Effect of length of apical root resection on the biomechanical response of a maxillary central incisor in various occlusal relationships.

AIM: To investigate the stress distribution and tooth displacement of a maxillary central incisor with various apical root resection lengths and occlusal relationships using finite element (FE) analysis. METHODOLOGY: A maxillary central incisor was scanned by micro-CT. First, the FE intact incisor model with dentine, enamel, pulp and root surrounded by alveolar bone and periodontal ligament was designed based on the micro-CT image data. Then, six FE models with varying lengths of apical root resection were established to simulate the clinical treatment and reveal the clinically applicable limit of apical root resection during endodontic microsurgery. For each model under different loading conditions, the maximum von Mises stress (σ max) at the root apex, root cervix, alveolar bone and periodontal ligament and the maximum tooth displacement (ΔR max) were calculated and compared. RESULTS: In a normal occlusion, more than 6 mm of root resection resulted in a marked increase in the ΔR max values (>10%) and σ max values of alveolar bone (>50%); the stress levels at the root apex increased dramatically when the apical root was resected more than 7 mm. With increased overjet, apical root resection did not change the stress level markedly until it reached 8 mm, but the ΔR max increased markedly (>10%) if the root was resected more than 5 mm. With deep overbites, the σ max increased significantly (>50%) when the root was resected more than 4 mm whilst the ΔR max decreased. With increased overjet and deep overbite, more than 6 mm of resection resulted in a substantial σ max increase (>50%) of alveolar bone and the ΔR max increased markedly (>10%) when the root was resected 8 mm. Additionally, the σ max and the ΔR max values were greater with increased overjet and lower with deep overbites. CONCLUSIONS: Using FE analysis, apical root resection of more than 6 mm resulted in a marked increase of stress distribution and tooth displacement in normal and increased overjet with deep overbite occlusal relationships. In increased overjets or deep overbites, more than 5 mm or 4 mm, respectively, stress distribution and tooth displacement increased markedly.

Quick rehabilitation nursing improves the recovery of colon cancer patients after laparoscopy.

Colon cancer is a common malignant tumor with particularly high morbidity and mortality. The aim of this study was to compare the effect of quick rehabilitation nursing and routine nursing in postoperative recovery of patients with colon cancer after laparoscopic surgery. Two hundred forty patients with colon cancer were classified into four random groups (A, B, C and D, with 60 patients in each group). All patients underwent surgery to remove the colon tumor by laparoscopy under general anesthesia. Patients in groups A and B received quick rehabilitation nursing for post-surgery recovery. In group C patients, local anesthesia associated with quick rehabilitation nursing for post-surgery recovery was used. Group D was used as control group and the patients were treated based on routine nursing. Time to get out of bed, first bowel movement time and the average time of hospitalisation in group A was lower than group D (p less than 0.05), postoperative leukocyte level as well as the occurrence rate of nausea and vomiting, ankylenteron and pelvic adhesion was decreased in group A compared to group D (p less than 0.05), but the postoperative albumin and total protein level was higher than group D (p less than 0.05). The serum level of C-Reactive Protein (CRP) and interleukin 6 (IL-6) in group A was decreased compared to group D several days after surgery (p less than 0.05); group B had 4 cases of intestinal obstruction after surgery that could be cured through conservative treatment, while group D had 10 cases of intestinal obstruction, 8 of which could be cured through conservative treatment and two needed surgery (p less than 0.05); VAS for pain degree of group C in active state was clearly lower at 1h, 5h, 7h, 15h, 30h and 42h after surgery, and side effects of postoperative analgesia were clearly reduced. Time to get out of bed was obviously decreased, while there was no evident effect on postoperative dosage, chronic pain and complications. Adopting quick rehabilitation nursing can effectively reduce occurrence of complications and postoperative pain, speed up the recovery of gastrointestinal function, shorten the length of stay, and improve patients’ satisfaction.

Exploration of the mechanisms of biofilm formation by Enterococcus faecalis in glucose starvation environments.

BACKGROUND: Enterococcus faecalis is the most common single species present in teeth after failed root canal therapy. This is mainly due to its ability to maintain viability for a long time in filled root canals where nutrients are normally sparse. The aim of this study was to explore the mechanism of E. faecalis survival and biofilm formation in glucose-starved environments. METHODS: Enterococcus faecalis ATCC 33186 was inoculated in energy starvation media for biofilm formation. Confocal laser scanning microscopy and fluorescent DNA-binding agents were employed to assess biofilm-forming ability. The physiochemical properties of the biofilm cell wall were investigated by measuring the hydrophobicity, extracellular polysaccharide and ATPase activity. The expression of stress and virulence genes was quantified by real-time quantitative polymerase chain reaction. RESULTS: The ability for biofilm formation decreased with a decreasing concentration of glucose. The cell surface hydrophobicity increased dramatically with decreasing glucose concentration. Water-soluble exopolysaccharide (WSE) synthesis decreased in glucose starvation media, whereas water-insoluble exopolysaccharide (WIE) synthesis increased. A marked decrease in ATPase activity was observed only in a no glucose medium. In addition, transcription of ace, fsrB and gelE genes increased under glucose starvation stress while atpE, salB and esp genes were down-regulated. CONCLUSIONS: Enterococcus faecalis survival and biofilm formation under glucose starvation stress may be attributed to an increase in cell-surface hydrophobicity and additionally to the up-regulation of some genes involved in stress response and biofilm formation. These characteristics may explain why E. faecalis can maintain viability for a long time in an energy-starved environment and why it is frequently isolated from persistently infected root canals.