Water sorption and solubility of polyamide denture base materials

Abstract

Purpose: Some patients experience adverse reactions to poly(methyl methacrylate)-based (PMMA) dentures. Polyamide (PA) as an alternative to PMMA has, however, not been well documented with regard to water sorption and water solubility. The aim of this in vitro study was to measure water sorption and water solubility of two PA materials compared with PMMA, and to evaluate the major components released from the PA materials and the effect on hardness of the materials. Methods: Ten discs (40.0 mm diameter, 2.0 mm thick) of each material (PA: Valplast and Breflex; PMMA: SR Ivocap HIP) were prepared according to manufacturers’ recommendations. The specimens were tested for water sorption and water solubility, according to a modification of ISO 20795-1:2008. Released substances were analysed by gas chromatography/mass spectrometry (GC/MS). Results: There were statistically significant differences among the materials regarding water sorption, water solubility and time to water saturation. Breflex had the highest water sorption (30.4 μg/mm3), followed by PMMA-material (25.8 μg/mm3) and Valplast (13.6 μg/mm3). Both PA materials had statistically significant lower water solubility than the PMMA. Both PA had a net increase in weight. Analysis by GC/MS identified release of the compound 12-aminododecanolactam from the material Valplast. No release was found from the Breflex material. Conclusions: The PA denture materials show differences in water sorption and solubility, but within the limits of the standard requirements. The PA showed a net increase in weight after long-term water sorption. The clinical implications of the findings are not elucidated.

Patient and Clinical Evaluation of Traditional Metal and Polyamide Removable Partial Dentures in an Elderly Cohort

“…Nonetheless, it should be noted that in some studies RPD performances, such as those related to masticatory efficiency, have been evaluated even after 5 or 6 months, suggesting that 1 year postevaluation can already provide some useful information . In addition, mechanical properties of VALPLAST and PMMA can change even earlier (within 8 weeks), due to water sorption and solubility, as reported by Nguyen and coworkers . Another limitation is that no data on bone loss in edentulous segments were reported.…”

“…Nonetheless, it was also found that VALPLAST‐RPD was characterized by increased difficulty in prosthesis care and roughness perceived by the tongue. Polyamide material is subjected to faster degradation and lower wear resistance as compared to PMMA and CoCR . This may also contribute to increased damage of the surface when cleaning, also causing the roughness of prosthesis.…”

“…Decreased retention was also observed for VALPLAST‐RPD. This finding can be related to the characteristic of the material, which is more subjected to water uptake, with consequent changes in the retention area . Water absorption may break the chemical bond, with detrimental effects on the mechanical property of the material, and may contribute to artificial teeth loss.…”

“…Polyamide material is subjected to faster degradation and lower wear resistance as compared to PMMA and CoCR. 7,16,17 This may also contribute to increased damage of the surface when cleaning, 18 also causing the roughness of prosthesis. An increased roughness surface may also favor plaque/calculus accumulation over time 15 and increased candida infection, as reported by other authors.…”

“…29 In addition, mechanical properties of VALPLAST and PMMA can change even earlier (within 8 weeks), due to water sorption and solubility, as reported by Nguyen and coworkers. 17 Another limitation is that no data on bone loss in edentulous segments were reported. The reason is that bone loss requires more observation time and more accurate images to be assessed correctly.…”