Rosemary Sadami Arai Shinkai

Determinants of masticatory performance in dentate adults

Masticatory performance results from a complex interplay of direct and indirect effects, yet most studies employ univariate models. This study tested a multivariate model of masticatory performance for dentate subjects. Explanatory variables included number of functional tooth units, bite force, sex, age, masseter cross-sectional area, presence of temporomandibular disorders, and presence of diabetes mellitus. The population-based sample consisted of 631 dentate subjects aged 37-80 years. Covariance structure analysis showed that 68% of the variability in masticatory performance could be explained by the combined effects of the explanatory variables. Age and sex did not show a strong effect on masticatory performance, either directly or indirectly through masseter cross-sectional area, temporomandibular disorders, and bite force. Number of functional tooth units and bite force were confirmed as the key determinants of masticatory performance, which suggests that their maintenance may be of major importance for promoting healthful functional status.

Effect of microwave disinfection on denture base adaptation and resin surface roughness

This study evaluated the effect of disinfection methods [chemical disinfection (immersion in 100 ppm chloride solution) or microwave disinfection (690 W for 6 min)] on the internal adaptation of denture bases and resin surface roughness. For the adaptation test, 18 maxillary denture bases were obtained from stone casts duplicated from a metallic master model and submitted to the following treatments: 1) control (no disinfection), 2) chemical disinfection or 3) microwave disinfection. Disinfection procedures were performed twice (T1, T2) with a 7-day interval between them. Internal adaptation was measured at baseline (T0) and after T1 and T2 by weighing a vinyl polysiloxane film reproducing the gap between the resin base and the master model. For surface roughness measurement, 60 rectangular (5x10x40 mm) resin specimens were either mechanically or chemically polished and then submitted to the disinfection treatments. Surface roughness (Ra) was recorded after polishing (T0) and after T1 and T2. Data were analyzed by ANOVA GLM for repeated measures and Bonferroni correction at 5% significance level. Bases submitted to microwave disinfection had gradual increase of misfit, while bases immersed in chloride solution did not differ from the control group. Surface roughness increased in the mechanical polishing groups with microwave disinfection and decreased in the chemical polishing groups.

Salivary flow rate, pH, and concentrations of calcium, phosphate, and sIgA in Brazilian pregnant and non-pregnant women

BackgroundStudies on salivary variables and pregnancy in Latin America are scarce. This study aimed to compare salivary flow rate, pH, and concentrations of calcium, phosphate, and sIgA of unstimulated whole saliva in pregnant and non-pregnant Brazilians.MethodsCross-sectional study. Sample was composed by 22 pregnant and 22 non-pregnant women attending the Obstetrics and Gynecology Clinics, São Lucas Hospital, in Porto Alegre city, South region of Brazil. Unstimulated whole saliva was collected to determine salivary flow rate, pH, and biochemical composition. Data were analyzed by Student t test and ANCOVA (two-tailed α = 0.05).ResultsNo difference was found for salivary flow rates and concentrations of total calcium and phosphate between pregnant and non-pregnant women (p > 0.05). Pregnant women had lower pH (6.7) than non-pregnant women (7.5) (p < 0.001), but higher sIgA level (118.9 mg/L) than the latter (90.1 mg/L) (p = 0.026).ConclusionSome of the tested variables of unstimulated whole saliva were different between pregnant and non-pregnant Brazilians in this sample. Overall, the values of the tested salivary parameters were within the range of international references of normality.

Functional evaluation of oral rehabilitation with removable partial dentures after five years

Most removable partial denture (RPD) wearers are satisfied with their prostheses, but the factors that influence satisfaction and acceptance are still not determined. Objective: This study explored technical, biological, and satisfaction variables for the functioning of RPDs after five years, and compared the evaluation by the patient and by the clinician. Materials and Methods: Fifty adults (39 females, 11 males) were reexamined after five years of RPD service. Data were collected through clinical examination and a structured questionnaire to record the conditions of supporting soft tissues, prosthesis acceptance and technical characteristics, mastication, esthetics, comfort, hygiene, and need for professional intervention. Data were analyzed by descriptive statistics and Spearman correlation. Results: More than 50% of patients classified their RPDs as excellent regarding retention, mastication, esthetics, comfort, and hygiene. In the professional evaluation, retention and stability were considered excellent in more than 66% of cases, and hygiene of teeth and prostheses was considered good in 52% and 46%, respectively. The metallic framework and acrylic base were considered adapted in 92% of cases. Prosthesis acceptance was associated with retention, mastication, esthetics, hygiene, and comfort evaluated by the patient, and with retention, stability, and condition of the framework evaluated by the clinician. Retention and mastication/comfort evaluated by the patient had moderate positive correlation with retention and stability measured by the clinician. There was no association of hygiene evaluation by the patient and by the clinician. Conclusions: After five years, the oral rehabilitation with RPDs was satisfactory for most cases. There was correspondence between retention/retention and mastication-comfort/stability variables evaluated by the patient and by the clinician. Oral and prosthesis hygiene were not related.

Maximum occlusal force and medial mandibular flexure in relation to vertical facial pattern: a cross-sectional study.

BackgroundVertical facial pattern may be related to the direction of pull of the masticatory muscles, yet its effect on occlusal force and elastic deformation of the mandible still is unclear. This study tested whether the variation in vertical facial pattern is related to the variation in maximum occlusal force (MOF) and medial mandibular flexure (MMF) in 51 fully-dentate adults.MethodsData from cephalometric analysis according to the method of Ricketts were used to divide the subjects into three groups: Dolichofacial (n = 6), Mesofacial (n = 10) and Brachyfacial (n = 35). Bilateral MOF was measured using a cross-arch force transducer placed in the first molar region. For MMF, impressions of the mandibular occlusal surface were made in rest (R) and in maximum opening (O) positions. The impressions were scanned, and reference points were selected on the occlusal surface of the contralateral first molars. MMF was calculated by subtracting the intermolar distance in O from the intermolar distance in R. Data were analysed by ANCOVA (fixed factors: facial pattern, sex; covariate: body mass index (BMI); alpha = 0.05).ResultsNo significant difference of MOF or MMF was found among the three facial patterns (P = 0.62 and P = 0.72, respectively). BMI was not a significant covariate for MOF or MMF (P > 0.05). Sex was a significant factor only for MOF (P = 0.007); males had higher MOF values than females.ConclusionThese results suggest that MOF and MMF did not vary as a function of vertical facial pattern in this Brazilian sample.

Length of the drilling holes of zygomatic implants inserted with the standard technique or a revised method: a comparative study in dry skulls.

AIM This study aimed to evaluate the length of the holes drilled for the placement of zygomatic implants using two surgical techniques: the original Brånemark and the Exteriorized (extrasinus) protocols. The most frequent implant length used and position where the implants emerged in the zygomatic bone were recorded. MATERIALS AND METHODS Both surgical techniques for inserting zygomatic implants were performed on the right and left sides of 18 dry adult skulls. The depth of the drilling holes in the zygomatic bone for placement of zygomatic implants and the corresponding implant length were measured. The position where the implant emerged was recorded using a standardized division of the zygomatic bone surface into 13 sections (Fig. 3). RESULTS The Exteriorized technique showed significantly longer drilling holes for zygomatic implants than the Brånemark technique (P<0.001). For both techniques, the most commonly used implant lengths were 30 and 35 mm, and the most frequent position where the implants emerged were sections 9 and 12. CONCLUSIONS The results suggest that the Exteriorized technique increases the length of the drilling holes in the zygomatic bone, which may provide higher initial mechanical stability for zygomatic implants than the original Brånemark technique.

Effect of the number of abutments on biomechanics of Branemark prosthesis with straight and tilted distal implants

Objective This study aimed to evaluate the bending moments, and compressive and tensile forces in implant-supported prostheses with three, four or five abutments. Material and Methods Ten Pd-Ag frameworks were tested over two master models with: 1) parallel vertical implants, and 2) tilted distal implants. Strain gauges were fixed on the abutments of each master model to measure the deformation when a static load of 50 N was applied on the cantilever (15 mm). The deformation values were measured when the metallic frameworks were tested over three, four or five abutments, and transformed into force and bending moment values. Data were analyzed by ANOVA and Tukey’s test for multiple comparisons at 5% level of significance. Results Abutment #1 (adjacent to the cantilever) had the highest values of force and sagittal bending moment for all tests with three, four or five abutments. Independently from the number of abutments, axial force in abutment #1 was higher in the vertical model than in the tilted model. Total moment was higher with three abutments than with four or five abutments. Independently from the inclination of implants, the mean force with four or five abutments was lower than that with three abutments. Conclusion The results suggest that in the set-ups with four or five abutments tilted distal implants reduced axial force and did not increase bending moments.

Cell Culture–Based Tissue Engineering as an Alternative to Bone Grafts in Implant Dentistry: A Literature Review

Several biomaterials and techniques for bone grafting have been described in the literature for atresic bone tissue replacement caused by edentulism, surgical resectioning, and traumas. A new technique involves tissue engineering, a promising option to replace bone tissue and solve problems associated with morbidity of autogenous grafting. This literature review aims to describe tissue-engineering techniques using ex vivo cell culture as an alternative to repair bone maxillary atresias and discuss the concepts and potentials of bone regeneration through cell culture techniques as an option for restorative maxillofacial surgery.

Surface changes in denture soft liners with and without sealer coating following abrasion with mechanical brushing.

AIM To evaluate the surface alterations of soft liners with or without sealer coating following abrasion with mechanical brushing. METHODS Thirty specimens were made of a methacrylate- (Coe-Soft) and a siloxane-based material (Ufi-Gel SC), and 15 received two coatings of surface sealer. The specimens were submitted to a mechanical brushing-dentifrice assay under 200g of force at 250 cycles/min. Mechanical brushing was simulated for a period of 1 (1250 cycles) and 6 months (5000 cycles). Surface roughness (Ra parameter) was measured, and scanning electron microscopy (SEM) images were obtained. Ra data were analysed by anova for repeated measures and Bonferronis test (alpha=0.05). RESULTS Ra increased from baseline to 6 months regardless of sealer coating. At baseline, only Coe-Soft without sealer had a higher Ra than the other groups. After 1 month, the Ra of Coe-Soft with sealer was three-fold higher than the Ra at baseline; the other groups showed no significant increase of Ra. SEM images showed degradation of the soft liners over time, except for the Ufi-Gel SC with sealer, which displayed minimum alteration of surface texture. CONCLUSION Sealer coating reduced the surface degradation of the tested soft liners, but the protective effect was more pronounced for the siloxane-based material.

Surface changes in denture soft liners with and without sealer coating after mechanical brushing abrasion

AIM To evaluate the surface alterations of soft liners with or without sealer coating following abrasion with mechanical brushing. METHODS Thirty specimens were made of a methacrylate- (Coe-Soft) and a siloxane-based material (Ufi-Gel SC), and 15 received two coatings of surface sealer. The specimens were submitted to a mechanical brushing-dentifrice assay under 200g of force at 250 cycles/min. Mechanical brushing was simulated for a period of 1 (1250 cycles) and 6 months (5000 cycles). Surface roughness (Ra parameter) was measured, and scanning electron microscopy (SEM) images were obtained. Ra data were analysed by anova for repeated measures and Bonferronis test (alpha=0.05). RESULTS Ra increased from baseline to 6 months regardless of sealer coating. At baseline, only Coe-Soft without sealer had a higher Ra than the other groups. After 1 month, the Ra of Coe-Soft with sealer was three-fold higher than the Ra at baseline; the other groups showed no significant increase of Ra. SEM images showed degradation of the soft liners over time, except for the Ufi-Gel SC with sealer, which displayed minimum alteration of surface texture. CONCLUSION Sealer coating reduced the surface degradation of the tested soft liners, but the protective effect was more pronounced for the siloxane-based material.