Journal
of Dentistry,
4, No. 5, 1976,
pp. 207-210,
Printed
in Greet Britain
The prevalence of failure of restorations: a literature review R.J. Elderton, PhD, BDS, LDS Experimental Dental Care Project, The London Hospital Medical College, London
ABSTRACT
Millions of dental restorations are placed each year, yet many fait in service. Different workers have reported varying figures for the prevalence of this failure, but in general it appears that about a third of all restorations present at any one time may be considered to have failed for one reason or another.
INTRODUCTION Dental caries is perhaps disease affecting mankind,
the most prevalent and its treatment by
surgical excision and prosthetic restoration has been a major preoccupation of dentists since the middle of the last century. The demand for dental treatment has steadily risen and the number of restorations placed each year has increased dramatically. In the United Kingdom 36 million restorations, approximately 80 per cent of which were of amalgam, were provided during 1973 in the General Dental Services of the National Health Service alone, at a cost of ES2 million (Dental Estimates Board, 1973). However, little information is available relating to the expected lifespan of these restorations or to the proportion that replaced previous ones. Holloway (1974) and others have advanced the hypothesis that restorative dentistry is palliative rather than therapeutic, i.e. that it prolongs the life of the dentition rather than saves it. While this would seem to be a most critical indictment of restorative dentistry, it indicates the severity of the consequences of failed restorations. That some restorations fail is an undoubted fact, but the magnitude of the problem and the
reasons for the failures are subjects for speculation since there have been no appropriately designed long-term studies to investigate these matters fully. Such studies would not only be difficult to undertake, but also they would inevitably be subject to considerable bias on account of patient selection and operator variation, both at the time of insertion of the restorations and later in their assessment. Nevertheless, there are published studies which yield useful information on the prevalence of failure of restorations; these studies form the subject of this review. An examination of other work, where attempts have been made to define and categorize the causes of failure of restorations, will be made in a subsequent article. REVIEW OF THE LITERATURE An early investigation which shed some light upon the extent of failures among restorations was reported more than 50 years ago by Ottolengui (1925). He examined extracted teeth that had been restored with amalgam, and, on account of caries associated with their margins, considered that 5 1 per cent of 1067 amalgam surfaces had ‘failed. However, since many of the teeth may have been extracted on account of this caries, the sample must be considered to have been biased towards a high failure rate. Further, since no information was given concerning the ages of the restorations, the time scale over which the failures occurred could not be examined. It was not until the current decade that such information first became available through the work of Robinson (197 1).
208
Robinson appears to have illustrated well the pattern of failure of restorations. Though small, his study was most interesting and probably unique. He analysed the failures among 145 amalgam and 23 silicate restorations in 43 patients over a period of 21 years in his dental practice in London. Strict rules were adopted for defining failure, and extraction of a tooth containing a restoration was included among them, even though the restoration may in fact have been quite sound in itself. The findings showed that the proportions of amalgam restorations that had failed were 27 per cent after 5 years, 50 per cent after IO years and 77 per cent after 20 years. There was clearly a tendency for the rate of failure to diminish slightly with time, but this is probably of little significance. In comparison, the silicate restorations survived rather better in the short term but had a higher incidence of failure-91 per cent-over 20 years. A more usual approach to quantifying the life of restorations has been to assess the prevalence of their success and failure in samples obtained from among patients attending dental school clinics. Thus, Harvey (1962) at Emory University examined 1197 restorations involving either the mesio-occlusal surfaces of ftrst molars or the disto-occlusal surfaces of second premolars, since he considered these to have particularly high caries rates. He found that 44 per cent of the restorations were of amalgam, of which 6 per cent had failed, while 56 per cent were gold inlays, of which 4 per cent had failed. Each restoration was assessed in the mouth by three dentists who also used bitewing radiographs to aid their diagnoses. These low failure rates may have been influenced by the nature of the sample since only a quarter of the patients sent for attended the examinations; many of these might have only just completed treatment. Allan (1969), on the other hand, examined patients who were about to commence treatment. He recorded a failure rate of 33 per cent among 887 restorations of various materials, using a critical standard of assessment by routine clinical means including bitewing radiographs
Journal of Dentistry,
Vol. ~/NO.
5
where indicated. The criteria for assigning a restoration as failed were severe and included: caries elsewhere in the tooth necessitating removal of the restoration, lack of a contact point, pulpal pathology and extraction for orthodontic or prosthetic reasons. The criteria which have been cited accounted for almost one-third of the failures, the remainder being attributed to poor restorative technique in its own right. In a larger study in Missouri, Moore and Stewart (1967) examined the records of 21 728 teeth in 907 patients aged between 12 and 81 years who were under active treatment. Thirtynine per cent of the teeth contained restorations, over three-quarters of which were of amalgam. Forty-five per cent were considered to be defective and in need of replacement. In terms of the overall numbers of operative procedures required for these patients, it is salutary to realize that as many as 38 per cent were on account of these defective restorations. In view of the high incidence of failure, some information on the criteria used for assessing restorations in this dental school might have helped in the interpretation of the results. In a study at The London Hospital, however, in spite of a relatively low rate of failure of restoration surfaces (10 per cent) being recorded in 95 young adults who presented for dental care, the proportion of tooth surfaces requiring restorative work on account of failure of previous treatment was much the same as in the Missouri study at 43 per cent (Experimental Dental Care Project, 1973). While dissimilar samples may have been responsible for the great difference between the proportions of failed restorations in these two studies, differences in levels of diagnosis were probably largely responsible, since the ratios of new carious lesions to failed restorations were alike in both studies. Also, in the London study the dentist making the diagnoses was himself responsible for carrying out the treatment that he indicated to be necessary. His diagnostic criteria may therefore have been less critical in order to save himself some clinical work.
Elderton: Prevalence of Failure of Restorations
In comparison with the findings of Mooreand Stewart (1967) that treatment arising from defective restorations accounted for 38 per cent of all operative procedures in the dental school in Missouri, a study reported by Richardson and Boyd (1973) is particularly interesting, for while a slightly different parameter was measured, it concerned the conditions of private practice. Fifty dental practitioners in British Columbia were questioned with respect to the number of amalgam restoration surfaces they replaced during a sample l-week period. The mean finding was 33 surfaces replaced per dentist, the cost of this treatment representing about 20 per cent of the total gross incomes, and therefore productivity, of the dentists concerned. While in the dental school environment where the examining dentists were unlikely to have been much involved on a personal basis with the original restorative work that they assessed, in the general practice study the opposite would apply at least to some extent, and a lower proportion of failures might therefore be expected. In fact, it is clear that in both situations treatment to overcome the consequences of failed restorations constituted a major item of the dental service provided, and that much time and money were involved. Some investigators have reported specifically on the failure of the more complex types of restoration. Thus, in a German study, von Sobkowiak and Teseler (1970) carried out a clinical and radiographic study of gold and silvertin inlays that had functioned in the mouth for a mean period of 6 years. Using secondary caries as their criterion for failure, they found that 49 per cent were unsatisfactory, the two materials behaving alike in this respect. Morrant (1956) reviewed bridges that had been carried out at the Eastman Dental Hospital and noted that 8 per cent of 122 bridges made in 1954 had failed during the first year. He was unable to take into account any failures that might have been present in patients who failed to attend the recall appointment, but commented that it would not be surprising if 35 per cent of
209
bridges failed within 5 years. The criteria that he used to define failure were: recurrent caries, loosening of a retainer or breakage requiring reconstruction of the bridge. It is refreshing to be able to report considerable success with restorations in some studies. However, these have all been designed primarily to test and compare the clinical performance of restorative materials; the operative procedures employed were therefore probably not typical of the field situation. For example, there was probably unlimited clinical time available and it is likely that the operators were working to particularly high standards, for they were university faculty members and knew that the restorations were to be assessed. The most extreme example of success under these conditions has been reported by Leinfelder et al. (1974) in a clinical study in North Carolina. They examined over 1000 composite resin restorations for Class 1, II and III lesions that had served for up to 2’%years and found no recurrent caries throughout the period of study-a most remarkable finding. However, such defects as surface wear of the restorative material were common. While these were not sufficiently severe to constitute failure, the longer term picture might well be very different, especially in the light of the studies reviewed above. It is clear that many different approaches have been made in attempts to quantify the success and failure of restorations; it is therefore unwise to compare different studies too closely, especially as the samples and the methods of assessment, in particular the criteria for failure, differed widely. Indeed, in many of the studies the clinical diagnoses of various dentists, and perhaps sometimes dental students, were accepted without any attempts to define the criteria at all. These differences probably explain the wide variations in the results reported. However, even with these conditions borne in mind, it is possible to hint at an overall picture of the extent of the problem. The proportions of failed restorations in the studies reviewed where the ages of the restora-
210
Journal of Dentistry, Vol. ~/NO. 5
be more accurate to assume that every restoration stands a high chance of failing within a few years.
tions were either not stated or were over 3 years ranged from 4 to 91 per cent, with a mean prevalence of about 1 in 3 restorations. Even considering that some of the samples may have included patients with particularly gross restorative needs, it is clear that the dental profession is presented with a large and indeed somewhat embarrassing problem. In a study of occlusal amalgam restorations, Elderton (1975) showed that clinicians usually believe their operative work to be excellent. The writers of textbooks on restorative dentistry may be partly responsible for this attitude, since they rather lead their readers to assume that the treatment procedures that they describe will normally be successful. However, in the light of the studies reviewed here it seems that it might be more accurate to assume that every restoration stands a high chance of failing within a matter of a few years. Certainly, the universal adoption of such a philosophy might engender a greater sense of conservatism in cavity design, as cavities tend to increase in size when restorations are replaced (Elderton, 1975). Widespread knowledge of this massive problem associated with restorative care might also serve to enhance appreciation of the advantages of preventive dentistry and so encourage the demand for preventive procedures on a larger and more serious scale than at present.
might
CONCLUSIONS
Ottolengui R. (1925) Failures with amalgam as commonly used. Dent. Cosmos 67,9981008. Richardson A. S. and Boyd M. A. (1973) Replacement of silver amalgam restorations by 50 dentists during 246 working days. J. Can. Dent.
While reports of the prevalence of the failure of restorations vary considerably, in general it appears that about 1 in 3 of all restorations present at any one time is unsatisfactory and has therefore failed in some way to meet the criteria commonly used to determine success. Rather
than the assumption engendered in textbooks that restorative treatment will normally be successful in the long term, it would seem that it
REFERENCES Allan D. N. (1969) The durability of conservative restorations. Br. Dent. J. 126, 172-177. Dental Estimates Board (1973) Annual Report,, England and wales. Eastbourne. Elderton R. J. (1975) An in vivo morphological study of cavity and amalgam margins on the occlusal surfaces of human teeth. PhD Thesis, University of London. Experimental Dental Care Project (1973) Report No. 2. The London Hospital Medical College, p. 24. Harvey 0. D. (1962) Caries resistance of filling materials. Dent. Progr. 2, 197-198. Holloway P. J. (1974) The success of restorative dentistry. Paper presented at FDI Congress, London, September. Leinfelder K. F., Sluder T. B., Sockwell C. L., Strickland W. D. and Wall J. T. (1974) Clinical evaluation of composites as anterior and posterior restorative materials. J. Dent. Res. 53, 152.
Moore D. L. and Stewart J. L. (1967) Prevalence of defective dental restorations. J. Prosthet. Dent. 17,372-378.
Morrant G. A. (1956) Bridges with particular relation to the periodontal tissues. Dent. Pratt. Dent. Rec. 6, 178-186.
Assoc. 8, 556-559.
Robinson
A. D. (1971)
The life of a filling. Br.
Dent. J. 130,206-208.
Von Sobkowiak E. M. and Teseler U. (1970) Zur frage der sekundarkaries. Dtsch. Stomatol. 20, 670-679.
of Dentistry,
4, No. 5, 1976,
pp. 207-210,
Printed
in Greet Britain
The prevalence of failure of restorations: a literature review R.J. Elderton, PhD, BDS, LDS Experimental Dental Care Project, The London Hospital Medical College, London
ABSTRACT
Millions of dental restorations are placed each year, yet many fait in service. Different workers have reported varying figures for the prevalence of this failure, but in general it appears that about a third of all restorations present at any one time may be considered to have failed for one reason or another.
INTRODUCTION Dental caries is perhaps disease affecting mankind,
the most prevalent and its treatment by
surgical excision and prosthetic restoration has been a major preoccupation of dentists since the middle of the last century. The demand for dental treatment has steadily risen and the number of restorations placed each year has increased dramatically. In the United Kingdom 36 million restorations, approximately 80 per cent of which were of amalgam, were provided during 1973 in the General Dental Services of the National Health Service alone, at a cost of ES2 million (Dental Estimates Board, 1973). However, little information is available relating to the expected lifespan of these restorations or to the proportion that replaced previous ones. Holloway (1974) and others have advanced the hypothesis that restorative dentistry is palliative rather than therapeutic, i.e. that it prolongs the life of the dentition rather than saves it. While this would seem to be a most critical indictment of restorative dentistry, it indicates the severity of the consequences of failed restorations. That some restorations fail is an undoubted fact, but the magnitude of the problem and the
reasons for the failures are subjects for speculation since there have been no appropriately designed long-term studies to investigate these matters fully. Such studies would not only be difficult to undertake, but also they would inevitably be subject to considerable bias on account of patient selection and operator variation, both at the time of insertion of the restorations and later in their assessment. Nevertheless, there are published studies which yield useful information on the prevalence of failure of restorations; these studies form the subject of this review. An examination of other work, where attempts have been made to define and categorize the causes of failure of restorations, will be made in a subsequent article. REVIEW OF THE LITERATURE An early investigation which shed some light upon the extent of failures among restorations was reported more than 50 years ago by Ottolengui (1925). He examined extracted teeth that had been restored with amalgam, and, on account of caries associated with their margins, considered that 5 1 per cent of 1067 amalgam surfaces had ‘failed. However, since many of the teeth may have been extracted on account of this caries, the sample must be considered to have been biased towards a high failure rate. Further, since no information was given concerning the ages of the restorations, the time scale over which the failures occurred could not be examined. It was not until the current decade that such information first became available through the work of Robinson (197 1).
208
Robinson appears to have illustrated well the pattern of failure of restorations. Though small, his study was most interesting and probably unique. He analysed the failures among 145 amalgam and 23 silicate restorations in 43 patients over a period of 21 years in his dental practice in London. Strict rules were adopted for defining failure, and extraction of a tooth containing a restoration was included among them, even though the restoration may in fact have been quite sound in itself. The findings showed that the proportions of amalgam restorations that had failed were 27 per cent after 5 years, 50 per cent after IO years and 77 per cent after 20 years. There was clearly a tendency for the rate of failure to diminish slightly with time, but this is probably of little significance. In comparison, the silicate restorations survived rather better in the short term but had a higher incidence of failure-91 per cent-over 20 years. A more usual approach to quantifying the life of restorations has been to assess the prevalence of their success and failure in samples obtained from among patients attending dental school clinics. Thus, Harvey (1962) at Emory University examined 1197 restorations involving either the mesio-occlusal surfaces of ftrst molars or the disto-occlusal surfaces of second premolars, since he considered these to have particularly high caries rates. He found that 44 per cent of the restorations were of amalgam, of which 6 per cent had failed, while 56 per cent were gold inlays, of which 4 per cent had failed. Each restoration was assessed in the mouth by three dentists who also used bitewing radiographs to aid their diagnoses. These low failure rates may have been influenced by the nature of the sample since only a quarter of the patients sent for attended the examinations; many of these might have only just completed treatment. Allan (1969), on the other hand, examined patients who were about to commence treatment. He recorded a failure rate of 33 per cent among 887 restorations of various materials, using a critical standard of assessment by routine clinical means including bitewing radiographs
Journal of Dentistry,
Vol. ~/NO.
5
where indicated. The criteria for assigning a restoration as failed were severe and included: caries elsewhere in the tooth necessitating removal of the restoration, lack of a contact point, pulpal pathology and extraction for orthodontic or prosthetic reasons. The criteria which have been cited accounted for almost one-third of the failures, the remainder being attributed to poor restorative technique in its own right. In a larger study in Missouri, Moore and Stewart (1967) examined the records of 21 728 teeth in 907 patients aged between 12 and 81 years who were under active treatment. Thirtynine per cent of the teeth contained restorations, over three-quarters of which were of amalgam. Forty-five per cent were considered to be defective and in need of replacement. In terms of the overall numbers of operative procedures required for these patients, it is salutary to realize that as many as 38 per cent were on account of these defective restorations. In view of the high incidence of failure, some information on the criteria used for assessing restorations in this dental school might have helped in the interpretation of the results. In a study at The London Hospital, however, in spite of a relatively low rate of failure of restoration surfaces (10 per cent) being recorded in 95 young adults who presented for dental care, the proportion of tooth surfaces requiring restorative work on account of failure of previous treatment was much the same as in the Missouri study at 43 per cent (Experimental Dental Care Project, 1973). While dissimilar samples may have been responsible for the great difference between the proportions of failed restorations in these two studies, differences in levels of diagnosis were probably largely responsible, since the ratios of new carious lesions to failed restorations were alike in both studies. Also, in the London study the dentist making the diagnoses was himself responsible for carrying out the treatment that he indicated to be necessary. His diagnostic criteria may therefore have been less critical in order to save himself some clinical work.
Elderton: Prevalence of Failure of Restorations
In comparison with the findings of Mooreand Stewart (1967) that treatment arising from defective restorations accounted for 38 per cent of all operative procedures in the dental school in Missouri, a study reported by Richardson and Boyd (1973) is particularly interesting, for while a slightly different parameter was measured, it concerned the conditions of private practice. Fifty dental practitioners in British Columbia were questioned with respect to the number of amalgam restoration surfaces they replaced during a sample l-week period. The mean finding was 33 surfaces replaced per dentist, the cost of this treatment representing about 20 per cent of the total gross incomes, and therefore productivity, of the dentists concerned. While in the dental school environment where the examining dentists were unlikely to have been much involved on a personal basis with the original restorative work that they assessed, in the general practice study the opposite would apply at least to some extent, and a lower proportion of failures might therefore be expected. In fact, it is clear that in both situations treatment to overcome the consequences of failed restorations constituted a major item of the dental service provided, and that much time and money were involved. Some investigators have reported specifically on the failure of the more complex types of restoration. Thus, in a German study, von Sobkowiak and Teseler (1970) carried out a clinical and radiographic study of gold and silvertin inlays that had functioned in the mouth for a mean period of 6 years. Using secondary caries as their criterion for failure, they found that 49 per cent were unsatisfactory, the two materials behaving alike in this respect. Morrant (1956) reviewed bridges that had been carried out at the Eastman Dental Hospital and noted that 8 per cent of 122 bridges made in 1954 had failed during the first year. He was unable to take into account any failures that might have been present in patients who failed to attend the recall appointment, but commented that it would not be surprising if 35 per cent of
209
bridges failed within 5 years. The criteria that he used to define failure were: recurrent caries, loosening of a retainer or breakage requiring reconstruction of the bridge. It is refreshing to be able to report considerable success with restorations in some studies. However, these have all been designed primarily to test and compare the clinical performance of restorative materials; the operative procedures employed were therefore probably not typical of the field situation. For example, there was probably unlimited clinical time available and it is likely that the operators were working to particularly high standards, for they were university faculty members and knew that the restorations were to be assessed. The most extreme example of success under these conditions has been reported by Leinfelder et al. (1974) in a clinical study in North Carolina. They examined over 1000 composite resin restorations for Class 1, II and III lesions that had served for up to 2’%years and found no recurrent caries throughout the period of study-a most remarkable finding. However, such defects as surface wear of the restorative material were common. While these were not sufficiently severe to constitute failure, the longer term picture might well be very different, especially in the light of the studies reviewed above. It is clear that many different approaches have been made in attempts to quantify the success and failure of restorations; it is therefore unwise to compare different studies too closely, especially as the samples and the methods of assessment, in particular the criteria for failure, differed widely. Indeed, in many of the studies the clinical diagnoses of various dentists, and perhaps sometimes dental students, were accepted without any attempts to define the criteria at all. These differences probably explain the wide variations in the results reported. However, even with these conditions borne in mind, it is possible to hint at an overall picture of the extent of the problem. The proportions of failed restorations in the studies reviewed where the ages of the restora-
210
Journal of Dentistry, Vol. ~/NO. 5
be more accurate to assume that every restoration stands a high chance of failing within a few years.
tions were either not stated or were over 3 years ranged from 4 to 91 per cent, with a mean prevalence of about 1 in 3 restorations. Even considering that some of the samples may have included patients with particularly gross restorative needs, it is clear that the dental profession is presented with a large and indeed somewhat embarrassing problem. In a study of occlusal amalgam restorations, Elderton (1975) showed that clinicians usually believe their operative work to be excellent. The writers of textbooks on restorative dentistry may be partly responsible for this attitude, since they rather lead their readers to assume that the treatment procedures that they describe will normally be successful. However, in the light of the studies reviewed here it seems that it might be more accurate to assume that every restoration stands a high chance of failing within a matter of a few years. Certainly, the universal adoption of such a philosophy might engender a greater sense of conservatism in cavity design, as cavities tend to increase in size when restorations are replaced (Elderton, 1975). Widespread knowledge of this massive problem associated with restorative care might also serve to enhance appreciation of the advantages of preventive dentistry and so encourage the demand for preventive procedures on a larger and more serious scale than at present.
might
CONCLUSIONS
Ottolengui R. (1925) Failures with amalgam as commonly used. Dent. Cosmos 67,9981008. Richardson A. S. and Boyd M. A. (1973) Replacement of silver amalgam restorations by 50 dentists during 246 working days. J. Can. Dent.
While reports of the prevalence of the failure of restorations vary considerably, in general it appears that about 1 in 3 of all restorations present at any one time is unsatisfactory and has therefore failed in some way to meet the criteria commonly used to determine success. Rather
than the assumption engendered in textbooks that restorative treatment will normally be successful in the long term, it would seem that it
REFERENCES Allan D. N. (1969) The durability of conservative restorations. Br. Dent. J. 126, 172-177. Dental Estimates Board (1973) Annual Report,, England and wales. Eastbourne. Elderton R. J. (1975) An in vivo morphological study of cavity and amalgam margins on the occlusal surfaces of human teeth. PhD Thesis, University of London. Experimental Dental Care Project (1973) Report No. 2. The London Hospital Medical College, p. 24. Harvey 0. D. (1962) Caries resistance of filling materials. Dent. Progr. 2, 197-198. Holloway P. J. (1974) The success of restorative dentistry. Paper presented at FDI Congress, London, September. Leinfelder K. F., Sluder T. B., Sockwell C. L., Strickland W. D. and Wall J. T. (1974) Clinical evaluation of composites as anterior and posterior restorative materials. J. Dent. Res. 53, 152.
Moore D. L. and Stewart J. L. (1967) Prevalence of defective dental restorations. J. Prosthet. Dent. 17,372-378.
Morrant G. A. (1956) Bridges with particular relation to the periodontal tissues. Dent. Pratt. Dent. Rec. 6, 178-186.
Assoc. 8, 556-559.
Robinson
A. D. (1971)
The life of a filling. Br.
Dent. J. 130,206-208.
Von Sobkowiak E. M. and Teseler U. (1970) Zur frage der sekundarkaries. Dtsch. Stomatol. 20, 670-679.
