Placement, replacement and longevity of composite resin-based restorations in permanent teeth in Greece

Abstract

Objectives: The aims of the present study were to assess the reasons for the placement and replacement of resin-based composite (RBC) restorations in permanent teeth and to establish the longevity of replaced restorations. Methods: The study population consisted of 2,480 individuals attending a private practice. Clinical examination involved the evaluation of the numbers of decayed teeth (primary caries) and failed restorations, respectively, and the reasons for the placement and replacement of RBC restorations. In addition, possible associations between the placement and replacement of restorations and type of cavity, and the reasons for the placement and replacement of RBC restorations by tooth type were assessed. Statistical analysis was accomplished using the chi-squared test. Results: A total of 3,528 restorations were identified; 2,046 (58%) of these were first-time restorations and 1,482 (42%) were replacement restorations. The main reason for first-time RBC restorations was primary caries (56%). Secondary caries was the most frequent reason for the replacement of RBC restorations (43%). Statistically significant differences were recorded between cavity type and first-time (P = 0.0083) and replacement (P = 0.0067) restorations. No statistically significant differences were observed between tooth type and the reasons for first-time (P = 0.067) or replacement (P = 0.073) RBC restorations. The median longevity of replaced restorations was approximately 4 years (39%). Conclusions: Primary and secondary dental caries were the principle reasons for first-time and replacement restorations, followed by tooth and restoration discolouration, respectively. Therefore, patients at high risk for developing caries may require more frequent dental care.

INTRODUCTION

The first resin-based composite (RBC) material was introduced as a Class II restorative in 1968; however, this soon failed for several reasons, including recurrent caries, excessive wear, tooth sensitivity, open contact areas, the fracture of the material and the discolouration of its surface¹. The clinical usage of the material, patient compliance and clinician decisions on the indications for the placement or replacement of a restoration are considered to be the main factors that determine the longevity or failure of a restoration². Nowadays, RBC materials are regarded as the materials of choice for conservative aesthetic restorations (for Class I–V carious lesions, mainly) and in traumatic injuries. Previous studies3., 4., 5., 6., 7., 8., 9., 10., 11., 12. have implicated primary caries as the principal reason for the placement of a restoration and secondary caries as the most frequent reason for the replacement of a restoration, followed by tooth discolouration and marginal fracture6., 7., 8., 9., 10., 11., 12., 13., 14., 15., 16., 17., 18., 19., 20.. Similar studies have identified several reasons for the replacement of a composite restoration, such as tooth fracture, the marginal staining of a tooth, fracture and marginal defects, deficient anatomical form and the over-contouring of a restoration7., 8., 11., 13., 15., 17., 19., 20., 21., 22.. Mjør²³ reported that secondary caries and poor marginal adaptation were the most common reasons for the failure of RBC restorations and mentioned that the failure of restorations was a major problem in dental practice as replacements comprise about 60% of all operative work. Brukiene et al.²⁴ reported that in many cases the failure of a composite restoration depends not only on the material itself, but also on its proper handling. According to Qvist et al.²⁵, the reasons for the replacement of composite restorations vary depending on the restorative material, the dentition and the age of the patient.

The aims of the present study were: (i) to assess the reasons for the placement and replacement of RBC restorations and to evaluate the longevity of replaced restorations; (ii) to estimate the associations of first-time and replacement RBC restorations, respectively, with type of cavity, and (iii) to evaluate the reasons for first-time and replacement RBC restorations, respectively, by tooth type.

METHODS

Subjects

A total of 2,480 subjects (1,170 men, 1,310 women) aged 18–58 years (mean age: 36.7 ± 5.4 years) attending a private practice in Patra, one of the biggest cities in Greece, were included as participants in the present study.

The reasons for the placement and replacement of RBC restorations in the sample over a period of 3 years (January 2008 to December 2010) were recorded. Data included the type of cavity (according to Black’s system of classification), the location and type of restored teeth and the longevity of replaced restorations; data were sourced from responses to self-report questionnaires on the age of failed composite restorations completed by participants. It is therefore not possible to calculate objectively the longevity of all replaced restorations. A comprehensive history was taken and all examinations were performed by the author in his private practice. A health-related questionnaire was used to establish that all participants were in good general health.

Ethical considerations

The present study was not experimental. Greek law requires only experimental studies to be reviewed and approved by an authorised committee (such as associated with a dental school, a Greek dental association or the Ministry of Health). Subjects who agreed to participate in the present study were informed about the evaluation to which they would be submitted and were asked to sign an informed consent form. Patients with diagnosed pathological conditions were advised to seek consultation and treatment.

Clinical examination

Clinical measurements in all participants were performed by the author of the present study. The majority of restorations in the study participants had been performed by the author’s colleagues at his practice.

A dental unit light was used as the light source for the inspections. The teeth and gingivae were dried with compressed air. Restored and non-restored teeth were examined carefully using an intra-oral mirror and an explorer.

The main indications for the placement of a restoration were those determined by the World Health Organization (WHO)²⁶ and focused on the clinical signs of primary caries and the presence of carious lesions (lesions with grooves, vents or crevices; lesions with smooth surfaces with soft substrates; lesions that appeared as grey areas; lesions that developed as visible cavities).

The main indications for the replacement of a restoration were those determined by the California Dental Association Quality Evaluation System²⁷ for use in the assessment of the quality of a dental restoration as follows: (i) surface quality and colour; (ii) anatomical form, and (iii) margin integrity.

Inclusion criteria

Selection criteria required participants to be aged ≥ 18 years and to have a minimum of 20 natural teeth because large numbers of missing teeth might have interfered with the results of the study. The absence of more than 12 teeth can cause problems in eating, speech and other basic activities that may worsen with time. Eventually, the remaining teeth in the jaw shift in an attempt to fill the gap left by a missing tooth. This can cause other oral diseases, including periodontal disease (pathologic migration, mobility), temporo-mandibular joint disorder, dental caries in the remaining teeth (primary caries) and dental caries in restored teeth (secondary caries)²⁸ and may lead the patient to decide to have the remaining teeth extracted although other treatments are available (e.g. fixed prosthodontics, partial dentures, fillings, etc.).

Choice of material

A proper RBC material (Filtek™ Z250; 3M ESPE Dental Products, Inc., St Paul, MN, USA) was used for first-time and replacement restorations of anterior teeth. The polymerisation of the material was performed using a halogen dental light cure unit (LK-G21; Zhengzhou Linker Trading Co. Ltd, Zhengzhou, China) (output power: 75 W; wavelength: 400–500 nm; light power: 800–1,000 mW/cm²; solidification time: 20 s; solidification depth: 2 mm).

This material is indicated for restorations of anterior and posterior teeth. However, it was considered unsuitable for restorations of posterior teeth because of its mechanical properties: it is relatively weak and should not be used in load-bearing areas, especially in extensive cavities. The ideal material in this context is Filtek™ P60 (3M ESPE Dental Products, Inc.).

Exclusion criteria

Only anterior teeth of the mandible and maxilla were included (posterior teeth were excluded for the reasons mentioned above). Restored and non-restored molars and premolars, third molars and amalgam-restored anterior teeth were excluded from the study.

Reproducibility

The intra-examiner consistency of clinical recordings was not estimated using the kappa index because the majority of first-time and replacement restorations had been performed by colleagues of the present author and because the reasons for the placement and replacement of restorations are more visible (according to the diagnostic criteria used) than other clinical parameters or measurements in which more objective evaluation may be necessary.

Statistical analysis

For each subject the numbers of decayed teeth (primary caries) and failed restorations (secondary caries) were calculated. The chi-squared test was employed to establish whether first-time and replacement restorations differed in terms of the type of tooth cavity (Classes I–III) and the reasons for the placement and replacement of restorations by tooth type. Statistical analysis was performed using spss Version 17.0 (SPSS, Inc., Chicago, IL, USA). A P-value of < 5% (P < 0.05) was considered to indicate statistical significance.

RESULTS

A total of 3,528 composite resin-based restorations were identified in the study sample, of which 1,552 (44%) were in men and 1,976 (56%) were in women; 2,046 (58%) were first-time restorations and 1,482 (42%) were replacement restorations.

Figure 1 shows the distributions of first-time and replacement composite restorations according to Black’s classification of cavity type. Most first-time (42%) and replacement (56%) restorations were placed in teeth with Class III cavities. Statistically significant differences were recorded between cavity type according to Black’s classification and first-time (P = 0.0083) and replacement (P = 0.0067) composite restorations.

Figure 1.

Distributions of first-time and replacement resin-based composite (RBC) restorations according to Black’s classification.

Reasons for first-time and replacement composite restorations are shown in Figure 2. Table 1 shows the reasons for first-time and replacement restorations by tooth type.

Figure 2.

Reasons for the placement and replacement of resin-based composite restorations.

Table 1.

Reasons for first-time and replacement resin-based composite restorations by tooth type

	Central incisors, %	Lateral incisors, %	Canines, %	Total, %
Reasons for first-time placement
Primary caries	68	62	38	56
Tooth discolouration	23	17	8	16
Tooth fracture	24	13	8	15
Dental erosion	17	13	9	13
Reasons for replacement
Secondary caries	54	47	28	43
Restoration discolouration	36	28	17	27
Loss of filling	27	16	11	18
Fracture of filling	17	12	7	12

No statistically significant differences were observed between tooth type and the reasons for first-time (P = 0.067) or replacement (P = 0.073) RBC restorations.

The longevity of replaced composite restorations was recorded for 1,482 defective restorations. The median longevity of a composite restoration was approximately 4 years (39%). Overall, 27% of composite restorations lasted for > 8 years, 16% of restorations were replaced at 4–8 years and 18% were replaced at < 1 year.

DISCUSSION

The findings of the present study show that primary caries was the principal reason for the placement of composite restorations. Data from previous studies have shown similar results3., 4., 5., 6., 7., 8., 9., 11.. Braga et al.¹⁰ and Frost¹² observed that primary caries and non-carious tooth substance loss (i.e. erosion) were the main reasons for the placement of initial restorations.

The principal reason for the replacement of restorations was secondary caries, a finding that is in accordance with those of previous studies10., 12.. In addition, the discolouration of a restoration was another important reason for replacement. This finding was also recorded in previous studies6., 7., 8., 9., 13., 14., 15., 16., 17..

The high incidence of secondary caries associated with composite restorations may be explained on the basis of microbiological findings²⁹. It is important to emphasise that the ultimate clinical outcome is highly influenced by the patient’s oral hygiene practice. Composite materials accelerate the growth of Streptococcus mutans, which, in combination with poor oral hygiene practice, may cause secondary caries³⁰. A significantly higher proportion of S. mutans was found at the cavity margins of composite restorations than at those of restorations performed using amalgam and glass-ionomer material⁵.

A study by Friedl et al.³¹ revealed that more dental plaque was found at the interface between the composite material and the tooth than at the amalgam–tooth interface. In addition, findings from previous studies indicate that resin-based materials accumulate more dental plaque and the composite of this plaque is more cariogenic than that seen on amalgam, silicate cement and glass-ionomer materials29., 31..

Other factors that have been associated with the development of secondary caries are microleakage³² and the shrinkage of composites during the curing period. Consequently, it is important to minimise the effect of composite shrinkage by following the instructions for the use of the material³³.

Discolouration as a reason for the replacement of composite restorations remains a significant problem for both the clinician and the patient. Mjør and Toffenetti¹⁵ observed that margin discolouration suggests inadequate acid-etching of the enamel prior to placing the bond agent, inadequate handling of the material (placing, concentration, adaptation) and the problems associated with polymerisation shrinkage. The increase in the etched surface area results in a stronger enamel–resin bond, which increases the retention of the restoration and reduces marginal microleakage and marginal discolouration³⁴.

Previous studies indicated that the main reasons for replacing composite restorations were marginal discolouration, marginal fracture and degradation7., 16., 35., tooth fracture7., 11., 13., 15., 17., 19., 20., restoration fracture, marginal infiltration, deficient anatomical form and the over-contouring of a restoration21., 22.. Vehkalahti and Palotie³⁶ observed that secondary caries, fractures, overhangs and marginal discrepancy were the most common reasons for replacing restorations. According to a study by Al-Negrish⁸, root canal treatment is another important reason for replacement.

It is important to stress that the reasons for replacement vary depending on the restorative material (in many cases the failure of a restoration depends not only on the material itself, but also on the proper handling of the material²⁴), the dentition and the age of the patient²⁵.

The differences described in the earlier studies cited here may be attributed to the heterogeneous population samples examined, the progression of dental caries and the restorative materials used during recent decades, differences in the methods and criteria used to assess the frequency of first-time and replacement restorations (e.g. some studies assessed only first-time and replacement composite restorations in anterior or posterior teeth, whereas other studies included amalgam restorations), and differences in the degree to which the various population samples regarded tooth maintenance and regular dental follow-up as important. The present study concerned subjects who sought dental treatment in a private practice and therefore the sample cannot be considered as random.

The decision to replace a restoration is influenced by subjective factors, such as the dentist’s interpretation of the restoration’s condition and the health of the tooth, the criteria used to define failure, and patient demand. These decisions are subject to a great deal of variation³⁷. Standardisation on the issue is lacking and no generally agreed criteria are used to establish when a restoration should be replaced³⁸.

Issues concerning the longevity of restorations are complex, and render the interpretation and comparison of the results of studies very difficult. A restoration may be assumed to have failed if it has been replaced or if clearly defined failure criteria are met. However, the criteria for failure are not well defined and there is often poor inter-and intra-examiner agreement on whether or not criteria are met³⁹.

The median longevity of failed restorations in the present study was approximately 4 years. Several studies have recorded different results and have reported rates of 2.4 years³⁶, 3 years¹⁷, 3.3 years¹⁵, 6 years18., 20., 7.1 years¹⁶, 7.8 years¹⁹, 8 years⁴⁰ and 9 years⁴¹.

Mjør et al.⁴⁰ revealed that cavity form, preparation and the careful handling of the material are prerequisites for the longevity of a restoration. Jokstad et al.⁴ suggested that longevity was influenced by the type and size, the material and, possibly, the intra-oral location of the restoration.

It is difficult to identify specific reasons for the low median longevity of the restorations replaced; however, operative technique, the quality of materials and careful handling according to the manufacturer’s instructions may play important roles⁴⁰.

The success or failure of both first-time and replacement restorations mainly depend on the following closely related factors: the dentist’s skills; patient compliance, and the restorative material used. In addition, the oral hygiene practice of the patient may play an important role in the development of secondary caries and discolouration.

CONCLUSIONS

The principal reasons for the placing of composite restorations were primary caries, tooth discolouration, tooth fracture and erosion. The main reasons for replacing such restorations were secondary caries, restoration discolouration, loss of filling and filling fracture. Most first-time and replacement restorations were in teeth with Class III cavities. The median longevity of a composite restoration was approximately 4 years (39%); 27% of composite restorations lasted for > 8 years, 16% lasted 4–8 years and 18% were replaced within < 1 year.

ACKNOWLEDGEMENTS

The author would like to thank his colleagues for their participation in this study and his patients for their cooperation.

Conflicts of interest

None declared.