Mechanical and technical risks in implant therapy

PURPOSE: To systematically appraise the impact of mechanical/technical risk factors on implant-supported reconstructions. MATERIAL AND METHODS: A MEDLINE (PubMed) database search from 1966 to April 2008 was conducted. The search strategy was a combination of MeSH terms and the key words: design, dental implant(s), risk, prosthodontics, fixed prosthodontics, fixed partial denture(s), fixed dental prosthesis (FDP), fixed reconstruction(s), oral rehabilitation, bridge(s), removable partial denture(s), overdenture(s). Randomized controlled trials, controlled trials, and prospective and retrospective cohort studies with a mean follow-up of at least 4 years were included. The material evaluated in each study had to include cases with/without exposure to the risk factor. RESULTS: From 3,568 articles, 111 were selected for full text analysis. Of the 111 articles, 33 were included for data extraction after grouping the outcomes into 10 risk factors: type of retentive elements supporting overdentures, presence of cantilever extension(s), cemented versus screw-retained FDPs, angled/angulated abutments, bruxism, crown/implant ratio, length of the suprastructure, prosthetic materials, number of implants supporting an FDP, and history of mechanical/technical complications. CONCLUSIONS: The absence of a metal framework in overdentures, the presence of cantilever extension(s) > 15 mm and of bruxism, the length of the reconstruction, and a history of repeated complications were associated with increased mechanical/technical complications. The type of retention, the presence of angled abutments, the crown-implant ratio, and the number of implants supporting an FDP were not associated with increased mechanical/technical complications. None of the mechanical/technical risk factors had an impact on implant survival and success rates.

Numerical investigation of the mechanical loading of supporting soft tissue for partial dentures

The aim of this research was to study the impact of loading on partial dentures within the supporting soft tissue with respect to different attachment techniques. A finite element model was developed to calculate the stress and strain distribution in this tissue. The model consisted of the left half of a mandible with three remaining teeth that had suffered an atrophy in the anterior region, and a partial denture over the toothless area that was connected at the left mandibular canine using an attachment system. Resulting stress/strain distributions are presented for different load cases using a commercially available prefabricated attachment system.

Curing lights for orthodontic bonding: a systematic review and meta-analysis

INTRODUCTION Light cure of resin-based adhesives is the mainstay of orthodontic bonding. In recent years, alternatives to conventional halogen lights offering reduced curing time and the potential for lower attachment failure rates have emerged. The relative merits of curing lights in current use, including halogen-based lamps, light-emitting diodes (LEDs), and plasma arc lights, have not been analyzed systematically. In this study, we reviewed randomized controlled trials and controlled clinical trials to assess the risks of attachment failure and bonding time in orthodontic patients in whom brackets were cured with halogen lights, LEDs, or plasma arc systems. METHODS Multiple electronic database searches were undertaken, including MEDLINE, EMBASE, and the Cochrane Oral Health Group's Trials Register, CENTRAL. Language restrictions were not applied. Unpublished literature was searched on ClinicalTrials.gov, the National Research Register, Pro-Quest Dissertation Abstracts, and Thesis database. Search terms included randomized controlled trial, controlled clinical trial, random allocation, double blind method, single blind method, orthodontics, LED, halogen, bond, and bracket. Authors of primary studies were contacted as required, and reference lists of the included studies were screened. RESULTS Randomized controlled trials and clinical controlled trials directly comparing conventional halogen lights, LEDs, or plasma arc systems involving patients with full arch, fixed, or bonded orthodontic appliances (not banded) with follow-up periods of a minimum of 6 months were included. Using predefined forms, 2 authors undertook independent extraction of articles; disagreements were resolved by discussion. The assessment of the risk of bias of the randomized controlled trials was based on the Cochrane Risk of Bias tool. Ten studies met the inclusion criteria; 2 were excluded because of high risk of bias. In the comparison of bond failure risk with halogen lights and plasma arc lights, 1851 brackets were included in both groups. Little statistical heterogeneity was observed in this analysis (I(2) = 4.8%; P = 0.379). There was no statistical difference in bond failure risk between the groups (OR, 0.92; 95% CI, 0.68-1.23; prediction intervals, 0.54, 1.56). Similarly, no statistical difference in bond failure risk was observed in the meta-analysis comparing halogen lights and LEDs (OR, 0.96; 95% CI, 0.64-1.44; prediction intervals, 0.07, 13.32). The pooled estimates from both comparisons were OR, 0.93; 95% CI, 0.74-1.17; and prediction intervals, 0.69, 1.17. CONCLUSIONS There is no evidence to support the use of 1 light cure type over another based on risk of attachment failure.

Impulsive Partial Hyperbolic Functional Differential Equations of Fractional Order with State-Dependent Delay

MSC 2010: 26A33, 34A37, 34K37, 34K40, 35R11

Preparos dentários de dentes pilares em prótese parcial removível

A perda de dentes além de afectar a mastigação e a estética, altera também o equilíbrio do sistema estomatognático, observando-se de imediato alterações na posição dos dentes adjacentes e dos dentes oponentes. Torna-se, portanto, imprescindível para a reposição da saúde oral do paciente a reabilitação com recurso a próteses fixas ou removíveis. No que diz respeito às próteses parciais removíveis (PPR´s) estas visam a substituição dos dentes perdidos, sendo facilmente removidas e inseridas pelo paciente, sem qualquer intervenção do médico dentista e, apoiam-se directamente na mucosa e nos dentes. Enquanto as PPR´s acrílicas são suportadas pela mucosa, mediante uma ampla área de contacto, as próteses esqueléticas são suportadas pelos dentes pilares através da colocação de retentores. No caso específico das PPR´s, é fundamental que o profissional de saúde tenha em consideração a importância do planeamento correcto e adequado da reabilitação oral. Para isso, pode e deve utilizar o paralelómetro, determinando assim correctamente a localização dos planos-guia, dos apoios e retentores necessários. Guiando-se por estes princípios fundamentais, qualquer reabilitação com recurso às PPR´s pode ser bem sucedida quer a nível estético quer a nível funcional.

Models for the estimation of life of stator insulation in large rotating machines

Epoxy resin bonded mica splitting is the insulation of choice for machine stators. However, this system is seen to be relatively weak under time varying mechanical stress, in particular the vibration causing delamination of mica and deboning of mica from the resin matrix. The situation is accentuated under the combined action of electrical, thermal and mechanical stress. Physical and probabilistic models for failure of such systems have been proposed by one of the authors of this paper earlier. This paper presents a pragmatic accelerated failure data acquisition and analytical paradigm under multi factor coupled stress, Electrical, Thermal. The parameters of the phenomenological model so developed are estimated based on sound statistical treatment of failure data.

Análise molecular vibracional da interface adesivo-dentina após aplicação de múltiplas camadas de sistemas adesivos convencionais de dois passos

O propósito do presente estudo foi analisar o efeito da aplicação de múltiplas camadas consecutivas de dois sistemas adesivos convencionais de dois passos na difusão resinosa e padrão de distribuição dos componentes monoméricos resinosos. Dezesseis terceiros molares humanos hígidos foram tratados com os sistemas adesivos convencionais de dois passos de acordo com as instruções dos fabricantes ou com aplicações em múltiplas camadas consecutivas. Os espécimes foram seccionados paralelamente aos túbulos dentinários e as superfícies submetidas ao polimento com lixas 600, 1200, 1800, 2000 e 4000. Os espectros Raman foram coletados ao longo de uma linha perpendicular a interface adesivo-resina em intervalos de 1 ou 2 m. As medidas de difusão da resina adesiva e distribuição dos componentes monomériccos foram avaliadas pelos picos Raman de 1113 cm-1, 1609 cm-1 e 1454 cm-1. O gradiente de desmineralização usado na determinação da região de hibridização foi avaliado pelo pico de 960 cm-1 da apatita. De acordo com os resultados obtidos, a aplicação de múltiplas camadas apresentou uma tendência de homogeneização dos componentes poliméricos, dependente da composição química da resina adesiva.

Avaliação in vitro de duas resinas macias para reembasamento de próteses modificadas pela incorporação de clorexidina

Resinas macias para reembasamento de próteses são largamente utilizadas após cirurgias para estabilizarem a prótese e condicionarem o tecido, aguardando a completa cicatrização. É importante que o material não seja facilmente colonizado por biofilme oral e se possível, evite a contaminação do sítio cirúrgico. Objetivou-se avaliar o efeito da incorporação de clorexidina às resinas acrílicas macias para o reembasamento de próteses totais, através de análises de liberação, citotoxicidade e efeito inibitório de um biofilme de C. albicans. Foram confeccionados corpos de provas (CDPs) com as resinas Trusoft e Coe-soft, com incorporação de 0%, 0,5%, 1,0% e 2,0% de clorexidina, totalizando 8 grupos. A liberação de clorexidina foi avaliada através da mensuração da mudança na densidade óptica da solução de armazenamento, na qual ficaram imersos os CDPs, por espectrometria UV, a cada 48 horas, durante 40 dias. A citotoxicidade celular foi avaliada em fibroblastos (linhagem L929), que ficaram 24 horas em contato com meio de cultura no qual os CDPs ficaram previamente imersos, pela técnica de absorção de corante vermelho neutro após 24, 48 e 72 horas e semanalmente até o 28 dia. E, por fim, a atividade antifúngica contra a C. albicans (ATCC 10231) foi avaliada de duas maneiras: (1) teste de difusão em ágar, no qual os CDPs foram colocados em placas de BHI previamente inoculadas com C. albicans, com medição do halo de inibição após 48 horas de incubação a 37C; (2) a avaliação da inibição da formação de um biofilme de C. albicans sobre a superfície dos CDPs pela quantificação por metil tetrazólio (MTT) a cada 48 horas, durante 22 dias, com leitura feita em espectrofotômetro de UV. Os dados obtidos foram inseridos no programa SigmaStat (versão 3.1, USA) para realizar as análises estatísticas. As diferenças estatísticas foram determinadas por análises de variâncias do tipo ANOVA e todos os procedimentos para comparações múltiplas pareadas foram feitos utilizando-se o método Holm-Sidak, com nível de significância global igual a 0,05. A clorexidina adicionada às resinas testadas foi capaz de ser liberada para o meio de armazenagem, proporcionalmente à quantidade de clorexidina incorporada, porém com diferentes cinéticas de liberação entre as resinas, visto que a Trusoft libera até 71% do total de clorexidina liberada nas primeiras 48 horas e a Coe-soft, até 44%. Ambas as resinas com incorporação de clorexidina apresentaram efeito citotóxico adicional, se comparadas às resinas sem clorexidina, porém para a Coe-soft não houve diferença estatística dos valores, apenas para a Trusoft (p<0,001). Ocorreu formação de halo de inibição proporcionalmente às concentrações de resinas adicionadas, com maiores halos para a resina Trusoft (p<0,001), e sem formação de halo para as resinas sem clorexidina; a inibição da formação de biofilme, realizada somente com a resina Coe-soft, mostrou total inibição durante 8, 12 e 16 dias, para a incorporação de 0,5%, 1,0% e 2,0% respectivamente, sendo uma diminuição estatisticamente significativa (p<0,001) em relação à resina sem incorporação de clorexidina, que não apresentou inibição do biofilme.

Hard magnetic properties of Sm3Fe26.7VxN4 and Sm3Fe26.7VxCy

Sm3Fe26.7V2.3N4 nitrides and Sm3Fe26.7V2.3Cy carbides have been synthesized by gas-solid phase reaction. Their hard magnetic properties have been investigated by means of additional ball-milling at room temperature. The saturation magnetization of Sm3Fe26.7V2.3N4 almost decreases linearly with increasing ball-milling time t, but that of Sm3Fe26.7V2.3Cy has no obvious change when the ball-milling time increases from t = 1 to 28 h. As a preliminary result, the maximum remanence B-r of 0.94 and 0.88 T, the coercivity mu(0i)H(C) of 0.75 and 0.25 T, and the maximum energy product (BH) of 108.5 and 39.1 kJ/m(3) for their resin-bonded permanent magnets are achieved, respectively, by ball-milling at 293 K. (C) 1999 Published by Elsevier Science B.V. All rights reserved.

Estudo da prevalência das alterações biológicas e mecânicas associadas à reabilitação com prótese parcial removível nas clínicas pedagógicas de Medicina Dentária da FCS-UFP

Projeto de Pós-Graduação/Dissertação apresentado à Universidade Fernando Pessoa como parte dos requisitos para obtenção do grau de Mestre em Medicina Dentária

Fracture strength of machined ceramic crowns as a function of tooth preparation design and the elastic modulus of the cement

Objectives: To determine, by means of static fracture testing the effect of the tooth preparation design and the elastic modulus of the cement on the structural integrity of the cemented machined ceramic crown-tooth complex. 
Methods: Human maxillary extracted premolar teeth were prepared for all-ceramic crowns using two preparation designs; a standard preparation in accordance with established protocols and a novel design with a flat occlusal design. All-ceramic feldspathic (Vita MK II) crowns were milled for all the preparations using a CAD/CAM system (CEREC-3). The machined all-ceramic crowns were resin bonded to the tooth structure using one of three cements with different elastic moduli: Super-Bond C&B, Rely X Unicem and Panavia F 2.0. The specimens were subjected to compressive force through a 4 mm diameter steel ball at a crosshead speed of 1 mm/min using a universal test machine (Loyds Instrument Model LRX.). The load at the fracture point was recorded for each specimen in Newtons (N). These values were compared to a control group of unprepared/unrestored teeth. 
Results: There was a significant difference between the control group, with higher fracture strength, and the cemented samples regardless of the occlusal design and the type of resin cement. There was no significant difference in mean fracture load between the two designs of occlusal preparation using Super-Bond C&B. For the Rely X Unicem and Panavia F 2.0 cements, the proposed preparation design with a flat occlusal morphology provides a system with increased fracture strength. 
Significance: The proposed novel flat design showed less dependency on the resin cement selection in relation to the fracture strength of the restored tooth. The choice of the cement resin, with respect to its modulus of elasticity, is more important in the anatomic design than in the flat design. © 2013 Academy of Dental Materials.

Bond durability in erbium:yttrium-aluminum-garnet laser-irradiated enamel

This study sought to evaluate the influence of thermocycling and water storage on the microtensile bond strength of composite resin bonded to erbium:yttrium-aluminum-garnet (Er:YAG)-irradiated and bur-prepared enamel. Eighty bovine incisors were selected and sectioned. Specimens were ground to produce a flat enamel surface. Samples were randomly assigned according to cavity preparation device: (I) Er:YAG laser and (II) high-speed turbine, and were subsequently restored with composite resin. They were subdivided according to the duration of water storage (WS)/number of thermocycles (TCs): 24 h WS/no TCs; 7 days WS/500 TCs; 1 month WS/2,000 TCs; 6 months WS/12,000 TCs. The teeth were sectioned into 1.0 mm(2)-thick slabs and subjected to tensile stress in a universal testing machine. Data were submitted to two-way analysis of variance (ANOVA) and Tukey`s test at a 0.05 significance level. The different periods of water storage and thermocycling did not influence the microtensile bond strength (A mu TBS) values in the Er:YAG laser-prepared groups. In bur-prepared enamel, the group submitted to 12,000 TCs/6 months` WS (IID) showed a significant decrease in bond strength values when compared to the group stored in water for 24 h and not submitted to thermocycling (IIA), but values were statistically similar to those obtained in all Er:YAG laser groups and in the bur- prepared groups degraded with 500 TCs/1 week WS (IIB) or 2,000 TCs/1 month WS (IIC). It may be concluded that adhesion of an etch-and-rinse adhesive to Er:YAG laser-irradiated enamel was not affected by the methods used to simulate degradation of the adhesive interface and was similar to adhesion in the bur-prepared groups in all periods of water storage and thermocycling.

Qualidade de vida, eficiência mastigatória e presença de disfunção temporomandibular em usuários de prótese parcial removível com arco dental curto inferior

Even nowadays there is in Brasil a large number of edentulous and a precarious financial condition of most of the population. In addition, World Health Organization aims for oral health, which consists on the maintenance of a natural dentition, functional and aesthetic composed of at least 20 teeth, without need of prosthetic intervention throughout life. From this and considering the lack of researches about the permanence of edentulous spaces in the oral cavity, and also avoiding overtreatment, this research has been proposed. Thus, the aim was to evaluate the effect of different lengths of the shortened lower dental arch in the presence or absence of a removable partial denture (RPD) on masticatory function, quality of life and occurrence of temporomandibular dysfunction. To achieve this goal, we compared the masticatory efficiency (colorimetric test), the oral comfort through the analysis of the impact of oral health in quality of life (OHIP-14), the presence of temporomandibular dysfunction (RDC/TMD) and the general quality of life (WHOQOL) of patients with shortened dental arches (SDA) (n=60), which is an arch with a reduction of teeth starting posteriorly, and patients with complete dental arch (Complete DA) (n = 34). The group of patients whit SDA was divided among PPR wears (PPD + SDA) (n = 17) and non-wears (n = 43). The population of this study consisted on patients who received or looked for treatment at the clinics of the Department of Dentistry of UFRN, from clinical analysis and records. The sample was chosen by convenience. For statistical analysis, it was a database in SPSS 17.0, followed by descriptive analysis with frequencies, absolute values, tests of central tendency and variability. The statistical tests used were chi-squared and analysis of variance as well as Tukey s post test, when applicable, all with a 95% confidence level. The results shown a prevalence of TMD of 47,1% among patients using PRP and 69,8% among those who didn t, but this result wasn t statistically significant. The mean of the results of masticatory efficiency, WHOQOL and OHIP didn t show association to the presence or absence of PPR and to the lower number of occlusal units of the patients (0, 1, 2 or more occlusal). The association only occurred among the different groups of SDA and the patients with complete dental arch. Taking into account the results, it could be observed that studied patients with low posterior support using lower PRP didn t have better masticatory efficiency, general quality of life, less impacts of their oral conditions in quality of life or not even less temporomandibular dysfunction or better masticatory efficiency when compared to those who didn t use the prosthesis

Avaliação clínica longitudinal do periodonto de dentes pilares e não pilares de próteses parciais removíveis

The literature has shown a relation between periodontics and the removable partial denture (RPD), with progressive destruction observed in the support structures. The aim of this study was to clinically assess periodontal condition in users of removal partial denture (RPD), and compare right abutments teeth, indirect abutments and controls before installation and after 1 year, in addition to comparing tooth-supported and tooth mucosa-supported abutments. A total of 50 patients, 32 women and 18 men, mean age of 45 years, took part in the study. The patients were examined by a single examiner at prosthesis installation and after 3, 6, 9 and 12 months. The following were verified at each examination: Probe Depth (PD), Plaque Index (PI), Gingival Index (GI), the amount of Keratinized Mucosa (KM), Gingival Recession (GR) and Dental Mobility (DM); in addition patients received oral hygiene orientation, accompanied by prophylaxis, periodontal scaling and root planing (PSRP), when necessary. Analysis of Variance (ANOVA) with Tukey-Kramer post test was used to assess the dependent variables (PD, PI, KM, GR) of the three groups over time while Friedman s test was used for GI. To assess the outcomes of prosthesis type in the right abutment group, a confidence interval-based analysis was performed. The results showed that the control group was the least compromised in all the variables studied. With respect to development of the groups over time, it was verified that the measures for GR, PD, GI and KM increased from initial examination to 1 year of use in all the groups, but only PI showed a significant increase. There was a non-discriminatory low prevalence of dental mobility. The tooth mucosa-supported prosthesis had significantly higher values for GR, GI and PI and significantly lower ones for KM when compared to tooth-supported. Over time, both types of prostheses showed no significant differences from initial to final examination for the variables GR, PD, KM and GI, with PI significant only for tooth-supported. The results showed that the teeth most involved in RPD design had greater potential of periodontal damage, probably because of greater dental biofilm accumulation. Abutments elements adjacent to the free extremities had less favorable periodontal condition than those adjacent to interpolated spaces, but the use of RPD did not worsen the initial condition

Análise comparativa na influência da técnica de moldagem funcional em arcos parcialmente edêntulos sobre os pontos de contato oclusais, a integridade da fibromucosa e a extensão da base da prótese

There is a lack of clinical studies evaluating techniques of functional impression for partially edentulous arches. The aim of this double-blind non-randomized controlled clinical trial was to compare the efficacy of altered cast impression (ACI) and direct functional impression (DFI) techniques. The efficacy was evaluated regarding the number of occlusal units on denture teeth, mucosa integrity at 24-hour follow-up and denture base extension. The sample included 51 patients (female and male) with mean age of 58.96 years treated at Dental Department of UFRN. The patients, exhibiting edentulous maxilla and mandibular Kennedy class I, were divided into two groups (group ACI, n=29; group DFI, n=22). Clinical evaluation was based on the number of occlusal units on natural and/or artificial teeth, mucosa integrity at 24-hour follow-up, and denture base extension. Statistical analysis was conducted using the software SPSS 17.0® (SPSS Inc., Chicago, Illinois). Student T-test was used to reveal association between number of occlusal units and impression technique while chi-square test showed association between mucosa integrity and impression technique. Fischer s exact test was applied for association between denture base extension and impression technique at 95% level of significance. No significant difference was observed between the groups regarding number of occlusal units, mucosa integrity and denture base extension. The altered cast technique did not provide significant improvement in comparison to the direct technique when the number of occlusal units, mucosa integrity and denture base extension