Thermal expansion and corrosion resistance of cobalt-chromium alloys fabricated by contemporary manufacturing processes: an in vitro study / Expansión térmica y resistencia a la corrosión de aleaciones de cobalto-cromo fabricadas mediante procesos de abricación contemporáneos: un estudio in vitro

In Purpose: The fabrication technique can influence the mechanical properties of Cobalt-Chromium (Co-Cr) dental alloys. Hence, the present study aims to determine the corrosion resistance and thermal expansion of alloys manufactured using three contemporary techniques. Material and Methods: A total of nine specimens of Co-Cr alloy were prepared according to ISO 22674 by each one of the three manufacturing processes (three in each process); conventional casting, direct metal laser sintering (DMLS) and milling (MIL). All these specimens were tested for coefficient of thermal expansion and corrosion resistance. The data was tabulated and analyzed statistically. Results: The difference in the thermal expansion of alloys fabricated using three techniques was non-significant at almost all the temperatures from 50 ºC to 950 ºC (p>0.05), except 450 ºC and 600 °C. The polarization resistance of specimens manufactured using the conventional method was more compared to DMLS and MIL at pH 5 (Conventional>MIL>DMLS) (p<0.001). Conclusion: The thermal expansion behavior of alloys manufactured using the three selected techniques were similar, whereas, at acidic pH, the corrosion resistance of conventional and MIL were better than the DMLS.

Antecedentes: La técnica de fabricación puede influir en las propiedades mecánicas de las aleaciones dentales de cobalto-cromo (Co-Cr). Por lo tanto, el presente estudio tiene como objetivo determinar la resistencia a la corrosión y la expansión térmica de aleaciones fabricadas con tres técnicas contemporáneas. Material y Métodos: Se prepararon un total de nueve probetas de aleación de Co-Cr según ISO 22674 por cada uno de los tres procesos de fabricación (tres en cada proceso); fundición convencional, sinterización directa de metal por láser (DMLS) y fresado (MIL). Todos estos especímenes fueron probados para determinar el coeficiente de expansión térmica y la resistencia a la corrosión. Los datos fueron tabulados y analizados estadísticamente. Resultados: La diferencia en la dilatación térmica de las aleaciones fabricadas con las tres técnicas no fue significativa en casi todas las temperaturas desde 50ºC hasta 950ºC (p>0,05), excepto 450ºC y 600ºC. La resistencia a la polarización de las muestras fabricadas con el método convencional fue mayor en comparación con DMLS y MIL a pH 5 (Convencional>MIL>DMLS) (p<0, 0 01). Conclusión: El comportamiento de expansión térmica de las aleaciones fabricadas con las tres técnicas seleccionadas fue similar, mientras que, a pH ácido, la resistencia a la corrosión de la convencional y la MIL fue mejor que la de la DMLS.

Clinical utility of multiplex ligation-dependent probe amplification technique in identification of aetiology of unexplained mental retardation: A study in 203 Indian patients.

Background & objectives: Developmental delay (DD)/mental retardation also described as intellectual disability (ID), is seen in 1-3 per cent of general population. Diagnosis continues to be a challenge at clinical level. With the advancement of new molecular cytogenetic techniques such as cytogenetic microarray (CMA), multiplex ligation-dependent probe amplification (MLPA) techniques, many microdeletion/microduplication syndromes with DD/ID are now delineated. MLPA technique can probe 40-50 genomic regions in a single reaction and is being used for evaluation of cases with DD/ID. In this study we evaluated the clinical utility of MLPA techniques with different probe sets to identify the aetiology of unexplained mental retardation in patients with ID/DD. Methods: A total of 203 randomly selected DD/ID cases with/without malformations were studied. MLPA probe sets for subtelomeric regions (P070/P036) and common microdeletions/microduplications (P245-A2) and X-chromosome (P106) were used. Positive cases with MLPA technique were confirmed using either fl uorescence in situ hybridization (FISH) or follow up confirmatory MLPA probe sets. Results: The overall detection rate was found to be 9.3 per cent (19 out of 203). The detection rates were 6.9 and 7.4 per cent for common microdeletion/microduplication and subtelomeric probe sets, respectively. No abnormality was detected with probe set for X-linked ID. The subtelomeric abnormalities detected included deletions of 1p36.33, 4p, 5p, 9p, 9q, 13q telomeric regions and duplication of 9pter. The deletions/duplications detected in non telomeric regions include regions for Prader Willi/Angelman regions, Williams syndrome, Smith Magenis syndrome and Velocardiofacial syndrome. Interpretation & conclusions: Our results show that the use of P245-A2 and P070/P036-E1 probes gives good diagnostic yield. Though MLPA cannot probe the whole genome like cytogenetic microarray, due to its ease and relative low cost it is an important technique for evaluation of cases with DD/ID.

Cephalometric Comparison of Frankforts Horizontal Plane And Occlusal Plane With Variations In Ala- Tragus Line.

The glossary of prosthodontic terms defines occlusal plane as an average plane established by the incisal and occlusal surfaces of the teeth. Generally, it is not a plane but represents the planar mean of the curvature of these surfaces. Another definition defines it as the surface of wax occlusion rims contoured to guide in the arrangement of denture teeth. Ala-tragus line according to the glossary of prosthodontic terms is defined as a line running from the inferior border of the ala of the nose to some defined point on the tragus of the ear, usually considered to be the tip of the tragus. It is frequently used, with a third point on the opposing tragus, for the purpose of establishing the ala-tragus plane. Ideally, the ala-tragus plane is considered to be parallel to the occlusal plane. The occlusal plane is at an angle of approximately 10 degrees relative to the Frankfort horizontal plane, when viewed in midsagittal plane. No precise, scientific method exists for determining the level of the occlusal plane in edentulous patients. Several principles have been postulated for determining the occlusal plane. The use of ala-tragus line to orient the occlusal plane has been controversial. This controversy is primarily due to disagreement on the exact point of reference for this line.Therefore the main objective of this study was to find out a reference line most parallel to the natural occlusal plane so that this reference point on the tragus can be used to determine the occlusal plane during the fabrication of complete denture

Polydactyly and genes.

Pediatricians deal with cases with the congenital malformations and malformation syndromes interest many of them. A lot of information about genes involved in development is available now. Genetics of hand development and genes involved in polydactyly syndromes is discussed in this article as a prototype to know about genetics of malformations: how it is studied and what is known. Genetic and chromosomal defects are often associated with congenital malformations. Polydactyly is one of the commonly seen malformations and genetic defects of many malformation syndromes associated with polydactyly are known. The role of genetic defect in polydactyly syndromes and the correlation between genotypes and phenotypes is discussed in this review article.

Asphyxiating thoracic dystrophy with facial dysmorphism.

Here it is reported a male newborn baby with features of asphyxiating thoracic dystrophy (ATD) with facial dysmorphism. The disproportionate rhizomelic short stature, narrow thorax, long fibulae, wide metaphysis and trident acetabule are consistent with diagnosis of ATD. In addition the baby had facial dysmorphism and broad thumbs and great toes similar to Oto-palato-digital syndrome type II (OPD II). The association of these features with ATD is not reported till date.

Ring chromosome 13 in an infant with ambiguous genitalia.

Ring chromosome is a rare chromosomal abnormality. We report a case of ring chromosome 13 associated with ambiguous genitalia. Karyotype is the important investigation in the evaluation of a case with ambiguous genitalia and chromosomal analysis should not be limited to only presence of X and Y chromosomes.

TNFR2 gene polymorphism in coronary artery disease.

BACKGROUND: Recently atherosclerosis and coronary artery disease (CAD) are considered to be inflammatory diseases. The genetic polymorphism in inflammatory markers has been well studied and found to be associated with development of CAD. AIM: To study the association of biallelic polymorphism at position 196 in exon 6 of tumor necrosis factor 2 (TNFR2) gene and coronary artery disease. SETTINGS AND DESIGN: The study design was a prospective case control study conducted at a tertiary referral center mainly catering to the north Indian population. MATERIALS AND METHODS: One hundred and fifty angiographically proven patients with coronary artery disease and one hundred and fifty age matched controls were genotyped for TNFR2 gene by polymerase chain reaction followed by analysis of restriction fragment length polymorphism. STATISTICAL ANALYSIS: Genotype frequencies were compared in patients and controls by Chi-square test. Binary logistic regression analysis was used to examine the relationship between genotypes and disease, incorporating other variables into the model. RESULTS: The incidence of CAD in those with MM genotype was 65% and in those with RM genotype was 42%. Genotype frequency shows significant association of MM genotype with development of CAD (P < 0.001; odds ratio-2.585; 95% confidence interval 1.533-4.359). The association of TNFR2 genotype with CAD persisted on logistic regression analysis. CONCLUSION: MM genotype of TNFR2 gene is associated with development of CAD and RM genotype appears to be protective.

T1 and M1 polymorphism in glutathione S-transferase gene and coronary artery disease in North Indian population.

BACKGROUND: DNA damage has been found to play an important role in atherosclerosis and coronary artery disease. Genetic polymorphisms of the genes coding for enzymes involved in the metabolism of genotoxins result in different phenotypes with respect to their ability to detoxify these agents. In the present study the contribution of the polymorphism in the glutathione S-transferase gene to the development of coronary artery disease has been investigated. METHODS: One hundred and ninety seven angiographically proven patients with coronary artery disease and one hundred and ninety eight age-matched controls were genotyped for glutathione S- transferase polymorphism by polymerase chain reaction. Genotype frequencies were compared in patients and controls by Chi-square test. Binary logistic regression was used to examine the relationship between genotype and disease, incorporating other variables into the model. RESULTS: GSTT1 null genotype was significantly decreased in patients with coronary artery disease. No significant association was found with GSTM1 genotypes. No such association was seen with smokers. CONCLUSION: Null genotype of GSTT1 is protective against coronary artery disease in our population.