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Abstract Background The clinical success rate with zinc phosphate cemented Procera crowns is high. The objective with this study was to determine whether CADCAM processed and zinc phosphate cemented Denzir copings would perform as well as zinc phosphate cemented Procera copings when tested in vitro in tension. Methods Twelve Procera copings and twenty-four Denzir copings were made. After the copings had been made, twelve of the Denzir copings were sandblasted on their internal surfaces. All copings were then cemented with zinc phosphate cement to carbon steel dies and transferred to water or artificial saliva. Two weeks after cementation, half of the samples were tested. The remaining samples were tested after one year in the storage medium. All tests were done in tension and evaluated with an ANOVA. Results Sandblasted and un-sandblasted Denzir copings performed as well as Procera copings. Storage in water or artificial saliva up to one year did not decrease the force needed to dislodge any of the coping groups. Three copings fractured during testing and one coping developed a crack during testing. The three complete fractures occurred in Procera copings, while the partly cracked coping was a Denzir coping. Conclusion No significant differences existed between the different material groups, and the retentive force increased rather than decreased with time. Fewer fractures occurred in Denzir copings, explained by the higher fracture toughness of the Denzir material. Based on good clinical results with zinc phosphate cemented Procera crowns, we foresee that zinc phosphate cement luted Denzir copings are likely to perform well clinically.

This article describes how dental adhesives evolved from the cements developed by the Mayan Indians into today's modern dental adhesives. Particular attention is paid to Oskar Hagger, a chemist who worked for DeTrey/Amalgamated Dental Company, and already in 1949 developed an adhesive product called Sevriton Cavity Seal. That adhesive was acidic and interacted with the tooth surface on a molecular level. His ground-breaking concept makes him the true "Father of Modern Dental Adhesives." Hagger's concept was soon adopted by other investigators, and different generations of dental adhesives evolved thereafter. Today, after many years of accepting that the key to the success of dental adhesives is the micromechanical retention resulting from acid etching of dentin and enamel, we still return to Dr. Hagger's original concept that bonding can be achieved via molecular interactions between adhesives and tooth surfaces. That concept is obvious in the development of newer generations of dentin adhesives. These adhesives, like Sevriton Cavity Seal, rely on acidic monomers capable of etching and interacting on a molecular level with tooth surfaces in order to form physical/chemical bonds between the restoration and the tooth. Whether Hagger's concept will become the norm in the future is still an open question, but one thing is certain: Hagger's idea is still very much alive. [ABSTRACT FROM AUTHOR]

Purpose: To test the hypothesis that simpler-to-use dentin adhesives (7th-generation adhesives) perform better when used by inexperienced operators than do the more complex 4th-generation adhesives. Materials and Methods: Six operators with no previous experience regarding dental adhesives, three residents in pediatric dentistry, and three experienced dentists used one 4th-generation dentin adhesive (MA) and two 7th-generation adhesives (MB and MC). With each adhesive, each operator performed 6 bondings to enamel and 6 bondings to dentin. After 24 h of storage in water at 37°C, the shear bond strength was determined. Results: The pooled results showed that the bond strength to dentin was higher (p < 0.05) than that to enamel (dentin mean value = 14.0 MPa, SD = 9.1 MPa; enamel mean value = 11.9 MPa, SD = 7.1 MPa), and that adhesive MA performed better (p < 0.05) than adhesives MB and MC (inexperienced operators = 16.2 ± 10.9 MPa, residents in pedodontics = 12.0 ± 6.8 MPa, and experienced operators = 10.7 ± 4.8 MPa). Of the two 7th-generation adhesives, one performed better on enamel than on dentin, while the other 7th-generation adhesive performed better on dentin than on enamel. Regarding operators, there were large individual variations. The inexperienced bonders performed as well as the residents (p > 0.05), while the experienced operators performed best (p < 0.05). Conclusion: In general, the tested 4th-generation adhesive performed better than the 7th-generation adhesives. Even inexperienced operators performed better with the more difficult-to-use 4th-generation adhesives than with the 7th-generation adhesives. Dentin adhesion was stronger than enamel adhesion. [ABSTRACT FROM AUTHOR]

Three UEDMA/TEGDMA (50:50 by weight) based dental composites were made, each with filler loadings of 53 vol.%. The three composites contained silane-treated filler particles with average particle diameters of 1.5, 3.0, or 10.0 microm. Twelve specimens per composite were mounted on wear wheels and run through 200,000 cycles in an ACTA wear machine. Six of these specimens per material were worn in slurries consisting of 30 g ground Millet seed shells and 120 g ground rice mixed with 275 mL water. The remaining six specimens were worn in similar 25% ethanol-water slurries. The composite wear profiles were recorded with a profilometer and used to calculate the wear. Hardness values of the composites were also measured both before and after storage for 2 weeks in either water or in a 25% ethanol water solution. The wear and hardness values from the measurements were analyzed using ANOVA. The wear analysis showed that the finer composites (1.5 microm filler diameter) wore the least and the coarsest composites (10 microm filler diameter) the most. The wear was significantly higher in the ethanol water slurry than in the water slurry. The hardness value of the coarsest composite decreased more than the finest composite during storage in water or 25% ethanol water. The hardness decrease was most pronounced in the alcohol solution. [ABSTRACT FROM AUTHOR]

The author reflects on the need for the dental community to gain a better understanding of the fracture mechanics behind dental bond failures in restorations. He comments on the book "Adhesion and Adhesives: Science and Technology" by A. J. Kinlock, which suggested mechanical tests cannot measure the level of adhesion forces that operate across an interface. He mentions bulk strength values often are magnitudes lower than the material's theoretical material strength caused by processing defects.

Purpose: To (1) measure the shear and flexural bond strengths of three different bonding agents that use different application techniques, (2) determine whether the shear and flexural bond tests rank the three materials similarly, and (3) determine whether the fractured surface produced with the flexural test, facilitates studies of failures within the adhesive interphase region. Materials and Methods: Scotchbond MP (SBMP), Single Bond (SNGB) and Clearfil SE (CLSE) were evaluated. For each material, 16 samples were bonded. Eight of these samples were bonded for shear testing and the other 8 samples for flexural bond strength testing. After the bonding was completed, all samples were stored in water at 37°C for 30 days. Shear bond strength was measured using an orthodontic edge wire loop and flexural strength was measured using a 4-point bending device. The samples used for the flexural test consisted of 3 mm x 3 mm x 20 mm beams in which center a 1 mm thick dentin wafer had been bonded perpendicularly to the length of the beam. An indentation with a microhardness tester was placed at one of the dentin-composite interfaces to serve as an induced flaw. This flaw was placed on the surface in tension during flexural testing. The data were analyzed using ANOVA. Scanning electron microscopy was used to examine each specimen and assign its failure mode. Percent occurrence of failure mode was determined for each material and overall for both test methods. When there was uncertainty regarding failure location, electron dispersive spectroscopy x-ray analysis was used to identify elements present on the fractured surface. Results: No significant difference {P> 0.05) in bond strength was observed within each test group, while significant differences (P< 0.05) existed between the two test methods (shear; SBMP= 21.2 ± 4.0 MPa, SNGB= 24.3 ± 4.7 MPa, CLSE= 24.6 ± 4.4 MPa; flexural strength: SBMP= 34.6 ± 9.3 MPa, SNGB = 31,9 ± 6.9 MPa. CLSE= 34.3 ± 4.7 MPa). Shear bond test specimens failed mostly within dentin (54.2%), followed by failures within the adhesive interphase (41.6%), and failures in composite (4.2%). Flexural strength specimens failed mostly within the adhesive interphase (833%), followed by failure in composite (16.7%). Bond strengths were similar for all three adhesive systems within each test method group. Failure mode analysis revealed significant differences (P< 0.0001) among the two test methods. [ABSTRACT FROM AUTHOR]

PURPOSE: To evaluate the shear bond strength of acetone- or water-based primers applied with or without agitation to either wet or dry dentin. MATERIALS AND METHODS: Forty-eight caries-free extracted human premolars were embedded in gypsum and flat dentin surfaces were prepared. The teeth were randomly divided in eight groups with six specimens each. After acid etching and rinsing, either a HEMA and acetone (Ac) or a HEMA and water (Wa) primer were applied to dry (D) or wet (W) dentin. The primer was placed with (Y) or without (N) agitation according to the following combinations: Group 1: D-Ac-Y; Group 2: D-Ac-N; Group 3: D-Wa-Y; Group 4: D-Wa-N; Group 5: W-Ac-Y; Group 6: W-Ac-N; Group 7: W-Wa-Y; Group 8: W-Wa-N. The primed surface was dried, covered with a bonding resin and light-cured, whereupon a composite cylinder was bonded to the dentin surface. The shear bond strength was determined after 30 days in water. RESULTS: The mean and standard deviations, expressed in MPa, were: Group 1: 13.1 ± 3.42; Group 2: 15.9 ± 4.84; Group 3: 19.8 ± 6.64; Group 4: 18.6 ± 5.18; Group 5: 16.5 ± 5.25; Group 6: 25.5 ± 4.79; Group 7: 21.9 ± 4.94; Group 8: 17.4 ± 4.50. The results were analyzed using ANOVA and Waller-Duncans K-ratio t-test. The acetone-based primer gave the highest bond strength to wet dentin without agitation. When the acetone-based primer was used on dry dentin a significant decrease in bond strength occurred (P < 0.05). No significant difference (P > 0.05) was found for the water-based primer on wet or dry dentin. Agitation improved the bond strength for the water-based primer, but decreased the bond strength for the acetone-based primer. [ABSTRACT FROM AUTHOR]

Differences in the flexural strength of composites (P-30) repaired with four different adhesive techniques were determined and compared to the flexural strength of unrepaired specimens. Besides investigating the effects of differences in repair methods, both the effect of composite age at repair time and the effect of water storage on flexural strength were evaluated. No significant differences were found between specimens which had been stored for different times (1 or 60 days) before they were repaired. All specimens, including the unrepaired ones, became weaker with time in water. After both 90 and 360 days at 37°C in water, the strength of the repaired specimens ranged between 25 and 50% of the strength of the unrepaired specimens. The weakest group was the one which had been repaired after acid etching, water rinsing, and air drying only. [ABSTRACT FROM AUTHOR]

Six different dental composite materials were investigated regarding leaching of filler elements such as silicon, barium, and zinc. The leaching was conducted by storing the samples in distilled water at 60°C for half a year. The results could not prove that the leaching behavior of filler elements in most of the investigated cases decreases with time. The practical implications of this study could be important. If other elements follow the same leaching pattern, therapeutic elements such as fluoride could be incorporated in filler particles. The tendency of composites to Leach filler cements almost linearly with time, could be used to generate a constant release rate of such therapeutic elements over time. Such an application could have a major impact on controlling caries adjacent to composite restorations and sealants. [ABSTRACT FROM AUTHOR]

The objective with this study was to investigate how the shear bond strength of a phosphate based dentinal bonding agent is influenced by storage in saline at 37°C up to 6 months. The effect of dentin bonding agent on the leachability of calcium from dentin was also determined. The results showed that the shear bond strength decreased after saline storage. After half a year, the strength was ca. 60%, of the initial dry strength. The bonding agent also accelerated the leaching of calcium from the dentin discs, a finding which was explained as being a result of acidic reactions occurring at the dentin-bonding agent interface. In addition to the increased calcium leachability, the dentin bonding agent peeled off with time from the dentin discs. SEM investigation of the dentin surfaces after either shear strength determination or the film had peeled off due to water storage showed that a residual film was left on the dentin. This film, based on morphologic appearance, is most likely composed of the bonding agent but may also contain residuals of the smear layer. [ABSTRACT FROM AUTHOR]

Purpose: To evaluate the clinical performance of two self-etching adhesives of different pH values when used to restore non-retentive cervical lesions., Methods: 84 paired non-retentive class 5 restorations were originally placed in 21 subjects in need of 2, 4 or 6 restorations in incisors, canines and premolars. The retention of the placed restorations relied on the two adhesives only, which were iBOND NG plus B (iB), now marketed as iBOND Self Etch, and Clearfil SE (CB). Lesions were restored with a micro-hybrid composite (Venus). Following a baseline evaluation, the subjects were recalled and evaluated after 3 months, 1 year, 2 years and 4 years., Results: At the 4-year evaluation, 17 subjects remained who had originally received 66 restorations (33 of each adhesive). Eight of these 66 restorations had dropped out during the 4 years (4 iB and 4 CB) for different reasons. Two of the drop-outs (one iB and one CB) had fractured in the same patient, leaving a large piece of the composite still bonded to the dentin. Two other drop outs (both material iB) were not available for evaluation because they had been crowned (one after endodontic treatment and one after cusp fracture), while the remaining drop-out iB restoration had debonded. Regarding material CB, except for the fractured and partly retained drop-out restoration, the remaining three drop-outs had debonded. Pair-wise comparison of the evaluated parameters using Fishers Exact Test revealed no statistically significant (P < 0.05) differences between the two materials.

BACKGROUND: The clinical success rate with zinc phosphate cemented Procera crowns is high. The objective with this study was to determine whether CADCAM processed and zinc phosphate cemented Denzir copings would perform as well as zinc phosphate cemented Procera copings when tested in vitro in tension. METHODS: Twelve Procera copings and twenty-four Denzir copings were made. After the copings had been made, twelve of the Denzir copings were sandblasted on their internal surfaces. All copings were then cemented with zinc phosphate cement to carbon steel dies and transferred to water or artificial saliva. Two weeks after cementation, half of the samples were tested. The remaining samples were tested after one year in the storage medium. All tests were done in tension and evaluated with an ANOVA. RESULTS: Sandblasted and un-sandblasted Denzir copings performed as well as Procera copings. Storage in water or artificial saliva up to one year did not decrease the force needed to dislodge any of the coping groups. Three copings fractured during testing and one coping developed a crack during testing. The three complete fractures occurred in Procera copings, while the partly cracked coping was a Denzir coping. CONCLUSION: No significant differences existed between the different material groups, and the retentive force increased rather than decreased with time. Fewer fractures occurred in Denzir copings, explained by the higher fracture toughness of the Denzir material. Based on good clinical results with zinc phosphate cemented Procera crowns, we foresee that zinc phosphate cement luted Denzir copings are likely to perform well clinically.