Viviane Maia Barreto Oliveira

Effect of a denture cleanser on weight, surface roughness, and tensile bond strength of two resilient denture liners

STATEMENT OF PROBLEM Denture cleansers used in clinical practice can damage resilient denture lining materials. PURPOSE This study evaluated the effects of a denture cleanser on weight change, roughness, and tensile bond strength on 2 denture resilient lining materials. MATERIAL AND METHODS Forty specimens of microwave acrylic resin (Onda-Cryl), 30 mm in diameter and 4 mm thick, were prepared to verify weight change and surface roughness. The specimens were divided into 4 groups consisting of 10 specimens each, relined with a resilient liner (Coe Soft or Dentusoft), and treated (Polident or tap water). To evaluate tensile bond strength, 12 specimens were used for each group. All specimens were stored in artificial saliva for 15 days, immersed once a day in Polident or tap water, and evaluated at 0 hours and after 24 hours and 7 and 15 days. Roughness was evaluated by use of a profilometer. Weight changes were recorded in milligrams and expressed as the percentage of weight difference between the periods of evaluation. Tensile bond strength was determined with a universal testing machine. The specimens were placed under tension until failure by a cross-speed of 5 mm/min with a 500 Kg load cell. The type of failure was determined by use of stereoscopic microscopy at original magnification x8. The data were submitted to analysis of variance and compared by Tukeys test (alpha=.05). RESULTS Specimens immersed in Polident showed higher and significant (P<.05) weight changes (%) than those immersed in water between 24 hours and 7 days (Coe Soft-Polident: 0.48 +/- 0.09; Coe Soft-water: 0.28 +/- 0.09; Dentusoft-Polident: 0.44 +/- 0.16; Dentusoft-water: 0.22 +/- 0.15) and between 7 and 15 days (Coe Soft-Polident: 0.08 +/- 0.04; Coe Soft-water: -0.17 +/- 0.05; Dentusoft-Polident: 0.01 +/- 0.04; Dentusoft-water: - 0.24 +/- 0.03). There was significant difference (P<.05) in roughness (in micrometers), between treatments after 7 days (Coe Soft-water: 4.07 +/- 0.22; Coe Soft-Polident: 3.36 +/- 0.52; Dentusoft-water: 3.68 +/- 0.72; Dentusoft-Polident: 3.26 +/- 0.41) and 15 days (Coe Soft-water: 4.88 +/- 0.29; Coe Soft-Polident:3.53 +/- 0.61; Dentusoft-water: 4.42 +/- 1.12; Dentusoft-Polident: 3.68 +/- 0.37). Tensile bond strength was highest (P<.05) after 15 days (Coe Soft-water: 5.19 +/- 0.93; Coe Soft-Polident: 4.40 +/- 0.38; Dentusoft-water: 4.42 +/- 1.15; Dentusoft-Polident: 4.84 +/- 1.14). Most failures were cohesive (Coe Soft: 76.04% and Dentusoft: 82.29%). CONCLUSION Within the limitations of this in vitro study, specimens immersed in Polident demonstrated increased weight changes of resilient liners when compared with tap water, but surface roughness and tensile bond strength were unaffected.

In vivo assessment of the effect of an adhesive for complete dentures on colonisation of Candida species

OBJECTIVE Denture adhesives have long been recognised by denture wearers as a useful adjunct to denture retention and stability. The objective of the present study was to evaluate, in vivo, the effect of a denture adhesive on oral quantities of Candida species by determination of absolute counts of colony-forming units (CFU) per ml of saliva of individuals who use this denture adhesive for a period of 14 days. MATERIALS AND METHODS Twenty-four individuals were randomised in two equal groups of 12 (test and control), with the individuals of the test group using the adhesive for 14 days. Samples of saliva were collected from all individuals on days 0 (initial), 7 and 14. Aliquots of saliva were diluted and plated in duplicate on Sabouraud dextrose agar with chloramphenicol and incubated for 37 °C for 48 h, the CFU/ml were counted in the individuals of each group and the data of each group were compared at the different time periods and analysed statistically by the non-parametric Mann-Whitney U-test (α ≤ 5%). RESULTS There were no statistically significant differences between the test and control groups during the test periods. CONCLUSION Within of the limitations of this study, the data suggested that the denture adhesive tested did not significantly alter the oral microbiota during the 14-day trial period.

Short term evaluation of interocclusal distance during speech after new removable prosthesis insertion

The aim of this study was to evaluate the interocclusal distance during the pronunciation of /m/ and /s/ sounds from Portuguese Language, in partially edentulous patients before and after new partial and total prosthesis installation. The subjects were divided into two groups: Experimental group, consisting of 9 patients entirely edentate in the upper maxillary arch and classified as Kennedy Class I in the lower arch; and Control group, consisting of 9 totally dentate patients. The subjects from the first group had their worn out dentures changed and the occlusal vertical dimension (OVD) corrected. A magnetic method of jaw tracking was used to measure the interocclusal distance (mm) during pronunciation of those phonemes. Comparison between groups, by t test, showed significant difference (p<0.05) for /m/ sound in all periods of time: before prosthesis installation - T0 (3.38±1.23), immediately - T1 (2.15±1.06), six hours - T2 (3.41±1.33), twenty-four hours - T3 (2.92±0.92), two days - T4 (4.80±1.93), one week - T5 (3.87±1.43), two weeks - T6 (3.03±0.96), one month - T7 (3.03±0.96), two months - T8 (4.47±1.45) and three months - T9 (4.33±2.56), except for six months - T10 after prosthesis installation. For /s/ sound phoneme the results were different (p<0.05) between the groups in T1 (2.89±1.33), T2 (3.37±1.22), T3 (3.19±1.06), T4 (3.86±1.21), T5 (3.83±1.32), T6 (3.27±1.10), T7 (3.37±0.99) and T10 (3.84±1.38) after oral rehabilitation. The paired-t test, for means comparison between before and after prosthesis insertion, indicated significant differences (p<0.05) for /m/ sound only in T1, and for /s/ sound in T1, T2, T3, T6, T7 and T10. It was concluded that new prosthesis insertion, correcting the OVD, changes the interocclusal distance, and for /m/ sound this distance could be recovered after six months of prosthesis wearing.

CEMENTED OR SCREW RETAINED PROSTHESIS ON IMPLANTS: CLINICAL APPLICABILITY

| The evolution of implant dentistry relates to the constant progress of rehabilitation. The correct selection of prosthetic components is crucial to the success and longevity of treatment. The type of implant retention aids can be divided into cemented or screwed, and their choice depends mainly on the clinical situations presented. In both types of retention is observed that there are advantages and disadvantages in their use, however, we must have scientific knowledge about its characteristics in order to select the proper restraint system. Thus, the objective of this study is to review the literature that addresses the cemented and screwed prostheses, facilitating their clinical indication.