Effects of primer containing silane and thiophosphate monomers on bonding resin to a leucite-reinforced ceramic

Influence of silane coupling agent on the mechanical performance of flowable fibre-reinforced dental composites

OBJECTIVES

This experimental investigation explored the optimisation of silane treatment of surface-modified S-2 Glass fibres in restorative dental composites for improved mechanical performance. The influence of optimum amount of silane to improve the interfacial adhesion at the fibre-matrix interfaces and its effect on the mechanical properties of the restorative composites were explored.

METHODS

S-2 Glass fibres of 5 μm diameter and 250 μm length were surface modified using the acid etching technique. The etched fibres were then treated with either 3-methacryloxypropyltrimethoxysilane (3-MPS), 3-Glycidoxipropyltrimethoxysilane (3-GPS) or 8-methacryloxyoctyltrimethoxysilane (8-MOTS) at varying molar % / wt% concentrations. Fibres that were not silanised with any silane coupling agents were used as the control sample. The silanol content of each mixed silane was observed using Fourier transform infrared (FT-IR) spectroscopy analysis. Fibres (5 wt%) with optimised molar% / wt% silane coupling concentration were added to UDMA/TEGDMA dental resin. Mechanical properties such as flexural strength, flexural modulus, and the breaking energy of the materials were evaluated using a comprehensive experimental programme.

RESULTS

FTIR spectrum of glass fibre silanised with each silane coupling agent revealed many peaks from 3800 to 1400 cm^-1, indicative of -CH₃, -CH_2, and CO bonding, suggesting the proper silanization of the fibre. The contact angle test revealed that optimum wt% concentration of 3-MPS, 3-GPS and 8-MOTS were 0.5%, 0.8% and 1.4% respectively. The flexural strength of the fibre-reinforced with optimum concentration of 3-MPS (DC-3-MPS_0.5%) increased by 7.0% compared to those of the 2 wt% concentration of 3-MPS fibre-reinforced composite (DC-3-MPS_2.0%). While the flexural strength of optimum concentration 8-MOTS grafted dental resin composites (DC-8-MOTS_1.4%) were 9.9% higher than that of 2 wt% concentration 8-MOTS grafted dental resin composite (DC-8-MOTS_2.0%) and the flexural strength of optimum concentration of 3-GPS (DC-3-GPS_0.8%) was 7.5% higher when compared to that of 2 wt% concentration 3-GPS grafted dental resin composites (DC-3-GPS_2.0%). A concurrent trend was found while investigating the fracture behaviour of the dental composite with optimum wt% concentration of each silane coupling agent against its corresponding higher wt% concentrations. The ANOVA results showed that the optimum fibre-reinforced dental composites grafted with 8-MOTS showed better mechanical behaviour when compared to 3-GPS and 3-MPS.

SIGNIFICANCE

The interfacial adhesion between the fibre and the resin due to silane coupling agents has helped to improve the mechanical properties of the fibre-reinforced dental composite. This is the first experimental study to provide a thorough investigation into the significance of the optimal use of silane coupling agents to treat the S-2 Glass fibres and subsequently the influence on the mechanical performance of the fibre-reinforced flowable dental composites.

Using Geopolymer Technology on Synthesizing Leucite Ceramics

The aim of this study is to assess the process of synthesizing potassium-based geopolymers (KGL) into leucite ceramics with regard to five variables, namely, alkaline solution ratio (R), sintering time (S), calcining temperature (T), mixing time (M), and curing time (C). Under these conditions, the specimens were tested by the viscosity test, the mechanical properties test, X-ray diffraction (XRD), Fourier-transform infrared (FTIR) spectroscopy, and scanning electron microscopy (SEM) to understand the geopolymerization reactions and the characteristics of the KGL network. The results indicate that a KOH to K₂O/SiO₂ ratio of 1:1 promotes the reaction within metakaolin. XRD analysis of the KGL shows that, when the temperature is 1100 °C, the phase transforms into the leucite phase. Moreover, XRD analysis, mechanical properties, and FTIR all indicate improved characteristics when the curing time increases from 1 to 8 h. This might be attributed to the enhancement of the strong interaction between the matrix and the alkaline solution upon achieving adequate time to complete the geopolymerization process and forming a more stable three-dimensional structure. The formulation which formed the purest leucite phase consisted of: a 1:1 alkaline solution ratio, 10 min mixing time, 8 h curing time, 1200 °C calcining temperature, and 2 h sintering time.

Repair bond strength of composite to Er,Cr:YSGG laser irradiated zirconia and porcelain surfaces

BACKGROUND

Fracture or chipping are major concerning failures of an all-ceramic restoration. Repairing of the failure restoration using intra-oral technique is time saving and cost effective treatment modality. The present study was proposed to evaluate effect of Er,Cr:YSGG laser irradiation on shear bond strength between zirconia/porcelain and composite resin.

METHODS

Thirty zirconia and thirty zirconia based porcelain disc shape specimens were prepared. Three different surface treatment procedure were applied the specimens. For control groups (Group ZC and PC), instruction manual of an intra-oral porcelain repair system was followed. Different pulse rates of Er,Cr:YSGG laser irradiation (short and long pulses) were applied to zirconia and porcelain surfaces for other groups (Group ZS, ZL, PS, and PL). Porcelain repair kit was used to repair specimens using standard cylindrical teflon mold (2 × 2 mm). Repair bond strength of the repaired specimens was tested using a universal testing machine.

RESULTS

Highest mean bond strength value was observed at Group PC that was significantly higher than laser applied porcelain groups. Long pulse laser irradiation illustrated that increased mean bond strength compared to short pulse application on to the porcelain surface. Laser applied zirconia groups showed better mean bond strength than Group ZC, but differences between the groups were not statistically significant.

CONCLUSION

Different modes of Er,Cr:YSGG laser irradiation enhanced repair bond strength of the composite resin to zirconia, but these were not significant. Following the instruction manual for surface treatment on the porcelain surface was better method than Er,Cr:YSGG laser surface conditioning.

Comparison of access-hole filling materials for screw retained implant prostheses: 12-month in vivo study

BACKGROUND

Screw retained implant prostheses seem to be an efficient restorative method to prevent peri-implantitis caused by cement excess around the abutment. The drawback of the screw-retained prostheses is the difficulty to realize an efficient access-hole filling functionally and aesthetically. Up to now, few in vitro and in vivo studies were reported in the literature. The aim of this study was to evaluate clinical performances of two direct filling materials through a period of 12 months.

METHODS

To pursue a previous in vitro evaluation, this in vivo 12 months prospective study followed up and compared the access-hole filling integrity of a modified 4-META (4-methacryloxyethyl trimellitate anhydride)/MMA-TBB (methyl methacrylate-tri-n-butyl borane) - based resin (M4M) and a photo-polymerizing nano-hybrid composite resin (CR). Twenty-eight access-holes were filled with both materials respectively, then impressions and intra-oral photographs were taken at T = 0, T = 1 M (month), 3, 6, and 12 M. The access-hole surface measurement and the margin analysis (depth and angle) were carried out. The VAS (visual analogue scale) value on marginal discoloration and integrity at the baseline T = 0 and T = 12 M was recorded.

RESULTS

The mean values of the surface areas changes from T = 1 to T = 12 M were 83.3 ± 11.5% for group CR and 77.1 ± 13.1% for group M4M, respectively. (Mann-Whitney test p < 0.05, p = 0.046). The mean marginal depth at T = 12 M for group CR were 141.2 ± 125.5 μm and 132.1 ± 107.8 μm for the group M4M, respectively. (Mann-Whitney test p > 0.05, p = 0.58). The mean values of the angle formed at the margin (T = 12 M) were for group CR 39.5 ± 19.4° and 28.2 ± 17.2° for group M4M, respectively (Mann-Whitney test p < 0.0001). The photographical analysis by VAS values showed no significant difference between CR and M4M groups (Mann-Whitney test p > 0.05, p = 0.848).

CONCLUSIONS

Based on intra- and extra-oral evaluations with the limitation, both CR and M4M combined with a ceramic primer are indicated as promising materials to fill the access-hole. Further long-term investigation is necessary to confirm this finding.

Evaluation of thermal conductivity and flexural strength properties of poly(methyl methacrylate) denture base material reinforced with different fillers

STATEMENT OF PROBLEM

Poly(methyl methacrylate) (PMMA) is widely used in prosthodontics as a denture base material. However, it has several disadvantages, including low strength and low thermal conductivity.

PURPOSE

The purpose of this in vitro study was to evaluate thermal conductivity and flexural strength after adding powdered Ag, TiO₂, ZrO₂, Al₂O₃, SiC, SiC-nano, Si₃N₄, and HA-nano in ratios of 10 wt% to PMMA.

MATERIAL AND METHODS

A total of 144 specimens were fabricated and divided into 18 groups. Specimens were left in water for 30 days. Thermal conductivity values were measured using a heat flowmeter, flexural strength was measured with a 3-point bend test, and specimens were investigated with environmental scanning electron microscopy. One-way ANOVA was used to compare means followed by using Duncan multiple range test (α=.05).

RESULTS

The thermal conductivity value of PMMA increased significantly after the addition of Si₃N₄, SiC, Al₂O₃, SiC-nano, TiO₂, ZrO₂, HA-nano, and Ag. Progressive increases in thermal conductivity were observed in Si₃N₄, SiC, and Al₂O₃ fillers. Flexural strength values of the control group were not significantly different from those of the SiC, Al₂O₃, or Ag group (P>.05). In the other groups, flexural strength values decreased significantly (P<.05). On the basis of electron microscopy, we observed that Si₃N₄, SiC, and Al₂O₃ powders had higher thermal conductivity values that are dissipated more homogeneously in PMMA.

CONCLUSIONS

Although the addition of 10 wt% SiC, Al₂O_3, and Ag powder to PMMA significantly increased thermal conductivity, the flexural strength values of PMMA were not significantly changed.

Flexural Strength of Preheated Resin Composites and Bonding Properties to Glass-Ceramic and Dentin

To test the impact of preheating (25, 37, 54, or 68 °C) of TetricEvoCeram (TEC), FiltekSupremeXT (FSXT), and Venus (V) on flexural strength (FS), shear bond strength (SBS) and interfacial tension (IFT). FS was tested with TEC and FSXT. For SBS, glass-ceramic and human dentin substrate were fabricated and luted with the preheated resin composite (RC). SBSs of 1500 thermal cycled specimens were measured. For IFT, glass slides covered with the non-polymerized RC were prepared and contact angles were measured. Data were analyzed using 2/1-way ANOVA with Scheffé-test, and t-test (p < 0.05). Preheated TEC (37–68 °C) showed higher FS compared to the control-group (25 °C) (p < 0.001). FSXT presented higher FS than TEC (p < 0.001). For SBS to dentin higher values for FSXT than TEC were found. The preheating temperature showed no impact on SBS to dentin. SBS to glass-ceramic revealed a positive influence of temperature for TEC 25–68 °C (p = 0.015). TEC showed higher values than V and FSXT (p < 0.001). IFT values increased with the preheating temperature. A significant difference could be observed in every RC group between 25 and 68 °C (p < 0.001).

Effect of repeated firings on flexural strength of veneered zirconia

OBJECTIVE

Chipping and/or delamination represent a clinical failure of porcelain fused to zirconia (PFZ) prostheses. Causes and solutions have not been completely clarified. The present study was aimed at evaluating the effects of number of firings on the flexural strength of PFZ specimen.

METHODS

Forty-five zirconia specimens in shape of bars were cut, sintered and divided in 3 groups (n=15). Group 1: veneering ceramic was layered "in bulk" and fired. Group 2: veneering ceramic was layered in three layers, individually fired. Group 3: veneering ceramic was layered in five layers, individually fired. Each layer thickness was controlled by the use of calibrated molds. The total veneering ceramic thickness for all the specimens was 1.2mm, and the total thickness of the specimen of 2.0mm. Three-point bending test was performed. Fracture load was recorded in Newton and MPa value was calculated taking into account the bi-layered nature of the specimen. Data were statistically analyzed.

RESULTS

Specimens obtained with on single firing cycle obtained a statistically significant (p<0.001) lower flexural strength (54.61±8.98MPa) than specimens veneered with 3 or 5 firing cycles. The last two obtained very similar results (77.63±13.17MPa and 73.62±12.38MPa respectively) and the differences was not statistically significant.

SIGNIFICANCE

In bi-layered PFZ specimen, three to five layers and firings determine higher flexural resistance when compared to a single firing. Thus, a 3-layers veneering procedure is recommended to increase flexural resistance. If a 5-layer procedure is necessary to improve esthetics, it does not decrease flexural resistance.

Comparison of four silane primers and an isocyanate primer for bonding of tri-n-butylborane resin to a leucite-reinforced glass ceramic

PURPOSE

The purpose of the present study was to compare the effectiveness of an isocyanate monomer and four different silane monomers as primer components for bonding a leucite-reinforced glass ceramic (GN-Ceram Block).

METHODS

Four different methyl-methacrylate based primers, each with three different concentrations (1, 4, or 16wt%) of 2-methacryloxyethylisocyanate (MOI), 3-methacryloxypropylmethyldimethoxysilane (MDS), 3-methacryloxypropyltrimethoxysilane (MTS), and 3-acryloxypropyltrimethoxysilane (ATS) were prepared. A commercially available silane primer (ESPE™Sil) was also used as a control. The GN-Ceram Block specimen was ground with silicon carbide paper, rinsed, primed, and then bonded to a resin composite disk using a tri-n-butylborane-initiated self-curing luting agent. After 24-h immersion in water, the shear bond strengths were determined.

RESULTS

The highest level of bond strength was obtained with 4wt% MTS (45.2 MPa) and 4wt% ATS (38.7 MPa), followed by 4wt% MOI (29.8 MPa), ESPE™Sil (28.1 MPa), and 4wt% MDS (27.9 MPa). For each MTS, ATS, MOI, and MDS, the bond strengths for concentrations of 4wt% and 16wt% were not significantly different. No significant differences were found between 4wt% ATS, 4wt% MOI, ESPE™Sil, and 4wt% MDS. The use of any of these primers led to a significant increase in bond strength compared to an unprimed control (13.8 MPa).

CONCLUSIONS

The type and concentration of monomers dissolved in the primer influence the bond strength between a tri-n-butylborane resin and a leucite-reinforced glass ceramic GN-Ceram Block. The effectiveness of MOI was found to be comparable to that of MDS, ATS, and ESPE™Sil, but inferior to that of MTS.