Concepts of occlusion in prosthodontics: A literature review,part I

Occlusion and its relationship to the function of the stomatognathic system have been widely studied in dentistry since many decades. This series of articles describe about occlusion in the complete denture, fixed partial denture, and implants. Part I and II of this articles series describe concepts and philosophies of occlusion in complete denture. So far, available research has not concluded a superior tooth form or occlusal scheme to satisfy the requirements of completely edentulous patients with respect to comfort, mastication, phonetics, and esthetics. Since then, several balanced and nonbalanced articulation concepts were proposed in the literature. A balanced articulation appears to be most appropriate because of tooth contacts observed during nonfunctional activities of patients. This article discusses about evolution of different concepts of occlusion and occlusal schemes in complete denture occlusion.Key Words: Articulation, complete denture, occlusion     

A Finite Element Analysis of Stress Distribution in the Bone, Around the Implant Supporting a Mandibular Overdenture with Ball/O Ring and Magnetic Attachment

Today implant dentistry has made great inroads into the treatment modalities that are available in treating an edentulous patient. Popularity of a two implant retained overdenture has created a necessity to examine the various attachment systems being used and the stresses that are transmitted to the alveolar bone. Hence a Three dimensional Finite Element Analysis was done to analyze the stress distribution in the mandibular bone with implant-supported overdenture having Ball/O-ring and Magnet attachments of different diameters. A segment of the anterior region of the mandible was modeled with implant and the overdenture. Four different models were generated having Ball/O-Ring and Magnet Attachments. Forces of 10 N, 35 N and 70 N were applied from the horizontal, vertical and oblique directions respectively and the stress distribution studied. It was concluded that the greatest stress concentrations were seen at the crest of the cortical bone and could be reduced by using smaller sized attachments for implant supported-overdenture.     

Genistein, a soy phytoestrogen, reverses severe pulmonary hypertension and prevents right heart failure in rats

Pretreatment with a phytoestrogen genistein has been shown to attenuate the development of pulmonary hypertension (PH). Because PH is not always diagnosed early, we examined whether genistein could also reverse preexisting established PH and prevent associated right heart failure (RHF). PH was induced in male rats by 60 mg/kg of monocrotaline. After 21 days, when PH was well established, rats received daily injection of genistein (1 mg/kg per day) for 10 days or were left untreated to develop RHF by day 30. Effects of genistein on human pulmonary artery smooth muscle cell and endothelial cell proliferation and neonatal rat ventricular myocyte hypertrophy were assessed in vitro. Severe PH was evident 21 days after monocrotaline, as peak systolic right ventricular pressure increased to 66.35±1.03 mm Hg and right ventricular ejection fraction reduced to 41.99±1.27%. PH progressed to RHF by day 30 (right ventricular pressure, 72.41±1.87 mm Hg; RV ejection fraction, 29.25±0.88%), and mortality was ≈75% in RHF rats. Genistein therapy resulted in significant improvement in lung and heart function as right ventricular pressure was significantly reduced to 43.34±4.08 mm Hg and right ventricular ejection fraction was fully restored to 65.67±1.08% similar to control. Genistein reversed PH-induced pulmonary vascular remodeling in vivo and inhibited human pulmonary artery smooth muscle cell proliferation by ≈50% in vitro likely through estrogen receptor-β. Genistein also reversed right ventricular hypertrophy (right ventricular hypertrophy index, 0.35±0.029 versus 0.70±0.080 in RHF), inhibited neonatal rat ventricular myocyte hypertrophy, and restored PH-induced loss of capillaries in the right ventricle. These improvements in cardiopulmonary function and structure resulted in 100% survival by day 30. Genistein restored PH-induced downregulation of estrogen receptor-β expression in the right ventricle and lung. In conclusion, genistein therapy not only rescues preexisting severe PH but also prevents the progression of severe PH to RHF.     

Reliability of the rabbit postero‐lateral spinal fusion model: A meta‐analysis

The rabbit model of spinal fusion with the autogenous iliac crest bone graft (ICBG) control is widely used to evaluate bone graft substitutes and enhancers. This study examined the reliability of this model using meta‐analysis. A systematic literature search from January 1995 to May 2011 identified 56 studies, involving 733 animals. The primary outcome was fusion success calculated as logit event rate. Study design, surgical technique, rabbit characteristics (gender, species, age, weight), and institution were analyzed. Overall fusion success was 52.4%. Important positive variables were time‐point >4 weeks, ICBG dose >1 cm³, initial weight of animals ≥3 kg, level at L4‐5 or L5‐6, and age ≥6 months. Inter‐ and intra‐institutional reliability was excellent. The rabbit model ICBG control group is reliable, although several factors can affect results. Fusion under normal handling occurs reliably in 5 weeks. The volume of bone graft should be >1 cm³ but no benefits are present with >2 cm³. The animals should weigh a minimum of 3 kg and be at least 6 months old. © 2013 Orthopaedic Research Society Published by Wiley Periodicals, Inc. J Orthop Res 31:1261–1269, 2013     

Escherichia coli DNA polymerase II catalyzes chromosomal and episomal DNA synthesis in vivo

We have investigated a role for Escherichia coli DNA polymerase II (Pol II) in copying chromosomal and episomal DNA in dividing cells in vivo. Forward mutation frequencies and rates were measured at two chromosomal loci, rpoB and gyrA, and base substitution and frameshift mutation frequencies were measured on an F′(lacZ) episome. To amplify any differences in polymerase error rates, methyl-directed mismatch repair was inactivated. When wild-type Pol II (polB⁺) was replaced on the chromosome by a proofreading-defective Pol II exo⁻ (polBex1), there was a significant increase in mutation frequencies to rifampicin resistance (Rif^R) (rpoB) and nalidixic acid resistance (Nal^R) (gyrA). This increased mutagenesis occurred in the presence of an antimutator allele of E. coli DNA polymerase III (Pol III) (dnaE915), but not in the presence of wild-type Pol III (dnaE⁺), suggesting that Pol II can compete effectively with DnaE915 but not with DnaE⁺. Sequencing the Rif^R mutants revealed a G → A hot spot highly specific to Pol II exo⁻. Pol II exo⁻ caused a significant increase in the frequency of base substitution and frameshift mutations on F′ episomes, even in dnaE⁺ cells, suggesting that Pol II is able to compete with Pol III for DNA synthesis on F episomes.     

Improved Sensitivity for Molecular Detection of Bacterial and Candida Infections in Blood

The rapid identification of bacteria and fungi directly from the blood of patients with suspected bloodstream infections aids in diagnosis and guides treatment decisions. The development of an automated, rapid, and sensitive molecular technology capable of detecting the diverse agents of such infections at low titers has been challenging, due in part to the high background of genomic DNA in blood. PCR followed by electrospray ionization mass spectrometry (PCR/ESI-MS) allows for the rapid and accurate identification of microorganisms but with a sensitivity of about 50% compared to that of culture when using 1-ml whole-blood specimens. Here, we describe a new integrated specimen preparation technology that substantially improves the sensitivity of PCR/ESI-MS analysis. An efficient lysis method and automated DNA purification system were designed for processing 5 ml of whole blood. In addition, PCR amplification formulations were optimized to tolerate high levels of human DNA. An analysis of 331 specimens collected from patients with suspected bloodstream infections resulted in 35 PCR/ESI-MS-positive specimens (10.6%) compared to 18 positive by culture (5.4%). PCR/ESI-MS was 83% sensitive and 94% specific compared to culture. Replicate PCR/ESI-MS testing from a second aliquot of the PCR/ESI-MS-positive/culture-negative specimens corroborated the initial findings in most cases, resulting in increased sensitivity (91%) and specificity (99%) when confirmed detections were considered true positives. The integrated solution described here has the potential to provide rapid detection and identification of organisms responsible for bloodstream infections.     

Perforation of Jejunal Diverticula in Steroids and Nonsteroidal Anti-Inflammatory Drug Abusers: A Case Series

INTRODUCTION: Jejunal diverticula are rare lesions, and when complications arise, they pose diagnostic difficulties. Perforation is a common complication resulting in an acute abdomen, although preoperative diagnosis is usually not possible. The "gold standard" for management for patients with complications is surgery. We present a series of patients with perforated jejunal diverticula who were on prolonged treatment with nonsteroidal anti-inflammatory drugs (NSAIDs) and steroids for Chikungunya fever. METHODS: There were a total of six patients, all of them presenting with perforative peritonitis, with or without shock. Plain abdominal radiogram and ultrasonogram confirmed this, although the exact site of the perforation was not diagnosed preoperatively. All patients underwent exploratory laparotomy and perforated jejunal diverticulum was found. Resection and anastomosis was performed in all cases. RESULTS: The mean operating time was 113.5 minutes, and the blood loss was not significant. Postoperative course was uneventful except wound infection in two patients. There was no mortality. CONCLUSIONS: Prolonged NSAID and steroid use are known to cause ulceration/perforation of the upper digestive tract and colonic diverticula. This seems to be the most likely cause for the perforation of jejunal diverticula in our series of patients. This view is supported by the absence of inflammation and infiltration of neutrophils on histopathological examination of the diverticula.