Publications by authors named "Martin Rosentritt"

160 Publications

Correction to: Temporary materials: comparison of in vivo and in vitro performance.

Clin Oral Investig 2021 Jul 21. Epub 2021 Jul 21.

Department of Prosthetic Dentistry, Regensburg University Medical Center, D-93042, Regensburg, Germany.

A Correction to this paper has been published: https://doi.org/10.1007/s00784-021-04067-4.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1007/s00784-021-04067-4DOI Listing
July 2021

Long-term clinical performance and complications of zirconia-based tooth- and implant-supported fixed prosthodontic restorations: A summary of systematic reviews.

J Dent 2021 Jun 11;111:103723. Epub 2021 Jun 11.

Department of Prosthetic Dentistry, UKR University Hospital Regensburg, 93042 Regensburg, Germany. Electronic address:

Objectives: To present an overview on systematic reviews on prosthodontic zirconia restorations and to discuss long-term complications as well as information on anatomical and functional changes to the masticatory system.

Data/sources: MEDLINE, EMBASE, Trip medical, and Cochrane Library databases were searched for systematic reviews up to February 2021. Bias was assessed and clinical survival and complications were analyzed.

Study Selection: 38 eligible articles published between 2006 and 2021 were included. The reviews were based on 128 in vivo studies on approximately 10,000 zirconia restorations. 5-year cumulative survival rates varied between 91.2% and 95.9% for tooth-supported (TS) single crowns (SC), 89.4% and 100% for TS multi-unit fixed dental prostheses (FDP), 97.1% and 97.6% for implant-supported (IS) SCs and 93.0% and 100% for IS FDPs. Chipping was the most often technical complication, followed by framework fracture, loss of retention, marginal discrepancies/discoloration, occlusal roughness and abutment/screw loosening. Color mismatch was the only esthetic complication. Biological complications were caries, endodontic complications, tooth fracture, periodontal disease, abrasion/attrition, persisting pain, high sensitivity, peri‑implantitis and soft tissue issues. Patients with bruxism were only examined sporadically.

Conclusions: 5-year results for zirconia restorations were satisfactory. The predominant technical problem of veneering fractures could be overcome with adapted design or fabrication and application of monolithic restorations, but reviews of clinical studies on this subject are rare. The impact of zirconia restorations on the masticatory system remains unclear.

Clinical Significance: Zirconia restorations are experiencing a rapidly increasing use in dental practice. Being highly wear-resistant, hard and durable, it can be assumed that they do not follow natural abrasion and changes in the masticatory system. Possible long-term effects on the stomatognathic system as a whole should therefore be considered.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.jdent.2021.103723DOI Listing
June 2021

Machine-driven simulation of removing luting agent remnants from implant surfaces: An investigator-independent assessment of cleaning protocols.

J Mech Behav Biomed Mater 2021 09 25;121:104584. Epub 2021 May 25.

Department of Prosthodontics, University Hospital Regensburg, Germany.

Introduction: To simulate removing luting agent remnants from crowns fixed onto implant-abutment analogs using a standardized machine-driven protocol including a scaler and air polishing or sonic.

Material And Methods: A motor-driven device was constructed that controlled the rotational speed of the specimens, machining distance, contact pressure, and working time. A standardized layer of cement (Provicol, VOCO; Cuxhaven, G; Ketac Cem, 3MEspe; Seefeld, G; or Rely X Unicem, 3MEspe, Seefeld, G) was placed onto the finishing line of the crowns luted onto titanium-abutment analogs. The cement layer was scaled with a fresh titanium scaler maneuvered by the motor-driven device and treated with air polishing or sonic. Protocol 1: Scaling only for 20s, 40s, or 60s; n=20; protocol 2: 40s of scaling plus 20s of air polishing; protocol 3: 20s of scaling plus 40s of air polishing; protocol 4: 20s of scaling plus 40s of sonic; protocol 5: 40s of scaling plus 20s of sonic; protocols 2-5: n=10. Cement remnants were counted digitally as "percentage of remnants".

Statistics: mean, standard deviation, Bonferroni post hoc tests; α=0.05.

Results: Ketac Cem was easily removed by scaling only and Provicol by scaling and air polishing, but the self-adhesive resin composite cement Rely X Unicem was not removable with the device. Only remnants of Provicol could be significantly reduced by further treatment after scaling (p<0.001).

Conclusion: The presented motor-driven device enables reproducible investigations of various cleaning protocols and is thus useful to create an overview of cleaning protocols needed for the different types of cement.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.jmbbm.2021.104584DOI Listing
September 2021

Pilot in-vitro study on insertion/removal performance of hand-cast, milled and 3D printed splints.

J Mech Behav Biomed Mater 2021 09 27;121:104612. Epub 2021 May 27.

Department of Prosthetic Dentistry, UKR University Hospital Regensburg, 93042, Regensburg, Germany. Electronic address:

Objectives: The aim of this in-vitro pilot study was to establish a splint testing method and compare insertion/removal performance of dental splints.

Materials And Methods: 56 identical lower jaw splints (n = 8 per group) were manufactured from 2x methacrylate (MA) hand-cast (reference material), deep-drawn Polyethyleneterephthalate, combined deep-draw MA hand-cast, 2x CAD/CAM-milled MA and 3D-printed MA systems. After 10 days water storage (37 °C), cyclic pull-off and insertion performance on a metal jaw was investigated. Statistics; Shapiro-Wilk-test, one-way-ANOVA; post-hoc-Bonferroni, Kaplan-Meier-survival, α = 0.05.

Results: Mean insertion/pull-off cycles varied significantly (p = 0.000) between 864 cycles (MA) and 202640 cycles (Deep Draw MA). Fracture of the splints was characterized by brittle individual fractures in the 31-34 region and most fractures in region 35 (44 of 56 splints). Finite element analysis confirmed the type and location of failure.

Conclusions: Deep-draw, cast methacrylate and combined systems showed longer insertion/pull-off system cycles in comparison to printed or milled splints. Insertion/pull-off performance showed differences between the tested splint systems and indicates the influence of the processing.

Clinical Relevance: The presented in-vitro test allowed for estimating the clinical insertion/pull-off performance of dental splints.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.jmbbm.2021.104612DOI Listing
September 2021

The Influence of Surface Preparation, Chewing Simulation, and Thermal Cycling on the Phase Composition of Dental Zirconia.

Materials (Basel) 2021 Apr 22;14(9). Epub 2021 Apr 22.

Department of Prosthodontics and Material Sciences, Leipzig University, 04103 Leipzig, Germany.

The effect of dental technical tools on the phase composition and roughness of 3/4/5 yttria-stabilized tetragonal zirconia polycrystalline (3y-/4y-/5y-TZP) for application in prosthetic dentistry was investigated. Additionally, the X-ray diffraction methods of Garvie-Nicholson and Rietveld were compared in a dental restoration context. Seven plates from two manufacturers, each fabricated from commercially available zirconia (3/4/5 mol%) for application as dental restorative material, were stressed by different dental technical tools used for grinding and polishing, as well as by chewing simulation and thermocycling. All specimens were examined via laser microscopy (surface roughness) and X-ray diffraction (DIN EN ISO 13356 and the Rietveld method). As a result, the monoclinic phase fraction was halved by grinding for the 3y-TZP and transformed entirely into one of the tetragonal phases by polishing/chewing for all specimens. The tetragonal phase t is preferred for an yttria content of 3 mol% and phase t″ for 5 mol%. Mechanical stress, such as polishing or grinding, does not trigger low-temperature degradation (LTD), but it fosters a phase transformation from monoclinic to tetragonal under certain conditions. This may increase the translucency and deteriorate the mechanical properties to some extent.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3390/ma14092133DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8122781PMC
April 2021

Characterisation of the Filler Fraction in CAD/CAM Resin-Based Composites.

Materials (Basel) 2021 Apr 15;14(8). Epub 2021 Apr 15.

Department of Dental Prosthetics and Materials Science, Leipzig University, 04103 Leipzig, Germany.

The performance of dental resin-based composites (RBCs) heavily depends on the characteristic properties of the individual filler fraction. As specific information regarding the properties of the filler fraction is often missing, the current study aims to characterize the filler fractions of several contemporary computer-aided design/computer-aided manufacturing (CAD/CAM) RBCs from a material science point of view. The filler fractions of seven commercially available CAD/CAM RBCs featuring different translucency variants were analysed using Scanning Electron Microscopy (SEM) with Energy Dispersive X-ray Spectroscopy (EDS), Micro-X-ray Computed Tomography (µXCT), Thermogravimetric Analysis (TG) and X-ray Diffractometry (XRD). All CAD/CAM RBCs investigated included midifill hybrid type filler fractions, and the size of the individual particles was clearly larger than the individual specifications of the manufacturer. The fillers in Shofu Block HC featured a sphericity of ≈0.8, while it was <0.7 in all other RBCs. All RBCs featured only X-ray amorphous phases. However, in Lava Ultimate, zircon crystals with low crystallinity were detected. In some CAD/CAM RBCs, inhomogeneities (X-ray opaque fillers or pores) with a size <80 µm were identified, but the effects were minor in relation to the total volume (<0.01 vol.%). The characteristic parameters of the filler fraction in RBCs are essential for the interpretation of the individual material's mechanical and optical properties.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3390/ma14081986DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8071413PMC
April 2021

Finite element analysis of occlusal interferences in dental prosthetics caused by occlusal adjustment.

Int J Prosthodont 2021 Feb 23. Epub 2021 Feb 23.

Purpose: To investigate the influence of occlusal interference in dental prosthetics using finite element analysis (FEA).

Materials And Methods: The FEA model designed for this study centered on an all-ceramic, bi-layered, fixed partial denture (FPD) retained on the maxillary first premolar and molar, with the second premolar replaced by a pontic. The surrounding structures, such as the neighboring teeth, antagonists, and periodontium, were modeled. Four different load cases were designed at occlusal interferences of 0, 8, 12, and 24 μm, loaded by a simulated bite force of 300 N. Principal and von Mise stresses, as well as strain, were evaluated for all included structures.

Results: For interferences of 12 and 24 μm, failure-relevant tensile stresses in the veneering layer were observed at the occlusal surfaces. Stress found in the zirconia FPD did not reach fatigue or flexural strength for any test load.

Conclusion: Peak tensile stress was observed in close proximity to occlusal contact points, increasing with increasing occlusal interference. The FEA results suggested that the majority of occlusal stress is absorbed by the deformation of the periodontal ligament. Framework failure caused by the simulated interferences was not expected. Surface defects may ultimately lead to failure due to fracture or chipping, especially in cases of weaker ceramics or veneering.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.11607/ijp.7178DOI Listing
February 2021

Multilayer zirconia: Influence of positioning within blank and sintering conditions on the in vitro performance of 3-unit fixed partial dentures.

J Prosthet Dent 2020 Dec 30. Epub 2020 Dec 30.

Researcher, Department of Prosthetic Dentistry, UKR University Hospital Regensburg, Regensburg, Germany.

Statement Of Problem: Multilayer zirconia blanks comprise material layers with different optical and mechanical properties. Whether positioning within the blank, as well as variation in the sintering procedure, will lead to restorations with different properties is unclear.

Purpose: The purpose of this in vitro study was to test the influence of sintering procedures and positioning in a multilayer blank on the in vitro performance of 3-unit zirconia fixed partial dentures.

Material And Methods: Human molars were embedded in acrylic resin and prepared for 3-unit fixed partial dentures. Anatomic contour prostheses were milled from zirconia blanks (ZirCAD Prime 16 mm) in 3 different positions: above (cusp-top at the top of the blank), central (center of the prosthesis in the center of the blank), and bottom (margins at the lower edge of the blank). Sintering time (2:26, 4:25, 9:50 hours:minutes) was varied for the central and bottom prostheses. All prostheses were glazed and adhesively bonded. Thermocycling and mechanical loading was performed at 2×3000×5 °C/55 °C in distilled water for 1.2×10 cycles at a 50-N load. Then, fracture force was determined with a universal testing device by using central loading, a Ø12-mm steel ball, a 1-mm tin foil, and a rate of 1 mm/min. Failure was defined as 10% force drop or acoustic signal (crack). Statistical analysis was performed with 1-way ANOVA and Bonferroni correction (α=.05).

Results: All fixed partial dentures survived thermocycling and mechanical loading. Fracture forces varied between 1002 ±446 N (above; 9:50 hours) and 1760 ±607 N (central; 9:50 hours). The 1-way ANOVA revealed no statistically significant differences (P=.059) among the groups. Individual significant differences (P=.048) were found between prostheses from positions above, 9:50 hours, and central, 9:50 hours. For normal and long sintering times, fracture forces were highest in the central position.

Conclusions: The sintering process and positioning of restorations within a multilayer zirconia blank have little effect on the mechanical properties of the prostheses.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.prosdent.2020.11.009DOI Listing
December 2020

In vitro performance and fracture resistance of interim conventional or CAD-CAM implant-supported screw- or cement-retained anterior fixed partial dentures.

J Prosthet Dent 2020 Sep 19. Epub 2020 Sep 19.

Professor and Engineer, Department of Prosthetic Dentistry, UKR University Hospital Regensburg, Regensburg, Germany.

Statement Of Problem: Interim restorations represent an essential clinical treatment step; however, limited information is available concerning the performance of computer-aided design and computer-aided manufacturing (CAD-CAM) interim materials.

Purpose: The purpose of this in vitro study was to evaluate the performance and fracture load of resin anterior implant-supported interim fixed partial dentures (IFPDs).

Material And Methods: Identical anterior resin IFPDs (maxillary central incisor to canine; n=16 per material) were milled from polymethylmethacrylate (PMMA) or di-methacrylate (DMA) systems with different filler content. The IFPD groups were split to simulate a chairside (cemented implant-supported prosthesis) or laboratory procedure (screw-retained implant-supported prosthesis). A cartridge DMA material served as a control. After interim cementation, combined thermocycling and mechanical loading (TCML) was performed on all restorations to approximate a maximum of 2.5 years of clinical function. Behavior during TCML and fracture force was determined, and failures were analyzed. The data were statistically investigated (Kolmogorov-Smirnov test, 1-way-ANOVA; post hoc Bonferroni, Kaplan-Meier survival, α=.05).

Results: Drop out during TCML varied between no failures and complete failure during loading. For most systems, failure occurred between 120 000 and 600 000 mechanical loading cycles. For IFPDs without a screw channel fracture, values varied between 644 ±263 N and 987 ±101 N. Those with a screw channel fracture failed between 493 ±89 N and 951 ±248 N. Individual IFPDs had significantly higher mean fracture loads (P<.002), but the mean fracture values between IFPDs with and without a screw channel were not significantly different (P>.137). Failures were characterized by fracture of the connector (n=53) followed by mixed failures (n=22) or fractures at the abutment (n=21).

Conclusions: These interim materials are sufficiently fracture resistant for the fabrication of implant-supported anterior IFPDs and are expected to survive between 6 months and 2 years before failure. The stability of IFPDs depended on the type of material but not on the restoration design (with or without a screw channel).
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.prosdent.2020.08.008DOI Listing
September 2020

Fatigue and wear behaviour of zirconia materials.

J Mech Behav Biomed Mater 2020 10 9;110:103970. Epub 2020 Jul 9.

DDS, Department of Prosthetic Dentistry, UKR University Hospital Regensburg, 93042, Regensburg, Germany.

Objectives: Comparison of in-vitro fatigue and wear performance of 3Y-, 4Y-, 5Y-TZP and lithiumdisilicate ceramic, multilayer/monolayer 4Y-TZP and variation of wall thickness at 5Y-TZP.

Method And Materials: Crowns (n = 96; 6 groups à 16) were made of 3Y-TZP-LA, 4Y-TZP (multilayer and monolayer), 5Y-TZP (0,5mm/1 mm wall thickness) and lithiumdisilicate. 8 per group were stored in water (24hrs), 8 underwent TCML (1.200.000 × 50N; 2x3000x5°/55 °C; HO, 2min cycle). Fracture force was determined by static loading (v = 1 mm/min, steel sphere with tin foil, diameter = 12 mm). Pin-on-block wear test was performed (steatite antagonist d = 3 mm; 50N, 120,000 cycles, 1.2Hz, lateral motion: 1 mm, antagonist lift: 1 mm, n = 8). Roughness, wear depth [μm] and antagonist wear were determined (3-D-laser-microscope, KJ3D, Keyence, J).

Statistics: one-way-ANOVA; Bonferroni-post-hoc-test; α = 0.05.

Results: Fracture forces varied between 1211N (5Y,TCML) and 3952N (4Y-Mult,TCML). Individual significant differences (p ≤ 0.025) were found between materials. Increase of wall thickness (5Y; 0.5 mm/1.0 mm) lead to a non-significant (p ≥ 0.442) increase of fracture force. 4Y and 4Y-multilayer zirconia showed no significantly different (p ≥ 0.073) fracture forces. Zirconia mean wear (3Y:10.0 ± 3.9 μm, 4Y:19.8 ± 3.8 μm, 5Y:10.9 ± 6.8 μm) was not significantly (p = 1.000) different. Lithiumdisilicate ceramic (149.3 ± 45.4 μm) and human enamel (434.2 ± 131.3 μm) provided significantly (p ≤ 0.002) higher wear. Antagonistic wear against lithiumdisilicate (17.5 ± 3.9%) and human enamel (6.7 ± 3.0%) was significantly (p ≤ 0.007) lower than against zirconia (4Y:31.9 ± 8.0% - 5Y:27.6 ± 5.8%).

Conclusion: Fracture force of 5Y-TZP differs from 4- or 3-Y-TZP. Mechanical characteristics and dimensional requirement of 5Y-TZP are comparable to lithiumdisilicate. Mono- or multilayer 4Y-TZP provided comparable fracture forces. Wear was comparable between zirconia systems and lower in comparison to lithiumdisilicate or enamel.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.jmbbm.2020.103970DOI Listing
October 2020

Reliability and aging behavior of three different zirconia grades used for monolithic four-unit fixed dental prostheses.

Dent Mater 2020 11 15;36(11):e329-e339. Epub 2020 Sep 15.

Department of Prosthetic Dentistry, Regensburg University Medical Center, Franz-Josef-Strauß-Allee 11, 93053 Regensburg, Germany.

Objective: To investigate the fracture resistance and phase composition of tooth supported four-unit fixed dental prostheses (FDPs) made from three different zirconia grades after loading and aging.

Methods: Seventy-two FDPs were fabricated from 3Y-TZP, 4Y-PSZ and 5Y-PSZ. This resulted in 24 FDPs per grade, subdivided into three groups (n = 8): a control group (C), a hydrothermally aged (HO, 85 °C, 90 days) group (A) and a group subjected to loading (2.5M cycles, 98N) with simultaneous thermal cycling (HO, 5-55 °C) subsequent to treatment A (AL). Subsequently, FDPs were statically loaded to fracture. Phase composition was quantified by X-ray diffraction (XRD) and μ-Raman spectroscopy. Focused ion beam (FIB) - Scanning electron microscopy (SEM) was used for visualization in-depth.

Results: Compared to 3Y-C FDPs (1233 ± 165N), reduced fracture load was found for 5Y-C FDPs (889 ± 80 N; p < .001). This did not apply for 4Y-C samples (1065 ± 111N). Treatments (A, AL) did not negatively affect the fracture load for the three grades of zirconia (p > .645). Both A and AL increased monoclinic phase content for 3Y and 4Y FDPs, whereas FIB-SEM suggests no transformability of 5Y-PSZ. 5Y-AL FDPs showed cracks and fractures at the abutment walls and restoration margins after dynamic loading. Reduced fracture load of 5Y samples as compared to 3Y and 4Y was associated with deficient transformability in the fracture zone.

Significance: Aging and loading did not negatively affect the fracture resistance of monolithic four-unit FDPs made from three grades of zirconia. Due to cracks after dynamic loading, 5Y-PSZ cannot be recommended for the clinical application of four-unit FDPs.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.dental.2020.08.002DOI Listing
November 2020

In vitro performance and fracture resistance of pressed or CAD/CAM milled ceramic implant-supported screw-retained or cemented anterior FDPs.

J Prosthodont Res 2021 Jun 9;65(2):208-212. Epub 2020 Sep 9.

Department of Prosthetic Dentistry, UKR University Hospital Regensburg.

Purpose: This study investigated the in-vitro performance of anterior implant-supported fixed dental prostheses (FDP). The effect of ceramics, fabrication, finalization and the presence of a screw-channel wa s investigated.

Methods: Identical anterior ceramic FDPs (tooth 11-13; n=80) were milled (Lithiumdisilicate (LiSiCAD, emaxCAD, Ivoclar-Vivadent), Lithiumaluminiumsilicate (LiAlSi, experimental material) or pressed (Lithiumdisilicate (LiSiPress, emaxPress, Ivoclar-Vivadent), Lithiumsilicate (ZLS, CeltraPress, Dentsply Sirona). FDP-groups (n=8 per material and group) simulated a cemented or screw-retained approach. After cementation or screwing on titanium abutments, thermal cycling and mechanical loading (TCML) was performed on all restorations to mimic 5-year clinical performance. Performance and fracture force were determined and failures were analyzed.

Statistics: (Kolmogorov-Smirnov-test, one-way-ANOVA; post-hoc-Bonferroni, multivariate-regression, α=0.05).

Results: All FDPs survived TCML without aging, cracks, fractures or chipping. For FDPs without screw channel fracture values varied between with 839.8±112.3N (LiAlSi glazed) and 1485.9±232.6N (LiSiCAD). With screw channel, fracture results varied between 701.4±220.1N (LiALSi glazed) and 1516.3±253.7N (LiSipress). The type of material had a significant influence on the fracture results (LiSi>ZLS>LiAlSi; p≤0.012). Fabrication and finalization had no influence on the results. A screw channel did not significantly (p≥0.135) reduce the fracture force of the FDPs. Type of failure was mostly characterized by a fracture of the connector (LiSi, LiAlSi) or the abutment (ZLS, LiAlSi).

Conclusions: FDPs survived TCML without failures indicating that the in vitro performance was not influenced by the tested parameters. Composition of ceramic material has significant influence on the fracture resistance of implant supported LiSi based FDPs. Screw channel, fabrication or finalization did not weaken the FDPs.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.2186/jpr.JPOR_2019_403DOI Listing
June 2021

Temporary materials: comparison of in vivo and in vitro performance.

Clin Oral Investig 2020 Nov 24;24(11):4061-4068. Epub 2020 Jun 24.

Department of Prosthetic Dentistry, Regensburg University Medical Center, D-93042, Regensburg, Germany.

Objective: The aim of this investigation was to compare clinical performance and in vitro wear of temporary CAD/CAM and cartridge crowns. This study is an approach to estimate the influence of in vivo use and laboratory simulation on temporary crowns.

Materials And Methods: A total of 90 crowns were fabricated from each temporary CAD/CAM or cartridge material. Also, 10 crowns of each material were clinically applied for 14 days, and 80 identical duplicate restorations were investigated in the laboratory after storage in water (14 days; 37 °C) and subsequent thermal cycling and mechanical loading (TCML, 240.000 × 50N ML, 600 × 5°C/55 °C). After in vivo application or in vitro aging, facture force, superficial wear (mean and maximum), surface roughness (Ra, Rz), thermal weight loss (TGA), and heat of reaction (DSC) were determined for all crowns.

Statistics: Bonferroni post hoc test; one-way analysis of variance (ANOVA); α = 0.05).

Results: The fracture resistance of the temporary materials varied between 1196.4 (CAD in vivo) and 1598.3 N (cartridge crown in vitro). Mean (maximum) wear data between 204.7 (386.7 μm; cartridge in vitro) and 353.0 μm (621.8 μm; CAD in vitro) were found. Ra values ranged between 4.4 and 4.9 μm and Rz values between 36.0 and 40.8 μm. DSC and TG analysis revealed small differences between the materials but a strong influence of the aging process.

Conclusions: Comparison of in vivo and in vitro aging led to no significant differences in fracture force and wear but differences in roughness, DSC, and TGA. SEM evaluation confirmed comparability. Comparison of CAD/CAM and cartridge temporary materials partially showed significant differences.

Clinical Relevance: In vitro aging methods might be helpful to estimate materials' properties before principal clinical application. CAD/CAM and cartridge temporary materials provided comparable good clinical performance.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1007/s00784-020-03278-5DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8275555PMC
November 2020

Laboratory performance and fracture resistance of CAD/CAM implant-supported tooth-coloured anterior FDPs.

J Dent 2020 05 20;96:103326. Epub 2020 Mar 20.

Department of Prosthetic Dentistry, UKR University Hospital Regensburg, 93042, Regensburg, Germany.

Objectives: This study investigated the in-vitro performance and fracture force of anterior implant-supported tooth-coloured fixed dental prosthesis (FDPs). Different material types with varying flexural strength and modulus of elasticity were compared with screw-retained or bonded application.

Materials And Methods: Identical anterior FDPs (tooth 11-13; n = 80) from materials (flexural strength 240-1150 MPa, modulus 7.6-210 GPa; 1x lithiumdisilicate ceramic, 2x zirconia (4Y-TZP, 5Y-FSZ), 3x resin-based composites (with different flexural strength and modulus)) were milled. FDPs were grouped into chairside (bonded) and labside (screw-retained) procedure. To simulate a 5-year clinical application, thermal cycling with mechanical loading (TCML) was accomplished. TCML-performance and fracture force were evaluated and failure patterns were analysed. Data were statistically investigated (Kolmogorov-Smirnov-test, one-way-ANOVA; post-hoc-Bonferroni, α = 0.05).

Results: TCML did not lead to any cracks, fractures or chipping on all tested FDPs. Fracture values varied between 1208.9 ± 354.6 N (experimental resin-based composite) and 2094.3 ± 293.4 N (4Y-TZP) for FDPs without screw channel. With screw channel the results ranged between 1297.9 ± 268.3 N (5Y-FSZ) and 2129.3 ± 321.7 N (4Y-TZP). The influence of the screw channel was not significant for all materials (p ≥ 0.218). Modulus of elasticity and flexural strength had influence on the fracture force only in the individual material groups. Fractures at the connector were predominant for ceramic and zirconia. Resin-based composites primarily showed radial fractures in abutment region or mixed failure types. FDPs with/without screw-channel showed comparable types of failure.

Conclusions: TCML did not lead to drop-outs or failures for all FDPs. Individual materials showed no different in-vitro performance, but varying fracture force after TCML. Independent from material, screw channels did not weaken the FDPs. All tested systems showed sufficient properties for an anterior implant application.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.jdent.2020.103326DOI Listing
May 2020

The antimicrobial and cytotoxic effects of a copper-loaded zinc oxide phosphate cement.

Clin Oral Investig 2020 Nov 20;24(11):3899-3909. Epub 2020 Mar 20.

Department of Prosthodontics, University Medical Center Goettingen, Goettingen, Germany.

Objectives: Evidence about modifications of dental luting materials to minimize biological failure at the "marginal gap" between teeth and fixed prosthodontics is scarce. We compared a copper-modified (Co-ZOP) and a conventional zinc oxide phosphate cement (ZOP) in terms of antimicrobial and cytotoxic potentials in vitro and in vivo.

Materials And Methods: Specimens of ZOP and Co-ZOP were characterized by the mean arithmetic roughness (Ra) and surface free energy (SFE). Powder components were examined using scanning electron microscopy (SEM). Energy-dispersive X-ray spectroscopy (EDX) showed elemental material compositions. In vitro microbial adhesion was shown using SEM, luminescence, and fluorescence assays. CCK-8 assays of mouse fibroblasts (L929) and human gingival fibroblasts (GF-1) were performed after 6, 24, and 48 h of specimen incubation. In vivo, ZOP and Co-ZOP specimens were applied intraorally for 12 h; biofilm accumulation was shown using SEM.

Results: Ra of ZOP and Co-ZOP showed no significant differences; SFE was significantly higher for Co-ZOP. EDX exhibited minor copper radiation for Co-ZOP, none for ZOP. In vitro fungal adhesion to Co-ZOP was significantly higher than to ZOP; in vitro streptococcal adhesion, cytotoxicity, and in vivo biofilm formation were not significantly different.

Conclusions: Co-ZOP showed low surface allocations of copper with no improved antimicrobial properties compared with conventional ZOP in vitro or in vivo.

Clinical Relevance: Antimicrobial effects and low cytotoxicity of biomaterials are important for the clinical outcome. Based on our in vitro and in vivo results, no clinical recommendation can be given for the tested Co-ZOP.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1007/s00784-020-03257-wDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7544705PMC
November 2020

Stability of screw-retention in two-piece zirconia implants: An in vitro study.

Clin Oral Implants Res 2020 Jul 31;31(7):607-614. Epub 2020 Mar 31.

Department of Oral Surgery, University Center for Dental Medicine Basel (UZB), Basel, Switzerland.

Objectives: To compare the stability of a screw-retained connection in a novel two-piece zirconia implant to a conventional titanium-based connection in an in vitro chewing simulation including artificial ageing.

Material And Methods: Incisor (I) and molar (M) shaped monolithic zirconia crowns were screw-retained on either two-piece zirconia (test) or two-piece titanium (control) implants resulting in 4 groups of 8 samples (titanium implants with incisor-shaped crowns (T-I), titanium implants with molar-shaped crowns (T-M), zirconia implants with incisor-shaped crowns (Z-I) and zirconia implants with molar-shaped crowns (Z-M). These were subjected to artificial ageing by thermal cycling (TC: 2 × 3000 × 5°C/55°C cycles of 2 min) and mechanical loading (ML: 1.2 × 10 cycles of 50 N, f = 1 Hz). Surviving samples additionally underwent a fracture force test. Kaplan-Meier plots were drawn, and two-way ANOVA was calculated taking anatomical localisation and material variables as factors.

Results: The mean corresponding survival times were lower for T-M (0.86 × 10  ± 0.31 × 10 cycles) and Z-I (0.84 × 10  ± 0.21 × 10 cycles) compared to T-I (1.14 × 10  ± 0.10 × 10 cycles) and Z-M (1.20 × 10  ± 0.10 × 10 cycles). In one-way ANOVAs for survival time dependent on either location or material, no statistically significant differences could be found (location: p = .31; material: p = .62) in one-way ANOVAs. The interaction of location and material showed significant differences (F = 21.3, p < .001).

Conclusion: The connection of the tested screw-retained zirconia crowns in two-piece zirconia implants is comparable to standard titanium implants in the specific in vitro testing.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1111/clr.13597DOI Listing
July 2020

The effect of sterilization and ultrasonic cleaning on resin cement interface of customized dental implant abutments.

J Mech Behav Biomed Mater 2020 04 4;104:103660. Epub 2020 Feb 4.

Department of Prosthodontics, Regensburg University Medical Center, Germany.

View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.jmbbm.2020.103660DOI Listing
April 2020

Influence of zirconia and lithium disilicate tooth- or implant-supported crowns on wear of antagonistic and adjacent teeth.

J Adv Prosthodont 2020 Feb 20;12(1):1-8. Epub 2020 Feb 20.

Department of Prosthetic Dentistry, UKR University Hospital Regensburg, Regensburg, Germany.

Purpose: To investigate the influence of crown material (lithium-disilicate, 3Y-TZP zirconia) and abutment type (rigid implant, resin tooth with artificial periodontium) on wear performance of their antagonist teeth and adjacent teeth.

Materials And Methods: A mandibular left first molar (#36) with adjacent human teeth (mandibular left second premolar: #35, mandibular left second molar: #37) and antagonistic human teeth (maxillary left second premolar: #25, maxillary left first molar: #26, maxillary left second molar: #27) was prepared simulating a section of the jaw. Samples were made with extracted human molars (Reference), crowned implants (Implant), or crowned resin tooth analogues (Tooth). Crowns (tooth #36; n = 16/material) were milled from lithium-disilicate (Li, IPS e.max CAD) or 3Y-TZP zirconia (Zr, IPS e.max ZirCAD, both Ivoclar Vivadent). Thermal cycling and mechanical loading (TCML) in the chewing simulator were applied simulating 15 years of clinical service. Wear traces were analyzed (frequency [n], depth [µm]) and evaluated using scanning electron pictures. Wear results were compared by one-way-ANOVA and post-hoc-Bonferroni (α = 0.05).

Results: After TCML, no visible wear traces were found on Zr. Li showed more wear traces (n = 30-31) than the reference (n = 21). Antagonistic teeth #26 showed more wear traces in contact to both ceramics (n = 27-29) than to the reference (n = 21). Strong wear traces (> 350 µm) on antagonists and their adjacent teeth were found only in crowned groups. Abutment type influenced number and depth of wear facets on the antagonistic and adjacent teeth.

Conclusion: The clinically relevant model with human antagonistic and adjacent teeth allowed for a limited comparison of the wear situation. The total number of wear traces and strong wear on crowns, antagonistic and adjacent teeth were influenced by crown material.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.4047/jap.2020.12.1.1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7040450PMC
February 2020

Flexural strength and fracture toughness of two different lithium disilicate ceramics.

Dent Mater J 2020 Mar 19;39(2):302-308. Epub 2019 Dec 19.

Department of Prosthetic Dentistry, University Hospital, Ludwig-Maximilians-University Munich.

To test the impact of the pressing furnace on flexural strength and facture toughness of the lithium-disilicate-ceramics HS10PC (HS) and IPS e.max Press (IP). Three hundred and sixty specimens (3×4×30 mm) were pressed (n=180/ceramic) using different pressing furnaces, namely Austromat 654 Press-i-dent (AUS), Programat EP5000 (PRO), and Vario Press 300 (VAR). Three-point flexural strength (n=30) and fracture toughness (n=30) were measured. Flexural strength (336-360 MPa) was not affected by pressing furnace or ceramic and showed comparable values between all groups. Fracture toughness (2.65-2.81 MPa√m) provided higher values for HS pressed using AUS compared to specimens pressed in PRO and VAR. For IP, no impact of the pressing furnace on fracture toughness was found. IP presented higher fracture toughness than HS when pressed using PRO. No correlations were found. Both lithium disilicate ceramics showed comparable flexural strength regardless of the pressing furnace. Fracture toughness depended on the ceramic and on the pressing furnace.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.4012/dmj.2019-045DOI Listing
March 2020

Fracture force of CAD/CAM resin composite crowns after in vitro aging.

Clin Oral Investig 2020 Jul 11;24(7):2395-2401. Epub 2019 Nov 11.

Department of Prosthetic Dentistry, UKR University Hospital Regensburg, 93042, Regensburg, Germany.

Objectives: The aim of this in vitro study was to investigate the influence of material, preparation, and pre-treatment on the aging and fracture force of CAD/CAM resin composite molar crowns.

Materials And Methods: CAD/CAM molar crowns (n = 80) were milled from four resin composites (Block HC, Shofu; Lava Ultimate, 3 M; Grandio Blocs, Voco; and Tetric CAD, Ivoclar Vivadent, with/without sandblasting). Extracted human teeth were prepared with optimal preparation (height 6-8 mm, angle 6-8°) or worst-case preparation (height 3.5-4 mm, angle 10-15°). Both groups were prepared with a 1-mm deep cervical circular shoulder. Crowns were adhesively bonded after corresponding tooth treatment required for the individual adhesive systems (Table 1). Specimens were aged for 90 days in water storage (37 °C) and subsequently subjected to thermal cycling and mechanical loading (TCML 3000 × 5 °C/3000 × 55 °C, 2 min each cycle, H20 distilled; 1.2 × 10 cycles à 50 N, 1.6 Hz). De-bonding and fracture force was determined.

Statistics: one-way-ANOVA; post hoc Bonferroni, α = 0.05.

Results: Four crowns of Lava Ultimate with worst-case preparation de-bonded during TCML. Individual crowns without sandblasting treatment (3x Tetric CAD with optimal preparation; 1x Tetric CAD with worst-case preparation) de-bonded during water storage. One crown of Grandio Blocs with optimal preparation showed a small chipping during TCML. All other crowns survived TCML and water storage without failure. Fracture forces differed between 1272 ± 211 N (Lava Ultimate) and 3061 ± 521 N (Tetric CAD). All Grandio Blocs and Tetric CAD crowns revealed significantly (p ≤ 0.023) higher fracture forces than Block HC or Lava Ultimate crowns. No significantly different (p > 0.05) fracture forces were found between optimal or worst-case preparation/fit groups.

Conclusions: De-bonding during water storage and TCML was dependent on material and crown pre-treatment. Therefore, surface roughening seems strongly required. Fracture forces were not influenced by preparation but by the type of material.

Clinical Relevance: Clinical success and de-bonding of CAD/CAM resin composite crowns is strongly influenced by the type of material and its pre-treatment.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1007/s00784-019-03099-1DOI Listing
July 2020

Validating laboratory simulation with resin-based materials for temporary fixed denture prostheses - Results from clinical and laboratory trials.

J Mech Behav Biomed Mater 2020 01 12;101:103431. Epub 2019 Sep 12.

Department of Prosthodontics and Materials Science, University of Leipzig, Leipzig, Germany. Electronic address:

The aim of the current study was to relate an artificial aging protocol for the analysis of dental materials to their clinical performance. 20 fixed interim restorations (crowns and fixed denture prostheses (FDPs)) fabricated from two commercially available resin-based composites (RBCs) and a previous clinical trial served as templates for the fabrication of duplicate restorations. Duplicates were subjected to artificial aging using thermal cycling and mechanical loading. Subsequent to wear analysis, templates and duplicates were loaded to fracture and were examined using thermal gravimetric analysis (TG) and differential scanning calorimetry (DSC). For both RBCs, a relevant uptake of water was identified, which was more pronounced in the duplicates. Tribological analyses indicated relevant signs of wear in both templates and duplicates. While qualitative analyses indicated macroscopically similar wear traces in templates and duplicates, data showed that wear of FDPs was underrated in the laboratory analyses. The results of the current study suggest that chewing simulation allows a proper estimation of aging processes in materials for the fabrication of fixed interim restorations. However, simulation parameters should be continuously improved using data derived from clinical settings to enhance the quality of the simulation protocols.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.jmbbm.2019.103431DOI Listing
January 2020

Dynamic fatigue of composite CAD/CAM materials.

J Mech Behav Biomed Mater 2019 10 7;98:311-316. Epub 2019 Jul 7.

Department of Prosthetic Dentistry, UKR University Hospital Regensburg, 93042, Regensburg, Germany. Electronic address:

View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.jmbbm.2019.07.002DOI Listing
October 2019

Performance of resin materials for temporary fixed denture prostheses.

J Oral Sci 2019 Jun 30;61(2):270-275. Epub 2019 Mar 30.

Department of Prosthetic Dentistry, Regensburg University Medical Center.

This study investigated the handling properties and clinical performance of two commercially available resin materials with slight differences in filler composition for the fabrication of fixed interim restorations. In a dental university setting, patients requiring prosthetic treatment were supplied with fixed interim restorations fabricated from two commercially available resin materials. To clarify the handling properties of the resin materials, dentists and undergraduate students completed a questionnaire. Prior to insertion of the definitive restoration, the interim restorations were analyzed by calibrated examiners using a modification of the United States Public Health Service criteria. Eighty-two fixed interim restorations with a mean clinical service period of 44.5 (±28.3) days were included, including 39 single crowns, 30 fixed denture prostheses, 10 blocked crowns, and 3 partial coverage restorations. No significant differences between the two materials in the rating of their handling properties were identified, with the exception of the parameter "surface". Failures due to fractures were observed in 13% of the interim restorations. No significant differences between the materials in the rating of the clinical performance were identified. These results indicate that slight changes in the filler composition of commercial formulations account for few differences in handling properties and clinical performance.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.2334/josnusd.18-0150DOI Listing
June 2019

Direct or Indirect Restoration of Endodontically Treated Maxillary Central Incisors with Class III Defects? Composite vs Veneer or Crown Restoration.

J Adhes Dent 2018 ;20(6):519-526

Purpose: The aim of this ex-vivo study was to evaluate the load capacity of direct or indirect endodontically restored maxillary central incisors with Class III defects, with or without glass-fiber posts.

Materials And Methods: Seventy-two extracted human maxillary central incisors were endodontically treated and bi-proximal Class III cavities were prepared. Specimens were randomly allocated to six groups (n = 12): direct restoration with composite (C); direct restoration with composite and additional glass-fiber post (CP); ceramic veneer restoration (V), ceramic veneer restoration and additional glass-fiber post (VP), ceramic crown restoration (Cr), ceramic crown restoration and additional glass-fiber post (CrP). Specimens were exposed to thermomechanical loading (TML: 1.2 million cycles, 1 to 50 N; 6000 thermal cycles between 5°C and 55°C for 1 min each), and subsequently linearly loaded until failure (Fmax [N]) at an angle of 135 degrees 3 mm below the incisal edge on the palatal side. Statistical tests were performed using the Kruskall-Wallis and Mann-Whitney U-Test.

Results: During dynamic loading by TML, one early failure occurred in group C, CP, and CrP. Subsequent linear loading resulted in mean fracture load values [N] of C = 483 ± 219, CP = 536 ± 281, V = 908 ± 293, VP = 775 ± 333, Cr = 549 ± 258, CrP = 593 ± 259. The Kruskal-Wallis test showed significant differences of load capacity between groups (p < 0.05). Mann-Whitney U-test revealed significantly lower maximum fracture load values of group C compared to group V (p = 0.014), after Bonferroni-Holm correction. Non-restorable root fracture was the most frequent type of failure.

Conclusion: Endodontically treated maxillary central incisors with Class III defects directly restored with composite are as loadable as indirect crown restorations. Compared to full-coverage restorations, less invasive veneers appear to be more beneficial. Additional placement of glass-fiber posts shows no positive effect.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3290/j.jad.a41635DOI Listing
September 2019

Influence of placement instruments on handling of dental composite materials.

Dent Mater 2019 02 30;35(2):e47-e52. Epub 2018 Nov 30.

UKR University Hospital Regensburg, Department of Prosthetic Dentistry, Franz-Josef-Strauß-Allee 11, 93053 Regensburg, Germany. Electronic address:

Objective: Applicability and stickiness of dental composites are influential factors for the properties of those materials and so indirectly affect function, longevity and esthetics of composite restorations in the clinic. Thus, this in vitro study aimed for the influence of different placement instruments' diameter, geometries and coatings on the handling of uncured resin composite materials.

Methods: A survey about application technique of resin composites, placement instrument diameter, geometry and coating, and application temperature was answered by 55 German dentists in private practice. Due to these data diverse composite placement instruments were used to perform tensile tests on PMMA plates with application forces of 1N and 2N (v=35mm/min) at 25 and 37°C. Following the dosing of a certain amount of the composite (nanohybrid, microhybrid) to the tip of the composite placement instrument, unplugging forces were determined after application and unplugging was performed.

Results: Unplugging forces were statistically significant different and varied between 0.27N and 1.14N. Stickiness of dental composites was dependent on the composite material itself as well as diameter, geometry and coating of the placement instruments.

Significance: Pre-clinical testing of composite materials' stickiness by unplugging forces facilitates the assessment of its handling properties.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.dental.2018.11.010DOI Listing
February 2019

In-vitro performance of CAD/CAM crowns with insufficient preparation design.

J Mech Behav Biomed Mater 2019 02 3;90:269-274. Epub 2018 Oct 3.

Department of Prosthetic Dentistry, UKR University Medical Center Regensburg, 93042 Regensburg, Germany. Electronic address:

Purpose: To compare the debonding and fracture force of different CAD/CAM composite crowns with respect to the influence of water storage (0d vs. 90d/37 °C) and types of cementation (adhesive vs. self-adhesive).

Methods: Extracted human molars were prepared with a worst-case preparation scenario providing a nonretentive design (height ~4 mm; angle ~15°) and reduced fitting (250 µm). After digitalization, 72 crowns (n = 8 per group; circular wall thickness 1.5 mm / occlusal thickness ~2.5 mm) were milled from the composites (CS, LU), one experimental composite (EX), a resin-infiltrated ceramic (VE), and a feldspar ceramic reference (VM). The crowns were adhesively bonded (Scotchbond Universal + Rely X Ultimate, 3M), and two groups (EX, VE) were additionally cemented with a self-adhesive cement (RelyX Unicem, 3M). After 90-d water storage, thermal cycling and mechanical loading (TCML) were performed. Restorations, which failed during storage or TCML, were analyzed using scanning electron microscopy, and surviving restorations were loaded to fracture. To evaluate storage effects, two materials (EX, LU) were investigated without water storage.

Results: CS (7×) and LU (2×) exhibited debonding during 90-d storage. LU (5×) debonded during TCML. Cement remained on the inner sides of the crowns in all cases. EX and VE survived storage and TCML without failure or debonding. Two specimens of VM exhibited cracks after TCML. Fracture forces varied between 720 N and 2155 N. Solely the results between VE and VM were not significantly different (p = 0.204). Debonding effects due to water storage were material dependent. Fracture forces in tendency (p > 0.117) were higher for self-adhesive cementation.

Conclusions: Debonding and stability of CAD/CAM crowns were material dependent. Water storage affected debonding, and cementation marginally influenced performance and fracture force.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.jmbbm.2018.10.002DOI Listing
February 2019

Failure loads of all-ceramic cantilever fixed dental prostheses on post-restored abutment teeth: influence of the post presence and post position.

Eur J Oral Sci 2018 12 1;126(6):526-532. Epub 2018 Oct 1.

Department of Prosthodontics, Geriatric Dentistry and Craniomandibular Disorders, Humboldt-Universität zu Berlin, Berlin Institute of Health, Charité - Universitätsmedizin Berlin, Berlin, Germany.

The influence of a fiber post-restored abutment tooth on the load capability of a three-unit zirconia framework cantilever fixed dental prosthesis (cFDP) was evaluated after simulated clinical function. Human lower sound premolars (n = 64) were distributed, in equal numbers, to four experimental groups: two vital abutment teeth (group I; control); mesial abutment tooth post-restored (group II); distal abutment tooth post-restored (group III); and mesial and distal abutment teeth post-restored (group IV). All specimens received an adhesively luted three-unit cFDP of veneered zirconia. Simulated clinical function was performed by two subsequent sequences of thermal-cycling (2 × 3,000 cycles) and mechanical loading (1.2 × 10 load cycles from 0 to 50 N) (TCML). Four specimens failed during TCML (one in each of groups I and IV and two in group II). The maximum load capability ranged from 365 to 538 N and was not significantly different between groups. Specimens with post-restored abutments failed mainly because of abutment tooth fracture of the distal abutment. The presence or position of post-restored abutment teeth has no significant impact on load capability of all-ceramic three-unit cFDPs. The risk of tooth fracture of the distal abutment teeth of a cFDP was significantly increased when one abutment tooth, irrespective of its position, was post-and-core restored.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1111/eos.12573DOI Listing
December 2018

performance and fracture resistance of novel CAD/CAM ceramic molar crowns loaded on implants and human teeth.

J Adv Prosthodont 2018 Aug 17;10(4):300-307. Epub 2018 Aug 17.

Department of Prosthetic Dentistry, UKR University Hospital Regensburg, Regensburg, Germany.

Purpose: To investigate the fatigue and fracture resistance of computer-aided design and computer-aided manufacturing (CAD/CAM) ceramic molar crowns on dental implants and human teeth.

Materials And Methods: Molar crowns (n=48; n=8/group) were fabricated of a lithium-disilicate-strengthened lithium aluminosilicate glass ceramic (N). Surfaces were polished (P) or glazed (G). Crowns were tested on human teeth (T) and implant-abutment analogues (I) simulating a chairside (C, crown bonded to abutment) or labside (L, screw channel) procedure for implant groups. Polished/glazed lithium disilicate (E) crowns (n=16) served as reference. Combined thermal cycling and mechanical loading (TC: 3000×5℃/3000×55℃; ML: 1.2×10 cycles, 50 N) with antagonistic human molars (groups T) and steatite spheres (groups I) was performed under a chewing simulator. TCML crowns were then analyzed for failures (optical microscopy, SEM) and fracture force was determined. Data were statistically analyzed (Kolmogorow-Smirnov, one-way-ANOVA, post-hoc Bonferroni, α=.05).

Results: All crowns survived TCML and showed small traces of wear. In human teeth groups, fracture forces of N crowns varied between 1214±293 N (NPT) and 1324±498 N (NGT), differing significantly (≤.003) from the polished reference EPT (2044±302 N). Fracture forces in implant groups varied between 934±154 N (NGI_L) and 1782±153 N (NPI_C), providing higher values for the respective chairside crowns. Differences between polishing and glazing were not significant (≥.066) between crowns of identical materials and abutment support.

Conclusion: Fracture resistance was influenced by the ceramic material, and partly by the tooth or implant situation and the clinical procedure (chairside/labside). Type of surface finish (polishing/glazing) had no significant influence. Clinical survival of the new glass ceramic may be comparable to lithium disilicate.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.4047/jap.2018.10.4.300DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6104500PMC
August 2018

The error of tensile strength tests and an approach for improvement.

J Mech Behav Biomed Mater 2018 11 3;87:138-142. Epub 2018 Jul 3.

Department of Prosthodontics, Regensburg University Medical Center, 93042 Regensburg, Germany.

Objectives: The deviation and spread of values measured by tensile strength tests should be significantly reduced by optimized axially pull-off-device.

Material And Methods: Factors like geometry, roughness, surface texture and fit of the specimens, the luting procedure (mixing ratio, compacting pressure) were standardized and the precision of the axially load transmission during the tensile force application optimized. Copings of CoCr-alloy were luted using a provisional zinc-oxide eugenol and a glass-ionomer cement (n = 20 per group each) on 4°, respectively 8° titanium implant abutment analogs. 24 h after luting the copings were pulled off with the improved (IPD) and the previous non improved device (NIPD). Means, std. dev. and t-tests were calculated.

Results: The stress- strain curves produced by the IPD showed a clear and linear relationship between stress and strain. The curves of the NIPD were ragged and chaotic. For both luting agents the means of the retentive force were considerable higher (p > 0.000) with IPD. However, the standard deviation was unimproved for the zinc oxide eugenol cement: IPD: 27%; NIPD: 27%, but significantly improved with glass ionomer: IPD: 16%, NIPD: 28%.

Conclusion: The results from luting agents, which react like a solid body, may benefit from the optimized pull-off-device. Despite the fact that many factors in this investigation have been controlled, unknown flow characteristics of non-Newtonian-fluids like luting agents may have a considerable influence on the standard deviation of pull-off tests.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.jmbbm.2018.07.003DOI Listing
November 2018

Investigation of Clinical and Laboratory Wear in Locator-Supported, Implant-Retained Overdentures.

Int J Prosthodont 2018 Jul/Aug;31(4):334-337

Purpose: To investigate the mechanical properties and wear of nylon inserts and abutments in Locator-retained, implant-supported overdentures (L-IODs).

Materials And Methods: Clinical wear of inserts and abutments was qualitatively rated in a group of 16 patients with L-IODs. The inserts were also subjected to microscopic analysis, differential scanning calorimetry (DSC), and thermal gravimetric analysis (TGA).

Results: Wear was identified in almost all inserts and abutments. These results were corroborated by DSC and TGA analyses, which showed significant mechanical deterioration of the inserts.

Conclusion: Nylon inserts and Locator abutments show relevant signs of deterioration in clinical use, indicating that regular maintenance is an issue that should be addressed with the patients prior to treatment.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.11607/ijp.5706DOI Listing
November 2018
-->