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PURPOSE To investigate the discoloration and surface properties of four CAD/CAM composite resins provoked by a variety of food solutions and cigarette smoke. MATERIALS AND METHODS A total of 74 specimens (N = 370) were prepared per material (Brilliant Crios [Coltene], CeraSmart [GC], Lava Ultimate [3M Espe], Shofu Block HC [Shofu], and SonicFill 2 [Kerr]). Discoloration (ΔE) was investigated with a spectrophotometer. Measurements were taken before immersion in the storage media for 2 weeks (carrot juice, curry, cigarette smoke, red wine, energy drink, and distilled water), immediately after immersion, and after manual polishing of the specimens following immersion. The mean surface roughness (Ra) was measured using a profilometer. Qualitative surface observation was performed with scanning electron microscopy (SEM). Data were analyzed using Kolmogorov-Smirnov, Mann-Whitney U, and one-way analysis of variance with Tukey post hoc tests. RESULTS The highest influence on ΔE after immersion was observed by the storage medium (ηP. = 0.878, P < .001), followed by the interaction between storage medium and material (ηP. = 0.770, P < .001) and the material (ηP. = 0.306, P < .001). For ΔE after polishing, the highest influence was indicated by the interaction of material and medium (ηP. = 0.554, P < .001), followed by the medium (ηP. = 0.244, P < .001) and the material (ηP. = 0.196, P < .001). Immersion in carrot juice led to the highest color change (ΔE: 8.0 to 10.4), whereas the lowest values were recorded in distilled water (ΔE: 2.0 to 2.4). Carrot juice and the energy drink provoked the highest Ra values (0.120 to 0.355 μm). SEM pictures indicated a loss of the organic matrix after manual polishing. CONCLUSION The different materials reacted dissimilarly in the various storage media in terms of discoloration. Surface roughness increased after immersion and polishing. Neither discoloration nor surface roughness could be reset to default by manual polishing.

Investigating the impact of different pretreatment methods, attachment materials and aging regimens on shear bond strength (SBS) between zirconia and indirectly bonded brackets using CAD/CAM transfer trays.Zirconia substrates were conditioned with silica coated alumina (CoJet) and a) Clearfil Ceramic Primer Plus (CF), b) RelyX Ceramic Primer (RXP), c) Futurabond U (FU). Brackets were virtually placed, transfer tray designed (OnyxCeph) and 3D-printed for indirect bonding with a) Transbond LV (TBL), b) Nexus NX3 (NX3), c) Maximum Cure (MC). SBS testing was performed with a universal testing machine after 24 h, 500 thermal cycles, 90 d. Directly bonded brackets to human enamel using Transbond XT Adhesive served as control. The adhesive remnant index (ARI) was evaluated. Data was analyzed with Shapiro-Wilk, Kruskal-Wallis and Dunn's post-hoc test with Bonferroni correction, ChiSBS ranged from 0.1 to 15.5 MPa and were influenced mostly by the attachment material. NX3 generally showed the highest values (9.5-15.8 MPa). Initially RXP/TBL and FU/TBL presented the lowest values (4.3/4.8 MPa). Aging regimens reduced SBS of MC irrespective of pretreatment, after 90 d values ranged from 0.1 to 0.9 MPa. ARI 1 was predominant in all MC groups and FU/NX3, 2 and 3 in the other groups. Weibull moduli ranged between 0.15 (MC/RXP/500 TC) and 6.24 (NX3/RXP/500 TC).MC seems not to be suitable for indirect bonding using CAD/CAM transfer trays to zirconia. NX3 showed similar SBS values compared to the control, TBL lower.

Statement of problem Polyphenylene sulfone (PPSU) is a thermoplastic that can be processed using 3-dimensional printing. PPSU is new to dentistry, and scientific data on its properties are lacking. Purpose The purpose of this in vitro study was to test the surface properties and the tensile bond strength (TBS) between PPSU and a veneering composite resin in comparison with a polyetheretherketone (PEEK). Material and methods Gehr PPSU (PPSU-B1), Radel R-5000 NT (PPSU-B2), and Juvora Dental Disc (PEEK-CG) substrates were cut from bulk material, while FIL-A-GEHR PPSU (PPSU-3D) was 3-dimensionally printed (N=504, n=126/material). TBS to veneering composite resin (CeramageUp) was tested initially and after 5000 and 10 000 thermocycles, and fracture types were analyzed. Surface free energy (SFE) and surface roughness (Ra) were determined after pretreatment with aluminum oxide (Al2O3) of different grain sizes (50 and 110 μm) applied with different pressures (0.1, 0.2, 0.4 MPa), silicon dioxide (SiO2)-coated Al2O3 (0.28 MPa), sulfuric acid, or polished. Qualitative surface characterization was performed by using a scanning electron microscope (SEM). One-way ANOVA, the Kruskal-Wallis, Mann-Whitney U, and the Spearman correlation tests were computed (α=.05). Results PPSU-3D and PEEK-CG presented higher TBS results than PPSU-B1 and PPSU-B2. Initial TBS values were higher than after 10 000 thermocycles. Adhesive fractures between substrate and veneering composite resin occurred most frequently. With a few exceptions, PEEK-CG presented higher SFE values than all other materials within a pretreatment group, while PPSU-3D and PEEK-CG showed consistently high Ra values. An increase in pressure and particle size increased SFE and Ra. Conclusions FFF-printed PPSU-3D showed similar TBS values with the veneering composite resin to the more established PEEK. Pretreatment methods devised for PEEK represent valid strategies for increasing both the SFE and Ra of the high-performance polymer PPSU.

Objectives To investigate the chemical (degree of conversion (DC)) and mechanical properties (Martens hardness (HM), elastic indentation modulus (EIT), and biaxial flexural strength (BFS)) of four dual-polymerizing resin composite core build-up materials after light- and self-polymerization. Materials and methods Round specimens with a diameter of 12 mm and a thickness of 1.5 mm were manufactured from CLEARFIL DC CORE PLUS (CLE; Kuraray), core·X flow (COR; Dentsply Sirona), MultiCore Flow (MUL; Ivoclar Vivadent), and Rebilda DC (REB; VOCO) (N = 96, n = 24/material). Half of the specimens were light-polymerized (Elipar DeepCure-S, 3 M), while the other half cured by self-polymerization (n = 12/group). Immediately after fabrication, the DC, HM, EIT, and BFS were determined. Data was analyzed using Kolmogorov–Smirnov, Mann–Whitney U, and Kruskal–Wallis tests, Spearman’s correlation, and Weibull statistics (p Results Light-polymerization either led to similar EIT (MUL; p = 0.119) and BFS (MUL and REB; p = 0.094–0.326) values or higher DC, HM, EIT, and BFS results (all other groups; p p p p = 0.020) and Weibull modulus after light-polymerization. Positive correlations between all four tested parameters (R = 0.527–0.963, p Conclusions For the tested resin composite core build-up materials, light-polymerization led to similar or superior values for the degree of conversion, Martens hardness, elastic indentation modulus, and biaxial flexural strength than observed after self-polymerization. Among the tested materials, COR should represent the resin composite core build-up material of choice due to its high chemical (degree of conversion) and mechanical (Martens hardness, elastic indentation modulus, and biaxial flexural strength) properties and its high reliability after light-polymerization. The examined chemical and mechanical properties showed a positive correlation. Clinical relevance The chemical and mechanical performance of dual-polymerizing resin composite core build-up materials is significantly affected by the chosen polymerization mode.

The present investigation tested the effect of cleaning methods and adhesives on the tensile bond strength (TBS) of a resin-based composite luted to a temporary 3D printed resin. Substrates (n= 360) were printed using a Rapidshape D20II and cleaned with a butyldiglycol-based solution, isopropanol, or by centrifugation. Specimens were air-abraded with Al2O3 (mean particle size 50 µm) at 0.1 MPa followed by pretreatment (n = 30/subgroup) with: (1) Clearfil Ceramic Primer (CCP); (2) Clearfil Universal Bond (CUB); (3) Scotchbond Universal Plus (SUP) or 4. Visio.link (VL) and luted to PanaviaV5. TBS (n = 15/subgroup) was measured initially (24 h at 37 °C water) or after thermal cycling (10,000×, 5/55 °C). The degree of conversion (DC) for each cleaning method was determined prior and after air-abrasion. Univariate ANOVA followed by post-hoc Scheffé test was computed (p < 0.05). Using Ciba-Geigy tables and chi-square, failure types were analyzed. The DC values were >85% after all cleaning methods, with centrifugation showing the lowest. CCP pretreatment exhibited the lowest TBS values, with predominantly adhesive failures. The combination of CCP and centrifugation increased the TBS values (p < 0.001) compared to the chemical cleaning. CUB, SUP, and VL, regardless of cleaning, can increase the bond strength between the 3D printed resin and the conventional luting resin.

Objectives A variety of dental materials are available for the fabrication of telescopic crowns. The aim was to investigate the impact of material combinations and removal and insertion cycles on their retention forces. Materials and methods CAD/CAM-fabricated cobalt–chromium–molybdenum (CoCr) and zirconia (ZrO2) primary crowns were combined with polyetheretherketone (PEEK), polyetherketoneketone (PEKK), CoCr, and ZrO2 secondary crowns (four combinations included PEEK/PEKK secondary crowns in a thickness of 0.5 mm bonded to the CoCr tertiary construction), resulting in 12 different material combinations: CoCr–PEEK; CoCr–PEKK; CoCr–ZrO2; CoCr–CoCr; CoCr–PEEK 0.5; CoCr–PEKK 0.5; ZrO2–PEEK; ZrO2–PEKK; ZrO2–ZrO2, ZrO2–CoCr; ZrO2–PEEK 0.5; and ZrO2–PEKK 0.5 (n = 15 pairings per material combination). Pull-off tests were performed with a universal testing machine initially and after 500, 5000, and 10,000 removal and insertion cycles in a mastication simulator. Descriptive statistics with the Kolmogorov–Smirnov, Kruskal–Wallis, and Mann–Whitney U tests were computed (α = 0.05). Results The tested parameters, material combination, and removal and insertion cycles had significant impact on the retention force values (p < 0.001). An increase in removal and insertion cycles was associated with a decrease in retention forces within CoCr and ZrO2 secondary crowns, regardless of the primary crown material. In contrast, PEEK and PEKK secondary crowns presented higher retention load values after 10,000 cycles than initially. Conclusion Different material combinations behaved differently after simulated removal and insertion regimens. This difference should be considered during treatment planning. Clinical relevance Telescopic crown systems should be made of materials with predictable retention forces that do not deteriorate with time. The implementation of new materials and technologies facilitates reproducibility and time-saving fabrication.

To investigate the bending moment of implants restored with a directly screwed single-unit fixed dental prosthesis (FDP) compared to implants restored with an FDP polymerized to a titanium base before and after thermomechanical aging.A total of 240 implants (120 with and 120 without a titanium base) were restored with FDPs manufactured from conventionally sintered 3Y-TZP, 5Y-TZP, 4Y-TZP, and CoCrMo, as well as high-speed sintered 4Y-TZP. Half of the specimens per subgroup were aged using chewing simulation combined with thermocycling (1,200,000 cycles at 50 N; 6,000 cycles at 5°C to 55°C). Initial and aged fracture load were measured. The bending moment was calculated and subjected to statistical analysis (Kolmogorov-Smirnov test, one-way ANOVA followed by post hoc Scheffé, t, and chi-square tests; P.05). Failure types were analyzed.Implants without a titanium base showed higher bending moments for all initially tested zirconia groups compared to implants with a titanium base. The highest initial values were observed for 4Y-TZP FDPs regardless of implant type. High-speed sintered FDPs demonstrated higher initial bending moments compared to conventionally sintered FDPs. Artificial aging led to a decrease of the bending moment in most of the subgroups. After aging, no differences were found within the restoration materials, sintering protocols, or implant types. Implant deformation occurred mainly with directly screwed FDPs, whereas FDP mobility was predominantly observed among implants with a titanium base. FDP fractures were mainly observed for 5Y-TZP.Both implant types exhibited similar values after aging. Thus, implants without a titanium base seem to show equally sufficient stability for clinical applications with all tested materials.

Objective The study aims to investigate the shear bond strength (SBS) between silicate ceramic restorations and ceramic brackets after different pretreatments and aging methods. Material and methods Leucite (LEU) and lithium disilicate (LiSi) specimens were pretreated with (i) 4% hydrofluoric acid + silane (HF), (ii) Monobond Etch&Prime (MEP), (iii) silicatization + silane (CoJet), and (iv) SiC grinder + silane (SiC). Molars etched (phosphoric acid) and conditioned acted as comparison group. SBS was measured after 24 h (distilled water, 37 °C), 500 × thermocycling (5/55 °C), and 90 days (distilled water, 37 °C). Data was analyzed using Shapiro–Wilk, Kruskal–Wallis with Dunn’s post hoc test and Bonferroni correction, Mann–Whitney U, and Chi2 test (p Results LEU pretreated with MEP showed lower SBS than pretreated with HF, CoJet, or SiC. LiSi pretreated with MEP resulted in lower initial SBS than pretreated with HF or SiC. After thermocycling, pretreatment using MEP led to lower SBS than with CoJet. Within LiSi group, after 90 days, the pretreatment using SiC resulted in lowest SBS values. After HF and MEP pretreatment, LEU showed lower initial SBS than LiSi. After 90 days of water storage, within specimens pretreated using CoJet or SiC showed LEU higher SBS than LiSi. Enamel presented higher or comparable SBS values to LEU and LiSi. With exception of MEP pretreatment, ARI 3 was predominantly observed, regardless the substrate, pretreatment, and aging level. Conclusions MEP pretreatment presented the lowest SBS values, regardless the silicate ceramic and aging level. Further research is necessary. Clinical relevance There is no need for intraoral application of HF for orthodontic treatment.

PURPOSE To investigate the influence of different cleaning methods for additively manufactured fixed dental prostheses (FDPs) for long-term temporary use on the degree of conversion (DC), surface roughness, Martens parameters, and biaxial flexural strength. MATERIALS AND METHODS A total of 180 specimens per material (3Delta Etemp, DeltaMed; Freeprint Temp, Detax; Temp PRINT, GC Europe; Temp CB N = 180) were additively manufactured (D20 II, Rapid Shape) and subsequently cleaned by different methods: by rinsing for 5 minutes in acetone (Hofer Chemie; 99.5%); butyl glycol (Algin Chemie; 100%); ethanol (Otto Fischar; 96%); isopropanol (SAV LP; 100%); Yellow Magic 7 (Bradley Systems; 100%); or by applying centrifugal force for 4 minutes (n = 30 per subgroup). After postpolymerization (Otoflash G171, NK-Optik), the DC was measured using Raman spectroscopy, and the surface roughness, as well as the Martens parameters, were recorded. Biaxial flexural strength was investigated after artificial aging (thermocycling for 10,000 cycles). Data were statistically analyzed (Kolmogorov-Smirnov, Kruskal-Wallis, and Mann-Whitney U tests, and Pearson correlation coefficient). RESULTS The highest DC was recorded after the use of butyl glycol or isopropyl (P < .001 to P = .047). The highest surface roughness was measured after the use of butyl glycol (P < .001 to P = .024). The use of centrifugal force or Yellow Magic resulted in the highest Martens parameter values (P < .001 to P = .036) and the highest biaxial flexural strength (P < .001 to P = .013), while acetone and butyl glycol led to the lowest values. CONCLUSION The use of centrifugal force and Yellow Magic resulted in the highest Martens parameter values and the highest biaxial flexural strength. Concerning Yellow Magic, no negative effect on the mechanical properties was observed. The 3Delta Etemp material especially was prone to degradation after chemical cleaning.

Purpose To investigate the impact of high-speed sintering on the accuracy (trueness and reproducibility) and fit of 4Y-TZP full-coverage single-unit fixed dental prostheses (FDPs) and three-unit FDPs. Materials and methods Single-unit FDPs, conventional three-unit FDPs, and cantilever three-unit FDPs (N = 108; n = 12 per subgroup) were fabricated from: (1) high-speed sintered (1,580°C, about 20 minutes) multi-layer 4Y-TZP (Zolid RS, Amann Girrbach; ZMLH group), as well as two conventionally sintered (1,450°C, about 10 hours) materials: (2) multi-layer 4Y-TZP (Zolid Gen-X, Amann Girrbach; ZMLC group) and (3) monochrome 4Y-TZP (Ceramill Zolid HT+ PS, Amann Girrbach; ZMOC group). All specimens were scanned. Trueness, reproducibility, and fit were measured with 3D analysis software. For data analysis, Kolmogorov-Smirnov, Kruskal-Wallis, and Mann-Whitney U tests were performed (α = .05). Results Three-unit FDPs made from ZMLH presented a deterioration of accuracy in comparison to ZMLC (P ≤ .001 to .008). The influence of highspeed sintering on marginal and general fit was not clinically relevant (P = .154 to .877). Conclusion High-speed sintering influenced the accuracy of 4Y-TZP full-coverage single-unit and three-unit FDPs. However, no clinically relevant impact on fit was observed.

Objectives To investigate the initial bacterial adhesion on 3D-printed splint materials in relation to their surface properties. Materials and methods Specimens of five printable splint resins (SHERAprint-ortho plus UV, NextDent Ortho Rigid, LuxaPrint Ortho Plus, V-Print Splint, KeySplint Soft), one polymethylmethacrylate (PMMA) block for subtractive manufacturing (Astron CLEARsplint Disc), two conventional powder/liquid PMMA materials (FuturaGen, Astron CLEARsplint), and one polyethylene terephthalate glycol (PETG) thermoplastic sheet for vacuum forming (Erkodur Thermoforming Foil) were produced and finished. Surface roughness Ra was determined via contact profilometry. Surface morphology was examined under a scanning electron microscope. Multi-species bacterial biofilms were grown on entire splints. Total biofilm mass and viable bacterial counts (CFU/ml) within the biofilms were determined. Statistical analyses were performed with a one-way ANOVA, Tukey’s post hoc test, and Pearson’s test (p Results Astron CLEARsplint and KeySplint Soft specimens showed the highest surface roughness. The mean total biofilm mass on KeySplint Soft splints was higher compared to all other materials (p Ra, biofilm mass, and CFU/ml. A positive correlation was found between Ra and CFU/ml (r = 0.69, p = 0.04). Conclusions The 3D-printed splints showed overall favorable results regarding surface roughness and bacterial adhesion. Thermoplastic materials seem to display a higher surface roughness, making them more susceptible to microbial adhesion. Clinical relevance The development of caries and gingivitis in patients with oral appliances may be affected by the type of material.

To investigate the water sorption (wSpecimens (N = 540) were 3D-printed (NextDent Denture 3D+ (DEN), Fotodent Denture (FOT), Freeprint Denture (FRE), V-Print dentbase (VPR)), cut (Ivotion Base (IVO)) and molded (PalaXpress (PAL)) in three geometries. WAlthough 3D-printed denture base resins showed promising results with regard to the observed DC and FS, only FOT and FRE surpassed the threshold values defined by the ISO norms.

Objectives The influence of different cleaning methods, air-abrasion parameters, and aging on shear bond strength (SBS) and tensile bond strength (TBS) of 3D resin luted to composite resin. Materials and methods Nine hundred resin substrates were 3D printed (D20II, Rapid Shape) and cleaned with either isopropanol (ISO), butyldiglycol-based solution (BUT), or centrifugation (CEN). After 24-h storage in 37 °C water, specimens were air-abraded (mean particle size 50 µm; n = 60) with either alumina at 0.1 MPa (AL0.1) or 0.4 MPa (AL0.4) and glass pearls at 0.1 MPa (GP0.1) and 0.4 MPa (GP0.4) or conditioned with visio.link (control) and luted with PanaviaV5. Initially (24 h, 37 °C water storage) or after aging (10,000 thermal cycles), SBS and TBS were measured, and fracture types were examined. Surface free energy (SFE) and roughness (Ra) were determined after air-abrasion. Kolmogorov–Smirnov, Kruskal–Wallis H, Mann–Whitney U, chi-square, and partial eta-squared were computed. Results SBS measurements presented higher values than TBS (p p p p Conclusions Pretreatment with AL0.4 and the control group mainly presented the highest bond strength values. Thermocycling had a positive effect on the bond strength. Clinical relevance According to this study, 3D-printed restorations should be pretreated with AL0.4 or with visio.link before adhesive luting, regardless of their cleaning.

Objective To investigate the degree of conversion (DC), Martens hardness (HM), elastic indentation modulus (EIT), and biaxial flexural strength (BFS) of six dual-polymerizing resin composite luting materials initially and after 2 and 7 days of aging. Materials and methods Specimens fabricated from Bifix QM (BIF; VOCO), Calibra Ceram (CAL; Dentsply Sirona), DuoCem (DUO; Coltène/Whaledent), G-CEM LinkForce (GCE; GC Europe), PANAVIA V5 (PAN; Kuraray Europe), and Variolink Esthetic DC (VAR; Ivoclar Vivadent) (n = 12 per material) were light-polymerized through 1 mm thick discs (Celtra Duo, Dentsply Sirona). DC, HM, and EIT were recorded directly after fabrication, and after 2 and 7 days of aging. As a final test, BFS was measured. Univariate ANOVAs, Kruskal–Wallis, Mann–Whitney U, Friedman, and Wilcoxon tests, and Weibull modulus were computed (p Results While CAL presented low DC, HM, EIT, and BFS values, DUO and BIF showed high results. Highest Weibull moduli were observed for VAR and DUO. DC and Martens parameters increased between the initial measurement and 2 days of aging, while aging for 7 days provided no further improvement. Conclusions The choice of dual-polymerizing resin composite luting material plays an important role regarding chemical and mechanical properties, especially with patients sensitive to toxicological issues. DUO may be recommended for bonding fixed dental prostheses, as it demonstrated significantly highest and reliable results regarding DC, HM, and BFS. As DC and HM showed an increase in the first 48 h, it may be assumed that the polymerization reaction is not completed directly after initial polymerization, which is of practical importance to dentists and patients. Clinical relevance The chemical and mechanical properties of dual-polymerizing resin composite luting materials influence the overall stability and long-term performance of the restoration.

Statement of problem Additive manufacturing has been proposed for the fabrication of occlusal devices. However, information about the mechanical properties of additively manufactured devices is lacking. Purpose The purpose of this in vitro study was to evaluate the influence of the postpolymerization unit and artificial aging on the Martens hardness (HM) and indentation modulus (EIT) of different 3D-printed materials in comparison with a conventionally milled material. Material and methods Thirty disks (20 mm in diameter and 5 mm in thickness) were additively manufactured (D20 II, Rapidshape & Form 2) for each 3D-printed material (NextDent Splint, Formlabs Dental LT Clear, and Freeprint Splint). As a control, 10 disks of the same thickness were cut from a conventionally milled material (Temp Premium). Each specimen was measured for HM and EIT (ZHU 0,2) after fabrication. The specimens were stored in water at 37 °C and measured again after 2 and 4 weeks. The data were analyzed statistically by using the Kruskal-Wallis, Mann-Whitney U, and Wilcoxon tests (adjusted by Bonferroni correction α=.05/27=.002). Results The highest influence on HM parameters was shown by artificial aging (partial eta squared: HM: ηP2=0.840, EIT: ηP2=0.855, P Conclusions HM parameters of additively manufactured occlusal devices depend on postpolymerization strategy. Otoflash and Printbox result in higher HM and EIT values. The 3D-printed materials are more prone to artificial aging than the control group, which brings into question their long-term service.

To investigate the impact of different cleaning methods on the fracture load and two-body wear of additively manufactured three-unit fixed dental prostheses (FDP) for long-term temporary use, compared to the respective outcomes of milled provisional PMMA FDPs. Shape congruent three-unit FDPs were 3D printed using three different resin-based materials [FPT, GCT, NMF] or milled [TEL] (N = 48, n = 16 per group). After printing, the FDPs were cleaned using: Isopropanol (ISO), Yellow Magic 7 (YEL), or centrifugal force (CEN). Chewing simulation was carried out with a vertical load of 50 N (480,000 × 5 °C/55 °C). Two-body wear and fracture load were measured. Data were analyzed using global univariate ANOVA with partial eta squared, Kruskal-Wallis H, Mann-Whitney U, and Spearman’s rho test (p < 0.05). TEL showed less wear resistance than FPT (p = 0.001) for all cleaning methods tested. Concerning vertical material loss, NMF and GCT were in the same range of value (p = 0.419–0.997), except within FDPs cleaned in ISO (p = 0.021). FPT showed no impact of cleaning method on wear resistance (p = 0.219–0.692). TEL (p < 0.001) showed the highest and FPT (p < 0.001) the lowest fracture load. Regarding the cleaning methods, specimens treated with ISO showed lower fracture load than specimens cleaned with CEN (p = 0.044) or YEL (p = 0.036). The material selection and the cleaning method can have an impact on two-body wear and fracture load results. Printed restorations showed superior two-body wear resistance compared to milled FDPs but lower fracture load values. Regarding cleaning methods, ISO showed a negative effect on fracture load compared to the other methods tested.

New materials and precise manufacturing processes allow for new processes in the veneering and production of fixed dental prostheses. However, data on the bond strength of computer-aided design and computer-aided manufacturing (CAD-CAM) and conventional veneering materials to substrates bonded with different composite resins are lacking.The purpose of this in vitro study was to investigate the shear bond strength (SBS) of 2 CAD-CAM, Lava Ultimate (LVU) and VITABLOCS Mark II (VMII), and 3 conventional veneering materials (VM9, VM13, VTI) to 3 different substrates: zirconia (ZIR), cobalt-chromium (CC), and titanium (TIT).Substrates and veneering cylinders were manufactured and bonded by using 3 different composite resins, RelyX Unicem (RUL), RelyX Ultimate (RXU), and Sinfony (SIN), after various pretreatments (n=18). Half the specimens underwent artificial aging before SBS testing, and failure types were analyzed. Univariate 1-way ANOVA, Kruskal-Wallis, and Mann-Whitney U were computed (α=.05).CC substrates bonded with RUL showed the highest SBS (P=.007). ZIR substrates bonded with RXU presented higher SBS than TIT substrates (P=.007). ZIR substrates bonded with SIN showed higher SBS than CC substrates (P.001). SIN veneered groups showed lower SBS than that observed for VM9/13/VTI (P.001). SIN veneered LVU and VMII substrates presented lower SBS (P.001). Thermocycling led to a reduction in SBS for most groups (P=.001-.022). SIN veneered substrates and RXU veneered VMII substrates resulted in lower SBS than that seen for VM9/13/VTI and veneered ZIR substrates bonded with SIN or RXU (P.001). Adhesive failures were most common.While RUL is capable of forming a stable bond to CC without pretreatment, ZIR substrates achieve higher SBS after conditioning with an MDP-containing primer when using RXU or SIN than that seen for RUL. Pretreated CAD-CAM-veneered ZIR substrates bonded with SIN or RXU led to similar SBS results to those observed for conventional veneers, while veneering with SIN resulted in lower SBS.

To investigate the degree of conversion (DC), Martens hardness (HM), elastic indentation modulus (EIT), and flexural strength (FS) of veneering resin composites (SR Nexco Paste (NP), Ceramage Incisal (CI), Gradia Plus (GP); n=60/group) cured with different polymerization devices (bre.Lux Power Unit, Labolight DUO, Otoflash G171, LC-3DPrint Box, PCU LED; n=12/subgroup) after storage. Otoflash G171 and Labolight DUO showed increased DC/HM/EIT. CI presented the lowest DC and highest HM/EIT. NP showed the highest DC and lowest HM/EIT. Within Otoflash G171, Laboligth DUO and PCU LED, highest FS was observed for CI. Storage did not affect DC/HM/EIT for specimens cured with Otoflash G171 or Labolight DUO. With storage not showing an influence on the tested parameters for polymerization devices that otherwise presented superior results, increased storage time cannot be recommended. For the tested resin composites, this study observed a high/low degree of conversion to coincide with respectively low/high amounts of fillers/mechanical properties.

Statement of problem Yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) materials of different formulations (3Y-TZP, 4Y-TZP, and 5Y-TZP) can be colored by using color liquids. However, practically and clinically relevant factors such as modifications of sintering protocols and hydrothermal aging might affect the extent of light transmittance and flexural strength of zirconia materials of different formulations; studies on these outcomes, however, are lacking. Purpose The purpose of this in vitro study was to test the impact of hydrothermal aging on the light transmittance and flexural strength of colored zirconia materials compared with a lithium-disilicate (LiSi2) ceramic. Material and methods A total of 210 specimens were prepared from 3Y-TZP0.25 (n=30), 3Y-TZP0.05 (n=30), 5Y-TZP (n=30), 4Y-TZP (n=60), pre4Y-TZP (preshaded, n=30), and LiSi2 (n=30). All specimens, except for pre4Y-TZP and LiSi2, were manually colored, predried, and either conventionally sintered at 1450 °C (3Y-TZP0.25, 3Y-TZP0.05, 5Y-TZP, and half of 4Y-TZP) or high-speed sintered at 1580 °C (other half of 4Y-TZP and pre4Y-TZP). Light transmittance was measured initially and after 2, 5, 10, 20, 40, and 160 hours of hydrothermal aging (134 °C, 0.2 MPa). Biaxial flexural strength was tested initially and after 160 hours of hydrothermal aging (n=15). The Kolmogorov-Smirnov test, multivariate analysis, and 1-way ANOVA with the Tukey HSD post hoc test, the t test, and linear mixed models were calculated (α=.05). Results LiSi2 showed the highest translucency, followed by 5Y-TZP, 4Y-TZP, pre4Y-TZPspeed, 3Y-TZP0.05, and 3Y-TZP0.25. 4Y-TZPspeed was most opaque and matte. The decrease in translucency related to aging hours was higher for LiS2 and conventional sintered zirconia materials than for 4Y-TZPspeed and pre4Y-TZPspeed. Initially, 3Y-TZP0.25 had the highest flexural strength, followed by 3Y-TZP0.05, 4Y-TZP, and pre4Y-TZPspeed. pre4Y-TZPspeed was comparable with 4Y-TZPspeed but significantly higher than 5Y-TZP. LiSi2 had the lowest biaxial flexural strength. Hydrothermal aging increased biaxial flexural strength for 3Y-TZP0.25 and 3Y-TZP0.05 (P Conclusions Manually colored, conventionally sintered 4Y-TZP was resistant to hydrothermal aging regarding flexural strength. High-speed sintering inhibited color development for manually colored 4Y-TZP but did not affect the resistance to hydrothermal aging. The findings were reversed for industrially preshaded 4Y-TZP.

Objectives To evaluate and compare fracture resistance, translucency, and color reproducibility, as well as the effect of aging on the fracture load and color stability of novel monolithic CAD/CAM ceramics. Materials and methods One hundred crowns of uniform thickness were milled from five ceramic blocks (n = 20): partially crystallized lithium disilicate (PLD) and fully crystallized lithium disilicate (FLD), lithium metasilicate (LMS), 4Y-TZP (SMZ), and 5Y-TZP (UMZ) monolithic zirconia. PLD crowns were glazed, LMS was fired, and FLD was polished. SMZ and UMZ crowns were sintered and polished. Crowns were adhesively cemented to epoxy dies. Half of the crowns (n = 10) were subjected to 1.200.000 load cycles with thermal cycling. Color space values L, a, b defined by the Commission Internationale de l´Eclairage (CIELAB) were measured before and after aging, and (∆E) was calculated. Both aged and non-aged specimens were loaded until fracture in a universal testing machine and the fracture load was recorded. X-ray diffraction (XRD) and scanning electron microscope (SEM) fractographic analysis were carried out on fractured fragments of representative samples. For translucency and color reproducibility, 50 rectangular-shaped specimens were fabricated and processed as described previously. Color values were measured over black and white backgrounds, and the translucency parameter (TP) was computed. Using the shade verification mode, (∆E) to shade A3 was calculated. Data were statistically analyzed using one-way and two-way ANOVA, and t-test. Results Aging did not affect fracture resistance significantly (p > 0.05). The highest mean fracture load was obtained for the SMZ and UMZ. A significant color change was observed after aging in all groups. The highest TP was noted for FLD. SMZ and UMZ had the best shade match. Conclusions Zirconia showed higher fracture resistance and color stability than lithium silicate ceramics. Lithium silicate ceramics were more translucent. The experimental FLD demonstrated high translucency. Clinical relevance Tested ceramics showed sufficient stability to withstand masticatory forces. Characterization of final restorations might be mandatory for better color match.

To report the long-term clinical survival and failure rates of single-tooth restorations made of pressable lithium disilicate ceramics (LSTwenty-one patients (12 female, nine male) were treated with 436 minimally invasive single-tooth restorations made of 274 pressed LSThe 274 LSPressed LSDespite the limitations of the clinical observations, single-tooth restorations of both materials can be recommended for permanent use in patients with severe tooth wear.

Statement of problem The selection of an appropriate restorative material based on fracture behavior is important for the marginal integrity of a dental restoration. For computer-aided design and computer-aided manufacturing (CAD-CAM) restorative materials, information regarding their edge chipping resistance is scarce. Purpose The purpose of this in vitro study was to determine the edge chipping resistance (ECR) and Martens hardness (HM) of 6 different dental CAD-CAM restorative materials before and after thermocycling. Material and methods Four composite resin materials including Brilliant Crios; Cerasmart, an experimental material; Lava Ultimate, a polymer-infiltrated ceramic-network (PICN) material (VITA Enamic), and a glass-ceramic control (IPS Empress CAD) were tested. The specimens were tested before and after thermocycling (30 000 times, 5 °C/55 °C). The ECR was measured for each material (n=25) and related to the point of loading and to the maximum chipping depth. HM was determined for each material (n=25). The Kruskal-Wallis and Mann-Whitney U tests were used to compare materials (α=.05). The impact of thermocycling was analyzed by using the Wilcoxon test (α=.05). The correlations between all parameters were calculated by using the Spearman-Rho test (α=.05). For fractographic analysis of chip patterns, chipped surfaces were analyzed by laser scanning microscopy. Results For ECR and HM, the materials showed different values. ECRmd and ECRpl showed a positive correlation, but both showed a negative correlation to HM. The materials showed a different chip size (P Conclusions All tested CAD-CAM materials behaved as brittle materials, but HM and ECR differed among the materials. The control glass-ceramic material showed the highest values for HM, followed by the PICN material. ECR values revealed the opposite order of materials, with the highest for composite resins. Artificial aging by thermocycling affected all dental CAD-CAM restorative materials. Especially for composite resin materials, ECR changed after aging.

Statement of problem High-performance thermoplastics have been adopted as framework materials. However, their bond strength to an esthetic veneering material is unclear. Purpose The purpose of this in vitro study was to test the tensile bond strength (TBS) between an aryl-ketone polymer (Ultaire AKP) and veneering resins. Material and methods AKP substrates (N=324) were prepared, airborne-particle abraded (Al2O3, 50 μm, 0.2 MPa), and divided into 9 groups (n=36) with different bonding systems (visio.link, Adhese Universal, All-Bond Universal, CLEARFIL UNIVERSAL BOND, G-Premio BOND, iBOND Universal, ONE COAT 7 UNIVERSAL, Scotchbond Universal) and without a bonding system as a control. Each group was further divided for opaquer (n=18). Further subdivision followed according to flowable or paste veneering resin (n=9). Specimens were stored in distilled water for 24 hours at 37 °C and thermocycled (×5000, 5/55 °C). TBS was measured and analyzed with the Kolmogorov-Smirnov test and 3-way ANOVA with partial eta squared (ηP2), followed by the Kruskal-Wallis and Mann-Whitney-U tests. Relative frequency of failure types was analyzed with the Chi2-test and a Ciba-Geigy table. Results The highest impact on TBS was exerted by the adhesive (ηP2=0.458, P Conclusions The application of opaquer increased TBS for all universal adhesives. Using opaquer and flowable veneering resin is beneficial for bonding to Ultaire AKP.

Objectives To investigate the retention force of polyetheretherketone (PEEK) removable dental prosthesis clasps in comparison with a cobalt-chrome-molybdenum control group after storage in artificial saliva. Materials and Methods Clasps were milled (Dentokeep (PEEKmilled1), NT digital implant technology; breCAM BioHPP Blank (PEEKmilled2), bredent), pressed (BioHPP Granulat for 2 press (PEEKpressed), bredent), or cast (remanium GM 800+ (cobalt-chrome-molybdenum), Dentaurum); N = 60, n = 15/subgroup. Retention force was examined 50 times/specimen in a pull-off test using the universal testing machine (Zwick 1445), where pull-off force was applied with a crosshead speed of 5 mm/minute until the maximum force dropped by 10%, at different aging levels: (1) initial, after storage in artificial saliva for (2) 90 and (3) 180 days. Statistical analysis was performed using one-way ANOVA followed by post hoc Scheffé-test and mixed models (p < 0.05). Results Cobalt-chrome-molybdenum presented the highest retention force. No differences were observed between polyetheretherketone materials. Cobalt-chrome-molybdenum showed a significant decrease of its values after artificial aging, while polyetheretherketone materials presented similar results over the course of aging. Regarding a repetitive insertion and removal, even though PEEKmilled2 and cobalt-chrome-molybdenum showed an initial increase, ultimately, a decrease in retention force was observed for all tested groups. Conclusions Although the control group showed significantly higher results, the retention force of polyetheretherketone materials indicate a potential clinical application. Neither the manufacturing process nor artificial aging showed an impact on the retention force of polyetheretherketone clasps. Clinical relevance Mechanical properties of novel removable dental prosthesis clasp materials devised to meet the growing esthetic demands of patients need to be investigated to ensure a successful long-term clinical application.

Objectives To examine the retention force of removable dental prosthesis (RDP) clasps made from polyetheretherketone (PEEK) and cobalt-chrome-molybdenum (CoCrMo, control group) after storage in water and artificial aging. Materials and methods For each material, 15 Bonwill clasps with retentive buccal and reciprocal lingual arms situated between the second pre- and first molar were manufactured by milling (Dentokeep [PEEKmilled1], NT digital implant technology; breCAM BioHPP Blank [PEEKmilled2], bredent), pressing (BioHPP Granulat for 2 press [PEEKpressed], bredent), or casting (remanium GM 800+ [CoCrMo], Dentaurum); N = 60, n = 15/subgroup. A total of 50 retention force measurements were performed for each specimen per aging level (initial; after storage [30 days, 37 °C] and 10,000 thermal cycles; after storage [60 days, 37 °C] and 20,000 thermal cycles) in a pull-off test. Data were statistically analyzed using one-way ANOVA, post hoc Scheffé and mixed models (p < 0.05). Results Initial, PEEKpressed (80.2 ± 35.2) and PEEKmilled1 (98.9 ± 40.3) presented the lowest results, while PEEKmilled2 (170.2 ± 51.8) showed the highest values. After artificial aging, the highest retention force was observed for the control group (131.4 ± 56.8). The influence of artificial aging was significantly higher for PEEK-based materials. While PEEKmilled2 and PEEKpressed showed an initial decline in retention force, all other groups presented no impact or an increase in retention force over a repetitive insertion and removal of the clasps. Conclusions Within the tested PEEK materials, PEEKmilled2 presented superior results than PEEKpressed. Although CoCrMo showed higher values after artificial aging, all materials exhibited sufficient retention to recommend usage under clinical conditions. Clinical relevance As RDPs are still employed for a wide range of indications, esthetic alternatives to conventional CoCrMo clasps are sought.

Objectives To test the polymerization stress of nine self-adhesive resin composite cements (G-CEM, iCEM, Bifix SE, Maxcem Elite, PANAVIA SA, SoloCem, SmartCem 2, SpeedCEM, RelyX Unicem 2) and one glass ionomer cement (control group; Ketac Cem). Materials and methods The crack propagation of a feldspar ceramic (n = 130) was determined by measuring crack lengths that originated from Vickers indentations, prior to and after the application and polymerization of the self-adhesive resin cements. Results for crack propagation were converted to polymerization stress values, and statistical analysis was performed using one-way ANOVA followed by Scheffé post hoc test. Results SmartCem 2 presented higher stress values than iCEM, SoloCem, and Ketac Cem, while Ketac Cem showed lower values than Bifix SE, Maxcem Elite, SmartCem 2, SpeedCEM, and RelyX Unicem 2. Conclusions Self-adhesive resin composite cements differ in their polymerization stress, which may affect the durability of the restoration. For restorations made from ceramics with lower flexural strength, such as feldspar ceramics, resin composite cement materials with less polymerization stress should be preferred. Clinical Relevance As a high polymerization shrinkage may increase crack propagation, the determination of the polymerization stress of self-adhesive resin composite cements employed for fixing all-ceramic restorations is an important factor.

ZusammenfassungSowohl für die Befestigung von Brackets als auch von Aligner-Attachments stehen verschiedene Materialien und Strategien zur Auswahl. Die Vorbereitung der Schmelz-Oberfläche für die adhäsive Befestigung kann mit Phosphorsäure im Etch and Rinse-Verfahren oder mittels diverser selbstätzender Adhäsive vorgenommen werden. Die Materialien zur Befestigung unterscheiden sich hinsichtlich der Monomermatrix, der Füllkörper und deren Anteile sowie ihres Initiatiorsystems. Brackets können direkt oder indirekt adhäsiv befestigt werden. Attachments für die Behandlung mit Alignern können ein- oder zweiphasig auf die entsprechenden Zähne aufgebracht werden. Ziel dieses Artikels ist es, anhand der aktuellen Literatur einen Überblick über die verschiedenen Materialien und Befestigungsstrategien zu geben.

PURPOSE To analyze the impact of different veneering techniques on the fracture load of telescopic secondary crowns made of a high-performance polymer (Ultaire aryl ketone polymer [UAKP]). MATERIALS AND METHODS Zirconia primary crown models (taper of 0 degrees) were prepared (N = 48), polished, scanned, and divided into four veneering groups (n = 12 each): premanufactured, digital, full anatomical, and vestibular. For all groups except vestibular, a standardized telescopic secondary crown (thickness: 0.6 mm, circular margin: 1 mm) was constructed, adapted to the corresponding primary crown, milled from UAKP, and veneered. The veneered master crown was developed based on the premanufactured group. After surface polishing, all specimens were artificially aged in a chewing simulator (1.2 million cycles, 50 N, 1.1 Hz, between 5°C and 55°C). Fracture load was tested in a universal testing machine with a piston (O = 6 mm, 1 mm/minute). Fracture patterns were analyzed. For statistical analysis, Kolmogorov-Smirnov test and descriptive statistics followed by one-way ANOVA with post hoc Scheffe test were conducted (P < .05). RESULTS Significant differences in fracture load were found between different veneering techniques (P < .001), with the highest values for the vestibular and digital groups, followed by the premanufactured group. Full anatomical veneering showed the significantly lowest fracture load (1,885 ± 397 N). For all specimens, cohesive brittle fractures with similar fracture patterns occurred, irrespective of the veneering technique. CONCLUSION The veneering technique of telescopic secondary crowns made of high-performance polymer affects overall stability. All veneering techniques provided sufficient fracture load values for telescopic secondary crowns made of UAKP. Digital veneers seem the most recommendable.

Objectives To test and compare five pressable lithium-X-silicate-ceramics on their mechanical and wear properties. Methods Specimens were pressed and prepared from: i. Amber Press (AP), ii. Celtra Press (CP), iii. Initial LiSi Press (IL), iv. Livento Press (LP), and v. IPS e.max Press (IE). Four-point flexural strength (FS), SEVNB fracture toughness (KIC), three-body wear (3BW), Martens hardness (HM) and indentation modulus (EIT) were measured. For CP, FS and HM were measured with and without additional Power Firing. Each subgroup contained 15 specimens. Data were analyzed using Kolmogorov–Smirnov, one-way ANOVA followed by Scheffe test, Kruskal–Wallis-H-, Mann–Whitney-U-, and Spearman–Rho-test (p Results AP and CP presented higher FS than IL. LP presented the highest Weibull modulus. CP showed lower KIC values than AP, and AP was not significant compared to LP and IE. The most 3BW material loss was observed for CP. CP revealed higher HM values than the remaining ceramics. IL presented lower EIT compared to AP and CP. The following correlations were observed between the test parameters: 3BW with FS (r = 0.279, p = 0.015), with HM (r = −0.378, p = 0.001), and with EIT (r = −0.344, p = 0.004); EIT with FS (r = 0.203, p = 0.028); and HM with FT (r = −0.223, p = 0.027) and EIT (r = 0.884, p Significance AP followed by LP showed the highest and IL followed by CP the lowest properties tested. Power Firing of CP improved the flexural strength. Ceramics with high flexural strength and Martens parameters showed lower wear. Materials with high Martens hardness presented lower fracture toughness values and ones with high indentation modulus showed high flexural strength.

To determine the fracture load before and after artificial aging of implant-supported 4-unit cantilever fixed dental prostheses (FDP) with frameworks made of two differently filled polyetheretherketone (PEEK) compounds and veneered using three different techniques.A total of 120 duplicate 4-unit FDP frameworks were produced (n = 60 milled from PEEK, 20% TiOVeneering technique and filler content significantly affected the fracture load (p 0.001). Prefabricated veneers showed higher fracture load (p ≤ 0.001) whereas digital and conventional veneerings were similar (p = 0.451). PEEK with 30% filler content presented higher fracture load (p 0.001) compared with PEEK with 20%. Aging showed no effect on fracture load (p = 0.176). Regarding fracture types, no significant differences were found among the groups (p = 0.055).Filler content of PEEK compound as well as veneering technique influenced fracture load while aging had no effect on fracture load. FDPs made of PEEK with 30% of filler content veneered using prefabricated veneers had the highest fracture resistance.

OBJECTIVES To test and compare two types of implant systems restored with four monolithic polymer-based materials with regard to their bending moments (BM) before and after aging. METHODS A total of 192 tissue-level implants (TRI Dental Implants) differing in the presence (TiB, Octa line, n = 96) or absence (NTiB, Matrix line, n = 96) of a titanium base were restored with mandibular right first molar crowns manufactured from composite (CC), polymer-infiltrated ceramic (VE), PMMA (PM) and a 3D printed resin (ND) (n = 24). Half of the specimens (n = 12) were loaded for 1,200,000 cycles (50 N, 1.3 Hz, TC: 5/55 °C, 6000×) and examined for failures. Fracture load was measured according to ISO standard 14801, BM was calculated, and fracture types were examined. Data were analyzed using parametric statistics (p 0.116). When aged, restoration material had no impact on the BM values of NTiB implants (p ≥ 0.233). Aged TiB implants showed higher values in combination with CC than with ND (p = 0.001). PM and VE showed similar values as ND and CC. Artificial aging led to a decrease of BM within PM, CC and ND on NTiB implants and ND on TiB implants. The majority of failures after testing were characterized by crown fractures in two to four pieces. Fractures in more pieces with smaller fragments occurred primarily for ND. SIGNIFICANCE The use of NTiB implants with the polymer-based materials tested can only be recommended for clinical use as interim prostheses. CC seems to show a positive effect on the BM. Clinical research investigating the in vivo behavior is necessary to confirm these findings.

Objectives The aim of this study is to investigate the influence of the material and corresponding sintering protocol, layer thickness, and aging on the two-body wear (2BW) and fracture load (FL) of 4Y-TZP crowns. Materials and methods Multi-layer 4Y-TZP crowns in three thicknesses (0.5 mm/1.0 mm/1.5 mm) were sintered by high-speed (Zolid RS) or conventional (Zolid Gen-X) sintering. 2BW of ceramic and enamel antagonist after aging (1,200,000 mechanical-, 6000 thermal-cycles) was determined by 3D-scanning before and after aging and subsequent matching to determine volume and height loss (6 subgroups, n = 16/subgroup). FL was examined initially and after aging (12 subgroups, n = 16/subgroup). Fractographic analyses were performed using light-microscope imaging. Global univariate analysis of variance, one-way ANOVA, linear regression, Spearman’s correlation, Kolgomorov–Smirnov, Mann–Whitney U, and t test were computed (alpha = 0.05). Weibull moduli were determined. Fracture types were analyzed using Ciba Geigy table. Results Material/sintering protocol did not influence 2BW (crowns: p = 0.908, antagonists: p = 0.059). High-speed sintered Zolid RS presented similar (p = 0.325–0.633) or reduced (p p p Conclusions High-speed sintered crowns with a minimum thickness of 1.0 mm showed sufficient mechanical properties to withstand masticatory forces, even after a simulated aging period of 5 years. Clinical relevance Despite the manufacturer indicating a thickness of 0.5 mm to be suitable for single crowns, a minimum thickness of 1.0 mm should be used to ensure long-term satisfactory results.

Objective This interlaboratory round robin test investigated the robustness of the Chevron-Notch Beam (CNB) test method and the effect of the processing and testing variations on the fracture toughness of a dental 3Y-TZP ceramic. Methods The round robin test was performed precisely following the procedures recommended in ISO 24370:2005 and applied on a commercial 3Y-TZP ceramic (product information). A total of 335 test specimens with dimensions 3×4 x 45 mm³ was equally distributed among 10 participating laboratories of varying experience in fracture toughness testing. A standard operating procedure was defined with either narrow processing tolerances or alternative (wider) processing tolerances (as proposed in ISO 24370). Fracture toughness data (series 2) was analyzed using one way ANOVA followed by post hoc Tukey HSD test and 95% Confidence Intervals (CI) were computed (p < 0.05). A further, preceding round-robin (series 1) test was conducted with - more possible variations of test conditions regarding CNB notch processing and storage conditions. Those results are summarized in the supplement and discussed with the actual ISO 24370 test. Results Fracture toughness of the 3Y-TZP ceramic material, summarized over all laboratories was measured to KIc = 4.48 ± 0.11 MPam0.5 for the standard processing tolerance and KIc = 4.55 ± 0.31 MPam0.5 for the alternative tolerance. The results revealed a significant influence of cutting offset and notch geometry on KIc when using CNB method. The test medium also has a significant influence on KIc in terms of reduced fracture toughness under the influence of water. With defined testing conditions the number of valid tests and reduced standard deviation increased. In case of strictly following such standard operation procedures, KIc can be determined with high reliability. There is no difference between the involved laboratories, but significant influence of cutting offset on KIC was observed. Significance The CNB method is suitable method for determination of KIc on fine-grained ceramics such as 3Y-TZP ceramic. By using tighter tolerances for processing and testing, i.e. closely following the ISO 24370 procedure, a highly-precise evaluation of fracture toughness with low data variation is achievable. The information of the storage medium should always be reported along with the data. CNB fracture toughness testing is an alternative method compared to Single-edge V-notch beam (SEVNB), especially for fine-grained ceramics.

High-speed sintering allows the rapid fabrication of esthetic restorations with adequate flexural strength. However, data on the fatigue behavior of high-speed sintered 4 mol% yttria-stabilized tetragonal zirconia polycrystal (4Y-TZP) are lacking.The purpose of this in vitro study was to examine the effect of high-speed sintering and the preshading of blanks (monochrome versus multilayer) on the fatigue behavior of 4Y-TZP ceramics.Four-point flexural strength specimens (N=405) were fabricated from high-speed sintered multilayer 4Y-TZP (Zolid DRS) processed at 1580 °C for about 20 minutes and conventionally sintered at 1450 °C for about 10 hours, multilayer 4Y-TZP (Zolid Gen-x), and monochrome 4Y-TZP (Ceramill Zolid HT+PS), the control group. The specimens were loaded under 5 different dynamic test conditions for fatigue testing (P1-P5). Three were step-stress protocols (P1: 50 N for 5000 cycles; P2: 10 N for 1000 cycles, P3: 5% for 5000 cycles), 1 was tested with a constant force of 720 N (P4), and 1 was tested for different constant load levels (P5). For analysis of P1-P3, the Kaplan-Meier test and Mantel Cox test were performed (α=.05). P4 was analyzed with the Kolmogorov-Smirnov, Kruskal-Wallis, and Mann-Whitney U tests, and P5 by creating a load-cycle diagram. A fracture analysis was performed.ZMLC showed better fatigue behavior than ZMLH (P≤.006) and ZMOC (P≤.002) in all 3 step-stress protocols (P1-P3). ZMLH showed results comparable with those for ZMOC (P≥.285). In P4 and P5, all materials showed comparable values (P=.163 for P4).The multilayer technique showed a positive effect on the fatigue behavior of 4Y-TZP. In contrast, high-speed sintering negatively influenced the fatigue behavior of multilayer 4Y-TZP. The high-speed sintered material showed no deterioration compared with the conventional sintered monochrome material.

ObjectiveThe objective of this in vitro study was to investigate fracture load, fracture types, and impact of chewing simulation of human molars restored with 3D printed indirect polyetheretherketone (PEEK) inlays and compare these with milled indirect PEEK inlays, direct resin composite fillings, and sound teeth.Materials and methodsA total of 112 molars with form congruent class I cavities were restored with (n = 16/group) 3D printed indirect PEEK inlays via fused layer manufacturing (FLM): (1) Essentium PEEK (ESS), (2) KetaSpire PEEK MS-NT1 (KET), (3) VESTAKEEP i4 G (VES), (4) VICTREX PEEK 450G (VIC), (5) milled indirect PEEK inlays JUVORA Dental Disc 2 (JUV), and (6) direct resin composite fillings out of Tetric EvoCeram (TET). Sound teeth (7) acted as positive control group. Half of the specimens of each group (n = 8) were treated in a chewing simulator combined with thermal cycling (1.2 million × 50 N; 12,000 × 5 °C/55 °C). Fracture load and fracture types of all molars were determined. Statistical analyses using Kolmogorov-Smirnov test and two-way ANOVA with partial eta squared (ηp2) followed by Scheffé post hoc test, chi square test and Weibull modulusmwith 95% confidence interval were computed (p ResultsESS and TET demonstrated the lowest fracture load with a minimum of 956 N, whereas sound molars showed the highest values of up to 2981 N. Chewing simulation indicated no impact (p = 0.132). With regard to Weibull modulus, KET presented a lower value after chewing simulation than JUV, whereas TET had the highest value without chewing simulation. All indirect restorations revealed a tooth fracture (75–100%), direct resin composite fillings showed a restoration fracture (87.5%), and 50% of the sound teeth fractured completely or had cusp fractures.ConclusionsAll 3D printed and milled indirect PEEK inlays as well as the direct resin composite fillings presented a higher fracture load than the expected physiological and maximum chewing forces.Clinical relevance3D printing of inlays out of PEEK via FLM provided promising results in mechanics, but improvements in terms of precision and esthetics will be required to be practicable in vivo to represent an alternative dental material.

PURPOSE To investigate the tensile bond strength between zirconia abutments and titanium bases, luted with two different resin composite cements, after different cleaning procedures. MATERIALS AND METHODS Zirconia abutments and titanium bases were luted with either a DMA/HEMA-based cement (n = 80; Multilink Hybrid Abutment, Ivoclar Vivadent) or a Bis-GMA/TEGDMA-based cement (n = 80; Panavia V5, Kuraray Noritake). The adhesive gap of half of the specimens was polished (n = 40 per resin composite cement). Four separate specimens underwent roughness measurements and scanning electron microscopy. The specimens were divided into four groups (n = 10 per subgroup): (1) not cleaned, (2) cleaning in an ultrasonic bath, (3) cleaning in an autoclave, and (4) treatment with low-pressure plasma. The specimens were thermocycled (20,000×, 5°C/55°C), tensile bond strength was tested, and fracture types were analyzed. Data were examined using the Kolmogorov-Smirnov test, univariate ANOVA with additional partial eta-squared (ηp2), and the Mann-Whitney U test. The defined level of significance was adjusted by Bonferroni correction (P < .003). RESULTS The tensile bond strength of specimens luted with the DMA/HEMA-based cement was higher than that of specimens luted with the Bis-GMA/TEGDMA-based cement. The polishing step and the cleaning procedures showed no impact on tensile bond strength results. Specimens luted with the DMA/HEMA-based cement presented more cohesive fractures, whereas specimens luted with the Bis-GMA/TEGDMA-based cement presented themselves with more fractures of the interface between the resin composite cement and zirconia abutment. Ra values showed a decline in roughness after polishing for both resin composite cements. CONCLUSION As the DMA/HEMA-based cement showed higher tensile bond strength values, the usage of this resin composite cement for luting implant abutments to titanium bases can be recommended. Neither polishing nor the use of different cleaning procedures had an impact on tensile bond strength.

PURPOSE To assess surface characteristics and implant stability after implantoplasty performed by two different instrument sequences regarding material loss, surface roughness, and fracture load resistance. Additionally, operators' subjective experience during instrumentation and the damage to neighboring teeth were evaluated. MATERIALS AND METHODS Titanium implants were placed in the position of both first maxillary molars in models exposing 6 mm of their surface. Implantoplasty was performed in phantom heads: Exposed surfaces were instrumented with diamonds and Arkansas stones or abrasive stones and silicone polishers. Operators reported on abrasion, gloss, effectiveness, and tactility using a visual analog scale (VAS). Residual wall thickness of implants was measured on radiographs, material abrasion using three-dimensional (3D) scans, and surface roughness by contact profilometry. Maximum bending moments were measured. RESULTS Residual thickness and weight loss were comparable after both treatments (0.3 ± 0.1 and 0.25 ± 0.07 mm and 0.22 ± 0.01 g, and 0.03 ± 0.01 mm and 0.02 ± 0.01 g, respectively, P > .05). Mean surface roughness was lower (P = .0001) for the group with the silicone polishers (0.4 ± 0.2 μm) compared with the group employing diamonds (0.8 ± 0.1 μm). Maximum bending moments showed neither intergroup differences nor stability loss compared with untreated implants. The stone-and-silicone polisher group showed less abrasion (4.6 ± 2.2) and higher gloss values (8.1 ± 1.4) than the diamond-and-Arkansas group (3.1 ± 1.3 and 4.1 ± 2.1, respectively). Superficial tooth injuries at proximal neighbor teeth were common (73% and 80%). CONCLUSION Implantoplasty did not weaken implant stability. The use of silicone polishers revealed lower surface roughness. Regarding surface smoothness, the instrumentation sequence employing silicon carbide and Arkansas stones followed by silicone polishers seems to be superior to the combination of diamond and Arkansas stones.

Objective To test the impact of zirconia pretreatment and aging on flexural strength and phase structure. Methods For flexural strength measurements, 180 3Y-TZP0.25 specimens were fabricated and pretreated: (i) air-abraded (105-μm alumina, 0.25 MPa), (ii) air-abraded (50-μm alumina, 0.25 MPa), (iii) air-abraded (30-μm silica-coated alumina, 0.28 MPa) (iv) non-pretreated. Each pretreated group (n = 15) was aged: (a) hydrothermal (134 °C, 0.23 MPa, 2 h) (b) in a mastication simulator (1,200,000×, 5/55 °C) and (c) not aged. The fractured specimens were stored dry for 5 years (23 °C) for analysis of phase transformation. Additionally, specimens were fabricated from 3Y-TZP0.25 (n = 12) and 3Y-TZP0.05 (n = 8), pretreated (i, ii, iii, iv), and hydrothermally aged. Each air-abrasion method was alternated using 0.05, 0.25 and 0.4 MPa pressure. The phase transformation was examined by Raman spectroscopy and surface topography by scanning electron microscope. Data were analyzed using univariate ANOVA with the Scheffe post hoc test and partial-eta-squared (ƞp²) (α = 0.05). Results The highest impact on flexural strength was exerted by the pretreatment (ηP² = 0.261, p Significance Air-abrasion with 30-μm silica-coated alumina powder can be recommended for pretreatment of 3Y-TZP0.25 and 3Y-TZP0.05. For air-abrasion using alumina powder lower pressure should be used.

To test the impact of polishing strategies on zirconia properties. One hundred eight zirconia specimens were divided into nine groups (n = 12/group). Seven groups were polished in the white-stage with either (1) a felt wheel (FW), (2) a felt wheel combined with a polishing paste (FWP), (3) a goat hair brush (GB), (4) a goat hair brush combined with a polishing paste (GBP), (5) a green-state finishing kit (FK), (6) a universal polisher (UP), or (7) with SiC polishing paper (PP), and sintered. Thereafter, the seven groups were divided into two subgroups each and polished using (1) a fine polisher (one-step, n = 6) or (2) a rough and fine polisher (two-steps, n = 6). The positive control group (polish-lab-kit, PLK) was sintered and polished in two-steps. The no polished group (NP) acted as negative control group. Translucency (T%) was measured after white-stage polishing and sintering, and after sintered-stage polishing. Surface free energy (SFE), surface roughness (SR), and flexural strength (FS) were determined. Data were analyzed using one-way ANOVA with Tukey-B post-hoc, t test, and Wilcoxon-test (p

OBJECTIVES To assess the mechanical stability of implants after implantoplasty and thermocyclic loading, the residual thickness of the instrumented areas and neighbouring tooth injury due to implantoplasty. MATERIALS AND METHODS Using a phantom head simulator and maxillary model implants were subjected to an implantoplasty procedure. Thirty implants were randomly assigned to receive one of three instrumentation sequences. After instrumentation, injury on neighbouring teeth was assessed. Instrumented implants and non-instrumented controls were subjected to 1.2 million cycles of thermo-mechanical loading in a chewing machine. Afterwards, maximum fracture load for all implants and an additional five pristine control implants was tested. RESULTS Generally, damage of neighbour teeth was a frequent finding (33 ± 56% of all cases) with considerable inter-group differences. No considerable inter-group difference for the residual implant thickness was found for different areas assessed. No implant fractured during cyclic loading. Fracture load was reduced after cyclic loading of uninstrumented implants from 2,724 ± 70 N to 2,299 ± 127 N, and after implantoplasty to 1,737 ± 165 N, while no effect by the instrumentation sequence could be observed. CONCLUSIONS Both implantoplasty and cyclic loading were shown to reduce the implants' maximum bending strength. Cyclic loading in a laboratory masticator, simulating a five-year equivalent of chewing, did not result in fractured implants. Since neighbouring tooth injury was assessed often, care should be taken with the selection of suitable instruments.

To investigate the impact of pretreatment and conditioning on shear bond strength (SBS), surface free energy (SFE) and surface roughness (SR) between polyetheretherketone (PEEK) and cold-cured polymethylmethacrylate (PMMA).PEEK substrates (Dentokeep PEEK Disc, nt-trading) were air abraded with Al2O3 particles of different grain sizes applied with varying pressure at 1) 0.2 MPa - 50 µm Al2O3; 2) 0.4 MPa - 50 µm Al2O3; 3) 0.2 MPa - 110 µm Al2O3; 4) 0.4 MPa - 110 µm Al2O3; or 5) without air abrasion (n = 172/group). Surface properties were quantified using SFE and SR (n = 10/group), and scanning electron microscope imaging (n = 2/group). Substrates were conditioned with a) Visio .link (VL, Bredent); b) Scotchbond Universal (SU, 3M Oral Care); c) Bonding Fluid (BF, Schütz Dental); or d) without conditioning (WC; n = 40/subgroup) and bonded to the polymer (Futura Jet, Schütz Dental). SBS and fracture types were determined before and after 10,000 thermal cycles (n = 20/subgroup). Univariate ANOVA, Kruskal-Wallis test, Mann-Whitney U-test, Kaplan-Meier survival estimates, and Weibull distribution were computed (p0.05). Ciba-Geigy tables and the chi-squared test were used to analyze fracture type distributions.An increase in particle size and pressure resulted in similar or increased SBS, Weibull characteristic strength, and Weibull moduli (p0.001 - 0.046). The lowest results were observed for the control group (without air abrasion), while pretreatment with 0.4 MPa - 110 µm Al2O3 presented the highest values (p0.001). In comparison with the other conditioning procedures, VL showed high (p0.001 - 0.03), and SU and WC low SBS (p0.001 - 0.006). Although it did not influence SFE, an increase in particle size and pressure led to an increased SR (p0.001).Pretreatment with 0.4 MPa - 110 µm Al2O3 can be recommended to increase bonding properties between PEEK and PMMA. Application of adhesives such as VL can enhance SBS further.

OBJECTIVE To analyze the impact of the color of a resin composite cement (RCC) on the optical properties of different computer-aided design and computer-aided manufacturing (CAD/CAM) ceramics. MATERIALS AND METHODS Specimens (N = 220, thickness: 0.9 ± 0.03 mm) were fabricated from: leucite (Initial LRF Block/IPS Empress CAD), lithium disilicate (Amber Mill/IPS e.max CAD), lithium metasilicate (Celtra Duo), and lithium alumina silicate ceramic (n!ce) in translucency levels HT and LT. All specimens were bonded with an RCC (Light+/Warm+). Color was analyzed (spectrophotometer) initially as well as after bonding of RCC with CAD/CAM ceramics using CIELab and CIEDE2000. Kolmogorov-Smirnov test, one-way ANOVA and t test served for analyzing (α = 0.05). RESULTS Highest impact on ΔE presented the choice of ceramic (ηp2 = 0.155/p

To investigate the impact of crown geometry, crown/abutment/antagonist material and thermal loading on the two-body wear of dental materials caused by chewing simulation.For the crown geometry, crowns (polymethylmethacrylate (PMMA), polyetheretherketone (PEEK) and silicate ceramic (SiOPMMA crowns presented the highest and PEEK the lowest material losses. Flat CINC showed the lowest material losses for PEEK and SiOCrown geometry influences the crown and antagonists wear, with an increased cusp inclination entailing increased wear. For in vitro set-ups, CoCr abutments and RECO antagonists present valid alternatives to natural teeth. For polymers, in vitro chewing simulations may be performed at a constant temperature (37 °C).