Peri-implant strain around mesially inclined two-implant-retained mandibular overdentures with Locator attachments

Abstract

This study aimed to evaluate the periimplant strain around mesially inclined implants used to retain mandibular overdentures with Locator resilient attachments. Four mandibular edentulous acrylic resin models received two implants in the canine areas with 0°, 5°, 10°, and 20° mesial inclinations. Overdentures were connected to the implants using Locator attachments. Pink nylon inserts (light retention) were used for all implant inclinations, and red inserts were used for 20° inclination (20°red). Four strain gages were bonded on the mesial (M), distal (D), buccal (B), and lingual (L) surfaces of each implant. Peri-implant strains were measured during bilateral and unilateral loading. The 20° inclination showed the highest strain, followed by 10° and 5°, and both 0° and 20°red presented with the lowest strain. Site D was associated with the highest strain, followed by M, B, and L, which showed the lowest strain values. Unilateral loading and the loading side presented with significantly higher strain values than bilateral loading and the nonloading side, respectively. Hence, in this study, strains around the two-implant-retained overdentures with Locator attachments increased with increases in mesial implant angulation, except when red male inserts were used.

Effect of Implant Position on Clinical and Radiographic Outcomes of Locator‐Retained Mandibular Overdentures: A 1‐Year Prospective Study

“…Therefore, blue inserts (extra-light retention) were used in both groups (for standardization) to decrease periimplant stresses resulting from increased implant angulation, as these inserts were reported to be associated with reduced periimplant stresses compared to pink (light retention) and clear (medium retention) inserts. 9,[41][42][43] Overall, the null hypothesis was rejected. From the results of this study, both canine and premolar implants could be used successfully to retain mandibular overdentures with Locator attachments; however, canine implants may present a clinical advantage in terms of peri-implant bone preservation.…”

“…39 Also the increased marginal bone loss in the PM group may be attributed to the fact that the majority of implants inserted in premolar areas are inclined lingually due to mandibular resorption, bone concavities, and undercuts present in the lingual side of the mandible in this area. 40 This implant angulation significantly increases peri-implant stresses, especially with Locator attachments 9,41,42 and may be responsible for increased periimplant bone loss. Therefore, blue inserts (extra-light retention) were used in both groups (for standardization) to decrease periimplant stresses resulting from increased implant angulation, as these inserts were reported to be associated with reduced periimplant stresses compared to pink (light retention) and clear (medium retention) inserts.…”

Effect of Distal Implant Inclination on Dislodging Forces of Different Locator Attachments Used for Mandibular Overdentures: An In Vitro Study

“…These inserts were used for 20°implant inclination only. For each implant inclination (model), five specimens for each type of insert were used based on the recommendations of other studies [16][17][18]22 for sufficient power in the results. No power analysis was performed.…”

“…Although Lm may increase retention values, it may cause destructive forces to the inclined implants when Locator attachments are used. [16][17][18] Geckili et al 39 concluded that higher retention force of an implant-retained overdenture provides better quality of life, but does not affect patient satisfaction. Therefore, clinicians should avoid the use of strong retentive elements (Lm) when implants present a distal inclination, and use light retentive elements (Le and Lee) instead to minimize destructive forces on the implants when Locator attachments are used.…”

“…14 Stability is the resistance to horizontal and rotational forces that prevent lateral or anterior-posterior shunting of the denture base. 15 Implant angulation significantly affects peri-implant strain, [16][17][18] retention, [19][20][21] and prosthetic maintenance 8,13,19,22 of Locator attachments. The effect of different degrees of distal 8,20,23 and mesial 19,24 inclinations of two implants on the retention of Locator attachments have been investigated in several studies; however, these studies did not evaluate and compare the retention of all types of patrix nylon inserts (the conventional and extended range inserts) when used for angulated implants.…”