Objective
To systematically review studies on various occlusal splint materials and describe their mechanical and chemical properties.
Methods
MEDLINE (PubMed), Scopus, and Web of Science searches ...were conducted for in vitro studies focusing on occlusal splint materials. Two reviewers performed an assessment of the identified studies and data abstraction independently, and this was complimented by an additional hand search. The articles were limited to those in the English language that were published between January 1
st
, 2012, and December 1
st
, 2022.
Results
The initial search yielded 405 search results of which 274 were selected for full-text review following abstract evaluation. 250 articles that did not meet the inclusion criteria were excluded, and the remaining 25 articles (with 1 article identified from the reference lists of included articles) providing mechanical and chemical values were used in this review. Poly methyl methacrylate (PMMA) -based occlusal splint materials showed the highest values in terms of hardness, wear resistance, flexural strength, flexural modulus, e-modulus, and fracture toughness. The material group with the highest water sorption and water solubility was 3D printed (PR) splint materials. In addition, the lowest degree of double bond conversion was also observed in this group of materials.
Conclusions
The outcome of this review suggests that mechanically and chemically acceptable properties can be attained with PMMA-based occlusal splint materials using both conventional and digital production methods. PR splint materials should not be considered as the primary choice for long-term treatments due to their low mechanical and chemical properties.
Clinical Relevance
This review provides clinical recommendations for selecting the appropriate material and fabrication method for occlusal splints while taking the patients’ needs and the materials´ mechanical and chemical properties into account.
In recent years, Zirconia-reinforced Lithium Silicate ceramic (ZLS), combining lithium-silicate and zirconia features, has shown to have excellent mechanical and aesthetic characteristics. Thus, the ...aim of this study was to compare the fracture strength of ZLS single crowns cemented with two different cementation techniques. Twenty crowns were realised and cemented on teeth replicas achieved from an extracted premolar human tooth. The samples were divided into two groups of 10 specimens each, Glass-ionomeric cement (GIC) group and Self-Adhesive Resin Cement (ARC) group. The mechanical test was performed using a universal testing machine. The specimens were then evaluated with a scanning electron microscope (SEM) to identify for all crowns and related abutments the pattern of fracture after the breaking point. The data obtained were statistically analysed. The mean fracture toughness values and standard deviations (±SD) were 2227 ± 382 N and 3712 ± 319 N respectively for GIC and ARC groups. In fact,
-test showed a statistically significant difference between the two groups (
< 0.001). Moreover, the SEM results demonstrated portions of abutments still attached to the crown fragments in the ARC group, whilst these were not present in the GIC group. Within the limitations of this study, these results suggest the use of adhesive cementation for ZLS crowns, which significantly increase the compressive strength of ZLS restorations compared to GIC.
The aim of this study was to evaluate four test methods on the adhesion of resin composite to resin composite, and resin composite to glass ceramic. Resin composite specimens (N = 180, Quadrant ...Universal LC) were obtained and distributed randomly to test the adhesion of resin composite material and to ceramic materials (IPS e.max CAD) using one of the four following tests: (a) Macroshear SBT: (n = 30), (b) macrotensile TBT: (n = 30), (c) microshear µSBT: (n = 30) and (d) microtensile µTBT test (n = 6, composite-composite:216 sticks, ceramic-composite:216 sticks). Bonded specimens were stored for 24 h at 23 °C. Bond strength values were measured using a universal testing machine (1 mm/min), and failure types were analysed after debonding. Data were analysed using Univariate and Tukey’s, Bonneferroni post hoc test (α = 0.05). Two-parameter Weibull modulus, scale (m), and shape (0) were calculated. Test method and substrate type significantly affected the bond strength results, as well as their interaction term (p < 0.05). Resin composite to resin composite adhesion using SBT (24.4 ± 5)a, TBT (16.1 ± 4.4)b and µSBT (20.6 ± 7.4)a,b test methods presented significantly lower mean bond values (MPa), compared to µTBT (36.7 ± 8.9)b (p < 0.05). When testing adhesion of glass ceramics to resin composite, µSBT (6.6 ± 1)B showed the lowest and µTBT (24.8 ± 7)C,D the highest test values (MPa) (SBT (14.6 ± 5)A,D and TBT (19.9 ± 5)A,B) (p < 0.05). Resin composite adhesion to ceramic vs. resin composite did show significant difference for the test methods SBT and µTBT (resin composite (24.4 ± 5; 36.7 ± 9 MPa) vs. glass ceramic (14.6 ± 5; 25 ± 7 MPa)) (p > 0.05). Among substrate–test combinations, Weibull distribution presented the highest shape values for ceramic–resin in µSBT (7.6) and resin–resin in µSBT (5.7). Cohesive failures in resin–resin bond were most frequently observed in SBT (87%), followed by TBT (50%) and µSBT (50%), while mixed failures occurred mostly in ceramic–resin bonds in the SBT (100%), TBT (90%), and µSBT (90%) test types. According to Weibull modulus, failure types, and bond strength, µTBT tests might be more reliable for testing resin-based composites adhesion to resin, while µSBT might be more suitable for adhesion testing of resin-based composites to ceramic materials.
The effect of additional reference objects on the accuracy of different intraoral scanners for partially and completely edentulous patients has not been investigated sufficiently.
The purpose of this ...in vitro study was to evaluate the effect of an additional reference object in the form of additional artificial landmarks on the trueness and precision of different intraoral scanners in partially and completely edentulous areas.
Partially and completely edentulous models with 2 and 4 implants (BLT, RC, Institut Straumann AG), respectively, were used in the study. For the digital scan, scan bodies (CARES Mono Scanbody) were attached, and reference data obtained by using industrial scanners. Ten digital scans of the same model were made with each intraoral scanner: PRIMESCAN, TRIOS 3, TRIOS 4, Carestream 3600, and Medit. Then, additional artificial landmarks were attached, and 10 more intraoral scans were made with each device. Computer-aided design files of the scan bodies were aligned to obtain 3-dimensional surfaces with reference and test scanners. Trueness and precision of distance, angulations, and vertical shift between scan bodies were estimated. The Mann-Whitney Wilcoxon or Student 2-sample t test was applied to estimate statistically significant differences between groups (α=.05).
In the partially edentulous model, distance trueness mean ±standard deviation values ranged from −46.7 ±15.4 μm (TRIOS 3) to 392.1 ±314.3 μm (Medit) in models without additional artificial landmarks. When additional artificial landmarks were applied, trueness of distance mean ±standard deviation values ranged between −35 ±13 μm (TRIOS 4) and 117.7 ±232.3 μm (CARESTREAM). Trueness mean ±standard deviation values of angulation varied from −0.0 ±0.5 degrees (CARESTREAM) to 0.2 ±0.0 degrees (PRIMESCAN) without additional artificial landmarks and from 0.0 ±0.2 degrees (TRIOS 3) to 0.4 ±0.5 degrees (CARESTREAM) with additional artificial landmarks. Vertical shift trueness measurements varied from −108 ±47.1 μm (TRIOS 4) to 107.2 ±103.5 μm (Medit) without additional artificial landmarks and from −15.0 ±45.0 μm (CARESTREAM) to −86.9 ±42.1 μm (TRIOS 4) with additional artificial landmarks. The additional artificial landmark technique improved the trueness of all measured parameters for the 5 tested intraoral scanners. No statistically significant differences were found among models with or without additional artificial landmarks, except for Medit in all parameters and PRIMESCAN in angle measurements (P<.05). The best precision for distance was found with TRIOS 3 and with PRIMESCAN for angulation and vertical shift. Larger deviations were observed in the completely edentulous situation. The effect of additional artificial landmarks was limited when the accuracy parameters of digital scans were considered.
Scans with and without additional artificial landmarks of partially edentulous conditions scanned by any of the intraoral scanners tested did not influence precision and trueness, except for Medit i500 in the distance and vertical shift parameters and CARESTREAM3600 in vertical shift. Precision and trueness of digital scans of completely edentulous areas were affected, except for Medit i500 for distance, PRIMESCAN and TRIOS 4 for angle, and all systems except TRIOS 4 for vertical shift precision.
The aim of this study was to compare the shear bond strength of relined CAD-CAM complete removable dental prosthesis (CRDP) resins with conventional heat-polymerized polymethylmethacrylate (PMMA) ...resin.
A total of 96 resin specimens in identical dimensions of 10 mm × 10 mm × 11 mm were fabricated for four study groups #1- Conventional heat-polymerized group: n=24 (ProBase); #2- Milled#1: n=24 (Ivobase); #3- Milled#2: n=24 (Ivotion); #4- 3D-printed: n=24, (NextDent Denture 3D+). Twelve specimens in each group were sectioned in the middle to produce a 3 mm defect and then were relined using a conventional denture relining material. All specimens underwent thermocycling (5-55°C) for 10,000 cycles. The shear bond tests were carried out in a universal testing machine. One-way ANOVA and Tukey's test were used for statistical analysis (p<0.05). The two-parameter Weibull distribution values were calculated.
Relined 3D-printed specimens had a significantly lower shear bond strength when compared with conventional (p=0.0003) and milled groups (Milled#1: p=0.0004; Milled#2: p<0.0001). There were no differences in the shear bond strengths between the milled and conventional groups. Weibull distribution presented the highest shape value for the non-relined Milled#1 (22.83) group and the lowest values for the 3D-printed relined group (4.001).
The findings of this study conclude that the shear bond strength of the conventionally-relined 3D-printed resins used for fabricating CRDPs was inferior to the shear bond strength of conventionally-relined resins employed for manufacturing CRDPs using CAD-CAM milling and conventional heat-polymerization techniques.
When considering 3D-printing for the fabrication of CRDPs, it is recommended to employ it in clinical situations where a frequent need for denture relining is not expected.
This study evaluated the effects of different simulated chairside grinding and polishing protocols on the physical and mechanical properties of surface roughness, hardness, and flexural strength of ...monolithic zirconia. Sintered monolithic zirconia specimens (15 mm × 3 mm × 3 mm) were abraded using three different burs: diamond bur, modified diamond bur (zirconia specified), and tungsten carbide bur, along with a group of unprepared specimens that served as a control group. The study was divided into two phases, Phase 1 and Phase 2. Surface roughness, surface hardness, and flexural strength were assessed before and after the grinding procedure to determine the ‘best test group’ in Phase 1. The best abrasive agent was selected for Phase 2 of the study. The specimens in Phase 2 underwent grinding with the best abrasive agent selected. Following the grinding, the specimens were then polished using commercially available diamond polishing paste, a porcelain polishing kit, and an indigenously developed low-temperature sintered zirconia slurry. The physical and mechanical properties were again assessed. Results were analyzed using one-way ANOVA test. Specimens were observed under scanning electron microscopy (SEM) and X-ray diffraction (XRD) for their microstructure and crystalline phases, respectively. Grinding with diamond burs did not weaken zirconia (p > 0.05) but produced rougher surfaces than the control group (p < 0.05). Tungsten carbide burs did not significantly roughen the zirconia surface. However, specimens ground by tungsten carbide burs had a significantly reduced mean flexural strength (p < 0.05) and SEM revealed fine surface cracks. Phase transformation was not detected by XRD. Polishing with commercially available polishing agents, however, restored the surface roughness levels to the control group. Dental monolithic zirconia ground with tungsten carbide burs had a significantly reduced flexural strength and a smooth but defective surface. However, grinding with diamond burs roughened the zirconia surface. These defects may be reduced by polishing with commercially available polishing agents. The use of tungsten carbide burs for grinding dental zirconia should not be advocated. Grinding with diamond abrasives does not weaken zirconia but requires further polishing with commercially available polishing agents.
This study aimed to investigate the effect of universal primers on resin composite repair with and without silica-coating while assessing adhesion durability under various aging methods. Specimens ...were fabricated using multiple increments of composite resin (Clearfil Majesty Esthetic) placed into cylindrical forms (diameter: 3.2 mm, height: 4 mm) and photopolymerized. Specimens (N = 300, n = 15 per group) were randomly assigned to three groups for aging (control: fresh-dry, 6 months water storage and thermocycling ×5000 cycles, 5-55 °C). These three main groups were further randomly assigned to two groups according to the surface conditioning procedures; (a) Control: No air-abrasion, and (b) Air abrasion with silica-coating (Co-Jet, 30 µm, 5 s, 2.5 bar). All subgroups were then randomly divided into five subgroups to be treated with adhesion promoters (a) All Bond Universal: AB (Bisco), (b) Clearfil Universal Bond Quick: SKB (Kuraray), (c) Monobond Plus: MP (Ivoclar Vivadent), (d) G-Premio Bond: GP (GC), (e) Clearfil Universal Bond: CU (Kuraray). After bonding according to the manufacturer's instructions to new composite blocks, shear bond strength tests were conducted using a Universal testing machine (1 mm/min). Obtained Data (MPa) were analyzed by 3-way ANOVA and Tukey`s post-hoc tests (alpha = 0.05). Bond strength results were significantly affected by the adhesive type (p < 0.05), silica-coating (p < 0.05), and aging (p < 0.001) but the interaction terms were not significant (p > 0.05). In non-aged groups (24 h), no significant effect on bond strength was observed using silica-coating (min; 8.41; max:12.98) but after 6 months, silica-coating increased the results for AB, GP, and CU ranging between 9.56 and 11.25 (p < 0.05) and even more after thermocycling for SKB, MP, GP, CU (10.23-13.95) (p < 0.05) compared to non-conditioned groups (6.83-10.37 for 6 months, 8.96-11.18 for thermocycling, respectively). Failure types were mainly adhesive for non-air abraded groups but exclusively cohesive after silica-coating. For immediate or short-term resin composite repairs, silica-coating may not improve adhesion but shear bond strength could be secured by this conditioning method after aging.
Studies on the microhardness of novel additively manufactured polymers compared with well-established low- and high-viscosity composite resins with regard to chemical composition are lacking.
The ...purpose of this in vitro study was to evaluate the effect of hydrothermal aging on the microhardness of various conventional and additively manufactured polymers.
Cylindrically shaped specimens (N=240, n=10 per group) (Ø10×2 mm) were either additively manufactured (6 groups) or conventionally (6 groups) manufactured by using 3D (Optiprint Temp OP; Dentona; C&B MFH ND; NextDent; Saremco print CROWNTEC SA; Saremco Dental AG; Temp Print TP; GC; 3DELTA ETEMP DM; Deltamed; MED690 ST; Stratasys, Ltd) or conventional low (Gradia Direct GR; GC; Clearfil Majesty CM; Kuraray Noritake; Tetric EvoCeram TE; Ivoclar AG) and high (Gradia Direct Flo GR-F; GC; Clearfil Majesty Flow CM-F; Kuraray Noritake; Tetric EvoFlow TE-F; Ivoclar AG) viscous materials. All specimens were randomly allotted to 2 different aging methods (no-aging dry or aging by thermocycling TC, ×6000, 5 °C-55 °C) and Vickers hardness (VH) tested (ZHV30; Zwick). Three indentations were made on each specimen (0.98-N load, duration 15 seconds). The calculated average microhardness value of each specimen was statistically analyzed by using 2-way ANOVA and Tukey post hoc tests (α=.05). Two-parameter Weibull distribution was calculated to predict the reliability of material type and aging method on VH.
The mean ±standard deviation VH ranged between 17 ±0.5 VHN and 68 ±0.5 VHN in the following ascending order: group STa<OPb, NDb<SAc, TPc<GRd, GR-Fd<DMe, TE-Fe<CMf<TEg<CM-Fh. The groups with the same superscript were not significantly different from each other (P>.05). The mean ±standard deviation of HV for aged (37 ±1 VHN) and nonaged (35 ±1 VHN) specimens were statistically similar (P>.05). The Weibull distribution values presented the highest shape for the aged group SA (37.81).
The choice of the material had a significant effect and resulted in lower hardness for the 3-dimensionally printed materials than for the conventional composite resins. Under fatigue conditions, the choice of the material showed no significant difference when the Vickers microhardness was evaluated.
Selective laser melting (SLM) additive manufacturing (AM) technology is a current option to fabricate cobalt-chromium (Co-Cr) metal frameworks for dental prostheses. However, the Co-Cr alloy ...composition, surface roughness, and ceramic bond strength values that SLM metals can obtain are not well-defined.
The purpose of this in vitro study was to compare the chemical composition, surface roughness, and ceramic shear bond strength of the milled and SLM Co-Cr dental alloys.
A total of 50 disks of 5 mm in diameter and 1 mm in thickness were fabricated by using subtractive (control group) and AM with each of following SLM providers: SLM-1 (EOS), SLM-2 (3D systems), and SLM-3 (Concept Laser). The milled disks were airborne-particle abraded with 100-μm aluminum oxide particles. All the specimens were cleaned before surface roughness (Ra), weight (Wt%), and atomic (At%) percentages were analyzed. Three-dimensional profilometry was used to analyze the topographical properties of the surface parameters Ra (mean surface roughness). The chemical composition of Co-Cr alloy specimens was determined by using energy dispersive X-ray (EDAX) elemental analysis in a scanning electron microscope (SEM). Thereafter, the specimens were bonded to a ceramic (Dentine A3 and Enamel S-59; Creation CC) interface. Specimens were stored for 24 hours at 23 °C. The bond strength of the SLM-ceramic interface was measured by using the macroshear test (SBT) method (n=10). Adhesion tests were performed in a universal testing machine (1 mm/min). The Shapiro-Wilk test revealed that the chemical composition data were not normally distributed. Therefore, the atomic (At%) and weight percentages (Wt%) were analyzed by using the Kruskal-Wallis test, followed by pairwise Mann-Whitney U tests between the control and AM groups (AM-1 to AM-4). However, the Shapiro-Wilk test revealed that the surface roughness (Ra) and ceramic bond strength data were normally distributed. Therefore, data were analyzed by using 1-way ANOVA, followed by the post hoc Sidak test (α=.05).
Significant differences were obtained in Wt%, At%, and Ra values among the Co-Cr alloys evaluated (P<.05). Furthermore, the control group revealed significantly lower mean ±standard deviation Ra values (0.79 ±0.11 μm), followed by AM-3 (1.57 ±0.15 μm), AM-2 (1.80 ±0.43 μm), AM-1 (2.43 ±0.34 μm), and AM-4 (2.84 ±0.27 μm). However, no significant differences were obtained in the metal-ceramic shear bond strength among the different groups evaluated, ranging from mean ±standard deviation 75.77 ±11.92 MPa to 83.65 ±12.21 MPa.
Co-Cr dental alloys demonstrated a significant difference in their chemical compositions. Subtractive and additive manufacturing procedures demonstrated a significant influence on the surface roughness of the Co-Cr alloy specimens. However, the metal-ceramic shear bond strength of Co-Cr alloys was found to be independent of the manufacturing process.
The present report describes a technique for a digital cast-free clinical workflow for the fabrication of a combined tooth-implant–supported removable partial denture. This technique comprises ...digital intraoral scanning, computer-aided design, and subtractive computer-aided manufacturing for the denture base, denture teeth, and crowns and additive computer-aided manufacturing for the denture framework (CAD-CAM).
PDF
