Zirconia-reinforced Lithium Disilicate Research Articles

Effect of immune-boosting beverage, energy beverage, hydrogen peroxide superior, polishing methods and fine-grained dental prophylaxis paste on color of CAD-CAM restorative materials

BackgroundThe effect of an immune-boosting beverage (SAM) containing Sambucus Nigra, an energy beverage (ENE), an in-office bleaching (BLE) agent with 25% hydrogen peroxide superior, glazing (GLA) or polishing (POL) methods, and professional dental prophylaxis (PDP) on the color of CAD-CAM restorative materials is unknown.MethodsIn total 210 specimens were prepared, consisting of CAD-CAM feldspathic (FC), zirconia-reinforced lithium disilicate ceramic (ZLS) and hybrid ceramic (HC). The ceramic specimens were divided according to the polishing methods of glazing (GLA) and mechanical polishing (POL). All materials were divided into two groups: with and without BLE. A 25% hydrogen peroxide superior (HPS) gel was used for BLE. After the baseline (BAS) measurement, the specimens were immersed in 3 different beverages (distilled water (DIS), SAM, ENE). After 28 days, a fine-grained (RDA 7) prophylaxis paste was applied. Statistical analysis of ∆E00 color difference values was performed by 3-way ANOVA and Bonferroni test (α = 0.05).ResultsThe effect of all other actions except material-BLE-beverage on color for BAS-Day 28 was statistically different (p < 0.05). The effect of material, material-BLE, beverage on color for Day 28-PDP was statistically different (p < 0.05). After 28 days, the lowest color change was found in FC-GLA and HC immersed in DIS (p = 0.0001) and the highest in FC-POL immersed in ENE (p = 0.0002). PDP was efficient in color recovery in HC immersed to DIS, ENE and SAM (p = 0.0010). For FC, HC and ZLS, BLE caused a higher color change (p < 0.0001). Regardless of the material, the highest color change for BLE-beverage was found in BLE-treated specimens immersed in ENE (p = 0.0496) and the lowest color change was found in non-BLE-treated specimens immersed in SAM (p = 0.0074).ConclusionsIn materials pre-exposed to 25% HPS, the effect of PDP on color recovery was lower than in unexposed materials. After 28 days, mechanical polishing produced higher color change in FC than glazing, however, in ZLS effects of glazing and mechanical polishing on color were similar. For material/polishing method, HC was the most effective. ENE caused higher color change than DIS and SAM. PDP was more effective than ENE in restoring color to DIS- and SAM-immersed specimens.

Effect of thermomechanical loading on fracture resistance and failure mode of new pressable zirconia-reinforced lithium disilicate onlay restoration.

Insufficient information exists regarding the fracture resistance and failure pattern of newly developed zirconia-reinforced lithium disilicate (ZL, Vita Ambria) onlays. This in vitro study compared the fracture resistance of two types of onlays: monolithic lithium disilicate (LD) and monolithic ZL. Forty-eight ceramic onlay restorations were fabricated on epoxy dies using a maxillary first premolar model. The samples were divided into two main groups: LD and ZL. Half of each group was subjected to thermomechanical fatigue loading (TML) using a chewing simulator. All the samples were cemented with self-adhesive resin cement. Subsequently, they were loaded until failure in a universal testing machine, and the fracture patterns and resistance were recorded. Before TML, ZL demonstrated the highest statistically significant mean fracture resistance (499.76±34.14N) compared to LD (470.40±27.38N). After TML, ZL showed the highest non-statistically significant mean fracture resistance (429.27±131.42N), while LD's mean fracture resistance decreased (377.31±62.18N). Monolithic zirconia-reinforced onlays demonstrated higher fracture resistance and a more favorable failure mode compared to LD. However, the impact of thermomechanical aging resulted in reduced fracture resistance for both materials, with a notable preference observed for ZL.

Surface treatments of the zirconia-reinforced lithium disilicate ceramic in the adhesion to the resin cement.

This study verified the effect of surface treatments of the zirconia-reinforced lithium disilicate ceramic bonded to resin cement. Ceramic blocks were divided according to treatments (n=10): FA+SRX (Fluoric acid + silane RX), FA+MDP (Fluoric acid + MDP), FA+SCF+MDP (Fluoric acid + silane CF + MDP), FA+MEP (Fluoric acid + MEP), and MEP (Self-etch primer). Resin cement cylinders were made in the ceramic blocks, photoactivated with 1,200 mW/cm² for 40s, stored in water at 37°C for 24h, and evaluated by the microshear strength test, optical failure descriptive analysis (%), surface characterization (SEM) and contact angle (Goniometer). Other samples were submitted to 10,000 thermocycles between 5°C and 55°C. Bond strength data were submitted to two-way ANOVA and Tukey's test. Contact angle to one-way ANOVA and Games-Howell's test (5%). At 24h, MEP showed higher bond strength, and FA+SRX the lower. FA+MDP and FA+SCF+MDP showed similar values and FA+MEP was intermediate. After thermocycling, FA+SCF+MDP, FA+MEP, and MEP showed higher values, and FA+SRX the lower while FA+MDP was intermediate. When the periods were compared, FA+MDP, FA+SCF+MDP, FA+MEP, and MEP showed higher values for 24h while FA+SRX was similar. SEM showed retentive surface and crystal exposure when treated with FA+SCF+MDP. The less retentive surface was obtained with MEP, and the other treatments promoted intermediate irregularities. In conclusion, surface treatment and thermocycling promoted different values of adhesive strength and contact angle in a zirconia-reinforced lithium silicate ceramic. Failures were predominantly adhesive, and the ceramic surface was characterized by different levels of roughness and selective exposure of crystals.

Comparison of load bearing capacity of ceramic crowns with zirconia or polyetherketoneketone frameworks.

The aim of the present study was to compare the load bearing capacity of monolithic or bilayered single crowns with zirconia or polyetherketoneketone frameworks designed and fabricated using CAD/CAM systems. Cr-Co-based metal dies (n = 60) were duplicated from an extracted and prepared premolar and then restored with different CAD/CAM materials. The specimens were divided into five groups (n = 12) according to the type of materials: group S: monolithic zirconia-reinforced lithium disilicate; group ZI: bilayered zirconia framework with lithium disilicate; group ZE: bilayered zirconia framework with resin-infiltrated hybrid ceramic; group PI: bilayered polyetherketoneketone (PEKK) framework with lithium disilicate; group PE: bilayered PEKK framework with resin-infiltrated hybrid ceramic. The crown specimens were cemented on Cr-Co metal dies with a resin cement (Multilink N). The specimens were subjected to cyclic mechanical loading followed by load bearing testing. Data were analyzed using the Kruskal-Wallis and Mann-Whitney U tests (α = 0.05). The monolithic crowns in group S (1930 ± 452.18 N) presented significantly higher load bearing capacity than those of the other groups (P < 0.05). This was followed by group ZI (1165.41 ± 264.04 N). The remaining groups demonstrated comparable results. Failure types were more frequent in all zirconia specimens that included veneering ceramic. Monolithic zirconia-reinforced lithium disilicate CAD/CAM ceramics showed superior load bearing capacity compared with all other bilayered counterparts. All CAD/CAM materials tested remarkably exceeded the average occlusal force in the posterior region.

Wear characteristics of esthetic resin matrix and zirconia reinforced lithium disilicate CAD/CAM materials: two-body wear and surface topography analysis.

This in vitro study assessed the wear behavior of different CAD-CAM blocks and the abrasion of the enamel antagonist against these materials. 64 disk-shaped specimens were prepared from 8 different CAD/CAM blocks as follow: one lithium disilicate glass ceramics block "IPS Emax CAD" as control group, two zirconia reinforced lithium silicate "Vita Suprinity & Celtra DUO," one interpenetrating network ceramic block "Vita Enamic," Three resin-based block composites "Lava Ultimate, Cerasmart & Brilliant-crios" as well as one hybrid nanoceramic "Shofu block HC". All specimens were mounted against canine and tested for two body wear analysis using a chewing simulating loading machine (100,000 cycles, 50 N, 5/55 °C). The amount of wear loss was measured for each specimen using a digital precise scale. Wear area before and after the chewing simulation were evaluated using an optical profilometer. Data analysed using one-way ANOVA test followed by Tukey's post hoc. The results showed a significantly higher wear loss in resin matrix ceramics in comparison to glass ceramics. However, for tooth wear glass ceramics had significantly higher value than hybrid ceramics. Resin based CAD/CAM Blocks gives a superior result when evaluating the wear behavior and its effect on the opposing tooth surface.

A micro-computed tomography analysis of internal and marginal fits of fixed partial dentures: Effect of preparation finish line designs on monolithic zirconia and heat-pressed zirconia-reinforced lithium disilicate.

To evaluate the effect of finish line design (chamfer and feather-edge) and ceramic type on the internal and marginal fits of fixed partial dentures on abutment teeth. Two typodont mandibular casts, missing right first premolar tooth, received tooth preparation on canine and second premolar abutments (one cast with chamfer finish line and the other cast with feather-edge finish line). The preparation segment of each typodont model was scanned, 3D printed in resin, and then invested and casted in metal to obtain two metal models. Polyvinyl siloxane impressions were made for the metal models and poured in type IV stone. The stone models (n=40) were randomly assigned into four groups (n=10): chamfer finish line with heat-pressed zirconia reinforced lithium disilicate fixed partial denture (CL), chamfer finish line with monolithic zirconia fixed partial denture (CZ), feather-edge finish line with heat-pressed zirconia-reinforced lithium disilicate fixed partial denture (FL), and feather-edge finish line with monolithic zirconia fixed partial denture (FZ). After the fabrication of ceramic restoration, micro-computed tomography was used to evaluate the internal and marginal fits of each fixed partial denture. Data were statistically analyzed with three-way ANOVA (α=0.05). There were no significant interactions between preparation type, material type, and tooth type at any of the areas assessed. There was significant difference (p=0.01) between CZ (59.15±4.6µm) and FZ (73.6±17.1µm) groups at the finish line area. Regarding the horizontal marginal discrepancy area, there were significant differences between CZ (62.65±10.5µm) and FZ (90.05±5.6µm) groups (p<0.001), CL (77.45±8.1µm) and CZ (62.65±10.5µm) groups (p<0.001), and FZ (90.05±5.6µm) and CL (77.45±8.1µm) groups (p<0.001). At finish line area, there was a significant difference (p=0.018) between feather-edge with canine (72.75±13.3µm) and chamfer with canine (59.05±5.8µm); however, there was no significant difference (p=0.774) between feather-edge with premolar (69.45±12µm) and chamfer with premolar (65.1±7.4µm). Moreover, there was no significant difference (p=0.886) between feather-edge with canine and feather-edge with premolar. The internal and marginal fits of the ceramic fixed partial dentures can be affected by the finish line design and ceramic type. The feather-edge finish line had a negative impact on the marginal and internal fits of ceramic fixed partial dentures at certain measurement points. Regarding the effect of finish line design on abutment teeth, the difference in fit was only detected at the finish line area of the anterior abutment (canine) with the feather-edge finish line.

Marginal gap distance and cyclic fatigue loading for different all-ceramic endocrowns.

The aim of the study was to evaluate the effect of the fabrication techniques of two types of glass ceramics on the marginal gap distance and the fracture resistance of endocrown restorations after cyclic loading. Forty extracted mandibular first molars were root canal treated. Decoronation was done for all the endodontically treated teeth 2 mm above the cemento-enamel junction. The teeth were individually fixed vertically into epoxy resin mounting cylinders. All teeth were prepared to receive endocrown restorations. The prepared teeth were randomly divided into four equal groups (n=10) according to the all-ceramic materials and technique used for endocrown construction as follows: Group I (n=10): Pressable lithium disilicate glass ceramics (IPS e-max Press), Group II (n=10): Pressable zirconia-reinforced lithium disilicate glass ceramics (Celtra Press), Group III (n=10): Machinable lithium disilicate glass ceramics (IPS e-max CAD), Group IV (n=10): Machinable zirconia-reinforced lithium disilicate glass ceramics (Celtra Duo). The endocrowns were cemented using dual-cure resin cement. All endocrowns were subjected to fatigue loading. The cycles were repeated 120,000 times to clinically simulate one year chewing condition. Marginal gap distance of all endocrowns was measured directly using a digital microscope with x100 magnification. The load required to failure was recorded in Newton. Data were collected, tabulated, and statistically analyzed. Fracture resistance testing of all-ceramic crowns revealed a statistically significant difference between all different ceramic materials used in this study (p-value <0.001). On the other hand, there was a statistically significant difference between all the four ceramic crowns for the marginal gap distance either before or after fatigue cyclic loading. After considering the limitation of the current study, the following conclusions were given: endocrowns are considered one of the promising minimally invasive restorations for root canal treated molars. CAD/CAM technology revealed better results than heat press technology regarding the fracture resistance of glass ceramics. Heat Press technology revealed better results than CAD/CAM technology regarding the marginal accuracy of glass ceramics.

Cantilever resin-bonded fixed dental prosthesis to substitute a single premolar: Impact of retainer design and ceramic material after dynamic loading.

To evaluate the influence of retainer design and ceramic materials on the durability of minimally invasive cantilever resin-bonded fixed dental prostheses (RBFDPs) after artificial aging. One hundred caries-free human mandibular molars were prepared as abutments for all-ceramic cantilevered fixed dental prostheses using the following retainer designs: One wing (OW), Two wings (TW), Inlay ring (IR), Lingual coverage (LC), and Occlusal coverage (OC). Two ceramic materials were used: monolithic high translucent zirconia(z) and zirconia-reinforced lithium disilicate (ZLS2) (n=10). All restorations were adhesively bonded with resin cement. The thermocycling of the specimens were performed between 5°C and 55°C for 10,000 cycles and then exposed to 240.000 cycles of dynamic loading on a chewing simulator. All surviving specimens were loaded onto the pontic until failure using a universal testing machine. The mean failure load ranged from 124.00 to 627.00 N for the zirconia groups and from 133.30 to 230.00 N for the ZLS2 groups. Regarding the materials, a significantly higher failure load was recorded in the zirconia groups than in the ZLS2 groups (P<0.001), except for OW (P=0.748). Regarding the retainer designs, a significant different failure load was recorded between the different designs except for IR and LC in the zirconia groups, IR and OC, OW and TW, and TW and LC in the ZLS2 groups (P<0.001). Zirconia IR, LC, and OC can be used as cantilever RBFDP in the premolar region. The fracture resistance of the ZLS2 design was below the normal bite force and should not be recommended as the first option.

Roughness of the Surface of Zirconia Reinforced Lithium Disilicate Ceramic Treated by Different Procedures.

Lithium disilicate and zirconia are the two most popular materials for aesthetic and dental prosthetic work; however, due to their limitations, a new material is being researched, namely zirconia-reinforced lithium disilicate, the surface of which is treated with different procedures to achieve the best possible surface properties. In this study, the surface of zirconia-reinforced lithium disilicate glass-ceramic was treated using different methods (conventional and laser) to determine the effects of the treatment procedures on the surface properties and surface roughness to achieve a higher strength of adhesion from the self-adhesive resin cement to zirconia-reinforced lithium disilicate. The treated surfaces were investigated using profilometry, X-ray diffraction and energy dispersive X-ray fluorescence. The results obtained were statistically evaluated. The results show that the surface roughness is highest for the samples treated with Er:YAG (erbium-doped yttrium aluminium garnet laser) and silanisation. Furthermore, the surface treatment procedures applied did not change the composition of the surface.

Surface Roughness and Hardness of CAD/CAM Ceramic Materials after Polishing with a Multipurpose Polishing Kit: An In Vitro Study.

This article evaluates the effect of multipurpose polishing kit on surface roughness and hardness of three computer-aided design/computer-aided manufacturing (CAD/CAM) ceramic materials at different polishing durations. Weight changes of the polishing bur were also determined. Three CAD/CAM ceramic materials were lithium disilicate glass ceramic (IPS e.max CAD), translucent zirconia (VITA YZ), and zirconia-reinforced lithium disilicate ceramic (Celtra Duo). Ceramics were ground with a diamond bur, and polished with the multipurpose polishing kit (Eve Diacera HP), which comprises coarse and fine polishing burs. Surface roughness value (Ra) was measured using a noncontact optical profilometer (n = 10 per group) after grinding and every 15 seconds of coarse and fine polishing until 60 seconds. The complete polishing Ra was compared with the lab as-received specimens and human enamel. Surface morphology was examined using a scanning electron microscope after 60-second coarse and fine polishing and compared with the lab as-received specimens. Hardness was measured using a Vickers hardness tester on the lab as-received specimens and after the final polishing process (n = 4 per group). Changes in surface roughness and polishing bur weight of each material were analyzed using one-way repeated-measures analysis of variance (ANOVA) and dependent t-test. One-way ANOVA was used to detect differences in surface roughness, Vickers hardness, and bur weight among materials within the same polishing duration (α = 0.05). From grinding to complete polishing, the greatest Ra reduction was found in VITA YZ, followed by Celtra Duo and IPS e.max CAD. Final Ra values of all ceramics after 60-second fine polishing were not significantly different, and were similar to that of enamel and lab as-received specimens. Vickers hardness of ceramic materials did not change after grinding and polishing. Coarse polishing bur demonstrated the highest weight loss after polishing VITA YZ, followed by Celtra Duo and IPS e.max CAD. The multipurpose polishing kit reduced surface roughness of CAD/CAM ceramic materials to the similar level of the lab as-received specimen and enamel regardless of material's hardness. The reductions of surface roughness and a coarse polishing bur weight were highest in VITA YZ, followed by Celtra Duo and IPS e.max CAD.

Fracture resistance of bonded ceramic overlay restorations prepared in various designs

This study investigates fracture resistance of adhesive ceramic overlays of various designs. Forty-eight upper premolar teeth were divided into eight groups. The variations were: shoulder margins on the buccal and lingual surfaces with axial wall heights of 1, 2, or 3 mm; one shoulder margin with axial wall height of 1, 2, or 3 mm on the lingual surface and one contrabevel margin on the buccal surface; contrabevel margins on the buccal and lingual surfaces; and a control of sound teeth. Overlays were designed and fabricated with CAD/CAM using zirconia-reinforced lithium disilicate ceramic and bonded with resin cement. Samples underwent thermocycling and dynamic fatigue equivalent to 6 months of use. Compressive loading was applied until fracture, and fracture mode was analyzed. Results showed no statistical difference in fracture resistance between designs, and the fracture pattern of most was involvement of pulp tissue and below the CEJ. Fracture resistance of the restored teeth was also not statistically different from the control. All control fractures were within the dentin and above the CEJ. Overlay restorations were therefore effective in strengthening damaged teeth and imparting fracture resistance equal to sound teeth, and axial wall heights and margin types did not influence this result.

Finite element analysis and nanomechanical properties of composite and ceramic dental onlays

The aim is to evaluate the mechanical properties of the composite and ceramic based indirect restorative materials used in dental treatments with scanning nanoindentation test (NT). Finite element analysis (FEA) was applied to investigate the stress distribution. Four hybrid composite materials; Indirect resin composite (IRC), Resin nanoceramic (RNC), Polymer infiltrated ceramic (PIC) and Zirconia-reinforced lithium-di-silicate (ZRC) were divided into two subgroups for NT (n = 20) and fracture test (n = 40). Statistical analyses were performed with independent t-test, ANOVA and post-hoc Tukey tests (p ≤ 0.05). The highest hardness, elasticity and fracture toughness were observed in ZRC (p = 0.001). Frequency of vertical root fractures in RNC and IRC were statistically lower than ZRC (p = 0.032). Reinforced CAD-CAM ceramics revealed higher mechanical properties compared with IRC materials. The FEA model for fracture mechanism of RNC demonstrated lowest stress values and uniform stress distribution amongst all groups, while ZRC and PIC presented the highest fracture toughness.

47 - Effect of Sintering and Etching Protocols of Zirconia-Reinforced-Li2O-SiO2 on Bond-Strength

The optimal tensile bond strength of zirconia reinforced lithium-disilicate after multiple glazing firing protocols, different etching time and etchant concentration needs to be evaluated. Purpose of this study was to evaluate the effect of different firing cycles and etching condition on resin cement tensile bond strength of zirconia reinforced lithium disilicate system glass ceramics to titanium. Square-shaped specimens (N=53) were prepared from blocks of zirconia reinforced lithium silicate glass ceramics (CeltraDUO) with 12.5 mm×14 mm rectangular tiles of 2 mm thickness. The specimens were subjected to different firing cycles and etching conditions. They were cemented onto titanium rods (Grade V Ti-alloy, 4.8 mm in diameter, and 1 inch in length) with a resin cement (Theracem), and then tested for tensile bond strength. Least square mean linear regression model was used to analyze the effects on tensile bond strength data using JMP Pro 13.2, followed by the post hoc Tukey tests and tests (α= 0.05). The tensile bond strength was significantly affected by etching duration (p<0.001) and firing cycles (p<0.001), but not significantly affected by etchant concentration (p=0.31). The highest load to failure was observed at 30-60 seconds of etching time and the least load to failure was observed at 20 seconds of etching time. In terms of firing cycles, 1 firing cycle provided the highest load to failure in contrast to least load to failure observed with no firing. Changes in etching time and firing condition of the specimens had a significant effect on the resin cement tensile bond strength of zirconia reinforced lithium disilicate. On the other hand etching the specimens under different concentrations of 5 and 9.6% did not differ statistically in terms of resin cement tensile bond strength.

Stainability of different ceramic materials against mouth rinses and effect of polishing after staining

Statement of problemMouth rinses are known to stain tooth surfaces. However, their staining effect on different ceramics after prolonged use and the effect of polishing after staining are still unclear. PurposeThe purpose of this in vitro study was to evaluate the stainability of different ceramic materials against different mouth rinses and the effect of polishing on staining. Material and methodsForty disk-shaped specimens were prepared from each material (total of 160 specimens): lithium disilicate (IPS e.max CAD), zirconia-reinforced lithium disilicate (VITA SUPRINITY PC), leucite-reinforced feldspar (GC Initial LRF), and resin matrix ceramic (CERASMART). Baseline color measurements (T0) were recorded with a clinical spectrophotometer (VITA Easyshade V). The specimens were immersed in chlorhexidine gluconate (CHX) 0.2% mouth rinse (Klorhex), (KLO) chlorhexidine gluconate 0.1% mouth rinse (Eludril) (ELU), a daily mouth rinse (LISTERINE Cool Mint) (LIS), artificial saliva (CON) continuously for 7 days (T1), 14 days (T2), and 28 days (T3). Discoloration values (ΔE) between the immersion time points (T0,T1,T2,T3) were calculated by using the following formula: ΔE= ([ΔL∗]2 + [Δa∗]2 + [Δb∗]2)1/2. After the immersion process, specimens were polished and ΔE values remeasured. The Kruskal-Wallis and Mann-Whitney U tests were performed (α=.05) and were adjusted by postanalysis Bonferroni testing. ResultsKLO caused the highest ΔE values in all groups. IPS e.max CAD had the lowest ΔE values, and CERASMART showed the highest ΔE values against all of the solutions (P<.05). However, polishing caused a decrease in the ΔE values in all groups. ConclusionsProlonged use of mouth rinses may cause color change in different ceramic materials. Polishing affected the color change and resulted in a decrease in ΔE values. Mouth rinses containing CHX should be recommended with caution for daily use.

FRACTURE RESISTANCE OF ENDODONTICALLY TREATED TEETH RESTORED WITH LITHIUM DISILICATE CROWNS RETAINED WITH FIBER POSTS COMPARED TO CERASMART AND CELTRA DUO ENDOCROWNS (IN VITRO STUDY)

Aim: The purpose of this study wasto evaluate the fracture resistance of cerasmart and Celtra Duo endocrowns compared to endodontically treated teeth restored with glass fiber post and lithium disilicate crowns. Methodology: Eighteen sound maxillary premolars were endodontically treated, then divided into three groups: Group (GE) received fiber post, resin core and lithium disilicate (IPS E.max CAD, Ivoclar-Vivadent) crown. Group (GC) received endocrown with butt joint finish line design fabricated from hybrid ceramic (CERASMART, GC Dental USA). Group (GD) received endocrown with butt joint finish line design fabricated from zirconia reinforced lithium disilicate (CELTRA DUO, Dentsply Sirona). All restorations were fabricated using (CEREC MC XL SW 4.0) milling machineand cemented with self-adhesive dual cureresincement. Thermo-mechanical fatigue was applied on all samples and fracture test was then done. Scanning electron microscope was used for examining the fractured samples. Results: Fracture resistance test showed that there was statistically significant difference between the three groups (P-value = 0.001, Effect size = 0.603).GE showed statistically significant highest median fracture value (1866 +/- 399.9).Meanwhile, there was no statistical difference between mean fracture resistance values of GC of (1045.1 +/- 122.1) and GD (1377 +/-307) where both showed statistically significant lowest mean fracture resistance values. Conclusion: Conventional post, core andcrown treatment option remains the gold standard for treating endodontically treated maxillary premolar, nevertheless endocrown restoration on premolars needs further research to become a viable restoration in this condition.

Wear resistance of crowns made from different CAM/CAD materials

ObjectivesThe aim of this laboratory study was to evaluate the wear resistance of crowns made from current computer-aided design and computer-aided manufacture (CAD/CAM) materials. In addition, the abrasion of the steatite antagonist against these materials was compared. MethodsIdentically shaped crowns of lithium disilicate, zirconia-reinforced lithium disilicate and a polymer-infiltrated ceramic network (PICN) were fabricated with an occlusal thickness of 1.5mm and a lateral wall thickness of 1.2mm (n=8). The crowns were cemented with a dual-polymerizing luting resin on composite resin dies. Using spherical steatite antagonists, all specimens were loaded with 49N for 1,200,000 cycles in a mastication simulator with additional thermocycling. After 120,000, 240,000, 480,000, 960,000, and 1,200,000 cycles, precision impressions were made and investigated with a laser scanning microscope. The vertical and volume substance loss was measured. Additionally, the substance loss of the antagonists was evaluated after 1,200,000 loading cycles. ResultsNo significant difference (p>0.05) was found in the median volume loss of the test materials after 1,200,000 cycles (lithium disilicate: 0.405mm3, PICN: 0.362mm3, zirconia-reinforced lithium disilicate: 0.340mm3). The vertical substance loss of PICN (157μm) was significantly lower (p≤0.05) than that of lithium disilicate (201μm) and zirconia reinforced lithium disilicate (191μm). However, the substance loss of steatite against zirconia-reinforced lithium disilicate (0.191mm3) was significantly lower (p≤0.05) than against lithium disilicate (0.296mm3) and PICN (0.531mm3). SignificanceAll three CAD/CAM materials showed wear resistance that seems appropriate for clinical application. Also, the abrasion of the antagonist looks promising.

Restoration of severe localized tooth wear with zirconia-reinforced lithium silicate: A case report

Tooth wear is becoming an increasingly common cause for referral to restorative dentistry departments in the UK. Often, these cases are treated with resin-bonded composite direct restorations in the first instance. This article presents a case of 23-year-old patient who was treated using zirconia-reinforced lithium disilicate restorations. CPD/Clinical Relevance: In certain cases, indirect restorations can be considered a first-line treatment, based on the presentation and patient factors. Each case should be evaluated on its own merits and careful consideration should be given to the evidence base and its relevance.

The Influence of Surface Roughening and Polishing on Microbial Biofilm Development on Different Ceramic Materials.

To test the hypothesis that surface roughening and polishing of ceramics have no effect on their surface roughness and biofilm adhesion. Feldspathic ceramic Vitablocks™ TriLuxe forte (VTF), lithium disilicate glass IPS e.max Press™ (IPS) and zirconia reinforced lithium silicate Vita Suprinity™ (VS) ceramic blocks (n = 27 per group) were prepared from sintered CAD blocks using a water-cooled saw. They were further subdivided into 3 subgroups according to the surface treatment protocols (n = 9): as prepared, roughened and polished. The surface roughness of the ceramic blocks was measured using an electro-mechanical profilometer. The ceramic sections were inoculated with Streptococcus mutans and incubated for 48 hours to form a biofilm. The ceramic surfaces with the biofilms were analyzed using Confocal Laser Scanning Microscopy to calculate the percentage of live bacteria and substratum coverage by the biofilm, and further visualized using scanning electron microscopy. Statistical analysis was done with SPSS software using two-way ANOVA, followed by post hoc Bonferroni test to identify significant differences between the groups. The level of significance was set at p = 0.05. As prepared VTF showed significantly higher mean surface roughness values than as prepared IPS and VS. The mean percentage of live bacteria and biofilm coverage of the substrate were significantly higher in the roughened ceramic blocks than the as prepared and polished blocks for all three ceramic types (p < 0.05). Polished specimens of VS significantly lower percentage of biofilm coverage than the other groups (p < 0.05). This study sheds new light that adjustments of ceramic restorations prior to cementation increases the likelihood for formation and adhesion of microbial biofilms on the surface. Polished zirconia reinforced lithium disilicate ceramics demonstrated the lowest bacterial adhesion among the evaluated ceramics.

Repair bond strength of dental computer-aided design/computer-aided manufactured ceramics after different surface treatments.

To evaluate the microtensile bond strength of four dental computer-aided design/computer-aided manufactured (CAD/CAM) ceramics after application of four different surface treatments. Four dental CAD/CAM ceramics were tested: feldspathic ceramic (VITABLOCKS-Mark II), polymer-infiltrated ceramic network (VITA ENAMIC), zirconia-reinforced lithium silicate (VITA SUPRINITY), and yttria-stabilized zirconia (VITA YZ T). Four surface treatments were applied: no treatment, 5% hydrofluoric acid-etching, airborne particle abrasion, and tribochemical silica coating. The ceramic blocks were repaired with nanohybrid composite (Tetric N-Collection). Sixteen test groups of 12 specimens were prepared. After thermocycling, microtensile bond testing was performed. The microtensile strengths values were statistically analyzed using two-way analysis of variance and Tukey's post-hoc test. Repaired feldspathic and resin polymer-infiltrated ceramic network ceramics demonstrated superior microtensile bond strengths compared to zirconia-reinforced lithium silicate and yttria-stabilized zirconia. Etched feldspathic and polymer-infiltrated ceramic network ceramics had higher bond strength than the untreated groups. Surface treatments did not affect the bond strength of zirconia-reinforced lithium silicate and yttria-stabilized zirconia with the exception of etching, which reduced the bond strength of yttria-stabilized zirconia. Feldspathic ceramic and polymer-infiltrated ceramic network were repaired with dental composite after surface etching with hydrofluoric acid. Repair of zirconia-reinforced lithium silicate and yttria-stabilized zirconia did not demonstrate promising results. Repair of feldspathic ceramic and polymer-infiltrated ceramic network restorations may be a cost-effective means to promote the longevity of dental restorations. However, zirconia and zirconia-reinforced lithium disilicate restorations do not offer such an option.

Effect of different cement systems and aging on the bond strength of chairside CAD-CAM ceramics

Statement of problemThe bond strength of different chairside computer-aided design and computer-aided manufacturing (CAD-CAM) restorative materials to dentin with different resin cements needs to be evaluated. PurposeThe purpose of this in vitro study was to investigate the effect of 3 different cementation systems after thermal aging on the shear bond strength of different CAD-CAM materials. Material and methodsThe occlusal surfaces of 63 molar teeth of similar size were removed, and 21 zirconia-reinforced lithium disilicate (Vita Suprinity-VS), 21 polymer infiltrated ceramic (Vita Enamic-VE), and 21 resin nanoceramic (GC Cerasmart-GC) rectangular specimens of 2.5 mm in thickness were obtained. The ceramics were cemented using total etch (TE), self-etch (SE), and self-adhesive (SA) cement systems. Half of the specimens were subjected to thermal aging with 5000 cycles. The shear bond strength test of all the specimens was measured. Fractured ceramic surfaces were examined by scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM/EDX) analysis. The Shapiro-Wilk test, 3-way analysis of variance (ANOVA), and Fisher Least Significant Difference (LSD) tests were used to analyze the shear bond strength test data (α=.05). ResultsThe highest bond strength value was found in the nonthermal aged VS-TE and the lowest in the thermal aged VE-TE. Significant interaction was found between TE and SE cemented ceramics (P<.001). For specimens cemented with the SA system, significant interaction was found among ceramics with thermal aged specimens (P<.001). Thermal aging significantly decreased the mean bond strength (P<.05). ConclusionsDifferences in bond strength were observed in chairside CAD-CAM ceramics when cemented with TE, SE, and SA systems. Additionally, thermal aging significantly reduced the bond strength values of all the ceramic materials, regardless of the cementation procedure. Clinicians should consider these variables and choose the most suitable cementation systems for the material used.