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PubMed2004

Leachability of plasticizer and residual monomer from commercial temporary restorative resins.

OBJECTIVES: This study was performed to determine the compositions of commercial temporary restorative resins and to evaluate the leachability of plasticizer and residual monomer from them. METHODS: The chemicals in four commercial temporary restorative resins (Dura Seal, Fit Seal, Plast Seal Quick, and Poly Seal) were detected by GCMS and HPLC. The amounts of plasticizers and residual monomers that leached from cured resin samples immersed in ethanol for 1 h to 14 d were determined by HPLC. RESULTS: Phthalate esters used as plasticizers contained 40-55 wt% either di-n-butyl phthalate (DBP) or butyl phthalyl butyl glycolate. The resin monomer included methyl methacrylate (MMA) or a mixture of MMA and 2-hydroxyethyl methacrylate (HEMA); 1,3-butanediol dimethacrylate was added as a cross-linking agent. Each resin contained 40-60 wt% monomer. The amounts of phthalate esters leached increased with immersion time up to 7 d, reaching 120-190 microg/mg, and did not change subsequently. The residual monomers leached gradually for up to 3d and did not change subsequently. The amount of leached residual monomer (MMA, HEMA) was 20-90 microg/mg after 3d storage. More than 50% of the leachable plasticizers and monomers were eluted from the cured resins within 24 and 3 h, respectively. CONCLUSIONS: The amounts of leached plasticizers and residual monomers were extremely large compared with the concentrations of endocrine disrupters and their potentially genotoxic effects. Therefore, it is very important to evaluate the leachability of these compounds from temporary restorative resins.

Acrylic Resins↗
PubMed2004

Polymerization shrinkage: effects of boundary conditions and filling technique of resin composite restorations.

OBJECTIVE: To evaluate the linear polymerization shrinkage (LPS) and the effect of polymerization shrinkage of a resin composite and resin-dentin bond strength under different boundary conditions and filling techniques. METHODS: Two cavities (4 x 4 x 2 mm3) were prepared in bovine incisors (n=30). The teeth were divided into three groups, according to boundary conditions: In group TE, the total-etch technique was used. In group EE, only enamel was conditioned, and in group NE, none of the walls of the cavities were conditioned. A two-step adhesive system was applied to all cavities. The resin composite was inserted in one (B) or three increments (I) and light-cured with 600 mW/cm2 (80 s). The LPS (%) was measured in the top-bottom direction, by placing a probe in contact with resin composite during curing. Enamel and total mean gap widths were measured (400 x) in three slices obtained after sectioning the restorations. Then, the slices were sectioned again, either to obtain sticks from the adhesive interface from the bottom of the cavity or to obtain resin composite sticks (0.8 mm2) to be tested for tensile strength (Kratos machine, 0.5 mm/min). The data was subjected to a two-way repeated measures ANOVA and Tukey's test for comparison of the means (alpha=0.05). RESULTS: The highest percentage of LPS was found for the TE when bulk filled, and the lowest percentage of LPS was found in the EE and NE when incrementally filled. The resin-dentin bond strength was higher and the total mean gap width was lower for TE group; no significant effect was detected for the main factor filling techniques. No difference was detected for the tensile strength of resin composite among the experimental groups. CONCLUSIONS: The filling technique is not able to minimize effects of the polymerization shrinkage, and bonding to the cavity walls is necessary to assure reduced mean gap width and high bond strength values.

Analysis of Variance↗
PubMed2006

Effect of zirconium-oxide ceramic surface treatments on the bond strength to adhesive resin.

STATEMENT OF PROBLEM: Surface treatment methods used for resin bonding to conventional silica-based dental ceramics are not reliable for zirconium-oxide ceramics. PURPOSE: The aim of this study was to compare the effects of airborne-particle abrasion, silanization, tribochemical silica coating, and a combination of bonding/silane coupling agent surface treatment methods on the bond strength of zirconium-oxide ceramic to a resin luting agent. MATERIAL AND METHODS: Sixty square-shaped (5 x 5 x 1.5 mm) zirconium-oxide ceramic (Cercon) specimens and composite resin (Z-250) cylinders (3 x 3 mm) were prepared. The ceramic surfaces were airborne-particle abraded with 125-microm aluminum-oxide (Al(2)O(3)) particles and then divided into 6 groups (n = 10) that were subsequently treated as follows: Group C, no treatment (control); Group SIL, silanized with a silane coupling agent (Clearfil Porcelain Bond Activator); Group BSIL, application of the adhesive 10-methacryloyloxydecyl dihydrogen phosphate monomer (MDP)-containing bonding/silane coupling agent mixture (Clearfil Liner Bond 2V/ Porcelain Bond Activator); Group SC, silica coating using 30-microm Al(2)O(3) particles modified by silica (CoJet System); Group SCSIL, silica coating and silanization (CoJet System); and Group SCBSIL, silica coating and application of an MDP-containing bonding/silane coupling agent mixture (Clearfil Liner Bond 2V/Porcelain Bond Activator). The composite resin cylinders were bonded to the treated ceramic surfaces using an adhesive phosphate monomer-containing resin luting agent (Panavia F). After the specimens were stored in distilled water at 37 degrees C for 24 hours, their shear bonding strength was tested using a universal testing machine at a crosshead speed of 0.5 mm/min. Debonded specimen surfaces were examined with a stereomicroscope to assess the mode of failure, and the treated surfaces were observed by scanning electron microscopy. Bond strength data were analyzed using 1-way analysis of variance and the Duncan test (alpha = .05). RESULTS: The bond strengths (mean +/- SD; MPa) in the groups were as follows: Group C, 15.7 +/- 2.9; Group SIL, 16.5 +/- 3.4; Group BSIL, 18.8 +/- 2.8; Group SC, 21.6 +/- 3.6; Group SCSIL, 21.9 +/- 3.9; and Group SCBSIL, 22.9 +/- 3.1. The bond strength was significantly higher in Group SCBSIL than in Groups C, SIL, and BSIL (P<.001), but did not differ significantly from those in Groups SC and SCSIL. Failure modes were primarily adhesive at the interface between zirconium and the resin luting agent in Groups C and SIL, and primarily mixed and cohesive in Groups SC, SCSIL, and SCBSIL. CONCLUSION: Tribochemical silica coating (CoJet System) and the application of an MDP-containing bonding/silane coupling agent mixture increased the shear bond strength between zirconium-oxide ceramic and resin luting agent (Panavia F).

Air Abrasion, Dental↗
PubMed2000

Color stability of new-generation indirect resins for prosthodontic application.

STATEMENT OF PROBLEM: Several new-generation indirect resins are being advocated for full contour restoration of teeth. Previous indirect resin systems have failed in this application, due in part to color instability. PURPOSE: This study evaluated and characterized the color stability of various new-generation indirect resins (ceramic-polymers) when subjected to accelerated aging. MATERIAL AND METHODS: Four new-generation indirect resin systems, 1 direct resin system, and 1 dental porcelain control were subjected to accelerated aging for a period of 300 hours. Initial specimen color parameters were determined in the Commission International de l'Eclairage Lab (CIELAB) color order system with a colorimeter. Color changes (DeltaE) were calculated between baseline color measurements and measurements made after 150 and 300 hours of accelerated aging. Color difference data were subjected to a 1-way analysis of variance to examine the interaction between material and time interval of aging. Where significant interactions occurred, a least-squared means test was performed to identify differences in the color stability between the materials (P </=.05). RESULTS: After 300 hours of accelerated aging, color changes of the indirect resins ranged between 0.62 and 3.40 DeltaE units. Two of the products tested demonstrated color stability that was not significantly different from the porcelain control. CONCLUSION: All the indirect resins tested demonstrated color stability at or below a quantitative level that would be considered clinically acceptable. Color changes of ceramic-polymers occurred because of changes in chroma, rather than alterations in lightness.

Analysis of Variance↗
PubMed1997

Temperature rise in pulpal chamber during fabrication of provisional resinous crowns.

STATEMENT OF PROBLEM: The heat generated during the exothermic polymerization reaction of autopolymerizing resinous materials and the heat generated by ultraviolet lamps during irradiation of photopolymerizing resinous materials could cause pulpal damage when a direct technique is used to fabricate provisional restorations. This could occur if temperature elevations overcome the physiological heat dissipating mechanisms of the dental-periodontal system. PURPOSE: This in vitro study compared the rise in temperatures in the pulpal chamber during fabrication of provisional complete veneer crowns by direct method with different autopolymerizing and photopolymerizing resins. The effect of curing resinous crowns in different matrices, such as a polyvinyl siloxane impression and a vaccuum-formed polypropylene sheet, was also evaluated. RESULTS: The results demonstrated that the amount of heat generated during resin polymerization and transmitted to the pulpal chamber could be damaging to pulpal tissues including odontoblasts. When curing of provisional resinous crowns was performed in the polyvinyl siloxane impression, significantly lower temperatures were recorded compared with curing in the vacuum-formed polypropylene sheet. CONCLUSIONS: To prevent pulpal damage, effective cooling procedures are strongly recommended when directly fabricating resinous provisional crowns.

Analysis of Variance↗
PubMed1998

Effects of adhesive fixed prosthesis retainer design on resultant resin luting agent thickness.

STATEMENT OF PROBLEM: Resin cement thickness may influence the success or otherwise of adhesive fixed prostheses and needs to be quantified for future stress analyses. PURPOSE: This study evaluated the effect of different complexities of retainer preparation design on resultant resin lute thickness. MATERIAL AND METHODS: Five retainer designs were evaluated for resin luting thickness (Panavia Ex) after cementation to appropriately selected natural teeth as follows: (1) flat plate retainer; mandibular canine; (2) occlusal rests, mandibular premolar; (3) occlusal rests, proximal grooves, mandibular premolar; (4) modified three-quarter crown, mandibular premolar; and (5) occlusal strut, maxillary premolar. Five samples of each design were prepared in vitro. A mesiodistal and a buccolingual section were obtained from each sample with a diamond saw. Measurements were carried out on the fluorescent cement lute with a confocal microscope. Mean resin thickness and cervical resin thickness were analyzed with analysis of variance and Tukey tests. RESULTS: Resin thickness (micron) for each of the retainer designs were as follows (mean +/- SD): design 1, 58 +/- 40; design 2, 67 +/- 42; design 3, 80 +/- 28; design 4, 87 +/- 15; and design 5, 85 +/- 29. There were no significant differences among the designs (mean global value 75.4). The three-quarter crown (design 4) had a significantly wider cervical resin thickness (P < or = .01) than designs 1, 2, and 3.

Analysis of Variance↗
PubMed1997

Effect of microgravity on Escherichia coli and MS-2 bacteriophage disinfection by iodinated resins.

Experiments on chemical disinfection by iodinated resins were conducted on STS 50 (USML-1), which flew a 13 day mission during 1992. Fluid processing apparatus containing microorganisms and iodinated resins was assembled in either Manhattan, Kansas, or Boulder, Colorado, and loaded on-board the Space Shuttle for the mission. Pentaiodide resin was more effective than the triiodide resin against Escherichia coli. Both resins were more effective bactericides at unit gravity than microgravity because of cosedimentation of bacteria and iodinated resin beads. In bacteriophage experiments, the triiodide resin reduced the viable titer of MS-2 by nine logs. The few viable phage surviving chemical disinfection were associated with precipitant formation in the fluid processing apparatus.

Anion Exchange Resins↗
PubMed1998

Stereomicroscopic and scanning electron microscopic study of roots obturated with vertically condensed gutta-percha, epoxy resin cement, and dentin bonding agent.

Root canal fillings performed with dentin bonding agent, gutta-percha, and epoxy resin sealer were observed by stereomicroscope. Fourteen palatal roots of extracted maxillary molars were used. Seven roots (group 1) were filled with gutta-percha, epoxy resin sealer, and dentin bonding agent. Seven (group 2) were filled with gutta-percha and epoxy resin sealer alone. The presence of these materials (gutta-percha, adhesive, cement, and a combination of these materials) and the number of voids present were evaluated in the apical, middle, and coronal thirds of the canals. In group 1, a combination of the three materials used was found to be the statistically most frequent case only in the apical third. No statistically significant difference was found between the overall number of voids present in the two groups. The resin-dentin-gutta-percha interface of roots from group 1 was observed by scanning electron microscopy: no statistically significant difference was found between apical and coronal sections regarding the presence of hybrid layer, penetration of resin into the dentinal tubules, or the presence of gaps in either the dentin-resin interface or the resin-gutta-percha interface.

Bismuth↗
PubMed2003

Determination of residual double bonds in resin-dentin interface by Raman spectroscopy.

OBJECTIVES: The quality of the hybrid layer is believed to be more important than the thickness of this layer. The purpose of this study was to investigate a method to analyze the percentage of adhesive resin residual double bonds in the dentin-resin interface using laser Raman spectroscopy. METHODS: Bovine dentin was treated with dentin adhesives and resin composite was bonded according to the manufacturers' instructions. The specimens were sectioned parallel to dentinal tubules and the surfaces were then polished to 1 microm diamond pastes. Raman spectra were recorded along a line perpendicular to the dentin-resin interface in steps of 0.2 microm. The measurement of residual C=C bond was made on a relative basis by comparing the C=C unpolymerized methacrylate stretching vibration (1638 cm(-1)) against the C=O stretching mode of the ester group (1719 cm(-1)). The percentage of residual double bonds including pendant and monomeric double bonds was calculated by comparing the obtained ratio with that of uncured adhesive resin. RESULTS: The amount of residual double bonds in the hybrid layer varied from 10 to 25% compared to the uncured adhesives, a relatively higher percentage was detected for Fluoro Bond (12.3-23.6%) and Single Bond (9.5-21.8%), and lower for Mac Bond II (10.6-18.0%) and Mega Bond (10.7-16.3%). No relationship was seen between the percentage of remaining double bonds and the location within the resin-dentin interface. SIGNIFICANCE: Laser Raman microscopy used was a useful tool for measuring the residual double bonds in the dentin-resin interface.

Analysis of Variance↗
PubMed1996

Long-term mechanical characteristics of resin-modified glass ionomer restorative materials.

OBJECTIVES: The purpose of this study was to compare the effects of long-term water storage on the mechanical characteristics of four resin-modified glass ionomer restorative materials with those of a conventional glass ionomer cement and a resin composite material. METHODS: Cylindrical specimens were prepared and stored in water for 1 h, 24 h, 1 wk, 1 mon, 3 mon and 6 mon prior to determination of diametral tensile strength (DTS) and depth of surface indentation both under 1 N load and after removal of the load. RESULTS: Diametral tensile strength was lowest for the conventional glass ionomer cement and highest for the composite; the resin-modified glass ionomer cements were intermediate between the reference materials. Water storage reduced DTS between 24 h and 1 wk or 1 mon but then remained unaffected until the final measurements after 6 mon. The materials showed a trend toward a slight increase in the depth of indentation both under load and after removal of the load with increasing storage time. These mechanical properties indicate the position of four resin-modified glass ionomer cements on a continuum with conventional glass ionomer cement and resin composite as the end points. SIGNIFICANCE: The mechanical properties of resin-modified glass ionomers show that this group of materials is weaker than resin composite but stronger than conventional glass ionomer cement. Water storage for 6 mon has little adverse effect on the mechanical properties.

Analysis of Variance↗
PubMed1999

Effect of water on the physical properties of resin-modified glass ionomer cements.

OBJECTIVES: Resin-modified glass ionomer cements (GIC) are available for clinical use as restorative materials or as liners and bases. This work was conducted to study the effect of water sorption on the physical properties of several resin-modified GIC, by changing the samples' storage conditions. METHODS: The water sorption, the flexural strength, the flexural elastic modulus, the Vickers hardness and the dimensional changes of five resin-modified GICs were measured using specimens aged for 24 h to 3 mon. The specimens were stored at 37 degrees C, either in a dry environment (A), immersed in water (B), stored in a humid environment (C), stored in a humid environment for 1 h and then immersed in water (D), or immersed in water and subsequently dried (B + A). An analysis of variance was used to compare the results. RESULTS: The resin-modified GIC absorb during the first 24 h large amounts of water (114-172 mg/cm3) compared to the conventional GIC (30-63 mg/cm3). Water alters the physical properties of resin-modified GICs: With regard to dry specimens, a decrease in the flexural strength of 20 to 80% was observed for samples immersed in water. Decreases in their flexural elastic modulus (50 to 80%) and in their hardness (approximately 50%) were also observed. Water sorption also provoked an expansion in volume of the immersed specimens, ranging from 3.4 to 11.3% after 24 h. SIGNIFICANCE: The flexural strength and Vickers hardness of the resin-modified GICs are sensitive to the water contained in the tested specimens. A correlation was established between the decrease in their physical properties and the water uptake. However, it should not be concluded that these materials are not adequate for use in applications in direct contact with oral fluids. Probably, resin-modified GIC placed in oral cavities would not be affected to the same extent as in in vitro tests. In an oral environment, the constituents of saliva will certainly decrease the rate of water sorption and will hence delay its effects.

Absorption↗
PubMed2003

In vitro degradation of resin-dentin bonds analyzed by microtensile bond test, scanning and transmission electron microscopy.

Our knowledge of the mechanisms responsible for the degradation of resin-dentin bonds are poorly understood. This study investigated the degradation of resin-dentin bonds after 1 year immersion in water. Resin-dentin beams (adhesive area: 0.9mm(2)) were made by bonding using a resin adhesive, to extracted human teeth. The experimental beams were stored in water for 1 year. Beams that had been stored in water for 24h were used as controls. After water storage, the beams were subjected to microtensile bond testing. The dentin side of the fractured surface was observed using FE-SEM. Subsequently, these fractured beams were embedded in epoxy resin and examined by TEM. The bond strength of the control specimens (40.3+/-15.1MPa) decreased significantly (p<0.01) after 1 year of water exposure (13.3+/-5.6MPa). Loss of resin was observed within fractured hybrid layers in the 1 year specimens but not in the controls. Transmission electron microscopic examination revealed the presence of micromorphological alterations in the collagen fibrils after 1 year of water storage. These micromorphological changes (resin elution and alteration of the collagen fibrils) seem to be responsible for the bond degradation leading to bond strength reduction.

Biocompatible Materials↗
PubMed2000

Effect of altering the type of enamel conditioner on the shear bond strength of a resin-reinforced glass ionomer adhesive.

The purpose of this study was to determine the effects of changing the type of enamel conditioner on the shear bond strength of a resin-reinforced glass ionomer within half an hour after bonding the bracket to the tooth. Freshly extracted human molars were collected and stored in a solution of 0.1% (weight/volume) thymol. The teeth were cleaned and polished. The teeth were randomly separated into 4 groups according to the enamel conditioner/etchant and adhesive used: group I, teeth were conditioned with 10% polyacrylic acid and brackets were bonded with a resin-reinforced glass ionomer adhesive; group II, teeth were conditioned with 20% polyacrylic acid and brackets were bonded with a resin-reinforced glass ionomer adhesive; group III, teeth were etched with 37% phosphoric acid and the brackets were bonded with a resin-reinforced glass ionomer adhesive; group IV, teeth were etched with 37% phosphoric acid and the brackets were bonded with a composite adhesive. The results of the analysis of variance comparing the 4 experimental groups (F = 24.87) indicated the presence of significant differences between the groups (P =.0001). In general, the shear bond strengths were significantly greater in the 2 groups etched with 37% phosphoric acid. This was true for both the resin-reinforced glass ionomer (X = 6.1 +/- 2.7 MPa) and the composite (X = 5.2 +/- 2.9 MPa) adhesives. On the other hand, the shear bond strengths were significantly lower in the two groups conditioned with polyacrylic acid. The bond strength of the resin-reinforced glass ionomer adhesive conditioned with 10% polyacrylic acid (X = 0.4 +/- 1.0 MPa) was significantly lower than the group conditioned with 20% polyacrylic acid (&xmacr; = 3.3 +/- 2.6 MPa). The present findings indicated that the bond strength of the resin-reinforced glass ionomer adhesive can be significantly increased in the initial half hour after bonding if the enamel is etched with 37% phosphoric acid instead of being conditioned with either 10% or 20% polyacrylic acid. The clinician needs to take these properties into consideration when ligating the initial archwires.

Acid Etching, Dental↗
PubMed2002

The effect of two polishing pastes on the surface roughness of bis-acryl composite and methacrylate-based resins.

STATEMENT OF PROBLEM: A highly polished restoration surface is necessary to promote a plaque-free environment. PURPOSE: The purpose of this study was to compare the surface roughness of 3 different bis-acryl composite-based and 3 different methyl methacrylate-based provisional crown and fixed partial denture resins after being polished with aluminum oxide and diamond paste. MATERIAL AND METHODS: Six different materials were used (Iso-Temp, Protemp II, Structer 2, Dentalon Plus, Tab 2000 Kerr, Temdent). A total of 180 specimens were fabricated: 30 specimens of each material using circular stainless steel molds 10 mm in diameter and 2 mm high. Each material was mixed and polymerized according to manufacturer's instructions. The bis-acryl composite specimens were polymerized with a laboratory light-initiating unit for 30 seconds on each side (400 to 525 nm, 75 W quartz-halogen light source). All specimens were kept in a water bath at 37 degrees C for 45 minutes. Ten specimens of each group were left as untreated controls, 10 specimens of each group were polished with the aluminum oxide paste (Composite Polish), and 10 specimens of each group were polished with the diamond paste (Insta glaze). Surface roughness was determined with a profilometer. The data were analyzed with one-way analysis of variance (Post Hoc Scheffe's S test) (P<.001). In addition, the profilometric evaluations photographic images were recorded with a scanning electron microscope to examine the surface roughness after polishing. RESULTS: The mean of the surface characteristics of the bis-acryl composites were 1.33 microm for aluminum oxide and 0.90 microm for diamond polishing paste; the mean of the results of the methyl methacrylate resins were 1 microm for aluminum oxide and 0.50 microm for diamond polishing paste. The difference between the mean values of bis-acryl resins groups and methacrylate-based resin groups were significant (P<.001). The difference between the subgroups of bis-acryl resins group (Iso-Temp, Protemp II, Structer 2) were not significant (P>.05). The difference between the subgroups of methacrylate-based resin group (Dentalon, Tab 2000, Temdent) were not significant (P>.05). CONCLUSION: Within the limitations of this study, single-phase polishing of the bis-acryl composites tested and the methacrylate resins tested with diamond-based paste produced a smoother surface than when polished with aluminum oxide paste.

Acrylic Resins↗
PubMed2003

In vitro evaluation of long-term bonding of Procera AllCeram alumina restorations with a modified resin luting agent.

STATEMENT OF PROBLEM: Bonded densely sintered aluminum oxide ceramic restorations such as Procera AllCeram laminates rely on a strong and long-term durable resin bond. Air particle abrasion and a phosphate-modified resin luting agent have the potential to provide such bonds to aluminum oxide ceramics, but their efficacy on the Procera AllCeram intaglio surface is unknown. The inherent microroughness of this surface may influence bond strengths, because micromechanical interlocking is a main contributor for adhesion of resins to ceramic materials. PURPOSE: This study evaluated the bond strength of a phosphate-modified resin luting agent with and without silanization to an air particle-abraded Procera AllCeram intaglio surface compared with a conventional resin-bonding system before and after artificial aging. MATERIAL AND METHODS: Sixty square (10 x 10 x 2 mm) specimens of Procera AllCeram alumina ceramic with the Procera intaglio surface were air particle abraded with aluminum oxide. Composite cylinders (2.9 mm in diameter and 3.0 mm in width) were fabricated with Z-250 composite and bonded to the ceramic specimens with either Panavia 21 TC or Rely X ARC (control) and their corresponding bonding/silane coupling agents. In addition, Panavia was used without silanization as suggested in similar studies. Subgroups of 10 specimens were stored in distilled water for either 3 or 180 days before shear bond strength was tested with a universal testing machine (MPa) until fracture. The 180-day specimens were subjected to thermocycling at 2000 cycles every 30 days (12,000 cycles total). Data were analyzed with 1-way analysis of variance and Tukey's multiple comparison (alpha=.05). Failure modes were examined with a light microscope (original magnification x 25). RESULTS: Differences between short-term and long-term groups were highly significant (P=.000). Bond strength with Rely X ARC and its silane coupling agent (22.75 +/- 4 MPa) decreased significantly (P=.000) after artificial aging (3.32 +/- 3.62 MPa). Panavia 21 after silanization revealed significantly different (P=.003) early (21.42 +/- 4.3 MPa) and late (16.09 +/- 2.37 MPa) bond strengths but achieved the highest bond strength after artificial aging. Bond strengths of Panavia without silanization both early (8.06 +/- 2.1 MPa) and late (6.91 +/- 2.49 MPa) were not significantly different. Failure modes were mainly adhesive at the ceramic surface for all groups. CONCLUSION: Panavia 21 in combination with its corresponding bonding/silane coupling agent can achieve an acceptable resin bond to the air particle-abraded intaglio surface of Procera AllCeram restorations after artificial aging, which had mixed effects on the other investigated groups. The conventional resin luting agent revealed the most dramatic decrease in bond strength.

Adhesiveness↗
PubMed2001

A resin veneer for enamel protection during orthodontic treatment.

The aims of this study were to test the tensile bond strength of a recently developed veneer. Sound premolar teeth (120) extracted for orthodontic purposes were divided into two experimental and two control groups. In one experimental group (V1) 4-META/MMA-TBB resin (4META) was used on the surface veneer prepared with micro particle filled resin (MFR) as an adhesive for bracketing and in the second group (V2) 4META was applied on the surface veneer with the trial resin. For the controls, in group R 4META was used on the enamel surface without veneer and in group G light-cured glass ionomer cement was applied. The 30 samples in each group were divided into three groups of 10 samples and thermal cycled (TC) at 3000, 10,000 or left uncycled. Tensile testing was carried out using an Instron machine. After tensile testing the bond failures in the experimental groups were recorded using a stereomicroscope. Statistical analysis was performed using ANOVA. In group V2 the resin veneer was able to maintain sufficient bond force to enamel during clinical use. The bond strength of group V1 was significantly higher than that of groups R (P < 0.05) and G (P < 0.01) at TC 0, but for both TC 3000 and 10,000, the bond strength of group V1 was lower than groups R and G, respectively. There were significant differences between groups V1 and R (P < 0.01) for TC 3000, and between groups V1 and R and G (P < 0.01) at TC 10,000. The bond strength of group V2 was almost equal to that of group R at TC 0. At TC 3000, group V2 showed significantly lower bond strength than group R (P < 0.05), but no significant difference was found compared with group G. At TC 10,000, there were no significant differences between groups V2, R or G. When comparing groups V1 and V2, the bond strength of group V1 was significantly higher than that of group V2 (P < 0.01) at TC 0, but the bond strength of group V1 was significantly lower than that of group V2 for both TC 3000 (P < 0.05) and TC 10,000 (P < 0.01). Comparison between groups R and G, showed that the bond strength of group R was significantly higher than that of group G for both TC 0 (P < 0.01) and TC 3000 (P < 0.01), but no significant difference was found for TC 10,000. In group V2, nine samples showed adhesive failure between the veneer surface and bracket adhesive before thermal cycling. There were significant differences between the MFR and both trial resin and glass ionomer cement (P < 0.01) when examining thermal expansion. No significant difference was found between the trial resin and glass ionomer cement. It is suggested that application of a resin veneer prior to bracket bonding is suitable for clinical application to protect the teeth and to prevent decalcification and caries.

Acrylic Resins↗
PubMed1994

Effect of restoration composition, shade, and thickness on the cure of a photoactivated resin cement.

PURPOSE: This study investigates the effect of selected properties of a restorative material (type, shade, and thickness) on the cure of a photoactivated resin cement. MATERIALS AND METHODS: Disks of ceramic and resin-based restorative materials of two extreme shades were made to provide thicknesses of 0.5 to 3.0 mm in 0.5-mm intervals. Light transmission was measured through various thicknesses and shades of each restorative material type. The effect of light transmission, as influenced by restorative material type, shade, and thickness on resin cement cure was also determined. RESULTS: Thickness and shade of restorative material had the greatest influence on light transmission. For simulated restoration thicknesses 1.5 mm and greater, Dicor (Dentsply International Inc, York, PA) had greater transmission of light than the other materials, regardless of shade. At equal restorative material thickness, light transmission was similar for identical shades of the other three materials. Restoration shade and thickness also had the greatest influence on resin cement cure. Material type, although significant, had only a minor influence. At thicknesses of 1 to 2 mm, Dicor consistently yielded greater resin cement cure values than any other material tested. CONCLUSIONS: When considering the ability of restorative materials to transmit light for curing of photo-activated resin cements, the thickness of the restoration and its shade are much more influential than the choice of restorative material. Dicor provides greater light transmission that results in the ability to photobond restorations of greater thicknesses than the other materials. For restorations greater than 1 mm in thickness, a dual cure or chemical cure resin cement should be used to provide maximal cement properties.

Analysis of Variance↗
PubMed2005

Shear bond strength evaluation of composite resin on enamel and dentin after nonvital bleaching.

BACKGROUND: Studies have shown that bleaching agents interfere with the adhesion of composite resin placed immediately after bleaching. PURPOSE: The aim of this study was to evaluate the shear bond strengths of composite resin after four different durations since the time of nonvital bleaching (1 d and 1, 2, and 3 wk). MATERIALS AND METHODS: Two hundred seventy bovine teeth were assigned to nine groups (n = 30) according to the bleach used and the time between bleaching and restoration: group 1--sodium perborate (SP), 1 day after bleaching (AB); group 2--SP, 1 week AB; group 3--SP, 2 weeks AB; group 4--SP, 3 weeks AB; group 5--37% carbamide peroxide (CP), 1 day AB; group 6--CP, 1 week AB; group 7--CP, 2 weeks AB; group 8--CP, 3 weeks AB; group 9--control group (no treatment). After the bleaching treatment, the teeth in each group were sectioned and the enamel and dentin were separated. The teeth were cut, embedded in polyester resin, and polished to obtain flat enamel and dentin surfaces. The adhesive system was applied and a cylinder of composite resin was bonded on each flat surface. The specimens were stored in distilled water for 7 days at 37 degrees C. The shear bond strength test was performed in a universal test machine (Emic DL-500, São José dos Pinhais, São Paulo, Brazil) at a crosshead speed of 0.5 mm/min. RESULTS: The data were subjected to analysis of variance, Dunnett's t-test, and Tukey's least significant difference at p < or = .05 and showed a statistically significant decrease in bond strengths of composite resin for enamel and dentin 1 day after the nonvital bleaching. CLINICAL SIGNIFICANCE: The decrease in shear bond strength values is time dependent. A delay in bonding procedures for composite resin restoration is recommended. According to the results, a satisfactory time to perform the restoration of composite resin for both enamel and dentin is 2 weeks after bleaching.

Analysis of Variance↗