Survival predictions of amalgam restorations

Influence of the experience of operator and assistant on the survival rate of proximal ART restorations: two-year results

AIM

The objective of the study was to determine the influence of the experience of the operator and the assistant on the survival rate of proximal ART- restorations after 2 years when placed using two methods of tooth-isolation and three glass ionomer cement-brands.

STUDY DESIGN

A clinical intervention study.

METHODS

Each of 804 children aged 6-8 years received one proximal restoration in their primary molars. The restorations were placed by 'experienced/inexperienced' operators randomly paired with 'experienced/ inexperienced' assistants. The atraumatic restorative treatment (ART) approach was used with 3 brands of glass ionomer cements (GIC) and 2 tooth-isolation methods (rubber dam vs cotton rolls). Trained and calibrated evaluators evaluated the restorations, soon after placement and after 2 years.

STATISTICS

The data collected were analyzed using SPSS 14.0, to determine and relate the survival rate of the restorations to the operator and assistant with respect to the other factors such as the restorative material used and the isolation method applied.

RESULTS

After 2 years, the survival rate of the restorations was 30.8%. In general, there were no statistical significant differences in the survival rate of the restorations made by the 'experienced' vs 'inexperienced' operators, but individually, the operator with more experience was associated with a significantly higher survival rate of the restorations. The experienced assistants were associated with significantly higher survival rates of the restorations. The most 'experienced' operator paired with any 'experienced' assistant and using rubber dam tooth-isolation method, was associated with a significantly higher survival rate of the restorations.

CONCLUSION

The combination of the 'experienced' operator and assistant using rubber dam tooth-isolation method had the best chance of survival for proximal ART restorations, irrespective of the material-brand used.

An alternative method to reduce polymerization shrinkage in direct posterior composite restorations

BACKGROUND

Polymerization shrinkage is one of dental clinicians' main concerns when placing direct, posterior, resin-based composite restorations. Evolving improvements associated with resin-based composite materials, dental adhesives, filling techniques and light curing have improved their predictability, but shrinkage problems remain.

METHODS

The authors propose restoring enamel and dentin as two different substrates and describe new techniques for placing direct, posterior, resin-based composite restorations. These techniques use flowable and microhybrid resin-based composites that are polymerized with a progressive curing technique to restore dentin, as well as a microhybrid composite polymerized with a pulse-curing technique to restore enamel. Combined with an oblique, successive cusp buildup method, these techniques can minimize polymerization shrinkage greatly.

CONCLUSIONS

Selection and appropriate use of materials, better placement techniques and control polymerization shrinkage may result in more predictable and esthetic Class II resin-based composite restorations.

CLINICAL IMPLICATIONS

By using the techniques discussed by the authors, clinicians can reduce enamel microcracks and substantially improve the adaptation of resin-based composite to deep dentin. As a consequence, marginal discoloration, recurrent caries and postoperative sensitivity can be reduced, and longevity of these restorations potentially can be improved.

Direct posterior restorations: clinical results and new developments

The longevity of dental restorations is dependent on many different factors, including those related to materials, the dentist, and the patient. The main reasons for restoration failure are secondary caries, fracture of the bulk of the restoration or of the tooth, and marginal deficiencies and wear. The importance of direct-placement, aesthetic, tooth-colored restorative materials is still increasing. Amalgam restorations are being replaced because of alleged adverse health effects and inferior aesthetic appearance. All alternative restorative materials and procedures, however, have certain limitations. Direct composite restorations require a time-consuming and more costly treatment procedure and are actually only indicated for patients with excellent oral hygiene. Glass ionomers can be considered only as long-term provisional restorations in stress-bearing posterior cavities. Future treatment regimens that are made possible by the development of sophisticated preparation techniques, improved dentin bonding agents, and resin-based restorative materials will result in the therapy of more small-sized lesions rather than large restorations. The importance of indirect inlay techniques will shift more and more toward the direct restoratives. As the cavities become smaller, it is to be expected that the use of improved direct restorative materials will provide excellent longevity even in stress-bearing situations.

Posterior resin-based composite restorations: clinical recommendations for optimal success

Resin-based composites are increasingly used for the restoration of defects in posterior teeth. This review describes, illustrates and discusses important clinical aspects of the posterior composite technique. A relatively new stratification concept oriented to the development of functional and anatomic restorations is proposed.

Replacement risk of amalgam treatment modalities: 15-year results

OBJECTIVES

This paper reports on the replacement risk of different treatment modalities for Class II amalgam restorations in a clinical trial of 15 years duration.

METHODS

The performance of 1117 conventional Class II amalgam restorations in a controlled, longitudinal study were analysed using logistic regression with a random component. Primary variables regarding replacement risk were the treatment modality (cavity wall treatments) and alloy (conventional versus high copper). Secondly, the operator, type of tooth and type of restoration (MO/DO vs MOD) were considered.

RESULTS

Over 15 years, 17% of the restorations were replaced (true failures). The application of copalite varnish or silver suspension and the type of alloy did not reduce the replacement risk. Reduced risks were observed by providing a 90-degree cavosurface angle combined with a cavity wall finish. The operator and the type of restoration determine replacement risk to a significant extent.

CONCLUSIONS

Additional treatment modalities do not necessarily reduce replacement risks of Class II amalgam restorations within 15 years, while clinical variables affect the risk of replacement to a certain degree.

Long-term survival of extensive amalgam restorations

In cost-effectiveness analysis and contemporary treatment planning strategies, the postponement of placement of cast crowns plays an important role. Extensive amalgam restorations that involve the rebuilding of cusps and the provision of auxiliary retention are thought to make this postponement possible. This study reports the long-term survival (100 months) of extensive amalgam restorations in a randomized, controlled clinical trial. The operational hypothesis was that the type of retention and the operator have a long-term influence on the survival and clinical functioning of extensive amalgam restorations. Three hundred extensive amalgam restorations were placed by three operators in molar teeth in which one or more cusps were reconstructed. Five different auxiliary retention methods were used for retention of these restorations. Since the purpose of extensive amalgam restorations is considered to be two-fold (to restore a broken-down molar to function acceptably as an independent restoration and to create a substructure for subsequent crown construction), survival was assessed at different levels. The survival rate of extensive amalgam restorations as an independent restoration was 88+/-2%. The functional survival rate (as an independent restoration or as a substructure) was 92+/-2%. The influence of experimental variables ('retention method' and 'operator') and background variables ('tooth type', 'extension of extensive amalgam restorations', and 'age of patient') on the survival was analyzed by Log Rank and Breslow tests. The analyses revealed that there were no statistically significant influences on the survival rates except for the variable 'age of patient' (p < or = 0.05). Extensive amalgam restorations were more prone to failure in the group of older patients than in the group of younger ones. It is concluded that the clinical survival of extensive amalgam restorations is independent from several clinical variables in the study.

Benefits and disadvantages of tooth-coloured alternatives to amalgam

OBJECTIVES

To give the practising dentist scientifically based data to assist him/her in the responsible decision-making process necessary to weigh the options available to the patient if she/he prefers not to have an amalgam placed.

DATA SOURCES

Based on the literature and on the research work, which was done in the author's department, the indications and limitations of the known alternatives of amalgam were formulated. DESCRIPTION OF ALTERNATIVES TO AMALGAM: With the exception of cast gold restorations, all alternatives require the strict use of adhesive techniques. When compared with similar amalgam restorations, placing composite restorations (if they are indicated) takes approximately 2.5 times longer because complex incremental techniques are needed. Despite all the efforts, direct composite restorations placed in large cavities still show unacceptable amounts of marginal openings. Tooth-coloured inlays are a better alternative for large restorations. These restorations must be inserted with adhesive techniques. With composite inlays it is difficult to achieve a composite-composite bond. Ceramic inlays may be micromechanically bonded to the luting composite. They all show clinically a good marginal behaviour and the use of ultrasonic energy may further simplify the application technique of aesthetic inlays.

STUDY SELECTION

Papers describing the different techniques were used as a base for the corresponding chapter. To assess and compare the longevity of the different restoration types, literature data were used. We limited ourselves to papers reporting at least 5-year clinical data. Longitudinal, clinically controlled studies were preferred. However, to be more complete, retrospective, cross sectional studies were also included. LONGEVITY OF POSTERIOR RESTORATIONS: Amalgam shows excellent longevity data with studies up to 20 years. The average annual failure rate is 0.3-6.9%. Posterior composites are in the same range (0.5-6.6%), however, the study times are much shorter (max. 10 years). For tooth-coloured inlays much less data are available. Longevity is reported up to 6 years with annual failure rates of 0.6-5%.

CONCLUSIONS

All aesthetic alternatives to amalgam require more complex procedures and more time. If cost benefit considerations are a concern, amalgam is still the most convenient restorative material for posterior teeth.

Longitudinal study of pressed glass-ceramic inlays for four and a half years

STATEMENT OF PROBLEM

Some restorative materials used in the posterior region of the mouth present conventional problems, such as microleakage, recurrent caries, wear, and poor color stability.

PURPOSE

This study determined the reliability of the IPS Empress ceramic material for fabricating inlays and onlays in the posterior region of the mouth.

MATERIAL AND METHODS

A total of 125 IPS Empress pressed glass ceramic inlays were placed for 29 patients in a private practice. The restorations were observed for a period of 7 to 56 months, with a mean of 40.3 months. All inlays were constructed in the same dental laboratory and the restorative materials used according to the manufacturers' instructions. The restorations were evaluated clinically according to modified U.S. Public Health Service criteria at the time of insertion and at periodic recall appointments. Kaplan-Meier statistics were used to calculate survival rates.

RESULTS

Clinical evaluation revealed that pressed glass ceramic inlays, with the exception of four fractured restorations, were rated from Alpha to Bravo for each criteria. Marginal discoloration recorded the lowest percentage of alpha ratings (65.3%). The estimated survival rate after approximately a 4.5-year follow-up period was 95.63% (95% confidence interval; 90.77% to 99.95%).

Cost-conservative dentistry: appropriate dentistry at lower cost

Dental practitioners in both private and public dentistry are faced with patients who for reasons of public or private finance are not able to be treated with the most sophisticated available dentistry. A concept of appropriate dentistry is provided whereby, with reference to available literature, it is shown that cost-conservative treatment can be provided that is likely to be satisfactory to both the client and the practitioner.

Predictions of resin-bonded bridge survivals, comparing two statistical models

The purpose of this study was to compare the predictive accuracy of the standard Weibull distribution model with that of a modification, or mixture model, for resin-bonded etched-metal bridge survivals. A total of 189 bridges placed in adult patients treated by students and staff at a teaching hospital was evaluated over periods of up to 8 years. Survival predictions based on the actual survival data accumulated in 1989 were compared with the later survival data updated in 1992. Comparison of the two fitted Weibull predictive curves with the life table survival estimates from the 1992 updated data demonstrated clearly the improved accuracy of the mixture model for predicting survivals of the resin-bonded bridges in this study.

Predictions of restoration deterioration

This study evaluated the application of a mixture model involving a Weibull distribution function to predict the median times for restorations of three dental restorative materials to achieve unsatisfactory rating scores for six clinical factors. The accuracy of the method was assessed graphically against the known actuarial long-term deterioration observations of 1813 amalgam, 1774 anterior resin composite and 474 glass polyalkenoate (ionomer) cement restorations, assessed over periods of up to 20, 18 and 14 years, respectively. Of the six clinical factors investigated (which included marginal fracture), only four had sufficient long-term unsatisfactory rating score data to enable their median times to be predicted. These predicted times were: for amalgam restorations, surface roughness 32.5 years and surface tarnishing 16.0 years; for resin composites, marginal staining 25.4 years and colour mismatch 14.2 years; and for glass polyalkenoate (ionomer) cements, marginal staining 17.6 years and colour mismatch 3.6 years. The known and predictive unsatisfactory rating score results were generally in close agreement. However, it was not possible to predict median times for unsatisfactory rating scores associated with very slowly deteriorating restoration factors. The actual replacement rates of the amalgam restorations were too low to obtain their median survival time. However, for the faster failing resin composites this time was 7.9 +/- 0.5 years, and for the glass polyalkenoate (ionomer) cements 2.2 +/- 0.2 years. The relationship of restoration deterioration to restoration replacement and dental health requires further analysis.

Report of the Committee on Scientific Investigation of the American Academy of Restorative Dentistry

The committee screened several hundred articles, citing 518 published papers. Some are present quality in research, others provide clinical interest, and some are identified as misleading. New techniques in pulp physiology and pathology are reported. Laser use and techniques in prevention, restorative dentistry, and materials use are reported. Epidemiology of selected diseases and the results of various formulations for treatment are cited. Diagnosis of craniomandibular dysfunction is well represented as well as references to literature reviews and other sophisticated scientific investigation. Research on adhesives is presented in respect to bonding agents for dentin and enamel. Several clinical studies are included, along with customary laboratory reports on several materials.