influence of inclined implants and attachments on the retention and longevity of implant-retained overdentures: an in vitro study

Statement of Problem: Several dilemmas have been reported with regard to the retention and longevity of implant-retained overdentures. A few studies have investigated the influence of implant and attachment inclination on the path of insertion and withdrawal of the prosthesis and on the retention and longevity of the overdenture. However, no study has been reported with regard to the influence of labio-lingual inclination on the aforementioned indices

Purpose: The purpose of this study was to investigate the influence of implants and attachments with 5 and 10 degrees of inclination on the retention and longevity of implant-retained overdentures

Materials and Method: In this experimental study, 10 implants and 50 attachments were selected and divided into five groups: Group I: two implants and attachments parallel to each other; Group II: implants inclined at an angle of 5 degrees and attachments without any inclination; Group III: implants and attachments inclined at an angle of 5 degrees; Group IV: implants inclined at an angle of 10 degrees and attachments without any inclination; Group V: implants and attachments inclined at an angle of 10 degrees. All the attachments and implants were lubricated by artificial saliva. Initial retention [N] of blocks was measured through the Universal Testing Machine [SANTAM, STM-20]. The blocks were removed and replaced for 3000 cycles and retention was measured after each 500 cycles. The retention was measured five times for each group and the registered data were analyzed by One-way ANOVA and T-test

Results: The maximum and minimum amounts of initial retention were 5.54 +/- 0.3 and 3.88 +/- 0.19 and were related to groups III and I, respectively. There was no significant difference among groups II, III, IV, and V with regard to the amount of retention of implants and attachments [p < 0.3]. However, there was a significant difference between the control group, group I, and the other groups [p <0.01]

Conclusion: Although the placement of labially inclined implants results in an increase in the initial retention, it will lead to a large decrease in the amount of retention after the last cycle. However, this amount of inclination [5 or 10 degrees] does not have any negative effect on the prosthesis longevity

[Evaluation of the accuracy of three common methods in determining hinge axis points]

Determining the true hinge axis point in order to transfer the orientation relation to articulator is of great importance in reducing occlusal errors. Because of the high cost and time consuming nature of kinematic method in determining hinge axis point, different arbitrary methods have been introduced which rendered controversial results throughout literature. The aim of this study was to evaluate some arbitrary methods for determining hinge axis point and to introduce a precise arbitrary method which has the least distance from kinematic point. This cross-sectional study was performed sequentially on 40 subjects without any TM-disorders with an age range of 21-37. At first true hinge axis point was determined by DENAR hinge axis locator and marked bilateraly on the skin. Then 3 arbitrary points [Beyron, Gysi, Tetruck and Laundeen] was also determined by a flexible ruler and marked on the skin. The distance between the arbitrary points and kinematic point was measured and the data were charted and subjected to Repeated ANOVA and Paired sample test. According to the results of the study, Beyron method was significantly more accurate than the other two methods. 88.88% of Beyron points were within 3 mm distance from kinematic point, but the other points didn't show any significant difference with each other. It is concluded that Beyron method has a high accuracy as an arbitrary method and because of its proximity to the true point, application of this method is recommended

evaluation of occlusal contacts of remounted complete denture before final occlusal adjustment

There are various studies about the advantages and effect of remounting procedures on success of complete dentures; however, the number and distribution of occlusal contacts of remounted complete dentures before occlusal adjustment have not been sufficiently assessed. The purpose of this study was to evaluate the distribution and number of occlusal contacts of remounted complete dentures in centric relation before occlusal adjustment. In this cross-sectional study, 207 newly constructed complete dentures were remounted on a modified two dimensional articulators. For identification of occlusal contacts, a 60 micron articulating paper was used to mark the actual contacts of the opposing teeth. The articulating paper was interposed between the teeth, and contacts were obtained by holding the articulating paper between the opposing teeth. The number and distribution of the occlusal contacts on each complete denture in centric relation were recorded and analyzed, using descriptive statistics. Out of the 207 studied complete dentures, 203 had occlusal contacts. Among 203 complete dentures, 138 [68%] and 65 [32%] had bilateral and unilateral occlusal contacts, respectively. The total number of occlusal contacts was 713 with a range of 1-14. The mean number of occlusal contacts was 3.44 +/- 2.29. The results suggest that the number of occlusal contacts of remounted complete dentures before occlusal adjustments by articulating paper was low, the posterior teeth did not meet evenly all around the arch at the first contact, and delivery of such complete dentures may lead to occlusal error and unstable complete denture

[Prevalence of epulis fissuratum and its associated factors in dependent elderlies, Tehran 2005]

According to relatively high prevalence of epulis fissuratum in patients having compete denture, with its known consequences and predicaments; also, the controversy and lack of information about the prevalence of epulis fissuratum especially in Iranian dependent elderly, the aim of this study was to determine the prevalence of epulis fissuratum and its associated actors, in two senatorium of Tehran [Kahrizak, and Pasdaran] in 1384. This cross- sectional study was done on 201 dependent elderlies having complete dentures. Clinical examinations were done to diagnose and record the epulis fissuratum which is a sessile pedanculated inflammatory fibrous hyperplastic lesion under base of the denture. Associated factors such as sex, age, site of living, retention, and stability of denture, satisfaction of denture esthetic, complete denture maker, and complete denture wearing period were studied. The prevalence of epulis fissuratum was determined and the associated factors were statistically analysed by Chi-square test. The prevalence of epulis fissuratum was 16.4%. There was significant relation among the prevalence of epulis fissuratum with sex, stability, retention of complete denture and period of wearing complete denture on 24 hours [P<0.05]. Other studied factors didnt have any significant relation with incidence of epulis fissuratum. The prevalence of epulis fissuratum was noticeable. With regard to probable dysplastic and precancerous changes in this lesion cohort and clinical studies are recommended