Effect of Interimplant Distance and Cyclic Loading on the Retention of Overdenture Attachments

The Effect of Mini Dental Implant Number on Mandibular Overdenture Retention and Attachment Wear

Purpose

Evaluate the effect of different mini-implant numbers on overdenture retention and evaluate attachment wear following one year of simulated placement/removal. Material and Methods. Nine models simulating atrophic mandibles held 27 mini dental implants in three groups of 2, 3, and 4 mini-implants. A total of 1080 simulated placement/removal cycles were carried out, and a digital force gauge was used to measure the overdenture dislodgment force. The means of the retention forces were analyzed using SPSS with one-way ANOVA and post hoc (p < 0.05). The inner diameter of attachment inserts was evaluated using a light microscope before and after testing. A paired t-test was used to compare the mean of inner ring diameters (p < 0.05).

Results

The retention was significantly reduced regardless of the mini dental implant number, but the number affected overdenture retention. The placement of 4 mini dental implants provided higher retention and less reduction in retentiveness. However, no significant difference was found when 3 mini dental implants were compared to 2 mini dental implants (p = 0.21). Microscopic examination showed abrasion wear in all inserts following testing. However, the inserts of the 4 mini dental implants showed less wear than those used for 2 or 3 mini dental implants with p ≤ 0.001 and p ≤ 0.001, respectively.

Conclusion

Mini dental implant overdenture retention force and attachment wear could improve by increasing the mini dental implants to 4. However, there was no difference in retention force or attachment wear when 2 or 3 mini dental implant overdentures were compared.

Effects of interimplant distance and cyclic dislodgement on retention of LOCATOR and ball attachments: An in vitro study

STATEMENT OF PROBLEM

Evaluation of the long-term retentive behavior of overdenture attachments is necessary for successful treatment. Interimplant distance (IID) could affect the retention of these attachments.

PURPOSE

The purpose of this in vitro study was to assess the effects of IID and cyclic dislodgement on the retention of LOCATOR and ball attachments.

MATERIAL AND METHODS

Ball and LOCATOR attachments were connected to corresponding implant analogs. Metal housings were connected to each attachment. Thirty-six pairs of acrylic resin blocks were fabricated for 3 IIDs (19, 23, and 29 mm) and 2 attachments (n=6). Each pair consisted of 2 attachment assemblies parallel to each other with a specified IID. Overall, 1440 dislodgement cycles were applied by using a universal testing machine, and the maximum dislodging force was recorded after 0, 120, 360, 720, and 1440 cycles. Dislodging force data were analyzed by using repeated-measures 3-way analysis of variance, with the number of cycles as the within-subject factor for each specimen. Bonferroni-corrected Student t tests were used to resolve effects that were statistically significant. Moreover, dislodging force data were fit into an exponential decay model to determine the extent and rate of force decay for each attachment and IID studied.

RESULTS

The initial retention of LOCATOR attachments was significantly higher than that of ball attachments with IIDs of 23 and 29 mm, but no significant difference was noted with the 19-mm IID. After 1440 cycles, the retention was statistically similar with that of the 23-mm IID but was significantly higher for ball attachments with IIDs of 19 and 29 mm.

CONCLUSIONS

The IID is one of the factors that affect the retention of ball and LOCATOR attachments. The mean retention of both attachments was sufficient for all 3 IIDs at insertion and after 1440 cycles.

Effect of Implant Location on Palateless Complete Overdenture Retention: an In Vitro Study

Objectives

The purpose of this in vitro study was to evaluate effect of implant location on initial retention values of palateless complete overdentures retained by four o-rings at different inter-implant distances.

Material and Methods

Two standard acrylic models representing completely edentulous maxillary arches were used. Four single piece ball type implants were placed in each model. Models were divided into two groups according to the distance between anterior and posterior implants. Two canine implants with 32 mm inter-implant distance were placed in both models. In one model (G1), two posterior implants were placed in second premolar region away from canine implants by 14 mm on both sides, while in the other model (G2), the two posterior implants were placed in first molar region away from canine implants by 22 mm on both sides. Eighteen palateless complete overdentures were constructed for each model. Overdentures were retained by four o-rings. Initial axial (central), and para-axial (anterior, posterior, and lateral) retention values of overdentures were estimated and compared using a universal testing machine.

Results

Independent t-test revealed that implant location has a significant role in palateless complete overdenture retention with a level of significance set at P < 0.05.

Conclusions

For in vitro simulated palateless implant overdentures retained by four o-rings, increasing the inter-implant distance between anterior and posterior implants is favourable for a more retentive prosthesis.