Effect of Tooth-Whitening Procedures on Stained Composite Resins.

In this laboratory study, a composite resin was stained to a visibly discernible level using both coffee and red wine over 14 days (change was considered clinically noticeable and significant when ΔEab*≥2.7). Color change was measured at one, three, seven, and 14 days of staining. Although the nature of color change was different for the two staining solutions, the overall degree of staining (ΔEab*) rendered by either coffee or wine at each time interval was not significantly different ( p≥0.05). Four whitening protocols were applied to stained composites. Treatment included applications of distilled water (control), Crest Pro-Health [HD] toothpaste, Crest Whitestrips, Opalescence PF bleach (15%), and application of a fine pumice polishing (Preppies). HD toothpaste and Whitestrips were applied daily for 21 days, Opalescence was applied daily for 10 days, and polishing was applied once. Each of the whitening products, applied in a manner simulating at-home or in-office treatment, was effective in producing color improvements (lightening) over controls ( p<0.05), but none of the four treatments produced lightening that was significantly different from the other treatments ( p≥0.05). A comparison of final composite color with that measured at baseline showed that Opalescence returned composite color to an acceptable level following exposure to both staining solutions (ΔEab*<2.7), Whitestrips returned color close to baseline for wine-stained composites, and HD paste and polishing permitted residual stain to remain (ΔEab*≥2.7).

Effect of liners on cusp deflection and gap formation in composite restorations.

This study measured deformation of cusps and gap formation associated with MOD resin composite restorations in maxillary premolars with and without the use of low elastic modulus liners. Low elastic modulus liners may reduce the deformation by absorbing polymerization shrinkage stress. Forty maxillary premolars were mounted in stone and slot MOD cavities were prepared. Teeth were randomized into four groups. In Group A, cavities were etched, Single Bond was applied and the cavities were restored with Z-100 composite. In Group B, the same was done except that a layer of flowable composite (Revolution) was place and cured after the bonding agent. In Group C, the same steps were followed as Group A but a layer of glass ionomer (Vitrebond) was placed and cured before the bonding agent. In Group D, a thin layer of composite was placed (after the bonding agent) as a base and cured and the cavities were filled. The distance between indexed cusp tips was measured before the restorations were finished and five minutes and 24 hours after the restorations were completed. The samples were then sectioned mesiodistally and epoxy resin replicas were made and prepared for SEM evaluation of gap formation. The mean contraction of the cusps in microm at 5 minutes and 24 hours, respectively, for each group was A) 47 and 30, B) 35 and 21, C) 23 and 8 and D) 40 and 28. Groups A and D resulted in the highest deformation, B was intermediate and C was the lowest. There was no statistically significant difference in gap formation between the groups.

Effect of dentin desensitizers and dentin bonding agents on dentin permeability.

PURPOSE: To determine the effect of dentin desensitizing agents (oxalates and glutaraldehyde) and dentin bonding agents, with and without resin-based composite (RBC) on dentin permeability and morphology of the dentin surface. The influence of saliva and toothbrushing on these agents was also evaluated. MATERIALS AND METHODS: Radicular dentin discs +/-1 mm thick were obtained from extracted human teeth. The thickness of the discs was standardized by grinding them with 600 grit silicon carbide powder. Both pulpal and periodontal surfaces of the discs were treated with 6% citric acid for 2 min prior to the baseline measurement of dentin permeability. Permeability was measured for the discs, using a split-chamber apparatus, at four different time points: at baseline, after treatment with each desensitizing modality, after 24 hrs of saliva immersion and after simulated toothbrushing equivalent to 3 weeks of normal brushing. The treatment modalities were: Sensodyne Dentin Desensitizer, Gluma Dentin Desensitizer, All-Bond DS (primers without etching), Etch+Primers (All-Bond 2 system), Etch+Primers+Adhesive and Etch+Primers+Adhesive+RBC (AElite Flo). Radicular dentin discs were prepared separately for scanning electron microscopy (SEM). One group was left untreated as the control group. Discs in the other groups were treated with the modalities listed above. One disc from each group was viewed under the SEM after treatment with the desensitizing modality. The second disc in each group was viewed after 24 hrs of saliva immersion following desensitizing treatment and the third disc after 3 weeks of simulated toothbrushing following desensitizing treatment and saliva immersion. RESULTS: The greatest reduction in permeability was caused by All-Bond DS followed by Sensodyne Dentin Desensitizer and Etch+Primers+Adhesive+RBC. Gluma Dentin Desensitizer, Etch+Primers, and Etch+Primers+Adhesive did not reduce permeability by a significant amount. Saliva immersion increased permeability significantly only for the Gluma and Etch+Primers+Adhesive groups. There was a trend towards increase in permeability after toothbrushing; however, this increase was not statistically significant for any group (P > 0.05). Thus, placement of primers without etching (All-Bond DS) reduced permeability more than any other treatment modality. These data indicate that etching a sensitive dentin area may be appropriate only if RBC is to be placed in the area. Exposure to saliva and toothbrushing countered the decrease in permeability caused by dedicated desensitizers and dentin bonding agents. The SEM micrographs revealed that in most cases, form corroborated function and the morphology of the dentin surface corresponded to the dentin permeability values.

Effect of HEMA-containing dentin desensitizers on shear bond strength of a resin cement.

PURPOSE: To determine whether the use of two HEMA-containing dentin desensitizing agents [Health-Dent Desensitizer with fluoride (H) or Gluma Desensitizer (G)], when applied at simulated "cavity preparation" and "cementation" appointments, affects the bond strength of lab processed resin composite restorations cemented to dentin. MATERIALS AND METHODS: The occlusal surfaces of 70 teeth were ground flat to expose dentin and polished to 600 grit. Teeth were randomly assigned to seven groups (n = 10). The treatments were applied in two sessions in order to simulate cavity preparation and cementation appointments. Water (W) was applied as a control instead of a desensitizing agent. H or G were applied for 30 seconds with a rubbing motion (1) at preparation appointment (HW and GW), or (2) at cementation appointment, after etching (WH and WG), or (3) at both sessions (HH and GG). In the control group, water was applied at both sessions (WW). All-Bond 2 and Dual Cement were used according to manufacturers' instructions to cement pre-polymerized resin composite cylinders (4 mm diameter) to the dentin surfaces using a force of 1.0 MPa. Specimens were thermocycled 300x and tested in shear until failure. Data was analyzed using one-way ANOVA and Tukey's HSD test at alpha = 0.05. RESULTS: Mean bond strength and standard deviations are reported in MPa: GW = 7.4 +/- 6.0; WW = 7.7 +/- 5.8; HW = 8.2 +/- 4.3; WH = 10.8 +/- 6.2; GG = 13.5 +/- 6.0; HH = 13.8 +/- 7.1; WG = 19.9 +/- 8.8. There were no significant differences in bond strengths for GW, WW, HW, WH and GG. Shear bond strength for WG and HH was significantly higher than all groups except for GG. Results of this in vitro study indicate that the use of desensitizers at the preparation and/or cementation appointment does not interfere with bond strengths of resin cement to dentin.

Shear bond strengths of 10 adhesive resin/amalgam combinations.

This study compared the shear bond strengths of amalgam to dentin using two amalgam alloys and five adhesive resin systems. One hundred extracted human third molars were flattened occlusally to expose dentin. Dentin surfaces were treated with one of five adhesive resins: All-Bond 2, Amalgambond Plus, Amalgambond Plus with HPA Powder, OptiBond, and Resinomer. Tytin (spherical) or Dispersalloy (admixed) amalgam was condensed onto the treated dentin surface through a Teflon split mold. The samples were stored 7-10 days and thermocycled before shear testing using a Zwick Materials Testing Machine. Two-way ANOVA revealed significant differences among the 10 groups (P < 0.05). The combination of Tytin/OptiBond produced the highest bond strength to dentin (14.17 MPa), while Dispersalloy/Amalgambond Plus produced the lowest (3.89 MPa). In general, the filled resin systems (Amalgambond Plus with HPA Powder, OptiBond, Resinomer) produced higher bond strengths than the unfilled systems (All-Bond 2, Amalgambond Plus). Additionally, for four of the five resins, bond strengths were higher with Tytin than with Dispersalloy, although differences were statistically significant in only two groups.

Surface treatment effects on amalgam repair strength.

PURPOSE: To determine whether the use of microetching and bonding agents could improve the shear bond strength between aged and freshly added dental amalgam, simulating an amalgam repair. MATERIALS AND METHODS: Aged amalgam surfaces were treated with either a carbide bur or carbide bur + microetcher (Al2O3 abrasive). Five commercially-available adhesive systems were tested. Fresh amalgam was condensed through a split mold onto each prepared amalgam surface. Two control groups were included: a positive control consisting of non-repaired amalgam, and a negative control consisting of aged specimens which received neither carbide bur nor microetching preparation prior to the addition of fresh amalgam. In addition, one group received only carbide bur and another received only carbide bur and microetching treatments, without any adhesive. Following storage and thermocycling, each specimen was tested for shear bond strength. RESULTS: The mean shear bond strength of the repaired samples treated with carbide bur alone (25.8 MPa) was not exceeded by any of the other treatments. Neither microetching nor use of an adhesive agent significantly improved amalgam-to-amalgam shear bond strength. In some cases, use of an adhesive agent significantly decreased the shear bond strength of repaired amalgam samples.

Surface treatment techniques for resin composite repair.

PURPOSE: To compare bond strengths of fresh resin composites to previously polymerized ("aged") composites following various surface treatments. MATERIALS AND METHODS: Eighty Pertac Hybrid (PH) and an equal number of Silux Plux (SLX) specimens were fabricated and stored for 1 week prior to surface treatment. The specimens were then polished and stored for an additional 24 hours prior to final surface treatment. The surface treatments included use of one of the following: (1) diamond bur (DB), (2) microetcher with 50 microns Al2O3@80 psi pressure (ME), (3) high-pressure air abrasion with 27 microns Al2O3@psi, (KCP), or (4) low-pressure silicate ceramic deposition using 30 microns particles@34 psi (CJ-S) with a microetcher. Half of the samples were treated with a silanating agent. Fresh resin composite (same type as used for the aged specimen) was bonded to the treated surfaces, and specimens were then stored 24 h and thermocycled 300 x at 5 degrees and 55 degrees C prior to testing for shear bond strength. Two-way ANOVA was used to determine significant differences between mean shear bond strengths for both composite materials. RESULTS: Significant differences were found between the groups for both surface treatment and silane use (P < 0.05). The interaction between the two main effects was also significant (P < 0.05). Overall, the highest bond strengths were found when the low-pressure silicate ceramic deposition system (CJ-S) was used, with or without silane.

Enhancement of resin bonding to heat-cured composite resin.

The purpose of this study was to evaluate the effectiveness of various surface treatments used to enhance the bond strength of resin cements to two different laboratory-processed composite resins. Seventy specimens of a microfilled composite resin (Concept) and 70 specimens of a micro-hybrid composite resin (Herculite XRV) were fabricated in metal wells and subjected to heat (250 degrees F) and pressure (85 psi) curing. An additional 70 specimens of each material were fabricated in the shape of disks and also subjected to the same heat/pressure curing. All composite resins were subjected to one of seven treatment regimens. The like-treated specimens were then bonded together using dual-curing resin cement and a uniform seating force (106 gm). After 7 days, bonded specimens were thermocycled 1000 times at 5 and 55 degrees C, and debond shear strengths were determined on a Universal Testing Machine. The use of microabrasion (50 microns aluminum oxide at 60 psi) and ceramic layer deposition (30 microns aluminum oxide with a ceramic additive at 75 psi) consistently improved the shear bond strength of the resin cements to both composite resins. The other treatment combinations provided varying effects. In conclusion, microabrasion or ceramic layer deposition are preferred methods to enhance the bond of resin cements to composite resins.

Effect of Gluma desensitization on dentin bond strength.

PURPOSE: To determine whether the use of Gluma as a desensitizing agent on tooth preparations has any effect upon the bond strength of a resin composite restoration cemented to dentin. MATERIALS AND METHODS: Forty extracted human molars which were caries and restoration-free were occlusally reduced to remove enamel. Twenty of the teeth received a Gluma desensitization treatment and 20 were untreated (controls). Following a 7-day storage period, simulated resin composite inlays were bonded to all of the dentin specimens, using either All-Bond 2 with All-Bond Crown & Bridge Cement or OptiBond with Porcelite Dual Cure. Twenty-four hours later, the shear bond strength of the specimens was determined. RESULTS: Statistical analysis (paired t-tests) indicated no significant difference in bond strength for Gluma-treated specimens when compared to controls, for either bonding material.

Effects of secondary curing on indirect posterior composite resins.

This study was designed to compare strength, elastic modulus (stiffness), and hardness for five composite resin materials that are used for laboratory-fabricated posterior composite restorations. Ten specimens of each material were processed according to the manufacturer's instructions. Statistical analysis indicated that there were significant differences in mechanical properties among the materials tested. In addition, materials that are incrementally light cured prior to secondary processing were tested for changes in mechanical properties following secondary processing. It was determined that secondary processing provided improvement in flexural strength (11%) when compared to samples that were only light cured.

Bond strength and microleakage of current dentin adhesives.

OBJECTIVES: The purpose of this in vitro study was to evaluate shear bond strengths and microleakage of seven current-generation dentin adhesive systems. METHODS: Standard box-type Class V cavity preparations were made at the cemento-enamel junction on the buccal surfaces of eighty extracted human molars. These preparations were restored using a microfill composite following application of either All-Bond 2 (Bisco), Clearfil Liner Bond (Kuraray), Gluma 2000 (Miles), Imperva Bond (Shofu), OptiBond (Kerr), Prisma Universal Bond 3 (Caulk), Scotchbond Multi-Purpose (3M), or Scotchbond Dual-Cure (3M) (control). Lingual dentin of these same teeth was exposed and polished to 600-grit. Adhesives were applied and composite was bonded to the dentin using a gelatin capsule technique. Specimens were thermocycled 500 times. Shear bond strengths were determined using a universal testing machine, and microleakage was evaluated using a standard silver nitrate staining technique. RESULTS: Clearfill Liner Bond and OptiBond, adhesive systems that include low-viscosity, low-modulus intermediate resins, had the highest shear bond strengths (13.3 +/- 2.3 MPa and 12.9 +/- 1.5 MPa, respectively). Along with Prisma Universal Bond 3, they also had the least microleakage at dentin margins of Class V restorations. SIGNIFICANCE: No statistically significant correlation between shear bond strength and microleakage was observed in this study. Adhesive systems that include a low-viscosity intermediate resin produced the high bond strengths and low microleakage. Similarly, two materials with bond strengths in the intermediate range had significantly increased microleakage, and one material with a bond strength in the low end of the spectrum exhibited microleakage that was statistically greater. Thus, despite the lack of statistical correlation, there were observable trends.

A clinical study of nightguard vital bleaching.

This double-blind, randomized, controlled clinical trial was designed to evaluate the efficacy and soft tissue effects of nightguard (mouthguard) vital bleaching. Subjects were assigned to one of two treatment groups, overnight (insertion of mouthguard at bedtime) or 3-hour (replenishment of test solution at hourly intervals for a total of 3 hours exposure daily). The experimental solutions included two products that are specifically designed for tooth bleaching, one product that is marketed as an oral antiseptic, and a control solution (glycerin). Each subject participated for a 3-week period. Tooth color analysis (shade determination) was done at baseline and the end of the treatment. Gingival and Plaque Indices were recorded at baseline and at the end of each week of study. Results indicated that the bleaching treatment was effective in most cases and caused no tissue inflammation or significant tooth sensitivity. The mean Gingival and Plaque Indices were generally lower (denoting improvement) at the end of treatment. Patient satisfaction with the procedure was high.

A national survey on the use of glass-ionomer cements.

This study was conducted to determine why and how glass-ionomer cements are being used by general dentists. Data were collected by a mail survey sent to a random sample of approximately 1000 general dentists in the United States. The results showed that 94% of the respondents currently use or have used glass ionomers. The primary uses (in order of popularity) are: 1) as a base or liner, 2) as a luting cement, and 3) as a crown foundation. Eighty-two percent of the respondents who use glass-ionomer luting cements reported some postoperative tooth sensitivity, but a slightly larger proportion (85%) reported postoperative sensitivity with other cements.

Side-effects: mercury contribution to body burden from dental amalgam.

The purpose of this paper is to examine and report on studies that relate mercury levels in human tissues to the presence of dental amalgams, giving special attention to autopsy studies. Until recently, there have been few published studies examining the relationship between dental amalgams and tissue mercury levels. Improved and highly sensitive tissue analysis techniques have made it possible to measure elements in the concentration range of parts per billion. The fact that mercury can be absorbed and reach toxic levels in human tissues makes any and all exposure to that element of scientific interest. Dental amalgams have long been believed to be of little significance as contributors to the overall body burden of mercury, because the elemental form of mercury is rapidly consumed in the setting reaction of the restoration. Studies showing measurable elemental mercury vapor release from dental amalgams have raised renewed concern about amalgam safety. Mercury vapor absorption occurs through the lungs, with about 80% of the inhaled vapor being absorbed by the lungs and rapidly entering the bloodstream. Following distribution by blood circulation, mercury can enter and remain in certain tissues for longer periods of time, since the half-life of excretion is prolonged. Two of the primary target organs of concern are the central nervous system and kidneys.

Composite resin esthetic dentistry survey in New England.

This study collected information on various aspects of esthetic dentistry, including the time used and income produced while delivering treatment to noncarious teeth. A mail survey was sent to 521 randomly selected dentists in the six-state New England area (approximately 7% of the total active dentists in that region); the response rate was 74%. The results indicated that dentists are providing a substantial amount of esthetic treatment on noncarious teeth.

Effect of retention grooves on fracture strength of Class 2 composite resin and amalgam restorations.

The effect of approximal retention grooves on fracture strengths of class 2 composite resin and amalgam restorations was tested in vitro. Results indicated that retention grooves significantly improved (P less than 0.05) the compressive strength of amalgam restorations (38.6% stronger). For posterior composite resin restorations, there was no significant difference in mean compressive strength of restorations in preparations with and without retention grooves.

The need for operative dentistry services: projecting the effects of changing disease patterns.

The declining incidence of caries in children and adolescents has caused speculation that there will soon be a great reduction in need for restorative services among adults. This study used recent dental epidemiological data, population estimates, and numerous alternative assumptions to calculate the hours of adult operative dentistry treatment need in the US in 1972, 1990, and 2030. According to those calculations, the total hours of need were about 125 million in 1972. In 1990 and 2030, the projected hours of need were determined to be about 150 million and 192 million, respectively.