Strains around distally inclined implants retaining mandibular overdentures with Locator attachments: anin vitrostudy

Abstract

PURPOSEThe aim of the present study was to evaluate, by means of strain gauge analysis, the effect of different implant angulations on strains around two implants retaining mandibular overdenture with Locator attachments.MATERIALS AND METHODSFour duplicate mandibular acrylic models were constructed. Two implants were inserted in the canine regions using the following degrees of distal inclinations: group I (control); 0°, group II; 10°, group III; 20°, and group IV; 30°. Locator pink attachments were used to connect the overdenture to the implants and Locator red (designed for severely angled implants) was used for group IV (group IVred). For each group, two linear strain gauges were attached at the mesial and distal surfaces of the acrylic resin around each implant. Peri-implant strain was measured on loading and non-loading sides during bilateral and unilateral loading.RESULTSFor all groups, the mesial surfaces of the implants at loading and non-loading sides experienced compressive (negative) strains, while the distal implant surfaces showed tensile (positive) strains. Group IV showed the highest strain, followed by group III, group II. Both group I and group IVred showed the lowest strain. The strain gauges at the mesial surface of the loading side recorded the highest strain, and the distal surface at non-loading side showed the lowest strain. Unilateral loading recorded significantly higher strain than bilateral loading.CONCLUSIONPeri-implant strains around two implants used to retain mandibular overdentures with Locator attachments increase as distal implant inclination increases, except when red nylon inserts were used.

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

“…Using a parallometer milling machine (TDS cutter, Turbodent system, Jabil Green, Taichung, Taiwan), two recesses were prepared in the marked sites in the canine areas (17). The models were classified into the following four groups on the basis of the degree of mesial implant inclination: 0°, 5°, 10°, and 20° (Fig.…”

“…The implants were fixed to the acrylic models using a resin cement to simulate osseointegration (30). For each model, an approximately 1.5-mm layer of silicone soft liner (GC Reline Extra soft, GC Corp., Tokyo, Japan) was used to simulate the alveolar mucosa (6,17,29,31,32).…”

“…They also transmit increased stress to the bone compared with vertically placed implants (16,17). The increased stress may cause bone resorption and microdamage (18,19).…”

“…However, data regarding peri-implant strain around two-inclined implant-retained overdentures remain scarce (17,(26)(27)(28). In a finite element study, Hong et al (26) found higher strains and less equal stress distribution in peri-implant bones for all inclined implants compared with those in parallel implant-retained overdentures with ball anchors.…”

“…Most studies evaluating the stress around the inclined implant-retained overdentures are concerned with distal inclination (17,(26)(27)(28). However, the effect of mesial implant inclination on strain transmitted by Locatorretained overdentures has not been investigated.…”