Bond Strength of Milled and Printed Zirconia to 10-Methacryloyloxydecyl Dihydrogen Phosphate (10-MDP) Resin Cement as a Function of Ceramic Conditioning, Disinfection and Ageing.

This study aimed to assess the suitability of printed zirconia (ZrO2) for adhesive cementation compared to milled ZrO2. Surface conditioning protocols and disinfection effects on bond strength were also investigated. ZrO2 discs (n = 14/group) underwent either alumina (Al2O3) airborne particle abrasion (APA; 50 µm, 0.10 MPa) or tribochemical silicatisation (TSC; 110 µm Al2O3, 0.28 MPa and 110 µm silica-modified Al2O3, 0.28 MPa), followed by disinfection (1 min immersion in 70% isopropanol, 15 s water spray, 10 s drying with oil-free air) for half of the discs. A resin cement containing 10-methacryloyloxydecyl dihydrogen phosphate (10-MDP) was used for bonding (for TSC specimens after application of a primer containing silane and 10-MDP). Tensile bond strength was measured after storage for 24 h at 100% relative humidity or after 30 days in water, including 7500 thermocycles. Surface conditioning significantly affected bond strength, with higher values for TSC specimens. Ageing and the interaction of conditioning, disinfection and ageing also impacted bond strength. Disinfection combined with APA mitigated ageing-related bond strength decrease but exacerbated it for TSC specimens. Despite these effects, high bond strengths were maintained even after disinfection and ageing. Adhesive cementation of printed ZrO2 restorations exhibited comparable bond strengths to milled ZrO2, highlighting its feasibility in clinical applications.

Oral Health Status of Healthcare Workers in Ilembula/Tanzania during the COVID-19 Condition.

The challenge of reduced dental treatment and education infrastructure in the Tanzanian highlands affects the oral health situation of both the general population and local healthcare workers. The aim of this study was to investigate the oral health status of healthcare workers at Ilembula Lutheran Hospital (ILH), Tanzania, during the COVID-19 pandemic. In total, 134 healthcare workers (62 women, 72 men; mean age 36.48 ± 9.56 years, range 19-59 years; median age 35.00 years) participated in this cross-sectional study, conducted from 12 February to 27 February. A dental examiner trained in oral health screening performed the oral health data collection. Data collection was performed by probability sampling using the Ilembula Data Collection Form-Oral Health (IDCF-Oral Health) questionnaire distributed in paper form. Ethical approval was obtained from the National Institute for Medical Research/Tanzania. The decayed, missing, and filled teeth (DMF/T) index proposed by the World Health Organization (WHO) was used with the associated caries measurement method and the simplified oral hygiene index (OHI-S). Details regarding edentulism, nutritional habits, and socio-economic factors were collected. Statistical analysis was performed using linear regression (α = 0.05). The average DMF-T index was 3.33 ± 0.82, with age, gender, meal frequency, and soft drink consumption significantly influencing the index. No evidence of dental plaque was detected in 43.3% of the participants. Of the participants, 32.8% required prosthetic treatment (Kennedy Class III), while 16.4% needed it for acute malocclusions. Oral hygiene products were used in 97% of cases. A total of 35.8% of the participants had an OHI-S score of up to 1.0, with (p < 0.001) age and (p < 0.001) sex having a significant influence on the index. The current oral health situation of healthcare workers at ILH shows a moderate need for restorative and prosthetic treatment in rural Tanzania. Despite the COVID-19 pandemic, there was no change in the need for dental treatment, which may be explained by the generally restricted access to dental healthcare in the investigated region. The development of an interdisciplinary oral health prophylaxis system could help to reduce the need for future treatments.

Metal-Ceramic Resin-Bonded Fixed Partial Dentures After a Mean Observation Time of 7.5 Years.

PURPOSE: To generate data on the long-term survival of metal-ceramic resin-bonded fixed partial dentures (RBFPDs). MATERIALS AND METHODS: A total of 89 patients received 94 RBFPDs, 5 of whom (women n = 1; men n = 4) received 2 RBFPDs each. All RBFPDs were fabricated as two-retainer end-abutment metal-ceramic restorations. Clinical follow-ups were performed 6 months after cementation and then annually thereafter. The mean observation time was 7.5 years. Cox regression was performed to test the effects of the variables: gender, location, arch, design, use of rubber dam, and adhesive luting system. Survival and success were calculated using Kaplan-Meier curves. As a secondary objective, patient and dentist satisfaction with the esthetics and function of the RBFPDs was evaluated. The significance level was set at α = .05 for all calculations. RESULTS: Estimated Kaplan-Meier failure-free survival was 97.5% (standard error [SE] 1.7) after 5 years and 83.3% (SE 5.3) after 10 years. Calculated intervention-free survival (success) was 90.1% (SE 3.4) after 5 years and 65.5% (SE 6.7) after 10 years. Debonding-free survival was 92.6% (SE 2.9) after 5 years and 80.6% (SE 5.4) after 10 years. Cox regression revealed that none of the four tested variables had a significant effect on the incidence of complications in RBFPDs. Patient and dentist satisfaction with RBFPD esthetics and function was consistently high throughout the observation period. CONCLUSIONS: Within the limitations of an observational study, RBFPDs achieved clinically successful outcomes over a mean observational period of 7.5 years.

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.

Initial damage and failure load of zirconia-ceramic and metal-ceramic posterior cantilever fixed partial dentures.

OBJECTIVES: The aim of this study was to compare failure load and initial damage in monolithic, partially veneered, and completely veneered (translucent) zirconia cantilevered fixed partial dentures (CFPDs), as well as completely veneered metal-ceramic CFPDs under different support and loading configurations. MATERIALS AND METHODS: Eight test groups with anatomically congruent CFPDs (n = 8/group) were fabricated, differing in CFPD material/support structure/loading direction (load applied via steel ball (Ø 6 mm) 3 mm from the distal end of the pontic for axial loading with a 2-point contact on the inner cusp ridges of the buccal and oral cusps and 1.3 mm below the oral cusp tip for 30° oblique loading): (1) monolithic zirconia/CoCr abutment teeth/axial, (2) monolithic zirconia/CoCr abutment teeth/oblique, (3) partially veneered zirconia/CoCr abutment teeth/axial, (4) partially veneered zirconia/CoCr abutment teeth/oblique, (5) completely veneered zirconia/CoCr abutment teeth/axial, (6) completely veneered CoCr/CoCr abutment teeth/axial (control group), (7) partially veneered zirconia/implants/axial, and (8) partially veneered zirconia/natural teeth/axial. Restorations were artificially aged before failure testing. Statistical analysis was conducted using one-way ANOVA and Tukey post hoc tests. RESULTS: Mean failure loads ranged from 392 N (group 8) to 1181 N (group 1). Axially loaded monolithic zirconia CFPDs (group 1) and controls (group 6) showed significantly higher failure loads. Oblique loading significantly reduced failure loads for monolithic zirconia CFPDs (group 2). Initial damage was observed in all groups except monolithic zirconia groups, and fractography revealed design flaws (sharp edges at the occlusal boundary of the veneering window) in partially veneered zirconia CFPDs. CONCLUSIONS: Monolithic zirconia CFPDs might be a viable alternative to completely veneered CoCr CFPDs in terms of fracture load. However, oblique loading of monolithic zirconia CFPDs should be avoided in clinical scenarios. Design improvements are required for partially veneered zirconia CFPDs to enhance their load-bearing capacity. CLINICAL RELEVANCE: Monolithic zirconia may represent a viable all-ceramic alternative to the established metal-ceramic option for CFPD fabrication. However, in daily clinical practice, careful occlusal adjustment and regular monitoring should ensure that oblique loading of the cantilever is avoided.

The Effect of Titanium Anodization on the Bond Strength of 10-methacryloyloxydecyl dihydrogen phosphate (10-MDP) Resin Cement.

PURPOSE: To examine the effects of anodization and different surface modifications of titanium on bond strength to 10-methacryloyloxydecyl dihydrogen phosphate (10-MDP) resin cement. MATERIALS AND METHODS: Grade 5 titanium alloy disks (n = 160) were assigned to one of five prebonding surface treatment study groups (polished; polished and anodized; polished, etched, and anodized; sandblasted; sandblasted and anodized). Disks were adhesively bonded with 10-MDP resin cement (Panavia 21; bonding area: 3.3 mm in diameter) to composite resin cylinders. In each study group, tensile bond strength tests were conducted after 24 ± 1 hours and after 6 months (180 ± 2 days) of water storage (n = 16 specimens per water storage subgroup). Debonded specimens were stereomicroscopically analyzed to determine their fracture mode. Statistics included one-way and multifactorial ANOVA and Tukey post hoc tests (α = .05). RESULTS: Anodization and water storage did not significantly (P ≥ .389) affect tensile bond strength. Although subgroups of polished samples had significantly (P ≤ .031) lower bond strengths (subgroup mean values: 20 to 26 MPa) than etched or sandblasted samples (subgroup mean values: 29 to 33 MPa), they nonetheless exceeded the empirical threshold of 10 MPa used as a criterion for clinical recommendation. The fracture mode of all test specimens was predominantly cohesive. CONCLUSIONS: Anodization of titanium surfaces can be performed without weakening the adhesion of 10-MDP-based resin cement to titanium.

Cumulative 10-year performance of endodontically treated teeth with prosthetic restorations of base metal alloy double crowns with friction pins-a retrospective study.

OBJECTIVES: This 120-month follow-up study aimed to investigate the complication rate of abutment teeth after endodontic pretreatment with base metal alloy double crowns with friction pins. MATERIALS AND METHODS: A total of 158 participants (n = 71, 44.9% women) aged 62.5 ± 12.7 years with 182 prostheses on 520 abutment teeth (n = 459, 88.3% vital) were retrospectively analyzed between 2006 and 2022. Of the endodontically treated abutment teeth, 6.9% (n = 36) were additionally treated with post and core reconstructions. Cumulative complication rates were calculated using the Kaplan-Meier estimator and log-rank test. In addition, Cox regression analysis was performed. RESULTS: The cumulative complication rate at 120 months for the entire set of abutment teeth was 39.6% (confidence interval [CI]: 33.0-46.2). Endodontically treated abutment teeth (33.8%; CI: 19.6-48.0) were found to have a significantly higher cumulative fracture rate than vital teeth (19.9%; CI: 13.9-25.9, p < 0.001). Endodontically treated teeth restored with post and core reconstructions (30.4%; CI: 13.2-47.6) showed a nonsignificant lower cumulative fracture rate than that of teeth with root fillings only (41.6%; CI: 16.4-66.8, p = 0.463). CONCLUSIONS: Higher 120-month cumulative fracture rates were observed in endodontically treated teeth. Comparable performance was observed in teeth with post and core reconstructions compared to teeth with root fillings only. CLINICAL RELEVANCE: If endodontically treated teeth are used as abutments for double crowns, the risk of complications from these teeth should be considered when planning treatment and communicating with the patient.

Metal-ceramic resin-bonded fixed partical dentures after a mean observation time of 7.5 years.

PURPOSE: The aim of the present study was to generate data on the long-term survival of metal-ceramic resin-bonded fixed partial dentures. MATERIAL AND METHODS: Eighty-nine participants, received 94 RBFPDs, 5 (n women = 1; n men = 4) received 2 RBFPDs each. All RBFPDs were fabricated as two-retainer end-abutment metal-ceramic restorations. Clinical follow-ups were performed 6 weeks after cementation and annually thereafter. The mean observation time was 7.5 years. Cox regression was performed to test the effects of the variables sex, location, jaw, design, use of rubber dam, and adhesive luting system Survival and success were calculated by using Kaplan-Meier curves. As a secondary objective, patient and dentist satisfaction with the esthetics and function of the RBFPDs was evaluated. The significance level was set at α = .05 for all calculations. RESULTS: Estimated Kaplan-Meier failure-free survival was 97.5% (standard error [SE] 1.7) after 5 years and 83.3% (SE 5.3) after 10 years. Calculated intervention-free survival (success) was 90.1% (SE 3.4) after 5 years and 65.5% (SE 6.7) after 10 years. Debonding-free survival was 92.6% (SE 2.9) after 5 years and 80.6% (SE 5.4) after 10 years. Cox regression revealed none of the four tested variables had a significant effect on the incidence of complications in RBFPDs. Patient and dentist satisfaction with RBFPD esthetics and function was consistently high throughout the observation period. CONCLUSIONS: Within the limitations of an observational study, RBFPDs achieved clinically successful outcomes over a mean observational period of 7.5 years.

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.

Ten-year clinical performance of non-precious metal double crowns with friction pins in severely reduced dentitions-a retrospective study.

OBJECTIVES: This follow-up study aimed at collecting long-term data for removable partial dentures (RPDs) retained by double crowns with spark-eroded friction pins (DCP) and comparing them in the presence of severely reduced dentition (SRD) and non-SRD (NSRD, i.e. residual dentition with more than three abutment teeth) after a 10-year wearing period. MATERIALS AND METHODS: A total of 158 participants (n = 71, 44.9% women) aged 62.5 ± 12.7 years with 182 prostheses on 520 abutment teeth were followed up between 2006 and 2022. The SRD group included 144 RPDs supported by 314 abutment teeth. The data collection was performed retrospectively. 10-year survival rates of RPDs and abutment teeth were determined using the Kaplan-Meier method and compared using the log-rank test for SRD and NSRD, among others. Cox regression analyses were conducted to isolate risk factors for the survival of both RPDs and abutment teeth. RESULTS: The 10-year cumulative survival rate of all abutment teeth was 65.6% with significantly lower values in the SRD group (53.5%) (p < 0.001). The survival rate for all RPDs was 65.5%. The SRD group showed lower survival rates (57.9%) (p = 0.004). The number and location of the abutment teeth had a significant influence on the survival rates of the RPDs and the abutment teeth. Age, sex, jaw, relining, and vitality had a significant influence on the abutment teeth survival rates. CONCLUSIONS: RPDs showed an acceptable clinical survival rate after 10 years. The number, location, and vitality of abutment teeth were factors that influenced the survival of both RPDs and abutment teeth. CLINICAL RELEVANCE: Consideration of the influencing factors found can help improve the prognostic assessment of double crown-retained dentures in the context of prosthetic therapy planning.

Up to 10 years clinical performance of zirconia ceramic and metal-ceramic fixed partial dentures: A retrospective study.

STATEMENT OF PROBLEM: Completely veneered zirconia ceramic (ZC) fixed partial dentures (FPDs) have been reported to have a higher incidence of ceramic chipping than the standard metal-ceramic FPDs. However, data from comparative long-term studies are sparse. PURPOSE: The purpose of this retrospective study was to compare the long-term survival, chipping-free survival, and success of ceramic-veneered high noble metal alloy (HN), base metal alloy (cobalt-chromium alloy) (CC), and ZC FPDs and to isolate risk factors for the incidence of failure, veneer chipping, and overall complications. MATERIAL AND METHODS: Data from 289 study participants (58.7% women; mean age, 57.97 ±11.51 years) provided with a total of 400 FPDs comprising 197 (49.3%) HN FPDs, 121 (30.3%) CC FPDs, and 82 (20.5%) ZC FPDs fabricated from presintered 3 mol% yttria-stabilized zirconia (mean time of service, 6.85 ±3.25 years) were evaluated. Of these, 278 (69.5%) FPDs were provided by dentists and 122 (30.5%) by dental students. Five- and 10-year survival, chipping-free survival, and success rates were calculated using the Kaplan-Meier method and compared with the log-rank test. Risk factors were assessed using Cox regression analysis. The study was exploratory, so all P values were considered exploratory and descriptive. RESULTS: The 5- and 10-year survival rates were 94.7% and 77.8% for HN, 93.7% and 81.2% for CC, and 92.9% and 53.3% for ZC FPDs, respectively, indicating no clear difference in survival among the framework materials. The 5- and 10-year chipping-free rates were 94.1% and 82.8% for HN, 96.1% and 78.9% for CC, and 82.6% and 62.2% for ZC FPDs, respectively, indicating a difference between HN and ZC, and CC and ZC restorations. The 5- and 10-year success rates were 83.7% and 55.3% for HN, 86.5% and 51.4% for CC, and 68.9% and 30.2% for ZC FPDs, respectively, indicating a difference between HN and ZC, and CC and ZC restorations. The Cox regression model indicated framework material as an influencing risk factor for success, and this influence persisted when chipping was investigated. Compared with zirconia, the use of a metal alloy reduced the risk of chipping or the occurrence of complications by up to one-third. CONCLUSIONS: All FPDs showed high 5-year survival rates and acceptable 10-year survival rates with no strong differences among the materials. Higher success and chipping-free rates were observed for both HN and CC restorations compared with ZC restorations. Metal frameworks had a lower risk for complications or veneer chipping than zirconia frameworks.

Influence of artificial landmarks on the accuracy of complete arch scans in the partially edentulous maxilla: An in vitro study.

STATEMENT OF PROBLEM: Scan path length and the presence of edentulous alveolar ridge sections have a negative influence on scanning accuracy. How different artificial landmarks combined with an adapted scanning method affect accuracy is unclear. PURPOSE: The purpose of this in vitro study was to determine the influence of 2 different artificial landmarks combined with an adapted scanning method on the scanning accuracy of a partially edentulous maxillary model. MATERIAL AND METHODS: The model simulated a maxilla with 6 prepared teeth to accommodate a complete arch fixed partial denture. Five ceramic precision balls (ball center P1-P5), distributed buccally to the dental arch, were used to detect the dimensional and angular changes between the reference model and the intraoral scans. One intraoral scanner (Primescan) was used to make 30 scans each with either the scanning strategy recommended by the manufacturer (M) or with an adapted scanning strategy and the use of a bar (B) or 4 plates (P) as artificial landmarks in the dorsal palate. Data were statistically analyzed using a generalized least squares regression model (α=.05). RESULTS: Scanning with artificial landmarks reduced the maximum absolute distance deviations (M: 249 µm, B: 190 µm, P: 238 µm) and the maximum angle deviations (M: 0.31 degrees, B: 0.28 degrees, P: 0.26 degrees). Vertical distance deviations were improved by 10 to 50% with the use of artificial landmarks. Absolute mean distance deviations were significantly lower for group M (P<.001). In contrast, with artificial landmarks, mean angle (P<.001) and mean vertical distance deviations (P<.014) improved significantly. CONCLUSIONS: Scanning with artificial landmarks in the dorsal palate combined with an adapted scanning method improved the scanning accuracy and reliability of vertical distance deviations.

The effect of titanium anodization on the bond strength of 10-methacryloyloxydecyl dihydrogen phosphate (10-MDP) resin cement.

PURPOSE: To examine the effects of anodization and different surface modifications of titanium on bond strength to 10-methacryloyloxydecyl dihydrogen phosphate (10-MDP) resin cement. MATERIALS AND METHODS: Grade 5 titanium alloy disks (n = 160) were assigned to one of five prebonding surface treatment study groups (polished; polished and anodized; polished, etched, and anodized; sandblasted; sandblasted and anodized). Disks were adhesively bonded with 10-MDP cement (Panavia 21; bonding area: 3.3 mm in diameter) to resin cylinders. In each study group, tensile bond strength tests were conducted after 24 ± 1 hours and after 6 months (180 ± 2 days) of water storage (n = 16 specimens per water storage subgroup). Debonded specimens were stereomicroscopically analyzed to determine their fracture mode. Statistics included one-way and multifactorial analysis of variance and Tukey post hoc tests (α = .05). RESULTS: Anodization and water storage did not significantly (P ≥ .389) affect tensile bond strength. Although subgroups of polished samples had significantly (P ≤ .031) lower bond strengths (subgroup mean values: 20 to 26 MPa) than etched or sandblasted samples (subgroup mean values: 29 to 33 MPa), they nonetheless exceeded the empirical threshold of 10 MPa used as a criterion for clinical recommendation. The fracture mode of all test specimens was predominantly cohesive. CONCLUSION: Anodization of titanium surfaces can be performed without weakening the adhesion of 10-MDP-based resin cement to titanium.

In vitro accuracy of digital and conventional impressions in the partially edentulous maxilla.

OBJECTIVES: This in vitro study compared the dimensional accuracy of conventional impressions (CI) with that of digital impressions (DI) in a partially edentulous maxilla. DIs were made by two intraoral scanners, Omnicam (OC) and Primescan (PS). MATERIALS AND METHODS: CI and both intraoral scanners were used to take 30 impressions of two identical reference models. CIs were poured with type 4 gypsum and the saw-cut models were digitized. The reference models simulated a maxilla with six prepared teeth that accommodated a cross-arch fixed partial denture. Center points of five precision balls and center points at the margin level of each prepared tooth were used to detect changes in dimensions and tooth axis between the reference model and the scans. RESULTS: For DI, the largest deviations (176 µm for OC and 122 µm for PS) occurred over the cross-arch. For CI, the largest deviation (118 µm) occurred over the anterior segment. For shorter distances up to a quadrant, DI was superior to CI. For longer scan distances, DI was comparable (2 sextant and anterior segment) or inferior (cross-arch) to CI. Vertical and tooth axis deviations were significantly smaller for CI than for DI (p < 0.001). CONCLUSIONS: The impression method affected the impression accuracy of a partially edentulous maxilla with prepared teeth. DI is recommended for scans up to a quadrant. Larger scan volumes are not yet suitable for fabricating a fixed partial denture because of the high scatter of accuracy values. CLINICAL RELEVANCE: In contrast to conventional impressions, digital impressions lead to comparable or better results concerning scans up to a quadrant. Consequently, for larger scan volumes, several smaller scans should be performed or, if restoration-related not possible, it is recommended to take conventional impressions.

Oral health status of nursing staff in Ilembula, Wanging'ombe District, Njombe region, Tanzania: a cross-sectional study.

BACKGROUND: Owing to the reduced dental treatment infrastructure in the Tanzanian highlands, maintaining good oral health is a challenge for not only the general population but also individual professional groups. In this study, the caries prevalence and, subsequently, the prosthetic treatment needs of the nurses of the Ilembula Lutheran Hospital (ILH) and Ilembula Institute of Health and Allied Sciences (IIHAS), Tanzania, were investigated. MATERIALS AND METHODS: One hundred and sixty-eight ILH and IIHAS nurses and nursing students (87 women, 81 men; age 23.1 ± 6.1 years, range 18-58 years) participated in this cross-sectional study conducted in February 2020. The participants were examined at the dental office of ILH. The Decayed, Missing, and Filled Teeth (DMF/T) Index, Simplified Oral Hygiene Index, and details regarding edentulism, nutrition habits, and socioeconomic factors were collected. Linear regression and binary logistic regression were used for statistical analysis. RESULTS: The mean DMF/T-Index was 6.30 ± 4.52. In 7.14% of the investigated nurses, no dental plaque was detected. An enhanced prosthodontic treatment (Kennedy Class III) demand was identified in 31.50% of the participants, and 4.80% of the participants required treatment for acute malocclusion. Oral hygiene products were used by 99.4% of the patients. CONCLUSIONS: The current oral health situation of the study participants showed a moderate restorative and prosthetic treatment demand in the rural area of Tanzania. The development of an interdisciplinary oral health prophylaxis system could be a means to remedy this situation.

In Vitro Analysis of the Mechanical Properties of Hypoallergenic Denture Base Resins.

The development of hypoallergenic denture resins is key to the treatment of patients with allergies to polymethyl methacrylate (PMMA). In this study, the in vitro mechanical properties of hypoallergenic and PMMA denture base resins were compared. Ninety-six test specimens of hypoallergenic denture base resins (Polyan Plus®, Sinomer, TMS Acetal Dental, Erkocryl) and 72 test specimens of PMMA-based denture base resins (Paladon 65, PalaXpress, SR-Ivocap) were fabricated. The flexural strength, elastic modulus, compressive strength, macro- and microhardness, average roughness, water absorption, and water solubility of the resins were measured. None of the hypoallergenic denture resins matched all the mechanical properties of the PMMA resins. Polyan Plus® and TMS Acetal Dental were closest to matching the mechanical properties of the PMMA resins, and TMS Acetal Dental had some superior properties. Consequently, Polyan Plus® and TMS Acetal Dental hypoallergenic resins are recommended for further investigation as potential alternatives to PMMA resins for the fabrication of removable dentures.

Effect of scan-path length on the scanning accuracy of completely dentate and partially edentulous maxillae.

STATEMENT OF PROBLEM: The accuracy of fit of fixed partial dentures is directly dependent on the accuracy of a digital scan. However, the influence of scan-path length on scanning accuracy is unclear. PURPOSE: The purpose of this in vitro study was to evaluate how scan-path length influenced the scanning accuracy of a completely dentate or partially edentulous maxilla captured by 3 intraoral scanners: Omnicam AC (OC), TRIOS 4 (TR), and Primescan (PS). MATERIAL AND METHODS: Each intraoral scanner was used to make 30 scans each of the 2 clinical scenarios (completely dentate and partially edentulous) simulated with a reference model. The partially edentulous model simulated a maxilla with 6 prepared teeth to support a complete arch fixed partial denture. The missing teeth were then added to create a completely dentate model. The prepared teeth were later used to determine distance, angular, and tooth-axis deviations between the reference model (digitized with high precision before the tests) and the intraoral scans. Data were statistically analyzed by using a linear model or, if not applicable, a type II ANOVA (α=.05). RESULTS: Distance deviations increased linearly as the scan-path length increased. In contrast, angular and tooth-axis deviations did not increase linearly. All types of deviation differed depending on the scanning system used. Regarding the 90% quantile values, total distance deviations related to scan-path length amounted to 1.31 µm/mm (OC), 1.00 µm/mm (PS), and 1.45 µm/mm (TR) for the completely dentate maxilla and 1.10 µm/mm (OC), 1.46 µm/mm (PS), and 1.40 µm/mm (TR) for the partially edentulous maxilla. CONCLUSIONS: Distance deviations became larger as the scan-path length increased.

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.

Impact of the Veneering Technique and Framework Material on the Failure Loads of All-Ceramic Computer-Aided Design/Computer-Aided Manufacturing Fixed Partial Dentures.

OBJECTIVES: Zirconia (Y-TZP) ceramics are considered as posterior fixed partial denture (FPD) materials; however, their applications are limited due to chipping. The use of monolithic lithium disilicate (LiDi) glass ceramics in posterior FPDs can be advantageous. This in vitro study aims to compare the loads until failure of posterior Y-TZP-FPDs and LiDi-FPDs before and after aging.