Flexural strength of acrylic resin repairs processed by different methods: water bath, microwave energy and chemical polymerization

Denture fractures are common in daily practice, causing inconvenience to the patient and to the dentists. Denture repairs should have adequate strength, dimensional stability and color match, and should be easily and quickly performed as well as relatively inexpensive. OBJECTIVE: The aim of this study was to evaluate the flexural strength of acrylic resin repairs processed by different methods: warm water-bath, microwave energy, and chemical polymerization. MATERIAL AND METHODS: Sixty rectangular specimens (31x10x2.5 mm) were made with warm water-bath acrylic resin (Lucitone 550) and grouped (15 specimens per group) according to the resin type used to make repair procedure: 1) specimens of warm water-bath resin (Lucitone 550) without repair (control group); 2) specimens of warm water-bath resin repaired with warm water-bath; 3) specimens of warm water-bath resin repaired with microwave resin (Acron MC); 4) specimens of warm water-bath resin repaired with autopolymerized acrylic resin (Simplex). Flexural strength was measured with the three-point bending in a universal testing machine (MTS 810 Material Test System) with load cell of 100 kgf under constant speed of 5 mm/min. Data were analyzed statistically by Kruskal-Wallis test (

One-year prospective clinical study comparing patient satisfaction and masticatory performance of mandibular overdentures supported by one versus two implants

There is a lack of clinical evidence on mandibular overdentures (MOD) supported by a single implant. Objective: To compare patient satisfaction and masticatory performance in MOD supported by one versus two implants in a two-group parallel randomized clinical trial. Material and Methods:Twenty-one patients wearing new maxillary and mandibular complete dentures (CDs) were randomly divided to receive one (GI, n = 11) or two (GII, n = 10) implants in the mandibular arch. Four months after implant placement, o-ring abutments were installed in the implants, and matrix attachments were placed in the lower complete dentures. Patient satisfaction with their dentures and masticatory performance were compared at baseline, 3, 6, and 12 months after the procedure. Data on patient satisfaction were analyzed using the Friedman test and the Mann-Whitney U test. Data on masticatory performance were analyzed using one-way repeated measures analysis of variance (ANOVA) and Student's t test (α=0.05). Results: Both groups exhibited a significant increase in overall patient satisfaction in all periods evaluated (p<0.05), except for GI after 12 months, which had values similar to baseline (p=0.74). Satisfaction levels of GI and GII were similar at baseline, 3 and 6 months, but GII showed higher satisfaction levels (p=0.01) than GI at 12 months. GI and GII exhibited a significant increase (p<0.05) in masticatory performance for all periods relative to baseline. However, GII had higher masticatory performance with dentures than GI, regardless of the period (p<0.05). Conclusion: MOD supported by two implants demonstrated better patient satisfaction in the follow-up at 12 months and better masticatory performance than MOD supported by one implant. &nbsp

Influencia das resinas acrilicas, tecnicas de polimerização e do periodo de armazenamento em agua na movimentação total superior

Orientadores: Saide Sarkis Dominitti, Simonides ConsaniTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Odontologia de PiracicabaResumo: O objetivo deste estudo foi analisar a intluência do período de armazenagem e das técnicas de polimerização, em três marcas comerciais de resinas acrílicas, na movimentação dental de prótese total superior. As resinas acrílicas utilizadas foram LUCITONE 550 (polimerizada em banho de água a 740C por 9 horas e em microondas a 500 W por 3 minutos), QC20 (ciclo em água fervente por 20 minutos) e ACRON-MC (ciclo em microondas 500W por 3 minutos). As distâncias dentais foram mensuradas após o enceramento da prótese (To), inclusão (TI), polimerização e demutlagem (Tz) e nos períodos de 3 (T3), 7 (T4) e 30 dias (Ts) de armazenagem em água a 37°C. Os resultados obtidos foram submetidos ao teste de T~ey (p :::; 0,05) e permitindo concluir que: (1) A resina ACRONMC apresentou os maiores deslocamentos dentais~ (2) No período T3 (3 dias de armazenagem) ocorreram os maiores índices de deslocamentos dentais~ (3) Os períodos de armazenagem em água não compensaram totalmente as distorções~ e, (4) As distâncias entre pré-molares e molares mensuradas no plano horizontal nas direções látero-Iateral e ânteroposterior apresentaram contração e expansão respectivamenteAbstract: The objective of this study was to analyze the teeth movement during different cure techniques of three commercial acrylic resins and afier periods of water storage in upper complete dentures. The acrylic resins used and the cure techniques proposed were : LUCITONE 550 (cured in water 9 Hs at 74° C and energy microwave 550 W at 3 min.), QC-20 (cured in boiled water 20 min.) and ACRON-MC (cured in energy microwave 550 W at 3 min.). The teeth distances, measured in the frontal and sagital planes by linear microscopy, were taken afier denture wax (To), denture inc1usion(T 1), cureq and demuflask (T2) and in the periods of 3(T3), 7- (T4) and 30-day (Ts) water storage. The results were analysed for Tukey's test (p ~ 0,05) and permited to conc1ued that: (1) ACRON-M..Ç resin presented_the highes~h movement in all perioqs: (2) the 3-d.ro: water storage ITJJ showed--1he highest movement scores: (3) the water storage did not fully compensate the cur~ distortions in upper complete illnture anq (4) cont;rngion anq expansion occurreq among ~ ' measured frontal/sagital planes. respectivelyDoutoradoProtese DentalDoutor em Clínica Odontológic

Influencia da forma do palato e da sorção de agua na adaptação de proteses totais

Orientador: Saide Sarckis DomittiDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Odontologia de PiracicabaResumo: Neste trabalho foram analisadas as influências das fonnas geométricas dos palatos (triangular, oval e plano) e os tempos de armazenagem em água a 37:1:2 °c (24 horas, 15 e 30 dias) na adaptação das bases de próteses totais superiores confeccionadas com resina acrílica polimerizada termicamente. A metodologia consistiu na confecção de próteses totais superiores à partir de modelos mestres de gesso, devidamente duplicados em moldeiras individuais com silicona por adição e gesso pedra tipo IV. Após enceramento, inclusão, polimerização e demuflagem, as peças protéticas foram armazenadas em água nos períodos previamente determinados. Posterionnente, com auxílio de um aparelho específico adaptado à mna mesa de fixação, foi possível controlar o assentamento final das próteses sobre os respectivos modelos mestres e sua fixação com adesivo instantâneo. Orientados por guias existentes na própria mesa de fixação, foram realizados cortes padronizados com serra manual, correspondentes as regiões do selado periférico posterior ("post -dam"), fossas centrais dos primeiros molares e regiões distais dos caninos. Os desajustes entre as bases de resina acrílica e os modelos mestres foram mensurados com um microscópio comparador linear. Os resultados indicaram que existe uma significância estatística ao nível de 5 % nas fonnas geométricas do palato tendo o palato plano apresentado os menores desajustes. O palato triangular demonstrou os maiores valores de desajuste entre a base de resina acrílica e o modelo de gesso. As localizações dos cortes também apresentaram valores significantes estatisticamente, sendo que o corte mais posterior (corte I) revelou os maiores desajustes, seguido pelos cortes li e IIl, respectivamente. Os períodos de armazenagem em água destilada a 37:t2 DC não demonstraram qualquer significância estatística entre os dados. Desta maneira, os resultados indicaram que a região do "post-dam" foi a mais desfavorável à adaptação em prótese total, tendo a forma geométrica triangular do palato contribuído para o aumento dos desajustes que poderão interferir na retenção e estabilidade de próteses totais superioresAbstract: The purpose of this study was to evaluate the influence of palate geometric shapes ( deep, intennediate and flat) and the period of storage in water at 3712 DC (24 hours, 15 and 30 days) related to the adaption of superior complete dentures bases of heat -cured acrylic resin. The superior complete dentures was confeccioned from master cast duplicated with individual trays using silicone and embebed with stone plaster. After waxed, cured and deflasked, the complete dentures were storaged in water in the previously determined periods. Afterly, with the aid of an especific instnnnent on fixation grip, it was possible to control the final adjustment of the dentures over the master cast and its fixation with instantanious adhesive. The cuts were made with manual saw in corresponding postpalatal region, central region of first molars and distal regions of canines. The disadjustment between acrylic resin base and cast stone was mesured with an linear microscope. The results showed an statistical significative difference when the most . posterior cut (cut l) was compared with the cuts H and lH. The greater disajustment was obtained in the cut l and the smallest one was observed in cut lH. The periods of storage in water at 37-:12 DC didn't show any statistic difference between the data. The results showed that the postpalatal region is the most adversely to the adaptation in total dentures, with the deep geometric shape increasing the disadjustments, being able to interfere in retention and stability of superior total denturesMestradoProteseMestre em Clínica Odontológic

The center of the incisive papilla for the selection of complete denture maxillary anterior teeth in 4 racial groups

Objectives: To evaluate the use of the center of the incisive papilla as a guide for the selection of the proper width of maxillary dentures in 4 racial groups. Method and Materials: One hundred sixty stone casts were obtained from impressions of the maxillary arch of white, black, mixed, and Asian subjects. The occlusal surfaces of the casts were photocopied and the images placed on a digitizer. The most anterior and posterior points of the papilla and cusp tips of the canines were digitized. Dentofacial Planner Plus software was used to calculate the distance from a line passing through the cusp tips of the canines to the center of the papilla, defined as the midpoint of the anterior and posterior points of the papilla. The selection error (in millimeters) due to the clinical application of the method of the incisive papilla was calculated and analyzed. Results: In all studied racial groups, there was no coincidence between the center of the incisive papilla and the canine line. The utilization of the center of the papilla would lead to the selection of wider artificial teeth. In 24.9% of the white, 19.3% of the mixed, 32.9% of the black, and 15.5% of the Asian populations, errors greater than 4 mm would be present with the utilization of the papilla. Conclusion: The method of the center of the incisive papilla is not accurate, but may aid in initial artificial teeth selection for the racial groups studied. (Quintessence Int 2008;39:841-845

Correlation between maxillary central incisor form and face form in 4 racial groups

Objectives: the purpose of this study was to evaluate the correlation between central incisor form and face form in 4 racial groups and to investigate if there was agreement among experts in categorizing the central incisor forms. Method and Materials: A total of 160 subjects (40 whites, 40 mulattos, 40 blacks, and 40 Asians) ranging from 18 to 33 years of age were selected. Digital photographic records were made, 1 full-face and 1 intraoral view of the maxillary right central incisor. The outline tracings of the tooth and face images were obtained using Adobe Photoshop 5.0 software. The outline tracings were printed in distinct transparencies, and 3 prosthodontists determined if there was correspondence between the tooth and the face forms by superimposition of the transparencies. If there was disagreement among the prosthodontists' evaluations, the prevalent decision was considered. The experts also classified the central incisor forms into square, ovoid, tapering, or combination at 2 different sessions. At the first session, no instructions were given. At the second session, the prosthodontists were instructed to follow Williams' method of classification. Results: A correspondence between tooth and face forms was found in 23.75% of all cases. Agreement on the tooth form classifications among the prosthodontists occurred in 30.62% of all cases at the first session and 24.37% at the second session. Conclusion: There is not a highly defined correlation between central incisor form and face form in any racial group studied. In addition, the experts were not in fair agreement in categorizing tooth forms