A comparison of preload values in gold and titanium dental implant retaining screws.

This in vitro investigation compared the effect of using either gold or titanium retaining screws on preload in the dental implant- abutment complex. Inadequate preload can result in screw loosening, whilst fracture may occur if preload is excessive. These are the most commonly reported complications in implant-retained prostheses, and result in unscheduled, costly and time-consuming visits for the patient and the clinician. This study investigated changes in preload generation after repeated torque applications to gold and titanium screws. The test set-up consisted of an implant body, a cylindrical transmucosa abutment, and the test samples of gold and of titanium retaining screws. The implant bodies were anchored using a load cell, and the transmucosal abutments were attached using either gold or titanium retaining screws. A torque gauge was used to apply torque of 20Ncm, 32Ncm, and 40Ncm to the retaining screws. The preloads generated in each screw type were compared at each torque setting, and after repeated tightening episodes. In addition, the effect of applying torque beyond the manufacturers' recommendations was also examined. Gold retaining screws were found to achieve consistently higher preload values than titanium retaining screws. Preload values were not significantly different from the first to the tenth torque cycle. Titanium screws showed more consistent preload values, albeit lower than those of the gold screws. However due to possible galling of the internal thread of the implant body by titanium screws, gold screws remain the retaining screw of choice. Based on the findings of this study, gold retaining screws generate better preload than titanium. Torque beyond the manufacturers' recommendations resulted in a more stable implant complex. However, further investigations, with torque applications repeated until screw breakage, are needed to advise on ideal maintenance protocols.

A clinical evaluation of children under the age of five years who are household contacts of adults with sputum positive tuberculosis in Harare, Zimbabwe.

OBJECTIVE: To determine the prevalence and risk factors for transmission of tuberculosis in children under five years of age who are household contact of sputum smear positive tuberculosis adults in Harare, Zimbabwe. DESIGN: Cross sectional study. SETTING: City Health Infectious Diseases Hospital Outpatient Department. SUBJECTS: 174 children in contact with 102 index cases. MAIN OUTCOME MEASURES: TB infection status in children according to modified WHO classification of tuberculosis. METHODS: Under five year old contacts of sputum smear positive TB adults were recruited over a three month period. A coded questionnaire was used to document the following: socio-demographic profile of caregivers, duration of stay with the index case and presenting complaints. Contacts were evaluated by clinical examination, Mantoux testing, HIV antibody testing and chest radiographs. RESULTS: Of the 174 children in contact with 102 index cases evaluated, 109 (62.6%) were Mantoux positive (> or = 10 mm), 42% had abnormal chest X-ray, with hilar lymphadenopathy being the commonest abnormality. Forty nine percent of the children evaluated had probable TB, 28% had suspected TB and 23% had no TB. High alcohol acid fast load (AAFB) in the index case was independently associated with probable and suspected TB (OR 2.27 95% CI (1.05 to 4.87). CONCLUSION: The documented high transmission rate among under five years contacts in the study justifies the need for strengthening contact tracing and appropriate therapeutic management of identified children.