Randomized clinical trial of complete denture cleaning methods in residents of care institutions

Aim: To evaluate the efficacy of ultrasonic bath and traditional brushing in the hygiene of complete dentures of dependent residents in long-term care institutions (LTCIs). Methods: A randomized cross-over clinical study was conducted in 17 maxillary complete denture wearers living in LTCIs. Cleaning protocols were brushing or ultrasonic bath, both applied with neutral liquid soap. Biofilm biomass were estimated by MTT reduction assay and specific microbial load (CFU) of Streptococcus spp., Staphylococcus spp. and Candida spp. were quantified by selective and differential culture media. Results: Ultrasound method showed higher percentage reduction of biofilm biomass and specific microbial loads of Streptococcus spp. compared to brushing (p<0.01). Reduction of microbial loads of the other microorganisms were not different between cleaning methods (p>0.05). Conclusions: The ultrasonic bath proved to be a feasible alternative method for the mechanical cleaning of complete dentures in LTCIs

Determination of final occlusal vertical dimension by cephalometric analysis

Introduction: Most of techniques for determining the occlusal vertical dimension (OVD) of edentulous patients are based on soft tissues references, which lead to measurement discrepancies. Objective: To propose a method to obtain the OVD of edentulous patients during the confection of complete dentures considering the lower facial height established by Ricketts (LFHr) or the lower facial height obtained from cephalometric analysis of dentulous patients (LFHd). Material and methods: The OVD of 11 edentulous patients was determined by the association of 3 clinical methods. On each patient's bite plates a metallic ball was fixed and the patient was submitted to lateral radiographic to obtain the lower facial height (LFHe) from cephalometric analysis. Additionally, from 40 lateral cephalograms of dentulous patients the LFHd was obtained. After that, the distance between metallic balls (DMB, in mm) was calculated to verify the linear difference when LFHe was changed to LFHd or LFHr, which provided the amount of wax to be added or removed from the bite plates, establishing a new method of OVD determination. LFHe, LFHd and LFHr values were submitted to t e z statistical tests and DMB differences were analyzed by Student's t-test (α=0.05). Results: LFHr (47.0±4.0o a) was statistically higher than LFHd (44.9±5.6o b) and LFHe (43.5±3.5o b). There was statistical difference on linear discrepancies calculated between the LFHe and LFHd (1.7±4.1mm a) or LFHr (4.2±4.1mm b). Conclusion: The use of the cephalometric analysis showed to be a useful auxiliary tool in determining the intermaxillary relationship. However, this method must be associated with different clinical methods of OVD determination and it is recommended that regional references are used to calculate the linear discrepancies.

Dimensional stability of a novel polyvinyl siloxane impression technique

AIM: To introduce a modification of the reline impression technique (MRIT), and compare the dimensional changes of impressions obtained by MRIT and by conventional reline impression technique (CRIT). METHODS: An acrylic resin tablet was milled by a CAD-CAM system to simulate three abutments (A, B and C) with different distances among them. The abutments were molded using both impression techniques. For MRIT, before completing the putty silicone polymerization, the relieve procedure was made by compression and it was immediately repositioned to complete the polymerization. Impressions were stored dry at room temperature for different periods (immediately, 1 h, 2 days and 7 days). The distances were obtained by scanning. The differences between the impressions and their respective matrix reference measurements were calculated to determine the dimensional changes. Data were subjected to ANOVA and Tukey's test (p<0.05). RESULTS: For AB and BC distances, there was no statistically significant difference between CRIT and MRIT (p=0.0597 and p=0.2167, respectively). For AC, there was statistically significant difference between the techniques for the immediate storage time (p=0.006). In general, for CRIT the material showed expansion, while for MRIT it showed contraction. CONCLUSIONS: It was verified that the addition silicon impressions obtained by both impression techniques showed dimensional stability, except for the immediate time-point...

Analysis of tensile strength of poly(lactic-coglycolic acid) (PLGA) membranes used for guided tissue regeneration

Introduction: The challenge of restoring patient's function that presented some loss of an organ or tissue encourages the Tissue Engineering and Biotechnology to develop materials that promote bone regeneration. Poly(lactic-co-glycolic acid) (PLGA) copolymer is among of the most biomaterials used. Objective: To evaluate the tensile strength of PLGA membranes at different conditions of humidity and temperature. Material and methods: PLGA membranes were hourglass-shape cut and prepared at three different conditions of temperature and humidity (n = 10): (I) dry membrane at environment temperature of about 20ºC (control group), (II) moist membrane plasticized at 55ºC, (III) moist membrane plasticized at 55ºC, which subsequently underwent cooling. Subsequently, the membranes were subjected to tensile tests in a universal testing machine (DL-2000, EMIC) at 1.0 mm/min. Data was submitted to ANOVA and Tukey's test (p < 0.05). Results: Group I showed the highest tensile strength mean (16.7 ± 1.9a MPa, p = 0.0022). There was no statistically significant difference between the means of groups II (14.6 ± 1.4 MPab) and III (13.9 ± 1.7 MPab). Conclusion: The dried PLGA membranes showed higher tensile strength than the membranes that were only either plasticized or cooled.