Analysis of Cutting Capacity, Surface Finishing, and Mechanical Properties of NiTi Instruments 25/.04: ROTATE and LOGIC 2.

INTRODUCTION: In an effort to enhance the quality of mechanized endodontic instruments, various thermal treatment methods, and design modifications have been suggested. However, upon evaluation, these endodontic instruments may exhibit microscopic irregularities. The objective of this in vitro study was to analyze the cutting capacity, surface finish, and mechanical properties of Nickel-Titanium 25/.04 Rotate (VDW GmbH, Munich, Germany) and LOGIC 2 (Easy Equipamentos Odontológicos, Belo Horizonte, MG, Brazil) rotary instruments. METHODOLOGY: Twenty rotary instruments were divided into 2 groups: GR, the group with ROTATE instruments (n = 10); and GL2, the group with LOGIC 2 instruments (n = 10). They were evaluated for roughness, using a profilometer, for bending resistance, buckling resistance, and cutting capacity using a universal testing machine, as well as for torsional strength (torque and angular deflection) using a torquemeter. The instruments were visualized before and after the mechanical tests through scanning electron microscopy. RESULTS: GR showed better surface finish in terms of roughness, greater cutting capacity, and greater angular deflection than GL2 (P < .05). However, GL2 showed better flexibility than GR (P < .05). GL2 and GR did not show statistically significant differences in terms of buckling and torque (P > .05). CONCLUSION: The ROTATE and LOGIC 2 rotary instruments differed in their surface finish, cutting capacity, and mechanical properties, except for their buckling resistance and required fracture torque.

Surface quality of furniture components using a band saw, milling machine, and two species / Qualidade superficial de componentes de móveis utilizando serra fita e fresadora e duas espécies

This study is dedicated to considering the use of eucalyptus and Ocotea porosa to produce classic-style furniture, assessing the machining time and surface quality. For such, the survey of data on the surface quality of eucalyptus and Ocotea porosa pieces was carried out through a visual assessment with the adaptation of the methodology described in standard ASTM 1666. This analysis of the wood surface quality occurred using two different species and two machining modalities (a band saw and a copy milling machine) for parts intended to produce components (feet) for classic furniture. After making the feet, the pieces of furniture were assembled and reassessed. Forty samples were selected and evaluated for initial defects through visual inspection, and the non-parametric Kruskal-Wallis statistical test was applied. The values found for surface quality were considered good quality, with more time being necessary to perform the finishing of the parts processed with the band saw than the milling machine. One may conclude thatthe milling time spent on each treatment influences the production capacity of the company, with the cuts carried out with the milling machine being faster and with better surface finishing.(AU)

Esse estudo dedicou-se a considerar a utilização de eucalipto e Ocotea porosa na produção de móveis em estilo clássico, avaliando o tempo de usinagem e a qualidade superficial. Para tal, foi realizado o levantamento de dados sobre a qualidade superficial de peças de eucalipto e Ocotea porosa, por meio de uma avaliação visual com adaptação da metodologia descrita na norma ASTM 1666. Essa análise da qualidade superficial da madeira ocorreu por meio de duas diferentes espécies e conduzido por duas modalidades de usinagem (uma serra-fita e uma fresadora copiadora) de peças destinadas a produção de componentes (pés) para móveis clássicos. Após a confecção dos pés os móveis foram montados e novamente avaliados. Selecionou-se 40 amostras, nas quais foram avaliados os defeitos iniciais por meioda inspeção visual, foi aplicada a estatística não paramétrica de Kruskal-Wallis. Os valores encontrados sobre a qualidade de superfície foram considerados de boa qualidade, sendo necessário maior tempo para realizar o acabamento nas peças processadas na serra-fita se comparado com a fresadora. Pôde-se concluir que o tempo de usinagem gasto em cada tratamento influencia na capacidade de produção da empresa, sendo mais rápidos os cortes realizados pela fresadora com melhor acabamento superficial.(AU)

Surface quality of furniture components using a band saw, milling machine, and two species / Qualidade superficial de componentes de móveis utilizando serra fita e fresadora e duas espécies

This study is dedicated to considering the use of eucalyptus and Ocotea porosa to produce classic-style furniture, assessing the machining time and surface quality. For such, the survey of data on the surface quality of eucalyptus and Ocotea porosa pieces was carried out through a visual assessment with the adaptation of the methodology described in standard ASTM 1666. This analysis of the wood surface quality occurred using two different species and two machining modalities (a band saw and a copy milling machine) for parts intended to produce components (feet) for classic furniture. After making the feet, the pieces of furniture were assembled and reassessed. Forty samples were selected and evaluated for initial defects through visual inspection, and the non-parametric Kruskal-Wallis statistical test was applied. The values found for surface quality were considered good quality, with more time being necessary to perform the finishing of the parts processed with the band saw than the milling machine. One may conclude thatthe milling time spent on each treatment influences the production capacity of the company, with the cuts carried out with the milling machine being faster and with better surface finishing.

Esse estudo dedicou-se a considerar a utilização de eucalipto e Ocotea porosa na produção de móveis em estilo clássico, avaliando o tempo de usinagem e a qualidade superficial. Para tal, foi realizado o levantamento de dados sobre a qualidade superficial de peças de eucalipto e Ocotea porosa, por meio de uma avaliação visual com adaptação da metodologia descrita na norma ASTM 1666. Essa análise da qualidade superficial da madeira ocorreu por meio de duas diferentes espécies e conduzido por duas modalidades de usinagem (uma serra-fita e uma fresadora copiadora) de peças destinadas a produção de componentes (pés) para móveis clássicos. Após a confecção dos pés os móveis foram montados e novamente avaliados. Selecionou-se 40 amostras, nas quais foram avaliados os defeitos iniciais por meioda inspeção visual, foi aplicada a estatística não paramétrica de Kruskal-Wallis. Os valores encontrados sobre a qualidade de superfície foram considerados de boa qualidade, sendo necessário maior tempo para realizar o acabamento nas peças processadas na serra-fita se comparado com a fresadora. Pôde-se concluir que o tempo de usinagem gasto em cada tratamento influencia na capacidade de produção da empresa, sendo mais rápidos os cortes realizados pela fresadora com melhor acabamento superficial.

Oral exfoliative cytology and corrosion of metal piercings. Tissue implications.

OBJECTIVES: A group of adolescents with oral piercings was studied to determine the presence of metallic particles in cells exfoliated from the mucosa surrounding their metal oral piercings and the association between such particles and the metal jewelry, and to evaluate subsequent tissue implications. MATERIALS AND METHODS: Sixteen teenage patients who had tongue and/or lip piercings were included. The clinical features of the oral mucosa and lip skin were evaluated. Exfoliative cytology was performed in the area surrounding the piercing. The surface of used and unused jewelry was studied by scanning electron microscopy and energy dispersive X-ray analysis. RESULTS: Hyperplastic, leukoedematous, and lichenoid lesions were observed in the mucosa, as well as lesions associated with metallosis of the lip skin. Cytological smears showed the presence of particles inside the epithelial cells; the particles were found to contain aluminum, tungsten, and molybdenum. In one case requiring surgical removal of the piercing, histological examination of the tissue associated with the piece of jewelry showed the presence particles containing aluminum, iron, and tin inside multinucleated giant cells. Although surface finish defects were observed on both unused and used piercing jewelry, they were more evident on the used pieces. CONCLUSIONS: Ion particles are released from the metal piercings and could have been adjuvant factors in the development of the observed lesions. Cells exfoliated from the oral mucosa surrounding metal piercings may serve as bioindicators of corrosion processes. CLINICAL RELEVANCE: We propose the use of exfoliative cytology to monitor corrosion processes and for routine clinical follow up.

Evaluation of Surface Finish and Dimensional Control of Tribological Metal-Ultra High Molecular Weight Polyethylene Pair of Commercially Available Hip Implants.

BACKGROUND: Dimensional control and surface finish of the femoral head and acetabular liner are critical factors in the manufacturing process due to the risk of increased polyethylene wear, which is the primary cause of aseptic failure of a metal/polymer hip prosthesis. The aim of this study is to perform a dimensional and surface finish analysis to evaluate the reproduction and accuracy of the manufacturing processes of metal femoral heads and ultra high molecular weight polyethylene acetabular liners. METHODS: Four femoral heads and acetabular liners from 5 manufacturers were evaluated. The methods of evaluation followed the standards ISO 7206-2:2011 and ISO 21535:2010. RESULTS: The diameter, sphericity, and roughness of the femoral heads from all the manufacturers were in accordance with the standard requirements. Only the sphericity showed a lack of repeatability among the manufacturers. The variability in sphericity was high among some manufacturers and low in others. The diameters of the acetabular liners of 2 manufacturers were not in accordance with the standard requirements. The repeatability of sphericity, thickness, and roughness of the acetabular liners were heterogeneous among the manufacturers, which means that some manufacturers need to improve quality control. CONCLUSION: Our results showed a good dimensional and surface finish control of the manufacturing processes of the femoral heads. However, the same control was not shown during the manufacturing of the acetabular liners although all samples had a thickness and sphericity in accordance with the standard. A better quality control of the manufacturing process of ultra high molecular weight polyethylene acetabular liners should be made to improve the dimensional parameters of the acetabular liners and the tribological pair.

Influence of Surface Roughness on the Fatigue Life of Nickel-Titanium Rotary Endodontic Instruments.

INTRODUCTION: The goal of the present study was to evaluate the influence of surface grooves (peaks and valleys) resulting from machining during the manufacturing process of polished and unpolished nickel-titanium BR4C endodontic files on the fatigue life of the instruments. METHODS: Ten electropolished and 10 unpolished endodontic files were provided by the manufacturer. Specimens were from the same batch, but the unpolished instruments were removed from the production line before surface treatment. The instruments were evaluated with a profilometer to quantify the surface roughness on the working part of the instruments. Then the files were subjected to rotating bending fatigue tests. RESULTS: Analysis with the profilometer showed that surface grooves were deeper on the unpolished instruments compared with their electropolished counterparts. In the rotating bending fatigue test, the mean and standard deviation for the number of cycles until fracture (NCF) were greater for instruments with less pronounced grooves. Student t test revealed significant differences in all tests (P < .05). CONCLUSIONS: The results from the present study showed that the depth of the surface grooves on the working part affected the NCF of the instruments tested; the smaller the groove depth, the greater the NCF.