A Critical Review of the Durability of Adhesion to Tooth Tissue: Methods and Results

The immediate bonding effectiveness of contemporary adhesives is quite favorable, regardless of the approach used. In the long term, the bonding effectiveness of some adhesives drops dramatically, whereas the bond strengths of other adhesives are more stable. This review examines the fundamental processes that cause the adhesion of biomaterials to enamel and dentin to degrade with time. Non-carious class V clinical trials remain the ultimate test method for the assessment of bonding effectiveness, but in addition to being high-cost, they are time- and labor-consuming, and they provide little information on the true cause of clinical failure. Therefore, several laboratory protocols were developed to predict bond durability. This paper critically appraises methodologies that focus on chemical degradation patterns of hydrolysis and elution of interface components, as well as mechanically oriented test set-ups, such as fatigue and fracture toughness measurements. A correlation of in vitro and in vivo data revealed that, currently, the most validated method to assess adhesion durability involves aging of micro-specimens of biomaterials bonded to either enamel or dentin. After about 3 months, all classes of adhesives exhibited mechanical and morphological evidence of degradation that resembles in vivo aging effects. A comparison of contemporary adhesives revealed that the three-step etch-and-rinse adhesives remain the ‘gold standard’ in terms of durability. Any kind of simplification in the clinical application procedure results in loss of bonding effectiveness. Only the two-step self-etch adhesives approach the gold standard and do have some additional clinical benefits.

Cementation: methods and materials. Part two

This is a review of the literature of the last 21 years about cementing or luting indirect restorations to tooth structure. Recommendations are made as to the surface preparation of precious metals, non-precious metals, indirect composite materials, and all available porcelain materials including feldspathic, luecite reinforced, lithium di-silicate, slip cast aluminum oxide, densely sintered aluminum oxide, and zirconia prior to luting. Using data from a variety of sources, product categories of materials and various bonding materials and procedures are ranked according to their bond strength and durability.

The role of cements in dental lant success, Part I

Peri-implant disease can be the result of residual excess cement. While there is no ideal implant restorative cement, the clinician must be aware that the material selection for implant restorations should not be based on properties which are more suited to restoration of the natural dentition. More appropriate criteria would be those unique to implants and the specific challenges these medical devices bring to the restorative dentist.

Crown and bridge cements: clinical applications

Cement selection can be confusing because factors such as substrate, the type of restoration, and patient needs must be considered. Some substrates require additional treatment before cementation. This article describes the most commonly used traditional crown and bridge cements (GI and RMGI) used for metal and metal-ceramic restorations, and resin cements used for all-ceramic restorations. Advantages, disadvantages, indications, and contraindications of cements have been reviewed. Recommended uses of cements for metal, ceramic, and laboratory composite restorations have been presented. General guidelines for surface treatment ot silica- and zirconia-based restorations when using resin cements have been discussed.

Extension for prevention: margin placement

This article will review the concept of extension for prevention popularized by G.V. Black around the early 1900s. Concepts of extension and prevention have changed over the years with a more informed knowledge of the caries process, improved materials, cutting instruments, and techniques. The reasons for placement of the outline form relative to the tooth morphology, gingival tissue, relationship to adjacent teeth, and the choice of material will be described for all of the materials used in restorative dentistry. Research will be cited to support the scientific basis for outline form placement.

Considerations for proper selection of dental cements

Selecting the proper cement for sufficient bond strength has become progressively complicated as the number of different materials for indirect restorations has increased. The success of any restoration is highly dependent on the proper cement being chosen and used. The function of the cement is not only to seal the restoration on the tooth but also, in some cases, to support the retention of the restoration. This ability to strengthen retention varies by the cement chosen by the clinician; therefore, careful consideration must precede cement selection.

Interdisciplinary treatment of cervical lesions

Soft tissue grafting is an integral part of treatment of cervical lesions due to the common lack of adequate attached gingiva and root exposure associated with these lesions. Complete root coverage is a predictable outcome for Miller Class I and II recession defects, and partial root coverage can be achieved in Miller Class III defects. In the esthetic zone, it is desirable to cover as much of the root as possible, and all sites require an adequate zone of attached gingiva, especially adjacent to a restoration. Restorations are required for cervical lesions with excessive depth and significant involvement of the enamel, but they should be avoided where the lesion is shallow and the enamel involvement is minimal. Of course, some sites will require both soft-tissue grafting and placement of a restoration. An interdisciplinary approach to treating cervical lesions will create the most biologically appropriate, stable, and esthetic outcome. Establishing the appropriate tooth form first in treatment planning and sequencing will determine the gingival level and extent of periodontal procedures necessary to achieve the desired outcome.

Micromorphology of resin-dentin interfaces using one-bottle etch&rinse and self-etching adhesive systems on laser-treated dentin surfaces: a confocal laser scanning microscope analysis

BACKGROUND AND OBJECTIVES

This study evaluated the hybrid layer (HL) morphology created by three adhesive systems (AS) on dentin surfaces treated with Er:YAG laser using two irradiation parameters.

STUDY DESIGN

Occlusal flat dentin surfaces of 36 human third molars were assigned into nine groups (n = 4) according to the following ASs: one bottle etch&rinse Single Bond Plus (3M ESPE), two-step Clearfil Protect Bond (Kuraray), and all-in-one S(3) Bond (Kuraray) self-etching, which were labeled with rhodamine B or fluorescein isothiocyanate-dextran and were applied to dentin surfaces that were irradiated with Er:YAG laser at either 120 (38.7 J/cm(2)) or 200 mJ/pulse (64.5 J/cm(2)), or were applied to untreated dentin surfaces (control group). The ASs were light-activated following MI and the bonded surfaces were restored with resin composite Z250 (3M ESPE). After 24 hours of storage in vegetable oil, the restored teeth were vertically, serially sectioned into 1-mm thick slabs, which had the adhesive interfaces analyzed with confocal laser microscope (CLSM-LSM 510 Meta). CLSM images were recorded in the fluorescent mode from three different regions along each bonded interface.

RESULTS

Non-uniform HL was created on laser-irradiated dentin surfaces regardless of laser irradiation protocol for all AS, while regular and uniform HL was observed in the control groups. "Stretch mark"-like red lines were found within the HL as a result of resin infiltration into dentin microfissures, which were predominantly observed in 200 mJ/pulse groups regardless of AS. Poor resin infiltration into peritubular dentin was observed in most regions of adhesive interfaces created by all ASs on laser-irradiated dentin, resulting in thin resin tags with neither funnel-shaped morphology nor lateral resin projections.

CONCLUSION

Laser irradiation of dentin surfaces at 120 or 200 mJ/pulse resulted in morphological changes in HL and resin tags for all ASs evaluated in the study.

Adhesion. Adhesive dentistry: the good, the bad, and the ugly

For more than 30 years, Compendium has provided its readers with university-based continuing education and editorial, demonstrating the latest advances in clinical procedures and techniques. Using the same peer-reviewed format and influence/direction from Compendium's distinguished editorial board, Special Report will provide insight on the latest advances in product technologies and the resulting benefits to both you and your patients. A discussion by the author on new clinical/laboratory research and product development strategies, as well as what the results could mean for dental treatment, will also be included. Focusing on one product category per issue provides a detailed review of the category and a comprehensive resource to help guide your treatment planning process.

[Effects of application methods of self-etching adhesives on resin-dentin bonding]

OBJECTIVE

To investigate the effects of application time and rubbing action of self-etching adhesives on resin-dentin bond strength and interface morphology in vitro.

METHODS

Caries-free human third molars were wet ground to expose dentin surface. Three self-etching bonding agents were applied with varying application time and with/without rubbing. The microtensile bond strength and interface morphology were evaluated.

RESULTS

When etching time was shortened, normal and prolonged, the bond strength was bonding agent 1 (Adper Prompt): (16.30 +/- 2.59), (23.13 +/- 2.56), (22.28 +/- 2.83) MPa, bonding agent 2 (Xeno III): (15.17 +/- 6.07), (34.50 +/- 3.64), (24.87 +/- 7.01) MPa, bonding agent 3 (Clearfil SE Bond): (29.92 +/- 3.32), (42.21 +/- 6.28), (41.07 +/- 3.93) MPa. When etching was applied with and without rubbing, the bond strength was bonding agent 1 (23.13 +/- 2.56), (12.53 +/- 3.73) MPa, bonding agent 2 (23.98 +/- 3.86), (34.50 +/- 3.64) MPa, bonding agent 3 (48.37 +/- 4.95), (42.21 +/- 6.28) MPa.

CONCLUSIONS

Shortening application time decreased bond strength of self-etching adhesives, while prolonging application time did not increase bond strength of self-etching adhesives. Not all self-etching adhesives applied with rubbing showed increased bond strength to dentin, which is product-dependent. Manufactures' instructions should be followed to achieve optimum bonding.

Dental adhesives--the foundation of esthetic dentistry

The clinical success of adhesive restorations depends on knowing the materials and how they are used in indicated areas. This article is designed to help clinicians understand the various protocols that are best suited for different clinical cases by discussing contemporary dental adhesive systems. The article also presents rationales for selecting adhesive systems for specific cavity classes, highlights the working principles underlying each clinical procedure, and explains technique problems in dental adhesive procedures. Clinical preventive measures to ensure longevity of direct adhesive restorations also are discussed.

Dental cements for definitive luting: a review and practical clinical considerations

Dental cement used to attach an indirect restoration to a prepared tooth is called a luting agent. A clinically relevant discussion of conventional and contemporary definitive luting agents is presented in this article. Physical properties are listed in table form to assist in comparison and decision-making. Additional subtopics include luting agent requirements, classifications, retention and bonding, cement considerations for implant-supported teeth, and fatigue failure.

Resin Tag Length of One-Step and Self-Etching Adhesives Bonded to Unground Enamel

Length of resin tags yielded by utilization of an one-step conventional adhesive system and self-etching adhesive system on unground enamel was observed. In study Groups I and III, the enamel surface was etched for 60 seconds with 35% phosphoric acid gel and adhesive systems PQ1 (Ultradent Products, Inc) and Adper Prompt L Pop (3M/ESPE) were applied. Adper Prompt L Pop (3M/ESPE) was also applied in Group II in accordance with the manufacturer's recommendations. After application of these adhesive systems to dental enamel, specimens were prepared for light microscopy analysis to ascertain degree of penetration (x400). The results were submitted to an analysis of variance at the 5% level; whenever there was significance, the Tukey test was applied at the 5% level. It was found that acid etching prior to application of conventional and self-etching adhesive materials provided higher penetration of the adhesive into the unground enamel surface compared to that achieved solely by application of self-etching adhesive.

Bond strength of orthodontic brackets using different light and self-curing cements

The purpose of the study was to evaluate the shear bond strength of stainless steel orthodontic brackets directly bonded to extracted human premolar teeth. Fifty teeth were randomly divided into five groups: (1) System One (chemically cured composite resin), (2) Light Bond (light-cured composite resin), (3) Vivaglass Cem (self-curing glass ionomer cement), (4) Fuji Ortho LC (light-cured glass ionomer cement) used after 37% orthophosphoric acid-etching of enamel (5) Fuji Ortho LC without orthophosphoric acid-etching. The brackets were placed on the buccal and lingual surfaces of each tooth, and the specimens were stored in distilled water (24 hours) at 37 degrees C and thermocycled. Teeth were mounted on acrylic block frames, and brackets were debonded using an Instron machine. Shear bond strength values at fracture (Nw) were recorded. ANOVA and Student-Newman-Keuls multiple comparison tests were performed (P < .05). Bonding failure site was recorded by stereomicroscope and analyzed by Chi-square test, selected specimens of each group were observed by scanning electron microscope. System One attained the highest bond strength. Light Bond and Fuji Ortho LC, when using an acid-etching technique, obtained bond strengths that were within the range of estimated bond strength values for successful clinical bonding. Fuji Ortho LC and Vivaglass Cem left an almost clean enamel surface after debracketing.

Crowns and other extra-coronal restorations: try-in and cementation of crowns

Having successfully negotiated the planning, preparation, impression and prescription of your crown, the cementation stage represents the culmination of all your efforts. This stage is not difficult, but a successful outcome needs as much care as the preceding stages. Once a restoration is cemented there is no scope for modification or repeat You have to get it right first time. Decemented crowns often have thick layers of residual cement suggesting problems with either initial seating or cement handling. When the fate of restorations costing hundreds of pounds depends on correct proportioning of cements and the quality of the mix, the value of a well-trained and experienced dental nurse is easy to see. Both dentist and nurse need a working knowledge of the materials they are handling.

A review of orthodontic cements and adhesives

Dental cements and resins are used intraorally to secure fixed orthodontic devices. Although cements are still used, the popularity of resin and resin-cement hybrid materials is increasing because of their improved physical properties and low solubility in oral fluids. Some cements bond chemically to enamel, but bond strengths are low because cements are brittle and fracture cohesively. Resin adhesives penetrate micropores in etched enamel and mechanical retentions in orthodontic devices, resulting in higher bond strengths because resins are more fracture resistant than cements. Resins, however, do not bond well in the presence of moisture, and their attachment to surfaces is primarily mechanical. Hybridized materials combine the advantages of cements and resins but also have certain disadvantages. Optimal material selection and application require an understanding of the chemical differences and physical limitations of today's orthodontic cements, resins, and hybrid materials.

Predictions of cement microfracture under crowns using 3D-FEA

PURPOSE

The objective of this research study was to test the effects of (1) crown margin type, (2) cement type, (3) cement thickness, (4) loading direction, and (5) loading magnitude on stress levels and distributions within luting cement that might lead to cement microfracture using three-dimensional Finite Element Analysis techniques.

MATERIALS AND METHODS

Thirty-two three-dimensional computer models, as well as models for standards, were generated for a mandibular first premolar. Crown preparations exhibited shoulder or chamfer margin configurations, and zinc phosphate, zinc polycarboxylate, glass ionomer, and resin cements were used in thicknesses of 25 or 100 microm. Modeled crowns were loaded axially or obliquely at 10 and 100 MPa. Areas and levels of stress concentrations within the cement were determined.

RESULTS

Stresses in the cement were low for all situations except 100 MPa oblique stressing. Stresses at the margins of crowns with chamfer marginal configuration were higher than those with shoulder margins. Stresses under oblique stressing were 10 to 150 times higher than under axial stressing. Except for Zn phosphate cement, cement thickness minimally affected stress levels and distributions. Greater stresses were found in cements with the greater Young's modulus.

CONCLUSIONS

Although the chamfer margin design could lead to greater stresses near the margins that places the cement at risk for microfracture and possible crown failure, glass-ionomer and composite resin cements have more favorable mechanical properties for resisting microfracture.

Creating a reliable bond. An all-in-one system

This paper explains the reasons why a new adhesion concept was developed, how it was conceived and what properties and test results were achieved with the product Prompt L-Pop that follows this new concept. Therefore, a short historical introduction into the development of adhesive materials is given followed by a summary of today's state-of-the-art techniques. The requirements for the new adhesion concept are pointed out and the outcome of the effort in the development is explained in more detail. In vitro and in vivo test results of Prompt L-Pop support the new concept by revealing excellent bond strength values in combination with good marginal adaptation and a significantly reduced post operative sensitivity. Finally, further developments regarding the new concept are discussed, such as the use of Prompt L-Pop in combination with plasma curing lights or indirect restorations.

Marginal integrity after fatigue loading of ceramic inlay restorations luted with three different cements

PURPOSE

To evaluate the effect of fatigue loading on the quality of the cement around the margins of adhesive ceramic MOD inlays.

MATERIALS AND METHODS

Non-metal IPS Corum porcelain inlays were made and cemented either with the resin-based composite Variolink, the compomer Dyract-Cem or the glass-ionomer cement Ketac-Cem. For each system, half of the specimens were subjected to thermal and mechanical load cycling to simulate fatigue loading. All teeth were then sectioned and evaluated by SEM on topography and by optical microscopy for dye penetration.

RESULTS

Before loading, all systems showed good marginal integrity. After loading, inlays cemented with Variolink and Dyract-Cem showed no significant (P > 0.05) increase in marginal break down, however restorations cemented with Ketac-Cem, showed a significant (P < 0.05) deterioration at the margins.

Contemporary evaluation of dental cements

Today, the clinician has numerous dental cements available for luting of restorations to prepared teeth. Compared to traditional cements, many of the newer cements have improved physical properties. In this article, we analyze available cements in terms of these physical properties based on scientific data and attempts to determine their effect on long-term clinical performance. We conclude that these improved physical properties do not necessarily result in improved clinical performance. We also conclude that although these newer cements have specific clinical applications, they should not be routinely used for the cementation of metal castings because they are clearly more technique-sensitive than traditional luting agents. Zinc-phosphate cement remains the cement of choice for cementing cast gold and metal-ceramic restorations.

Mutagenic potential of root canal sealers: evaluation through Ames testing

The mutagenic potential of 12 commercially available dental cements and of two 'pure substances' (zinc oxide and eugenol) used in root canal filling were examined. The cements were prepared according to the manufacturers' indications and set for defined times. Ames tests were performed in their extracts by using Salmonella typhimurium strains TA 98 and TA 100. The results showed that most cements present strong bactericidal activity that disappears or decreases remarkably in time. One of the tested cements showed mutagenicity with both Salmonella strains. Two cements yielded doubtful results. The remaining cements and the two 'pure substances' showed no mutagenic potential. The authors conclude that it is convenient to examine endodontic cements with the Ames test and to eliminate those that present mutagenicity in time.

Dual-cure luting composites: Part I: Filler particle distribution

Fourteen dual-cure luting composites were analyzed for their filler particle shape, predominant and maximum filler size, and filler weight in function of their clinical use. Polished surfaces were etched with an argon ion beam and studied by means of scanning electron microscopy. The type of filler particles, either inorganic or prepolymerized, could clearly be recognized. Their shapes were angular, rounded or spherical, depending on the product. The maximum filler size varied extremely from less than 1 micron to 250 microns. A particle-size distribution analyser disclosed a bell-shaped filler-size distribution. The predominant filler size for all the products was much smaller than the maximum filler size. The filler weight varied from 36 to 77%. After ion etching, some products showed small areas with a low degree of filler loading. A classification of the luting composites based on the maximum filler size is proposed. Since the particle size varies widely within the group of products analyzed, a standard specification for luting composites is urgently needed.