The incidence of the abutment screw loosening and its affecting factors in posterior implant restorations / 대한치과보철학회지

PURPOSE: This study was to assess clinically the incidence of abutment screw loosening of posterior implant-supported fixed prosthesis and its affecting factors. MATERIALS AND METHODS: 391 implant-supported crowns restored from January 2013 to January 2016 were included in this study. All restorations were fabricated with either a single crowns or a splinted crown, and cemented with temporary cement. The incidence of abutment screw loosening is investigated and gender, restoration position, opposing teeth, restoration type, abutment connection type were assessed as possible factors affecting abutment screw loosening. RESULTS: During the observation period (2 – 5 years), abutment screw loosening was found in 29 restorations (7.4%). It took 3 to 48 months (means 19.5 months) to loose the screw, and three of these implants were fractured. Among the factors considered, there were statistically significant differences at abutment screw loosening rate between molar group (9.4%) and premolar group (2.6%) (P<.019). According to the type of opposing teeth, there were statistically significant differences between nature teeth (74.7%) and implant (25.0%), removable denture (3%) (P<.019). The other possible factors did not have a significant effect on loosening of the abutment. CONCLUSION: The incidence of abutment screw loosening in posterior restoration was 7.4%. Abutment screw loosening were more likely to occur in molars group than premolar group, and according to the opposing teeth, there were the greatest frequency in nature teeth than implant and removal denture. There was a statistically significant difference.

Prenatal Development of Human Lip with Immunohistochemical Study

BACKGROUND: This study is aimed to elucidate the developmental pattern of human fetal lip by histological and immunohistochemical examinations. METHODS: Totally 231 normal human lip tissues obtained from autopsied fetuses were fixed with 10% buffered formalin, sectioned in cross and longitudinal directions, routinely stained for H&E and performed for immunohistochemistry with antibodies of S-100 protein, proliferating cell nuclear antigen (PCNA), transglutaminase C (TGase-C), metalloproteinase (MMP)-3, MMP-10, tenascin, KL1, K8.12, E-cadherin, tissue inhibitors of matrix metalloproteinase (TIMP)-1, TIMP-2 and total keratin (TK). RESULTS: The lip structure first appeared as an orifice of stomodeum around the 7-8th week of gestation, and a major structure of the midface was observed by the 11-12th week. As the squamous epithelium of the lip became thick and was keratinized, the vermilion border became distinguished in the 15-16th week, and the lip structure was almost completed with the presence of orbicularis oris muscle in the lingual side of vermilion border by the 17-18th week. Immunohistochemically, the vermilion border showed strong reactions for tenascin, E-cadherin and MMP-3 and increased positivity for PCNA, cytokeratins (TK, KL1, K8.12), and TGase-C. CONCLUSIONS: With the above findings we suppose that the cytodifferentiation of vermilion border epithelium plays an important role for the development of human fetal lip.