Resin Nano Research Articles

Progressive Tooth Wear Against Resin-Based Restorative Composites.

The composition and properties of resin-based composite materials could affect tooth wear and lead to clinical problems. Therefore, the study objective was to characterize human tooth wear behavior against a bulk-fill restorative (BF) compared to a conventional resin composite (RC) and a CAD/CAM resin nano ceramic (RN). Square-shaped specimens of each material were prepared and sub-divided according to the number of testing cycles (n=8): 100,000, 250,000, and 500,000 cycles. An occlusal wear test was performed using a chewing machine with 49 N, 2 Hz, in 37°C distilled water. Human premolar cusps were used as antagonists. Micro-CT and laser scanner were used to scan antagonists and specimens, respectively. Wear volume was assessed using a software and the wear pattern was examined with SEM. Softening in solvent analysis was performed by measuring the materials' Knoop microhardness (KHN) before and after immersion in ethanol. Wear volume data were analyzed with two-way ANOVA and Student-Neuman-Keuls test (α=0.05). For tooth and specimen wear volume, there was statistical significance for material and number of cycles, but not for the interaction between factors. BF resulted in less tooth (p=0.008) and specimen (p=0.030) wear than RN and RC, which were similar (p⟩0.05). Volume loss increased from 100,000 to 500,000 cycles. BF showed the lowest microhardness (KHN1); and %ΔKHN similar to RC, but greater than RN. BF induced less volume loss to the tooth than RC and RN, while presenting greater wear resistance. The tooth wear pattern and damage progression were mild for all materials. Resin composites show favorable wear behavior, leading to low volume loss and mild structural damage of the tooth. Regular bulk-fill resin composite stands out for its efficient restorative technique, low wear susceptibility and reduced capacity to wear down the tooth.

Self-assembly Fe-Co MOF@BN and epoxy resin nano composites with highly enhanced flame retardancy and smoke suppression properties

A shuttle-shaped Fe-Co bimetallic metal organic frameworks (MOFs) on sheet-like hexagonal boron nitride (h-BN) was fabricated via an organic-inorganic hybrid strategy, forming a novel Fe-Co MOF@BN flame retardant, and the hybrids together with ammonium polyphosphate (APP) were incorporated into epoxy resins to explore their flame retardancy and smoke suppression effects. When combining 0.5 % Fe-Co MOF@BN with 9.5 % APP, the peak heat release rate, peak smoke release rate, CO production rate, and peak CO2 production rate of the EP composite (EP/APP/Fe-Co MOF@BN) were reduced by 73.7 %, 71.4 %, 70 %, and 80 % respectively, compared to epoxy. The limiting oxygen index increases to 30.2 %, indicating the EP/APP/Fe-Co MOF@BN composites have superior fire safety performance. The excellent fire performance of EP/APP/Fe-Co MOF@BN composites benefiting from the barrier effect of Fe-Co MOF@BN lamellar structure, the catalytic carbonization of Fe and Co, the gas phase dilution of APP and the enhancement of the cross-linking degree of the char layer. Meanwhile, Fe-Co MOF@BN improves the dispersion of APP in the EP composites, which broadens the application range of MOF and h-BN. Herein, the EP/APP/Fe-CoMOF@BN composites with high flame retardancy, low smoke production rate, and excellent mechanical properties provide a feasible solution for the use of EP under high temperatures.

Effect of aging on the fracture resistance and microleakage of CAD-CAM-produced ceramic inlays

Aim: The aim of the study was to evaluate the fracture resistance and microleakage of different CAD-CAM inlay restorations. Methodology: Inlay restorations from nine restorative materials as monolithic zirconia (TZI), resin nano ceramic (LU), hybrid ceramic (VE), feldspathic ceramic (CB), zirconia reinforced lithium silicate (VS), lithium disilicate (e.max), leucite reinforced glass ceramic (Emp), resin ceramic (GCS), and conventional composite resin (CR) were used (n=10). For evaluating the fracture resistance, restorations were cemented to resin teeth and subjected to thermomechanical aging. The data of fracture resistance were analyzed using One-way Analysis of Variance (ANOVA) and Games-Howel tests (a=0.05). For evaluating the microleakage, restorations were cemented on human teeth and subjected to thermocycling. The teeth were vertically sectioned into two parts and microleakages were assessed as yes or no. Results: The highest and lowest fracture resistance values were found in TZI and LU groups, respectively (p>0.05). The most frequent microleakage was observed in TZI and CR groups, and the least microleakage was seen in the VE group. Microleakage was frequently found in cervical surfaces and followed by occlusal, axial, and pulpal surfaces. Conclusion: Hybrid ceramics showed similar fracture resistance with the monolithic zirconia; besides, the lowest microleakage was observed for these ceramics. Hybrid ceramics may be a good alternative for inlay restorations. How to cite this article: Bankoğlu Güngör M, İnal CB, Hürbağ M, Toksoy B, Turhan Bal B, Karakoca Nemli S. Effect of aging on the fracture resistance and microleakage of CAD-CAM-produced ceramic inlays. Int Dent Res 2024;14(1):10-18. https://doi.org/10.5577/intdentres.324

Comparison of volumetric loss and surface roughness of composite dental restorations obtained by additive and subtractive manufacturing methods

Statement of problemPermanent crown materials produced with new generation additive manufacturing and traditional subtractive manufacturing materials have not been compared in terms of wear resistance. PurposeThis study aims to compare the volumetric loss related to wear and resulting surface roughness after aging in a chewing simulator between resin nano ceramics produced with milling technique and permanent crown materials produced with three dimensional (3D) printing. Materials and methodsThree different hybrid composite-ceramic (HCC) (The three materials are GC: Cerasmart, VE: Vita Enamic, and GV: Grandio Voco.) and one 3D printed definitive crown resin (FormLabs Permanent Crown Resin) were investigated before aging (n:8), the surface roughness of all samples was measured with a profilometer, and 1 randomly selected sample from each subgroup was imaged with scanning electron microscope (SEM). 3D scans of each sample were obtained with a desktop scanner. Thermomechanical aging was performed using a chewing simulator. Four hundred thousand cycles were completed under a vertical occlusal force of 49 ± 0.7 N with a thermal cycle of 1.7 Hz 5–55° and with a dwell time of 120 s, mimicking 2 years of aging. The imaging procedures were repeated, and the change in surface roughness was evaluated. 3D images were also overlapped, and the volumetric loss was calculated with the relevant inspector software. The data obtained were analyzed by two-way ANOVA (p < 0.05). ResultThe results showed significant statistical differences for both parameters (p > 0.05). The highest volumetric loss was found in the GV group while the lowest volumetric loss was in the VE group. The highest surface roughness values were observed in the GV group, while the lowest values belonged to the VE one. ConclusionOf the restorative materials evaluated, the VE group is suitable for long-term restorations, whereas the GV one is suitable for medium-term restorations. It is promising in terms of 3D printing technologies that the 3D material gives comparable results with the GV group. Clinical i̇mplicationAdditive manufacturing techniques are a successful method that accelerates the manufacturing process. Permanent crown resins are promising alternatives to conventional production.

The fracture strength and the failure mode of lithium disilicate or resin nano ceramics as a crown, overlay, or endocrown restoration on endodontically treated teeth.

Different materials and restorative concepts have been proposed over the years to restore endodontically treated teeth (ETT). Monolithic ceramic and composite restoration can be lute to the tooh, without the use of a post. However, little is known how the material stiffness and presence of a composite core will affect the survival and failure mode. The objective of this in-vitro study was to evaluate the fracture strength and failure mode of endodontically treated molars, restored with ceramic or hybrid composite monolithic restoration, in the presence of absence of a composite core. Sixty depulped molars were restored with a lithium-disilicate (e.max CAD) or hybrid composite (Cerasmart) restoration. Both materials were used in a monolithic approach, but with 3 different designs: (a) monolithic endocrown, (b) crown with a separate composite core, and (c) overlay without core buildup or pulpal extension. Ten sound teeth were used as control group. All groups were thermocycled (10,000 cycles), subsequently loaded in a chewing simulator (100,000 cycles) and finally loaded until fracture. Peak fracture loads and failure modes were registered. No significant differences were seen between the groups in terms of fracture load. Failure modes were statistically significantly different among groups with significant correlation between restoration type and material. (p < 0.001 and p = 0.033, respectively). No group presented significantly higher fracture resistance. Although ceramic crowns and overlays presented the highest repairability, all restored ETT were within the range of the intact tooth' fracture strength. No restoration presented significant different fracture loads. However, the type of restoration and material choice were correlated to the fracture mode.

Translucency Parameters and Masking Abilities of Monolithic CAD/CAM Ceramics.

To compare the translucency parameters and masking abilities of different monolithic CAD/CAM ceramics placed on different-colored substructures. Square-shaped specimens (12 × 12 × 1.5 mm) were prepared from feldspathic (C), leucite (EMP), lithium disilicate (e.max), zirconiareinforced lithium silicate (VS), resin nanoceramic (LU), polymer-infiltrated ceramic (VE), hybrid nanoceramic (GC), monolithic zirconia (TZI), and composite resin (TC) blocks (n &#61; 10 per material). After mechanical polishing, the translucency parameter (TP) was calculated. Then, each ceramic specimen was measured on eight substructures, and the color difference between ND2 and each substrate was calculated with the CIEDE2000 formula. TP values were analyzed with one-way ANOVA and Games-Howell tests, and the color differences indicating masking ability were analyzed with two-way ANOVA and Tukey HSD tests. The highest TP was observed in TC, followed by LU, EMP, C,GC, e.max, VS, VE, and TZI. The ΔE00 color difference values of TZI, VS, and VE on all abutment colors, except for ND9, were below the acceptable threshold value. All monolithic ceramic materials used in the study masked the ND1 and ND3 substrates. The ND9, representing severely discolored or devitalized preparations, could not be masked by any monolithic CAD/CAM ceramics used in the study.

Predictable esthetics in hybrid and resin-based CAD/CAM restorative materials: Translucency as a function of material thickness.

The CAM of esthetically pleasing monolithic dental restorations presents with specific challenges. One vital parameter to consider is the translucency of the materials. Previous studies have proven a correlation between translucency and material thickness for various all-ceramic materials. The aim of the present study was to assess and define the relationship between thickness and translucency in modern resin-based restorative materials. Specimens fabricated from two resin nano-ceramics (Cerasmart, Lava Ultimate), a polymer-infiltrated ceramic network (Vita Enamic), and a polymethyl methacrylate (Telio CAD) were examined, representing these different material classes. For each material, 12 specimens (n = 12) were fabricated in five thicknesses (0.4, 0.7, 1.0, 1.3, and 1.6 mm; N = 240). The translucency was measured with a spectrophotometer. The total light transmittance for each specimen was calculated applying specialized software. Regression curves were fitted to the results and their coefficient of determination (R2) fit was determined. Logarithmic regression curves showed the best R2 approximation (Cerasmart: R2 = 0.994; Vita Enamic: R2 = 0.978; Lava Ultimate: R2 = 0.997; Telio CAD: R2 = 0.997) to the light transmission values. The results of the present study indicate that the translucency of resin-based materials can be calculated using a mathematic approach to estimate their optical behavior. Cerasmart, Lava Ultimate, Vita Enamic, and Telio CAD exhibit a logarithmic relationship between material thickness and translucency. By determining material-specific coefficients for this logarithmic function, the resulting translucency can be computed for any given material thickness.

Evaluation of Post- Operative Sensitivity of Nano Filled Composite Versus Bulk Filled Resin Composite in Posterior Class 2 Restoration

Dental composites use adhesives to adhere and are thermally non-conductive. Despite advances in restorative dentistry, adhesive restorations may cause postoperative pain and fail. Objective: To compare and evaluate the post-operative sensitivity between nano resin composite using incremental technique and bulk filled resin composite using bulk filled technique in class 2 posterior restorations by assessing the post-operative pain and sensitivity. Methods: Two hundred and twenty patients who satisfied inclusion and exclusion criteria were lottery-divided into groups A and B. Nano resin composite was placed via incremental technique in Group A and bulk filled in Group B. Post-operative pain was assessed using Visual Analog Scale 0-10 at 24 hours and 7 days. Results: Male patients were 47 (42.7%) and 48 (43.6%), female patients were 63 (57.3%) and 62 (56.4%). Mean of pain was 2.39 ± 0.97 and 2.32 ± 0.81 at 24 hours postoperatively and 0.14 ± 0.63 and 0.00 at 7 days in group A and group B respectively. Pain level was mild in 97 (88.2%) and 105 (95.5%) patients, moderate in 13 (11.8%) and 5 (4.5%) after 24 hours, no pain in 105 (95.5%) and 110 (100.0%) and mild in 5 (4.5%) and 0 (0.0%) at 7 days in group A and group B, respectively. Conclusion: Bulk filled resin composite using bulk filled technique is more effective in class 2 posterior restorations as compared to nano resin composite using incremental technique

Does the Difference in Finishing Systems and Time affect the Surface Roughness of Two Resin Composites? Comparison between Bulk fill and Nano resin composite

Does the Difference in Finishing Systems and Time affect the Surface Roughness of Two Resin Composites? Comparison between Bulk fill and Nano resin composite

Effect of intracanal diode laser irradiation on fracture resistance of roots restored with CAD/CAM posts

Aim: To evaluate the fracture resistance of roots restored with CAD/CAM-fabricated posts, receiving or not intracanal laser treatment, compared with glass fiber posts under mechanical cycling. Methods: Twenty-seven endodontically treated, single-rooted teeth were divided into 3 groups: group 1 (control), prefabricated glass fiber posts relined with resin composite; group 2, CAD/CAM-fabricated intraradicular posts using Resin Nano Ceramic (RNC) blocks; and group 3, CAD/CAM-fabricated intraradicular posts using RNC blocks in canals irradiated with a 940-nm diode laser (100 mJ, 300-um optic fiber, coronal-apical and apical-coronal helical movements, speed of 2 mm/second, 4 times each canal). After cementation of the coping, cyclic loading was applied at an angle of 135° to the long axis of the root, with a pulse load of 130 N, frequency of 2.2 Hz, and 150,000 pulses on the crown at a point located 2 mm below the incisal edge on the lingual aspect of the specimen. Every 50,000 cycles, the specimens were evaluated for root fracture occurring below or above the simulated bone crest. Results were analyzed by one-way ANOVA followed by Tukey’s test (p&lt;0.05). Results: Group 1 was the least resistant, while groups 2 and 3 were the most resistant. Group 1 differed significantly from groups 2 and 3 (p&lt;0.01), but there was no difference between groups 2 and 3 (p&lt;0.01). Conclusion: Treatment of the intracanal surface with diode laser had no influence on fracture resistance of roots restored with CAD/CAM-fabricated posts, but a longer cycling time is required to evaluate the real benefits of diode laser irradiation.

Comparison of Mechanical Properties of Chairside CAD/CAM Restorations Fabricated Using a Standardization Method

The aim of this in vitro study was to investigate the fracture resistance, fracture failure pattern, and fractography of four types of chairside computer-aided design/computer-aided manufacturing (CAD/CAM) restoration materials in teeth and titanium abutments fabricated using a standardization method. An artificial mandibular left first premolar prepared for all-ceramic crown restoration was scanned. Forty extracted mandibular molars and cylindrical titanium specimens were milled into a standardized shape. A total of eighty CAD/CAM restoration blocks were milled into a crown and twenty pieces of each lithium disilicate (LS), polymer-infiltrated-ceramic-network (PICN), resin nano ceramic (RNC), and zirconia-reinforced lithium silicate (ZLS) materials were used. Crowns were bonded to abutments, and all specimens underwent thermal cycling treatment for 10,000 cycles. Fracture resistance was measured using a universal testing machine and fracture failure patterns were analyzed using optical microscopy and scanning electron microscopy. Statistical differences were analyzed using appropriate ANOVA, Tukey HSD post hoc tests, and independent sample t-tests (α = 0.05). The results indicated that, in both teeth abutments and titanium abutments, the fracture resistances showed significantly the highest values in LS and the second highest in ZLS (p < 0.05). The fracture resistances based on teeth abutments and titanium abutments were significantly different in all the CAD/CAM restoration materials (p < 0.05). There are statistically significant correlations between the types of materials and the types of abutments (p < 0.05). Each of the different materials showed different fracture failure patterns, and there was no noticeable difference in fractographic analysis. Lithium disilicates and zirconia-reinforced lithium silicates exhibited statistically high fracture resistance, indicating their suitability as restoration materials for natural teeth or implant abutments. There were no distinct differences in the fracture pattern based on the restoration and abutment materials showed that the fracture initiated at the groove where the ball indenter was toughed and propagated toward the axial wall.

The efficiency of laser application for debonding laminate restorations manufactured of current CAD-CAM materials with different thicknesses.

Using lasers for adhesive restoration removal can be practical and atraumatic. The purpose of this study was to investigate Er: YAG laser exposure on debonding the adhesive cementation between enamel and feldspar ceramic, lithium disilicate-reinforced and resin nano ceramic composite laminate restorations. Vita Cerec Blocs, IPS e.max Computer-aided design (CAD). Computer-aided design and manufacturing (CAD-CAM) in full and Lava Ultimate restorative materials were chosen. The 3 × 3 mm2 standardized, 0.5-mm and 1 mm thick specimens were cemented on an enamel surface. After thermocycling, each material group was randomly divided into laser treated and control (non-laser treated) groups. Shear bond strength test was done with a universal testing machine with crosshead speed 0.5 mm/min. Factorial ANOVA Technique and TUKEY HSD multiple comparison test were used for statistical analyses. Moreover, the surface morphology of the debonded samples and the enamel was observed using a scanning electron microscope. The laser application was found to weaken the SBS values significantly (P < 0.05) for all groups; however, the most dramatic SBS decrease was observed for laser treated IPS e.max at both thicknesses. Laser treatment can serve as a practical and effective method that eliminates the risk the enamel damage and restoration fracture.

CLINICAL EVALUATION OF THE NANO HYBRID BULK FILL COMPOSITE AND NANO HYBRID FLOWABLE COMPOSITE IN CLASS I RESTORATIONS--- AN IN VIVO STUDY

Objectives: The aim of this study was to evaluate the clinical performance of a nano filled flowable and nano hybrid bulk fill resin composite in class I restorations.&#x0D; Methods and Materials: Twenty patients were selected for this in vivo study. Each patient received at least one pair of restorations, restored with nano hybrid bulk fill resin composite (IPS Empress direct [IED]) and nano hybrid Tetric N Ceram flowable composite [TNC]. Each restorative resin system was used with its respective adhesive system according to manufacturers’ instructions.&#x0D; A total of 40 class I restorations were placed by one operator. Restorations were blindly evaluated by two examiners at baseline and 3, 6, and 12 months respectively using modified US Public Health Service Ryge criteria.&#x0D; The data obtained was statistically analyzed using Chi square test to compare the two restorative materials for each category.&#x0D; Results: At 3, 6 and 12, months, recall rate was 100%, 95% and 85%, respectively, with a retention rate of 100%. There were statistically significant differences between the two restorative resins in terms of marginal adaptation and marginal discoloration (p&lt;0.05).&#x0D; No differences were observed between the restorative resins in terms of retention (p&lt;0.05). None of the restorations showed postoperative sensitivity, or loss of anatomic form.&#x0D; Conclusion: Within the limitations of this study, nano hybrid bulk fill composite resin viz. IPS EMPRESS DIRECT showed better clinical performance than nano filled flowable composite in terms of marginal discoloration and marginal adaptation.&#x0D; Keywords: direct composite, bulk, hybrid filled resin

Characterization of Zinc Oxide-Urea Formaldehyde Nano Resin and Its Impact on the Physical Performance of Medium-Density Fiberboard.

The main purpose of this research work is to characterize zinc oxide-urea formaldehyde nano resin and identify the physical performance of medium-density fiberboard (MDF). Considering the dry weight of natural fibers, the ZnO nanoparticles were added to urea formaldehyde (UF) glue at four levels—0.0%, 1.0%, 2.0% and 3.0%—and their effects were investigated in terms of the physical properties of MDF. The surface morphology and crystalline structure of ZnO, UF and UF-ZnO nanofillers were characterized using Scanning Electron Microscopy (SEM) and X-ray diffraction (XRD) analysis and significant improvements were achieved as a result of the addition of nanoparticles. Thermal properties were analyzed by means of differential scanning calorimetry (DSC) and thermogravemetric analysis (TGA) and it was observed that increasing the concentration of ZnO nanoparticles ultimately enhanced the curing of UF-ZnO nanofillers. Finally, density, thickness swelling and water absorption properties were investigated and it was observed that thickness swelling and water absorption properties were improved by 38% and 12%, respectively, when compared to control MDF.

Multifunctional carbon fiber reinforced multilayered metastructure with broadband microwave absorption and effective mechanical resistance

AbstractMetastructure is an innovative structure form to improve broadband microwave absorption. However, without reliable mechanical properties, it is difficult to apply metastructure absorbers in realistic application scenarios. Herein, a multifunctional carbon fiber reinforced multilayered metastructure (CFRMM) is proposed and fabricated through the principles of multiscale design, gradient structure design, and metastructure design. The multiwall carbon nanotube (MWCNT)/carbonyl iron (CI)/epoxy resin(EP) nano lossy composite was integrated with the patterned resistive films (PRF) to form a gradient metastructure. Carbon fiber (CF) cloth was incorporated into the structure to enhance mechanical resistance. The CFRMM achieves −10 dB absorption bandwidth in frequency bands of 2‐4.3 GHz and 7.02‐18 GHz with maximum absorption of −17.4 dB. The −9 dB absorption bandwidth was covered in the full band 2‐18 GHz. The CFRMM exhibits excellent mechanical properties with equivalent tensile strength and flexural strength of 75.77 and 408.43 MPa, respectively. The large tensile fracture strain of 24% reveals the good toughness of the metastructure. Broadband microwave absorption and effective load bearing integrated in one structure make the CFRMM more promising for applications in the future.

Effects of toothbrushing on surface characteristics of microhybrid and nanofilled resin composites following different finishing and polishing procedures

ObjectivesTo evaluate the effects of simulated tooth brushing (STB) on the surface roughness of microhybrid and nanofilled resin composites following different finishing and polishing procedures. Materials and methodsNinety cylindrical-shaped specimens of Filtek Supreme XT (a universal nano resin composite) and Filtek Z250 (a universal microhybrid resin composite) were prepared. The specimens were allocated at random into 9 paired groups each of 10 specimens. The finishing and polishing systems included were Tungsten Carbide bur (TC); Diamond bur (Db); Sof-Lex discs (S); PoGo discs (PG); TC + S; Db + S; TC + PG; Db + PG. Polymerisation against a Mylar strip without finishing and polishing acted as the control. Surface roughness was measured using a 3D non-contact optical profilometer and surface morphology was examined by scanning electron microscopy. Specimens were subjected to the equivalent of four years STB and surface roughness was measured again. ResultsMylar formed surfaces were the smoothest for both composites before and after STB. Finishing with the diamond finishing bur caused significantly greater surface irregularity (p < 0.0001) before and after STB compared to the tungsten carbide bur. The surface treatment with Db + PG resulted in significantly greater surface roughness following STB than all other regimes of finishing and polishing (p < 0.01). ConclusionWhere indicated clinically, finishing is better conducted using a tungsten carbide bur rather than a diamond finishing bur. The combination of tungsten carbide bur/Enhance PoGo and tungsten carbide bur/Sof-Lex surface protocols produced a similarly smooth finish for both composites. The composite surfaces in all groups increased in surface irregularity following STB. Clinical significanceWhilst finishing using a tungsten carbide finishing bur followed by either the Sof-Lex or PoGo polishing system may be found to result in a smooth surface finish, all the surfaces investigated increased in surface roughness following toothbrushing.

Influence of different surface treatments on resin nano ceramic-resin cement bond strength

This work aimed to evaluate the effect of different surface treatments on the shear bond strength of resin nano ceramic to resin cement, thereby providing a theoretical basis for the improvement of clinical application. A total of 150 specimens (10 mm×10 mm×3 mm) were milled from resin nano ceramic blocks (Lava Ultimate) using computer-aided design/computer aided manufacturing(CAD/CAM) technology. The specimens were randomly divided into five groups according to the surface treatment performed, as follows: control, sandblasted, sandblasted+silane, hydrofluoric acid, and hydrofluoric acid+silane groups. After the corresponding surface treatment, the specimens were cemented using Single Bond Universal Adhesive and RelyXTM Ultimate ClickerTM adhesive resin cement. All cemented specimens were placed in distilled water for 24 h and 30 days and subjected to a shear bond strength test in a universal testing machine. The surface treatment and water storage periods showed significant effects on bond strength. Surface treatment with sandblasted+silane showed the highest shear strength values among all tested groups, and the difference was statistically significant (P<0.05). A difference was observed between the control and hydrofluoric acid groups, and both had significantly difference compared with other groups (P<0.05). Sandblasted and hydrofluoric acid+silane groups were not statistically different, and both had significantly difference compared with other groups (P<0.05). The surface of resin nanoceramic treated by sand-blasted, sandblasted+silane, and hydrofluoric acid+silane can improve the bond strength. The sandblasted+silane group had the best the shear bond strength among the groups.

Colour stability and surface properties of high-translucency restorative materials for digital dentistry after simulated oral rinsing.

High-translucency restorative materials are commonly used in the restoration of anterior teeth where aesthetics is a critical factor. In this in vitro study, the impact of mouthwash on the colour stability and surface characteristics of high-translucency computer-aided design and computer-aided manufacturing (CAD-CAM) dental restorative materials was evaluated. Two-hundred specimens were fabricated from five high-translucency CAD-CAM materials: a resin nano ceramic; a polymer-infiltrated ceramic network; a feldspathic ceramic; a lithium disilicate glass ceramic; and high-translucency zirconia. Each group of ceramic specimens was then divided into four subgroups: conventional mouthwash (LISTERINE); whitening mouthwash (LISTERINE Healthy White); chlorhexidine gluconate; and distilled water. Oral rinsing was simulated at 100rpm for 180h, representing 15yr of clinical simulation. The specimens were then evaluated for colour, translucency, gloss, roughness, and surface morphology. Two-way ANOVA and linear mixed models were used for intergroup comparisons (α=0.05). The polymer-infiltrated ceramic network and feldspathic ceramic became brighter, more opaque, less glossy, and rougher after rinsing with the whitening mouthwash. The long-term use of specific mouthwashes can cause deterioration of the optical and surface properties of high-translucency CAD-CAM dental restorations.

A comparative study on color and dimensional stability of esthetic indirect dental materials

In selecting dental materials, color and dimensional stability play key roles in mechanical characteristics as well as esthetic aspects. While resin nano ceramics have been examined to determine their mechanical characteristics in carious experiments, few studies have focused on their intra-oral stability, specifically their long-term color stability or water sorption. In this study, ceramic, resin nano ceramic, and composite resin were analyzed to evaluate their color stability, water sorption, and solubility. The amount of characteristic changes was measured using a spectrometer, an electronic scale, and a caliper for durations of 1, 2, 4, and 8 weeks. The results showed that ceramic was the most stable among all materials, whereas resin nano ceramic and composite resin demonstrated time-dependent changes, which require more clinical considerations for long-term use.

Single blinded in-vitro study comparing microleakage between CAD/CAM crowns milled out of feldspathic ceramic and resin nano ceramic, cemented with three resin cements

Background: Studies on microleakage of Computer-Aided Design/Computer-Aided Manufacturing (CAD/CAM) crowns are abundant. However many of them are inconclusive, especially those using self adhesive cements.&#x0D; Aims: To compare the microleakage between CAD/CAM crowns milled out of feldspathic ceramic and resin nano ceramics, cemented with three resin cements.&#x0D; Materials and Methods: Crown preparation was made on 54 extracted human premolars. Impressions were captured optically using CEREC 3D machine intraoral camera, and crowns were milled from feldspathic ceramic (CEREC® Blocs PC, VITA) and resin nano ceramic (Lava™ Ultimate CAD/CAM Restorative, 3M ESPE) blocks. The crowns were then cemented with three cements (n = 9); RelyX™ U200 Self-Adhesive Resin Cement (3M ESPE); NX3 Nexus ® cement with two-step etch-and-rinse adhesive (Kerr Corporation) or three/multistep etch-and-rinse resin cement, Variolink® II/Syntac Classic (Ivoclar Vivadent). The specimens were kept in water for 24 hours, thermocycled, and then soaked in methylene blue dye for 24 hours, before being sectioned mesiodistally. Microleakage was assessed using a fivepoint scale using stereomicroscope. Statistical analysis of the data was carried out using ONEWay ANOVA.&#x0D; Results: CEREC® Blocs PC crowns showed significantly less microleakage (p&lt; 0.001) compared to Lava™ Ultimate. RelyX™ U200 showed significantly lower microleakage (p&lt; 0.001) compared to other cements. Combination of Lava™ Ultimate crown cemented with RelyX™ U200 showed the least microleakage (p&lt; 0.001).&#x0D; Conclusions: The microleakage scores were affected by the types of crown and cements.&#x0D; Bangladesh Journal of Medical Science Vol.18(4) 2019 p.764-772