A preliminary study on a resin-modified glass-ionomer cement for transitional restorations and subsequent core buildups.

PURPOSE: The purpose of this study was to evaluate the serviceability of a resin-modified glass-ionomer cement for transitional restorations and subsequent core buildups in endodontically treated maxillary premolars. MATERIALS AND METHODS: Fifty Vitremer restorations were made in 42 patients by one operator during a period of 5 months. After 1 year of follow up, the quality of the restorations was assessed for the variables occlusal contacts, proximal contacts, marginal adaptation, and surface roughness. Survival was estimated at 2 years of service either as a transitional restoration or as a core buildup. RESULTS: The percentage survival of the transitional restorations was 85% +/- 6%. When the crowned Vitremer restorations were added to the transitional restorations, the 2-year survival was 98% +/- 2%. With respect to the quality assessment, the majority of the restorations showed either no or light occlusal contacts and no or light contacts on at least one of their proximal surfaces. Marginal integrity and surface roughness were considered to be suboptimal on average. CONCLUSION: The described restorations seem to perform adequately for a transitional period of 1 to 2 years. Their viability as substructures for permanent cast restorations remains to be tested in long-term clinical studies.

[Long-term survival of extensive amalgam restorations]. / Langetermijnoverleving van uitgebreide amalgaamrestauraties.

In cost-effectiveness analysis and contemporary treatment planning strategies, the postponement of placement of cast crowns plays an important role. Extensive Amalgam Restorations (EAR), 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 EAR in a randomized, controlled clinical trial. A total of 300 EAR were placed by 3 operators in molar teeth in which one or more cusps were reconstructed. Five different auxiliary retention methods were used for retention of these restorations. As the purpose of EAR is considered to be twofold (to restore a broken-down molar to acceptably function as an independent restoration and to create a substructure for subsequent crown construction), survival was assessed at different levels. The survival rate of EAR 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 EAR and age of patient) on the survival was analysed using 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 < 0.05). EAR was more prone to failure in the group of older patients than the group of younger ones.

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.

The influence of absolute humidity on shear bond adhesion.

OBJECTIVES: The purpose of this study was to investigate the relationship between dentine shear bond strength, using data from experiments performed according to a standard protocol, and the absolute humidity for a new, fourth generation dentine adhesive system. METHODS: Results of seven recently performed adhesion experiments using the same protocol and product were analysed. Groups of 10 human molars were each bonded in a humidity chamber. The temperature and relative humidity conditions varied from 23 to 37 degrees C and 30 to 95%. After bonding of the composite resin a shear bond test at a crosshead speed of 2.0 mm/min was performed. RESULTS: The bond strength levels of the dentine adhesive system were influenced significantly by extreme temperature and humidity differences. Adhesion levels varied from 27.8 (SD 8.5) MPA to 12.8 (SD 1.4) MPA. Isobond strength curves are a good method to gain insight into the humidity sensitivity of adhesive systems. CONCLUSIONS: Results of in vitro adhesive bonding procedures for a dentine adhesive can be significantly influenced by the absolute humidity levels at which the procedures are performed. Consequently "Materials and Methods" sections of publications should refer to absolute humidity or temperature and relative humidity levels as a relevant parameter.

Intraoral humidity during operative procedures.

Results of dentine adhesion studies are influenced by many factors such as intrinsic and extrinsic dentine wetness. Relative air humidity and temperature are extrinsic environmental factors whose influence on dentine bonding capability is not precisely known. It was the aim of this study to gain an understanding of these factors as present in the mouths of patients and as influenced by several variables. In six different experiments the influence of application of a rubber dam, high and low relative humidity in the dental surgery, nose and mouth breathing and tooth drying was investigated. The results show that without application of a rubber dam there was no statistically significant difference in temperature for the variables nose and mouth breathing and tooth drying (mean 27.7 +/- 1.5 degrees C). Only the difference in relative air humidity of the dental surgery was statistically significant. With the application of a rubber dam the relative air humidity and temperature were essentially the same as the dental surgery conditions. It is concluded that without rubber dam the intraoral environment in which bonding procedures are to be performed is comparable with a high humidity climate such as that of Central Africa or the South Pacific.

A 4-year clinical evaluation of extensive amalgam restorations--description of the failures.

The 4-year evaluation of a randomized controlled clinical trial to the functioning of Extensive Amalgam Restorations (EAR) is reported. In this trial 300 EAR were made by three operators on molar teeth. Five different auxiliary retention methods were used to retain these restorations. In the evaluation a differentiation in 'absolute' and 'relative' failures was made. After 4 years seven absolute failures (EAR dislodged or removed) were encountered (2%). When relative failures (endodontic treatment or restoration at margin) are also taken into account the number of failures increased to 31 (10%). Due to the low number of failures, no significant influences from experimental variables (c.q. retention method or operator) could be detected. It may be concluded that the results of this interim analysis of the clinical functioning of EAR are promising. It is thought that careful evaluation of cusp strength and reducing weak cusps diminishes clinical failure and as a result, it is not necessary to protect an EAR with a cast restoration in the first 4 years of its clinical life.

Air humidity: a detrimental factor in dentine adhesion.

Successful dentine adhesion may be negatively influenced by intrinsic and extrinsic dentine wetness. Testing the influence of high humidity levels during the application of bonding systems is therefore relevant. It was the aim of this study to investigate in vitro the sensitivity to air humidity of the dentine bond strength for some commercially available bonding systems. Four bonding systems were tested in vitro on human molars at temperature/humidity levels of 25 degrees C and 40% relative humidity (RH) as well as 35 degrees C and 95% RH. Four operators each made two samples of the respective treatment combinations. After shear bond testing a three-way ANOVA was carried out. Only the factors 'material', 'humidity' as well as their interaction were statistically significant. The factor 'operator' did not exert a significant influence on the shear bond strength. For the 'clinically dry' group statistically significant differences were found between all materials (P < 0.001). In the 'high humidity' setting too, significant differences were found between materials (P < 0.001). The shear bond strength values ('high humidity') were very low (< 3 MPa) for Gluma 2000, Denthesive and Syntac, while the mean values for Scotchbond Multi-Purpose were significantly higher (12 MPa; P < 0.001). It was concluded that in general bonding systems are highly sensitive to extrinsic dentine wetness, resulting in very low adhesion values at high humidity.

Esthetic veneering of amalgam restorations with composite resin--combining the best of both worlds?

Patients are becoming more and more aware of the esthetic alternatives to dental amalgam and are asking dentists to offer solutions that are more esthetically pleasing. However, the difficulties in inserting clinically durable composite resin restorations in the posterior area are numerous. With the high-copper amalgam systems, the dental profession has had an excellent restorative material. In the past there have been attempts to combine amalgam with the esthetic qualities of composite resin. The introduction of an adhesive and opaque light-curing glass-ionomer liner has created new opportunities to bond composite resin to existing amalgam restorations on esthetically disturbing surfaces. This paper describes a simple and quick way in which unesthetic buccal and occlusal extensions of amalgam restorations can be veneered with composite resin. Preliminary six-month results of about 100 restorations are presented. This method may prevent the premature replacement of good functioning amalgam restorations with porcelain-fused-to-metal crowns or composite resin restorations for only esthetic reasons.

Fabrication times for indirect composite resin restorations.

Fabrication times for indirect posterior composite resin restorations were recorded in a prospective clinical efficacy study. Four operators completed 132 one-visit inlays and onlays utilizing a new indirect posterior composite resin system (ICS). The mean time needed for the fabrication of one ICS restoration was 90 min, including the 'laboratory time'. When two restorations were provided simultaneously, the overall mean fabrication time was 120 min. The fabrication times were significantly influenced by the operator and the number of restorations. In several clinical phases a 40 per cent difference in mean fabrication time could be identified between operators. The extent of the restoration had no influence on mean fabrication time. The results of this study are considered to provide some indication of the cost-effectiveness of ICS restorations.

Transverse resistance of composite resin restorations on dentin.

The transverse resistance of a dentin-bonded composite resin restoration was tested. Dentin and enamel surfaces of human molars were pre-treated differently. The specimens were stored for various periods. The presence of enamel led to a transverse resistance significantly higher than when only dentin was present. When enamel was present, additional etching of dentin gave a lower resistance. This was possibly caused by the formation of a soluble monite precipitate. Etching of dentin without the presence of enamel gave a value significantly higher than the bond strength to unetched dentin.

[Dowel and core systems for endodontically treated molars--in vitro loading]. / De opbouw voor endodontisch behandelde molaren. Een onderzoek naar de in vitro belasting.

The restoration of broken down pulpless molar teeth generally implies the provision of a cast post and core with a crown. In this experiment the failure resistance of some restoration methods utilizing amalgam and composite resin was investigated under an oblique load. Significant differences could be detected between the cast dowel and core, the methods utilizing composite resin and the methods utilizing amalgam. All systems could resist forces of more than 1000 Newton.