Successful Posterior Composites

Chapter 1

Posterior Composites: The State of Play

NHF Wilson and CD Lynch

Aim

New knowledge and understanding, and the commercial development of composite resin materials and associated bonding technologies, mean that the placement of composite resin in occlusal and all but the largest occlusoproximal cavities may, given appropriate technique, be considered predictable and effective. The aim of this chapter is to describe state-of-the-art approaches to the placement of posterior composites.

Outcome

After reading this chapter, the reader will understand how new knowledge and understanding and developments in the field of composite resin materials and bonding technologies have resulted in the predictable and effective placement of load-bearing composite restorations in posterior cavities.

Introduction

Attitudes to the placement of posterior composites have undergone significant changes in recent years. As recently as the late 1990s, guidance on the placement of composite resins in posterior teeth restricted the application to "small occlusal and occlusoproximal cavities in premolar teeth, and preferably in those with limited occlusal function". Educational surveys from that time demonstrated that most dental school graduates in Europe and North America had limited teaching in the placement of posterior composites, with many new dentists graduating with little or no clinical experience in their placement.

As a consequence of increased dental awareness in society, coupled with improvements in dietary and oral hygiene practices, many more patients, particularly younger patients, are now presenting with fewer and smaller lesions of caries than in the past (Figs 1-1 and 1-2). Such patients expect minimally interventive procedures, preferably using techniques that are described as "aesthetic" or "tooth coloured" (Fig 1-3). This, in association with commercial developments in composite resin materials and associated bonding technologies and lingering concerns over the safety of dental amalgam, has driven an increase in the placement of posterior composite restorations in general dental practice. For example, a survey of United Kingdom general dental practitioners in 2001 revealed, far from limiting the placement of composite to small cavities in premolar teeth, that almost one-half of general dental practitioners placed composite resin restorations in load-bearing cavities in molar teeth (Figs 1-4 to 1-6).

Fig 1-1 Mandibular dentition from a 30-year-old female, which is unrestored and caries free, albeit with some staining of occlusal fissures.

Fig 1-2 Bitewing radiograph from a healthy 35-year-old female demonstrating an absence of caries or restorations.

Fig 1-3 A recently placed composite restoration in the occlusal surface of a mandibular first molar.

Fig 1-4 A posterior composite restoration that has been in clinical service for over eight years.

Fig 1-5 The composite restorations in the maxillary premolars have been in clinical service for over 10 years. While there is some evidence of marginal staining, the restorations are serviceable. This is in contrast to the deteriorating dental amalgam restoration in the maxillary first molar.

Fig 1-6 An extensive posterior composite restoration in a root-filled maxillary first molar. This restoration has been in service for more than six years.

With ever increasing patient expectations, coupled with improvements in the physical properties of composite resin materials and bonding technologies, it is highly likely that the placement of composite resins in posterior teeth will continue to increase in clinical practice.

Are posterior composites effective?

The answer as to whether posterior composites are effective is a resounding "yes". While some studies, dating back to the 1990s, found that the longevity of posterior composites was not as favourable as that of dental amalgam restorations, these studies investigated the use of composite resins as a substitute rather than an alternative to the use of dental amalgam. More recent studies indicate that the survival of posterior composite restorations can match, or even exceed, that of restorations of dental amalgam if they are applied to the best possible advantage. Indeed, dental insurance claims data in North America indicate that the longevity of posterior composites placed in general practice has matched and even surpassed that of dental amalgams. This has also been seen in recent studies of posterior restorations placed in general dental practice in Europe. Furthermore, as our understanding of the science of composite resins and bonding technologies increases, and practitioners become all the more familiar with the techniques necessary to place good-quality resin composite restorations, the survival rates of posterior composites will improve further.

One of the keys to success when placing posterior composites is to recognise that they are an alternative to, rather than a substitute for, dental amalgam and, as such, require very different operative techniques to those appropriate for dental amalgam. Dental amalgam is the "old workhorse" of operative dentistry. It is considered to be a forgiving, relatively easy material to place. In contrast, composite resins require meticulous attention to moisture control, must be placed using an incremental placement technique and are dependent on an array of equipment and devices including light-curing units, sophisticated matrix systems and multicomponent finishing processes, let alone the effective use of an appropriate dental adhesive. Notwithstanding these complexities, and the associated additional costs, the use of composite resins offers distinct advantages in clinical service over dental amalgams for the restoration of teeth damaged by caries and other insults.

Why is Composite Resin Better than Dental Amalgam?

Some of the advantages of appropriately applied composite resins over dental amalgams include:

• a reduced need to remove sound tooth substance in preparation

• opportunity to retain the restoration in non-retentive preparations through adhesive bonding to the remaining tooth tissues

• an aesthetic tooth-coloured appearance (Fig 1-7)

• reinforcement of the remaining tooth structure

• increased fracture resistance of the restored tooth unit (Fig 1-8)

• opportunity to repair and refurbish restorations in clinical service, thereby reducing the need for the total replacement of failing restorations (Fig 1-9).

Fig 1-7 While these dental amalgam restorations are clinically acceptable, they lack the aesthetics increasingly expected by patients.

Fig 1-8 Fractured tooth tissue adjacent to an extensive dental amalgam restoration in a mandibular first molar.

Fig 1-9 A repaired posterior composite restoration in a mandibular first molar; fracture of the distolingual cusp had occurred, and the area repaired with resin composite. A lighter shade of composite was selected to permit discrimination of underlying tooth tissue should further operative intervention be required.

Countering these advantages, there is evidence that posterior composites may be more susceptible to secondary caries than dental amalgams in cariogenic environments. Additionally, as and when total restoration replacement is indicated, dental amalgam, unlike most posterior composites, may be readily distinguished from remaining tooth tissue, thus limiting the risk of inadvertent removal of sound tooth tissue. As will be discussed later in this book, there are ways and means to minimise the effects of these limitations.

The Way Forward

For many practitioners, there is a growing ethical problem. Is it in the patient's best interests to sacrifice sound tooth tissue to enable the effective application of dental amalgam, the tried and tested approach of 20th century operative dentistry, when it is possible to adopt minimally interventive preparation techniques through the use of a tooth-coloured alternative? It is suggested, as is now taught in many dental schools, that an adhesively bonded composite resin should be used to restore all but the largest initial lesion of caries, with particular...