriatric Oral Health Assessment Index (max. ADD-GOHAI score 60 points) was performed (n = 43). Bivariate statistics and a linear regression model were used after variable selection to analyze data. Centenarians presented with a mean (SD) of 22 (7.2) missing teeth. Complete (65.5%) or partial dentures (21.8%) in at least one jaw were most common. One-third of the dentures needed repair/replacement; 16% of the centenarians presented with denture sores. In 60% of cases, OHRQoL was rated unsatisfactory (ADD-GOHAI < 57). Trouble biting or chewing resulted in the lowest levels of OHRQoL. Fewer remaining teeth, reduced functional capacity and removable prostheses correlated with an impaired OHRQoL (rs = -0.36, p = 0.01; rs = -0.34, p = 0.01; rs = -0.29, p = 0.03, respectively). After variable selection, the final linear regression model included only the number of missing teeth, the associated ADD-GOHAI score decreasing by 0.3 points per missing tooth. In conclusion, tooth loss and removable prostheses in need of repair or replacement are highly prevalent in centenarians. These factors seem to modulate OHRQoL negatively, assumedly due to impaired chewing function. Larger confirmatory studies are needed to validate these first results.

Mechanical properties of CAD/CAM-fabricated in comparison to conventionally fabricated functional regulator 3 appliances.

Manufacturing of Fränkel's functional regulator 3 (FR3) is complicated and requires extensive knowledge from the dental technician. To determine whether FR3s produced by CAD/CAM techniques (CAD-FR3) meet similar mechanical properties like conventional FR3s (Con-FR3), for each of 10 patient cases, three CAD-FR3 designs (palatal connector cross-section 3 × 3 mm, 4 × 1 mm or 5 × 2 mm) and one Con-FR3 were subjected to cyclic loading and subsequent fracture testing in a universal testing device. Transversal load capacity (Fmax(FR3)) and stiffness were compared among the different CAD-FR3 designs and Con-FR3s using Friedman and Wilcoxon tests with a significance level of α = 0.05. All CAD-FR3 designs had significantly higher mean Fmax(FR3) (p ≤ 0.007) and stiffness (p ≤ 0.005) than the Con-FR3s. The CAD-FR33×3 had the highest mean Fmax(FR3) (98.2 ± 26.2 N) and stiffness (37.1 ± 15.5 N/mm), closely followed by the CAD-FR35×2 (Fmax(FR3): 90.3 ± 24.7 N; stiffness: 30.0 ± 12.3 N/mm). Among the CAD appliances, CAD-FR34×1 had the lowest values (p ≤ 0.007 for all pairwise tests) with Fmax(FR3) of 45.8 ± 17.9 N and stiffness of 12.5 ± 7.3 N/mm. CAD-FR3s have superior mechanical properties in comparison to Con-FR3s if certain design parameters are followed. Further clinical investigations have to examine if they can serve as an alternative in practice.

How Do Changes in Oral Health and Chewing Efficiency Affect the Changes of Oral-Health-Related Quality of Life of Nursing-Home Residents in the Short Term?

OBJECTIVE: To evaluate how changes in oral health and chewing efficiency affect the changes in oral-health-related quality of life (OHRQoL) of nursing-home residents over six months. METHODS: The study was conducted in nine nursing homes. Sociodemographic and general data were collected for all eligible individuals (n = 150). Of these, 114 participants (mean age 82.0 [± 9.5] years, 77.2% women) were available for the following tests at baseline and six months later: a comprehensive examination of dental and general health, a two-colour mixing-ability test (to assess chewing efficiency), the Geriatric Oral Health Assessment Index (GOHAI; to evaluate the OHRQoL), and the Mini Mental State Examination (MMSE; to diagnose the presence and severity of dementia). Univariate and multivariate linear regression models were compiled to analyse possible factors affecting OHRQoL. RESULTS: For the final analysis, 108 participants were available. For the study cohort as a whole, a decrease in the number of functional occluding pairs (C: 0.195; p = 0.034) and an increase in dental-treatment needs (C: -1.968; p = 0.056) had the greatest negative effects on OHRQoL as expressed by the GOHAI score. For denture wearers, a deterioration of denture condition (C: -2.946; p = 0.003) was the most important predictor for a decline in OHRQoL. CONCLUSION: A short-term decline in oral health and function affects the OHRQoL of nursing-home residents. The most important dental variables in this regard are the number of functional occluding pairs and dental and denture-related treatment needs.