Questionnaires were distributed to 55 Public Health and Defence Force dental clinics throughout Papua New Guinea in order to ascertain storage and clinical conditions, as well as information related to the type, consumption and performance of alginate and elastomeric impression materials and composite restorative materials. Of the 39 respondents, representing a 71% return, few reported any problems with either of the two types of impression materials. However, complaints associated with the use of paste-paste composites, Adaptic and Concise, were a major concern. It was assumed that the problems were caused by exposure to excessively high temperatures during shipment, distribution and storage of these materials throughout Papua New Guinea. Alternative materials, which are less sensitive to heat, were proposed for use in Papua New Guinea. These were a light-activated composite (Durafill), a powder-liquid composite (Powderlite) and a powder-water glass ionomer (Chemfil II).
Dental Clinics ; Dental Materials - supply & ; distribution ; Dental Restoration, Permanent - instrumentation ; Drug Storage ; Military Dentistry ; Papua New Guinea

OBJECTIVETo evaluate the effect of root canal taper and post on tooth stress distribution.

METHODSThree-dimensional finite element models of human mandibular first molar with root canals prepared with 35# K file, ProTaper and Profile were established. The tooth were restored with fiber-resin, stainless steel and silver amalgam posts respectively. A vertical load on tooth occlusal surface was simulated. Marc software was used to analyze and calculate the stress distributions in the tooth restored with three kinds of different root canal posts, especially the in the cervical part and root.

RESULTSDifferent tapered root canals had no obvious influence on stress distribution in all three different posts. Stress distribution of stainless steel post located at the cervical and middle part of distal root, the highest Von-Mises stress was about 45 MPa. Stress distribution of silver amalgam post located at the orifice of root canal and pulp fundus, the highest Von-Mises stress was about 16 MPa. Stress distribution of fiber-resin post had no obvious stress concentration.

CONCLUSIONSFiber-resin post is the most ideal root canal post. Stainless steel post causes remarkable stress concentration in the root, which may raise the possibility of root fracture.

Dental Amalgam ; chemistry ; Dental Pulp Cavity ; pathology ; Dental Restoration, Permanent ; Dental Stress Analysis ; methods ; Finite Element Analysis ; Humans ; Male ; Mineral Fibers ; Molar ; Post and Core Technique ; instrumentation ; Quartz ; chemistry ; Root Canal Preparation ; instrumentation ; Stainless Steel ; chemistry ; Stress, Mechanical ; Tooth Root ; physiology