Bonding Systems for Dentin in Adhesive Dentistry · 2017-12-18 · Bonding Systems for Dentin in...

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Release date: January 12, 2018

Expiration date: January 11, 2021

Bonding Systems for Dentin in

Adhesive Dentistry

Updated 1st Edition

By

Patricia W. Kihn, DDS, MS

P.O. Box 1930Brockton, MA 02303800-438-8888

Dental Planner: Karen Hallisey, DMDThe planner has disclosed that she has no significant financial or other conflicts of interest pertaining to this course book.

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ABOUT THE AUTHORPatricia W. Kihn, DDS, MS, is the director of regulatory clinical support activities and corporate complaint officer for DENTSPLY International, and adjunct faculty in the Department of Restorative Dentistry at the University of Maryland, Dental School in Baltimore, Maryland.

Patricia W. Kihn has disclosed that she has no significant financial or other conflicts of interest pertaining to this course book.

ABOUT THE UPDATED FIRST EDITION PEER REVIEWEREvan B. Rosen, DMD, MPH, is a maxillofacial prosthodontist and part-time lecturer at the Harvard School of Dental Medicine. Dr. Rosen completed his doctor of dental medicine degree at the University of Florida College of Dentistry and his prosthodontics residency at the Eastman Institute for Oral Health in Rochester, New York. Dr. Rosen continued his professional training by completing a fellowship in maxillofacial prosthetics at Memorial Sloan Kettering Cancer Center in New York City. Dr. Rosen is actively engaged in research focusing on quality-of-life outcomes and the management of medically complex patients.

Evan B. Rosen has disclosed that he has no significant financial or other conflicts of interest pertaining to this course book.

FP1217WS

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WESTERN SCHOOLScourse evaluation

BONDING SYSTEMS FOR DENTIN IN ADHESIVE DENTISTRY

INSTRUCTIONS: Using the scale below, please respond to the following evaluation statements. All responses should be recorded in the lower right-hand corner of the FasTrax answer sheet, in the section marked “Evaluation.” Be sure to fill in each corresponding answer circle completely using blue or black ink. Leave any remaining answer circles blank.

A B C D

Agree Agree Disagree Disagree Strongly Somewhat Somewhat Strongly

OBJECTIVES: After completing this course, I am able to: 1. Discuss the evolution of adhesive dentistry.

2. Explain the dental hard tissues involved in bonding.

3. Identify the various generations of bonding agents for dentin.

4. Explain ongoing research methods associated with bonding systems, including preparation techniques, marginal seal, leakage, and bond strength.

COURSE CONTENT 5. The course content was presented in a well-organized and clearly written manner.

6. The course content was presented in a fair, unbiased, and balanced manner.

7. The course content presented current developments in the field.

8. The course was relevant to my professional practice or interests.

9. The final examination was at an appropriate level for the content of the course.

10. The course expanded my knowledge and enhanced my skills related to the subject matter.

11. I intend to apply the knowledge and skills I’ve learned to my practice.

A. Yes B. Unsure C. No D. Not Applicable

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A. Yes B. No C. Not Applicable 12. Western Schools staff was responsive to my request for disability accommodations. 13. The Western Schools website was informative and easy to navigate. 14. The process of ordering was easy and efficient. 15. Western Schools staff was knowledgeable and helpful in addressing my questions or problems.

ATTESTATION

16. I certify that I have read the course materials and personally completed the final examination based on the material presented. Mark “A” for Agree and “B” for Disagree.

vcontinued on next page

Course Evaluation— vi Bonding Systems for Dentin in Adhesive Dentistry

COURSE RATING

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C O N T E N T SCourse Evaluation ....................................................................................................................................................vTables .......................................................................................................................................................ixIntroduction .............................................................................................................................................xi

Course Objectives .........................................................................................................................xiBonding Systems for Dentin in Adhesive Dentistry ..............................................................................1

The Evolution of Adhesive Dentistry ............................................................................................1

The Dental Hard Tissues ................................................................................................................1

Bonding to Enamel ..................................................................................................................2

Bonding to Dentin ....................................................................................................................2

The Smear Layer ......................................................................................................................2

The Hybrid Layer .....................................................................................................................3

Bonding Agents for Dentin ............................................................................................................3

First Generation .......................................................................................................................4

Second Generation ...................................................................................................................4

Third Generation ......................................................................................................................4

Fourth Generation ....................................................................................................................4

Fifth Generation .......................................................................................................................4

Sixth Generation ......................................................................................................................5

Seventh Generation ..................................................................................................................5

Case Scenario: The “Hometown” Dentist ......................................................................................6

Questions ..................................................................................................................................6

Discussion ................................................................................................................................6

Considerations in Adhesive Restorative Dentistry ........................................................................7

Summary ........................................................................................................................................8Exam Questions ........................................................................................................................................9References ...............................................................................................................................................13

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T A B L E STable 1: Requirements for Optimal Interface Bonding .............................................................................1

Table 2: Characteristics of an Ideal Dentin Bonding Agent ......................................................................3

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I N T R O D U C T I O N

COURSE OBJECTIVESAfter completing this course, the learner will be able to:

1. Discuss the evolution of adhesive dentistry.

2. Explain the dental hard tissues involved in bonding.

3. Identify the various generations of bonding agents for dentin.

4. Explain ongoing research methods associated with bonding systems, including preparation techniques, marginal seal, leakage, and bond strength.

Adhesive dentistry is the restoration of a tooth’s form and function through the use of chemical compounds that bond to the tooth structure. Adhesive dentistry has evolved through several gen-

erations of bonding techniques and systems. Numerous advances in clinical performance provide many advantages, including increased bond strength, patient comfort, minimal tooth preparation, excellent aesthetics, low thermal conductivity of resins, elimination of galvanic reactions, fast setting of the restorative material, and ease of color matching to adjacent teeth. However, challenges have persisted throughout each new generation of adhesion technique and materials, as certain adhesive systems may present technique sensitivity of adhesives and resins, polymerization shrinkage problems, and coef-ficients of thermal expansion that are greater than those of the dental hard tissues that they replace (Malhotra, Mala, & Acharya, 2011). As additional restorative products are introduced into the market-place, it will be a continuing challenge to understand the clinical benefits and pitfalls of these new and changing materials.

After completing this basic-level course, dental professionals will understand the history of adhesive bonding systems and will be able describe the necessary conditions for ideal adhesive bonding. Dental professionals will also gain a basic understanding of different dental adhesive systems and understand the advantages and disadvantages of each. Having a basic understanding of the science behind adhesive dentistry is imperative, as nearly 75% of people living in the United States have some form of dental restoration (Dye, Li, & Beltran-Aguilar, 2012). Understanding adhesive dentistry will allow dental pro-fessionals to practice responsibly and yield better restoration outcomes for their patients.

B O N D I N G S Y S T E M S F O R D E N T I N I N

A D H E S I V E D E N T I S T R Y

THE EVOLUTION OF ADHESIVE DENTISTRY

Buonocore (1955) introduced the first practi-cal method of bonding acrylic filling mate-

rials to enamel and subsequently described the characteristics of an ideal bonding system. The principles of an ideal bonding system include biocompatibility, bond strength, absence of microleakage, chemical compatibility with restorative materials, physical characteristics, and practicability (Nawareg et al., 2015). The principal requirements for the formation of an optimally bonded interface are summarized in Table 1 (D’Arcangelo et al., 2015).

Adhesive dentistry relies on a micromechan-ical bond between tooth and restorative material achieved through retention of the resin within surface pits and microtopography created in enamel and dentin by acid etching (Rosa, Piva, & Silva, 2015).

THE DENTAL HARD TISSUES

Enamel is highly inorganic and primarily composed of hydroxyapatite crystals. By

weight, it is composed of approximately 96% carbonated apatite. A minor component of the material is made of water (approximately 3%) and organic matrix (approximately 1%) by weight (Duverger, Beniash, & Morasso, 2016).

The enamel crystals are aligned in various ori-entations to form prisms, which are packed together densely and are roughly parallel to each other and oriented with their long axes running from the dental-enamel junction (DEJ) to the surface of the tooth.

Dentin differs greatly from enamel in struc-ture and chemical composition. The organic phase of dentin is almost exclusively 90% by weight composed of type I collagen. There are hydroxyapatite crystals that are interspersed among a network of collagen fibers and together

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TABLE 1: REQUIREMENTS FOR OPTIMAL INTERFACE BONDING

• Substrate surface should be clean.

• Adhesive must wet bonding surface, have low contact angle, and spread readily.

• There must be intimate approximation of adhesive and substrate without air or contaminant entrapment.

• Interfacial strength should sufficiently resist intraoral debonding forces.

• Adhesive must be well cured (if indicated) under the conditions recommended for use.

• Surface treatment may be modified to improved adhesion by etching, silane coupling, or other mechanical or chemical means as appropriate and indicated by manufacturer’s instruction.

Note: From Western Schools, 2018.

2 Bonding Systems for Dentin in Adhesive Dentistry

form a spongelike matrix consisting of inter-tubular and peritubular dentin. Primary tubules extend from the pulp outward toward the DEJ, with secondary tubules often running laterally and connecting primary tubules. The density of tubules decreases across the thickness of the dentin at the DEJ (Bertassoni, Orgel, Antipova, & Swain, 2012).

Within the tubules, odontoblastic processes extend from the pulp and the tubules are filled with a dentinal fluid containing calcium and phosphate ions as well as other extracellular fluids (Pashley, Pashley, Carvalho, & Tay, 2002). Dentin is inherently wet because of this organic tissue and especially the fluid; during cavity preparation, the deeper a preparation, the more fluid is likely to be encountered. Further, if enamel or cementum or other material does not seal the dentinal tubules, fluid is able to flow outward from the pulp, and substances dissolved in oral fluids are able to diffuse into the tubules. Dentinal permeability is central to the hydrodynamic theory of dentin sensi-tivity, which ascribes fluid movement in the tubules to activation of nerve fibers within the pulp, thus causing pain (Pashley et al., 2002). Accordingly, consideration must be given to the resistance to fluid flow within the tubules, which is directly related to the number of open tubules, the length of the tubules, and occlu-sion of the ends of the tubules. Tubule length is related to proximity to the pulp, with shorter tubules located near to the pulp such that there is less resistance to flow and greater fluid flow through the tubules (Chung, Jung, & Oh, 2013).

Bonding to EnamelThe relatively consistent composition of

enamel provides a predictable substrate for bond-ing, but the enamel surface must be prepared properly to achieve an adequate bond. Plaque and debris (including a “hydroxyapatite-rich” smear layer formed during cavity preparation) must

be removed to allow mechanical interlocking between bonding agent and tooth.

The first use of a phosphoric acid solution to dissolve hydroxyapatite crystallites on the enamel surface was proposed by Buonocore (1955), and current acid etching procedures use a 30% to 40% phosphoric acid solution with subsequent rinsing with water and drying. Acid etching removes the smear layer created during cavity preparation, dissolving about 10 µm of surface enamel with acid penetration between and within the prisms to a depth of 10 to 20 µm. The result is a roughened enamel surface with an increased surface area and a higher surface energy, both of which promote wettability and improved mechanical retention (Sofan et al., 2017). Bonding agents can flow into the enamel microtopography, forming resin tags that pro-vide micromechanical retention of the bonding agent to enamel.

Bonding to DentinBecause dentin is a complex, dynamic tis-

sue, development of an ideal bonding agent has been challenging. As noted previously, dentin has variability in structure and permeability, which can greatly affect bonding. Additionally, there is variability in surface moisture as well as collagen structure in caries-affected dentin. The presence of water in the dentin and fluid flow in the tubules necessitates a hydrophilic bonding system. Furthermore, when cut, dentin forms a highly variable smear layer comprising debris, collagen, bacteria, and inorganic tooth particles. In bonding to dentin, the smear layer and the hybrid layer play key roles (Tjaderhane, 2015).

The Smear LayerAs noted previously, the dentin smear layer is

a porous layer of debris, hydroxyapatite, bacteria, and mineralized collagen matrix. While the smear layer occludes dentinal tubules and increases the resistance to fluid flow, it is a barrier between

Bonding Systems for Dentin in Adhesive Dentistry 3

the bonding agent and the substrate. Further, the smear layer is poorly attached to the den-tin, resulting in lowered strengths when bonding directly to the unmodified smear layer (Frassetto et al., 2016).

Altering the smear layer before applying adhesives will increase bond strengths. There are three available options with regard to the smear layer, namely, total removal, partial dissolution and removal, or modification to allow use of the porosities within the smear layer. Each option involves the use of an acidic solution to treat the smear layer. The smear layer decreases fluid flow; therefore, its reten-tion is desirable. Well-hybridized resin tags in bonded dentin reduce flow and have the additional advantage of not being acid labile. Acid-etched dentin has had the smear layer removed and offers no surface resistance to fluid flow (Ikemura, Kadoma, & Endo, 2011; Van Meerbeek et al., 2011).

The Hybrid LayerThe hybrid layer is a transition zone located

between mineralized dentin and an applied resin. It is an important component in dentin bond-ing systems and two processes are involved in its formation. First, acid demineralization of dentin creates a network or scaffold of collagen fibers. These exposed collagen fibers will col-lapse if the dentin is dried; consequently, the dentin must be kept moist until treated with a hydrophilic primer. The primer infiltrates the moist collagen and extends through the collagen layer to the demineralized peritubular dentin, wetting and increasing the surface energy of the collagen network. The resin component of the bonding system then penetrates the conditioned dentin and copolymerizes with the primer to form an intermingled layer of collagen and resin. Thus dentin and resin are intertwined within the hybrid layer such that there is micromechanical interlocking of resin and the mineral portion of

dentin together with chemical bonding to the collagen. Additionally, resin flows into the open dentinal tubules and results in resin tag forma-tion, possibly contributing to the overall bond strength. The density of resin tags is greater closer to the pulp, with fewer resin tags close to the DEJ, where there are fewer tubules (Ikemura et al., 2011).

BONDING AGENTS FOR DENTIN

Adhesive dentistry has advanced through successive generations of dentin bonding

techniques (Sofan et al., 2017), the current gen-eration of bonding agents being far superior to earlier adhesives. The characteristics of an ideal bonding agent are summarized in Table 2.

The development of the successive genera-tions of dentin bonding techniques has not been completely chronological. For convenience, they will be discussed in terms of the progres-sion of the technology rather than chronology.

TABLE 2: CHARACTERISTICS OF AN IDEAL DENTIN BONDING AGENT

• High initial and permanent bond strengths to dentin and enamel

• Ability to minimize microleakage

• Biocompatibility

• Mechanical durability

• Ease of use with minimal technique sensitivity

• Good shelf life (material does not quickly expire)

• Compatibility with a wide range of resins

• Absence of toxicity

• No sensitivity to either operator or patient

• Sealing of tooth surfaces from oral fluids

Note. Adapted from Sofan et al., 2017.


First GenerationThe first generation of bonding materials

was little more than a variation of enamel bond-ing agents, exhibiting a weak chemical inter-action between bonding agent and calcium ions in the dentin. The chemical bonds were weak and easily hydrolyzed with bond strengths from 1 to 3 MPa. This generation of bonding mate-rials was intended mainly for class III and V restorations. An adhesive solution containing N-phenylglycine and glycidyl methacrylate was included in this generation (Ozer & Blatz, 2013). The use of an amalgam-like restoration form was still highly recommended, and postop-erative sensitivity was common with posterior occlusal restorations.

Second GenerationThe second generation of bonding agents

was characterized by the addition of components designed to reduce hydrolysis of phosphate- hydroxyapatite bonds. Ionic bonding was still the primary mode of adhesion to dentin and chlorophosphate groups facilitated the bonding. There was no alteration of the dentin surface before resin application and the smear layer was used for bonding. Bond strengths continued to be low (4 to 6 MPa) and postoperative sensitiv-ity in posterior restorations was not significantly reduced (Ozer & Blatz, 2013).

Third GenerationThe third generation of bonding agents

was characterized by the addition of a separate “ priming” and/or “conditioning” solution, or series of solutions, to modify the dentin sur-face before resin application. This made pos-sible the opening of dentinal tubules and ultimately increased permeability for bonding. Predictable higher bond strengths compared with second- generation adhesives were achieved, for example, up to 10 MPa, although the clinical use of these materials was more complex and

technique sensitive. The third-generation prod-ucts also enabled bonding to other substrates such as ceramics and metals. Postoperative sen-sitivity was decreased and the need for retention form was diminished, but longevity of the bond remained a problem (Ozer & Blatz, 2013).

Fourth GenerationAdhesive strategies of the fourth-generation

systems were characterized by “moist dentinal bonding” with an acetone-based primer com-bined with a “total etch” using phosphoric acid conditioning. This generation allowed total removal of the smear layer. These systems used separate priming and adhesive components but created dentin bonding through hybridization and formation of a collagen-resin “hybrid zone.” The primers of the fourth-generation bonding agents carried adhesion promoters into the acid-demineralized collagen-containing layer, simul-taneously capturing and evaporating residual moisture. The resulting hybrid zone was char-acterized as collagen fibrils encapsulated within polymerized adhesive resins.

Fifth GenerationFifth-generation bonding systems were

designed to increase the reliability of fourth-generation systems and simplify their clinical use, although most systems required multiple steps such as placement of several layers of material, air-drying, and light-curing. Two types of fifth-generation materials were developed, namely, the one-bottle system and the self-etching primer system, both using the total etch concept to form a hybrid layer similar to that of fourth-generation systems.

One-bottle systems, such as Prime & Bond

(introduced in 1994 by Dentsply Caulk), com-bined primer and adhesive in a single solu-tion applied after simultaneous etching of the enamel and dentin. This product contained the hydrophobic monomer urethane dimethacrylate


(UDMA) and an adhesion promoter, dipentae-rythritol pentaacrylate phosphoric acid ester (PENTA). The UDMA ensured proper polymer-ization and cross-linking that bonded to surface hydroxyl groups through its urethane group (Eliades, 1994), whereas PENTA facilitated penetration of resin monomers into dentin for micromechanical bonding (Van Meerbeek, Inokoshi, Braem, Lambrechts, & Vanherle, 1992). Nanofillers were added to reinforce the adhesive layer in the bonding interface. Mechanical interlocking of resin tags, adhe-sive lateral branches, and hybrid layer forma-tion created a reliable bond (Mason, Calabrese, & Graif, 1998; Tay, Gwinnett, Pang, & Wei, 1994), and the system combined technique sim-plicity with high dentin bond strengths (>20 MPa). Furthermore, marginal integrity was improved through increased resistance to mar-ginal stress.

Self-etch systems combined the etching and priming steps to reduce working time by elimi-nating the rinse step and lessening the possibil-ity of collagen collapse because of overdrying. However, the solution must be refreshed during use and it is possible for residual smear layer to be retained between the adhesive layer and dentin during clinical application. The quality of the bond to enamel with self-etch systems tended to be less predictable, and bond strengths were not significantly different from those achieved with the one-bottle systems (Cardoso et al., 2011; Ozer & Blatz, 2013).

Sixth GenerationSixth-generation materials attempted to

achieve a bond to enamel and dentin using only one solution. These materials were called self-etch adhesives. The acidic priming/conditioning material simultaneously etches the enamel and dentin, dissolves the smear layer, and creates a polymer network leading to the formation of a hybrid layer (Frey, 2000; Lopes, Baratieri,

Caladeira de Andrada, & Vieira, 2002). Bonding to enamel is satisfactory but it is more difficult to attain a strong bond to dentin. There are two categories of sixth-generation bonding agents: type I self-etch systems, in which the material is applied in two steps, primer first followed by adhesive, and type II self-etch systems, in which the primer and adhesive are mixed before appli-cation (Ozer & Blatz, 2013).

Seventh GenerationThe etchant, primer, and adhesive are com-

bined in the seventh-generation bonding agent and the chemistry is consolidated into a single step. The system incorporates all of the sixth-generation characteristics but differs in that the material does not need to be mixed before appli-cation. The advantageous element to this bond-ing generation is that it simplifies the procedure for the dental practitioner.

One concern that has been presented for seventh-generation bonding agents is the effec-tiveness of a single-step bonding system. This can be especially problematic in sites where isolation may be limited. It has been reported that indeed salivary contamination signifi-cantly weakens the shear bond strength of this generation of bonding agent (Bhatia, Asrani, Banga, Jain, & Rawlani, 2015). As a result, the dental practitioner must perform careful isolation if this generation of bonding agent is being used.

Because of the availability of self-etching bonding materials, current bonding systems are typically referred to as total-etch bonding and self-etch bonding. The former can be divided into two categories: multiple-bottle adhesives and single-bottle adhesives. Self-etch bond-ing systems likewise fall into two categories: multiple step and single step, with single-step adhesives further divided into mix and no-mix systems.


CASE SCENARIO: THE “HOMETOWN” DENTIST

Dr. Smith is a young dentist who has decided to return to his hometown to practice with

his childhood dentist, Dr. Payne. Dr. Smith, in an attempt to learn more about Dr. Payne’s office, inquires about his protocol for com-posite restorations. Dr. Payne tells Dr. Smith that he uses a restorative material and bond-ing agent that was introduced many years ago because of his familiarity with the company. Dr. Smith advises Dr. Payne that he is not familiar with these materials but will do some research on their use. After this conversation with Dr. Payne, Dr. Smith takes a closer look at the directions on the bonding agent and recognizes that the bond strength is 2 MPa. Additionally, he looks at the expiration date on the box and rec-ognizes that the material has expired. Dr. Smith goes back to his notes from dental school and recognizes that he was trained using a seventh-generation bonding system.

Questions1. Should Dr. Smith be concerned about the

bonding agent available in this practice?

2. What is the clinical implication of this discovery?

DiscussionWhenever a practitioner is entering a clinical

environment, it is extremely important to take a close look at the materials utilized in the prac-tice. As Dr. Smith discovered, there is an expira-tion date on many dental materials. This date is important because the chemistry used in modern dental materials degrades over time if unused. Utilization of an expired dental material would not be advisable; it may result in unexpected handling properties and incomplete curing, and ultimately translate to clinical failure.

In the situation described, Dr. Smith also discovered from the directions in the material that the expected bond strength of the unex-pired material was 2 MPa. This bond strength would be expected in a first-generation bonding material. Most dental schools are using bond-ing agents that are beyond first generation. It is important to identify the bond strength because it will affect where the bonding material may be used in the oral cavity. With a first-generation bonding material, it would not be advisable to place this material on an occlusal of a posterior tooth because the bond will likely fail. This gen-eration of bonding agent was recommended in non-load-bearing surfaces of teeth such as class III or V restorations. Dr. Smith should be aware that if he is intending to place composite resto-rations in other sites, a different bonding agent must be selected.

Additionally, Dr. Smith should recognize that the preparation for a restoration with this generation of bonding agent would be dissimi-lar to preparations for restorations with later-generation bonding agents. Retention form is important in retaining the composite restoration because the bond strength is only 2 MPa. The utilization of a less-extensive preparation would require a later generation of bonding agent. Ultimately Dr. Smith should discuss his con-cerns regarding material choice with Dr. Payne. Greater familiarity with available materials and restoration preparation requirements will allow for greater potential restorative success for the practice’s patient population.

Finally, each generation of bonding agent has a different protocol for use. Each progres-sive generation of bonding agent generally has fewer steps; however, it is important to follow the recommended steps exactly to obtain pre-dictable outcomes. Dr. Smith’s familiarity with this generation of bonding agent is extremely


limited and as a result he would need to study its use before using the material in clinic.

There are multiple considerations when intro-ducing new materials into the clinical workflow. The practitioner is ultimately responsible for verifying a material’s correct and appropriate application, its suitability for clinical application, and the predictable clinical outcome of its use.

CONSIDERATIONS IN ADHESIVE RESTORATIVE

DENTISTRY

Modern adhesive dentistry provides numer-ous advantages for the clinician, including

convenience, durability, esthetics, and conserva-tion of hard tissue. Enamel and dentin bonding systems permit conservative preparations; how-ever, there are still areas of continued contro-versy with this treatment modality (Cardoso et al., 2011).

The evolving concepts of adhesive dentistry have focused largely on traditional cavity prepa-rations using a standard high-speed handpiece and bur despite periodic interest in alternate preparation methods, notably air abrasion and laser technology. Regardless of the preparative technique, surface topography may be central to the success of dentin conditioning agents and paramount to the success of enamel bonding agents. However, with modern adhesive tech-nology, it has been suggested that bur speed and type may not be an influential factor in inter-facial gap formation between the resin restora-tion and the tooth surface (Sherawat, Tewari, Duhan, Gupta, & Singla, 2014).

Arguably, one of the most important aspects of any restoration is the marginal seal at the restoration-dentin interface. Loss of marginal integrity, often manifested as leakage, has been reported as a primary cause of secondary caries,

postoperative sensitivity, and staining, ultimately leading to clinical failure. Obviously, reducing or eliminating leakage around restorations is an important clinical parameter for evaluation and has been used in clinical studies to evaluate both amalgam and composite restorations (Dennison & Sarrett, 2012; Moncada et al., 2015).

Leakage (i.e., the passage of bacteria, oral fluids, and ions between the cavity wall and the restoration) is critically important because of its clinical sequelae. Efforts to minimize/eliminate leakage have clinical and esthetic value and prompt continuing evolution of bond-ing technology, but in vitro prediction of the clinical performance of a restoration is, at best, difficult. Leakage studies traditionally use pen-etration tests to characterize the extent and loca-tion of leakage and use dyes, radioisotopes, or silver nitrate as the penetrating material. Silver nitrate staining is popular in leakage studies and is widely accepted for its efficacy as a test regimen (Soliman et al., 2016). Penetration tests effectively indicate the location and extent of leakage around a restoration, essentially pro-viding a “snapshot” of the leakage at a given point of time, but they require specimens to be sectioned in order to evaluate leakage. In con-trast, an electrochemical approach to recording leakage is a dynamic test method that provides a continuous evaluation of leakage within a given specimen throughout the entire testing period. These tests have been used both in coronal restorations and in the evaluation of root canal obturation techniques (Keles et al., 2014).

Besides marginal integrity and leakage, bond strength is another characteristic often studied by in vitro methods. Ideally, restorative materi-als would both minimize/prevent leakage and exhibit high bond strength, but despite exten-sive research into these two issues, their inter-relationship has not been fully explained in the literature. Logic suggests an inverse relationship


between leakage and bond strength. Although there has not been direct evidence to demon-strate this relationship, the current literature and indirect evidence suggest a clinical association (Ferracane & Hilton, 2016).

SUMMARY

The utilization and evolution of dentin bond-ing systems has changed the way that

restorative dentistry is practiced. It is the respon-sibility of the dental practitioner to have a full understanding of the risks and benefits, as well as the technical intricacies, of each system. The literature indicates that a number of interacting factors influence leakage behavior. Although the selection of dentin bonding agent is an impor-tant factor, the location and technical skill of the practitioner also play an important role. As additional restorative products are introduced into the marketplace, it will be a continuing challenge to understand the clinical benefits and pitfalls of these new and changing materials.

E X A M Q U E S T I O N SBONDING SYSTEMS FOR DENTIN

IN ADHESIVE DENTISTRYQuestions 1–20

Note: Choose the one option that BEST answers each question.

1. Which of the following is a principle of an ideal bonding system?

a. Bond flexibility

b. Ease of color match

c. Absence of microleakage

d. Low thermal conductivity

2. According to Table 1, to ensure optimal interface bonding, the adhesive must

a. have air entrapment.

b. have a dry bonding surface.

c. resist spreading.

d. have a low contact angle.

3. What is the primary component of enamel?

a. Water

b. Organic matrix

c. Collagen

d. Carbonated apatite

4. The organic phase of dentin is almost exclusively by weight composed of

a. water.

b. nerve tissue.

c. type I collagen.

d. carbonated apatite.

5. Which of the following statements is correct regarding dentinal tubules?

a. The shorter tubules are located near the pulp.

b. The tubules are filled exclusively with air.

c. Dentinal permeability is central to the aerodynamic theory of dentin sensitivity.

d. Primary tubules run laterally and connect the secondary tubules.

6. What is used to remove the smear layer created during cavity preparation?

a. Rigorously brushing

b. Rinsing with alcohol

c. Acid etching

d. Drying thoroughly

7. Bonding to dentin is challenging because it

a. is a static tissue.

b. is difficult to clean.

c. does not contain any moisture content.

d. is variable in structure and permeability.

9 continued on next page


8. Altering the smear layer before applying adhesives will

a. occlude dentinal tubules.

b. ensure resistance to fluid flow.

c. increase bond strengths.

d. make the substrate more alkalynic in nature.

9. The term for the transition zone located between mineralized dentin and an applied resin is the

a. smear zone.

b. fusion zone.

c. hybrid layer.

d. fused layer.

10. Dentin must be kept moist until it is treated with a hydrophilic primer to prevent the

a. collapse of collagen fibers.

b. formation of a hybrid layer.

c. demineralization of dentin.

d. separation of resin from the hybrid layer.

11. The first generation of dentin bonding agents

a. exhibited weak chemical bonds.

b. were intended for use in all classes of restorations.

c. contributed to low rates of postoperative sensitivity.

d. reduced hydrolysis of phosphate-hydroxyapatite bonds.

12. The second generation of bonding agents was characterized by the addition of components designed to

a. alter the dentin surface before resin application.

b. increase the bond strength to 15 to 20 MPa.

c. reduce hydrolysis of phosphate-hydroxyapatite bonds.

d. significantly reduce postoperative sensitivity in posterior restorations.

13. The third generation of dentin bonding agents

a. introduced a moist dentinal bonding technique.

b. created dental bonding through hybridization.

c. added a priming solution to modify dentin.

d. increased bond strengths up to 15 to 20 MPa.

14. The fourth generation of bonding systems was characterized by the use of

a. an acetone-based primer combined with a “total etch.”

b. components designed to reduce hydrolysis of phosphate-hydroxyapatite bonds.

c. separate “priming” and/or “conditioning” solutions.

d. an adhesive solution containing N-phenylglycine and glycidyl methacrylate.


15. Fifth-generation bonding systems were designed to

a. increase the reliability of fourth-generation systems.

b. eliminate the need for multiple steps.

c. contain a hydrophobic monomer urethane dimethacrylate.

d. facilitate micromechanical bonding.

16. Self-etch systems combined the etching and priming steps to reduce working time by eliminating the rinse step and lessening the possibility of the collapse of collagen because of

a. the smear layer.

b. marginal stress.

c. overdrying.

d. acidity.

17. What category of sixth-generation self-etch bonding system is applied in two steps?

a. Type I

b. Type II

c. Type III

d. Type IV

18. How are the etchant, primer, and adhesive applied in seventh-generation bonding systems?

a. Each is applied individually in three separate steps.

b. Etchant and primer are mixed together and applied prior to adhesive.

c. Etchant is applied, followed by a mixture of primer and adhesive.

d. Etchant, primer, and adhesive are applied in a single step.

19. Maintaining a strong seal at the restoration-dentin interface may help reduce the

a. disintegration of the smear layer.

b. development of secondary caries.

c. creation of the hybrid layer.

d. possibility of collagen collapse.

20. Which test is popular in studies that characterize the extent and location of leakage?

a. Acid-etch test

b. Penetration test

c. Smear test

d. Isolation test

This concludes the final examination.Please answer the evaluation questions found on page v of this course book.

R E F E R E N C E S

Bertassoni, L. E., Orgel, J. P., Antipova, O., & Swain, M. V. (2012). The dentin organic matrix – Limitations of restorative dentistry hidden on the nanometer scale. Acta Bio-materialia, 8(7), 2419-2433.

Bhatia, T. K., Asrani, H., Banga, H., Jain, A., & Rawlani, S. S. (2015). Influence of salivary contamination on the dentin bond strength of two different seventh generation adhe-sive systems: In vitro study. Journal of Con-servative Dentistry, 18(6), 467-470.

Buonocore, M. G. (1955). A simple method of increasing the adhesion of acrylic fill-ing materials to enamel surfaces. Journal of Dental Research, 34(6), 849-853.

Cardoso, M. V., de Almeida Neves, A., Mine, A., Coutinho, E., Van Landuyt, K., De Munck, J., & Van Meerbeek, B. (2011). Current aspects on bonding effectiveness and stability in adhesive dentistry. Australian Dental Journal, 56(Suppl 1), 31-44.

Chung, G., Jung, S. J., & Oh, S. B. (2013). Cellular and molecular mechanisms of den-tal nociception. Journal of Dental Research, 92(11), 948-955.

D’Arcangelo, C., Vanini, L., Casinelli, M., Frascaria, M., De Angelis, F., Vadini, M., & D’Amario, M. (2015). Adhesive cemen-tation of indirect composite inlays and onlays: A literature review. Compendium of Continuing Education in Dentistry, 36(8), 570-577; quiz 578.

Dennison, J. B., & Sarrett, D. C. (2012). Prediction and diagnosis of clinical out-comes affecting restoration margins. Journal of Oral Rehabilitation, 39(4), 301-318.

Duverger, O., Beniash, E., & Morasso, M. I. (2016). Keratins as components of the enamel organic matrix. Matrix Biology, 52-54, 260-265.

Dye, B., Li, X., Beltran-Aguilar, B. (2012). Selected oral health indicators in the United States, 2005-2008. NCHS Data Brief, 96. Retrieved from https://www.cdc.gov/nchs/data/databriefs/db96.pdf

Eliades, G. (1994). Clinical relevance of the for-mulation and testing of dentine bonding sys-tems. Journal of Dentistry, 22(2), 73-81.

Ferracane, J. L., & Hilton, T. J. (2016). Poly-merization stress – Is it clinically meaning-ful? Dental Materials, 32(1), 1-10.

Frassetto, A., Breschi, L., Turco, G., Marchesi, G., Di Lenarda, R., Tay, F. R., … Cadenaro, M. (2016). Mechanisms of degradation of the hybrid layer in adhesive dentistry and therapeutic agents to improve bond durabil-ity – A literature review. Dental Materials, 32(2), e41-e53.

Frey, O. (2000). Creating a reliable bond: An all in one system. American Journal of Dentistry, 13, 85D-87D.

Ikemura, K., Kadoma, Y., & Endo, T. (2011). A review of the developments of self-etching primers and adhesives – Effects of acidic adhesive monomers and polymerization ini-tiators on bonding to ground, smear layer-covered teeth. Dental Materials Journal, 30(6), 769-789.

13

References—14 Bonding Systems for Dentin in Adhesive Dentistry

Keles, A., Ahmetoglu, F., Ocak, M. S., Dayi, B., Bozkurt, A., & Orucoglu, H. (2014). Comparative analysis of three different filling techniques and the effects of exper-imental internal resorptive cavities on api-cal microleakage. European Journal of Dentistry, 8(1), 32-37.

Lopes, G. C., Baratieri, L. N., Caladeira de Andrada, M. A., & Vieira, L. C. C. (2002). Dental adhesion: Present state of the art and future perspectives. Quintessence Inter-national, 33(3), 213-224.

Malhotra, N., Mala, K., & Acharya, S. (2011). Resin-based composite as a direct esthetic restorative material. Compendium of Contin-uing Education in Dentistry, 32(5), 14-23.

Mason, P. N., Calabrese, M., & Graif, L. (1998). Modified extrusion shear bond strength of the new 3M adhesive (abstract 256). Journal of Dental Research, 77, 1239.

Moncada, G., Fernandez, E., Mena, K., Martin, J., Vildosola, P., De Oliveirar, O. B., Jr. … Gordan, V. V. (2015). Seal, replace-ment or monitoring amalgam restorations with occlusal marginal defects? Results of a 10-year clinical trial. Journal of Dentistry 43(11), 1371-1378.

Nawareg, M. M., Zidan, A. Z., Zhou, J., Chiba, A., Tagami, J., & Pashley, D. H. (2015). Adhesive sealing of dentin surfaces in vitro: A review. American Journal of Dentistry, 28(6), 321-332.

Ozer, F., & Blatz, M. B. (2013). Self-etch and etch-and-rinse adhesive systems in clini-cal dentistry. Compendium of Continuing Education in Dentistry, 34(1), 12-14, 16, 18.

Pashley, D. H., Pashley, E. L., Carvalho, R. M., & Tay, F. R. (2002). The effects of dentin permeability on restorative dentistry. Dental Clinics of North America, 46(2), 211-245.

Rosa, W. L., Piva, E., & Silva, A. F. (2015). Bond strength of universal adhesives: a sys-tematic review and meta-analysis. Journal of Dentistry, 43(7), 765-776.

Sherawat, S., Tewari, S., Duhan, J., Gupta, A., & Singla, R. (2014). Effect of rotary cutting instruments on the resin-tooth interfacial ultra structure: An in vivo study. Journal of Clinical and Experimental Dentistry, 6(5), e467-e473.

Sofan, E., Sofan, A., Palaia, G., Tenore, G., Romeo U., & Migliau, G. (2017). Classi-fication review of dental adhesive systems: From the IV generation to the universal type. Annali di Stomatologia (Roma), 8(1), 1-17.

Soliman, S., Preidl, R., Karl, S., Hofmann, N., Krastl, G., & Klaiber, B. (2016). Influence of cavity margin design and restorative mate-rial on marginal quality and seal of extended class II resin composite restorations in vitro. Journal of Adhesive Dentistry, 18(1), 7-16.

Tay, F. R., Gwinnett, A. J., Pang, K. M., & Wei, S. H. Y. (1994). Structural evidence of a sealed tissue interface with total etch wet bonding technique, in vivo. Journal of Dental Research, 73(2), 629-636.

Tjaderhane, L. (2015). Dentin bonding: Can we make it last? Operative Dentistry, 40(1), 4-18.

Van Meerbeek, B., Inokoshi, S., Braem, M., Lambrechts, P., & Vanherle, G. (1992). Morphological aspects of the resin-dentin interdiffusion zone with different dentin adhe-sive systems. Journal of Dental Research, 71(8), 1530-1540.

Van Meerbeek, B., Yoshihara, K., Yoshida, Y., Mine, A., De Munck, J., & Van Landuyt, K. L. (2011). State of the art of self-etch adhesives. Dental Materials, 27(1), 17-28.

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