Conclusions

From statistical analysis of the results of the study, the following conclusions may be drawn in terms of its overall aim and specific objectives:

6.3.1 Overall aim

The results indicated that both surface treatments, and the composition of the medium in which the specimens were submersed, were successful in reducing either the sorption or solubility level recorded by the specimens. The analysis of the results suggests that overall, mechanical polishing was the most effective surface treatment procedure and that artificial saliva was the medium in which the specimens recorded the lowest sorption and solubility values.

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Objectives one and two were established to determine the sorption and solubility of heat-cured acrylic with no surface treatment soaked in distilled water and artificial saliva. The specimens soaked in artificial saliva recorded lower sorption and solubility values than the specimens soaked in distilled water. The reductions in both sorption and solubility were deemed to be statistically significant. The null hypothesis relating to objectives one and two was therefore accepted.

Objective three was established to determine the effect of mechanical polishing on the sorption and solubility of heat-cured acrylic soaked in distilled water. The specimens that were mechanically polished and soaked in distilled water recorded lower mean sorption and solubility values than the sample group which received no surface treatment, soaked in distilled water. Only the reduction in sorption was deemed to be statistically significant. The null hypothesis relating to objective three was therefore rejected.

Objective four was established to determine the effect of mechanical polishing on the sorption and solubility of heat-cured acrylic soaked in artificial saliva. The specimens that were mechanically polished and soaked in artificial saliva recorded lower mean solubility but higher mean sorption values than the sample group which received no surface treatment, soaked in artificial saliva. Neither the sorption nor the solubility values recorded were deemed to be statistically significant. The null hypothesis relating to objective four was therefore partially accepted.

Objective five was established to determine the effect of a light-cured varnish on the sorption and solubility of heat-cured acrylic soaked in distilled water. The specimens that were treated with the light-cured varnish and soaked in distilled water recorded lower mean sorption, but higher mean solubility values than the sample group which received no surface treatment, soaked in distilled water. Only the reduction in sorption was deemed to be statistically significant. The null hypothesis relating to objective five was therefore partially accepted.

Objective six was established to determine the effect of a light-cured varnish on the sorption and solubility of heat-cured acrylic soaked in artificial saliva. The specimens that were treated with the light-cured varnish and soaked in artificial saliva recorded lower mean sorption, but higher mean solubility values than the sample group which received no surface treatment, soaked in artificial saliva. Only the increase in solubility was deemed to be statistically significant. The null hypothesis relating to objective six was therefore partially accepted.

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Objective seven was established to determine which surface treatment results in the least sorption and solubility of the heat-cured acrylic. The specimens that were treated with the light- cured varnish recorded lower mean sorption, but higher mean solubility values than the specimens that were mechanically polished. Both the lower sorption and higher solubility values recorded by the specimens that were treated with the light-cured varnish were statistically significant. The null hypothesis relating to objective seven was therefore partially accepted.

Finally, objective eight was established to determine which medium results in the least sorption and solubility of heat-cured acrylic. The specimens soaked in artificial saliva recorded lower sorption and solubility values than the specimens soaked in distilled water, but only the reduction in solubility was deemed to be statistically significant. The null hypothesis relating to objective eight was therefore accepted.

6.3.3 Overall conclusions

i. The application of surface treatments to Vertex™ Rapid Simplified heat-cured acrylic had a significant effect on the material’s sorption and solubility properties.

ii. Mechanical polishing of prostheses fabricated from Vertex™ Rapid Simplified heat- cured acrylic will reduce their sorption and solubility, but the reduction cannot be expected to be statistically significant.

iii. The application of Optiglaze™ light-cured varnish to prostheses fabricated from Vertex™ Rapid Simplified heat-cured acrylic will significantly reduce the sorption of the material but will also result in significantly higher solubility values.

iv. When mechanical polishing is compared to Optiglaze™ light-cured varnish as a surface treatment, the sorption and solubility results indicate that mechanical polishing may be a more well-rounded surface treatment option.

v. Optiglaze™ light-cured varnish may be considered as an alternative surface treatment to mechanical polishing or used in conjunction with it as the sorption and solubility levels recorded were within the thresholds stipulated by ISO.

vi. The results indicate that the molecular composition of the medium in which the material is soaked affects the levels of sorption and solubility recorded. This suggests that the sorption and solubility properties of the material during function in the oral cavity may differ from those recorded during standardised tests.

vii. The results from this study and other comparable research indicate that denture wearers may benefit from having their prostheses cleaned and polished by a trained professional at calculated intervals.

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