ABSTRACT
The purpose of this study was pertinent design of the framework of the fixed bone anchored bridge using implants in the edentulous mandible through analysis of stress distribution by the three dimensional finite element analysis method. The results were as follows: 1. The L-shaped framework was favorable in restoring the edentulous mandible by implants and fixed bone anchored bridge. 2. The structure of the framework should be designed to endure the occlusal load because of stress concentration at the most distal abutment of the framework. 3. The stress at the distal implant where cantilever starts was twice as much as that of other portions. 4. Compressive stress was generated on the framework of the mesial side of the distal implant and extrusive force was induced to the mesially positioned implants. 5. The height of vertical plate was high as possible as can be to distribute stresses concentrating bucco-lingually and labio-lingually in the framework between abutments, 6. Reinforcement of the horizontal plate thickness was needed because stress was loaded more on the horizontal plate than on the vertical plate of the framework. 7. Lengthening of the vertical plate can compensate for any limitations in horizontal plate width.
Subject(s)
Dental Implants , Finite Element Analysis , Mandible , Suture AnchorsABSTRACT
Although attachments have been utilized for a retainer of removable prostheses during several decades, there is little information on the force distribution by the attachments. This study was undertaken to evaluate the stress patterns developed by partial dentures employing rigid attachments on the supporting structures. Four types of the mandibular removable partial dentures were designed depending upon the position of the rigid attachment and the existency of lingual bracing. Under 100N of vertical and 25N of lateral loads on the 1st and 2nd lower molar of partial denture, stress distribution patterns and displacement were analysed with three dimensional finite element method by ANSYS version 5.3. 1. The highest stresses were concentrated on the distal alveolar crest of posterior abutment and the second stresses on the apical region of posterior abutment in the models. 2. The greatest displacement were shown on the distal alveolar crest of posterior abutment and the second displacement on the distal alveolar crest of anterior abutment in the models. 3. There was little difference between the models with intraoral attachment and those with extracoronal attachment. 4. There was little difference between the models with and without the lingual bracing.
Subject(s)
Braces , Denture, Partial , Denture, Partial, Removable , Molar , Prostheses and ImplantsABSTRACT
Subject(s)
Female , Humans , Middle Aged , Antibodies, Antinuclear , Arthritis, Rheumatoid , Autoimmune Diseases , Biopsy , Brain , Butterflies , Drug Therapy , Endothelium , Immune System , Liver , Lupus Erythematosus, Systemic , Lymph Nodes , Lymphoma , Maxilla , Oncogenic Viruses , Sjogren's SyndromeABSTRACT
Epidemiological evidence suggests that human papillomavirus(HPV) infection is a high risk factor for the development of oral cancers. Many oncogenes, especially p53 suppressor gene, have a critical role of carcinogenesis in several human cancers including oral cancers. To investigate the prevalence of HPV infection and subtyping of high risk group(HPV-16, -18 and -33) HPV in oral cancers, the author studied 31 cases of squamous cell carcinomas arising from the oral cavity using polymerase chain reaction (PCR). The author also demonstrated the overexpression of p53 oncoprotein in the oral cancers using immunohistochemical methods. The correlation between HPVs infection and p53 overexpression in tumorigenesis of the oral cancers was evaluated. 1. Twenty-one cases(66.7%) among 31 cases of oral squamous cell carcinomas were positive for HPV-DNA. Among them, 16 cases were positive for HPV-16, 4 cases for HPV-18, and 2 cases for HPV-33. Two cases were coinfected with HPV-16 and HPV-18, and HPV-18 and HPV-33. 2. The prevalence of HPV infection appeared not correlated with tumor differentiation and clinical stages of oral squamous cell carcinomas. 3. The overexpression of p53 oncoprotein was present in 24 of 31 cases(77% ). In 21 HPV positive tumors 18 cases were positive for overexpression of p53 oncoprotein. Six cases were positive for p53 in ten HPV negative tumors. There was no correlation between HPV DNA detection rate and p53 overexpression. The above results suggest that HPV infection and p53 oncogene mutation play different roles in tumorigenesis of oral squamous cell carcinomas. No coexpression of p53 oncoprotein with HPV-DNA detection suggests that another etiologic mechanism other than HPV infection may be operative.