Clinical evaluation and microstructural analysis of a direct placement gallium restorative alloy

Dimensional change of a calcium aluminate cement for posterior restorations in aqueous and dry media

OBJECTIVES

A calcium aluminate cement has recently been developed, with claims of being an alternative to dental amalgam and resin composites in posterior cavities. However, its' mechanical properties are not well evaluated and the aim of the study was therefore, to evaluate its' dimensional stability over time.

METHODS

The dimensional changes of the cement, Doxadent, and two composite resins, Esthet-X and InTen-S, were tested during 360 d. The specimens were stored at 37+/-1 degrees C either in 100% air humidity (dry) or immersed in distilled water (wet), except for the first 24h when all specimens were stored at 100% air humidity and 37+/-1 degrees C.

RESULTS

During the first 24h, Doxadent decreased in volume with 0.04%, while InTen-S and Esthet-X decreased with 1.60 and 1.75%, respectively. From d 1-360, the dry Doxadent specimens increased in volume with 2.0% and in weight with 5.5%, while the corresponding increase for the wet specimens were 4.1 and 6.3%, respectively. The volume of both composites increased 0.8% or less in dry and wet conditions, while the increase in weight for InTen-S was 1.2% for the wet specimens and 0.6% for the dry. The corresponding figures for Esthet-X were 0.7 and 0.2%.

SIGNIFICANCE

Doxadent was less dimensionally stable than the composites tested. Doxadent increased 2 times more in volume immersed in water than in 100% air humidity, while the increase in weight was almost similar. The clinical implications of the results found in the present study are uncertain. A material that continues to absorb water during prolonged periods and continues to react is questionable for clinical use.

A 3-year longitudinal, controlled clinical study of a gallium-based restorative material

AIM

The aim of this three-year longitudinal controlled study was to compare the clinical performance of Galloy versus a high copper, mercury based Dispersalloy filling material.

METHODS

Moderate to large class I and class II cavities or replacement restorations were selected and 25 Galloy restorations and 25 Dispersalloy controls were placed in 14 adult patients by a single operator. Restorations were photographed and a silicone impression recorded at baseline, 6 months, 1 year, 2 years and 3 years.

RESULTS

At 3 years all 22 Dispersalloy restorations but only 4 Galloy restorations were still in situ. Three Dispersalloy restorations were lost to follow-up. Tooth fracture was observed in 15 (60%) of the Galloy restorations by the end of the 3 years, compared to one (4%) Dispersalloy restoration, which failed due to tooth fracture. A further six Galloy restorations had to be removed due to complaints of persistent pain. Four teeth restored with Galloy required endodontic treatment but none of the Dispersalloy restored teeth required endodontics. Of the four Galloy restorations remaining in situ, three were relatively small restorations and the fourth a moderate sized restoration required a marginal repair.

CONCLUSION

The clinical performance of Galloy restorations was so grossly inferior to the Dispersalloy controls that Galloy cannot be recommended for clinical use in moderate to large or multi-surface cavities.

A 3-year clinical evaluation of a gallium restorative alloy

Several alternative materials have been suggested to take the place of amalgam, because of the environmental toxic effects of its mercury component. One such material is gallium-based alloy restoratives. The aim of this in vivo study was to compare the long-term clinical performance of a commercial gallium alloy with an admixed high copper amalgam alloy. For this purpose, 32 gallium and 32 amalgam restorations were placed in molar teeth in 14 human subjects. All the selected patients had at least two molar teeth that required restoration. In this way both restoratives were used in the same oral cavity. The restorations were examined at baseline, 6 months, 1, 2 and 3 years. At baseline, six teeth restored with gallium alloy showed post-operative sensitivity, whereas none of the amalgams were sensitive. At the end of 3 years, only a few amalgam restorations showed slight surface tarnish and marginal integrity loss. None of them needed replacement. Of the 32 gallium restorations placed, five had to be removed because of sensitivity, corrosion and tooth fracture. Also dramatic surface roughness and corrosion were noticed in 12 gallium restoration. According to the results of this clinical study, gallium-based restoratives should not be used before their physical properties are improved.

[Dimensional changes of silver and gallium-based alloy]

Gallium-based dental alloys were created with the aim of solving the problem of toxicity of mercury. The material shows mechanical properties similar to those of dental amalgam, but researches point out two unfavorable characteristics: great corrosion and excessive post-setting expansion, and the latter is capable of cracking dental structures. The aim of this study was to evaluate, during 7 days, the in vitro dimensional alteration of a gallium dental alloy (Galloy, SDI, Australia), in comparison with a dental amalgam containing zinc (F400, SDI, Australia), as a function of the contact with saline solution (0.9% NaCl) during the setting period. The storage experimental conditions were: storage in dry environment, immersion in saline solution and contamination during condensation. Additionally, the effects of contamination during the trituration of dental amalgam and the effects of protecting the surface of the gallium alloy with a fluid resin were studied. Specimens were stored at 37 degrees C +/- 1 degree C, and measuring was carried out, sequentially, every 24 h during 7 days. When the gallium alloy was either contaminated or immersed, an expansion significantly greater than that observed in the other experimental conditions was noticed after 7 days. The application of a fluid resin to protect the surface of the cylinders was able to avoid the increase in expansion caused by superficial moisture. The amalgam alloy did not show significant dimensional alterations, except when it was contaminated during trituration.