Load-bearing capacity of handmade and computer-aided design--computer-aided manufacturing-fabricated three-unit fixed dental prostheses of particulate filler composite

Effect of filler contents on the bond strength of CAD/CAM resin crowns: New resin primer versus conventional silane agents

Purpose This study aims to evaluate the effects of resin primers containing methyl methacrylate (MMA) and silane agent on the bonding effectiveness of indirect resin composite blocks with three different filler contents.Methods A commercially available computer-aided design/computer-aided manufacturing (CAD/CAM) resin composite block and two experimental resin composite blocks with different filler contents were alumina-blasted and two surface treatments (primer and silane agent) were applied. The resin cement was built up, and the micro-tensile bond strength (μTBS) was measured after 24 hours, 1 month or 3 months of water storage (n = 24 per group). The fracture surfaces after μTBS measurements and resin block/cement interface were observed by scanning electron microscopy (SEM).Results The primer treatment group showed a significantly higher bond strength than the silane group only in F0 (filler content 0 wt%) group (P < 0.001). In the primer group, F0 and F41 (filler content 41 wt%) groups showed significantly higher bond strengths than F82 (filler content 82 wt%) group (P < 0.001). In contrast, in the silane group, F41 group showed significantly higher bond strength than F0 and F82 groups (P < 0.001), and F82 group showed significantly higher bond strength than F0 group (P < 0.001). SEM revealed that the matrix resin was partially destroyed on the fracture surface of the primer group, and an uneven interface surface was observed compared with that of the silane group.Conclusions MMA-containing primers showed higher bonding effectiveness to CAD/CAM resin composite blocks than the silane treatment.

Examination of the effect of aging process on marginal fit and fractute strength of temporary crowns prepared from different materials

Aim

The aim of this study is to investigate the effect of the aging process on the marginal fit and fracture resistance of temporary crowns prepared using different materials.

Materials and method

The steel die to represent the maxillary first premolar used in this study was produced on a CNC turning machine to include an anatomical occlusal surface. A total of 160 epoxy resin dies were obtained by taking impressions with conventional impression methods on the metal die. Epoxy resin dies were randomly divided into four groups. Temporary crowns were prepared for each group from poly acrylic resin (Vita CADTemp®), bis-acryl composite resin (Protemp 4), poly methyl methacrylate (PMMA; Imident) and poly ethyl methacrylate (PEMA; Dentalon Plus) restorative materials. Half of the specimens (n = 20) in each group (n = 40) were randomly separated and the aging process was applied 5000 times in the device. Marginal gap measurements on epoxy resin dies were made using a stereomicroscope. The fracture strength test of the specimens was performed by using the Instron Universal Test Device. Jamovi 2.2.5 statistical program was used for statistical analysis.

Results

When compared to temporary crowns prepared from all other materials, poly acrylic resin (Vita CADTemp ®) temporary crowns observed significantly lower marginal gap values (59,05 μm) regardless of the aging process, and a significantly higher fracture resistance (478,44 N) in the presence of aging process (p < .05 for each). While the highest marginal gap value was detected in PMMA (Imident) (120.36 μm) temporary crowns with aging process, the lowest marginal gap value was observed in poly acrylic resin (Vita CADTemp®) (59.05 μm) crowns without non-aging process. The marginal fit and fracture resistance of all temporary crowns were negatively affected by the aging process.

Conclusion

Our findings revealed the superiority of poly acrylic resin (Vita CADTemp®) crowns to the temporary crowns prepared from all other materials in terms of the significantly lower marginal gap in the absence of aging process, and the significantly higher fracture resistance in the presence of aging process. Marginal fit and fracture resistance values for all materials were found to be within clinically acceptable limits.

Biocompatibility and biofilm formation on conventional and CAD/CAM provisional implant restorations

Dental implant treatment is a complex and sophisticated process, and implant provisional restorations play a vital role in ensuring its success. The advent of computer-aided design and computer-aided manufacturing (CAD/CAM) technology has revolutionized the field of implant restorations by providing improved precision leading to a reduction in chair time and more predictable treatment outcomes. This technology offers a promising solution to the drawbacks of conventional methods and has the potential to transform the way implant procedures are approached. Despite the clear advantages of CAD/CAM over conventional provisional implant restorations including higher accuracy of fit and superior mechanical properties, little research has been conducted on the biological aspect of these novel restorations. This study aims to fill that gap, comprehensively assessing the biocompatibility, gingival tissue attachment and biofilm formation of a range of provisional implant restorations using CAD/CAM technology through milling and 3-D printing processes compared to conventional fabrication. The biocompatibility of the tested restorations was assessed by MTT assay, Calcein-AM assay as well as SEM analysis. The surface roughness of the tested samples was evaluated, alongside the attachment of Human Gingival Fibroblasts (HGF) cells as well as biofilm formation, and estimated Porphyromonas gingivalis (P. gingivalis) cell count from DNA detection.The results showed all tested provisional implant restorations were non-toxic and good HGF cell attachment but differed in their quantity of biofilm formation, with surface texture influenced by the material and fabrication technique, playing a role. Within the limitation of this study, the findings suggest that CAD/CAM-fabricated provisional implant restorations using a milling technique may be the most favourable among tested groups in terms of biocompatibility and periodontal-related biofilm formation.

Micro-CT Marginal and Internal Fit Evaluation of CAD/CAM High-Performance Polymer Onlay Restorations

(1) Background: The use of high-performance polymers for fixed restorations requires additional studies regarding their adaptability and processing with CAD/CAM technology. This in vitro study aims to assess the marginal and internal fit of PEEK and PEKK materials using microcomputed tomography. (2) Methods: Twenty-four (n = 8) MOD onlays made of PEKK (Pekkton ivory), unmodified PEEK (Juvora medical), and modified PEEK (BioHPP) were investigated. A typodont mandibular left first molar was scanned to achieve 24 resin, 3D printed abutment teeth. The onlays were fabricated with a five-axis milling machine, and after cementation of the specimens, the marginal (MG) and internal gaps (IG) were evaluated at twelve points in the mesio-distal section and thirteen points in the bucco-lingual section using microcomputed tomography. For statistical data analysis, Wilcoxon signed-rank/paired Student t-Test, Mann-Whitney/unpaired Student t-Test, and one-way ANOVA test were applied. (3) Results: Significant differences (p < 0.05; α = 0.05) were reported between the MG and IG for each material for all three polymers and also among two materials in terms of the MG and IG (except Juvora-BioHPP). The highest IG values were recorded in angular areas (axio-gingival line angle) in the mesio-distal section for all the polymers. (4) Conclusions: For all the materials, MG < IG. The type of polymer influenced the adaptability; the lowest marginal and internal gap mean values were recorded for BioHPP. The analyzed polymer used for onlays are clinically acceptable in terms of adaptability.

Probability of survival and failure mode of endodontically treated incisors without ferrule restored with CAD/CAM fiber-reinforced composite (FRC) post-cores

PURPOSE

This study evaluated the probability of survival and failure mode of endodontically treated incisors without ferrule restored with CAD/CAM FRC post-cores.

METHODS

Root canals of bovine incisors were treated, leaving post preparations of ∼10 mm. Teeth were allocated into three groups: (i) cast metal post-core, (ii) FRC prefabricated post with a direct resin core build-up, and (iii) CAD/CAM FRC post-core. Posts and zirconia crowns were cemented using resin cement. Specimens were subjected to step-stress accelerated-life fatigue testing in water. Use level probability Weibull curves, probability of survival for a mission of 100,000 cycles at 25, 50, and 100 N, Weibull modulus, and characteristic strength were calculated and plotted. Failure mode was examined under a stereomicroscope.

RESULTS

Restored incisors demonstrated high probability of survival (93-100%) for missions estimated at 25 and 50 N, irrespective of post-core foundation. At 100 N, incisors restored with metal posts presented significantly higher probability of survival (99%) relative to CAD/CAM posts (79%), whereas FRC groups demonstrated no significant difference. Weibull analysis indicated no significant difference on the Weibull modulus (m = 3.38-5.92). Incisors reconstructed with metal post-cores (431 N) presented significantly higher characteristic strength relative to prefabricated (200 N) and CAD/CAM (202 N) FRC post-cores. While post fracture was the chief failure mode for prefabricated and CAD/CAM FRC post-cores, post and/or root fracture were the main event for metal post-cores.

CONCLUSION

Endodontically treated incisors without ferrule restored with CAD/CAM FRC post-cores presented promising probability of survival for loads compatible with anterior masticatory forces and favorable failure modes.

Fracture behavior of discontinuous fiber-reinforced composite inlay-retained fixed partial denture before and after fatigue aging

PURPOSE

To evaluate the fracture behavior of inlay-retained fixed partial dentures (IRFPDs) made of experimental short fiber-reinforced composite (SFRC) computer-aided design/computer-aided manufacturing (CAD/CAM) block before and after cyclic fatigue aging.

METHODS

Five groups (n=20/group) of three-unit posterior IRFPDs were fabricated. The first and second groups were CAD/CAM fabricated from experimental SFRC blocks or lithium-disilicate (IPS e.max CAD, IVOCLAR) materials, the third group comprised a three-dimensional-printed composite (Temp PRINT, GC), and the fourth and fifth groups comprised conventional laboratory flowable composite (Gradia Plus, GC) and commercial flowable SFRC (everX Flow, GC), respectively. All IRFPDs were luted into a metal jig with adhesive dual-cure resin cement (RelyX Ultimate, 3M ESPE). Half the IRFPDs per group (n=10) were subjected to fatigue aging for 10,000 cycles. The remaining half were statically loaded until fracture without fatigue aging. The load was applied vertically between triangular ridges of the buccal and lingual cusps. The fracture mode was visually examined using optical and scanning electron microscopy (SEM). Data were statistically analyzed using a two-way analysis of variance (ANOVA) followed by Tukey's HSD test.

RESULTS

ANOVA revealed that IRFPDs made of experimental SFRC CAD/CAM had the highest (p<0.05) load-bearing capacity before (2624±463 N) and after (2775±297 N) aging among all groups. Cyclic fatigue aging decreased the load-bearing capacity (p>0.05) of all tested prostheses, except for the experimental SFRC CAD/CAM and conventional laboratory composite IRFPDs (p>0.05). SEM images showed the ability of discontinuous short fibers in the experimental SFRC CAD/CAM composite to redirect and hinder crack propagation.

CONCLUSION

CAD/CAM-fabricated IRFPDs made of experimental SFRC blocks showed promising performance in clinical testing in terms of fracture behavior.

Effectiveness of surface treatment on bond strength of ceramic brackets to two types of CAD/CAM-prepared nanohybrid composites

OBJECTIVES

The aim of this study was to assess the influence of surface treatment on the shear bond strength of two different adhesive-coated orthodontic ceramic brackets to computer-aided design/computer-aided manufacturing (CAD/CAM) nanohybrid composite.

METHODS

A total of 120 specimens (10 mm × 10 mm × 3 mm) were prepared from each type of CAD/CAM block (Grandio [GR], VOCO Cuxhaven, Germany; Lava Ultimate [LU], 3M ESPE, St. Paul, MN, USA). For each type of CAD/CAM block, the plates were divided into four groups based on the applied surface treatment: hydrofluoric acid (HF), grinding bur (GB), silica coating with CoJet system (CS), and titanium tetrafluoride (TiF₄) 2 wt/v%. Maxillary central incisors of adhesive-coated ceramic orthodontic brackets (APC Flash-free Clarity Advanced Ceramic, 3M Unitek, Monrovia, CA, USA) were bonded using Transbond XT Primer (3M Unitek, Monrovia, CA, USA). Shear bond strength was conducted, and the modes of failure were assessed utilizing the adhesive remnant index. Surface roughness and topography of treated CAD/CAM were evaluated. Data were statistically analyzed using two-way analysis of variance (ANOVA) and Tukey's test. The Weibull analysis was conducted on shear bond strength data.

RESULTS

Surface treatment with 2% TiF₄ wt/v revealed significantly higher bond strength (GR, 14.51 ± 2.57 MPa; LU, 11.19 ± 2.17 MPa) than other groups for both types of CAD/CAM restorative materials (p < 0.05). Adhesive failures were the predominant mode of failure. Surface treatment with CS revealed higher surface roughness than other groups (p < 0.05).

CONCLUSIONS

Surface treatment with 2% TiF₄ wt/v enhanced the adhesion between orthodontic ceramic brackets to GR and LU CAD/CAM composite restorative materials. GR CAD/CAM nanohybrid composite had higher bond strength than LU to ceramic orthodontic brackets.

Combination of a silane coupling agent and resin primer reinforces bonding effectiveness to a CAD/CAM indirect resin composite block

The effects of silanization and resin primer application on CAD/CAM indirect resin composite block bonding were investigated. KATANA AVENCIA P blocks (Kuraray Noritake Dental) were treated with a silane coupling agent and/or a resin primer. The contact angles (CAs) of resin primer were observed before and after silanization. Panavia V5 (Kuraray Noritake Dental) was built after each treatment. Bond strengths were measured, and the interface was analyzed by energy dispersive X-ray spectroscopy (EDS). The CA showed that silane treatment improved the wettability of the resin primer to the resin block. The combination treatment of the silane and resin primer showed significantly higher bond strength than no treatment, only in the silanization or resin primer group (p<0.001 each). EDS analysis showed that the resin primer penetrated both cement and block sides. The combination of the silane and resin primer improved bonding effectiveness between the resin block and resin cement.

Repair of temporary fixed dental prostheses using a flowable resin composite: Effect of material, bonding, and aging

Objectives

Assessment of the effect of aging and bonding on the reparability of different temporary crown and bridge materials using a flowable resin composite.

Methods

The materials used included two bis-acryl and two polymethylmethacrylate materials. The materials were aged either dry, in distilled water, or in a 75% ethanol/water solution. Each group was divided into three subgroups (n = 6) according to the bonding method: application of a universal adhesive, application of a universal primer followed by a universal adhesive, or no bonding. Materials were repaired with a light-cure flowable resin composite; then, they were subjected to thermocycling and tested by shear bond strength. The data were analysed using three-way ANOVA, one-way ANOVA, and Tukey post hoc tests (α = 0.05).

Results

The shear bond strength was significantly higher for bis-acryl compared to polymethylmethacrylate materials (p < 0.001). In terms of aging conditions, shear bond strength was in the order of 75% ethanol/water solution < dry < water. The application of bonding agents significantly increased the shear bond strength of polymethylmethacrylate-based materials (p < 0.001). The difference between water and dry storage was insignificant (p = 0.558); however, storage in a 75% ethanol/water solution showed significantly lower values compared to both dry and water storage in most of experimental groups (p < 0.001). Polymethylmethacrylate-based materials mainly demonstrated adhesive failure, while bis-acryl materials predominantly showed cohesive failure.

Conclusion

The bond strength of a light-cure flowable resin composite is significantly higher with bis-acryl compared to that with polymethylmethacrylate-based substrates. Aging in water does not have a significant effect; however, the 75% ethanol/water solution tends to negatively affect repairability. The application of different bonding agents positively affects the repair strength, especially for polymethylmethacrylate-based substrates.

Computer-aided design and computer-aided manufacturing indirect versus direct composite restorations: A randomized clinical trial

OBJECTIVE

This study compared the clinical performance of large indirect restorations (IRs) versus direct restorations (DRs) in posterior teeth.

METHODS

Thirty subjects received two class II restorations (n = 60), one fabricated from a precured composite block (Grandio Blocs, VOCO) for the indirect technique (IT) and the other with light-cured composite (GrandioSO, VOCO) for the direct technique (DT). For IT, the restoration was created using the computer-aided design and computer-aided manufacturer (CAD/CAM) system. For DT, the material was applied light-cured by using a layering technique. All restorations were evaluated by using the World Dental Federation criteria.

RESULTS

Twenty-three subjects attended the 2-year recall, and 46 restorations were evaluated. No significant differences were detected between the techniques for most parameters analyzed (p > 0.05). For "color match" at 7 days and 6 months, better results were observed for the DT. In relation to the overall scores, all restorations were esthetically acceptable after 2 years, while 93.3% of DT and 90% of IT showed acceptable function. For biological scores, 96.67% of DRs and 100% of IRs was acceptable after 24 months. Considering all properties, the success rates were 93.3% for DRs and 90% for IRs.

CONCLUSIONS

After 2 years, both restorations presented similar and good clinical behavior for all the properties analyzed.

CLINICAL SIGNIFICANCE

Light-cured direct posterior composite restorations may perform similarly to indirect composite restorations made with precured CAD/CAM composite blocks up to 2 years.

Physicochemical and mechanical characterization of a fiber-reinforced composite used as frameworks of implant-supported prostheses

OBJECTIVES

To characterize the physicochemical and mechanical properties of a milled fiber-reinforced composite (FRC) for implant-supported fixed dental prostheses (FDPs).

METHODS

For FRC characterization, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction, Fourier-transformed infrared spectrometry, simultaneous thermogravimetric analysis and differential scanning calorimetry were performed. For fatigue testing, 3-unit FRC frameworks were fabricated with conventional (9 mm² connector area) and modified designs (12 mm² connector area and 2.5 mm-height lingual extension). A hybrid resin composite was veneered onto the frameworks. FDPs were subjected to step-stress accelerated-life fatigue testing until fracture or suspension. Use level probability Weibull curves at 300 N were plotted and the reliability for 100,000 cycles at 300, 600 and 800 N was calculated. Fractographic analysis was performed by stereomicroscope and SEM.

RESULTS

The FRC consisted of an epoxy resin (∼25%) matrix reinforced with inorganic particles and glass fibers (∼75%). Multi-layer continuous regular-geometry fibers were densely arranged in a parallel and bidirectional fashion in the resin matrix. Fatigue analysis demonstrated high probability of survival (99%) for FDPs at 300 N, irrespective of framework design. Conventional FDPs showed a progressive decrease in the reliability at 600 (84%) and 800 N (19%), whereas modified FDPs reliability significantly reduced only at 800 N (75%). The chief failure modes for FRC FDPs were cohesive fracture of the veneering composite on lower loads and adhesive fracture of the veneering composite at higher loads.

SIGNIFICANCE

Milled epoxy resin matrix reinforced with glass fibers composite resulted in high probability of survival in the implant-supported prosthesis scenario.

Development of 3D printed resin reinforced with modified ZrO2 nanoparticles for long-term provisional dental restorations

OBJECTIVE

To characterize and investigate efficacy of loading functionalized ZrO₂ nanoparticles in 3-dimensional (3D) printed acrylate ester-based resin subjected to accelerated aging in artificial saliva. As well as to evaluate the effect of ZrO₂ nanoparticle volume fraction addition on mechanical and physical properties of printed composite.

METHODS

Functionalized ZrO₂ nanoparticles were characterized using TEM and Raman spectroscopy. 3D printed dental resin was reinforced, with ZrO₂ nanoparticles, in the concentration range (0-5wt.%). The resulted nanocomposites, in term of structure and physical/mechanical properties were evaluated using different mechanical testing, microscopic and spectroscopic techniques.

RESULTS

ZrO₂ based nanocomposite was successful and formed composites were more ductile. Degree of conversion was significant at the highest level with blank resin and 1wt.%. Sorption revealed reduction associated with volume fraction significant to neat resin, however solubility indicated neat and 4wt.% had the lowest significant dissolution. Vickers represented critical positive correlation with filler content, while nanohardness and elasticity behaved symmetrically and had the maximum strength at 3wt.% addition. In addition, 3wt.% showed the highest fracture toughness and modulus. Improvement of flexural strength was significantly linked to filler concentration. Overall properties dramatically were enhanced after 3 months aging in artificial saliva, especially degree of conversion, microhardness, nanoindentation/elasticity, and flexural modulus. However, significant reduction was observed with flexural modulus and fracture toughness.

SIGNIFICANCE

The outcomes suggest that the newly developed 3D printed nanocomposites modified with ZrO₂ nanoparticle have the superior potential and efficacy as long-term provisional dental restoration materials.

Fracture Strength of Interim CAD/CAM and Conventional Partial Fixed Dental Prostheses

PURPOSE

 To compare the fracture strength of three-unit provisional partial fixed dental prostheses (FDPs) fabricated by an indirect-direct technique from poly(methylmethacrylate) (PMMA) through digital and conventional workflows, and FDPs fabricated by a direct technique using Bisacryl (BisA) and externally reinforced BisA.

MATERIALS AND METHODS

 Forty partially edentulous typodonts with a missing mandibular left first molar and standard preparations on mandibular left second premolar and molar were used to fabricate three-unit provisional FDPs. Two materials and two techniques were used to fabricate a total of forty provisional FDPs: (1) BisA; (2) BisA reinforced with glass fiber strips [BisA-GFR]; (3) conventionally fabricated PMMA shell relined with PMMA [C-PMMA]; (4) CAD/CAM fabricated PMMA shell relined with PMMA [CAD/CAM-PMMA]. Provisional FDPs were then luted onto the preparations using a temporary cement. Specimens were mounted onto a chewing simulator; 20,000 cycles of 70 N forces were applied under 25°C distilled water. Specimens were then loaded to fracture using a universal testing machine (The Dillion Quantrol TC2i; Mecmesin) with a crosshead speed of 2 mm/min. One-way ANOVA, followed by Tukey post hoc test, was used to assess the effect of production technique on the fracture strength of the provisional FPDs (α = 0.5).

RESULTS

 Mean fracture strengths recorded for the CAD/CAM-PMMA, C-PMMA, BisA, and BisA-GFR groups were 520 N, 448 N, 245 N, and 169 N, respectively. PMMA groups had significantly (p < 0.0001; F = 24.40) higher fracture strength compared to Bisacryl groups.

CONCLUSION

 When high occlusal forces are expected, provisional FDPs fabricated with PMMA using the indirect-direct technique are recommended, irrespective of CAD/CAM or conventional workflow.

Review on Development and Dental Applications of Polyetheretherketone-Based Biomaterials and Restorations

Polyetheretherketone (PEEK) is an important high-performance thermoplastic. Its excellent strength, stiffness, toughness, fatigue resistance, biocompatibility, chemical stability and radiolucency have made PEEK attractive in dental and orthopedic applications. However, PEEK has an inherently hydrophobic and chemically inert surface, which has restricted its widespread use in clinical applications, especially in bonding with dental resin composites. Cutting edge research on novel methods to improve PEEK applications in dentistry, including oral implant, prosthodontics and orthodontics, is reviewed in this article. In addition, this article also discusses innovative surface modifications of PEEK, which are a focus area of active investigations. Furthermore, this article also discusses the necessary future studies and clinical trials for the use of PEEK in the human oral environment to investigate its feasibility and long-term performance.

Cytotoxicity of acrylic resin-based materials used to fabricate interim crowns

STATEMENT OF PROBLEM

If the components in the acrylic resins used to fabricate interim crows are cytotoxic, they can interfere with the integrity of the adjacent periodontal tissue and the dentin-pulp complex.

PURPOSE

The purpose of this in vitro study was to assess the cytotoxicity of resin-based materials used to prepare interim crowns.

MATERIAL AND METHODS

The following materials were used in this study: CAR, conventional acrylic resin powder and liquid; BR, bis-acrylic resin; and PAR, pressed acrylic resin of the CAD-CAM type. Glass disks were used as the control (Co). Oral epithelial cells (NOK) were seeded on glass disks and standardized disks prepared with the resins under study. After incubation for 24 hours, the cells were analyzed for viability (Alamar Blue and Live or Dead), adhesion, and morphology (SEM and fluorescence), as well as epidermal growth factor synthesis (EGF-ELISA). The surface roughness (Ra) of test specimens was evaluated under a confocal microscope. The data were submitted to ANOVA and the Tukey HSD statistical tests (α=.05).

RESULTS

The highest Ra value was observed in BR in comparison with CAR, PAR, and Co (P<.05). The highest viability, adhesion, and EGF synthesis values were determined for the cells in contact with PAR (P<.001).

CONCLUSIONS

The computer-aided design and computer-aided manufacturing (CAD-CAM)-type resin favored adhesion, metabolism, and epithelial cell proliferation, and it was therefore considered cytocompatible.

Randomized clinical trial of a conventional and a digital workflow for the fabrication of interim crowns: An evaluation of treatment efficiency, fit, and the effect of clinician experience

STATEMENT OF PROBLEM

Limited information is available regarding the fabrication of tooth-supported interim single crowns (SCs) with either a digital or a conventional workflow.

PURPOSE

The purpose of this randomized clinical trial was to compare the time efficiency and fit of interim crowns fabricated by using either a digital or a conventional workflow.

MATERIAL AND METHODS

Forty participants in need of posterior tooth-supported SCs were enrolled and randomly allocated to either the digital or conventional group. In the digital group, the interim SCs were fabricated by using digital sextant scans and computer-aided design and computer-aided manufacturing (CAD-CAM) technology without definitive casts. The conventional group included conventional impressions and direct fabrication of the interim restorations intraorally. Five experienced and 5 less experienced clinicians were randomly assigned to fabricate the interim SCs. The total fabrication time (laboratory and clinical) was recorded for time efficiency. The fit assessment included marginal fit, proximal contact, occlusal contact, and crown morphology. The evaluated parameters were analyzed with the Mann-Whitney U Test (α=.05).

RESULTS

The digital workflow required significantly less total fabrication time (laboratory and clinical) than the conventional workflow (P<.001). The less-experienced clinicians needed longer clinical time with the conventional workflow than the experienced ones (P=.023). In contrast, the laboratory time and total fabrication time were shorter for less-experienced clinicians using the digital workflow (P=.005 and P=.015). The interim SCs fabricated with the digital workflow had significantly better fit and occlusal contacts than those fabricated with the conventional workflow (P=.005 and P<.001). With the digital workflow, the interim SCs made by less-experienced clinicians were of the same quality as those made by experienced clinicians. When using the conventional workflow, the fit of the experienced clinicians was significantly better than that of the less-experienced clinicians.

CONCLUSIONS

The interim SCs fabricated with a digital workflow required a shorter fabrication time and resulted in better fit than those fabricated with a conventional workflow, especially for less-experienced clinicians.

Bracket bonding to polymethylmethacrylate-based materials for computer-aided design/manufacture of temporary restorations: Influence of mechanical treatment and chemical treatment with universal adhesives

Objective

To assess shear bond strength and failure mode (Adhesive Remnant Index, ARI) of orthodontic brackets bonded to polymethylmethacrylate (PMMA) blocks for computer-aided design/manufacture (CAD/CAM) fabrication of temporary restorations, following substrate chemical or mechanical treatment.

Methods

Two types of PMMA blocks were tested: CAD-Temp® (VITA) and Telio® CAD (Ivoclar-Vivadent). The substrate was roughened with 320-grit sandpaper, simulating a fine-grit diamond bur. Two universal adhesives, Scotchbond Universal Adhesive (SU) and Assure Plus (AP), and a conventional adhesive, Transbond XT Primer (XTP; control), were used in combination with Transbond XT Paste to bond the brackets. Six experimental groups were formed: (1) CADTemp®/SU; (2) CAD-Temp®/AP; (3) CAD-Temp®/XTP; (4) Telio® CAD/SU; (5) Telio® CAD/AP; (6) Telio® CAD/XTP. Shear bond strength and ARI were assessed. On 1 extra block for each PMMA-based material surfaces were roughened with 180-grit sandpaper, simulating a normal/medium-grit (100 mm) diamond bur, and brackets were bonded. Shear bond strengths and ARI scores were compared with those of groups 3, 6.

Results

On CAD-Temp® significantly higher bracket bond strengths than on Telio® CAD were recorded. With XTP significantly lower levels of adhesion were reached than using SU or AP. Roughening with a coarser bur resulted in a significant increase in adhesion.

Conclusions

Bracket bonding to CAD/CAM PMMA can be promoted by grinding the substrate with a normal/medium-grit bur or by coating the intact surface with universal adhesives. With appropriate pretreatments, bracket adhesion to CAD/CAM PMMA temporary restorations can be enhanced to clinically satisfactory levels.

Effect of surface treatments on the bond strength of indirect resin composite to resin matrix ceramics

PURPOSE

The purpose of this study was to evaluate the shear bond strength (SBS) of an indirect resin composite (IRC) to the various resin matrix ceramic (RMC) blocks using different surface treatments.

MATERIALS AND METHODS

Ninety-nine cubic RMC specimens consisting of a resin nanoceramic (RNC), a polymer-infiltrated hybrid ceramic (PIHC), and a flexible hybrid ceramic (FHC) were divided randomly into three surface treatment subgroups (n = 11). In the experimental groups, untreated (Cnt), tribochemical silica coating (Tbc), and Neodymium-Doped Yttrium Aluminum Garnet (Nd:YAG) laser irradiation (Lsr) with 3 W (150 mJ/pulse, 20 Hz for 20 sec.) were used as surface treatments. An indirect composite resin (IRC) was layered with a disc-shape mold (2 × 3 mm) onto the treated-ceramic surfaces and the specimens submitted to thermal cycling (6000 cycles, 5 – 55℃). The SBS test of specimens was performed using a universal testing machine and the specimens were examined with a scanning electron microscope to determine the failure mode. Data were statistically analyzed with two-way analysis of variance (ANOVA) and Tukey HSD test (α=.05).

RESULTS

According to the two-way ANOVA, only the surface treatment parameter was statistically significant (P<.05) on the SBS of IRC to RMC. The SBS values of Lsr-applied RMC groups were significantly higher than Cnt groups for each RMC material, (P<.05). Significant differences were also determined between Tbc surface treatment applied and untreated (Cnt) PIHC materials (P=.039).

CONCLUSION

For promoting a reliable bond strength during characterization of RMC with IRC, Nd:YAG laser or Tbc surface treatment technique should be used, putting in consideration the microstructure and composition of RMC materials and appropriate parameters for each material.

Fracture load of 3D-printed fixed dental prostheses compared with milled and conventionally fabricated ones: the impact of resin material, build direction, post-curing, and artificial aging-an in vitro study

OBJECTIVE

To investigate the impact of 3D print material, build direction, post-curing, and artificial aging on fracture load of fixed dental prostheses (FDPs).

MATERIALS AND METHODS

Three-unit FDPs were 3D-printed using experimental resin (EXP), NextDent C&B (CB), Freeprint temp (FT), and 3Delta temp (DT). In the first part, the impacts of build direction and artificial aging were tested. FDPs were manufactured with their long-axis positioned either occlusal, buccal, or distal to the printer's platform. Fracture load was measured after artificial aging (H₂O: 21 days, 37 °C). In the second part, the impact of post-curing was tested. FDPs were post-cured using Labolight DUO, Otoflash G171, and LC-3DPrint Box. While the positive control group was milled from TelioCAD (TC), the negative control group was fabricated from a conventional interim material Luxatemp (LT). The measured initial fracture loads were compared with those after artificial aging. Each subgroup contained 15 specimens. Data were analyzed using Kolmogorov-Smirnov test, one-way ANOVA followed by Scheffé post hoc test, t test, Kruskal-Wallis test, and Mann-Whitney U test (p < 0.05). The univariate ANOVA with partial eta squared (η_P²) was used to analyze the impact of test parameters on fracture load.

RESULTS

Specimens manufactured with their long-axis positioned distal to the printer's platform showed higher fracture load than occlusal ones (p = 0.049). The highest values were observed for CB, followed by DT (p < 0.001). EXP showed the lowest values, followed by FT (p < 0.001). After artificial aging, a decrease of fracture load for EXP (p < 0.001) and DT (p < 0.001) was observed. The highest impact on values was exerted by interactions between 3D print material and post-curing unit (η_P² = 0.233, p < 0.001), followed by the 3D print material (η_P² = 0.219, p < 0.001) and curing device (η_P² = 0.108, p < 0.001).

CONCLUSIONS

Build direction, post-curing, artificial aging, and material have an impact on the mechanical stability of printed FDPs.

CLINICAL RELEVANCE

The correct post-curing strategy is mandatory to ensure mechanical stability of 3D-printed FDPs. Additively manufactured FDPs are more prone to artificial aging than conventionally fabricated ones.

Light transmittance of CAD/CAM ceramics with different shades and thicknesses and microhardness of the underlying light-cured resin cement

Objectives

The aim of this in vitro study was to evaluate the effects of the thickness and shade of 3 types of computer-aided design/computer-aided manufacturing (CAD/CAM) materials.

Materials and Methods

A total of 120 specimens of 2 shades (A1 and A3) and 2 thicknesses (1 and 2 mm) were fabricated using VITA Mark II (VM; VITA Zahnfabrik), IPS e.max CAD (IE; IvoclarVivadent), and VITA Suprinity (VS; VITA Zahnfabrik) (n = 10 per subgroup). The amount of light transmission through the ceramic specimens was measured by a radiometer (Optilux, Kerr). Light-cured resin cement samples (Choice 2, Bisco) were fabricated in a Teflon mold and activated through the various ceramics with different shades and thicknesses using an LED unit (Bluephase, IvoclarVivadent). In the control group, the resin cement sample was directly light-cured without any ceramic. Vickers microhardness indentations were made on the resin surfaces (KoopaPazhoohesh) after 24 hours of dark storage in a 37°C incubator. Data were analyzed using analysis of variance followed by the Tukey post hoc test (α = 0.05).

Results

Ceramic thickness and shade had significant effects on light transmission and the microhardness of all specimens (p < 0.05). The mean values of light transmittance and microhardness of the resin cement in the VM group were significantly higher than those observed in the IE and VS groups. The lowest microhardness was observed in the VS group, due to the lowest level of light transmission (p < 0.05).

Conclusion

Greater thickness and darker shades of the 3 types of CAD/CAM ceramics significantly decreased the microhardness of the underlying resin cement.

Bonding to new CAD/CAM resin composites: influence of air abrasion and conditioning agents as pretreatment strategy

OBJECTIVES

Because of their industrially standardized process of manufacturing, CAD/CAM resin composites show a high degree of conversion, making a reliable bond difficult to achieve.

PURPOSE

The purpose of this experiment was to investigate the tensile bond strength (TBS) of luting composite to CAD/CAM resin composite materials as influenced by air abrasion and pretreatment strategies.

MATERIAL AND METHODS

The treatment factors of the present study were (1) brand of the CAD/CAM resin composite (Brilliant Crios [Coltene/Whaledent], Cerasmart [GC Europe], Shofu Block HC [Shofu], and Lava Ultimate [3M]); (2) air abrasion vs. no air abrasion; and (3) pretreatment using a silane primer (Clearfil Ceramic Primer, Kuraray) vs. a resin primer (One Coat 7 Universal, Coltene/Whaledent). Subsequently, luting composite (DuoCem, Coltene/Whaledent) was polymerized onto the substrate surface using a mold. For each combination of the levels of the three treatment factors (4 (materials) × 2 (air abrasion vs. no air abrasion; resin) × 2 (primer vs. silane primer)), n = 15, specimens were prepared. After 24 h of water storage at 37 °C and 5000 thermo-cycles (5/55 °C), TBS was measured and failure types were examined. The resulting data was analyzed using Kaplan-Meier estimates of the cumulative failure distribution function with Breslow-Gehan tests and non-parametric ANOVA (Kruskal-Wallis test) followed by the multiple pairwise Mann-Whitney U test with α-error adjustment using the Benjamini-Hochberg procedure and chi-square test (p < 0.05).

RESULTS

The additional air abrasion step increased TBS values and lowered failure rates. Specimens pretreated using a resin primer showed significantly higher TBS and lower failure rates than those pretreated using a silane primer. The highest failure rates were observed for groups pretreated with a silane primer. Within the Shofu Block HC group, all specimens without air abrasion and pretreatment with a silane primer debonded during the aging procedure.

CONCLUSIONS

Before fixation of CAD/CAM resin composites, the restorations should be air abraded and pretreated using a resin primer containing methyl-methacrylate to successfully bond to the luting composite. The pretreatment of the CAD/CAM resin composite using merely a silane primer results in deficient adhesion.

CLINICAL RELEVANCE

For a reliable bond of CAD/CAM resin composites to the luting composite, air abrasion and a special pretreatment strategy are necessary in order to achieve promising long-term results.

Blue-Light Transmittance of Esthetic Monolithic CAD/CAM Materials With Respect to Their Composition, Thickness, and Curing Conditions

Determining the amount of blue light (360-540nm) passing through nine monolithic computer-aided design/computer-aided manufacturing (CAD/CAM) materials depends on material thickness, initial irradiance, and the distance between the curing unit and the specimen's surface. A total of 180 specimens of two thicknesses (1 mm and 2 mm, n=10/subgroup) were fabricated from TelioCAD, VITA CAD-Temp (VCT), experimental nanocomposite, LAVA Ultimate (LU), VITA ENAMIC (VE), VITA MarkII (VM), IPS EmpressCAD (IEC), IPS e.maxCAD (IEM), and CELTRA DUO (CD). The irradiance passing through the CAD/CAM materials and thicknesses was measured using a light-emitting-diode curing unit with standard-power, high-power, and plasma modes by means of a USB4000 spectrometer. The curing unit was placed directly on the specimen's surface at 2- and 4-mm distances from the specimen's surface. Data were analyzed using a multivariate analysis and one-way analysis of variance with the post hoc Scheffé test (p&lt;0.05). The highest transmitted irradiance was measured for VM and LU, followed by VCT and IEC, while the lowest values showed VE, followed by IEM and CD. The highest transmitted irradiance was recorded by exposing the material to the plasma mode, followed by the high- and standard-power modes. The measured irradiance was decreased by increasing the specimen's thickness from 1 to 2 mm. Fewer differences were measured when the curing unit was placed at 0 or 2 mm from the specimen's surface, and the irradiance passing through the specimens was lower at a distance of 4 mm.

Effects of air abrasion with alumina or glass beads on surface characteristics of CAD/CAM composite materials and the bond strength of resin cements

Objective

The study aimed to evaluate effects of air abrasion with alumina or glass beads on bond strengths of resin cements to CAD/CAM composite materials.

Material and Methods

CAD/CAM composite block materials [Cerasmart (CS) and Block HC (BHC)] were pretreated as follows: (a) no treatment (None), (b) application of a ceramic primer (CP), (c) alumina-blasting at 0.2 MPa (AB), (d) AB followed by CP (AB+CP), and (e) glass-beads blasting at 0.4 MPa (GBB) followed by CP (GBB+CP). The composite specimens were bonded to resin composite disks using resin cements [G-CEM Cerasmart (GCCS) and ResiCem (RC)]. The bond strengths after 24 h (TC 0) and after thermal cycling (TC 10,000 at 4–60°C) were measured by shear tests. Three-way ANOVA and the Tukey compromise post hoc tests were used to analyze statistically significant differences between groups (α=0.05).

Results

For both CAD/CAM composite materials, the None group exhibited a significant decrease in bond strength after TC 10,000 (p<0.05). AB showed significantly higher bond strength after TC 10,000 than the None group, while CP did not (p<0.05). GBB exhibited smaller surface defects than did AB; however, their surface roughnesses were not significantly different (p>0.05). The AB+CP group showed a significantly higher bond strength after TC 10,000 than did the AB group for RC (p<0.05), but not for GCCS. The GBB+CP group showed the highest bond strength for both thermal cyclings (p<0.05).

Conclusions

Air abrasion with glass beads was more effective in increasing bond durability between the resin cements and CAD/CAM composite materials than was using an alumina powder and a CP.

CAD/CAM Polymer vs Direct Composite Resin Core Buildups for Endodontically Treated Molars Without Ferrule

OBJECTIVES

The aim of this study was to investigate the restoration of broken-down endodontically treated molars without ferrule effect using glass ceramic crowns on different composite resin core buildups.

METHODS AND MATERIALS

Forty-five decoronated endodontically treated teeth (no ferrule) were restored with a semidirect buildup using an experimental computer-aided design/computer-aided manufacturing (CAD/CAM) high-performance polymer (HPP group) or with light-curing composite core buildups of Tetric EvoCeram with (TECP group) or without (TEC group) a glass-fiber-reinforced post. All teeth were prepared to receive bonded glass ceramic crowns (Empress CAD luted with Variolink II) and were subjected to accelerated fatigue testing. Cyclic isometric loading was applied to the palatal cusp at an angle of 30° and a frequency of 5 Hz, beginning with a load of 200 N (×5000 cycles) and followed by stages of 400, 600, 800, 1000, 1200, and 1400 N at a maximum of 30,000 cycles each. Specimens were loaded until failure or to a maximum of 185,000 cycles. Groups were compared using the life-table survival analysis (log rank test at p=0.05). Average fracture loads and number of survived cycles were compared with one-way analysis of variance (Scheffé post hoc at p=0.05).

RESULTS

None of the tested specimen withstood all 185,000 load cycles. There was a significant difference in mean fracture load, survived cycles, and survival; the HPP group (fracture load 975.27N±182.74) was significantly higher than the TEC (716.87N±133.43; p=0.001) and TECP (745.67±156.34; p=0.001) groups, and the TEC and TECP groups showed no difference (p=0.884). Specimens in the TECP group were affected by an initial failure phenomenon (wide gap at the margin between the buildup/crown assembly and the root).

CONCLUSIONS

Semidirect core buildup made from high-performance polymer enhanced the performance of all-ceramic leucite-reinforced glass ceramic crowns compared with direct light-curing composite resin buildups. The use of a fiber-reinforced post system did not influence the fatigue strength of all-ceramic crowns.

Comparison of interim restorations fabricated by CAD/CAM with those fabricated manually

STATEMENT OF PROBLEM

Interim restorations represent an essential treatment step; however, the optimal resin material for long-term interim restorations requires investigation.

PURPOSE

The purpose of this in vitro study was to compare the color stability, water sorption, wear resistance, surface hardness, fracture resistance, and microleakage of computer-aided design/computer-aided manufacturing-(CAD/CAM) fabricated interim restorations with those of manually fabricated interim restorations.

MATERIAL AND METHODS

Epoxy replicas were made from a prepared maxillary first premolar. On the replicas, interim crowns were fabricated and divided into the following groups: CAD/CAM poly(methyl methacrylate) (PMMA) blocks (CC), autopolymerizing temporary resin (AP), automix temporary resin (AM), and thermoplastic resin (TP). After cementation, all specimens were subjected to thermocycling and dynamic fatigue. The CIE Laboratory color coordinates were then recorded before and after immersion in coffee, tea, carbonated cola, and red wine. Water sorption was evaluated by using an immersion technique. Wear resistance was measured in a surface abrasion device. Vickers microhardness was measured on polished specimens. Fracture resistance was evaluated by axial loading with a universal testing machine. Marginal dye penetration was evaluated by sectioning the interim restorations after immersion in methylene blue (α=.05).

RESULTS

Colorimetric analysis revealed a large degree of color alteration (ΔE) in the manually fabricated interim restorations: AP = ΔE of 6.7 ±2); AM = ΔE of 7.1 ±1.5), and TP = ΔE of =5.4 ±3.1. The CC group demonstrated color stability (ΔE=2.1 ±0.2). CAD/CAM interim restorations demonstrated significantly lower water sorption, higher wear resistance, higher surface hardness, and significantly higher fracture resistance (1289±56N) compared with manually fabricated interim restorations (AP=996 ±45, AM=899 ±37, and TP=1179 ±41). The stereomicroscopic examination of sectioned specimens demonstrated the absence of dye penetration in all tested specimens.

CONCLUSIONS

CAD/CAM interim crowns presented stable physical and mechanical properties and may be used for long-term interim restorations.

Repairability of CAD/CAM high-density PMMA- and composite-based polymers

OBJECTIVE

The study aimed to analyse the shear bond strength of computer-aided design and computer-aided manufacturing (CAD/CAM) polymethyl methacrylate (PMMA)- and composite-based polymer materials repaired with a conventional methacrylate-based composite after different surface pretreatments.

METHODS

Each 48 specimens was prepared from six different CAD/CAM polymer materials (Ambarino high-class, artBloc Temp, CAD-Temp, Lava Ultimate, Telio CAD, Everest C-Temp) and a conventional dimethacrylate-based composite (Filtek Supreme XTE, control) and aged by thermal cycling (5000 cycles, 5-55 °C). The surfaces were left untreated or were pretreated by mechanical roughening, aluminium oxide air abrasion or silica coating/silanization (each subgroup n = 12). The surfaces were further conditioned with an etch&rinse adhesive (OptiBond FL) before the repair composite (Filtek Supreme XTE) was adhered to the surface. After further thermal cycling, shear bond strength was tested, and failure modes were assessed. Shear bond strength was statistically analysed by two- and one-way ANOVAs and Weibull statistics, failure mode by chi(2) test (p ≤ 0.05).

RESULTS

Shear bond strength was highest for silica coating/silanization > aluminium oxide air abrasion = mechanical roughening > no surface pretreatment. Independently of the repair pretreatment, highest bond strength values were observed in the control group and for the composite-based Everest C-Temp and Ambarino high-class, while PMMA-based materials (artBloc Temp, CAD-Temp and Telio CAD) presented significantly lowest values. For all materials, repair without any surface pretreatment resulted in adhesive failures only, which mostly were reduced when surface pretreatment was performed.

CONCLUSIONS

Repair of CAD/CAM high-density polymers requires surface pretreatment prior to adhesive and composite application. However, four out of six of the tested CAD/CAM materials did not achieve the repair bond strength of a conventional dimethacrylate-based composite.

CLINICAL RELEVANCE

Repair of PMMA- and composite-based polymers can be achieved by surface pretreatment followed by application of an adhesive and a conventional methacrylate-based composite.

Three-unit reinforced polyetheretherketone composite FDPs: influence of fabrication method on load-bearing capacity and failure types

To investigate the influence of different fabrication methods of three-unit reinforced polyetheretherketone composite (PEEK/C) fixed dental prostheses (FDPs) on fracture load. Forty-five three-unit anatomically supported PEEK/C FDPs were fabricated as follows: i. milled using a CAD/CAM system from an industrially fabricated PEEK/C blank, ii. pressed from industrially fabricated PEEK/C pellets, and iii. pressed from granular PEEK/C. Fracture load was measured and data were statistically analysed (p<0.05). CAD/CAM fabricated FDPs (2,354 N) presented a higher mean fracture load than those pressed from granular PEEK/C material (1,738 N) (p<0.001). CAD/CAM milled FDPs and those pressed from PEEK/C-pellets showed spontaneous and brittle fractures near the pontic without deformation of the FDP. In contrast, granulate pressed FDPs showed some plastic deformation without fracture. CAD/CAM fabricated FDPs, and FDPs pressed from PEEK/C pellets showed higher Weibull moduli compared to FDPs pressed in granular form. Industrial pre-pressing of blanks (CAD/CAM/pellet) increased the stability and reliability of PEEK restorations.

Effect of different adhesives combined with two resin composite cements on shear bond strength to polymeric CAD/CAM materials

This study tested the impact of different adhesives and resin composite cements on shear bond strength (SBS) to polymethyl methacrylate (PMMA)- and composite-based CAD/CAM materials. SBS specimens were fabricated and divided into five main groups (n=30/group) subject to conditioning: 1. Monobond Plus/Heliobond (MH), 2. Visio.link (VL), 3. Ambarino P60 (AM), 4. exp. VP connect (VP), and 5. no conditioning-control group (CG). All cemented specimens using a. Clearfil SA Cement and b. Variolink II were stored in distilled water for 24 h at 37 °C. Additionally, one half of the specimens were thermocycled for 5,000 cycles (5 °C/55 °C, dwell time 20 s). SBS was measured; data were analyzed using descriptive statistics, four- and one-way ANOVA, unpaired two-sample t-test and Chi(2)-test. CAD/CAM materials without additional adhesives showed no bond to resin composite cements. Highest SBS showed VL with Variolink II on composite-based material, before and after thermocycling.

The effect of different pretreatment methods of PMMA-based crowns on the long-term tensile bond strength to dentin abutments

OBJECTIVES

The objective of the study was to test the effect of different pretreatments on tensile bond strength (TBS) of adhesively bonded CAD/CAM-generated polymethyl methacrylate (PMMA) crowns to dentin.

MATERIALS AND METHODS

Two hundred human molars were prepared and divided into 20 groups (n = 10/group). PMMA crowns were pretreated thusly: Monobond Plus/Heliobond (MH), Visio.link (VL), Ambarino P60 (AM), VP connect (VP), and nontreated as control groups (CG). Two resin cements were used for cementation of crowns: Clearfil SA Cement (CSA) and Variolink II (VAR). TBS was measured initially (24 h water storage, 37 °C) and after aging (5,000 thermal cycles, 5/55 °C). TBS was analyzed using one-way ANOVA with Scheffé post hoc, unpaired Student t, Mann-Whitney U, Kruskal-Wallis H, and chi-squared tests.

RESULTS

Within CSA, pretreatment with MH and VL showed higher initial TBS compared with AM-treated groups. All other groups showed no statistical differences. For MH, VL, AM, and VP in combination with CSA, a negative impact of aging was observed (p < 0.001), whereas in all VAR groups, no impact was measured. Pretreatment with MH (p = 0.001) and VP (p = 0.008) presented higher initial TBS for CSA than for VAR. After aging, MH (p = 0.025) and VL (p = 0.034) cemented with VAR showed higher results than CSA.

CONCLUSIONS

All tested groups showed very low TBS values. Pretreatments with MH, VL, and VP have minimally improved the tensile strength after aging.

CLINICAL RELEVANCE

Although the tensile strength results were low, crowns adhesively cemented with pretreatments with MH, VL, and VP showed, after aging, a higher tensile strength than nontreated groups.

Two-body wear rate of CAD/CAM resin blocks and their enamel antagonists

STATEMENT OF PROBLEM

Computer-aided design and computer-aided manufacturing (CAD/CAM) resins exhibit good mechanical properties and can be used as long-term restorations. The wear rate of such resins and their enamel antagonists is unknown.

PURPOSE

The purpose of this study was to test and compare the 2-body wear rate of CAD/CAM resin blocks.

MATERIAL AND METHODS

Wear specimens (N=42, n=6) were made from 5 CAD/CAM resins: ZENO PMMA (ZP), artBloc Temp (AT), Telio CAD (TC), Blanc High-class (HC), CAD-Temp (CT); 1 manually polymerized resin: Integral esthetic press (negative control group, IEP); and 1 glass-ceramic: VITA Mark II (positive control group, VM2). The specimens for the wear resistance were aged in a thermomechanical loading machine (49 N, 1.67 Hz, 5/50°C) with human enamel antagonists. The material loss of all specimens before, during, and after aging was evaluated with a 3DS profilometer. The measured material loss data of all tested groups were statistically evaluated with linear mixed model analysis (a=.05).

RESULTS

Manually polymerized resin showed significantly higher material wear (P<.001) than all other tested groups. Glass-ceramic showed significantly lower wear values (P<.001) than CAD/CAM resins ZP, AT, HC, CT, and IES. CAD/CAM resin TC was not significantly different from the positive control group. Glass-ceramic showed the highest enamel wear values (P<.001) of all tested resins. No differences were found in the enamel wear among all resins. The glass-ceramic group showed damage in the form of cracks on the worn enamel surface in 50% of specimens.

CONCLUSIONS

CAD/CAM resins showed lower wear rates than those conventionally polymerized. Only one CAD/CAM resin, TC, presented material wear values comparable with glass-ceramic. The tested glass-ceramic developed cracks in the enamel antagonist and showed the highest enamel wear values of all other tested groups.

Long-term tensile bond strength of differently cemented nanocomposite CAD/CAM crowns on dentin abutment

OBJECTIVES

To test the tensile bond strength of luted composite computer aided design/computer aided manufacturing (CAD/CAM) crowns after use of different adhesive systems combined with different resin composite cements on dentin abutments.

METHODS

Human molars (n=200) were embedded in acrylic resin, prepared in a standardized manner and divided into 20 groups (n=10). The crowns were treated as follows: (i) Monobond Plus/Heliobond (MH), (ii) Ambarino P60 (AM), (iii) Visio.link (VL), (iv) VP connect (VP), and (v) non-treated as control groups (CG) and luted with Variolink II (VAR) or Clearfil SA Cement (CSA). Tensile bond strength (TBS) was measured initially (24h water, 37°C) and after aging (5000 thermal cycles, 5/55°C). The failure types were evaluated after debonding. TBS values were analyzed using three-way and one-way ANOVA, followed by post hoc Scheffé-test, and two-sample Student's t-tests.

RESULTS

Among VAR and after aging, CG presented significantly higher TBS (p=0.007) than groups treated with MH, AM and VP. Other groups showed no impact of pre-treatment. A decrease of TBS values after thermal aging was observed within CSA: CG (p=0.002), MH (p<0.001), VL (p<0.001), AM (p=0.002), VP (p<0.001) and within VAR: MH (p=0.002) and AM (p=0.014). Groups cemented with VAR showed significantly higher TBS then groups cemented with CSA: non-aged groups: CG (p<0.001), and after thermal aging: CG (p=0.003), MH (p<0.001), VL (p=0.005), VP (p=0.010).

SIGNIFICANCE

According to the study results nano-composite CAD/CAM crowns should be cemented with VAR. Pre-treatment is not necessary if the tested resin composite cements are used.

Adhesion of veneering resins to polymethylmethacrylate-based CAD/CAM polymers after various surface conditioning methods

OBJECTIVES

The aims of this study were to test whether the bond strength of a hybrid composite and a PMMA-based veneer to CAD/CAM polymers would improve after pre-treatment and to evaluate the failure types after debonding.

MATERIALS AND METHODS

Three types of PMMA-based (CAD-Temp, artBloc Temp and TelioCAD) CAD/CAM blocks were obtained (N = 360, n = 15 per test group). They were divided into four groups to be conditioned with the following methods: (a) no-treatment, (b) air-abrasion (50 μm Al2O3), (c) air-abrasion (50 μm Al2O3) + MPS-Silane (Monobond S) + Adhesive resin (StickResin) (for Gradia)/MMA (for Integral Esthetic Press) application, (d) Silica coating and silanization (CoJet-System). The conditioned surfaces were veneered with a hybrid composite (Gradia) or a PMMA-based resin (Integral esthetic press). After water storage (1 week, 37°C), the bond strength was measured. Data were analyzed using 3-way ANOVA and post-hoc Scheffé test (α = 0.05).

RESULTS

Surface-conditioning method, veneer type and CAD/CAM polymers significantly affected the results. Hybrid composite did not bond to non-conditioned CAD/CAM polymers. Regardless of the conditioning method, PMMA-based resin showed significantly higher bond strength to all CAD/CAM polymers compared to hybrid composite. Air-abrasion increased the bond strength in all tested groups. Additional silane application after air-abrasion did not significantly increase the bond strength of hybrid composite. While exclusively adhesive failures were observed between the hybrid composite and the CAD/CAM polymers, PMMA veneer demonstrated cohesive failures in the CAD/CAM polymers.

CONCLUSION

CAD/CAM polymers could be veneered with only a PMMA-based veneer with and without air-abrasion.

Impact of plasma treatment of PMMA-based CAD/CAM blanks on surface properties as well as on adhesion to self-adhesive resin composite cements

OBJECTIVES

To test surface energy, roughness and tensile bond strength (TBS) to self-adhesive resin composite cements without/with plasma treatment combined with different conditioning methods of PMMA-based CAD/CAM blocks.

METHODS

PMMA specimens (10mm×10mm×2mm) were fabricated (N=260), polished and air-abraded (50μm Al2O3, 5s, 0.05MPa). Twenty specimens were selected for surface energy and roughness measurements (without/with plasma n=10 per group). The remaining specimens (n=240) were used for TBS testing without/with plasma treatment and following conditioning methods (n=20 per test group): (i) without conditioning, (ii) Visio.link, (iii) VP connect and luted with Clearfil SA Cement and RelyX Unicem Automix. Specimens were aged (24h 37°C water+5000 thermal cycles, 5°C/55°C), TBS was measured and failure types were assessed. Data were analyzed using descriptive statistics, Mann-Whitney-U and Kruskal-Wallis-H tests, unpaired t-test, Chi(2) and the Spearman correlation test.

RESULTS

Plasma treatment of PMMA increased the surface energy significantly (p<0.001) but had no impact on the surface roughness (p=0.718). Groups without plasma treatment showed higher TBS than plasma treated groups (p<0.001 to p=0.011), except PMMA conditioned with VP connect and luted using RelyX Unicem Automix (p=0.03). Clearfil SA Cement showed higher TBS compared to RelyX Unicem Automix, except for groups conditioned with Visio.link. Both resin composite cements showed the highest TBS for groups conditioned with Visio.link. Also, among Clearfil SA Cement, conditioning with VP connect showed comparable TBS to Visio.link.

SIGNIFICANCE

Plasma treatment of PMMA did not increase the adhesion to self-adhesive resin composite cements.

Load-bearing capacity of CAD/CAM milled polymeric three-unit fixed dental prostheses: effect of aging regimens

OBJECTIVE

This study tested the fracture load of milled and conventionally fabricated polymeric and glass-ceramic three-unit fixed dental prostheses (FDPs) after aging.

MATERIALS AND METHODS

FDPs were fabricated (N = 1,050) from four computer-aided design and computer-aided manufacturing (CAD/CAM) resins: (1) AT (artBlock Temp); (2) TC (Telio CAD); (3) ZP (ZENO PMMA); (4) CT (CAD-Temp); two conventionally fabricated resins, (5) IES (integral esthetic press), (6) CMK (CronMix K), and a glass-ceramic (control) (7) PG (IMAGINE PressX). Specimens of each group were tested immediately after fabrication (n = 15 per material). Seventy-five FDPs per material type were stored in artificial saliva (37°C) and 15 of them were randomly selected after aging (1, 7, 28, 90, and 180 days) for fracture load measurement. The remaining specimens (n = 60 per material) were subjected to chewing simulation (×120.000-1.200.000, 49 N, 5°C/50°C). The data were analyzed using two-way and one-way ANOVA followed by Scheffé test.

RESULTS

The interactions between FDP materials and aging time in both storage media showed a significant impact on the results (p < 0.001). Among saliva storage groups, TC and ZP showed the highest, and PG the lowest fracture load (p < 0.05). AT and CT were not affected from chewing simulation. TC, ZP, and AT presented the highest in ascending order (p < 0.05), PG and CMK showed the lowest fracture load after chewing simulation (p < 0.001).

CONCLUSIONS

Aging did not influence the fracture load of FDPs made of CAD/CAM resins. FDPs made of glass-ceramic showed significantly lower fracture load than those of all resin FDPs.

CLINICAL RELEVANCE

Considering fracture load measurements, CAD/CAM resins tested could be alternative materials to glass-ceramic for FDP construction.