Comparison of accuracy between compression- and injection-molded complete dentures

Statement of problem. A clinically significant incisal pin opening may occur after processing complete dentures if a compression molding technique is used. To recover the proper vertical dimension of occlusion, a time-consuming occlusal adjustment is necessary that often destroys the anatomy of the artificial teeth. A new injection molding process claims to produce dentures that require few, if any, occlusal adjustments in the laboratory after processing.Purpose. This laboratory study compared incisal pin opening, dimensional accuracy, and laboratory working time for dentures fabricated by this new injection system with dentures constructed by the conventional compression molding technique.Material and methods. Two groups of 6 maxillary and 6 mandibular dentures were evaluated as follows: group 1 (control), Lucitone 199, compression molded with a long cure cycle; and group 2, Lucitone 199, injection molded with a long cure. Incisal pin opening was measured with a micrometer immediately after deflasking. A computerized coordinate measuring machine was used to measure dimensional accuracy of 3-dimensional variations in selected positions of artificial teeth in 4 stages of denture fabrication. Analysis of variance (ANOVA) and t tests were performed to compare the groups.Results. A significant difference was found in pin opening between groups (t test). Horizontal dimensional changes evaluated with repeated measures ANOVA revealed no significant differences between groups. However, analysis of vertical dimensional changes disclosed significant differences between the groups. There was no appreciable difference in laboratory working time for flasking and molding denture bases between the injection and compression molding techniques when polymethyl methacrylate resin was used.Conclusion. The injection molding method produced a significantly smaller incisal pin opening over the standard compression molding technique. The injection molding technique, using polymethyl methacrylate, was a more accurate method for processing dentures. There were no appreciable differences in laboratory working time between the injection and compression molding techniques.

Vertical marginal discrepancy of ceramic copings with different ceramic materials finish lines and luting agents: An in vitro evaluation

Statement of problem. Prosthetic restorations that fit poorly may affect periodontal health and occlusion. Studies that have evaluated the accuracy of fit of ceramic restorations before and after cementation assessed primarily intracoronal restorations.Purpose. This in vitro study evaluated the effect of different finish lines, ceramic manufacturing techniques, and luting agents on the vertical discrepancy of ceramic copings.Material and methods. Two stainless steel molars were prepared for complete crowns with 2 different finish lines (heavy chamfer and rounded shoulder); each molar was duplicated to fabricate 90 copings. A total of 180 copings generated 18 groups (n=10 for each finish line-coping material-luting agent combination). Luting agents tested included zinc phosphate, resin-modified glass ionomer (Fuji Plus), and resin composite cements (Panavia F). A metal frame was developed on which to screw the stainless steel model and a ceramic coping; the distance (mum) between 2 predetermined points was measured before and after cementation by a profile projector under a torquing force. A 4-way ANOVA with repeated measurements was performed to assess the influence of each factor in the vertical marginal discrepancy: 3 between-coping factors (finish line-coping material-luting agent) and 1 within-coping factor (before and after cementation) (alpha=.05).Results. Procera copings presented the lowest mean values (P<.05) of vertical marginal discrepancy before and after cementation (25/44 mum) when compared to Empress 2 (68/110 mum) and InCeram Alumina copings (57/117 mum), regardless of any combinations among all finish lines and luting agents tested.Conclusion. Considering each factor separately, the ceramic manufacturing technique appeared to be the most important factor tested for the definitive vertical discrepancy of all-ceramic copings, with lower mean values for Procera copings.

Estimativas de parâmetros genéticos para características de crescimento e produtividade em vacas da raça Canchim, utilizando-se inferência bayesiana

The objective of this study was to estimate genetic parameters for body weights at weaning (PD), 12 months old (P12) and adult age (PAD), culling age (TPR, days in herd), number (ND10) and kilograms (QD10) of calves weaned up to ten years of age, total number (NDT) and total kilograms (QDT) of calves weaned during herd life, and kilograms of calves weaned per year in herd (QTPR) of Canchim (5/8 Charolais + 3/8 Zebu) females from one herd. Data consisted of 3,249, 3.111, 1,138, 1,340, 1,362, 1,362, 1,340, 1,340 and 1,340 records of PD, P12, PAD, TPR, ND10, QD10, NDT, QDT and QTPR. respectively. Variance and covariance components were estimated by bivariate analyses between PD, P12 and PAD and other production traits using Bayesian inference. The models included the additive direct, permanent environmental and residual random effects and the fixed effects year and month of birth or calving, calving age and age of the animal, depending on the trait. QD10, QDT and QTPR of each female were obtained by adjusting the weaning weights of calves for year and month of birth, sex and age of cow. Average of heritability estimates were 0.38 (PD), 0.40 (P12), 0.54 (PAD), 0.22 (TPR), 0.22 (ND10), 0.24 (QD10), 0.23 (NDT), 0.23 (QDT) and 0.32 (QTPR), indicating genetic variability to obtain response by selection. Genetic correlations between TPR (-0.02, 0.26 and -0.12), ND10 (0.04, 0.10 and -0.29), QD10 (0.37, 0.39 and -0.13), NDT (-0.03, 0.14 and -0.25), QDT (0.20, 0.33 and -0.16), QTPR (0.21, 0.28 and -0.19) and body weights (PD, P12 and PAD) suggest that selection of females based on weaning and 12-month body weights will not affect productivity. However, it may be decreased by increasing female adult body weight.

AORTIC BARORECEPTORS PLAY A PREDOMINANT ROLE IN THE REGULATION OF HINDLIMB VASCULAR-RESISTANCE IN RATS

In previous studies using bilateral carotid occlusion in conscious freely moving rats we suggested that aortic baroreceptors may play a more important role in the regulation of hindlimb than in renal and mesenteric vascular resistances. In the present study we performed electrical stimulation of the aortic baroreceptor nerve and analyzed the changes in mean arterial pressure and in hindlimb, renal, and mesenteric vascular resistances. All the experiments were performed under urethan anesthesia. Unilateral electrical stimulation (3 V, 2 ms, 50 Hz) of the aortic baroreceptor nerve produced a fall in arterial pressure (-27 +/- 3 mmHg) and an important reduction in hindlimb vascular resistance (-43 +/- 5%), with an increase in renal (+3 +/- 14%) and mesenteric (+48 +/- 12%) vascular resistances. Similar changes in arterial pressure as well as in the resistance of the three vascular beds studied were also observed during electrical stimulation of the aortic baroreceptor nerve in rats with bilateral carotid baroreceptor denervation or in rats treated with methylatropine. The data obtained with electrical stimulation indicated that aortic baroreceptors play a more important role in the regulation of blood flow in hindlimb than in renal and mesenteric vascular beds.

Effect of denture fabrication and wear on closest speaking space and interocclusal distance during deglutition

Statement of problem. The accuracy of assessing maxillomandibular relationships for trial bases and dentures using phonetic and swallowing methods has not been compared to that observed with definitive prostheses. Thus, there is no evidence to prove whether measurements obtained through such methods remain the same after adaptation to dentures.Purpose. This study investigated changes in the closest speaking space, interocclusal rest space, and interocclusal distance during deglutition in edentulous patients during and after complete denture treatment.Material and methods. Eighteen edentulous subjects participated in this study and measurements were performed after 7 Intervals of time: (1) with occlusion rims and record bases following creation of the maxillomandibular relationship record, (2) with trial dentures, (3) at Insertion of definitive complete dentures, (4) 1 week, (5) 2 weeks, (6) 1 month, and (7) 3 months after insertion. Recordings of interocclusal distances were made with a mandibular kinesiograph. Closest speaking space was measured during the pronunciation of the word 'seis'. The distance between postural rest position and centric occlusion, or interocclusal rest space, was measured using a kinesiograph. Interocclusal distance during deglutition was tested by recording the closest mandibular position recorded during swallowing of 20 mL of water. Data were analyzed using repeated-measure ANOVA, followed by the Student-Newman-Keuls test (alpha=.05).Results. A significant (P <.01)reduction in the mean closest speaking space was found when it was evaluated using occlusion rims and record bases (4.6 mm) compared with other stages (3.0 to 3.4 mm). No significant differences were found in mean interocclusal rest space and interocclusal distance during deglutition among the time periods evaluated.Conclusions. The presence of occlusion rims can influence mandibular position during pronunciation of the /s/ sound. The arrangement of artificial teeth changes the closest speaking space. However, rest position and deglutition were not affected, either during denture fabrication or short-term use.

Composite occlusal surfaces for acrylic resin denture teeth

Acrylic resin denture teeth often exhibit rapid occlusal wear, which may lead to a loss of chewing efficiency and a loss of vertical dimension of occlusion. The use of metal occlusal surfaces on the acrylic resin denture teeth will minimize occlusal wear. Several articles have described methods to construct metal occlusal surfaces; however, these methods are time-consuming, costly, and sometimes considered to be unesthetic. These methods also require that the patient be without the prosthesis for the time necessary to perform the laboratory procedures. This article presents a quick, simple, and relatively inexpensive procedure for construction of composite occlusal surfaces on complete and partial dentures.

The treatment of painful temporomandibular joint clicking with oral splints: A randomized clinical trial

Background. The authors compared the efficacy of bilateral balanced and canine guidance (occlusal) splints in the treatment of temporomandibular joint (TMJ) pain in subjects who experienced joint clicking with a nonoccluding splint in a double-blind, controlled randomized clinical trial.Methods. The authors randomly assigned 57 people with signs of disk displacement and TMJ pain into three groups according to the type of splint: bilateral balanced, canine guidance and nonoccluding. The authors followed the groups for six months using analysis of a visual analog scale (VAS), palpation of the TMJ and masticatory muscles, mandibular movements and joint sounds. They used repeated analysis of variance and a XI test to test the hypothesis.Results. The type of guidance used did not influence the pain reduction; yet both occlusal splints were superior to the nonoccluding splint, on the basis of the VAS. Despite similar outcomes in relation to opening, left; lateral and protrusive movements, TMJ and muscle pain on palpation, subjects who used the occlusal splints had improved clinical outcomes. The frequency of joint noises decreased over time, with no significant differences among groups. Subjects in the groups using the occlusal splints reported more comfort.Conclusion. The type of lateral guidance did not influence the subjects'; improvement: All of the subjects had a general improvement on the VAS, though subjects in the occlusal splint groups had better results that did subjects in the nonoccluding splint group.

Clinical evaluation of the association of noncarious cervical lesions, parafunctional habits, and TMD diagnosis

Objective: To verify a potential association between the presence of noncarious cervical lesions, parafunctional habits, and temporomandibular disorder (TMD) diagnosis. Method and Materials: Sample-size calculation provided a value of 130 participants with a confidence level of 95% and an error margin of 5%. A population of 132 volunteers (30 men: mean age, 23.7 +/- 3.05 years; 102 women: mean age, 24.9 +/- 5.86 years) underwent an oral examination and was interviewed by a trained dentist. The following parameters were registered: personal details, TMD diagnosis, parafunctional habits, and noncarious cervical lesion presence. The population was then divided into a noncarious cervical lesion group and a control group and subjected to the t test, chi-square test, Fisher exact test, and Spearman correlation (alpha = .05). Results: Noncarious cervical lesions were present in 39% of the population, with the largest concentrations found in the maxillary premolars (32%). The data showed a significant association between noncarious cervical lesion presence, tooth clenching (P = .03), and nail biting (P = .02), as well as a relation with TMD diagnosis (Fonseca Index [P = .01] and Research Diagnostic Criteria for TMD (RDC/TMD) [P = .004] ). In the noncarious cervical lesion group, direct rank correlation was found between maxillary premolars and clenching (P = .03), mandibular canines and nail biting (P = .05), and mandibular incisors and parafunctional habits without dental contacts (P = .02). Conclusion: Parafunctional habits and TMD presence should be taken into account in the diagnosis and treatment plan of noncarious cervical lesions.

Influência da oclusão bilateral das artérias carótidas comuns sobre a atividade vagal

The effects of carotid occlusion on parasympathetic activity were studied in anesthetized dogs submitted to beta adrenergic blockade. Modifications of the heart rate, before and after administration of atropine, were utilized for assessment of vagal changes. When vagal activity was intact there was elevation of the heart rate. After parasympathetic blockade carotid occlusion did not cause heart rate modifications. The data suggest that carotid occlusion produced vagal inhibition.

Alguns aspectos funcionais da articulação temporomandibular.

The authors emphasize the some functional characteristics of the Temporomandibular join, TMJ, and were made comparative study of the auscultatory and sphymografic techniques to TMJ examination. The findings shown that the auscultatory technique furnished important dates to preliminary diagnosis of the TMJ disfunction.

Determinação da relação central. Estudo sobre as posições laterais da mandíbula, em relação à linha mediana facial, em função de dois métodos para esta determinação.

The authors studied the lateral positional desviations of the mandible, in relation to the facial median line in 30 (thirty) full edentulous patients, with the purpose to verify the influence of the unstrained guided (chinpoint guidance) and deglutition methods for the determination of centric relation. According the results obtained they conclude that the unstrained guided method produced a mandibular lateral desviation with a mean value of the 0.752 mm and in the deglutition method the mean value observed was 1.109 mm. The statistical analysis of the results revealed for the unstrained guided method a proportion of the points to the right and left of the median line not statistically significant, while for the deglutition method the difference was statistically significant at a level of 5%.

A influência da perfusão cardíaca nas relações pressão/volume do ventrículo esquerdo.

PURPOSE--To analyze the influence of the myocardial engorgement due to coronary perfusion on the left ventricular diastolic pressure/volume (P/V) relations. METHODS--The study was undertaken in the isovolumic blood-perfused dog heart preparation (n = 7). The P/V relations were determined promoting ventricular volumes variations by steps of 2ml, in two conditions: during coronary perfusion pressure of 100mmHg and after occlusion of the perfusion line. RESULTS--It was verified that the P/V relations obtained without myocardial perfusion shifted to the down right in respect to the perfused heart. A exponential fitting of the P/V relations allows to conclude that there was no difference among the slopes of the curves obtained with and without perfusion. CONCLUSION--Our results indicated that coronary perfusion restrain the capacity of the left ventricle to receive blood, but there is no influence on the passive elastic stiffness of the chamber. This effect was taught to be consequence of the myocardial erectile property.

Force patterns of hypoxic myocardium applied to oxygenated muscle preparations: Comparison with effects of regional ischemia on the contraction of non-ischemic myocardium

Objective: To examine the basis for local wall motion abnormalities commonly seen in patients with ischemic heart disease, computer-controlled isolated muscle studies were carried out. Methods: Force patterns of physiologically sequenced contractions (PSCs) from rat left ventricular muscle preparations under well-oxygenated conditions and during periods of hypoxia and reoxygenation were recorded and stored in a computer. Force patterns of hypoxic-reoxygenating and oxygenated myocardium were applied to oxygenated and hypoxic-reoxygenating myocardium, respectively. Results: Observed patterns of shortening and lengthening closely resemble those obtained from ischemic and non-ischemic myocardial segments using ultrasonic crystals in intact dog hearts during coronary occlusion and reperfusion, and are similar to findings reported in angiographic studies of humans with coronary artery disease. Conclusion: The current study, demonstrating motions of oxygenated isolated muscle preparations which are similar to those in perfused segments of intact hearts with regional ischemia, supports the concept that the multiple motions of both ischemic and non-ischemic segments seen in regional myocardial disease can be explained by interactions of strongly and weakly contracting muscle during the physiologic cardiac cycle.

Effect of α-tocopherol, taurine and selenium on the attenuation of ischemia/reperfusion injury of splanchnic organs

Background: Splanchnic artery occlusion shock is caused by increased capillary permeability and cellular injury precipitated by oxygen derived free radicals following ischemia and reperfusion of splanchnic organs. The purpose of this study was to assess the role of several well-known oxygen- derived free radical scavengers in ameliorating or preventing this syndrome. Study design: Anesthetized rats were subjected to periods of occlusion of the visceral arteries and reperfusion. Tocopherol, taurine, selenium or a 'cocktail' of these three agents was injected subcutaneously for 4 consecutive days prior to operation. Mean arterial blood pressure was measured throughout the experimental period. Fluorometry and technetium-99m pyrophosphate counting of the visceral organs were performed as well as a histologic grading system for intestinal viability. Results: Final mean arterial blood pressure associated with the 'cocktail' and selenium groups was 79.1 ± 27.4 mmHg and 83.6 ± 17.8 mmHg, respectively. These values were significantly higher than the control group, 40.8 ± 11.4 mmHg (P < 0.05). Similar patterns of the benefit of selenium in contrast with the other groups were obtained with fluorescein perfusion, radioisotopic activity and histologic analysis. Conclusion: Pretreatment with selenium of splanchnic ischemia and reperfusion in the rat improves mean arterial blood pressure and microcirculatory visceral perfusion. Further analysis of the precise protective mechanism of selenium for reperfusion injury will enable visceral organs to withstand the consequences of increased capillary leakage and oxidant injury.

Efeito da seleção quanto ao peso corporal nas características reprodutivas em linhagens de frangos de corte

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)