الفهرس 
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Abstract
This study was conducted to compare between two types of thermoformed resins: (polyamide and acetal) and the conventional heat-cured PMMA in respect to the efficacy of four finishing techniques on the surface roughness of the materials under study; as well as, the difference in adaptation between tested materials.
Thirty-six specimens; for each evaluation, were prepared, twelve specimens in each group.
Three groups were categorized:
group A: Heat-cured polymethyl methacrylate: Acrostone.
group B: Thermoformed Polyamide: NEWULTRA.
group C: Thermoformed Acetal: Bio Dentaplast.
The results of surface roughness evaluation on specimens in this study proved that:
1-Polishing technique no.1 which used fine pumice with wet rag wheel, 1500 rpm for two minutes; caused no significant difference in surface roughness between tested materials.
2-Polishing technique no. 2 which is the same as technique no. 1 but followed by tripoli compound with wet rag wheel, 1500 rpm for two minutes), technique no. 3 (pre polishing rubberizing with brown rubber disc 1500 rpm for one minute, followed by fine pumice with wet rag wheel, 1500 rpm for two minutes) and technique no. 4 which is the same as technique no.3 but followed by fine pumice with wet rag wheel, 1500 rpm for two minutes, then with tripoli compound with dry rag wheel, 1500 rpm for two minutes); caused a significant difference.
The results of adaptation evaluation in this study proved that all the tested materials showed a significant difference after immersion in distilled water for different time intervals: 24 hours, 48 hours and 12 days with the highest significant values after 24 hours and 12 days.
Eighteen patients were selected under inclusion and exclusion criteria, partially removable dentures were made of the tested materials according to groups, six patients in each group:
group 1: Patients received conventional heat-cured PMMA (Acrostone) removable partial denture.
group 2: Patients received thermoformed polyamide (NEWULTRA) removable partial denture.
group 3: Patients received thermoformed acetal (Bio Dentaplast) removable partial denture.
- Dentures were polished by the two polishing techniques which caused the least surface roughness in specimen’s evaluation. In each group, three patients had their dentures polished with technique no. 3 and the others three patients with technique no. 4.
Evaluation of bacterial counting was conducted before denture wearing and after six months of denture wearing. Swabs were taken from the palate of the patients and bacteria were counted.