ABSTRACT
Accurate impressions are one of the most critical factors in achieving acceptable restorations. When pouring the impressions of implant supported restorations, soft materials like silicone and polyether are used to reconstruct the gingival form around the implants. To the best of our knowledge, no study has been conducted on the comparison of the accuracy of these soft materials.To evaluate the accuracy of polyether and silicone in reproducing the correct depth of gingival sulcus around the implants by probing.By the use of a periodontal probe, the gingival height was measured in six marked areas of one maxillary partial edentullism model on which two fixture analogs were attached and three points were marked around each analog for measurements, which was considered as an index height. Addition silicone impression material [putty and wash] was used to simultaneously take 10 impressions of the model. The samples were randomly divided into two groups of 5 and each impressions was poured twice; for the first group, the impressions were first poured with silicone, and for the second one they were poured with polyether material for reproducing the gingival contour; in the second group, the procedure was performed in reverse. Therefore, there were 10 casts in each group and because each cast contained two analogues, and each analogue was marked in three points for measuring gingival height, 60 numbers were achieved for each group as the gingival height. The mean gingival heights were compared by paired t-test using SPSS software, version 18 [p = 0.05].Comparison of the mean gingival height of the silicone and control groups revealed that there was no significant difference between the two groups [p = 0.090], whereas, a significant difference was found between the mean gingival height of the polyether and control groups [p = 0.034].Within the limitation of this study, it was concluded that for reproducing the gingival height around the implants, silicone materials are more appropriate than polyether ones
ABSTRACT
Statement of Problem: Two potential problems commonly identified with a denture base incorporating a resilient liner are failure of the bond between acrylic resin and soft liner material, and loss of resiliency of the soft liner over time. Since patients may drink different beverages, it is important to evaluate their effects on physical properties of soft lining materials
Purpose: The objective of this in vitro study was to evaluate the effect of different beverages on the hardness of two temporary acrylic-based soft lining materials and their bond strength to the denture base resin
Materials and Method: For the hardness test; a total of 80 rectangular specimens [40mm×10mm×3mm] were fabricated from a heat-polymerized polymethylmethacrylate
Two commercially auto-polymerized acrylic resin-based resilient liners; Coe-Soft and Visco-gel were prepared according to the manufacturers' instructions and applied on the specimens. For the tensile test, 160 cylindrical specimens [30mm×10mm] were prepared
The liners were added between specimens with a thickness of 3 mm. The specimens of both soft liners were divided into 4 groups [n=10] and immersed in distilled water as the control group, Coca-Cola, 8% and 50% ethanol. All groups were stored in separate containers at 37oC for 12 days. All beverages were changed daily. The hardness was determined using a Shore A durometer and tensile bond strength was determined in a ZwickRoell testing machine at a cross-head speed of 5mm/min. The results were analyzed using two-way ANOVA
Results: There was no significant interaction between the soft liners and the drinks for both hardness [p= 0.748] and bond strength [p= 0.902]. There were statistically significant differences between all drinks for both hardness [p< 0.001] and bond strength [p< 0.05]
Conclusion: Within the limitations of this study, it seems that drinking Coca-Cola and alcoholic beverages would not be potentially causing any problems for the temporary acrylic soft liners
ABSTRACT
Statement of Problem: Orientation of the occlusal plan in complete denture prostheses therapies plays an important role, leading to appropriate esthetics, stability and mastication
Purpose: The aim of the present study was to define the best soft tissue index, by which the location and inclination of the occlusal plane in complete dentures could be established
Materials and Method: This cross-sectional study consisted of 200 individuals [76 male, 124 female], with the mean age of 26.05 [SD+/-4.39]. In order to determine the relationship between maxillary occlusal plane and ala-tragus line, fox plane and J plane were used. The relationships between maxillary occlusal plane and ALT1 [ala-superior border of tragus], ALT2 [ala-mid-tragus] and ALT3 [ala-inferior border of tragus] were evaluated. In the lower jaw, the occlusal plane was evaluated with the line between the upper and middle parts [ret1] and that between the middle and lower part of retromolar pad [ret2]. Data were analyzed by Chi-square test
Results: Evaluation of the difference between the number and percentage using Chi-square test [p < 0.05] showed that there were significant differences between ALT1, ALT2, ALT3 [ALT3 < ALT2
Conclusion: Superior one third of the tragus and the upper and middle one third of the retromolar pad are suggested as a reference points for determining the posterior part of the occlusal plane in comparison with the middle and lower one third of the tragus and middle and inferior one third of the retromolarpad
ABSTRACT
Infection control is an integral part of dentistry and dental impressions are considered an important issue in cross contamination. The aim of this study was to investigate the dimensional stability of two irreversible hydrocolloid materials, Alginoplast and Iralgin after disinfection with 5.2% sodium hypochlorite, used with immersion and spraying methods. In this experimental study, impressions were made of a master mandibular arch [Typodont] containing three stainless steel inserts on the occlucal surface of both mandibular first molars and in the lingual surface of the mandibular central incisors, which served as reference marks for making measurements. Two types of irreversible hydrocolloid [Iralgin and Alginoplast] were tested. 5.2% sodium hypochlorite was used in two methods of spraying and immersion to disinfect the samples. The control group was not disinfected. Casts were made of type III gypsum. Stone casts were measured with a Nikon profile projector.Kruskall-Wallis and Mann-Witney test were used for statistical analysis using p<0.05 as the limit of significance. Casts prepared from Alginoplast disinfected by spraying method, were 0.38% larger in anteroposterior and 0.06% smaller in cross arch dimensions, whereas those prepared from Alginoplast immersed in hypochlorite were 0.47% larger in anteroposterior and 0.11% smaller in cross arch dimensions. Casts made from Iralgin were smaller after both methods of disinfecting, [0.01% smaller in anteroposterior and 0.001% smaller in cross-arch dimensions after spraying and 0.04% smaller in anteroposterior and 0.03% smaller in cross-arch dimensions after immersing in sodium hypochlorite]. Alginoplast and Iralgin impressions can be immersed or sprayed for disinfection without compromising the accuracy needed for diagnostic and opposing casts, as well as removable partial denture construction