ABSTRACT
PURPOSE: The midline fracture of maxillary complete dentures is a frequently encountered complication. The purpose of this study was to assess the effect of frenulum height on midline strains of maxillary complete dentures. MATERIALS AND METHODS: A removable maxillary complete denture was fabricated and duplicated seven times. Four different labial frenulum heights were tested for stresses occurring on the palatal cameo surface. The strains were measured with strain gauges placed on 5 different locations and the stresses were calculated. To mimic occlusal forces bilaterally 100 N of load was applied from the premolar and molar region. RESULTS: A statistically significant association between the height of the labial frenulum and the calculated stresses and strains was shown (P<.05) predominantly on the midline and especially on the incisive papilla. The results showed that stress on the anterior midline of the maxillary complete denture increases with a higher labial frenulum. CONCLUSION: Within the limitations of this in vitro study, it can be concluded that the stress on the anterior midline of the maxillary complete denture increases with a higher labial frenulum. Surgical or mechanical precautions should be taken to prevent short-term failure of maxillary complete dentures due to stress concentration and low cycle fatigue tendency at the labial frenulum region.
Subject(s)
Bicuspid , Bite Force , Denture Bases , Denture, Complete , Dentures , Fatigue , Molar , PalateABSTRACT
?Objective: To study the stress distribution of one segment type mono dowel implant with various length and diameter in alveolar bone. Methods: The thickness of cortical bone is 1～2 mm, implant was in close contact with alveolar bone directly. Implants with root length of 10,12,13 and 14 mm, cast diameter of 3.6, 3.7, 3.8, 3.9 and 4.0 mm, corona tall 4 and 9 mm were put into a bone model with alveolar bone. 200 N force was loaded in vertical, 45? oblique and 45? oblique of non center. CT and 3D FEM were used to study the stress distribution and selected the morphology of alveolar bone from first molar of lower jaw and an incisor of maxillary. Results: There was an area of stress in the boundary of the cortical and cancellous bony tissue,horizontal hole. The main region of stress was at the cancellous. Thickness and shape of alveolar bone could affect the distribution of stress. The maximal Von Mises Stress was always in the boundary of cortical and bone that contacted with implant. Higher elastic modulus of bone around the implant had higher stress in cortical stress . Conclusion: The stress of cortical and cancellous bone can be depressed to rise elastic modulus of implant.
ABSTRACT
The incidences of diseases related to mental stress are increasing in Japan. Mental stress, unacknowledged for long periods, has been shown to lead to the development of a number of diseases. Thus, an index for mental stress is important to induce awareness of its presence. We focused on the relationship between cortisol and mental stress in this review. We will discuss both the usefulness and problems of cortisol as a mental stress index by summarizing the relationship between cortisol and mental stress. The present findings suggested that cortisol appears to be an adequate index for mental stress. However, there are several problems; the present group clarifies these problems and builds the comprehensive mental stress assessment systems by using saliva samples.