Monolithic hybrid abutment crowns: Influence of crown height, crown morphology and material on the implant-abutment complex.

PURPOSE: This in vitro study investigated the influence of material selection, crown morphology, and vertical crown height on the biomechanical behavior of monolithic hybrid abutment crowns (HACs). METHODS: Ninety implants were embedded in accordance with ISO standard 14801; ninety HACs were mounted (N=90). Monolithic crowns with varying group-specific designs were luted using titanium bases. HACs were fabricated from monolithic lithium disilicate ceramic (LD) or zirconia-reinforced lithium silicate ceramic (ZLS). The crown morphology was either maxillary premolar (LD_PM, ZLS_PM) or molar (LD_MO). The three groups were further divided into three subgroups of ten specimens, each designed with a small (7.5 mm), middle (10.5 mm), and high (13.5 mm) configuration of crown heights (N=10). A load-to-failure test at 30° off-axis was conducted using a universal testing machine until failure. For statistical analysis, Kolmogorov-Smirnov and Mann-Whitney U tests were conducted (P < 0.05). RESULTS: All LD_MO groups presented the highest failure values (808.7 to 947.9 N), followed by the LD_PM (525.8 to 722.8 N) and ZLS_PM groups (312.6 to 478.8N). A comparison between LD and ZLS materials (P < 0.001) as well as the crown morphology (P < 0.001) showed significant differences in failure values. The values in the subgroups of ZLS_PM (low, middle, high) decreased as the crown height increased. The fracture modes showed no consistent patterns across the test groups. CONCLUSIONS: Material selection, crown morphology, and vertical crown height appear to be important factors that may influence the clinical failure values and patterns of HACs.

Clinical performance of monolithic lithium disilicate hybrid abutment crowns over at least 3.5 years.

PURPOSE: Hybrid abutment crowns (HACs) made from monolithic ceramics represent an efficient option for single restorations on implants. However, long-term data are scarce. The purpose of this clinical trial was to evaluate the survival and complication rates of CAD-CAM fabricated HACs over a time period of at least 3.5 years. MATERIALS AND METHODS: Twenty-five patients with a total of 40 HACs made of monolithic lithium disilicate ceramic bonded to a titanium base CAD-CAM abutment were retrospectively evaluated. All implants and screw-retained restorations were placed and manufactured in the same department of a university hospital. Only crowns that had been in service for more than 3.5 years were included in the study. HACs were evaluated regarding technical and biological complications. Functional Implant Prosthodontic Scores (FIPS) were obtained. RESULTS: The mean observation time was 5.9 ± 1.4 years. Implant survival was 100%, and HAC survival was 97.5%. Over the observation period, one crown fracture was observed, necessitating refabricating of the restoration. Three minor biological complications were found. The overall mean FIPS score was 8.69 ± 1.12 points. CONCLUSIONS: Within the limitations of this study, monolithic screw-retained HACs milled from lithium disilicate ceramics and bonded to titanium bases appeared to be a reliable treatment option over more than 3.5 years due to their low biological and technical complication rates.

CAD/CAM full-mouth rehabilitation of an elderly patient: One-piece digital complete denture meets multilayered zirconia with gradient technology.

OBJECTIVE: This article highlights a CAD/CAM complete-mouth rehabilitation in an 82-year-old patient by means of a complete maxillary prosthesis and mandibular implant- and tooth-supported fixed restorations made from multilayered zirconia. CLINICAL CONSIDERATIONS: Comprehensive complete-mouth rehabilitations in elderly patients with adaptation of the occlusal vertical dimension (OVD) often present particular challenges. This applies especially when exacting functional and esthetic requirements are to be met and the treatment should not cause the patient too much effort, still ensuring the highest level of quality and efficiency and a low intervention rate. CONCLUSION: The digital approach used for the present patient allowed for an efficient treatment procedure, facilitated virtual evaluations using a face-scan, and enhanced the predictability of the prosthodontic outcome. The approach enabled some steps required in the conventional protocol to be omitted, resulting in a straightforward clinical treatment with minimal strain on the patient. CLINICAL SIGNIFICANCE: Because of the comprehensive recording of extraoral and intraoral data, for example with a facial scanner, it was possible to transfer a digital replica of the patient to the dental laboratory technician. With this protocol, many steps can be performed in the absence of the real patient.

Exploratory Analysis of the Effects of Celecoxib on Cognitive Function in Vortioxetine-Treated Patients With Major Depressive Disorder in the PREDDICT Study: A Randomized, Double-Blind, Placebo-Controlled Clinical Trial.

Objective: Major depressive disorder (MDD) remains difficult to treat, with many patients resistant to existing treatments or experiencing relapse. Cognitive dysfunction is associated with more severe clinical outcomes. Vortioxetine has shown efficacy in remediating depression-associated cognitive impairment. Anti-inflammatory augmentation of antidepressants is a new strategy in treating depression and has not previously been assessed for effects on cognition in depression.Methods: Exploratory analyses were performed on secondary outcome cognitive data from the PREDDICT parallel-group, randomized, double-blind, placebo-controlled trial at the University of Adelaide (Australia). Participants (N = 119) with MDD (validated with Mini-International Neuropsychiatric Interview for DSM-IV) were treated with vortioxetine and celecoxib or vortioxetine and placebo for 6 weeks between December 2017 and April 2020. Measures included objective cognition composite scores (Choice Reaction Time, N-Back, Digit Symbol Substitution Test, Trail Making Task Part B), subjective cognition scores (Perceived Deficits Questionnaire), and global cognition composite scores (combined objective and subjective scores) derived from the THINC integrated tool (THINC-it). High-sensitivity C-reactive protein (hsCRP) measured at baseline and week 6 was tested for a predictive relationship with cognitive outcomes.Results: Cognition composite scores demonstrated improvement by week 6 in both treatment groups. However, there was no significant interaction between change over time and treatment group. HsCRP did not have a significant relationship with any tested cognition measures.Conclusions: Both treatment groups showed a reduction in depression-associated cognitive impairment. No superior clinical effect was reported for the add-on celecoxib group. HsCRP was modulated by neither vortioxetine nor add-on celecoxib.Trial Registration: ANZCTR identifier: ACTRN12617000527369.

The Head, the Heart, and the Community: Piloting a Brief Home-Based Mindfulness Intervention for Couples With Low Income.

Although mindfulness is documented to reduce both individual and relationship stress and has the flexibility to be taught anywhere (e.g., at home, clinic setting, etc.), research examining mindfulness interventions among individuals with low income and economic marginalization (LIEM; APA, 2019), or persons whose economic position negatively impacts their health or well-being due to factors such as access to healthcare, is limited. To address this gap, the author and colleagues used Community Based Participatory Research methods to develop a brief, couple-based, mindfulness intervention tailored for communities with LIEM (see Lenger et al., 2022). The present study tested this newly developed brief, couple-based, mindfulness intervention's effectiveness in improving individual and relationship health through 1- and 2-months post-intervention. The intervention was piloted on a sample of 39 couples with an overrepresentation of couples with LIEM. To improve access to care, couples could participate in their home or a variety of local clinics. Thirty-nine couples received the intervention and completed assessments on mindfulness, depression, anxiety, stress, relationship satisfaction, and communication at baseline, 1-month, and 2-months post-intervention. Results revealed that mindfulness, depression, and relationship satisfaction improved from baseline to 1-month post-intervention. Mindfulness improved at a greater rate for couples with LIEM relative to couples with higher incomes. From baseline to 2-months post-intervention, depression and stress significantly improved at similar rates for couples with higher income and couples with LIEM. Thus, this study indicates that mindfulness can be taught in a brief, two-session format, and can have favorable outcomes on individual and relationship functioning.

Forced surgical extrusion using an axial tooth extraction system as a practicable technique for preserving severely destroyed teeth? - Clinical outcomes up to 4.8 years.

OBJECTIVE: Several extrusion techniques have been described to restore teeth with insufficient coronal tooth structure and to avoid their extraction. Still, there is little evidence for a treatment concept combining surgical extrusion using an atraumatic axial extraction system. MATERIALS AND METHODS: A total of nine patients, each with an iso- or subgingival fractured tooth, were retrospectively examined. Treatment of the damaged tooth comprised an atraumatic forced surgical extrusion performed with an axial tooth extraction system and a more coronal positioning within the socket. The teeth were initially splinted and subsequently restored. The follow-up period was up to 57.1 months and averaged 36.5 (SD: ±13.5) months. RESULTS: All nine teeth were still in situ, without signs of inflammation. During the period of the provisional restoration, six prosthetic complications occurred, which were resolved with little effort, whereas, success rate for the definitive restoration was 100%. No biological complications were observed concerning the root apex or soft tissue. The radiographically measured mean extrusion distance was 3.4 (SD: ±1.0) mm, so that a sufficient prosthetic ferrule could be reestablished. CONCLUSIONS: Surgical extrusions using an axial tooth extraction system demonstrate low biological and prosthetic complications rates over observation time. CLINICAL SIGNIFICANCE: The presented extrusion approach preserves soft and hard tissue and is an efficient treatment option for severely destroyed teeth. Saving hopeless teeth by this relatively predictable and feasible procedure has hardly any disadvantages for patients, and in case of failure, an implant or fixed partial denture are still an option.

Predictable esthetics in hybrid and resin-based CAD/CAM restorative materials: Translucency as a function of material thickness.

AIM: The CAM of esthetically pleasing monolithic dental restorations presents with specific challenges. One vital parameter to consider is the translucency of the materials. Previous studies have proven a correlation between translucency and material thickness for various all-ceramic materials. The aim of the present study was to assess and define the relationship between thickness and translucency in modern resin-based restorative materials. MATERIALS AND METHODS: Specimens fabricated from two resin nano-ceramics (Cerasmart, Lava Ultimate), a polymer-infiltrated ceramic network (Vita Enamic), and a polymethyl methacrylate (Telio CAD) were examined, representing these different material classes. For each material, 12 specimens (n = 12) were fabricated in five thicknesses (0.4, 0.7, 1.0, 1.3, and 1.6 mm; N = 240). The translucency was measured with a spectrophotometer. The total light transmittance for each specimen was calculated applying specialized software. Regression curves were fitted to the results and their coefficient of determination (R2) fit was determined. RESULTS: Logarithmic regression curves showed the best R2 approximation (Cerasmart: R2 = 0.994; Vita Enamic: R2 = 0.978; Lava Ultimate: R2 = 0.997; Telio CAD: R2 = 0.997) to the light transmission values. CONCLUSIONS: The results of the present study indicate that the translucency of resin-based materials can be calculated using a mathematic approach to estimate their optical behavior. Cerasmart, Lava Ultimate, Vita Enamic, and Telio CAD exhibit a logarithmic relationship between material thickness and translucency. By determining material-specific coefficients for this logarithmic function, the resulting translucency can be computed for any given material thickness.

Atraumatic intraoral scans and virtual hybrid casts for custom implant abutments and zirconia implants: Accuracy of the workflow.

STATEMENT OF PROBLEM: Making impressions of 2-piece implants is typically associated with the repeated disassembly and reassembly of superstructures and related to soft-tissue trauma. Intraoral scanning of 1-piece zirconia implants is problematic because scan bodies are not readily available. Whether using virtual hybrid casts generated by merging intraoral scan data with the known surface geometry of abutments can solve these difficulties is not clear because data on accuracy of the workflow are sparse. PURPOSE: The purpose of this in vitro study was to evaluate the accuracy of virtual hybrid casts with respect to the impact of different gingival situations. The workflow was designed to render pointless the use of impression posts and scan bodies and avoid any displacement of the gingiva. MATERIAL AND METHODS: The mandibular right first molar in a typodont was replaced with a 2-piece titanium implant with a custom abutment and then a 1-piece zirconia implant. Three situations representing different gingival heights covering the abutments were simulated. Twelve intraoral scans were made for each situation to capture the recordable parts of the abutments, and virtual hybrid casts were constructed by superimposing and merging the intraoral scan data with the original laboratory scan data of the abutments. Hybrid casts were compared with reference data by using the root mean square error. Scan body-related and cast scan-related protocols were performed representing conventional digital workflows. Statistical analysis with the Kolmogorov-Smirnov, Kruskal-Wallis, and Mann-Whitney U tests with the Bonferroni correction was conducted with a statistical software program (α=.05). RESULTS: Deviation was low in the hybrid casts of the custom abutment when the entire abutment was recorded (6.5 µm; IQR: 3.0 µm), when the preparation margin was disguised (7.0 µm; IQR: 1.0 µm), and when half of the abutment was covered (8.0 µm; IQR: 4.0 µm). The accuracy in the 1-piece zirconia implant was 10.0 µm (IQR: 4.0 µm) when the whole surface of the abutment was visible and 12.5 µm (IQR: 6.0 µm) when the preparation margin was covered. When only half of the abutment was captured, a larger deviation of 22.0 µm (IQR: 7.0 µm) was observed. The hybrid cast concept demonstrated superior accuracy compared with protocols using scan bodies (76.0 µm; IQR: 27.0 µm) and cast scans (23.0 µm; IQR: 15.0 µm). CONCLUSIONS: Digital intraoral scanning and the generation of virtual hybrid casts provide high accuracy and are suitable for the fabrication of single-implant-supported restorations. The atraumatic procedure avoids tissue manipulation and reduces clinical effort.

Prospective Clinical Split-Mouth Study of Two-Wing­Retained Resin-Bonded Anterior Fixed Dental Prostheses with Metallic and Ceramic Frameworks: 5-year Results

PURPOSE: To analyze the clinical performance of two-wing­retained resin-bonded fixed dental prostheses (RBFDPs) after 5 years of clinical use with respect to technical and biologic complications, as well as survival and success rates. MATERIALS AND METHODS: RBFDPs were fabricated from 3Y-TZP zirconia layered by hand (Lava Frame veneered with Lava Ceram; 3M ESPE) or metal (Remanium Star, Dentaurum; layered with Reflex, Wieland). The primary endpoints were debonding and fracture. The secondary endpoints (marginal integrity, marginal discoloration, abrasion of antagonist dentition, patient satisfaction, Gingival Index, and side effects) were evaluated at baseline and after 5 years. Survival and success rates were calculated using the Kaplan-Meier method. Log-rank test was used to compare the survival and success rates of the different materials. RESULTS: The mean observation time was 6 years and 10 months. The estimated cumulative success rate after 5 years was 88.9% ± 10% for metal-supported and 33% ± 16% for all-ceramic two-wing RBFDPs. After conversion into one-wing RBFDPs, the survival rate was 100% in both groups. Debonding of one of the two wings was the major complication. One zirconia framework fracture occurred. Metal-based two-wing RBFDPs showed a significantly higher success rate, but lower esthetic evaluation. CONCLUSION: Due to a reduction in technical complication rate and less invasiveness, one-wing RBFDPs should be preferred over two-wing RBFDPs whenever possible.

Influence of monolithic restorative materials on the implant-abutment interface of hybrid abutment crowns: An in vitro investigation.

Purpose This in vitro study aimed to investigate the long-term performance, stability, and fracture mode of monolithic hybrid abutment crowns, and the effect of different materials on the implant-abutment interface (IAI).Methods Eighty monolithic hybrid abutment crowns luted on titanium bases were manufactured from 3Y-TZP zirconia (ZY3), "Gradient Technology" zirconia (ZY35), 5Y-TZP zirconia (ZY5), lithium disilicate ceramic (LDS), zirconia-reinforced lithium silicate ceramic (ZLS), polymer-infiltrated ceramic network (MHY), polymethylmethacrylate (PMA), and 3D-printed hybrid composite (PHC) (n = 10 for each material). Eighty implants (Camlog Progressive-Line, diameter: 3.8 mm) were embedded in accordance with ISO standard 14801, and crowns were mounted. After artificial aging (1.2 × 106 cycles, 50 N, thermocycling), intact specimens were loaded 30° off-axis in a universal testing machine until failure.Results Seven specimens in the PHC group failed during artificial aging, and all the others survived. There were two subgroups based on the one-way analysis of variance and Dunnett's test (P < 0.05) of the mean fracture load values. The first comprised Z3Y, ZY35, Z5Y, and LDS, with mean fracture loads between 499.4 and 529.7 N, while the second included ZLS, MHY, and PMA, with values in the 346.2-416.0 N range. ZY3, ZY35, ZY5, and LDS exhibited irreversible, visible deformations of the implant shoulders with varying dimensions after load-to-fracture tests.Conclusions Crowns made of LDS, ZLS, MHY, and PMA may act as potential stress breakers, and prevent possible deformation at IAIs. Further clinical studies need to assess if these materials also withstand relevant loads in-vivo.

Digital Veneering Techniques for Zirconia Implant-Supported Single Crowns-Bond Strength and Clinical Application.

PURPOSE: To evaluate the shear bond strength (SBS) of different digital veneering techniques for zirconia and to critically discuss its suitability for application in single-implant prosthetics. MATERIALS AND METHODS: A total of 112 square-shaped zirconia specimens were provided with four different veneering materials (n = 28 per group): a glass-ceramic (group GLA), a feldspathic ceramic (group FEL), a polymer-infiltrated ceramic network (group PIC), and a resin nanoceramic (group RNC). Discs in group GLA were sintered onto the core material, whereas all other specimens were adhesively connected. In each group, 14 specimens (GLA0, FEL0, PIC0, RNC0) were subjected to SBS testing before thermocycling, and the other 14 (GLA1, FEL1, PIC1, RNC1) were tested after thermocycling (10,000 cycles). Data were analyzed by applying SPSS software (P < .05). The surfaces and fracture patterns of the specimens were examined using scanning electron microscopy (SEM). RESULTS: Mean SBS values ranged from 14.09 ± 3.87 MPa (RNC1) to 40.82 ± 4.91 MPa (GLA0). Group GLA presented higher values than all other groups (P < .001). Groups FEL, PIC, and RNC showed no statistically significant differences between them. SBS decreased after thermocycling, but no significant impact was found. Every group exhibited a characteristic failure mode. CONCLUSION: All digital veneering techniques sufficed to present clinically acceptable SBS values and might be viable alternatives in implant prosthetics. However, some have yet to demonstrate their long-term clinical suitability. At present, lithium disilicate-veneered zirconia abutments and monolithic lithium disilicate hybrid abutment crowns seem to present a proven and reliable restorative option.

Influence of Pre-Treatment and Artificial Aging on the Retention of 3D-Printed Permanent Composite Crowns.

The aim of this in vitro study is to investigate the bonding properties of a 3D-printable permanent composite material in comparison to milled composite materials. The tested materials are 3D-printed BEGO VarseoSmile Crown plus (VA1_ab, VA1_nt, VA2_ab, VA2_nt), Vita Enamic (EN1, EN2), and 3M Lava Ultimate (UL1, UL2) (N = 64; n = 8). For this purpose, all crowns are luted to polymer tooth stumps #46 (FDI) using dual-curing luting composite, strictly according to the manufacturer's instructions. VA1_ab and VA2_ab are additionally airborne-particle abraded. 4 groups (VA2_ab, VA2_nt, EN2, UL2) are artificially aged (1,200,000 cycles, 50 N, 10,000 thermocycles), whereby no specimen has failed. All 64 specimens undergo pull-off testing until retention loss. The mean forces of retention-loss is 786.6 ± 137.6 N (VA1_nt, *), 988.6 ± 212.1 N (VA2_nt, *, Ɨ), 1223.8 ± 119.2 N (VA1_ab, Ɨ, ǂ), 1051.9 ± 107.2 N (VA2_ab, *, Ɨ), 1185.9 ± 211.8 N (EN1, Ɨ, ǂ), 1485.0 ± 198.2 N EN2, ǂ), 1533.8 ± 42.4 N (UL1, ǂ), and 1521.8 ± 343.4 N (UL2, ǂ) (one-way ANOVA (Scheffé method); p < 0.05; *, Ɨ, ǂ: group distribution). No characteristic failure modes can be detected. In conclusion, all of the pull-off forces reflect retention values that seem to be sufficiently high for clinical use. Additional airborne-particle abrasion of VA does not result in significantly better retention but can be recommended.

Up to 10-Year Incidence of Complications in Fixed vs Removable Implant-Supported Restorations for Edentulous Arches.

PURPOSE: To retrospectively compare the incidence of biologic and prosthetic complications in implant-supported fixed dental prostheses (FDP) and removable dental prostheses (RDP) in edentulous patients after up to 10 years. MATERIALS AND METHODS: A total of 13 patients (mean age: 58.8 years, women = 9, men = 4) who had received 14 implant-supported FDPs and a total of 43 patients (mean age: 64.4 years, 22 women, 21 men) who were provided with 50 implant-supported RDPs were included in the study. The RDPs were fixed using locator attachments, ball heads, bars, or double-crowns. Technical, biologic, and prosthetic complications were assessed over a 73.3-month (± 37.7) follow-up period, and the collected data covered the period between 2000 and 2016. Using Kaplan-Meier curve and Breslow tests, the data were statistically analyzed. The level of peri-implant bone margins was determined at least every 2 years. RESULTS: Of the 328 implants placed, 2 had to be removed during the follow-up period. All implant superstructures were still in situ at the end of the observation period. The mean overall complication rate was 0.24 per restoration per year for FDPs and 0.37 per year for RDPs. Reasonable therapeutic interventions allowed for preserving and reestablishing the integrity of all implants and full operability of all superstructures. Prosthetic complications occurred about four to five times more frequently than biologic ones; however, according to Breslow test, the distribution of biologic and prosthetic complications was not significantly different (P > .05) when comparing FDPs and RDPs over 10 years. CONCLUSION: Implant-supported FDPs were not significantly more prone to complications than implant-supported RDPs over time. Prosthetic intervention was required more often than biologic interventions in both approaches.

Accuracy of surface adaptation of complete denture bases fabricated using milling, material jetting, selective laser sintering, digital light processing, and conventional injection molding.

AIM: Milling-based, subtractive fabrication of digital complete dentures represents the computer-engineered manufacturing method of choice. However, efficient additive manufacturing technologies might also prove beneficial for the indication. The aim of the present study was to evaluate the accuracy of surface adaptation of complete denture bases fabricated using subtractive, additive, and conventional manufacturing techniques. MATERIALS AND METHODS: A standardized edentulous maxillary model was digitally designed and milled. Twelve duplicated plaster casts were scanned and virtual denture bases designed accordingly. Physical complete denture bases (n = 12 per technique) were manufactured applying different digital and conventional fabrication methods: 1) CNC milling (MIL); 2) material jetting (MJ); 3) selective laser sintering (SLS); 4) digital light processing (DLP); and 5) conventional injection molding (INJ). The INJ group served as control. The intaglio surfaces of the denture bases were digitized and superposed with the surface data of the casts using a best-fit algorithm. Accuracy of surface adaptation was assessed by examining deviations. Statistical analysis was conducted using SPSS (P < 0.05). RESULTS: The milling of denture bases led to significantly better surface adaptation compared with all the other technologies (P < 0.001). The other fabrication methods in the study, including conventional manufacturing, revealed no considerable overall differences. CONCLUSIONS: As regards the accuracy of surface adaptation, all the investigated technologies adequately produced complete denture bases, with milled denture bases presenting the most superior results.

Short communication: In vitro pilot study: Are monolithic 3Y-TZP zirconia crowns too strong for titanium Implants?

PURPOSE: To report on pilot tests for a planned study on single implant-supported crowns made from different restorative materials using finite element analysis (FEA) and in vitro load-to-failure testing. MATERIALS AND METHODS: Within this pilot study, FEA was conducted using Ansys 2019 R2 to simulate stress and deformation for implant-supported crowns made of lithium disilicate ceramic (LiS2) and zirconia (3Y-TZP). Additionally, an in vitro load to failure test was conducted using two specimens per group to evaluate the failure mode and to confirm the findings from the FEA. RESULTS/CONCLUSION: FEA revealed stress areas at the palatal cervical areas of the crowns. In the load to failure test, both hybrid abutment crowns made of LiS2 fractured (410 N and 510 N) before plastic deformation of the metal implant components occurred. The monolithic hybrid abutment crowns made of 3Y-TZP did not fracture until tests were interrupted at 646-N and 690-N occlusal force, when plastic deformation of the metal implant components was visually observed.

Accuracy of intraoral scans of edentulous jaws with different generations of intraoral scanners compared to laboratory scans.

PURPOSE: Purpose of this in vitro study was to determine the accuracy of different intraoral scans versus laboratory scans of impressions and casts for the digitization of an edentulous maxilla. MATERIALS AND METHODS: A PEEK model of an edentulous maxilla, featuring four hemispheres on the alveolar ridges in region 13, 17, 23 and 27, was industrially digitized to obtain a reference dataset (REF). Intraoral scans using Cerec Primescan AC (PRI) and Cerec AC Omnicam (OMN), as well as conventional impressions (scannable polyvinyl siloxane) were carried out (n = 25). Conventional impressions (E5I) and referring plaster casts were scanned with the inEOS X5 (E5M). All datasets were exported in STL and analyzed (Geomagic Qualify). Linear and angular differences were evaluated by virtually constructed measurement points in the centers of the hemispheres (P13, P17, P23, P27) and lines between the points (P17-P13, P17-P23, P17-P27). Kolmogorov-Smirnov test and Shapiro-Wilk test were performed to test for normal distribution, Kruskal-Wallis-H test, and Mann-Whitney-U test to detect significant differences in trueness, followed by 2-sample Kolmogorov-Smirnov test to detect significant differences in precision (P < .008). RESULTS: Group PRI showed the highest trueness in linear and angular parameters (P < .001), while group E5I showed the highest precision (P < .001). CONCLUSION: Intraoral scan data obtained using Primescan showed the highest trueness while the indirect digitization of impressions showed the highest precision. To enhance the workflow, indirect digitization of the impression itself appears to be a reasonable technique, as it combines fast access to the digital workflow with the possibility of functional impression of mucosal areas.

Predictable esthetics in all-ceramic restorations: Translucency as a function of material thickness.

BACKGROUND: The esthetic outcome of a dental restoration largely depends on the translucency of the materials used, especially for monolithic restorations. Research has been published reporting a correlation between translucency and material thickness. However, no mathematical formula has been described yet. The aim of the present study was to determine the mathematical relationship between material thickness and translucency of three dental ceramic materials. MATERIAL AND METHODS: Three representative all-ceramic materials were taken out of the group of silicate ceramics (IPS Empress CAD LT), lithium X-silicate ceramics (IPS e.max CAD LT), and oxide ceramics (Lava Plus HT). Sixty specimens with five different thicknesses (0.4, 0.7, 1.0, 1.3, and 1.6 mm; N = 60, n = 12) were produced out of each ceramic (N = 180). A spectrophotometer was used to measure the transmittance coefficient tc[%] for each wavelength within the visible light spectrum, and the total light transmittance (T%) was calculated for each specimen. Linear, exponential, and logarithmic regression curves were fitted to the results. RESULTS: The logarithmic regression curves exhibited the best correlation (R2; IPS Empress CAD LT, R2 = 0.996; IPS e.max CAD LT, R2 = 0.987; Lava Plus HT, R2 = 0.907) to the transmittance values. CONCLUSION: Within the limitations of the present study, the transmittance behavior of silicate ceramics, lithium-X-silicate ceramics, and oxide ceramics can be described by a logarithmic equation. The findings of this study therefore suggest that the optical behavior might be calculable by a mathematical approach.

Efficiency of occlusal and interproximal adjustments in CAD-CAM manufactured single implant crowns - cast-free vs 3D printed cast-based.

PURPOSE: The aim of this study was to evaluate the efficiency of occlusal and interproximal adjustments of single implant crowns (SIC), comparing a digital cast-free approach (CF) and a protocol using 3D printed casts (PC). MATERIALS AND METHODS: A titanium implant was inserted at position of lower right first molar in a typodont. The implant position was scanned using an intraoral scanner and SICs were fabricated accordingly. Ten crowns (CF; n = 10) were subject to a digital cast-free workflow without any labside occlusal and interproximal modifications. Ten other identical crowns (PC) were adjusted to 3D printed casts before delivery. All crowns were then adapted to the testing model, simulating chair-side adjustments during clinical placement. Adjustment time, quantity of adjustments, and contact relationship were assessed. Data were analyzed using SPSS software (P < .05). RESULTS: Median and interquartile range (IQR) of clinical adjustment time was 02:44 (IQR 00:45) minutes in group CF and 01:46 (IQR 00:21) minutes in group PC. Laboratory and clinical adjustment time in group PC was 04:25 (IQR 00:59) minutes in total. Mean and standard deviation (±SD) of root mean squared error (RMSE) of quantity of clinical adjustments was 45 ± 7 µm in group CF and 34 ± 6 µm in group PC. RMSE of total adjustments was 61 ± 11 µm in group PC. Quality of occlusal contacts was better in group CF. CONCLUSION: Time effort for clinical adjustments was higher in the cast-free protocol, whereas quantity of modifications was lower, and the occlusal contact relationship was found more favourable.

Arithmetic Relationship between Fracture Load and Material Thickness of Resin-Based CAD-CAM Restorative Materials.

Data on the long-term behavior of computer-aided designed/computer-aided manufactured (CAD-CAM) resin-based composites are sparse. To achieve higher predictability on the mechanical behavior of these materials, the aim of the study was to establish a mathematical relationship between the material thickness of resin-based materials and their fracture load. The tested materials were Lava Ultimate (LU), Cerasmart (GC), Enamic (EN), and Telio CAD (TC). For this purpose, 60 specimens were prepared, each with five different material thicknesses between 0.4 mm and 1.6 mm (N = 60, n = 12). The fracture load of all specimens was determined using the biaxial flexural strength test (DIN EN ISO 6872). Regression curves were fitted to the results and their coefficient of determination (R2) was computed. Cubic regression curves showed the best R2 approximation (LU R2 = 0.947, GC R2 = 0.971, VE R2 = 0.981, TC R2 = 0.971) to the fracture load values. These findings imply that the fracture load of all tested resin-based materials has a cubic relationship to material thickness. By means of a cubic equation and material-specific fracture load coefficients, the fracture load can be calculated when material thickness is given. The approach enables a better predictability for resin-based restorations for the individual patient. Hence, the methodology might be reasonably applied to other restorative materials.