The Progression of Dental Adhesives

A Peer-Reviewed Publication

Written by Ara Nazarian, DDS

www.ineedce.com

Educational Objectives

Upon completion of this course, the clinician will be able

to do the following:

1. Be knowledgeable about the evolution of

bonding adhesives

2. Know the attributes of an ideal bonding agent

3. Be knowledgeable about the properties of the

seventh-generation adhesives and the advantages

they offer

4. Know the applications that seventh-generation adhe

-

sives can be used for and understand the techniques

that should be used

Abstract

There has been dramatic progression in the adhesion of

dental adhesives and resins to enamel and dentin in the 40

years since Buonocore

introduced the technique of etching

enamel with phosphoric acid to improve adhesion to enamel.

The first dental adhesives bonded resins to enamel only,

with little or no dentin adhesion. Subsequent generations

have dramatically improved bond strength to dentin and

the sealing of dentin margins while retaining a strong bond

to enamel. With more patients demanding metal-free den

-

tistry, the use of dental resins as cements as well as direct and

indirect restorations will continue to increase. This article

discusses the progression of dental adhesives up to the most

recent generation, in which all components are contained

in a single bottle or unit-dose container and applied using a

one-step technique that requires no mixing.

Overview

Over the past 45 years, dental bonding systems have evolved

with variations in chemistry, application, mechanism, tech

-

nique, and effectiveness. This evolution accompanied the

development of improved esthetic dental materials, notably

composite resin and ceramic, and an increasing demand by

patients for esthetic dentistry. In 1999, approximately 86

million direct resin restorations were placed. With respect

to indirect restorations, approximately 2.5 million veneers,

38 million resin/ceramic crowns, and 1.1 million ceramic/

porcelain inlays were placed, in addition to metal-based

crowns and bridges and core/post and core build-ups.

All direct resin restorations require bonding, and indirect

restorations either require or are candidates for bonding. As

the demand for bonded esthetic restorations has continued

to increase, the evolution of bonding agents has accelerated.

Let us quickly review dental adhesives according to a series

of generations, allowing us to understand the characteristics

of each group.

All direct resin restorations

require bonding

History of Bonding Agents

First and Second Generation

The first- and second-generation bonding agents used

during the 1960s and 1970s did not recommend etching

the dentin, but instead relied on adhesion to the attached

smear layer.

The weak bond strength (2MPa–6MPa) to

the smear layer still allowed dentin leakage with clinical

margin stain.

Third Generation

The third-generation systems of the 1980s introduced

acid etching of dentin and a separate primer designed to

penetrate the dentin tubules as a method to increase bond

strength.

These systems increased bond strength to dentin

(12MPa–15MPa) and decreased dentin margin failure. With

time, however, margin staining caused clinical failure.

Fourth Generation

The fourth-generation adhesive systems of the early 1990s

used chemistry that penetrated both etched and decalcified

dentin tubules and dentin substrate, forming a “hybrid”

layer of collagen and resin. Fusayama

and Nakabayashi

described the penetration of resin into dentin as giving high

bond strengths and a dentin seal. In fact, Kanca

introduced

the idea of “wet bonding” with these systems. Products in

this category include All-Bond

®

2 (Bisco), OptiBond

®

FL

(Kerr), and Adper™ Scotchbond™ Multipurpose (3M

ESPE). These bonding agent systems have the longest track

record as far as research goes and they perform well clinical

-

ly. In fact, OptiBond FL, an 18-year-old product, received

the Product of the Year award from

Reality

magazine.

Bond

strengths for these adhesives were in the low- to mid-20MPa

range and significantly reduced margin leakage compared to

earlier systems.

This system was very technique sensitive

and required an exacting technique of controlled etching

with acid on enamel and dentin, followed by two or more

components on both enamel and dentin. Because of the

complexity of multiple bottles and steps, dentists began

requesting a simplified adhesive system.

Date: 2015-02-03; view: 1707