Resin Nano Research Articles

Evaluation of Post-Operative Sensitivity of Bulk Fill Resin Composite versus Nano Resin Composite: A Randomized Controlled Clinical Study.

BACKGROUND:Despite recent advances in restorative dentistry adhesive restorations may cause postoperative sensitivity which leads to restoration failure.AIM:This study aimed to compare and evaluate the incremental and bulk fill resin Composite postoperative sensitivity in class II posterior restorations bonded with two adhesive systems (self-etch and etch-and-rinse).METHODS:Sixty patients were randomly selected, their age range from twenty-five to forty years old, divided into two groups according to the packing technique of resin composite material; incremental Tetric Evoceram and Tetric Evoceram bulk-fill resin composite. Thirty patients (n = 30) for incremental Tetric Evoceram resin composite restorations and according to the adhesive systems used they were equally divided (n = 15 teeth).Thirty patients (n = 30) for Tetric Evoceram bulk-fill resin composite restorations and according to the adhesive systems used (etch and rinse or self-etch), they were equally divided (n = 15 teeth). Post-operative pain assessed at 24 hours, 1 week and 1 month using the Visual Analog Scale Score (VAS). Each patient was instructed to put a mark on the VAS line at home to point out the intensity of pain at each assessment period. The problem of measuring the pain that pain tolerance of individuals may be different from the others. This may be due to different reasons, and it is not always because of a problem in the restorationRESULTS:After 1 day, 1 week as well as 1 month, no statistically significant disagreement between the two resin composite types using self-etch adhesive strategy and total-etch adhesive strategy. Also, when the two adhesive systems were compared using Bulk Fill resin composite and incremental Nano resin composite no statistically significant disagreement between the two adhesive systems after 1 day, 1 week as well as 1 month.CONCLUSION:The post-operative hypersensitivity is related to many factors as the procedure of cavity preparation, adhesive approach, and type of resin composite used and placement technique of the resin composite.

Effects of Different Surface Treatments on the Bond Strength of CAD/CAM Resin Nano Ceramic or Ceromer to Resin Cement

Objectives: The purpose of this study was to evaluate the effects of different surface treatments on the micro-tensile bond strength (MTBS) of two different indirect restoration materials (resin nano ceramic CAD/CAM material [Lava Ultimate, 3M ESPE]; ceromer material [Estenia C&B, Kuraray Medical]). Materials and Methods: Specimens were prepared from each test material in dimensions of 3×10×10 mm. The specimens were divided into five different surface treatment groups: group 1 (control [C]), no treatment; group 2 (acid etching [A]); group 3 (acid etching + universal adhesive [AA]); group 4 (sandblasting [S]); and group 5 (sandblasting + universal adhesive [SA]). The prepared specimens were cemented to composite parts (Filtek Z250 Universal Restorative, 3M ESPE) of the same size using dual-cure adhesive resin cement (Panavia F2.0, Kuraray Medical). A total, 100 bar-shaped specimens (6×1×1 mm) were cut using a low-speed diamond saw (n=10 in each group). The MTBS test was performed in all groups (Shimadzu AG-50 kNG, Kyoto, Japan, 1 mm/min). Data were analyzed using a two-way analysis of variance (ANOVA) and Tukey’s multiple comparison tests at a significance level of p<0.05. Results: The MTBS values were significantly influenced by the type of restorative material and surface treatment (p<0.05). There were statistically significant differences between the materials and surface treatments procedures (p<0.05). For Lava Ultimate and Estenia C&B materials, the highest MTBS value was obtained in the SA surface treatment (p<0.05) and the lowest MTBS value was obtained in the control groups (p<0.05). Conclusions: The application of silane-containing universal adhesive material after sandblasting was the ideal surface treatment for both materials.

Vickers Micro-Hardness of New Restorative CAD/CAM Dental Materials: Evaluation and Comparison after Exposure to Acidic Drink.

CAD/CAM (computer-aided design/computer-aided manufacturing) for indirect restorative materials has been recently introduced in dentistry. The purpose of this study was to evaluate the change of the surface micro-hardness of different restorative CAD/CAM materials after exposure to a carbonated acidic drink (Coca-Cola, Coca-Cola Company, Milan, Italy). One hundred and eighty specimens of identical size (2 mm thickness) were obtained by sectioning each tested CAD/CAM block of four materials: a hybrid ceramic (CERASMART™, GC Corporation, Tokyo, Japan), a resin nano ceramic (Lava™ Ultimate, 3M, Monrovia, CA, USA), a nanohybrid composite (Grandio blocs, VOCO GmbH, Cuxhaven, Germany), and a zirconia-reinforced lithium silicate glass ceramic (VITA SUPRINITY® PC; VITA Zahnfabrik, Bad Sackingen, Germany). Forty-five specimens of each material were tested. Micro-hardness was measured at baseline, after 7 days and after 28 days. The data were analyzed. The micro-hardness of each material varied significantly after immersion in Coca-Cola. The nanohybrid composite had a high initial micro-hardness and the greatest percentage loss after acid exposure. The hybrid ceramic and the resin nano ceramic had similar percentage losses of micro-hardness values even if the second material had higher initial values. The zirconia-reinforced lithium silicate glass ceramic had the highest baseline values and the lowest percentage loss of micro-hardness. The different CAD/CAM materials presented different micro-hardness values before and after acid exposure.

Shade Stability of Polymer Infiltrated and Resin Nano Ceramic Crowns after Dynamic Chewing Simulation.

Investigation of the shade stability of polymer-infiltrated and resin nano ceramic crowns before and after artificial aging. 40 identical crowns of each of the materials VITA Enamic (VE) and Lava Ultimate (LU) were manufactured. Half of the crowns went through a dynamic chewing simulation (CS) with thermocycling. Material subgroups: 1. VE, 2. VE/CS, 3. LU, 4. LU/CS (each n=20). These were divided into 4 groups (n=5) and distributed in usual stain solutions. The shade of each crown was measured occlusally and vestibularly before and after insertion using a spectrophotometer (n=5). The data were analyzed using ANOVA and Tukey's test (p≤0.05). Sum scores (SSC) of the occlusal ΔE values: LU/CS: 7.99, VE: 5.75 VE/CS: 5.44, LU: 5.17. The total sum of the SSC yielded, for the materials: SSCtotal(VE): 20.0 and SSCtotal(LU): 24.0. Occlusally, there were significant shade differences for VE/CS (p=0.025) and LU/CS (p=0.014) between red wine and distilled water. LU/CS is significantly more clearly stained occlusally by coffee in comparison to the other three material subgroups (VE: p=0.007, LU: p=0.026, VE/CS: p=0.013). The shade stability of VITA Enamic crowns is superior to that of Lava Ultimate crowns. Only Lava Ultimate is affected by chewing simulation.

Evaluation of effects of non-thermal plasma treatment on surface properties of CAD/CAM materials

The purpose of this in vitro study was to evaluate the effect of the non-thermal plasma (NTP) treatment on the wettability and surface roughness of different types of CAD/CAM materials as well as the shear bond strength (SBS) of adhesive resin cement to the treated surfaces. Three different materials, namely; resin nano ceramic, feldspathic ceramic and poly(methyl methacrylate) (PMMA)-based samples were treated with NTP for different time points to evaluate the effect of NTP treatment on the surface properties of CAD/CAM materials. Moreover, surfaces of CAD/CAM materials were visualised with scanning electron microscopy (SEM). A 90-second NTP treatment time was determined as the optimum time for the highest measured wettability, and thus, the 90-second NTP treated samples were used for the SBS test and evaluation of the failure types. Our results revealed the NTP treatment lowered the contact angles and increased the roughness of all tested materials. Moreover, The NTP treatment significantly enhanced the SBS of resin nano ceramic and feldspathic ceramic-based materials. NTP could be considered as a novel pre-treatment method to improve surface properties and the bonding performance of ceramic-based CAD/CAM materials.

Shade Stability of Polymer-Infiltrated and Resin Nano Ceramics.

Background:The esthetics plays an increasingly significant role in today's dentistry.Objective:The objective was to investigate the shade stability of a polymer-infiltrated and a resin nano ceramic in comparison to a conventional feldspar ceramic and an acrylate polymer.Methods:20 specimens of each of the materials, CAD-Temp (CT), Mark II (M), VITA Enamic (VE) and Lava Ultimate (LU), were prepared using the standard method. These were divided into groups (n=5) and placed in the following stain solutions: Distilled water, coffee, Coca-Cola and red wine for 14 days. The shade of each specimen was measured before and after using a spectrophotometer (n=5). The data were analyzed using ANOVA and Tukey's test (p ≤ 0.05).Results:The largest ΔE mean values were observed in CT by Coca-Cola (4.38 ± 0.41), in M by coffee (5.95 ± 0.62), in VE (6.02 ± 0.78) and LU (8.61 ± 0.30) by red wine. LU had the largest and strongest overall shade differences (total score: SSC=16.95) and CT the least (SSC=8.74). Overall shade differences of VE (SSC=12.03) and M (SSC=12.48) were statistically indistinguishable. After 14 days, only Coca-Cola caused clinically relevant shade differences in CT (ΔE > 2.7); this was also caused by coffee, Coca-Cola and red wine in M and coffee and red wine in VE and LU.Conclusion:On average, VE showed fewer shade differences than LU. After 14 days of immersion, shade differences which exceeded the clinical acceptance threshold of ΔE=2.7 were shown by CT in Coca-Cola, by M in coffee, Coca-Cola and red wine, and by VE and LU in coffee and red wine.

One Year -Randomized Clinical Trial to Evaluate Packable Bulk fill and Nano Resin Composite in Children and Adolescents

Purpose: To evaluate the one- year clinical performance of the packable bulk fill and nano resincomposite in class I restorations in children and a adolescents.Materials & Methods: (33) pairs of first permanent molars had class I restorations wereplaced in (33) children were selected from Outpatient Clinic, Pediatric Dentistry Department,Faculty of Dentistry, Suez Canal University, each patient received two class I restorations thatwere similar as possible . In all cavities, single bond adhesive (Xeno V+) was applied. One cavity ofeach pair was randomly assigned to be restore with packable bulk fill resin composite (Quixfil) inincrement up to 4 mm . Another cavity was restored with Nano hybrid resin composite (Esthet-Xflow) placed in 2 mm increments. All restorations were evaluated at one week baseline and then onemonth, 3 months, 6 months , 9 months and 12 months . using slightly modified USPHS .Results: At all periods of evaluation, no statistically significant differences were detectedbetween packable bulk fill composite resin and Nano hybrid composite resin in marginal adaptation,surface roughness and caries detection ,whereas statistically significant differences between bothmaterials in anatomical form and marginal discoloration parameters in favor with packable bulkfill. Sensitivity was not reported during all evaluation periods Performance at one week base line, 1month, 3 months, 6 months, 9 months and 12 months for all criteria.Conclusions: The packable bulk- fill composite resin showed highly clinical performance whencompared with Nano hybrid composite resin restorations at one- year follow up. Further studiesnecessary for long term clinical evaluation of these materials.

Fracture Resistance of A Newly Proposed Occlusal Veneer Design Using Two Different CAD/CAM Ceramic Materials

Statement of the Problem: Management of severe occlusal erosive lesions constitutes a challenging therapeutic approach to the restorative dentist. Bonded occlusal veneers have been introduced as a conservative solution to traditional onlays or complete coverage crowns. Still, there is lack of information and conflict in the data concerning the mechanical performance of the occlusal veneer materials and designs.Purpose: The purpose of this in vitro investigation was to evaluate and compare the fracture resistance and failure mode of a newly proposed occlusal veneer design constructed of zirconia reinforced lithium silicate and hybrid ceramic materials with the conventional design restored with the same tested materials.Materials and Methods: Two mandibular first molars of a typodont were chosen to perform the master preparations; one for the conventional planar occlusal veneer design, and the second for the proposed modified design which consisted of occlusal veneer preparation with circumferential chamfer finish line and two shallow proximal slots. Ten elastomeric impressions were taken for each design using the putty and light polysiloxane addition silicone impression material. The twenty impressions were poured using type IV dental stone to produce twenty stone casts, ten for each design. Each group of stone casts was subdivided randomly into two equal subgroups according to the ceramic material to be tested; the zirconia reinforced lithium silicate “Celtra Duo” and the hybrid resin nano ceramic “Lava Ultimate”. All the occlusal veneers were fabricated using the CAD/CAM Cerec InLab SW 4.2.5 System. The veneers were then checked on both the stone casts and the master preparation on the typodont for perfect seating, after the Celtra veneers were crystallized and glazed and the Lava veneers being subjected to finishing and polishing. The preparations were duplicated to obtain twenty epoxy casts over which the occlusal veneers were adhesively cemented using a standard bonding protocol. The samples were then subjected to thermal cycling program. All the samples were individually mounted on the Instron testing machine with a loadcell of 5 KN and fracture test was done by compressive mode of load applied occlusally using a metallic rod with spherical tip (5.6 mm diameter) at cross-head speed of 1mm/min. The load required to fracture was recorded in Newton and tabulated to be statistically analyzed. The fractured specimens were examined to detect the mode of failure. Results: Regardless of the ceramic type, the modified occlusal veneer design showed statistically significant higher fracture resistance mean value (1106.0 N) than conventional design (957.6 N) at P ≤ 0.05. Irrespective of the design, the Lava Ultimate revealed higher statistically significant fracture resistance mean value (1114.1 N) than Celtra (949.5 N) at P ≤ 0.05. The Celtra veneers showed higher fracture resistance mean value (1016.9N) with the conventional design than the modified design (882.2 N), the difference was statistically significant at P ≤ 0.05. While the lava veneers presented higher statistically significant fracture resistance mean value with the modified design (1329.9 N) than the conventional design (898.3 N) at P ≤ 0.05. All the specimens exhibited cracks limited to the veneer material, except one revealed catastrophic failure.Conclusions: 1- The modified occlusal veneer design offered promising results as far as fracture resistance is concerned particularly with the nano-hybrid ceramic which presented the highest statistically significant fracture resistance mean values.2- The conventional planar occlusal veneer design proved to be superior with zirconia lithium silicate ceramic (ZLS) as it presented highly significant fracture resistance mean values than with the modified design.3- Both the conventional and modified occlusal veneer designs presented fracture resistance mean values with the two tested materials “Celtra and Lava Ultimate” that exceed the range of clinical acceptability.4- Rating of the tested occlusal veneers according to their fracture resistance mean values is as follows: the highest for the Lava Ultimate with the modified design, followed by Celtra Duo with conventional design, then Lava Ultimate with conventional design and Celtra Duo with modified design.5- It can be recommended that in cases with increased occlusal stresses, Lava Ultimate occlusal veneer with the modified design be the first choice, followed by the Celtra Duo with the conventional design as a second choice.

SEALING OF BONDED RESIN COMPOSITE TO GINGIVAL WALL FOLLOWING APPLICATION OF TWO HEMOSTATIC AGENTS USING TWO ADHESIVE PROTOCOLS: AN INVITRO STUDY

Aim: To evaluate the microleakage of self-etch adhesive used with and without pre-etching step, on human dentin contaminated with two different hemostatic agents. Materials and methods Thirty human premolars were collected and class V cavities with standard dimensions were prepared at the cemento-enamel junction on both buccal and lingual surfaces, with the gingival margin is totally placed in dentin. All specimens were randomly assigned into three groups according to the hemostatic agent used (A); A0: No hemostatic agent applied (control group). A1: Hemostop (Dentsply). A2:ViscoStat® (Ultradent). Each group was furtherly subdivided into two subgroups according to the adhesive protocol used (B); B1: Pre-etching was performed. B2: Pre-etching was not performed. The resultant will be six subgroups, each of them was formed of five teeth with 10 cavities (n=10). Filtek™ Z350 XT nano resin was used to restore all cavities according to the manufacturer’s instructions. Teeth were exposed to a thermocycling procedure, thereafter, they were stored in artificial saliva for two years. After immersion in 2% methylene blue dye, Microleakage was measured using USB Digital microscope with a built-in camera connected with an IBM compatible personal computer using a fixed magnification of 40X. Results: A two-way unrelated ANOVA showed significant main effects (p=0.0001) for hemostatic agent, with large effect size η2=86.5%, adhesive protocol with medium effect size η2=68.6%, and the interaction between hemostatic agent and adhesive protocol but with small effect size η2=34.2%.The Duncan post-hoc test revealed a significant difference between all groups except between the groups of Viscosat with pre-etching adhesive protocol (0.54 ± 0.03) on one hand and Hemostop with and without pre-etching adhesive protocol (0.53 ± 0.02) and (0.61 ± 0.04), respectively on the other hand (p > 0.05 ). Conclusions: 1. Contamination with hemostatic agents adversely affected the bonding qualities of self etch adhesives applied with and without pre etching step. 2. Dentin etching prior to self etch adhesives minimized the harmful effect of the hemostatic agents

In vitro Fracture strength and hardness of different computer-aided design/computer-aided manufacturing inlays.

The purpose of this study was to examine the fracture strength and surface microhardness of computer-aided design/computer-aided manufacturing (CAD/CAM) materials in vitro. Mesial-occlusal-distal inlays were made from five different CAD/CAM materials (feldspathic ceramic, CEREC blocs; leucite-reinforced ceramic, IPS Empress CAD; resin nano ceramic, 3M ESPE Lava Ultimate; hybrid ceramic, VITA Enamic; and lithium disilicate ceramic, IPS e.max CAD) using CEREC 4 CAD/CAM system. Samples were adhesively cemented to metal analogs with a resin cement (3M ESPE, U200). The fracture tests were carried out with a universal testing machine. Furthermore, five samples were prepared from each CAD/CAM material for micro-Vickers hardness test. Data were analyzed with statistics software SPSS 20 (IBM Corp., New York, USA). Fracture strength of lithium disilicate inlays (3949 N) was found to be higher than other ceramic inlays (P < 0.05). There was no difference between other inlays statistically (P > 0.05). The highest micro-Vickers hardness was measured in lithium disilicate samples, and the lowest was in resin nano ceramic samples. Fracture strength results demonstrate that inlays can withstand the forces in the mouth. Statistical results showed that fracture strength and micro-Vickers hardness of feldspathic ceramic, leucite-reinforced ceramic, and lithium disilicate ceramic materials had a positive correlation.

Comparative Study between Resin Nano Ceramic and CAD/CAM Ceramic Regarding Their Fracture Resistance, Microtensile Bond Strength and Fatigue Resistance

Purpose: In an attempt to improve the mechanical properties, industriallyCAD/CAM ceramics blocks have been introduced to dentistry. This study was directed to investigate the influence of the material thickness on the fracture resistance ofCAD/CAM Resin Ceramic and CAD/CAM Ceramic and asses the fatigue resistance of class II mesio-occlusal-distal (MOD) inlays of both materials and compare their micro-tensile bond strength (μTBS) after cementation by two different adhesive resin cements. Materials and Methods: A total of 70 specimens were fabricated. The specimens were divided according to the material used into two main groups (n= 35). Group 1 specimens were fabricated from CAD/CAM Resin Ceramic (Vita Enamic), whereas Group 2 specimens were fabricated from Lithium disilicate glass ceramic (IPS e-max CAD). Specimens of each group were further subdivided into 3 subgroups according to type of testing (microtensile bond strength test, fracture resistance and fatigue resistance tests). Specimens of subgroup of microtensile bond strength test (n=40) were further subdivided into 2 divisions (n=20) according to type of surface treatment (control and sandblasting). Then each division was further subdivided into 2 subdivisions (n=10) according to type of cement used (Rely X Ultimate and multilink N). Furthermore, subgroup of fracture resistance test (n=20) was further divided into 2 division (n=10) according to thickness (0.5 mm and 3 mm). Two-way analysis of variance ANOVA test and three-way analysis of variance ANOVA test of significance were done for comparing variables. Results: For microtensile bond strength, it was found that the highest μ-tensile bond strength value was recorded for Multilink N control subgroup (54.07±7.9 MPa), while the lowest μ-tensile bond strength mean values was for Rely X Ultimate sandblasted subgroup (37.12±2.5 MPa) and IPS e-max CAD. Results revealed that the highest μ-tensile bond strength mean value was recorded for Rely X Ultimate

Mechanical behaviour of nano jute filler glass fiber self healing and epoxy resin composite

In this paper presented the comparison of the tensile and compressive strengths of nano jute fiber composite under varying percentage of weight fractions of jute fiber as interlayer of glass fiber epoxy composite and nano jute self healing epoxy glass fiber composite . The used ratio of glass fiber and epoxy resin is 1:1. Hand layup method is employed for fabricating the samples and trimmed them under ASTM standards for experimentation. It is observed that the tensile and compressive strengths of self healing nano jute fiber composite is better than the epoxy resin nano jute glass fiber composite.

Internal fit of lithium disilicate and resin nano-ceramic endocrowns with different preparation designs

PurposeInvestigation of different central cavity designs on internal fit of endocrowns fabricated from two materials. Materials and methodsForty maxillary premolars were endodontically treated and divided into 8 groups [n = 5]: LS10, LS6, LD10, LD6, ES10, ES6, ED10 and ED6 (“L” restored with Lava™ Ultimate [resin nano ceramic], “E” restored with IPS e.max® CAD [lithium disilicate], “S” shallow depth [3 mm], “D” extended depth [5 mm], “6”-degree and “10”-degree axial wall divergence). All restorations were fabricated using CEREC CAD/CAM system. Samples were tested for internal fit using CBCT imaging (Next Generation i-CAT scanner) before and after adaptation. Data was tabulated and statistically analyzed. ResultsLava™ Ultimate showed significant better internal fit compared to IPS e.max® CAD endocrowns both before and after adaptation [p = 0.007 and 0.003, respectively]. Samples with 6-degree axial wall divergence showed significant better internal fit compared to those with 10-degree axial wall divergence before adaptation [p = 0.041].Before adaptation, group LS6 showed the best internal fit [403.00 ± 115.30 μm] followed by LD6, LD10, ES6, ES10, ED10, LS10 and ED6. After adaptation, group LS10 showed the best internal fit [394.80 ± 21.17 μm], followed by LS6, LD10, ED6, LD6, ES6, ED10, and ES10. ConclusionResin nano-ceramic endocrowns presented better internal adaptation compared to lithium disilicate endocrowns, regardless of the preparation design.

Effect of Different Preparation Designs on the Fracture Load of Two Machinable Laminate Veneers

Aim: The present study was performed to evaluate the effect of different preparation designs [window, butt- Joint, and incisal overlap], on the fracture load of two CAD / CAM laminate veneer materials [Zirconia CAD / CAM and resinnanoceramic ; lava ultimate].Materials and Methods: Thirty maxillary anterior teeth were restored with ceramic laminate veneers and divided into 6 groups as follows: group I-A (laminates made of Ultra translucent zirconia CAD with window preparation design), group I-B (laminates made of Ultra translucent zirconia CAD with butt-joint preparation design), group I-C (laminates made of Ultra translucent zirconia CAD with incisal overlap preparation design), group II-A (laminates made of Lava ultimate (Resin nano ceramic) CAD with window preparation design), group II-B (laminates made of Lava ultimate CAD with butt-joint preparation design), group II-C (laminates made of Lava ultimate CAD with incisal overlap preparation design). Fracture load test was performed using the Universal Testing Machine (UTM). Data were statistically analyzed using One-way analysis of variance ANOVA followed by Tukey’s multiple comparisontest. The results of the fracture load test were recorded in Newton: (I-A: 288.08N);(I-B: 322.47N); (I-C: 365.38N); (II-A: 301.15N); (II-B: 324.94N); (II-C: 394.95N). The results of the current study showed that there was no statistically significant difference between the means of fracture load for window, butt-joint and incisal overlap preparation designs among zirconia material. While, there was statistically highly significant difference between the means of fracture load for window, butt-joint and incisal overlap preparation designs among Lava ultimate material. The mean of fracture load for incisal over-lap preparation design was the highest, followed by butt-joint and window designs. Nonetheless, there were no statistically significant differences between translucent zirconia and lava ultimate regarding the fracture loadamong window, butt-joint and incisal overlap preparation designs.

Fracture resistance of zirconia and resin nano ceramic implant abutments according to thickness after thermocycling

Fracture resistance of zirconia and resin nano ceramic implant abutments according to thickness after thermocycling

Fracture strength of CAD/CAM fabricated lithium disilicate and resin nano ceramic restorations used for endodontically treated teeth.

The purpose of the present study was to evaluate and compare the fracture strength and failure modes of endocrowns, zirconia post, and fiber post supported restorations and predict the clinical outcomes of six different prostheses used for endodontically treated teeth. Sixty (n=10) maxillary central incisors were restored with zirconia post/resin-nano-ceramic crown (ZrRNC), fiber post/resinnano-ceramic crown (FbRNC), zirconia post/lithium disilicate ceramic crown (ZrLDS), fiber post/lithium disilicate ceramic crown (FbLDS), resin-nano-ceramic endocrown (EndoRNC), and lithium disilicate ceramic endocrown (EndoLDS). Fracture strength test was performed. Fracture loads and modes were determined. The EndoLDS group had the highest fracture strength, followed by ZrRNC and EndoRNC group. However the results were not significantly different among groups (p>0.05). The failure modes of the restorations changed according to the restorative materials. Endodontically treated anterior teeth might be restored with endocrowns as well as other post-core restorations, however tooth fracture failures should be considered that affect reliability of endocrowns.

Fatigue behavior of resin-modified monolithic CAD–CAM RNC crowns and endocrowns

ObjectiveTo evaluate the influence of different types of modifications with resin on fatigue resistance and failure behavior of CAD–CAM resin nano ceramic (RNC) restorations for maxillary first premolars. MethodsSixty standardized resin composite root dies received CAD–CAM RNC endocrowns (n=30) and crowns (n=30) (Lava Ultimate, 3M Espe). Restorations were divided into six groups: full anatomic endocrowns (group A) and crowns (group D), buccal resin veneered endocrowns (group B) and crowns (group E) and buccal resin veneered endocrowns (group C) and crowns (group F) with a central groove resin filling. A nano-hybrid resin composite was used to veneer the restorations (Filtek Supreme, 3M Espe). All specimens were first submitted to thermo-mechanical cyclic loading (1.7Hz, 49N, 600000 cycles, 1500 thermo-cycles) and then submitted to cyclic isometric stepwise loading (5Hz) until completion of 105000 cycles or failure after 5000 cycles at 200N, followed by 20000 cycles at 400N, 600N, 800N, 1000N and 1200N. In case of fracture, fragments were analyzed using SEM and modes of failure were determined. Results were statistically analyzed by Kaplan–Meier life survival analysis and log rank test (p=0.05). ResultsThe differences in survival between groups were not statistically significant, except between groups D and F (p=0.039). Endocrowns fractured predominantly with a mesio-distal wedge-opening fracture (82%). Partial cusp fractures were observed above all in crowns (70%). Analysis of the fractured specimens revealed that the origin of the fracture was mainly at the occlusal contact points of the stepwise loading. SignificanceVeneering of CAD–CAM RNC restorations has no influence on their fatigue resistance except when monolithic crowns are modified on their occlusal central groove.

Effect of Food Simulating Liquids and Thermo-cycling on flexural strength and surface hardness of a Resin Nano-Ceramic CAD/CAM Material

Purpose: Evaluate the effect of food simulating liquids and thermocycling on miniflexural strength and surface micro-hardness of a resin nano-ceramic material (Lava Ultimate) compared to indirect laboratory composite resin material (Nexco Paste) and direct composite resin material (Filtek Z350 XT).Material and Methods: A total number of 180 samples were fabricated. The samples were divided equally into 3 groups (n=60). Group 1 (M1) samples were fabricated from the resin nano ceramic CAD/CAM blocks (Lava Ultimate), group 2 (M2) samples were farbricated form indirect micro-hybrid resin composite (Nexco Paste), while group 3 (M3) samples were fabricated from direct resin composite (Filtek Z350 XT). Thirty bars (12X2X2mm) from each material were fabricated to evaluate the mini flexural strength. Thirty disks (8X2mm) were fabricated from each material to evaluate thesurface micro-hardness. The samples of M1 groups were fabricated by cutting from the CAD/CAM block using low speed diamond disk while samples of M2 and M3 samples were fabricated using teflon mold. Each material samples were further subdivided into 6 subgroups; the first subgroup was not immersed into food simulating liquids nor thermocycled,4 subgroups samples were immersed into food simulating liquids (water, ethanol, heptane and citric acid) and the last subgroup samples were thermocycled. Mini flexural strength test was done using universal testing machine and surface hardness was done using Vickers hardness tester.Results: Lava Ultimate showed the significantly highest mini flexural strength and surface micro-hardness values before and after immersion into food simulating liquids and thermocycling compared to the two other tested materials. Conclusion: According to the results of the present study, Lava Ultimate showed better mini flexural strength and surface micro-hardness compared to the two othertested materials.

Effect of Curing Mode on Shear Bond Strength of Self-Adhesive Cement to Composite Blocks.

To overcome the disadvantages of computer-aided design/computer-aided manufacturing (CAD/CAM) processed indirect restorations using glass-ceramics and other ceramics, resin nano ceramic, which has high strength and wear resistance with improved polish retention and optical properties, was introduced. The purpose of this study was to evaluate the shear bond strength and fracture pattern of indirect CAD/CAM composite blocks cemented with two self-etch adhesive cements with different curing modes. Sand-blasted CAD/CAM composite blocks were cemented using conventional resin cement, Rely X Ultimate Clicker (RXC, 3M ESPE, St. Paul, MN, USA) with Single Bond Universal (SB, 3M ESPE, St. Paul, MN, USA) for the control group or two self-adhesive resin cements: Rely X U200 (RXU, 3M ESPE, St. Paul, MN, USA) and G-CEM Cerasmart (GC, GC corporation, Tokyo, Japan). RXU and GC groups included different curing modes (light-curing (L) and auto-curing (A)). Shear bond strength (SBS) analyses were performed on all the specimens. The RXC group revealed the highest SBS and the GC A group revealed the lowest SBS. According to Tukey’s post hoc test, the RXC group showed a significant difference compared to the GC A group (p < 0.05). For the curing mode, RXU A and RXU L did not show any significant difference between groups and GC A and GC L did not show any significant difference either. Most of the groups except RXC and RXU L revealed adhesive failure patterns predominantly. The RXC group showed a predominant cohesive failure pattern in their CAD/CAM composite, LavaTM Ultimate (LU, 3M ESPE, St. Paul, MN, USA). Within the limitations of this study, no significant difference was found regarding curing modes but more mixed fracture patterns were showed when using the light-curing mode than when using the self-curing mode.

Effect of glycine pretreatment on the shear bond strength of a CAD/CAM resin nano ceramic material to dentin.

BackgroundThe purpose of this study was to evaluate the effect of glycine pretreatment on the shear bond strength between dentin and a CAD/CAM resin nano ceramic material (LavaTM Ultimate Restorative), bonded together with adhesive cements using three different luting protocols (total-etch; self-etch; self-adhesive).Material and MethodsThirty cylinders were milled from resin nano ceramic blocks with CAD/CAM technology. The cylinders were subsequently cemented to the exposed dentin of 30 bovine permanent mandibular incisors. The specimens were assigned into six groups of five teeth each according to luting procedure and dentin pretreatment. In the first two groups (A1, A2) 10 cylinders were cemented using a total-etch protocol; in groups B1 and B2, 10 cylinders were cemented using a self-etch protocol; in groups C1 and C2, 10 cylinders were cemented using a self-adhesive protocol; in groups A1, B1 and C1 the dentinal surface was also treated with glycine powder. All cemented specimens were submitted to a shear bond strength test. Statistical analysis was performed with Stata 9.0 software.ResultsANOVA showed the presence of significant differences among the various groups (P <0.0001).ConclusionsGlycine did not change the different bond strength demonstrated by the various luting protocols tested. Conventional resin composite cements used together with a self-etch adhesive reported the highest values. However the use of glycine seems to increase the bond strength of self-adhesive resin cements. Key words:Adhesive cements, CAD/CAM, glycine, luting system, resin nano ceramic, shear bond strength.