Atmospheric contamination during ultrasonic scaling.

OBJECTIVE: The aim of this study was to determine the microbial atmospheric contamination during initial periodontal treatment using a piezoelectric ultrasonic scaler in combination with either high-volume evacuation (HVE) or conventional dental suction (CDS). METHODS: The study included 17 treatment sessions, consisting of a 40-min episode of continuous plaque and calculus removal using an ultrasonic unit (EMS). The treatment sessions were carried out in six patients with generalized adult periodontitis and ranged from two to four sessions per patient according to their needs. The use of HVE and CDS was randomly assigned over the sessions within each patient. Before each treatment, the operating room was not used for 15 h. To measure baseline microbial air pollution two Petri dishes containing blood agar were exposed for 10 min to the air. At the start of each treatment session, two Petri dishes were exposed for 5 min at a distance of 40 cm from the mouth of the patients. After 20 min, this procedure was repeated. At a distance of 150 cm, two Petri dishes were exposed for 20 min followed by exposure of two new Petri dishes for the rest of the session. The plates were cultured aerobically and anaerobically for 3 and 7 days, respectively. RESULTS: The mean colony forming units (CFU) before treatment never exceeded 0.6 colonies per plate. At 40 cm, the mean CFU, when considering a period of 40 min, was 8.0 for HVE and 17.0 for CDS. The mean CFU at 150 cm during this period was 8.1 with HVE and 10.3 with the CDS. With reference to the Air Microbial Index the operatory atmosphere was considered to be in a good condition during 40 min of continuous use of the ultrasonic scaler in combination with both HVE and CDS. CONCLUSION: Within the restrictions of this study, only limited atmospheric microbial contamination is produced when using a piezoelectric ultrasonic scaler.

Can p53 alterations be used to predict tumour response to pre-operative chemo-radiotherapy in locally advanced rectal cancer?

PURPOSE: To examine whether p53 tumour suppressor gene alterations can be used to predict tumour response to pre-operative chemo-radiation in locally advanced rectal cancer in terms of reduction in tumour size and local failure. METHODS: p53 alterations were studied in pre-treatment biopsy specimens of rectal carcinomas from 48 patients by immunohistochemistry (IHC) and polymerase chain reaction/single strand conformation polymorphism (PCR-SSCP) gene mutation analysis. Pre-operative pelvic radiotherapy was delivered with four fields, 45 Gy to the ICRU point in 25 fractions over 5 weeks. A radio-sensitising dose of 5-fluorouracil (500 mg/m(2)) was delivered concurrently for 6 days of the 5-week schedule (days 1, 2, 3 and days 22, 23 and 24). Total meso-rectal excision was planned 4 to 6 weeks from completion of pre-operative treatment. Response to therapy was assessed by macroscopic measurement of the surgical specimen by a pathologist who was unaware of the pre-treatment tumour size or of the p53 status. RESULTS: IHC evidence of p53 protein accumulation was found in 40% of tumours, p53 gene mutation in 35% and p53 alteration (either or both changes) in 46%. The average reduction in tumour size was 53% in the group with 'wild-type' p53 (IHC-/SSCP-) and 63% in the group with altered p53 (either IHC+ or SSCP+; P=0.18). No significant differences in tumour size reduction or local failure were observed in the groups with p53 overexpression or p53 mutation compared with normal. CONCLUSIONS: p53 alteration detected by IHC or SSCP analysis is not a clinically useful predictor of local response to pre-operative adjuvant therapy in advanced rectal carcinoma.