Long term follow-up of clinical evaluations of lathe-cute versus spherical amalgam

The Influence of a Short Training Program on the Clinical Examination of Dental Restorations

Training in restoration assessment and the evaluation of such in the clinical environment is shown to produce positive benefits that include improved reliability and agreement with the set standard.

The interval nature of an ordinal scale for measuring the marginal fracture of amalgam

The clinical performance of amalgam alloys over time has been assessed by measuring the extent of marginal fracture of restorations made from these alloys. Scales of photographs of restorations exhibiting varying degrees of marginal fracture have been used to make these assessments. The purpose of this study was to determine the relationship between the ordinal scale numbers of five photographs composing a commonly used scale (Mahler and Marantz, 1979) and the average width in micrometers of marginal fracture of the restorations in the photographs of this scale. In addition, a comparison was made between parametric and non-parametric statistical methods when applied to marginal fracture data. The results showed that four of the five photographs of this scale demonstrated a significant linear regression with marginal fracture width (R2 = 0.997; p = 0.002). The last photograph of the scale, which proved to be an outlier, was not used in the regression and was accommodated by an extrapolation procedure. Using previously gathered clinical data on the marginal fracture behavior of five amalgam alloys, the use of parametric statistical procedures (ANOVA and Scheffé's multiple comparison test) proved to be more discriminatory than the use of nonparametric procedures (Kruskal-Wallis and Dunn's Multiple comparison test) when tested at the same overall confidence level. Thus, having a photographic scale of an interval nature removes any doubt about using the more powerful technique of parametric statistics to evaluate the marginal fracture behavior of dental amalgams.(ABSTRACT TRUNCATED AT 250 WORDS)

Clinical variables affecting the marginal degradation of amalgam restorations

The influence of different clinical variables on the marginal degradation of amalgam restorations was studied in a clinical trial of class-II amalgam restorations. Seven Scandinavian dentists using 5 different alloys placed 468 restorations in 210 patients. The marginal degradation was scored on impressions of the restored teeth by using a six-point ordinal rating scale and was transformed to ridit values. After 5 years 126 patients with 296 restorations remained in the trial. Ridit analysis and paired comparison tests utilizing the Bonferroni correction factor at each yearly interval indicated that the extent of degradation of the restoration margins was influenced by the location in the mouth, the position on the tooth, the type of alloy, and the operator. The results demonstrate that features of the cavity preparation and the handling of the material by the operator are more important for the degradation of the restoration margins than other clinical variables.

Marginal leakage of palladium-enriched amalgam restorations: an in-vitro study

An in-vitro study of marginal leakage around class V restorations, prepared in freshly extracted upper central incisors, tested two types of high copper amalgam: spherical high copper amalgam (Tytin) and spherical high copper amalgam containing palladium (Valiant). No significant statistical difference was noted between the two types of amalgam at the three testing periods. It seemed that the addition of palladium did not improve the marginal leakage.

A new method to measure the condensation pressure of amalgam under in vivo conditions

The purpose of this study was to investigate the condensation pressure of amalgam achieved under close to in vivo conditions by 42 general practitioners who were asked to fill a pre-cut standard class 2 cavity in a mannequin head. A measuring device was designed to allow the maximum and average condensation pressures and working and resting periods to be obtained. The results showed a maximum condensation pressure of 9.17 +/- 3.04 MPa and 4.09 +/- 1.41 MPa with a small (diameter, 1.15 mm) and a large (diameter, 1.8 mm) amalgam plugger, respectively. Only one of the 42 dentists reached the recommended condensation pressure of 15 MPa (Jørgensen, 1977). A significant (p less than or equal to 0.001) correlation between the duration of the working periods and the maximum condensation pressure was found (r = 0.61). Further investigations are required to determine the influence of these different condensation pressures on the physical properties of various amalgams.

Clinical evaluation of high copper amalgam restorations

A comprehensive clinical investigation of amalgam restorations was undertaken to evaluate the performance of "high copper' amalgams and the methods used to examine the marginal integrity of restorations. Six alloys, Aristaloy CR (A), Dispersalloy (D), Indiloy (I), an experimental "high copper' amalgam (E), Tytin (T), and New True Dentalloy (N) as a control, were randomly placed by four operators in 435 Class 1 and Class II restorations. Black and white 1 x photographs were taken at baseline, 6, 12 and 18 months and evaluated using the method described by Mahler & Marantz (1979). In addition, the U.S. Public Health Service system (Cvar & Ryge, 1971) was used at each recall. An analysis of variance based on photographic scoring indicated significant differences (P less than 0.05) among alloys at each recall. The use of Duncan's multiple range test resulted in two homogeneous subsets at 18 months: D, I, E and T, N, A. Six and 12 months recall data showed a close similarity in the rank order of the six alloys. The U.S.P.H.S. system showed no statistically significant differences between the alloys using the chi-square test, however, at each recall the rank order was comparable to that obtained with the photographic method.

Effect of residual mercury content on creep in dental amalgams

For most of the tested amalgams, the increased mercury content caused by delayed compaction increases the flow or creep. The amalgams that had high creep values when packed early were decidedly affected by the increase in mercury content caused by delay in compaction. Amalgams made with Dispersalloy, Tytin, Sybraloy, and New True Dentalloy are not as sensitive to the mercury content as are some of the others tested. Tests for creep may be related more to clinical practice if they are performed on specimens compacted three minutes after trituration rather than on specimens compacted immediately (a half minute) after trituration. In clinical practice, small amounts of amalgam should be mixed and used immediately after trituration. If the delay between trituration and compaction is longer than three minutes, additional mixes are required. We therefore conclude that, in making a large amalgam restoration, many small mixes have superior results over one large mix.

The effect of time on the marginal fracture behaviour of amalgam

In this study the effect of time on the marginal fracture behaviour of amalgam was determined. Six alloys in clinical service for up to 6 years were used as a data base and occlusal photographs were categorized according to a standard set of photographs depicting varying degrees of marginal fracture. The standard set of photographs was assigned a linear numerical scale, and the index of extent of fracture was considered to be an arithmetic mean based on this linear scale. An observed patient effect and unequal sample size were considered in the determination of both the mean and variance. The results of applying these procedures to the data of this study showed that marginal fracture increased with time for all alloys; that the relative ranking of alloys did not change with time; and that, with certain limitations, early time evaluations can predict long-term behaviour.

The effect of the operator on the clinical performance of amalgam

In this study, the effect of the operator on the clinical performance of amalgam was examined by evaluating the marginal fracture characteristics of four alloys placed by four operators. The results were as follows: --Marginal fracture was influenced by the operator. Therefore, careful attention should be given to the cavity design and the placement technique. --The interaction between operators and alloys was such that, for the worst alloy, there was no difference caused by the operators; for the intermediate alloys, there were large differences caused by the operators; and for the best alloy (a non-gamma 2 system), there was almost no difference caused by the operators. --The difference in marginal fracture characteristics among alloys was greater than the difference attributed to operators. --It appears that all practitioners should use non-gamma 2 amalgams because such amalgams perform better clinically and are less susceptible to variations in operators.

Assessment of the quality of restorations. A literature review

Most assessments of the quality of restorations are entirely subjective and involve standard clinical diagnostic equipment. However in recent years there has been an increasing demand for more accurate and reliable methods. Attempts to achieve these have been directed mainly towards the standardization of clinical judgements by the provision of various systems of guidelines of criteria upon which to base them. While these have improved the usefulness of the assessments, they have remained largely subjective. Furthermore, the efficacy of using the particular criteria selected are themselves open to questioning. By the use of more complex methods of examination, often in the field of restorative materials research, assessments have been made of various features of restorations and a body of knowledge concerning factors that might influence or manifest their quality has been build up. However the true significance of much of this knowledge in terms of the clinical behaviour, and thus the finite quality of restorations in service, has yet to be established, for many of the studies have been undertaken in isolation from the dynamic conditions of function in the mouth. Notably, however, a few objective clinical studies have been carried out and objective measurements of some factors affecting the quality of restorations have been reported.

Three-year clinical comparison of three amalgam alloy types emphasizing an appraisal of the evaluation methods used

Five different evaluation techniques were used to measure the marginal breakdown of three-year-old amalgam restorations. The most useful method appeared to be one in which photographs of all restorations were ranked in descending order starting with the restoration that had the least marginal breakdown and ending with the restoration that had the greatest deterioration. Three different alloys were evaluated and the results confirm those of previous studies; the alloy having the lowest creep was superior whereas restorations placed with the alloy having the highest creep displayed the greatest marginal breakdown.