Perceptions of NZ orthodontists and periodontists on the management of gingival recession in orthodontic patients.

BACKGROUND: This study aimed to investigate the perceptions and opinions of orthodontists and periodontists on the management of gingival recession in orthodontic patients. METHODS: An online survey was sent to 29 periodontists and 80 orthodontists registered and currently practising in New Zealand. All participants answered questions about the timing and clinical indications of mucogingival surgeries in orthodontic patients diagnosed with mucogingival deformities. RESULTS: Most periodontists and orthodontists believed that gingival grafts should ideally be performed after orthodontic treatment. In clinical practice, 40% of periodontists indicated that they would receive referrals after completion of orthodontic treatment. However, 29.6% of orthodontists indicated that they would refer to a periodontist before orthodontic treatment in clinical practice. The most crucial factor that affected periodontists' decision-making was 'evidence-based guidelines' (35.0%), followed by 'clinical experience' (30.0%) and 'patient concerns' (15.0%). All four factors of 'gingival phenotype', 'presence of gingival recession', 'amount of keratinised tissue' and 'planning specific tooth movements' were equally considered by orthodontists regarding their decision-making. CONCLUSIONS: The majority of the surveyed New Zealand periodontists and orthodontists expressed a belief that the ideal timing for the management of gingival recessions would be after the completion of orthodontic treatment.

Transformation of chlorinated methanes by zero-valent aluminum coupled with Pd/Al2O3.

The transformation of chlorinated methanes by zero-valent aluminum under various pH conditions has been examined in the presence and absence of Pd/Al2O3. In the absence of Pd/Al2O3, carbon tetrachloride was primarily transferred to chloroform (65%) and dichloromethane (15.3%) at pH 2.5 while little of the hydrodehalogenation intermediates (approximately 5%) was found at pH 10.8. This indicates that carbon tetrachloride undergoes hydrodehalogenation at low pH but not at high pH. The low production of hydrodehalogenation intermediates at high pH could be attributed to the base-catalyzed hydrolysis of carbon tetrachloride resulting in the formation of products that can not be detected by the provided analytic methods. In the presence of Pd/Al2O3, degradation rates were increased by a factor of 10-43 compared to the system without Pd/Al2O3, suggesting Pd/Al2O3, serves as a catalyst. Further, complete degradation of carbon tetrachloride by zero-valent aluminum with Pd/Al2O3 led directly to methane (86.4%) without formation and accumulation of dichloromethane at pH 9.0. The direct transformation of carbon tetrachloride to methane can be rationalized by the catalytic hydrodehalogenation occurring at the palladium surface. The study indicates aluminum coupled with Pd/Al2O3 is an environmentally-friendly technology for treatment of chlorinated organic contaminants.

Assessment of dose and risk to the body following conventional and spiral computed tomography.

BACKGROUND: Computed tomography (CT) is one of the most frequently used examination procedures in diagnostic radiology and the dose given to the patients is higher than in general radiographic procedures. In this study LiF chip thermoluminescent dosimeters (TLD-100) were placed in each relative organ or tissue position, including head, chest and abdomen, in a Rando phantom. CT was performed using both conventional and spiral modes, and effective dose and effective dose equivalent were assessed for each organ or tissue scanned. METHODS: The TLD reader used in this experiment was controlled at a nitrogen flow rate of 450 ml/min, preheat time of 14 seconds, reading time of 16 seconds and annealing time of 16 seconds. This CT scanner can be used to perform both conventional and spiral tomography. Operating conditions for spiral tomography were 120 kV, 80 mA for scout film, and 120 kV, 200 mA, 1 sec/slice for each scanning. However, for conventional tomography, the operating conditions were 120 kV, 80 mA for scout film and 120 kV, 160 mA, 1.5 sec/slice for each scanning. These operating conditions are satisfactory to most clinical applications, and therefore were adopted for the present studies. RESULTS: Results showed that, in both effective dose and effective dose and effective dose equivalent, conventional tomography was higher than spiral tomography. The average effective doses for each part were measured to be 1.89 and 4.95 mSv for the head, 30.01 and 40.65 mSv for the chest, and 12.85 and 19.62 mSv for the abdomen of spiral and conventional CT, respectively. Higher carcinogenic risk was assessed in organs such as liver, lung, stomach and bone marrow, other organs had a relatively lower incidence of risk. CONCLUSIONS: The main purpose of this study was to obtain distribution values of effective dose and effective dose equivalent, and to know the probability of carcinogenic effect upon each organ or tissue after CT scanning. Results showed the average effective dose for spiral CT to be less than conventional CT, and the dose in the body surface was generally lower than the dose in the central region.