Antimicrobial effect of silver nanoparticles on polypropylene and acrylic resin denture bases.

Background: The investigation of the antimicrobial action of Ag solutions in different surfaces has been performed, however, there is little data on the direct addition of those particles to the polypropylene denture base. The aim of this study was to evaluate the antimicrobial effect of silver nanoparticles in Candida albicans and Streptococcus mutans colonization in acrylic resin and polypropylene denture bases. Material and Methods: Twenty test bodies (10×13×3 mm) were fabricated with (heat-polymerized) poly methyl methacrylate acrylic resin (group 1), (heat-polymerized) poly methyl methacrylate acrylic resin with silver nanoparticles (group 2), polypropylene (group 3) and polypropylene with silver nanoparticles (group 4). Candida albicans and Streptococcus mutans colonization were performed. A colony count was performed in Colony Forming Unit (CFU/ml) and registered to calculate the arithmetical mean of the duplicate values of each sample. Data was analyzed by Lilliefors test and since samples did not present a normal distribution, Kruskal-Wallis for variance analysis with the value of significance set at p<0.05. Results: For Candida albicans colonies, when comparing nano-Ag in polypropylene, there were statistical difference between groups 3 and 4. For the same type of growth in heat-polymerized PMMA resin with and without nano-Ag, no statistical differences were found. The presence of nanoparticles did not affect Streptococcus mutans growth in the heat-polymerized PMMA resin. Value differences of S. mutans were not significant for comparisons between groups 1-2 and 3-4. Conclusions: Silver nanoparticles presented antifungal activity against C. albicans in polypropylene surfaces, but not in the heat-polymerized PMMA resin. Silver nanoparticles did not present antibacterial activity against S. mutans in any of the analyzed surfaces. Key words:Removable Partial Denture, Candida, Streptococcus mutans.

The influence of the retention feature in artificial teeth on its attachment to the thermoplastic resin denture base / Influência da forma de retenção em dentes artificiais de resina acrílica na fixação na base de prótese termoplástica

Objective: Teeth play a crucial role in masticatory efficiency and esthetic harmony making rehabilitation of partially edentulous patients a challenge because of the limitations of conventional removable partial dentures. As a therapeutic alternative, thermoplastic polymers are used in current dental practice either for practical processing purposes or aesthetics. However, it is recognized that the bond between acrylic resin artificial teeth and thermoplastic polymers has no chemical interaction, and depends on retentive features added to the teeth. This study analyzed the efficacy of two retentive forms of features through compressive strength test and as a secondary outcome, fracture and displacement resistance test. Material and Methods: Three groups of samples each with 14 sets of acrylic teeth were compared when two retentive features, single hole and groove retention, and a control group with teeth without any specific form. The experimental unit consisted of six maxillary anterior teeth, positioned in a linear pattern into a polypropylene block, where each tooth was submitted to a static load until its removal, on a universal testing machine. Results: Those specimens with a groove retention presented larger resistance to displacement when compared to the other groups (p <0.05). This was emphasized by the fracture of the tooth tested, with part of the cervical portion remaining embed in the base, and not its displacement as with (or without) the retentive feature. Conclusion: In this study, the type of retention influenced significantly to a better retention considering teeth and thermoplastic polymer base. The data in this study indicates that a groove placed on the artificial tooth offers significantly better retention efficacy to the point where the displacement was only possible after its fracture (AU)

Objetivo: Os dentes são um fator essencial na eficiência mastigatória. A harmonia estética e a reabilitação dos indivíduos parcialmente dentados tornam-se um desafio, frente às limitações das próteses parciais removíveis convencionais. Como uma alternativa terapêutica, os polímeros termoplásticos são utilizados na odontologia contemporânea, tanto para o seu processamento prático como seu apelo estético. Entretanto, pouco se sabe a respeito da união entre a resina acrílica de dentes artificiais e resinas termoplásticas, assim como a influência dos mecanismos de retenção, uma vez que não há interação química entre eles. O objetivo deste estudo foi analisar duas formas de retenção de dentes de resina acrílica a bases de prótese de material termoplástico, por força compressiva e como desfecho secundário, teste de resistência a fratura e deslocamento dos dentes artificiais. Material e Métodos: O presente estudo analisou dois tipos diferentes de retenções: uma cavidade com único ponto e uma canaleta de mesial a distal; e como grupo controle, dentes colocados sem qualquer recurso específico. A unidade experimental consistiu de seis dentes superiores anteriores, posicionados em linha em um bloco de polipropileno. Em cada dente artificial foi aplicada força até a sua remoção, em uma máquina universal de ensaios. Resultados: Os resultados mostraram que a retenção com canaleta apresentou maior força de deslocamento, quando comparado com os outros grupos (p <0,05). Tal fato foi evidenciado pelo teste de fratura e deslocamento, no qual parte da porção cervical do dente artificial permaneceu unida à base, não ocorrendo o deslocamento com (ou sem) a retenção. Conclusão: Neste estudo, o tipo de retenção influenciou de forma significante a retenção de dentes artificiais de resina acrílica a bases de prótese termoplásticas. Os dados deste estudo indicam que a confecção da retenção em canaleta nos dentes artificiais oferece significante aumento na eficiência da retenção, ao ponto em que o deslocamento do dente ocorreu somente após sua fratura (AU).

Assessment of different types of intra oral scanners and 3D printers on the accuracy of printed models: An in vitro study.

BACKGROUND: 3D printing technology is a reality in Dentistry and presents several ways to obtain a printed model. The aim of this study was to verify the influence of different types of intraoral scanners and 3D printers on the accuracy of printed models in comparison to plaster models obtained from conventional impressions. MATERIAL AND METHODS: A dental study model was used as the reference model and was molded with polyvinyl siloxane to produce the plaster models. It was also scanned with two types of intraoral scanners and the digital files were printed by two types of 3D printers. The plaster and printed models formed five groups (n=50), which were analyzed using linear measurements at six dimension sites. In order to test the equivalence in the precision of the measurements made in the reference model and in the different models of the experimental groups, the Schuirmann Two-One Sided t-test was applied. The trueness of the measurements of the experimental models was tested in comparison to those of the reference model by applying tests for paired data. In all statistical tests, the significance level of 5% (α = 0.05) was adopted. RESULTS: In relation to precision, all five groups presented similar and acceptable results. The trueness analysis indicated that both the printed and the plaster models had average measurements that were different from the reference model. CONCLUSIONS: It was concluded that the accuracy of printed and plaster models was impaired due to the trueness of the models. The type of printer influenced the accuracy of the printed models, while the type of scanner did not. The standardization of the method of obtaining printed models must be carried out in order to provide the production of quality models. However, there will be differences between the technologies. Key words:Dental models, three-dimensional printing, dimensional accuracy.

Sobrevida e perda marginal óssea de implantes de diâmetro estreito de liga titânio-zircônia e titânio puro / Survival rate of titanium-zirconium narrow diameter dental implants and commercially pure titanium narrow diameter dental implants

Apesar da existência de diversos estudos que validem o uso de implantes de diâmetro estreito, a maioria é baseada em ligas de titânio puro. Há pouca evidência clínica em relação ao sucesso do implantes de diâmetro estreito de titânio-zircônia (TiZr NDIs), no que diz respeito à taxa de sobrevida (SR) e perda óssea marginal (MLB). O objetivo desta revisão sistemática foi analisar sistematicamente SR, assim como MBL de TiZr NDIs quando comparados a implantes de diâmetro estreito de titânio comercialmente puro (cpTi NDIs). A busca foi conduzida nas bases Medline/Pubmed, Cochrane, Scopus e Embase (do ano 2000 a novembro de 2016). Foram incluídos estudos clínicos do tipo coorte e randomizados. Dos 3453 artigos inicialmente identificados, foram incluídos seis estudos clínicos. Não houve diferença estatisticamente significante em taxa de sobrevida quando comparados os grupos TiZr NDIs e cpTi NDIs, em um ano de acompanhamento (p=0,5), além disso, também não houve diferença na comparação entre região de implantação (anterior ou posterior) no grupo TiZr NDIs. Não houve diferença entre os grupos anterior e posterior em relação à taxa de sobrevida em um ano: -0,01 (95% CI, -0,05 a 0,03) e perda óssea marginal: -0,01 mm (95% CI: -0,14 a 0,12). Pode-se concluir que TiZr NDIs apresentam taxas de sucesso e reabsorção óssea peri-implantar similares às de cpTi NDis.

Survival rate of titanium-zirconium narrow diameter dental implants versus commercially pure titanium narrow diameter dental implants: A systematic review.

BACKGROUND: Despite the existence of several studies validating the use of narrow diameter implants, most of them are based on pure Ti alloys. There is few clinical evidence of the success of TiZr narrow diameter implants (TiZr NDIs) regarding survival rate (SR) and marginal bone loss (MLB). PURPOSE: The aim of this review was to systematically assess SR, as well as MBL of TiZr NDIs compared to commercially pure titanium narrow diameter implants (cpTi NDIs). MATERIAL AND METHODS: The search was conducted in Medline/PubMed, Cochrane, Scopus, and Embase databases (year 2000 to November 2016). Cohort studies and randomized trials were included. RESULTS: Six clinical studies from the 3453 articles initially identified met the inclusion criteria. There were no statistically significant differences in SR when TiZr NDIs and cpTi NDIs were compared in the 1-year follow up (P = .5), or when comparing TiZr NDIs placed in posterior and anterior regions. There was no difference between groups regarding 1-year SR: -0.01 (95% CI, -0.05-0.03) and MLB: -0.01 mm (95% CI: -0.14-0.12). CONCLUSION: It can be concluded that TiZr NDIs present similar success rates and peri-implant bone resorption to cpTi NDIs.

A 5-week Non-Surgical Approach towards Denture Induced Hyperplasia.

BACKGROUND: Despite the standard approach towards denture-induced hyperplasia being surgery, as elderly population increases the systemic problems are carried along. Thus, surgery might be risky for patients with medical conditions. OBJECTIVE: In this report, a patient with severe inflammatory papillary hyperplasia, medical problems and dental fear was treated with a 5-week nonsurgical protocol. METHOD: Once in a week, the upper denture was relined with a zinc enolic paste, for four weeks. In the fifth week, the denture was relined with fast set polymethyl methacrylate resin instead of zinc enolic paste so that the material would last longer than only a week until the new pair of dentures was manufactured. RESULTS AND CONCLUSION: The generated pressure combined with antioxidant and anti-inflammatory properties of the paste led to the elimination of the inflammatory papillary hyperplasia completely, satisfying the patient and allowing the manufacturing of a new set of complete dentures.

In Vivo Comparison of the Masticatory Efficiency of Artificial Teeth with Two Different Cusp Heights in Complete Dentures: A Preliminary Study.

PURPOSE: The goal of complete denture rehabilitation is to restore facial esthetics and masticatory function to edentulous patients. Several types of artificial teeth with different occlusal anatomy are available. Theoretically, teeth with a higher cusp height provide improved masticatory efficiency. The aim of this study was to compare the masticatory efficiency of complete denture wearers using artificial teeth with two cusp heights. MATERIALS AND METHODS: Sixteen complete denture wearers were given complete dentures with Heraeus Premium teeth. Fifteen days after denture installation, a first masticatory efficiency test was performed with Optocal. A new pair of complete dentures with Dentsply Biotone teeth was then given to each participant to replace the first set. This second set was fabricated by duplicating the same models used to fabricate the first set of dentures. Fifteen days after installation of the dentures with Biotone teeth, a second masticatory efficiency test was performed with Optocal. On both tests, the comminuted material was treated and sieved through a stack of sieves under vibration. The content of each sieve was weighed, and the obtained data were tabulated. Statistical analysis was performed using the Kolmogorov-Smirnov and Wilcoxon tests. RESULTS: Mean and standard deviation of participants' masticatory efficiency, as measured by X50 particle size (mm), were 8.39 and 5.59 for dentures with Premium teeth, and 8.56 and 5.84 for dentures with Biotone teeth. CONCLUSION: According to the results, there were no differences (p < 0.05) in the masticatory efficiency of the complete denture sets using teeth with the two cusp heights.

Different Occlusal Schemes in a Persistent Protruding Complete Denture Wearer.

Different types of artificial teeth and occlusal designs can be used in complete dentures. Bilateral balanced occlusion, lingualized occlusion, canine guidance, and monoplane are the main occlusal designs; however there is no agreement on which tooth arrangement is ideal for achieving success in complete dentures. This report presents an alternative for persistent involuntary protruding complete denture wearers through the use of artificial teeth with higher cusps. Due to an old and worn pair of complete dentures, the patient had the habit of protruding. New dentures were made with Biotone artificial teeth and in the trial session, the patient would still protrude. A new set was made with Premium artificial teeth, which present higher cusps. With these dentures, the involuntary protrusion did not occur. From the delivery to the follow-up sessions, the patient stopped protruding.

Eficiência mastigatória de indivíduos portadores de prótese total com arco dental reduzido / Masticatory efficiency of complete denture wearers with reduced dental arch

Um dos obstáculos na confecção das próteses totais é a diminuição de espaço intermaxilar para a montagem dos dentes artificiais posteriores, particularmente dos segundos molares, que influencia o tempo dispendido pelo profissional, pois gera a necessidade de desgaste da base de prova e muitas vezes do próprio dente. Na tentativa de contornar esse obstáculo, em alguns casos, tem-se suprimido a montagem dos segundos molares, uma vez que a ausência destes elementos não influencia a estética, fonética e conforto. Não há relatos na literatura que abordam este assunto, apesar de existirem estudos com arco encurtados e de performance mastigatória de próteses. O objetivo deste estudo foi comparar a eficiência mastigatória de pacientes portadores de próteses totais maxilomandibulares com arco reduzido (sem os segundos molares superiores e inferiores) e com o arco completo. Vinte indivíduos usuários de próteses totais maxilomandibulares, divididos em dois grupos aleatoriamente, receberam aparelhos protéticos novos. O grupo 1 recebeu as próteses sem os segundos molares e o grupo 2, com segundo molares. Após as consultas de controle, foi realizado o primeiro teste de eficiência mastigatória com Optocal. Quinze dias após o primeiro teste de performance mastigatória, foi realizado um novo teste, neste momento foram posicionados os segundos molares no grupo 1 e removidos no grupo 2. O material cominuído foi tratado e peneirado em uma pilha de peneiras sob vibração

A média e desvio padrão da eficiência mastigatória dos sujeitos no teste com todos os dentes posicionados foi de 4 e 0,68, respectivamente. Enquanto que, no teste sem os segundos molares foi de 4,22 e 0,92, respectivamente. Em relação ao momento da remoção dos segundos molares, a média do grupo 1 foi de 4,22 e desvio padrão de 0,63 e, do grupo 2 foi de 3,78 e 0,72, respectivamente. De acordo com a análise estatística realizada (p<0,05) não houve diferença na eficiência mastigatória em próteses totais maxilo-mandibulares com arco dental terminando em primeiro ou segundo molares. Portanto, a montagem de dentes até primeiros molares pode ser executada quando necessário, sem que haja comprometimento da eficiência mastigatória

One obstacle when placing posterior artificial teeth during the manufacturing of complete dentures is the reduction of spatial relationship of the maxillae to the mandible. It affects the work time of the technician, once it requires abrasion of the denture base and the artificial tooth itself. Occasionally, the placement of the second molars is suppressed, for it does not affect aesthetics, phonetics and comfort. There are no reports in literature on this subject; despite studies involving shortened dental arches and dentures masticatory performance. The aim of this study was to compare masticatory efficiency of maxillomandibular complete denture wearers with reduced dental arch (without superior and inferior second molars) and complete dental arch. Twenty subjects were divided in two groups randomly and received new dentures. Group 1 was given complete dentures without second molars and group 2 was given dentures with second molars. After post-insertion consults, the first masticatory efficiency test was taken with Optocal. Fifteen days after the first test, a new one was taken, in which second molars were positioned in group 1 and removed from group 2. Comminuted material was treated and sieved on a stack of sieves under vibration. Mean and standard deviation of subjects masticatory efficiency with complete dental arch was 4 and 0.68, respectively. While on the tests without second molars, mean and standard deviation were 4.22 and 0.92, respectively. Analyzing the moment of removal of second molars from the dental arch, mean of group 1 was 4.22 and standard deviation 0,63 and, group 2 3.78 and 0.72, respectively. According to the statistical analysis applied to this study (p<0,05), there were no differences on masticatory efficiency in complete dentures with or without second molars. Therefore, placing artificial teeth until first molars can be done when needed, without compromising masticatory efficiency

Avaliação da influência do ácido acético na eficiência da higienização de próteses totais / Evaluation of acetic acid influence in complete dentures hygiene effectiveness

Introdução: A manutenção da higiene das próteses é de grande importância para a saúde de seus usuários.O objetivo deste trabalho é avaliar a influência do ácido acético na eficiência da higienização de prótesestotais. Métodos: Para o estudo caso-controle, vinte e seis usuários de próteses totais foram selecionados emcasas de repouso em São Paulo. Os grupos receberam instruções sobre higiene das próteses totais, sendo ogrupo-controle instruído a deixá-las imersas em água durante a noite e o caso instruído a deixá-las imersasem vinagre pelo mesmo período. Nenhum paciente foi informado sobre o tipo de líquido utilizado. Resultadose Conclusão: Como resultado, obteve-se uma redução de placa no grupo estudado de 49% enquantono grupo-controle houve um aumento de 4%. Assim, é possível afirmar a eficácia do ácido acético na melhorada higienização de próteses totais

Introduction: The maintenance of complete denture is important for the patient?s health. The aim of thisstudy is to evaluate the influence of the acetic acid in complete dentures hygiene effectiveness. Methods:Twenty six wearers of complete dentures were selected in households in São Paulo City. Instructions weregiven on hygiene and they were instructed to keep their dentures in a certain liquid. Results and Conclusion:It was found a plaque reduction of 49% in the acetic acid group and an increase of 4% in the controlgroup. Thus, it was possible to affirm the efficiency of the acetic acid in the improvement of the completedentures? hygiene