Background: The fabrication of dental prosthesis requires the transfer of interocclusal records from patient's mouth to semiadjustable articulators using different kinds of recording media. Any inaccuracy in these interocclusal records leads to occlusal errors in the final prosthesis. This study was conducted to evaluate the dimensional changes occurring in the interocclusal recording material over a given period of time and the material's resistance to compression during the cast mounting on the articulator. Methods: In this in vitro study, the linear dimensional change and compressive resistance of four commercially available elastomeric interocclusal recording media was tested. Three were addition silicones and the fourth was a polyether material. Cylindrical samples of 10mm diameter of each material were prepared in three different thicknesses of 2, 4 and 6mm. Ten samples each of thickness of 2, 4 and 6mm for all four materials were prepared (total of 120 samples). The linear dimensional changes of the samples were evaluated after 24 hours of fabrication. The compressive resistance was measured when each of these was subjected to a constant compressive load of 25 Newtons. Results: The mean linear dimensional change in a horizontal plane was minimum for Kanibite Hard, an addition silicone. Ramitec showed the maximum linear dimensional change. The mean compression distance was least for Futar D Occlusion (an addition silicone) and maximum for Ramitec (a polyether). It was observed that the samples of thickness 2mm for all the materials underwent least compression. Conclusion: The compressive resistance of each elastomer was inversely proportional to the thickness of the sample. This implies that minimum thickness of the recording materials should be used for recording maxillomandibular relations without sacrificing the strength of the interocclusal record. MJAFI 2007; 63 : 237-240

Introduction: Infection control is an important concept in the present day practice of dentistry. Elastomeric dental impressions too should be disinfected as per laid down protocols. Recently, vinylsiloxaether type of elastomeric impression material have been introduced which is supposed to have improved hydrophilic properties among others. This invitro study was taken up to compare wettability of vinylsiloxaether impression material in comparison to two other popular traditional elastomeric impression materials i.e polyether and addition silicone. Materials and Methods: An in-vitro study was undertaken to evaluate effect of four recommended commercially available disinfectant solutions on the wettability of three types of elastomeric impression materials at 10 and 30 minutes time intervals. The impression materials evaluated were vinylsiloxaether, addition silicone and polyether. The disinfectants used were 2% glutaraldehyde, 0.5% sodium hypochlorite, 0.05% iodophor and 0.25% benzalkonium chloride. 100 samples of each impression material was made and subjected to 10 different immersion protocols including distill water as control. The surface wettability (contact angle) of all samples was measured using the contact angle analyzer (Digidrop, Contact angle meter, GBX products, France). The data obtained was statistically analyzed. 'Two-sample t-tests', 'twoway-ANOVA' and 'tukey simultaneous test' was applied. Results: The mean contact angle values of addition silicone samples were highest among elastomers followed by polyether and vinylsiloxaether samples. The mean value of contact angles for 30 minutes immersion time interval was highly significant compared to the corresponding values of 10 minutes immersion time interval (P< 0.0001). In each case, the mean contact angles were higher for 30 minutes immersion time interval. Conclusion: Among the elastomeric impression materials evaluated, wettability wise vinylsiloxaether proved to be the best impression material followed by polyether and addition silicone. Disinfection with 2% glutaraldehyde had shown lowest contact angle values followed by 0.5% sodium hypochlorite solution, 0.25% benzalkonium chloride and 0.05% iodophor respectively.

Dimensional stability of commonly used interocclusal records is a significant factor for precise articulation of patient's diagnostic and working casts in the fabrication of well fitting prosthesis with satisfactory occlusion. The aim of this study was to measure the dimensional accuracy of modeli g wax, aluwax, addition silicone and modeling wax corrected with zinc oxide eugenol. Total of 80 samples were fabricated. The dimensional accuracy of these materials was tested in three planes i.e. anteroposteriorly, mediolaterally and vertically. The dimensional accuracy in horizontal plane was measured with travelling micro cope and in vertical plane with digital vernier caliper. The values obtained were stati tically analysed y A OVA and Tukey HSD-Honestly significa t difference. olyvi ylsiloxane was observed to be the most dimensionally accurate material and modeli g wax, the least accurate material of all the materials tested.