Objectives: To investigate opinions on, and current use of lining materials prior to the placement of posterior resin composite restorations by general dental practitioners (GDPs) in the UK. A further objective was to investigate aspects of posterior resin composite restoration placement techniques employed by UK GDPs. Methods:A questionnaire was devised to gain the information sought. It was sent to 500 UK dentists, chosen at random from the register of the General Dental Council.Results: Three hundred and fifty four replies were received, which gave a response rate of 71%. Eighty two percent of respondents reported placing lining materials in deep cavities to be restored with resin composite. Regarding moderately deep cavities, half of the respondents indicated a preference to place a lining material, whilst 44%were not sure if a lining was required. The remaining 6% did not respond to the question. Of the respondents, 39% reported that they did not place lining materials in shallow cavities. Regarding techniques for posterior resin composite placement, twostep etch and rinse systems were the most common adhesive bonding systems used (60%). The majority of respondents (80%) reported not using rubber dam when restoring posterior teeth with resin composite. contentious among dentists, resulting in a need to generate more convincing, practice- Conclusions

TX 75083-3836, U.S.A., fax +1-972-952-9435. AbstractIn certain cases, multiple production casing sizes are used across formations of the same pressure regime especially in vertical or slightly deviated wells with long pay sections. The normal perforation practice would be to use a smaller gun size to perforate the smaller lower casing section before making another perforating run with bigger gun size to perforate the upper casing. Such perforating technique not only adds cost and time to the completion program but also reduces the efficiency of the perforation tunnels due to damage caused by the completion fluids in the wellbore between the two perforation runs. In addition, underbalanced perforation can only be performed on the first perforating run. Isolation of the first zone would be required to create under-balance for the second run, thus adding cost and complexity to the operations. Furthermore, multiple perforation runs in a well tends to damage the existing perforations due to pressure surges created in the subsequent runs. These pressure surges generally pack wellbore solids into the existing perforation tunnels.This paper describes in greater details the innovative technique of perforating with multiple gun sizes across multiple casing sizes in a single run. It discusses the engineering design and considerations involved which allows the application of this new technique safely without imposing additional risks to the perforating operation. This technique provides the operators with a viable option that is more economical and efficient compared to conventional practices of perforating across different sizes of casing using multiple runs.The key areas of concern when designing the perforating technique with two guns sizes are the combined detonation pressures and the shock waves effects from both gun sizes on the perforation string. Both of these factors were carefully calculated for the specific environment in which the guns to be run. From these engineering calculations, a suitable gun string can be design to stand the explosive effect resulted during perforation. Based on the detonation pressure, suitable gun adaptor is designed using appropriate alloy to stand the ballistic effect during the perforation. This gun adaptor allows instantaneous ballistic transfer between the two gun sizes. The use of reactive liner perforating shaped charges also reduces the damage on the perforation tunnels as well as eliminating the limitation due to wellbore and reservoir conditions. This innovative perforating technique of running multiple gun sizes in a single run was applied successfully in a gas well in Pakistan. The pay zone was completed with 7 in. liner and 5 in. liner. The operator was initially considering either to perforate the well using wireline conveyed perforation or using shoot and pull technique with tubing conveyed perforation with one gun sizes at a time. However, both methods involve long and costly operations. Considering all the above challenges, the new perforating technique was recommended. T...