The Influence of Implant Inclination on Retention and Peri-implant Stresses of Stud-Retained Implant Overdentures During Axial and Nonaxial Dislodgments: An In Vitro Study.

PURPOSE: The purpose of this study was to evaluate the influence of implant inclination on retention and peri-implant stresses of stud-retained implant overdentures during axial and nonaxial dislodgments. MATERIALS AND METHODS: Mandibular acrylic models (n = 4) received two implants in the canine areas with 0-, 5-, 10-, and 20-degree lingual inclinations. Dentures were attached to the implants with stud connectors. Four strain gauges were bonded at buccal, lingual, mesial, and distal surfaces of each implant to monitor strains around implants. Retention values (Newton) and peri-implant stresses (microstrains, µs) were recorded during axial (vertical) and nonaxial (anterior, posterior, and lateral) dislodging. A general linear model was used to compare retention forces and implant stresses between implant inclinations and dislodging direction. In addition, a linear regression model was used to test correlation of implant stresses with confounding factors. RESULTS: The highest retention and implant stresses were noted with 0 degrees, followed by 5 and 10 degrees (without difference), and the lowest values were noted with 20 degrees. Anterior dislodging was associated with the highest retention and implant stresses, followed by vertical dislodging, then lateral dislodging, and posterior dislodging. Peri-implant stresses significantly correlated with dislodging direction and retention forces. Every 1 N of increase in retention forces causes 19.17 µs increase in implant stresses. Anterior dislodging was associated with the highest predicted stress values (846.0 µs), and the lowest stress values (143.41 µs) were associated with posterior dislodging. CONCLUSION: Retention forces and peri-implant stresses decreased as lingual implant inclination increased during axial and nonaxial dislodging of stud-retained implant overdentures. Peri-implant stresses were significantly correlated with dislodging direction and retentive forces.

Effect of Different Degrees of Mesial Implant Inclination on the Retention and Stability of Two-Implant Mandibular Overdentures Retained with Stud Attachments: An In Vitro Study.

PURPOSE: To evaluate the effect of different degrees of mesial implant inclinations on the retention and stability of two-implant mandibular overdentures retained with stud attachments. MATERIALS AND METHODS: Four experimental mandibular acrylic models were constructed. Two laboratory implants were inserted in the canine areas of each model with the following degrees of mesial inclinations: 0, 5, 10, and 20 degrees. Experimental overdentures were connected to the implants with Locator extra-light retention (Le), Locator light retention (Ll), and Locator medium retention (Lm). Vertical (retention) and oblique (stability) dislodging forces (anterior, posterior, and lateral) were measured at the beginning of the study (initial retention) and after 540 cycles of denture insertion and removal (final retention). RESULTS: The final retention was not significantly affected by small (5 degrees) and large (20 degrees) implant inclinations, but decreased with a moderate (10 degrees) inclination. For a small implant inclination (5 degrees), Lm showed the highest final retention/stability and Le showed the lowest, while for moderate and large inclinations (10 and 20 degrees), Le showed the highest final retention/stability and Lm showed the lowest. Vertical dislodging recorded the highest final stability, and lateral dislodgment recorded the lowest stability. CONCLUSION: Within the limitations of this in vitro study, only moderate implant angulation (10 degrees) negatively affects the final retention and stability of Locator-retained overdentures. Locator medium retention for small angulation (5 degrees) and Locator extra-light retention for moderate (10 degrees) and large (20 degrees) angulations are recommended to maintain high retention and stability after 540 cycles of denture insertion and removal.

Masticatory function with ball and resilient telescopic anchors of mandibular implant-retained overdentures: A crossover study.

OBJECTIVE: The masticatory function of implant-retained overdentures with different attachments has not been sufficiently investigated. This study evaluated the masticatory function of implant-retained mandibular overdentures with ball and resilient telescopic attachments. METHOD AND MATERIALS: Twelve edentulous participants were rehabilitated with new maxillary and mandibular conventional dentures (CD). Three months later, two implants were installed in the canine regions of the mandible. Following a 3-month healing period, duplicate overdentures were constructed for all patients. In a simple random method, six participants were first given ball-retained overdentures (BOD) and the other six received resilient telescopic-retained overdentures (TOD). After testing these prostheses, the first group received the TOD, while the second group received the BOD. Masticatory functions (chewing efficiency [unmixed fraction, UF] and electromyographic activity [EMG] of masseter muscles) were measured 3 months after wearing each of the following dentures: CD, BOD, and TOD. UF was measured using chewing gum and EMG was recorded for right and left bellies of masseter muscle during clenching with (soft and tough) and without foods. RESULTS: Regardless of attachment type, implant-retained overdentures demonstrated significant decrease in UF and significant increase in EMG compared to CD. TOD recorded significantly lower UF and significantly higher EMG when compared to BOD. CONCLUSION: The TOD improves masticatory functions when compared to BOD. Such improvement may be related to the increased retention and stability of these dentures.

Posterior Mandibular Ridge Resorption Associated with Different Retentive Systems for Overdentures: A 7-Year Retrospective Preliminary Study.

PURPOSE: This retrospective study compared posterior mandibular residual ridge resorption with two different retentive mechanisms for overdentures after 7 years. MATERIALS AND METHODS: A convenience sample of 18 edentulous men was assigned to one of two equal groups. Two implants were placed in the mandibular canine areas for each patient using the conventional two-stage surgical protocol, and the implants were splinted with a round bar 3 months later. New mandibular overdentures were then connected to the bars with clips (clip-retained overdentures, CR group) or resilient liners (resilient liner-retained overdentures, RR group). Posterior mandibular ridge resorption (PMRR) was recorded using proportional measurements and posterior area index (PAI) on panoramic radiographs taken immediately after overdenture insertion (T0) and 7 years later (T7). A linear regression model was used to verify the relationship between PAI and the following considerations: attachment type, age, initial mandibular ridge height, period of mandibular edentulism, number of previously worn dentures, and relining events. RESULTS: After 7 years, the RR group demonstrated a significantly (P = .014) higher change in PAI (0.11 ± 0.02) than the CR group (0.06 ± 0.04). The average PMRR for each mm of posterior mandibular ridge was 0.79 mm (0.11 mm/year) in the CR group and 1.4 mm (0.2 mm/year) in the RR group. Attachment type, initial mandibular ridge height, and relining times were significantly correlated with change in the PAI (P = .004, P = .035, and P = .045, respectively). CONCLUSION: Within the limitations of this preliminary study's design, it was observed that following a 7-year period of use, resilient liner attachments for bar/implant-retained overdentures appear to be associated with greater posterior mandibular ridge resorption when compared to clip attachments.

Immediate versus early loading of mini-implants supporting mandibular overdentures: a preliminary 3-year clinical outcome report.

PURPOSE: The aim of this preliminary clinical report was to evaluate and compare the clinical outcomes of immediate and early loaded mini-implants (MIs) supporting mandibular overdentures. MATERIALS AND METHODS: Thirty-six completely edentulous patients (20 men and 16 women) complaining of insufficient retention of their mandibular dentures were randomly assigned to two groups. Each patient received four MIs in the interforaminal area of the mandible using the nonsubmerged flapless surgical approach. In group 1 (G1), MIs were loaded with mandibular overdentures using the immediate loading protocol, while in group 2 (G2), MIs were loaded with overdentures using the early loading protocol. The cumulative survival rate was calculated using Kaplan-Meier analysis. Peri-implant health indices (Plaque Index/Bleeding Index), probing depths, and marginal bone levels were recorded for both groups after MI insertions and 6, 12, 24, and 36 months thereafter. RESULTS: The cumulative implant survival rates were 91.7% and 96.7% for G1 and G2, respectively. G1 recorded significantly higher Plaque Index, Bleeding Index, and probing depths than G2 after 12 months, while other observation times demonstrated no significant difference between groups. Most of the recorded marginal bone loss occurred in the first year, and no significant bone loss was noted in subsequent years. After 6 months, marginal bone loss was significantly higher in G1 compared to G2, but no significant differences between groups were noted thereafter. CONCLUSIONS: Within the limitations of this study's research design and duration of follow-up outcome analyses, immediate and early loading protocols showed good clinical results with favorable peri-implant tissue response 3 years after implant insertion. Early loading of MIs supporting a mandibular overdenture appears to be preferable to immediate loading.

Unsplinted implants retaining a mandibular overdenture with magnetic attachments: a short-term clinical study in controlled type 2 diabetic patients.

OBJECTIVE: This short-term prospective study evaluated the clinical outcome of unsplinted implants retaining a mandibular overdenture with magnetic attachments in controlled type 2 diabetic patients. METHOD AND MATERIALS: Twenty-eight completely edentulous patients (18 men and 10 women) with controlled type 2 diabetes mellitus received a total of 56 implants (two per patient) in the canine region of the mandible using the standardized two-stage surgical protocol. All patients complained of insufficient retention of their mandibular denture. New maxillary complete dentures and mandibular overdentures were fabricated. Overdentures were connected to the implants with magnetic attachments. Each implant was evaluated at the time of prosthetic loading, and 6, 12, and 24 months thereafter. Clinical evaluation was performed using Gingival Index (GI), Plaque Index (PI), probing depth (PD), implant stability (ISQ), and vertical bone loss (VBLO). Cumulative success and survival rates were calculated using life table analysis. RESULTS: After 2 years of overdenture insertion, there was a significant increase in PI, GI, PD, and VBLO. ISQ decreased significantly after 6 months of loading then increased again after 2 years. The cumulative survival and success rates of the implants were 91% and 87.5% respectively. CONCLUSION: Within the limitations of this study, the clinical outcome of unsplinted implants retaining a mandibular overdenture with magnetic attachments in controlled type 2 diabetic patients was favorable after 2 years. However, long-term randomized controlled trials are needed to compare the clinical outcome of unsplinted implants in diabetic and nondiabetic patients.

Changes in the edentulous maxilla with ball and telescopic attachments of implant-retained mandibular overdentures: a 4-year retrospective study.

OBJECTIVE: This retrospective study investigated the clinical and radiographic changes in the edentulous maxilla in patients with either ball or telescopic attachments of implantretained mandibular overdentures. METHOD AND MATERIALS: Thirty-two completely edentulous patients (21 males and 11 females) received two implants in the canine region of the mandible. New maxillary complete dentures and mandibular overdentures were fabricated. Overdentures were connected to the implants either with ball (group 1, n = 16) or telescopic (group 2, n = 16) attachments. Retention and stability of the maxillary denture as well as mucosal changes of the maxillary ridge were recorded after 4 years of denturewearing. Traced rotational tomograms were used for measurements of maxillary alveolar bone loss. The proportional value between bone areas and areas of reference not subject to resorption was expressed as a ratio (R). Change in R immediately before (T0) and after 4 years (T4) of overdenture insertion was calculated for the anterior and posterior regions of the maxilla. RESULTS: After 4 years of denture-wearing, maxillary denture retention was significantly higher in group 1 than in group 2, while occurrence of flabby ridges was significantly higher in group 2 than in group 1. The change in R of the anterior region of the maxilla was significantly higher than the change in the posterior region in both groups. Group 2 showed significant anterior residual ridge resorption compared to group 1. CONCLUSION: Telescopic attachments for implant-retained mandibular overdentures are associated with increased maxillary ridge resorption and flabbiness, and decreased maxillary denture retention when compared to ball attachments.