Biomedical subjects

Renata Cunha Matheus Rodrigues Garcia

Publications and source records attributed to Renata Cunha Matheus Rodrigues Garcia.

6 recordsLinked to original sources

PubMed2006

Influence of acrylic resin polymerization methods and saliva on the adherence of four Candida species.

STATEMENT OF PROBLEM: There is limited information on the role of polymerization methods and saliva on the adherence of pathogenic Candida species, with the exception of the adherence of Candida albicans to acrylic resins and the relation of this to surface roughness and surface free energy, which appear to play a major role in the initial phases of microorganism adhesion. PURPOSE: This study evaluated the influence of polymerization methods and human whole saliva on the adherence of Candida species to acrylic resin surfaces. MATERIAL AND METHODS: Acrylic resin specimens (n=256) measuring 2.5 x 1.2 x 0.2 cm were heat (Classico) or microwave (OndaCryl) polymerized and evaluated for surface roughness using a profilometer, and for surface free energy by measuring the contact angle of a sessile drop of water. For the adherence assay, specimens of each acrylic resin were divided by lottery into 8 groups, according to whether they were exposed to human saliva or not (control), and to 1 of the 4 following suspensions: C albicans, Candida tropicalis, Candida dubliniensis, or Candida glabrata (1 to 5 x 10(6) cells/mL). Adhered yeasts were counted using an optical microscope at x400 magnification. Data were analyzed by 3-way ANOVA and the Tukey honestly significant difference test (alpha=.05). RESULTS: No statistical difference was found for roughness (P=.156), whereas higher surface free-energy values were found for the heat-polymerized acrylic resin (P=.0013). The overall adherence of Candida species was significantly decreased by human saliva (P<.001). CONCLUSION: Within the limitations of this study, saliva was capable of reducing the adherence of Candida species, whereas roughness and free energy did not influence the adherence rates. CLINICAL IMPLICATIONS: As growth on surfaces is a natural part of the Candida lifestyle, its colonization in denture users may be expected. The presence of human whole saliva, however, decreased the overall yeast adherence to the acrylic resin surface, whereas surface roughness and free energy did not interfere with the adherence of Candida species.

Acrylic Resins↗

PubMed2005

Signs and symptoms of temporomandibular disorders in adolescents.

The aim of this study was to verify the prevalence of signs and symptoms of temporomandibular disorders (TMD) in adolescents and its relationship to gender. The sample comprised 217 subjects, aged 12 to 18. The subjective symptoms and clinical signs of TMD were evaluated, using, respectively, a self-report questionnaire and the Craniomandibular Index, which has 2 subscales; the Dysfunction Index and the Palpation Index. The results of muscle tenderness showed great variability (0.9-32.25%). In relation to the temporomandibular joint, tenderness of the superior, dorsal and lateral condyle regions occurred in 10.6%, 10.6% and 7.83%, respectively, of the sample. Joint sound during opening was present in 19.8% of the sample and during closing in 14.7%. The most prevalent symptoms were joint sounds (26.72%) and headache (21.65%). There was no statistical difference between genders (p > 0.05), except for the tenderness of the lateral pterygoid muscles, which presented more prevalence in girls. In conclusion, clinical signs and symptoms of TMD can occur in adolescents; however, gender influence was not perceived.

Adolescent↗

PubMed2005

Water sorption, solubility, and tensile bond strength of resilient denture lining materials polymerized by different methods after thermal cycling.

STATEMENT OF PROBLEM: The clinical properties of resilient denture lining materials may be influenced by the methods used to polymerize them. PURPOSE: This study evaluated and compared water sorption, solubility, and tensile bond strength of 2 resilient liner materials polymerized by different methods after being thermal cycled. MATERIAL AND METHODS: Two acrylic resin-based resilient liner materials were evaluated: 1 (Light Liner) polymerized by visible light, and 1 (Ever-Soft) processed by 2 different methods: hot water bath and microwave energy. To evaluate water sorption and solubility, 10 disc-shaped specimens (50 x 0.5 mm) were fabricated for each polymerization method, using acetate matrices. The specimens were dried and thermal cycled (2000 cycles) between baths of 5 degrees C and 55 degrees C. After thermal cycling, the specimens were weighed, dried, and weighed again to calculate the water sorption values and solubility. For tensile bond strength assessment, 12 rectangular specimens measuring 83 mm in total length and with a cross-sectional area of 10 x 10 mm were fabricated using each polymerization method. The specimens were also thermal cycled (2000 cycles) and, afterwards, tested in a universal testing machine at a crosshead speed of 6 mm/min with 100 Kg load cell. The type of failure was determined by use of stereoscopic microscopy. The data (for water sorption and solubility, n = 30, and for tensile bond strength, n = 36) were submitted to 1-way analysis of variance. The means were compared using the Bonferroni test (alpha=.05). RESULTS: For water sorption the results showed no significant differences among the polymerization methods. Light Liner showed the lowest solubility values (5.3% +/- 0.3%) when compared to Ever-Soft (hot water bath: 7.3% +/- 1.1% and microwave energy: 7.8 +/- 0.9%). For tensile bond strength, Ever-Soft polymerized by microwave energy (0.7 +/- 0.0 MPa) showed the greatest and most significant ( P <.05) value when compared to Ever-Soft polymerized by hot water bath (0.5 +/- 0.1 MPa) and Light Liner polymerized by visible light (0.5 +/- 0.0 MPa). Most Ever-Soft specimens polymerized by microwave energy and Light Liner specimens showed adhesive/cohesive failures. However, Ever-Soft polymerized by hot water bath showed 50% adhesive/cohesive and 50% adhesive failures. The results at the reline material-resin bond interface showed the absence of cohesive failures. CONCLUSION: Within the limitations of this study, Light Liner showed the lowest solubility values. Ever-Soft should be polymerized by microwave energy to obtain the greatest tensile bond strength values. Materials polymerized by microwave energy and visible light showed predominantly adhesive/cohesive failures.

Absorption↗

PubMed2004

Polymerization time for a microwave-cured acrylic resin with multiple flasks.

This study aimed at establishing the polymerization time of a microwave-cured acrylic resin (AcronTM MC), simultaneously processing 2, 4, and 6 flasks. Required time was measured according to the parameters: monomer release in water, Knoop hardness, and porosity. Samples were made with AcronTM MC in different shapes: rectangular (32 x 10 x 2.5 mm) for monomer release and porosity; and half-disc (30 mm in diameter x 4 mm in height) for Knoop hardness. There were four experimental groups (n = 24 per group): G1) one flask (control); G2) two flasks; G3) four flasks, and G4) six flasks. At first, polymerization protocol was similar for all groups (3 min/450 W). Time was then adjusted for G2, G3, and G4, based on monomer release evaluation in the control group, obtained by spectrophotometer Beckman DU-70, with emitting wave of 206 nm. Knoop hardness test was performed using a Shimadzu HMV 2000 hardness tester, and 10 indentations were performed on each specimen's surface. Porosity was assessed after specimens were immersed in black ink and the pores counted in a microscope. Results showed that the complete polymerization of the resin occurred in 4.5 min for two flasks (G2); 8.5 min for four flasks (G3); and 13 min for six flasks (G4), all with 450 W. Statistical analysis revealed that the number of flasks does not interfere with polymerization, Knoop hardness, and porosity of the resin. Results showed that polymerization of microwave-curing resin with more than one flask is a viable procedure, as long as polymerization time is adjusted.

Acrylic Resins↗

PubMed2004

Effect of denture cleansers on the surface roughness and hardness of a microwave-cured acrylic resin and dental alloys.

PURPOSE: This study evaluated the effect of denture cleansers on the surface hardness of a denture base resin, and on the surface roughness of the resin and Co-Cr and Ti-6Al-4V alloys. MATERIALS AND METHODS: Forty-eight disc-shaped specimens were fabricated of a microwave-cured acrylic resin, each having one of the alloys attached to its surface. The specimens were randomly divided into 6 groups, each consisting of 8 samples. Specimens were exposed to one of the three cleansing treatments (polident, manipulation pharmacy cleanser, and water) as follows. Group I: Co-Cr + polident; Group II: Co-Cr + manipulation; Group III: Co-Cr + water; Group IV: Ti-6Al-4V + polident; Group V: Ti-6Al-4V + manipulation; and Group VI: Ti-6Al-4V + water. Three exposures lasting 5 minutes each were conducted daily, and repeated after storage periods of 1, 14, and 29 days in artificial saliva at 37 degrees C. Hardness and roughness measurements were undertaken immediately after specimen preparation (T0) and on the 1st (T1), 15th (T15), and 30th (T30) day following the beginning of storage. Three roughness and hardness evaluations were carried out for each sample and testing time, and mean values were calculated. Results were analyzed using ANOVA and linear regression. RESULTS: The Knoop hardness test demonstrated differences (p < 0.05) between Groups I and IV at T1 and T30 (14.30 +/- 2.78; 14.06 +/- 1.76) and between Groups II and V at T15 (16.99 +/- 2.24). Significant differences (p < 0.05) in resin roughness (in microm) were observed between Groups I and IV at T15 and T30 (0.14 +/- 0.06; 0.21 +/- 0.38). With regard to Co-Cr, roughness data showed differences (p < 0.05) for all groups at T30 (Group I: 0.15 +/- 0.07; Group II: 2.43 +/- 0.66; Group III: 4.05 +/- 1.03), for Group II at T1 (0.10 +/- 0.03), and for Group I at T15 (0.15 +/- 0.02). There were significant differences (p < 0.05) in titanium roughness for Group IV at T15 (0.12 +/- 0.01) and T30 (0.11 +/- 0.04). CONCLUSIONS: Manipulated cleanser containing sodium perborate increased surface roughness and hardness, probably due to its incapacity to remove the pellicle formed on the acrylic resin and dental alloys.

Acrylic Resins↗

PubMedDate not supplied

Effect of new dentures on interocclusal distance during speech.

PURPOSE: The aim of this study was to investigate the changes in interocclusal distance during the pronunciation of /m/ and /s/ sounds in the Portuguese language, in partially edentulous patients before and after insertion of new dentures. MATERIALS AND METHODS: Subjects were divided into a control group consisting of 18 completely dentate patients and an experimental group consisting of 18 patients who were edentulous in the maxilla and classified as Kennedy Class I in the mandible. The experimental group had new dentures placed and the occlusal vertical dimension corrected. A magnetic jaw-tracking device measured the interocclusal distance during pronunciation of the /m/ and /s/ phonemes. Interocclusal distance evaluations were carried out in a single session for the control group. In the experimental group, the measurements were carried out before insertion of new dentures; immediately after insertion; and after 6 and 24 hours; 2 days; 1 and 2 weeks; 1, 2, 3, and 6 months; and 1 year. RESULTS: Comparison between groups revealed significant difference in interocclusal distance for the /m/ sound both before and after insertion of dentures up to 2 months. For the /s/ phoneme, there was no difference between the groups before prosthesis insertion, or after 3, 6, and 12 months of prosthesis use. There were significant differences for the /m/ sound only at 6 and 12 months after new denture insertion, and for the /s/ sound at all periods evaluated. CONCLUSION: Insertion of new dentures, with the vertical dimension corrected, changes the interocclusal distance of speech during phonation of /m/ and /s/ sounds.

Adult↗