DNA glycosylases: in DNA repair and beyond

The base excision repair machinery protects DNA in cells from the damaging effects of oxidation, alkylation, and deamination; it is specialized to fix single-base damage in the form of small chemical modifications. Base modifications can be mutagenic and/or cytotoxic, depending on how they interfere with the template function of the DNA during replication and transcription. DNA glycosylases play a key role in the elimination of such DNA lesions; they recognize and excise damaged bases, thereby initiating a repair process that restores the regular DNA structure with high accuracy. All glycosylases share a common mode of action for damage recognition; they flip bases out of the DNA helix into a selective active site pocket, the architecture of which permits a sensitive detection of even minor base irregularities. Within the past few years, it has become clear that nature has exploited this ability to read the chemical structure of DNA bases for purposes other than canonical DNA repair. DNA glycosylases have been brought into context with molecular processes relating to innate and adaptive immunity as well as to the control of DNA methylation and epigenetic stability. Here, we summarize the key structural and mechanistic features of DNA glycosylases with a special focus on the mammalian enzymes, and then review the evidence for the newly emerging biological functions beyond the protection of genome integrity

Prospective Clinical Assessment of Pulp Sensitivity After Chin Bone Harvesting

Proposal: Evaluate pulp vitality of mandibular teeth after chin bone harvesting. Materials and Methods: Thirty patients underwent chin bone harvesting and accompanied for 12 months, being submitted to testing for pulp vitality with Endo Ice refrigerant spray to produce a local temperature of -50 degrees C. The statistical analysis was executed with McNemar test with P value < 0.05. Results: Results show that canine teeth are most susceptible to alterations; 68.82% (181) of the teeth tested showed no loss of pulp sensitivity to cold 30 days after surgery (P < 0.05), and at the end of the study, that figure had risen to 100% (263) of all teeth included in the sample. Conclusions: Pulp vitality testing showed that 31.18% (82) of teeth experienced some loss of sensitivity, but by 12 months after surgery, all teeth had recuperated their pulp sensitivity to cold unaided. (Implant Dentistry 2013;22:199-202)22219920

Segmental osteotomy with interpositional bone grafting in the posterior maxillary region

Tooth loss is followed by a natural bone resorption process that often leads to defects in the alveolar ridge, making the installation of dental implants unfeasible. Correction of such bone defects, especially loss of height of the ridge or associated loss of thickness, is a great challenge to dental surgeons. The technique of segmental osteotomy accompanied by interpositional bone grafting has been shown to be a viable option for addressing the problem. This report describes a successful application of the technique in the treatment of vertical dimension deficiency in the posterior maxillary region. Four months after graft surgery, 3 implants were successfully placed in accordance with the original reverse planning.41121563156

Evaluation of Patients' Perceptions of Alterations After Chin Bone Graft Harvesting

Objective: To evaluate patients' perceptions of alterations occurring after chin bone harvesting. Materials and Methods: Thirty patients were evaluated subjectively by visual analog scale-related sensitivity, facial aesthetics, eating, speaking, and lower lip movement, during 12 months. Objective analysis used the static light touch neurosensorial test. The statistical analysis was executed with Friedman test with P < 0.05 for both samples. Results: Subjective analysis revealed no alterations (1) to facial aesthetics, eating, speaking or lower lip movement but sensitivity of the mental region went from a lot of alteration initially (5) to little at the end of the study (3). Objective analysis results showed normal sensitivity (1) in the region after 12 months. Conclusion: The discrepancy between subjective and objective analyses may be indicative of the limited precision of clinical testing for subjective impressions assessment. (Implant Dent 2012;21:411-414)21541141

Radiographic prospective study of osseous repair in mandibular symphysis after chin bone remove

Bone harvest of mandibular symphysis has been used in maxillofacial reconstruction procedures. The aim of this research was to establish the presence of bone repair into osseous defect caused by removal of bone. Thirty patient s, 2 female and 8 male, ranging between 21 and 65 years of age underwent surgery for chin bone harvest and alveolar reconstruction. The surgery was performed by two maxillofacial surgeons and the patients were evaluated with lateral radiography in the pre-operatory stage, in early post-operatory and in late post-operatory stages. Horizontal and vertical measures of bone defect were realized; the dates were analyzed by Student t test with a value of p<0.05. After bone harvest, a vertical defect of 12.80 +/- 1.99 was observed and a horizontal defect of 8.33 +/- 1.77 was observed. After one year the defect decreased to 32.8% in vertical evaluation, and 50.3% in the horizontal evaluation with a statistical significance (p<0.05) in relation to the early post-operatory stage. Therefore, we conclude that in bone repair of mandibular symphysis defect is close to 30 - 50% in a one-year follow-up.30110010

Prospective Clinical Assessment of Morbidity After Chin Bone Harvest

The aim of this prospective research was to assess soft tissue morbidity in the symphyseal region after bone graft harvesting. Thirty patients, with average age 45 years, underwent symphyseal bone graft harvesting followed up for a period of 12 months. Follow-up involved neurosensory testing of 2-point discrimination, static light touch, brush directional stroke, pinprick, and thermal discrimination to cold and hot; the statistical analysis was performed using McNemar test and Friedman test with P < 0.05. The results showed that 50% of patients had postoperative morbidity in the first month after surgery showing statistical positive relation with surgery (P < 0.05); at 6 months, this situation diminished to 23%, and at the end of the monitoring period (1 year); the neurosensory tests revealed no persistent morbidity. In conclusion, all neurosensory tests revealed high morbidity in the first month with total resolutions at 1-year follow-up; however, this complication associated to surgery is indispensable to discharge the patient properly.2262195219