THE JOURNAL OF - Dentsply

More documents

Recommendations

Info

Söderholm Fig 1 Sevriton and Severiton Cavity seal were products developed by the DeTrey/Amalgamated Dental Company. Sevriton Cavity Seal was the first product claimed to be able to bond to tooth tissues. 29 This product was developed by the Swiss chemist, Oskar Hagger. the fact that microscopic porosities enhanced the retention of dental materials. What he did not communicate clearly, though, was that by replacing a brittle cement layer with a ductile material, the bonding ability could be substantially enhanced. The latter fact was probably the reason why the acid etching technique resulted in a major breakthrough in dentistry when compared to previous approaches to bonding to teeth. However, when it comes to a ductile interface, Buonocore was not the first to use a ductile resin layer at the tooth surface in order to enhance retention. The first one who came up with that idea was a Swiss chemist, Oskar Hagger. Hagger worked for DeTrey/Amalgamated Dental Company, and had already in 1949 developed an adhesive product called Sevriton Cavity Seal 33 (Fig 1). This product consisted of glycerolphosphoric acid dimethacrylate and was intended for use as an adhesive for the chemically cured resin Sevriton. Sevriton Cavity Seal was indeed a revolutionary product, because it was the first product that claimed to be able to chemically bond to tooth structure. In an article published by Kramer and McLean in 1952, 29 these two investigators claimed that the glycerolphosphoric acid dimethacrylate of the Sevriton Cavity Seal increased the adhesion to dentin by penetrating the surface. Today we call the resin-penetrated zone the hybrid zone. This is also remarkable, because we often assume that hybridization is a more recent discovery than it obviously is. The year after Buonocore published his classic paper, he also published a paper with Brudevold and Wileman, 13 in which they evaluated Sevriton Cavity Seal and Sevriton. In that paper they claimed that the glycerolphosphoric acid dimethacrylate did not bond as well to enamel as a self-curing resin placed in intimate contact with a phosphoricacid–etched enamel surface did. However, when placed in contact with dentin, the glycerolphosphoric acid dimethacrylate provided some dentin bond enhancement. Considering Hagger’s fundamental work, there is no doubt that modern dental adhesive technology had its root in the late 1940s, when Hagger initiated the use of acidic monomers to achieve bonding to both enamel and dentin. What Buonocore really showed was that it was easier to achieve bonding to enamel than to dentin, something we all agree upon today. Even though Buonocore had proved that enamel bonding worked in 1955, 15 it would take until the late 1970s before enamel bonding became generally accepted. The turning point occurred when 3M sponsored the International Symposium on Enamel Etching in December of 1974. 38 During that symposium, researchers and clinicians with experience of enamel bonding presented their findings, and 3M published and distributed that information to academic institutions and opinion leaders. The idea to develop a resin system capable of bonding to dentin did not die with Hagger. Instead, Bowen, after his invention of modern composites, focused on dentin adhesives during the 1960s. During that decade, he formed work groups that outlined strategies for developing new dental adhesives. 7-11 Guiding principles during these discussions were: (a) dentin is a vital tissue and should not be exposed to strong acids, (b) the presence of water should be minimized, because water would shield bond sites of adhesive molecules, (c) the adhesive molecules should be at least bifunctional so one end could bond to tooth surface and the other to the resin of the composite. As a result of Bowen’s research, NPG-GMA (N-phenylglycine and glycidyl methacrylate) was introduced in 1965 as a potential dentin adhesive. The shear bond strength of this first generation adhesive was 1 to 3 MPa, and it soon became obvious that these products did not work clinically. During the late 1970s, new dentin adhesives were developed. Most of these products contained of bis-GMA/HEMA resins mixed with halophosphorous esters. The bonding mechanism of these adhesives was believed to be due to ionic bond formation between halophosphorous groups and calcium ions of the tooth surface. Even though these second generation products were significant improvements compared to the first generation products, they still did not result in clinical success. A major breakthrough occurred in 1979, when Fusayama and his coworkers presented their findings, claiming they could bond to acid-etched dentin without any significant problems with pulp reactions. 22 The paper was met with ample skepticism by authorities in pulp biology who argued that the acidity would cause pulp inflammations and even pulp necrosis. Fusayama, on the other hand, argued that his findings were just supporting Brännström and Nyborg’s claim that bacteria rather than acid was the key concern when it came to causing pulp damage. 12 Another important paper from Japan came in 1982, when Nakabayashi and coworkers published their paper “The promotion of adhesion by the infiltration of monomers into tooth substrates”. This paper presented the hybrid-layer formation theory. 35 The findings from Fusayama’s and Nakabayashi’s groups 228 The Journal of Adhesive Dentistry
Söderholm resulted in a new generation of adhesives, the so-called 3rd generation adhesives. Manufacturers of adhesives were still somewhat reluctant to suggest an aggressive acid etching of the dentin. Instead, they tried to remove or modify the smear layer with a conditioner (often a weaker acidic solution) that was rinsed away before a hydrophilic primer was placed. These primers often consisted of 4-META and BPDM, and after primer application, an unfilled resin was placed. Other primers contained PENTA, HEMA and ethanol. One product used EDTA instead of acid to remove the smear layer and expose the collagen, and treated the exposed collagen fibers first with an aldehyde and then HEMA. 34 With that treatment, it was believed that the aldehyde would chemically bond to the collagen fiber and that the HEMA would then bond to the attached aldehyde molecules via a condensation reaction. The methacrylate groups of the HEMA molecule would then react with the composite. Interesting to mention is that Bowen and Cobb published a paper in 1983 entitled “A method for bonding to dentin and enamel”, 6 in which they claimed they could achieve an in vitro tensile bond strength corresponding to one ton per square inch. Translated into metric units, that would be 15.5 MPa. The bonding procedure was rather complex, but in that article, Bowen regarded this approach as a major breakthrough despite its complexity. Even though the 3rd generation adhesives were improvements, they did not result in long-term success. In 1985, Hansen and Asmussen correlated gap sizes around standardized cavities with the shear bond strength and found that gap-free restorations would be possible at shear bond strength values of around 23 MPa. 25 The best adhesives then had shear strength values of 18 MPa. Toward the end of the 1980s, some interesting research was published. The first paper came in 1985, when Bowen presented an abstract at an IADR meeting that contained information on the NTG-GMA he had been so enthusiastic about in his and Cobb’s 1983 publication. 5 In the 1985 presentation, he revealed that the adhesive he had used in 1983 contained an impurity. That impurity was nitric acid, and after purifying, the bond strength declined substantially. What he inadvertantly showed was how important it was to etch the dentin surface. Another important finding came in 1989, when Chigira et al treated an EDTA-conditioned dentin surface with aldehyde plus HEMA or HEMA only and found no difference in bond strength. 17 What they showed with that study was that collagen exposure and resin infiltration was the key behind dentin bonding, thereby supporting Nakabayashi’s hybridization theory. Some of the most important information came in 1994, when Van Herle’s group at the Catholic University of Leuven showed in a clinical study that the success rate of Scotchbond 2, a third generation dentin adhesive, exceeded 95% after 3 years. 43 Because of poor storage stability, Scotchbond 2 disappeared from the market almost immediately after it had been accepted and was replaced by Scotchbond MP, a 4th generation adhesive. At that time, it had started to become clear that by using more aggressive dentin treatments, the bond strength improved and exceeded the levels predicted by Hanssen and Asmusen for gap-free restorations. 25 Even though Fusayama and later on Nakabayashi had done extensive research on dentin etching and dentin bonding during the 1980s, it was during the early 1990s that dentin etching and dentin bonding first became widely accepted. The acceptance coincided with a symposium sponsored by 3M and later on published in Operative Dentistry. 4 Another important discovery was when Kanka 28 and Gwinnett 24 in two independent papers showed that bonding to dentin could be enhanced by using so-called moist bonding. Knowledge transfer is rarely an easy task, and when it came to introducing the 4th generation adhesives to the dental profession, it was soon clear that dentists did not really know how to do dentin bonding. Sometimes different components were used in the wrong order, and when it came to moist dentin, the definition differed quite widely. Because of these factors, there was a need for products that were easier to use, a demand to which the manufacturers soon responded. In an attempt to simplify dentin bonding, the primer and adhesive resin were combined. Unfortunately, the general perception among clinicians was often that by using a 5th rather than a 4th generation adhesive, the time needed for the bonding procedure could be decreased. In reality, though, such a belief was incorrect, because these systems required more time for the primer to diffuse into the collagen structure. Clinical studies that came out comparing the 4th and the 5th generation adhesives often suggested that the 4th generation adhesives performed somewhat better than the 5th generation adhesives. 1,14,31,42 Whether that difference was due to 5th generation adhesives curing too quickly has not been proven. However, in vitro results of different generation adhesives can be similar, independent of generation. 19 Simultaneously with the introduction of the 5th generation adhesives, new adhesives consisting of an acidic primer and an adhesive were also introduced. These systems often came from Japanese manufacturers of dental adhesives, and did not include the etching gel. Because of the generation terminology, these systems are referred to as the 6th generation of adhesives. In 1998, a new adhesive named Prompt-L-Pop was introduced, consisting of a delivery system that mixed the primer and the adhesive before it was applied. The popularity of this system grew quickly and it soon became quite clear that the market wanted a system that was self-etching and available in one single container. During the past few years, the trend has been to move the adhesive one step further by combining the acidic primer with the adhesive resin in an attempt to develop an all-in-one system, often marketed as 7th generation adhesives. The interest in the 7th generation products has been quite significant, despite the fact that these systems often perform less satisfactorily than many of the previous generation adhesives. 39 However, it is important to emphasize that all products, including the 7th generation adhesives, have learning curves. The knowledge generated during these trial periods is used to develop and improve products that do not perform as well as originally believed. Unfortunately, these development periods can be quite frustrating for the clinicians when faced with patients who have re- Vol 9, Supplement 2, 2007 229
Page 1 and 2: THE JOURNAL OF ADHESIVE DENTISTRY V
Page 3 and 4: Guest Editorial Satellite Symposium
Page 5 and 6: THE JOURNAL OF ADHESIVE DENTISTRY C
Page 7: Dental Adhesives …. How it All St
Page 11 and 12: Effectiveness of All-in-one Adhesiv
Page 13 and 14: Blunck/Zaslansky composites were us
Page 15 and 16: Blunck/Zaslansky 0 20 40 60 80 100
Page 17 and 18: Blunck/Zaslansky Table 3 Slopes of
Page 19 and 20: Blunk/Zaslansky many of the product
Page 21 and 22: Clinical Bonding of a Single-step S
Page 23 and 24: van Dijken et al DISCUSSION The rap
Page 25 and 26: Shear Bond Strength and Physicochem
Page 27 and 28: Latta Fig 1 Representative spectra
Page 29 and 30: Microshear Fatigue Testing of Tooth
Page 31 and 32: Braem Fig 1 Positioning of the dent
Page 33 and 34: Braem the number of steps but also
Page 35 and 36: Microleakage of Class V Composite R
Page 37 and 38: Rosales-Leal Fig 1 Percentage of ca
Page 39 and 40: Rosales-Leal fect the occlusal seal
Page 41 and 42: Microleakage of XP Bond in Class II
Page 43 and 44: Manhart/Trumm heim, Germany), resul
Page 45 and 46: Six-month Clinical Evaluation of XP
Page 47 and 48: Blunck et al Table 2 Results of the
Page 49 and 50: Adhesive Luting Revisited: Influenc
Page 51 and 52: Frankenberger et al Table 2 Results
Page 53 and 54: Frankenberger et al or resin coatin
Page 55 and 56: XP BOND in Self-curing Mode used fo
Page 57 and 58: Raffaelli et al Table 2 Bond streng
Page 59 and 60:
XP BOND in Self-curing mode used fo
Page 61 and 62:
Ferrari et al Table 2 Performance c
Page 63:
Sarrett Vol 9, Supplement 1, 2007 2
show all

THE JOURNAL OF - Dentsply

Create successful ePaper yourself

Delete template?

Save as template?