From Volume 42, Issue 9, November 2015 | Pages 829-839
A large number of Class V restorations are placed per annum to restore cervical lesions. This paper evaluates the pathogenesis of these lesions, with particular reference to the role of occlusal factors, and reviews the literature in order to provide advice on the material(s) which are most likely to produce optimal longevity of a Class V restoration.
The Class V cavity constitutes a considerable burden of treatment for the general dental practitioner, with the most recent available figures in England and Wales indicating that more of these are placed than Class I restorations (circa 1.5million vs 1.4 million in the year 2004–2005),1 although these data do not differentiate between non-carious cervical lesions (NCCL) and restorations placed because of root caries. However, worldwide, the prevalence of NCCL has been estimated to vary from 5–85% of the population,2 while the review by Pecie and colleagues3 found a prevalence ranging from 11–62%. The prevalence and severity also appears to increase with age. Despite this prevalence, these restorations do not appear to attract the attention or imagination of dentists worldwide, given the substantial volume of publications on Class I and II composites and the relative paucity of papers on Class V restorations.
It is therefore the aim of this paper to review the literature on Class V restorations with particular respect to which material performs optimally in these cavities.
Class V cavities may form:
An occlusally related pathogenesis has been proposed, with Grippo4 terming these lesions ‘abfractions’ from the Latin words for ‘breaking away’, in an attempt to explain the development of wedge-shaped lesions (Figure 2). The concept of tensile stresses in the aetiology of NCCL was first put forward by Lee and Eakle in 1984,5 with the theory being extended by Grippo4 in 1991 to include the concept of chemical or electrochemical degradation in the cervical area of affected teeth. Some engineering studies have supported the ‘abfraction theory’ by way of tensile stresses resulting from oblique occlusal forces causing the commencement of a lesion by disruption of bonds between hydroxyapatite crystals in the cervical area of teeth where the enamel is thin.6,7 One paper,8 in 1995, presented an SEM image purporting to demonstrate the initiation of an abfraction lesion by a small enamel fracture. Telles and co-workers9 examined 1,131 teeth in first year dental students, finding 129 NCCL, with 29 of the 40 students having at least one tooth with one lesion. After three years, the incidence of new lesions was 57, with the identification of new lesions associated with the presence of wear facets being statistically significant.
However, support for the ‘abfraction theory’ is generally lacking in systematic reviews:
In summary, therefore, support for a relationship between occlusal wear and NCCL development may be considered insufficient, in the view of the author, to support preventive intervention/treatment of NCCL lesions by occlusal adjustment.
Sensitivity, the presence of a carious lesion or poor aesthetics may result in a patient's request for treatment of a Class V lesion, but the dental practitioner may also consider restoration of such a lesion under the following circumstances:8
In addition, the American Academy of Operative Dentistry17 has suggested that, for lesions influenced by acidic dissolution, the reasons for the acid challenge should be assessed and the patient counselled, be it with regard to the consumption of fruit juice or other potentially erosive drinks (some sports drinks and herbal teas being implicated in some research). Furthermore, patients with conditions which result in gastric reflux should be counselled to seek medical attention. In other words, a first treatment goal should be the removal of the aetiological factors.17 It should also be noted that dentine is less resistant to acid attack and wear than enamel so that, when the dentine is exposed, the destruction of tooth substance will accelerate.
An alternative view has been proposed by Pecie and colleagues from the University of Geneva,3 namely that restoration should be postponed in the absence of aesthetic demands, sensitivity or a threat to the integrity of the tooth, given their consideration that the development of the NCCL is a slow process. They suggest preventive therapy, including risk assessment and prevention of development of NCCL by correcting habits and the early detection and management of incipient lesions. For patients presenting with NCCL, they suggest the use of a soft toothbrush and low abrasion fluoridated toothpaste and the avoidance of a toothpaste with a low pH. They also suggest the avoidance of toothbrushing after an acidic challenge and the use of adhesive systems to provide a dentine seal to be an effective strategy.
A number of restorative materials may be used for the restoration of Class V carious cavities or non-carious lesions. Fifty years ago, gold inlays were favoured for these cavities, formed by the taking of a wax pattern of the cavity, the investment of the pattern and the forming of the inlay by the lost wax process in a one visit technique (in the way that CAD CAM techniques can do today!). However, these restorations were not aesthetic in everyone's eyes! (Figure 3).
Today, with the advent of materials such as glass ionomer and its variants, which reliably adhere to tooth substance, the placement of Class V restorations is substantially simplified. Resin composite and its variants, such as flowable composites, are also appropriate, when used in conjunction with a dentine-bonding agent. The use of amalgam in Class V appears to be waning, but there are no data available which indicate the respective numbers of restorations placed in these materials.
Material specific properties for Class V restorations include:
Other properties, although not specific to Class V restorations, which could be considered appropriate include:
Amalgam may be used for Class V restoration, but its use is limited by the fact that it requires the provision of undercuts into the cavity, if these are not present as a result of caries removal, ie it is unlikely to fulfil the ideals of minimally invasive dentistry. It is also unaesthetic.
Glass ionomer (GI) and its variants possess the ideal property of adhesion to tooth substance by way of the chemical reaction between the polyacrylic acid constituent of the material and the calcium of the hard dental tissues.18 All glass ionomer materials release fluoride as a result of their acid-base setting reaction but, while this may be considered to be a beneficial property, this fluoride release has little or no effect on cariostasis in vivo.19 Conventional glass ionomers tend to be opaque and thereby unaesthetic (Figure 4), but have the low modulus considered appropriate for restoration of cavities in the cervical region. Resin-modified GIs (RMGIs) were developed by the incorporation of a resin into the glass ionomer matrix: this decreases the solubility of the material, improves its adherence to tooth tissue, improves its fluoride release and results in a material which is more aesthetic and which can be finished and polished immediately following placement, providing potentially reasonable aesthetics (Figure 5).18 For these reasons, RMGIs are therefore the glass ionomer of choice for the restoration of Class V cavities and non-carious cervical lesions.
Resin composite materials, other than those developed for use as self-adhesive resin luting materials,20 do not have any innate bond to tooth structure, so an intermediate dentine/enamel bonding agent must be employed. These are the most aesthetic materials available for use in Class V restorations (Figure 6). Several variants are available, with the less heavily-filled flowable variants being particularly favoured in Class V cavities. Initially, these materials were considered to have a modulus of elasticity close to dentine, but it is now apparent that their modulus is simply closer to that of tooth structure, as opposed to close.21
Flowable composites, which were introduced in 1995, are less heavily filled (45–60%) variants of conventional hybrid resin composite materials. Early materials had low viscosity, high polymerization shrinkage, low wear resistance, but, today, companies have added other components (resins, different filler types and amounts) in an effort to reduce polymerization shrinkage. These materials, which are often available in a wide variety of shades, are presented in syringe format, so are designed to flow into crevices or line angles without creating air voids. The material spreads or flows rather than staying in one place or shape, being ‘puddled’ into position. In this regard, a recently introduced composite, Sonic Fil (Kerr Mfg Co, Orange, CA, USA) may be of value in the restoration of Class V cavities. This uses sonic energy via a specially designed handpiece, in order to reduce the viscosity of the composite when it is being applied to the cavity, with the material becoming more viscous when the sonic energy is stopped.
With flowable composites, there is a delicate balance between polymerization shrinkage and modulus of elasticity. Being less heavily filled, it would be expected that their shrinkage will be greater than more heavily filled conventional composite materials. However, being less heavily filled, flowable composites will have a lower modulus of elasticity, ie increased flexibility, which could be perceived as an advantage, given that teeth are considered to flex, with the cervical region being the fulcrum.
The literature was reviewed, by way of a Medline search, in order to determine the optimum material(s) for restoring Class V lesions. Papers included were:
Furthermore, it was considered that papers from the ‘real world’ of general dental practice were ideal, given that this is where the majority of treatment, worldwide, is carried out. However, only one paper from this arena was identified, that from Stewardson et al22 (vide infra). The studies identified in the Medline search are summarized below:
As reported in other studies, there was wide variation within the same generic type of adhesives, with 78% of Permagen-retained restorations being lost over 13 years, compared with 41% of Optibond-retained restorations. This compared with a loss of 36% of Vitremer RMGI restorations after 13 years.
The five-year survival of the different materials is presented in Table 1.
| RMGI | 79% |
| Amalgam | 75% |
| Flowable Composite | 69% |
| Composite | 68% |
| Compomer | 71% |
| Conventional Glass Ionomer | 51% |
When interpreting these results, all materials were associated with a longer time to restoration failure than conventional glass ionomer, with RMGI performing optimally. There was also a significant relationship between whether the Class V cavity was carious or non-carious, with the follow-up comparisons indicating that more of the carious cavities had been filled with amalgam or RMGI or other materials. When the data were further separated, the time to failure of GI restorations was shorter than for other materials, with the log-rank tests indicating that this was only significant for carious cavities, and not for non-carious. There was no association with regard to carious cavities being prepared with a bur, but only 18 were so treated. However, with non-carious cavities, the time to failure for restorations in which the cavity was not prepared with a bur was significantly reduced compared with those which had been prepared. The results of this particular study concur with others of similar duration by Loguercio and co-workers31 and Franco et al,32 both of which demonstrated superior performance of RMGI (when compared with other tooth-coloured restorative materials) in NCCL.
Finally, with regard to the role of occlusal factors in the aetiology and restoration of NCCLs, the study by Stewardson et al22 did not identify an influence of any occlusal factors on time to restoration failure.
This paper evaluated the survival rate of a variety of materials used to restore Class V carious and non-carious cavities. The lack of homogeneity among the papers included in the present work makes drawing conclusions difficult, in particular because of the variety of criteria used to place or replace Class V cavities. However, it could be argued that this is what clinical dental practice is all about, with practitioners from differing undergraduate and postgraduate backgrounds providing a wealth of data.
The information presented here may therefore be considered to be robust, with a number of common themes emerging, namely, that RMGI materials provide the best AFRs in a number of studies and reviews and could therefore be recommended as the material of choice, other than in situations where the superior aesthetics of resin composite (flowable or other) is indicated.
There is evidence from the study by Heintze et al23 that this is a good clinical practice, with the study by Stewardson and colleagues22 supporting this. Van Dijken27 has discussed this, considering that, in contrast to the creation of a smear layer during cavity preparation, the cervical lesion is not normally covered by a smear layer, and that roughening with a round diamond prior to the adhesive restoration will create a smear layer similar to that found in drilled cavities. In his 8-year study,27 there was better clinical retention in the slightly roughened cavities. In addition, the removal of the outer surface of sclerotic dentine by roughening with a diamond has been suggested in order to create a hybrid layer similar to young dentine.33 While removal of a hyper-mineralized sclerotic dentine surface using phosphoric or stronger acids has been discussed, this may be considered to have the potential to result in post-operative sensitivity. Accordingly, removal of the surface layer of sclerotic dentine has also been recommended by Tay and Pashley,34 since clinicians have no way of discerning the actual morphology of the NCCL surface. Finally, the review by Heintze et al23 provides additional information regarding the benefit of roughening the dentine surface, given that they identified that retention and marginal discoloration was significantly less in those restorations whose surface was prepared with a diamond but prior to placement of the adhesive.
The perceived wisdom, in the past, was that it should, insofar that this would increase the surface area of contact between restorative and tooth. However, the review by Heintze et al23 did not identify any clinical improvement when the coronal enamel was bevelled. This is confirmed by the work of Da Costa and colleagues35 and a very recent systematic review/meta-analysis by Schroeder et al.36
The review by Heintze et al23 identified the 2-step self-etching adhesive systems as performing better than the 3-step etch and rinse systems, followed by the glass ionomer cements and RMGIs, with the worst performance in the 1-step self-etching group. In their 13 year evaluation, Van Dijken and Pallesen26 commented that all the systems that they tested showed a continuous degradation of bond, but with an RMGI performing optimally and a 3-bottle dentine bonding system (Optibond) performing best in that group of materials while, in a separate study, Van Dijken and collagues28 identified Clearfil Liner Bond as performing optimally. In the systematic review by Peumans and colleagues,25 their results indicated the lowest mean AFR scores for glass ionomer, followed by two-step self-etch adhesives, three-step etch and rinse systems, and significantly higher AFR scores were recorded for one-step self-etch systems.
The heterogeneity of the data makes it difficult to present one resin-based bonding agent as being superior in a variety of studies, with Chee et al24 identifying variation among adhesives with the same bonding strategy – is this due to variations in composition and/or manufacturer, perhaps? However, it appears that 2-step self-etching adhesive systems, such as Clearfil SE, have been found to perform optimally, followed by the 3-step etch and rinse materials, with the variants of Clearfil (Clearfil SE and Clearfil LinerBond) being mentioned as performing well in several studies, as well as the 3-bottle versions of Optibond. However, the field of dentine bonding is fast moving, with the latest variants, the Universal Bonding agents, appearing to hold promise. However, it might not be a coincidence that many of these new materials contain the monomer 10-MDP, which is a constituent of the Clearfil group of bonding agents.
Finally, placement of Class V restorations may be facilitated when less viscous materials, such as flowable composites, are replaced by the use of specially designed matrices, an example of which is illustrated in Figure 7. Furthermore, in order to maximize the effectiveness of restorations, as well as choosing the right generic type, as this article has attempted to elucidate, clinicians should use materials which have a good research pedigree, something which so-called ‘own label’ materials do not have.37,38
Which material and clinical technique performs best? From this review, it may be concluded that:
