Dentin In Class Research Articles

Interfacial Stress and Bond Strength of Bulk-Fill or Conventional Composite Resins to Dentin in Class II Restorations

The aim was to evaluate the microtensile bond strength (mTBS) to dentin and interfacial stress in a class II cavity restored with bulk-fill or conventional composite resins and the margin interfaces. Vertical slot class II cavities in the mesial face, with the gingival end in dentin, were prepared in 72 third molars, being divided into groups (n=24): G1-Tetric N-Ceram; G2-Tetric N-Ceram Bulk-Fill; G3-SonicFill. Clearfil SE Bond adhesive system was used in all groups. Half of the teeth in each group (n=12) were submitted to thermo-mechanical cycling (TMC). Restored teeth (n=9) were cut perpendicular to obtain beams, which were submitted to a mTBS test in an EMIC machine. The cervical margins in dentin of the restored teeth (n=3) were assessed using SEM through epoxy resin replicas as well as the section of the restoration. Interfacial stresses after load application were calculated by 2D finite element analysis. The mTBS means-MPa followed by different letters represent statistical difference by ANOVA and Games-Howell's test (p<0.05): Without TMC: G1-15.68±6.10a; G2-10.08±5.21ab; G3-7.98±3.76b. With TMC: G1-9.70±5.52a; G2-5.79±1.42a; G3-4.37±1.87a. Interfacial stress (MPa) was 4.4 for SonicFill, 3.9 for Tetric N-Ceram, and 3.5 for Tetric N-Ceram Bulk-Fill. SEM images showed continuous margins for all composite resin restorations. It was possible to conclude that SonicFill obtained a slightly higher interfacial stress and lower bond strength to dentin in comparison with Tetric N-Ceram and Tetric N-Ceram Bulk-Fill. Continuous margin interfaces were obtained for Tetric N-Ceram, Tetric N-Ceram Bulk-Fill, and SonicFill. However, voids were observed in the SonicFill restorations.

Comparison of the effect of two MMP inhibitors on microtensile bond strength to dentin in class I cavities

Aim: To compare the effects of pretreatment with doxycycline and chlorhexidine on microtensile bond strength to dentin in class I cavities restored with composite resin. Materials and Methods: Class I cavities were prepared on the occlusal surface of 30 freshly-extracted caries-free molars. In group 1, 2% chlorhexidine was applied to the acid etched surface, placed in contact for 20 seconds, and gently air dried without rinsing. In group 2, 2% doxycycline was applied to the acid etched surface, placed in contact for 20 seconds, and gently air dried without rinsing. In group 3, the control group, just the conventional bonding procedure was used without any pre-treatment. The cavities were restored with resin composite using a bulk method. After thermocycling, the specimens were serially sectioned to obtain resin dentin sticks with a rectangular cross-sectional area of approximately 1mm2 using microtome. The microtensile bond strength values were tested using Universal testing machine at crosshead speed of 0.5 mm/min until failure. The results obtained were analyzed by One-way ANOVA and Tukey's HSD tests for statistical significance. Results: The pre-treatment with chlorhexidine and doxycycline showed a significant effect in preserving the in vitro bond strength, when compared to the control group (p=0.000). Among the test groups, the chlorhexidine treatment resulted in a higher bond strength value than doxycycline group (p=0.000). Conclusion: Pre-treatment with MMP inhibitors resulted in higher bond strength values. Chlorhexidine group showed a significantly higher bond strength value compared to the Doxycycline group. Keywords: Chlorhexidine, Dentin, Doxycycline, MMP inhibitors, Microtensile bond strength

CAD-FE modeling and analysis of class II restorations incorporating resin-composite, glass ionomer and glass ceramic materials

ObjectivesTo investigate the influence of specific resin-composite, glass ceramic and glass ionomer cement (GIC) material combinations in a “multi-layer” technique to replace enamel and dentin in class II mesio-occlusal-distal (MOD) dental restorations using 3D-Finite Element Analysis (FEA). MethodsFour 3D-FE models (A–D) of teeth, adhesively restored with different filling materials, were created and analyzed in comparison with a 3D model (E) of a sound lower molar. Models A, B & C had “multilayer” constructions, consisting of three layers: adhesive, dentin replacement and enamel replacement.Model A: had a low modulus (8GPa) composite replacing dentin and a higher modulus (12GPa) composite replacing enamel.Model B: had a GI cement replacing dentin and a higher modulus (12GPa) composite replacing enamel.Model C: had a low modulus (8GPa) composite replacing dentin and a very high modulus (70GPa) inlay replacing enamel.Model D: had a lithium disilicate inlay replacing both dentin and enamel with a luting cement base-layer.Polymerization shrinkage effects were simulated and a load of 600N was applied. All the materials were assumed to behave elastically throughout the entire deformation. ResultsModel A showed the highest stress distribution along all the adhesive interfaces of the shrinking resin-based materials with a critical condition and failure risk marginally and internally. Model D, by contrast, showed a more favorable performance than either of the multilayer groups (A–C). Stress and displacement plots showed an elastic response similar to that obtained for the sound tooth model. Model B and Model C performed according to their bilayer material properties. The use of a non-shrink dentin component simulating a GIC clearly affected the shrinkage stress at the basis of the Model B; while the bulk resin composite having a 12GPa Young’s modulus and linear polymerization shrinkage of 1% strongly influenced the biomechanical response in the bucco-lingual direction. SignificanceDirect resin-based composite materials applied in multilayer techniques to large class II cavities, with or without shrinking dentin layers, produced adverse FEA stress distributions and displacements. An indirect lithium disilicate inlay used to replace lost dentin and enamel in posterior restored teeth generated lower stress levels, within the limits of the elastic FEA model.

Assessment of current adhesives in class I cavity: Nondestructive imaging using optical coherence tomography and microtensile bond strength

ObjectivesTo evaluate the sealing ability and the microtensile bond strength (MTBS) of different adhesive systems bonded to dentin in class I cavities. MethodsRound tapered dentin cavities (3-mm diameter, 1.5-mm height) prepared in extracted human molars were restored using composite resin (Clearfil Majesty Posterior) with two-step etch-and-rinse adhesive system (Adper Single Bond 2: ASB2), two-step self-etch adhesive (Clearfil SE Bond: CSEB), all-in-one adhesives (G-Bond Plus: GBP; Tri-S Bond Plus: TSBP), or no adhesive (Control), or bonded using low-shrinkage composite with its proper adhesive (Filtek Silorane, Silorane Adhesive System: FSS). After 24-h water storage or 10,000 cycles of thermal stress, the specimens were immersed into a contrast agent. Two and three-dimensional images were obtained using optical coherence tomography (OCT). The mean percentage of high brightness (HB%) at the interfacial zone in cross-sectional images was calculated as an indicator of contrast agent or gap at the interface. The specimens were then sectioned into beams and the MTBS measured. ResultsThe HB% (ASB2=TSBP=CSEB<FSS=GBP) and MTBS (CSEB=ASB2, CSEB>TSBP=GBP=FSS, ASB2>FSS) differed significantly among the adhesives. After aging, HB% increased for GBP and FSS specimens, and the MTBS decreased for FSS specimens (ANOVA, Tukey's post hoc, p<0.05). The HB% and MTBS were significantly and negatively correlated (p=0.002). Confocal laser scanning and scanning electron micrographs confirmed contrast agent infiltration within the gap. SignificanceThere was a significant correlation between sealing performance and bond strength of the adhesives in the whole cavity. After aging, the two-step systems showed equal or superior performance to the all-in-one and Silorane systems.

The evaluation of various restoration techniques on internal adaptation of composites in class v cavities.

Aim. The aim of this study was to evaluate the effect of different restoration techniques on the formation of internal microgaps between materials and dentin in class V restorations. Materials and Methods. Twenty-five extracted human premolars were prepared with standardized class V cavity outlines (3 mm × 2 mm × 2 mm). The cavities were randomly divided into 5 groups of 10 cavities each and restored according to manufacturer's instructions: Group 1: preheating (55°C) conventional composite (Filtek Z250), Group 2: flowable composite (Filtek Flow), Group 3: Filtek Flow + Filtek Z250 light-cured separately, Group 4: Filtek Flow + Filtek Z250 light-cured simultaneously, and Group 5 (control): Filtek Z250 at room temperature (23°C). The specimens were then thermocycled and cross-sectioned through the center of the restoration. Subsequently, impressions were taken, and epoxy resin replicas were made. The internal adaptation of the materials to the axial wall was analyzed under SEM. Results. The preheated Filtek Z250 (Group 1) showed better internal adaptation than the room temperature groups (P < 0.05). The combination of Filtek Flow with Filtek Z250 which was light-cured separately (Group 3) exhibited better internal adaptation than control group (P < 0.05). Conclusion. Different restoration techniques exhibit different behavior regarding internal adaptation to dentin after photopolymerization.

Compatibility between silorane adhesive and simplified methacrylate-based adhesive systems

The purpose of this study was to evaluate the impact of replacing P90 primer with simplified adhesive systems (with a conventional, two-step adhesive or a self-etching, one-step adhesive) on bond strength to dentin in Class I restorations. The interfaces were also analyzed using confocal microscopy by adding a fluorophore to the adhesive components and SEM using silver nitrate for nanoleakage investigation. X-ray diffraction (XRD) characterized the chemical interaction of the adhesives. Failure mode and nanoleakage varied among groups. Characteristic micromorphology and higher nanoleakage were noted for silorane combinations. On the other hand, no signs of phase crystallization in the silorane adhesive combinations were noted. Replacing the silorane primer with simplified adhesives proved successful as the modified systems provided bonding to dentin comparable to that of the unmodified silorane systems. However, the dedicated adhesive exhibited signs of degradation immediately after application, which may impact the longevity of restorations in short periods.

Effect of different chlorhexidine application times on microtensile bond strength to dentin in Class I cavities

Objectives: This study evaluated the effect of 2% chlorhexidine digluconate (CHX) with different application times on microtensile bonds strength (MTBS) to dentin in class I cavities and intended to search for ideal application time for a simplified bonding protocol. Materials and Methods: Flat dentinal surfaces with class I cavities () in 40 molar teeth were bonded with etch-and-rinse adhesive system, Adper Single Bond 2 (3M ESPE) after: (1) etching only as a control group; (2) etching + CHX 5 sec + rinsing; (3) etching + CHX 15 sec + rinsing; (4) etching + CHX 30 sec + rinsing; and (5) etching + CHX 60 sec + rinsing. Resin composite was builtup with Z-250 (3M ESPE) using a bulk method and polymerized for 40 sec. For each condition, half of the specimens were immediately submitted to MTBS test and the rest of them were assigned to thermocycling of 10,000 cycles between and before testing. The data were analyzed using two-way ANOVA, at a significance level of 95%. Results: There was no significant difference in bond strength between CHX pretreated group and control group at the immediate testing period. After thermocycling, all groups showed reduced bond strength irrespective of the CHX use. However, groups treated with CHX maintained significantly higher MTBS than control group (p

Regional bond strength to lateral walls in class I and II ceramic inlays luted with four resin cements and glass-ionomer luting agent.

To investigate regional shear bond strength to lateral walls of ceramic inlays in occlusal and occlusoproximal cavities using etch-and-rinse and self-adhesive resin cements and a glass-ionomer luting agent. IPS e.max Press ceramic inlays were made in 50 Class I and 50 Class II standardized cavities in intact extracted human molars and divided into 5 luting agent subgroups (n = 10): Variolink II (VL); Multilink Sprint (MLS); Multilink Automix (MLA); RelyX Unicem (RLX), and Ketac Cem Aplicap (KC). Inlays were pre-etched with IPS Ceramic etching gel for 60s. After 48 h, two disks of ca 1.0 mm thickness, one of superficial and the other of deep dentin, were push-out tested in a universal testing machine at a crosshead speed of 1.0 mm/min. The mode of failure was determined under a stereomicroscope at 20X. Data were analyzed with one way ANOVA, and Scheffé's test was used for post-hoc comparisons (α = 0.05). There were no significant differences in shear bond strength between Class I and Class II cavities for the dual-curing system in light-curing mode (VL=MLS=RLX), except that RLX demonstrated greater bond strength to deep dentin in Class II cavities. Bond strength values were significantly higher on deep than on superficial dentin. KC showed the worst result. Failures were mixed (adhesive/cohesive) for the resin luting cements and solely adhesive (cement/ceramic) for the glass-ionomer luting agent. Dual-curing etch-and-rinse or self-etching self-adhesive resin luting cements achieved greater bond strength when light curing was applied, with no differences between Class I and Class II cavities but higher values for deep vs superficial dentin. The weakest adhesion was obtained with glass-ionomer luting agent in both cavity types.

Effect of Chlorhexidine Application Methods on Microtensile Bond Strength to Dentin in Class I Cavities

To evaluate the influence of chlorhexidine with different application methods on the microtensile bond strength (microTBS) to dentin in Class I cavities. Flat dentinal surfaces with Class I cavities (4 mm long, 4 mm wide, 2 mm deep) in 50 molars were bonded with Adper Single Bond 2 etch-and-rinse adhesive system after: 1) Chlorhexidine (CHX) + rinsing + etching; 2) CHX + no rinsing + etching; 3) Etching + CHX + rinsing; 4) Etching + CHX + no rinsing; 5) Etching only as a control group. Resin composite buildups were constructed with Z-350 (3M ESPE) using a bulk method and they were polymerized for 40 seconds. For each condition, half of the specimens were immediately submitted to microtensile bond strength and half of the same group was submitted to 10,000 cycles of thermocycling between 5 degrees C and 55 degrees C before testing. The data were analyzed using the two-way ANOVA and Student t-test at a 95% significance level. Chlorhexidine pretreatment did not affect the bond strength of specimens tested at the immediate testing period, regardless of the application method used, compared to the control group. However, after 10,000 thermocycles, a significant bond strength reduction was found in the control group. In general, the chlorhexidine application method did not demonstrate a significant difference among the groups treated with chlorhexidine. However, there was a significant difference after thermocycling in the groups treated with chlorhexidine before etching and no significant difference in the groups treated with chlorhexidine after etching. Considering the amount of reduction in bond strength after thermocycling, the current study showed improved dentin bond strength with chlorhexidine when used after etching.

Sealing effectiveness of light-cured glass ionomer cement liners

Glass ionomer materials have been used as liners or bases beneath restorations, but light-cured varieties have recently been introduced. Microleakage at the restoration/tooth interface in cervical cavities was used to test the adhesion to dentin of two new light-cured glass ionomer cement lining materials, XR-Ionomer and Fuji Lining LC. Wedge-shaped cervical cavities were prepared on extracted teeth with a gingival cavosurface margin involving dentin, and the specimens were assigned randomly to three groups. The experimental groups were restored with two light-cured glass ionomer cements, the controls were restored with a chemically cured glass ionomer cement; and marginal leakage was assessed by dye penetration. The two light-cured glass ionomer cements displayed some adhesion to dentin in class V test cavities, but there was no significant difference between the two materials.

Pulp reactions to silicate cement in teeth with healing pulpitis

Unlined silicate restorations were placed in intact and experimentally altered monkey, teeth. Pulpitis had been induced experimentally by sealing soft carious human dentin in Class V cavities with amalgam for 7 d. These fillings were then removed and healing allowed by inserting zinc oxide/eugenol cement. A protective effect of the secondary dentin in teeth with healing pulpitis could be demonstrated in short-term experiments. After a 1-month observation period no difference in response to silicate cement could be found between intact and experimentally altered pulps, both groups exhibiting no or slight pulp reactions and secondary dentin formations.