Composite Resin Blocks Research Articles

EFFECT OF DIFFERENT REPAIR PROTOCOLS ON BOND STRENGTH TO DIRECT AND INDIRECT RESIN COMPOSITE

Objective: This study was carried out to investigate the effect of different surface treatment protocols on bond strength of nano-composite as a repair material to two types of resin composite either direct composite or indirect resin composite blocks for CEREC system. Materials and methods: Total of 80 composite discs were prepared and were divided into two main groups (40 each) according to the type of composite used (C), nano-filled composite (C1) and composite blocks for CEREC system (C2). All specimens were aged for one month in a distilled water solution at 370C. Each group was sub-divided into four subgroups (10 each) according to the surface treatment protocol (T) that was done on the discs, either no treatment (T0) (control), application of Ortho phosphoric acid (T1), Hydrofluoric acid (T2) and Sandblasting(T3) . Each sub group was subdivided into two classes (5 each) according to silane application (S1) or without (S0). Nanofilled resin composite (Filtek Z350 XT, 3M ESPE) was used as a repair material. Microshear bond strength testing (μ-SBS) was done using Universal testing machine. Failure modes of the fractured specimens were analyzed using scanning electron microscope (SEM). μ-SBS results were analyzed using ANOVA, Tukey’s post-hoc and Student t-tests. Results: The indirect resin composite of the hydrofluoric acid group with silane showed the highest µ-Shear bond strength mean value (31.35±5.1) while the direct composite of the etchant group with no silane showed the lowest µ-Shear bond strength mean value (20.8±4.5). Regarding the composite type, C2 recorded statistically significant (P 0.05) highest µ-shear bond strength mean value (26.72±0.78 MPa) followed by T1 (25.77±2.55 MPa) then T2 (24.71±1.44 MPa) while T0 recorded statistically non- significant (P>0.05) lowest µ-shear bond strength mean value (24.54±1.7 MPa). Regarding the silane application, S1 recorded statistically non-significant (P>0.05) higher µ-shear bond strength mean value (26.28±1.57MPa) than S0(24.59±1.66MPa). Conclusions: The Cojet treatment of the resin composite improved the bond strength of different types of resin composite .The type of resin composite used for repair influences the bond strength to the repaired resin composite. Silane application to repaired resin composite affects the bond strength to it with different treatment protocols.

Shear bond strengths of various self-adhesive resin cements between bovine dentin and 4 types of adherends

The purpose of this study was to evaluate the shear bond strengths of self-adhesive resin cements that was applied similar to clinical condition between bovine dentin and four types of adherend. The self-adhesive resin cements, which were used in this study, included U-Cem Premium (U-Cem, Vericom), Rely X Unicem II Automix (Rely X, 3M ESPE), Maxcem Elite (Maxcem: Kerr) and Clearfil SA luting Cement (Clearfil, Kuraray). Four types of adherends, which were used in the research, included composite resin block for CAD-CAM (Polyglass Blank, Vericom), base metal (Vera Bond 2V, Albadent), zirconia (Mazic zir, Vericom) and lithium disilicate (IPS E.max, Ivoclar/Vivadent). The block of adherend was made with breadth 3 mm × length 3 mm × height 3 mm. It adhered adherend to bovine dentin, repeated photopolymerization twice by 20 seconds per surface in the status of applying the load in 5 N, added 30minutes to the holding time following the polymerization instructed by a maker, and then kept it in 37°C dry oven. The adhered specimen was kept for 24 hours in 37°C distilled water until before the experiment. The shear bond strength was measured with 0.75 mm/min cross-head speed by using a universal testing machine(Z020, Zwick, Ulm, Germany). The blade of the used jig was a straight line. The bond strength with resin adherend was the highest in Rely X. U-cem and Clearfil were significantly higher than Maxem.(p0.05). As for the bond strength with zirconia, Rely X and U-Cem were significantly higher than other self-adhesive resin cements(p0.05). In terms of the bond strength with metal and lithium disilicate, Rely X, U-Cem, Clearfil were significantly higher than Maxcem(p0.05). Hence, Rely X is recommended to the adhesion with the composite resin adherend. Rely X and U-Cem are recommended to the adhesion of zirconia. Maxem, which shows the lowest bond strength in all adherends, needs to be paid a great attention given being used in a clinical trial.

Effect of Storage Time on Bond Strength and Nanoleakage Expression of Universal Adhesives Bonded to Dentin and Etched Enamel.

To investigate bond strength and nanoleakage expression of universal adhesives (UA) bonded to dentin and etched enamel. Extracted human third molars were sectioned and ground to obtain flat surfaces of dentin (n = 36) and enamel (n = 48). Dentin and etched enamel surfaces were bonded with one of two UAs, All-Bond Universal (ABU) or Scotchbond Universal (SBU); or a two-step self-etching adhesive, Clearfil SE Bond (CSEB). A hydrophobic bonding resin, Adper Scotchbond Multi-Purpose Bond (ASMP Bond) was applied only on etched enamel. Following each bonding procedure, resin composite blocks were built up incrementally. The specimens were sectioned and subjected to microtensile bond strength (MTBS) testing after 24 hours or one year water storage, or immersed into ammoniacal silver nitrate solution after aging with 10,000 thermocycles and observed using scanning electron microscopy. The percentage distribution of silver particles at the adhesive/tooth interface was calculated using digital image-analysis software. The MTBS (CSEB = SBU > ABU, for dentin; and CSEB > ABU = SBU = ASMP Bond, for etched enamel) differed significantly between the adhesives after 24 hours. After one year, MTBS values were reduced significantly within the same adhesive for both substrates (analysis of variance, Bonferroni post hoc, p<0.05), and no significant differences were found among the adhesives for etched enamel. Silver particles could be detected within the adhesive/dentin interface of all specimens tested. Kruskal-Wallis mean ranks for nanoleakage in ABU, SBU, and CSEB were 16.9, 18.5 and 11, respectively (p>0.05). In the short term, MTBS values were material and dental-substrate dependent. After aging, a decrease in bonding effectiveness was observed in all materials, with nanoleakage at the adhesive/dentin interface. The bonding of the UAs was equal or inferior to that of the conventional restorative systems when applied to either substrate and after either storage period.

Effect of Bioglass 45S5 air-abrasion on dentin bonding: evaluation of microtensile bond strength and confocal microscopy

The aim of this study was to evaluate the influence of air-abrasion executed with Bioglass 45S5 on the bonding performance of total and self-etching techniques. Human molars were divided into four groups (n = 5) according to the surface treatment: G1: self-etching without air-abrasion; G2: total-etching without air-abrasion; G3: self-etching with air-abrasion Bioglass 45S5 for 1 min; and G4: total-etching with air-abrasion Bioglass 45S5 for 1 min. The Single Bond Universal (3 M ESPE, St. Paul, Minnesota, USA) was used in both etching techniques. The adhesive was photo-activated by a LED with 800 mW/cm2 irradiance (Ultralume 5, Ultradent Products, South Jordan, UT, USA). Composite resin blocks were made on the dentin using Filtek Z100 (3M ESPE, St. Paul, MN, USA). Then, the samples were cut to obtain sticks attached to a jig in a universal testing machine (EZ Test, Shimadzu, Kyoto, Kansai, Japan) for testing microtensile bond strength (μTBS). The values μTBS of microtensile bond strength were submitted to two-way ANOVA and means were compared by Tukey test (p < 0.05). The results showed significant differences in μTBS between G1 and G2. No differences were found between G3 and G4. For the self-etching technique no differences were found for G1 and G3. In total-etching, G2 showed greater μTBS than G4. The application of Bioglass 45S5 on dentin did not increase the microtensile bond strength in self-etching groups and decreased the bond strength values for total-etching groups, but improved the quality of the hybrid layer.

Effect of aging type and aged unit on the repair strength of resin composite to feldspathic porcelain in testing microtensile bond strength

The aim of the present study is to investigate the effect of aging type (thermocycling vs. water storage) and aged unit (block vs. stick) on the repair strength of resin composite to feldspathic porcelain in testing microtensile bond strength (μTBS). Ceramic specimens (N = 30) (10 × 5.7 × 4.5 mm3, Vita Mark II, Vita) were obtained from CAD–CAM blocks. One surface was etched with 10% HF and silanized. An adhesive was applied and resin composite blocks were constructed incrementally on the conditioned surface. The specimens were randomly divided into five groups (n = 6): Control (C): Non-aged; BTC: Blocks were thermocycled (5–55 °C, 6000 cycles); STC: Sticks were thermocycled; BS: Blocks aged in water storage (6 months) after themocycling; SS: Blocks aged in water storage (6 months) after thermocycling. After μTBS test, failure types were classified. Data (MPa) were statistically analyzed (1-way and Dunett and 2-way ANOVA, Tukey`s) (α = 0.05). Two-parameter Weibull distribution values including the Weibull modulus, scale (m), and shape (0) values were calculated. Aging type (p = 0.009) and aged unit (p = 0.000) significantly affected the results. Interaction terms were also significant (p = 0.000). Considering the stick level, there was no significant difference between thermocycling (STC: 25.7 ± 2.3) and water storage (SS: 25.3 ± 3.8) (p > 0.05) but the results were significantly higher when blocks were thermocycled (BTC: 31.6 ± 2.9) (p < 0.05). Weibull modulus and characteristic strength was the highest in BTC (m = 4.2; σo: 34.4) among all other groups (m = 3–3.9; σo: 14.6–28.5). Adhesive failures were common and cohesive failures occurred in less than 5% in all groups. Aging protocol was detrimental on durability of repair strength of resin composite to feldspathic porcelain. Exposing the sticks to either thermocycling or water storage aging should be considered in in vitro studies.

Influence of Nd:YAG laser on intrapulpal temperature and bond strength of human dentin under simulated pulpal pressure.

The aim of this study was to evaluate the effects of simulated pulpal pressure (SPP) on the variation of intrapulpal temperature (ΔT) and microtensile bond strength (μTBS) to dentin submitted to an adhesive technique using laser irradiation. One hundred sound human molars were randomly divided into two groups (n = 50), according to the presence or absence of SPP (15cm H2O). Each group was divided into five subgroups (n = 10) according to Nd:YAG laser energy (60, 80, 100, 120, 140mJ/pulse). The samples were sequentially treated with the following: 37% phosphoric acid, adhesive (Scotchbond Universal), irradiation with Nd:YAG laser (60s), and light curing (10s). ΔT was evaluated during laser irradiation using a type K thermocouple. Next, a composite resin block was build up onto the irradiated area. After 48h, samples were submitted to microtensile test (10kgf load cell, 0.5mm/min). Data were analyzed by two-way ANOVA and Tukey tests (p = 0.05). ANOVA revealed significant differences for ΔT and TBS in the presence of SPP. For ΔT, the highest mean (14.3 ± 3.23°C)(A) was observed in 140mJ and without SPP. For μTBS, the highest mean (33.4 ± 4.15MPa)(A) was observed in 140mJ and without SPP. SPP significantly reduced both ΔT and μTBS during adhesive procedures, lower laser energy parameters resulted in smaller ΔT, and the laser parameters did not influence the μTBS values.

Comparative in vitro wear resistance of CAD/CAM composite resin and ceramic materials

Statement of problemComposite resin is a promising option in computer-aided design and computer-aided manufacturing (CAD/CAM) dentistry; however, the wear resistance of composite resin remains a primary concern. PurposeThe purpose of this in vitro study was to evaluate the wear resistance of 5 CAD/CAM materials (n=10), consisting of 4 composite resins (3M Lava Ultimate, Kerr experimental composite resin material, Vita Enamic, 3M Paradigm MZ100) and 1 ceramic (Vita Mark II) in contact with natural human enamel cusps. Material and methodsSpecimens were loaded into a computer-controlled mastication simulator and subjected to 200000 mechanical cycles (49 N) against natural human enamel simultaneously with 500 thermal cycles (5°C to 50°C to 5°C). The wear resistance was analyzed by measuring the vertical substance loss (the maximum depth of the worn area) in the contact point area of the specimen. The worn surfaces were observed by scanning electron microscopy to determine the wear patterns. ResultsVita Mark II exhibited the best wear resistance among the tested materials, followed by 3M Lava Ultimate, Vita Enamic, and 3M Paradigm MZ100. The Kerr experimental material exhibited the lowest wear resistance, yet its results were not significantly different from those of the 3 other composite resin blocks (P>.05). ConclusionsWithin the limitations of this in vitro study, the wear resistance of composite resin blocks in contact with enamel cusps was significantly lower than that of a ceramic block.

Effect of erosive challenge and Nd:YAG laser irradiation on bond strength of adhesive systems to dentin

PurposeTo evaluate the effect of Nd:YAG laser irradiation and erosive challenge on bond strength of two adhesive systems to dentin. MethodsTwenty bovine incisors were cut and grounded to obtain eighty slabs of flat dentin. Specimens were allocated into eight groups, based on: adhesive system—a two-step etch-and-rinse and a two-step self-etch; laser irradiation—Nd:YAG (1W/10Hz) or control (no laser irradiation); and erosive challenge after restorative procedure—presence or absence of erosive challenge. Nd:YAG laser groups were submitted to laser irradiation before the restorative procedure. Blocks of composite resin were built up on the bonded surfaces with a Southern Dental Industries device to perform shear bond strength (SBS) test. After, each specimen of erosive challenge, groups were subjected to immersion in Sprite Zero® (20ml/2h/24°C/under agitation). The SBS test (0.5mm/min) was performed after 24h of water storage at 37°C. Failure mode was evaluated with a stereomicroscope (X400). Data were analyzed with three-way ANOVA and Tukey’s post hoc tests (α=0.05). ResultsThe etch-and-rinse adhesive system presented higher bond strength values than self-etch adhesive. Laser irradiation increased the bond strengths values when erosive challenge was present. The predominant failure mode observed was adhesive. ConclusionsThe irradiation of Nd:YAG laser positively influences the bond strength values when erosive challenges are present. Moreover, the etch-and-rinse adhesive system is a better option to be used in dentin in this clinical condition.

Does 2% chlorhexidine digluconate cavity disinfectant or sodium fluoride/hydroxyethyl methacrylate affect adhesion of universal adhesive to dentin?

The objectives of this study were to investigate the adhesion of a universal adhesive used either in total-etch (TE) or self-etch (SE) mode with and without 2% chlorhexidine digluconate cavity disinfectant (CHX) or sodium fluoride/hydroxyethyl methacrylate (NaF/HEMA) to dentin. Dentin surfaces of extracted human non-carious third molar teeth (N = 18) were exposed and randomly assigned to two groups. Half of the teeth were conditioned with TE and the others with SE adhesive mode. The teeth were then randomly divided into two groups where half were cleaned with 2% CHX (Cavity Cleanser, Bisco, CC) and the other half with NaF/HEMA (Aqua Prep F, Bisco, APF). Control groups in TE (C1) and SE (C2) adhesive system did not receive any cavity disinfectant. Dentin surfaces were conditioned with universal adhesive (Single Bond Universal, SBU) and resin composite blocks (3 M Z550) were bonded incrementally on the conditioned dentin using a mold. The teeth were stored in water for 48 h, and from each tooth, beam-shaped specimens (1 mm2) were prepared (n = 14, per group). Microtensile bond strength (MBS) was measured using a universal testing machine (1 mm/min). Data (MPa) were analyzed using one-way ANOVA and Tukey’s test (α = 0.05). Two-parameter Weibull distribution values including the Weibull modulus, scale (m), and shape (0) values were calculated. Mean MTBS results (MPa) showed significant difference between the experimental groups (p = 0.001) and were in descending order as follows: C1-CC (32.8 ± 6.4)a < C1 (24.4 ± 5.2)b < C2 (21.1 ± 4.8)b < C1-APF (19.3 ± 4.4)b < C2-CC (14.1 ± 4.1)c < C2-APF (8.1 ± 2.1)d. C1 and C2 presented non-significant bond strength of the resin composite bonded with SBU (p > 0.05). CC application significantly increased the bond strength in TE mode, but significant reduction was observed when used in SE mode (p < 0.05). The use of APF did not significantly decrease the bond strength in TE mode, but significant reduction was observed when used in SE mode. Considering Weibull parameters, characteristics of adhesion seem to be less reliable for C2-CC (m = 3.86) and more reliable for C1-CC (m = 6.77). Failure types were predominantly adhesive between the dentin and the adhesive resin. Mixed failures were more common for both C1 and C2 and total etch-CC combination.

Resin Bonding to a Hybrid Ceramic: Effects of Surface Treatments and Aging.

The aim of this study was to verify the effects of different surface treatments on the microtensile bond strength between resin cement and a hybrid ceramic. Thirty-two hybrid ceramic slices (8 × 10 × 3 mm) were produced and allocated among four groups according to the surface treatment: Cont = no treatment, HA = 10% hydrofluoric acid applied for 60 seconds, PA = 37% phosphoric acid applied for 60 seconds and CJ = air abrasion with silica particle coated alumina (Cojet Sand, 3M ESPE, 30 μm/2.8 bar). As a control group, eight blocks of feldspathic ceramic (8 × 10 × 3 mm) were etched by hydrofluoric acid for 60 seconds (VMII). After the surface treatments, the ceramic slices were silanized (except the Cont group) and adhesively cemented to composite resin blocks (8 × 10 × 3 mm ) with a load of 750 g (polymerized for 40 seconds each side). The cemented blocks were cut into beams (bonded surface area of ∼1 mm(2)). Half of the beams were aged (thermocycling of 5°C-55°C/6000 cycles + water storage at 37°C/60 days), and the other half were tested immediately after being cut. Data were analyzed by Kruskal-Wallis and Dunn tests (non-aged groups) and by one-way analysis of variance and Tukey test (aged groups; α=0.05%). The mode of failure was classified by stereomicroscopy. The surface treatment significantly affected the bond strength in each set of groups: non-aged (p=0.001) and aged (p=0.001). Before being aged, samples in the CJ, HA, and PA groups achieved the highest bond strength values. However, after being aged, only those in the HA group remained with the highest bond strength values. Adhesive failure was found most often. In conclusion, hydrofluoric acid etching should be used for surface conditioning of the studied hybrid ceramic.

Evaluation of 3-body wear of novel composite blocks for CAD/CAM

CAD/CAM generated dental restorations meet standardized manufacturing processes with uniform material quality, reproducibility of restorations and reduction in production costs. CAD/CAM systems in dentistry have rapidly gained importance and popularity, then various types of composite block were introduced as novel material. The purpose of this study were to evaluate the wear resistance of dental novel composite blocks for CAD/CAM.BR Four composite resin blocks (Lava Ultimate, Block HC, Cerasmart, KZR-CAD HR) and one composite ceramic block (Vita Enamic) for CAD/CAM were tested. Wear was simulated with an OHSU oral wear simulator, which simultaneously incorporates the wear mechanism of attrition and abrasion in three-body wear mode. Composite specimens were subjected to 50,000 cycles of wear against a steatite antagonist. Mixture of poppy seeds (2 g) and PMMA beads (1 g) in DW (10㎖) was used for 3-body abrasive medium. After wear simulation, average wear depths for abrasion wear and attrition wear were measured with the use of a 3D profilometer. Ten specimens were tested each group.BR Composite blocks showed excellent abrasion wear resistance (1.74-3.45 ㎛). Cerasmart showed the lowest attrition wear (5.85 ㎛), there were no significantly difference in attrition wear (12.28-14.07 ㎛) for the other four composite blocks (p0.05). Composite ceramic block showed the similar wear behavior to composite resin blocks. Correlation between fraction of ceramic and wear resistance was very low (R² = 0.1684).

What is the best protocol for bonding resin-modified glass ionomer cement to composite resin?

Objective: The objective of this study was to evaluate the bond strength of resin-modified glass ionomer cement (RMGIC) to composite resin considering the use of conventional and self-etching adhesive systems. Material and Methods: 60 RMGIC blocks (Riva, SDI) measuring 4 x 4 x 4 mm. were constructed. On the blocks, the application of different protocols of adhesive systems (n = 10) was carried out: Group 1 (Control) - without application of adhesive agent; Group 2 - 37% phosphoric acid + conventional adhesive agent Single Bond 2; Group 3 - conventional adhesive agent Single Bond 2; Group 4 – conventional adhesive agent Scotch Bond Multi-Purpose; Group 5 - self-etching adhesive Clearfil SE Bond; Group 6: self-etching adhesive Optibond Allin-One. Next, resin composite blocks measuring 4 x 4 x 4 mm were constructed (Venus, Heraeus Kulzer). The specimens were cut to obtain sticks which were submitted to microtensile bond strength test in a universal testing machine. The data were submitted to ANOVA and Tukey test (5%). Results: ANOVA showed a value of p &lt; 0.05, which indicated significant differences between the groups (in Mpa): Group 2 - 32.83; Group 5 - 31.2; Group 3 - 25,15b; Group 6 - 22.92; Group 4 - 22.15; Group 1 - 13.84. The analysis of fracture mode demonstrated that there was a predominance of adhesive and mixed fractures for all groups. Conclusion: The protocols of acid etching + conventional adhesive system Single Bond 2 (Group 2) or self-etching adhesive system Clearfil SE Bond (Group 5) increased the bond strength of RMGIC to the composite resin. The presence of an adhesive layer between the two materials tended to improve the bonding of RMGIC to composite resin.

Optimum pressure for the high-pressure polymerization of urethane dimethacrylate

ObjectivesThe aim of this study, part of our research to improve properties of resin composite blocks suitable for CAD/CAM and to better understand underlying mechanisms associated with high-temperature/high-pressure (HT/HP) polymerization, was to determine an optimum polymerization pressure of urethane dimethacrylate (UDMA) in the presence of an initiator (0.5% benzoyl peroxide) by determining the degree of conversion (DC) and viscoelastic properties of polymers obtained at 90°C under varying HP. MethodsDC and viscoelastic properties of 16 UDMA polymers, two controls (thermo-cured and thermo-cured followed by post-cure relaxation) and 14 experimental groups (HP polymers, in the range of 50–350MPa, in 50MPa increments, without and with post-cure relaxation) were determined via near infrared spectroscopic analysis and dynamic mechanical analysis, respectively. ResultsThe results have shown that HP UDMA polymers have DC superior to that of the control group. With regards to E′ and E″, the results have shown no significant difference between control and HP polymers. The damping factor, tanδ, decreased with increasing pressure, while E′rub and Tg increased. Polymerization at 150MPa or higher resulted in significantly higher E′rub and Tg. SignificanceThe results of this study suggested that HP polymerization at 90°C of UDMA reduced the number of defects and the free volume, leading to a more homogeneous polymer network. The results have also suggested that 200MPa is an optimum polymerization pressure, resulting in polymers with significantly higher DC, E′rub, and Tg, while maintaining adequate damping capacity (tanδ).

Wear resistance of CAD/CAM composite resin blocks

Purpose: The aim of the study was to investigate twoand three-body wear resistance of CAD/CAM composite resin blocks. Methods and materials: Six composite resins (AVE, BLO, CER, GRA, KZR, and ULT), one hybrid ceramic (ENA) and one feldspar ceramic (VIT) block materials for CAD/CAM were examined. Six specimens each were tested in a ball-on-disc wear device fitted with a zirconia ball (50N load, 1.2Hz) in water for two-body and in poppy seed slurry for three-body wear evaluation. Volume loss after 10k cycles was quantified using a digital CCD microscope. Statistical analysis: ANOVA and Tukey’s multiple comparisons (a=0.05). Results: Two-body wear for composite resin blocks was small, hybrid ceramic and ceramic blocks showed larger volume loss. Three-body wear was very low for all materials. All CAD/CAM composite resin block materials investigated displayed lowwear compared to previous data reported for direct posterior composites carrying out the same wear test. Conclusion:The blockmaterials are considered suitable for fabrication of single full crown restorations on premolar teeth.

Influence of surface treatment on shear bond strength between CAD/CAM composite resin block and repair resin

Influence of surface treatment on shear bond strength between CAD/CAM composite resin block and repair resin

In vitro evaluation of the wear resistance of composite resin blocks for CAD/CAM.

The aim of the study was to investigate two- and three-body wear of CAD/CAM blocks. Four composite resins, one hybrid ceramic and one feldspar ceramic block material were examined. Six specimens each were tested in a ball-on-disc wear device fitted with a zirconia ball (50 N load, 1.2 Hz, 50 k cycles) in water for two-body and in poppy seed slurry for three-body wear evaluation. Volume loss after each 10 k cycle was quantified using a digital CCD microscope. ANOVA and Tukey's multiple comparisons (α=0.05). Two-body wear for composite resin blocks was small, hybrid ceramic and ceramic blocks showed larger volume loss. Threebody wear was very low for all materials. All CAD/CAM block materials investigated displayed low wear compared to previous data for direct posterior composites carrying out the same wear test. The block materials are considered suitable for fabrication of single full crown restorations on premolar teeth.

Effect of dentin pretreatment and curing mode on the microtensile bond strength of self-adhesive resin cements.

PURPOSEThe aim was to evaluate the effect of curing mode and different dentin surface pretreatment on microtensile bond strength (µTBS) of self-adhesive resin cements.MATERIALS AND METHODSThirty-six extracted human permanent molars were sectioned horizontally exposing flat dentin surface. The teeth were divided into 12 groups (3 teeth/group) according to the dentin surface pretreatment methods (control, 18% EDTA, 10% Polyacrylic acid) and curing mode (self-curing vs. light-curing) of cement. After pretreatment, composite resin blocks were cemented with the following: (a) G-CEM LinkAce; (b) RelyX U200, followed by either self-curing or light-curing. After storage, the teeth were sectioned and µTBS test was performed using a microtensile testing machine. The data was statistically analyzed using one-way ANOVA, Student T-test and Scheffe's post-hoc test at P<.05 level.RESULTSFor G-CEM LinkAce cement groups, polyacrylic acid pretreatment showed the highest µTBS in the self-cured group. In the light-cured group, no significant improvements were observed according to the dentin surface pretreatment. There were no significant differences between curing modes. Both dentin surface pretreatment methods helped to increase the µTBS of RelyX U200 resin cement significantly and degree of pretreatment effect was similar. No significant differences were found regarding curing modes except control groups. In the comparisons of two self-adhesive resin cements, all groups within the same pretreatment and curing mode were significantly different excluding self-cured control groups.CONCLUSIONSelecting RelyX U200 used in this study and application of dentin surface pretreatment with EDTA and polyacrylic acid might be recommended to enhance the bond strength of cement to dentin.

Effect of Saliva on the Tensile Bond Strength of Different Generation Adhesive Systems: An In-Vitro Study.

Newer development of bonding agents have gained a better understanding of factors affecting adhesion of interface between composite and dentin surface to improve longevity of restorations. The present study evaluated the influence of salivary contamination on the tensile bond strength of different generation adhesive systems (two-step etch-and-rinse, two-step self-etch and one-step self-etch) during different bonding stages to dentin where isolation is not maintained. Superficial dentin surfaces of 90 extracted human molars were randomly divided into three study Groups (Group A: Two-step etch-and-rinse adhesive system; Group B: Two-step self-etch adhesive system and Group C: One-step self-etch adhesive system) according to the different generation of adhesives used. According to treatment conditions in different bonding steps, each Group was further divided into three Subgroups containing ten teeth in each. After adhesive application, resin composite blocks were built on dentin and light cured subsequently. The teeth were then stored in water for 24 hours before sending for testing of tensile bond strength by Universal Testing Machine. The collected data were then statistically analysed using one-way ANOVA and Tukey HSD test. One-step self-etch adhesive system revealed maximum mean tensile bond strength followed in descending order by Two-step self-etch adhesive system and Two-step etch-and-rinse adhesive system both in uncontaminated and saliva contaminated conditions respectively. Unlike One-step self-etch adhesive system, saliva contamination could reduce tensile bond strength of the two-step self-etch and two-step etch-and-rinse adhesive system. Furthermore, the step of bonding procedures and the type of adhesive seems to be effective on the bond strength of adhesives contaminated with saliva.

Uniaxial and biaxial flexural strengths of resin-composite CAD-CAM blocks

Uniaxial and biaxial flexural strengths of resin-composite CAD-CAM blocks

In silico multi-scale analysis of composite resin block for CAD/CAM

In silico multi-scale analysis of composite resin block for CAD/CAM