Implant-supported Mandibular Overdentures Research Articles

Resilient Stud Versus Bar Attachments for Immediately Loaded Implants Supporting Mandibular Overdentures: 1-year Randomized Controlled Clinical Trial.

This study aimed to examine clinical and patient-centered outcomes of resilient stud and stress-free bar attachments used for immediately loaded implants supporting mandibular overdentures. Thirty edentulous patients with sufficient bone mesial and distal to the mental foramen received new dentures. The patients were randomly assigned into two groups. After 3 months of adaptation, four implants were placed in the canine and second premolar areas of the mandible using computer-guided surgery and the flapless surgical approach. Overdentures were connected immediately to the implants using either resilient stud (Locator) or stress-free implant bar (SFI-Bar) attachments. Marginal resorption of bone, plaque and gingival indices, pocket depth, and implant stability were evaluated for both groups at baseline (prosthesis delivery) and 6 and 12 months thereafter. Implant survival and patient satisfaction were calculated after 12 months. For both groups, marginal bone loss (P < .043), plaque scores (P < .001), and probing depth (P < .002) increased significantly with time. SFI-Bar recorded lower marginal bone loss (P = .048) and higher plaque scores (P = .021) and probing depth (P = .001) than Locator after 12 months of denture insertion. The implant survival was 96.6% and 98.3% for Locator and SFI-Bar, respectively. No significant difference was found in the survival rate between groups (P = .56). Locator showed significantly higher general satisfaction, satisfaction with retention, comfort, and cleaning of overdentures compared with SFI-Bar (P < .001). Within the limits of this investigation, both resilient stud and stress-free bar attachments can be used successfully with mandibular four-implant overdentures subjected to an immediate loading protocol. However, studs may be preferred regarding peri-implant soft tissue health, patient satisfaction with retention, cleaning, and comfort, and stress-free bar attachments could be more effective in terms of marginal bone preservation.

Outcome of peri-implant maintenance care in patients with an implant-supported lower denture-A 3.5-year retrospective analysis.

BackgroundImplant‐supported overdentures represent a successful treatment for edentulous patients. As early diagnosis, detection and supportive care are considered key factors for the prevention of peri‐implant diseases, consistent maintenance of these implants is becoming increasingly relevant.PurposeThis retrospective analysis evaluated a cohort of edentulous patients with a mandibular implant‐supported overdenture over a period of 3.5 years during which the peri‐implant tissues were assessed.Materials and MethodsA total of 108 patients that had consistently adhered to the annual maintenance appointments was selected. The clinical peri‐implant pocket probing depth (PiPPD) and peri‐implant bleeding on probing score (PiBOP) were investigated. Data from the 3.5‐year follow‐up were compared to data from the baseline assessment.ResultsA 100% implant survival was reported after 3.5 years. The mean PiBOP showed a significant decrease over time (P = .028). The mean PiPPD was found significantly deeper for male patients both at baseline (P = .004) and 3.5‐year follow‐up (P < .001). Besides, the PiPPD for locator anchorages was found significantly deeper compared to ball anchorages at the 3.5‐year follow‐up (P = .026).ConclusionIn those patients that adhered to the annual maintenance visits during the 3.5 years after implant surgery a stable peri‐implant condition was observed. As future consideration, the comparison of the clinical outcomes of patients participating in the maintenance program with those that did not would make this observation even more meaningful.

Mandibular implant-supported overdenture: A systematic review and meta-analysis for optimum selection of attachment system.

Aim:This systematic review aimed to compare different attachment systems used in mandibular implant supported overdentures by assessing outcomes such as prosthodontic maintenance and complication, peri implant tissue changes, retention, and patient satisfaction for optimum selection of attachment system.Settings and Design:This systematic review conducted following Preferred Reporting Items for the Systematic Review and Meta Analysis (PRISMA) guidelines.Materials and Methods:A systematic electronic literature search was conducted through PubMed, The Cochrane Central Register of Controlled Trials (Central), and Science direct. A hand search was also performed for individual journals and reference lists of selected studies. Randomized controlled clinical trials and crossover clinical trials from 2010 to 2020 with follow up of more than 1 year were included. The Cochrane Collaboration's tool was used for assessing the risk of bias of included studies.Statistical Analysis Used:The statistical meta analysis was performed using Review Manager (RevMan) [computer program]. Version 5.4. Copenhagen: The Nordic Cochrane Centre, The Cochrane Collaboation, 2020.Results:Six studies that met the inclusion criteria possess the low risk of bias with follow up of more than 1 year were included in this systematic review. Out of four outcomes, meta analysis was performed for prosthodontic maintenance and peri implant tissue changes. Due to the limited availability of data, retention and patient satisfaction were reviewed systematically without meta analysis. The result of meta analysis for ball versus magnet attachment showed statistically significant differences in prosthodontic complications and maintenance, and ball attachment reported fewer complications than the locator attachment (risk ratio [RR] =0.55, confidence interval [CI] =95%, P = 0.03). Peri implant tissue changes were analyzed in the included studies as probing depth and marginal bone loss. The result of meta analysis for probing depth showed no statistically significant difference between bar versus telescopic type of attachment (RR = 0.20, CI = 95%, P = 0.74). The meta analysis results for marginal bone loss showed no statistically significant difference between bar versus telescopic type of attachment (mean difference = 0.35, CI = 95%, P = 0.10).Conclusion:It can be concluded from the current review that bar attachment provided the most superior retention. The telescopic attachment system not only showed the most favorable patient's satisfaction but also reported the least peri implant mucosal changes. The ball attachment system is a favorable choice for limited inter arch space and parallel implant placement.

The effects of bone remodeling on biomechanical behavior in a patient with an implant-supported overdenture

This study aimed to clarify the effects of bone remodeling on biomechanical behavior in a patient with a mandibular implant-supported overdenture by comparing computed tomography-based finite element analyses (CT-FEA) with two time points of CT data. The present FEA was based on CT data collected from a 62-year-old female subject, who wore a mandibular implant overdenture supported by four dental implants with bar attachment. Two kinds of FE models were constructed from CT data taken at two time points: pre-implantation (Original-model) and 12 years post-implantation (Aged-model). FE models consisted of patient-specific model geometry and heterogeneous material properties. The deviation analysis was carried out to assess the changes in bone mass over a period of 12 years. The results show an averaging of intraosseous stress and strain energy density between the implant regions in the Aged-model. The results of the morphological assessments demonstrated that the bone mass and quality had significantly changed over 12 years. Area-specific bone resorption was also observed at the bone surrounding each implant. The combined findings indicate that the averaging of mechanical variables was due to chronological changes in bone morphology, suggesting adaptation to mechanical loads by peri-implant bone remodeling.

Comparison of Three Types of Stud Attachments on Retention and Strain Energy in the Mandibular Implant-Supported Overdentures

Background: The present in vitro study assessed he effects of three different Stud attachments on the retention and strain energy in the mandibular implant-supported overdentures.&#x0D; Methods: Two parallel implants (Implantium System) were placed on the mandibular canines’ regions and a chrome-cobalt casting framework was prepared as the denture base. The implant fixtures were installed on the canine location and the pulling was performed by three orthodontic wires in the Instron machine with a speed of 0.5 min/mm. Dislodging forces were applied to the housings in two vertical and oblique directions on three different Stud attachments (Ball, Kerator, Positioner). All three wires were connected to the device in the vertical position while one wire was separated from the molar’s region in the oblique loadings. The retention of these three attachments was statistically analyzed by means of one-way analysis of variance.&#x0D; Results: Significant differences were found between the attachments (F (2, 15) =33.01, p&lt;0.0001). Furthermore, Retention forces in the oblique loadings were significant differences between the attachments (F(2,15)=175.10, p&lt;0.0001). The effect size, calculated using eta squared, was 0.95, which is considered large. The strain energy was 4.08, 3.05 and 1.04 J for the Ball, Positioner and Kerator attachments in the vertical loadings and 4.05, 1.44 and 3.07 J in the oblique loading respectively.&#x0D; Conclusion: The retentive forces and strain energy of ball attachments were greatest than other studied attachments in the vertical and oblique loadings.

Comparison of ridge resorption and patient satisfaction in single implant-supported mandibular overdentures with conventional complete dentures: A randomised pilot study

PurposeTo compare ridge resorption (RR) and patient satisfaction in single implant-supported mandibular overdentures (SIMO) with conventional complete dentures (CCD) over a period of one year. Material and methodsThis prospective, randomized trial enrolled 30 completely edentulous participants following inclusion and exclusion criteria. The study was completed by 28 participants. Rehabilitation of 14 participants was done by using SIMO (group I) and CCD (group C) each according to randomization chart. For both the groups, RR was computed in millimeters from residual ridge height measured by using orthopantogram at 6 months (T1), 9 months (T2), and 12 months (T3) at 3 anatomic locations: maxillary posterior (L1), maxillary anterior (L2), and mandibular posterior (L3). Patient satisfaction was evaluated by using Geriatric Oral Health Assessment Index Hindi version (GOHAI-Hi) at 1week and 12 months after denture delivery. ResultsAt 12 months, minimum RR was observed at L2 of group I (0.62 ​± ​0.20 ​mm) and maximum RR was observed at L3 of group C (1.04 ​± ​0.15 ​mm). Comparison of ridge resorption between group I and group C was statistically significant at T3 (P ​= ​.001 for L1, P ​= ​.006 for L2, and P ​= ​.028 for L3). At T3, in group I, RR was more at L3 than L2 region (P ​= ​.011) and L1 region (P ​= ​.015). Statistically significant difference of GOHAI-Hi scores was observed between group I and group C at end of 12 months (P ​= ​.003). ConclusionsSIMO cause less RR and higher patient satisfaction as compared to CCD and can be recommended with higher predictability of success than CCD.

Observation of the effect on immediate mandibular implant-supported overdenture of micro implant system of Italy

The study was design to investigate the clinical effect of Micro implant system in Italy on immediate mandibular implant-supported overdenture. A total of 192 patients with mandibular edentulous treated in our hospital were randomly divided into 2 groups in which the control group consisted of 96 patients treated with immediate mandibular implant-supported overdenture by Xive implant system, while the observation group included 96 cases treated with the overdenture by Italy Micro implant system. Patients were followed up for 1 year and then the states of implant-borne overdentures, marginal bone resorption around alveolar bone, the compatibility of implant restorations with adjacent teeth, adverse events and satisfaction degree were compared between the groups. According to the results of 1-year follow-up, the resorption around alveolar bone of the observation group was significantly higher than that of the control group (p&lt;0.05). In the observation group the differences in labial gingival margin position, gingival color and texture were significantly better (p&lt;0.05) as compared to control group. The incidence of adverse events was notably lower (p&lt;0.05). The Italy Micro implant system has significant curative effect on mandibular implant-supported overdentures with good compatibility of the implant restorations with adjacent teeth and low incidence rate of adverse reactions, so it is worthy of clinical application and spreading.

Milled Bar with PEEK and Metal Housings for Inclined Implants Supporting Mandibular Overdentures: 1-Year Clinical, Prosthetic, and Patient-Based Outcomes.

This investigation aimed to evaluate clinical, prosthetic, and patient-based outcomes of a milled bar with polyether ether ketone (PEEK) and metal housings for inclined implants supporting mandibular overdentures. Eighteen edentulous participants received four implants in the interforaminal area of the mandible (two vertically and two distally inclined), and implants were connected with milled bars. Overdentures were attached to the bars with PEEK female housing (test group). The control group consisted of participants who received milled bar overdentures with conventional metal housings but were case matched to the test group and served as a historical cohort. Clinical parameters (Plaque Index, Gingival Index, pocket depth, and bone loss) were measured at baseline, 6 months, and 12 months. Patient satisfaction (using visual analog scale) and prosthetic complications were recorded after 12 months. The control group showed a significantly higher plaque score and marginal bone resorption compared with the test group. The test group showed higher satisfaction with retention, stability, speech, and esthetics compared with the control group (P < .048). The test group showed a significantly lower incidence of female housing wear (P = .017), plastic clip wear (P < .001), and plastic clip fracture/renewal (P = .049) than the control group. No difference between groups was noted for other clinical, prosthetic, and patient-based outcomes. PEEK housing of a milled bar may be a successful alternative to conventional metal housing for inclined implants supporting mandibular overdentures, as it is associated with favorable clinical, prosthetic, and patient-based outcomes after 1 year.

A 5-Year Retrospective Study Evaluating Periodontal Health and Oral Health-Related Quality of Life of Implant-Supported Overdentures With Locator and Magnetic Attachments.

This study compared peri-implant vertical bone loss, the periodontal index, prosthodontic maintenance requirements and oral health-related quality of life (OHQoL) of patients using mandibular implant-supported overdentures with 2 different attachment systems after an average of 5 years of use. Sixteen mandibular overdenture patients with magnet attachments (group 3), 24 with implant-supported mandibular overdentures with Locator attachments (group 2), and 25 conventional complete denture patients (group 1) were included in the study. The existing at least 5 years old dentures of all patients were evaluated for prosthodontic maintenance by the same prosthodontist and the patients were administered the oral health impact profile-14-Turkish version (OHIP-TR-14) questionnaire. Peri-implant tissue health was evaluated clinically in terms of plaque scores, bleeding scores, probing depth, and gingival index. Radiographic evaluation was performed in terms of peri-implant vertical bone loss. Radiographic evaluations were performed 5 years after overdenture insertion. There were no statistically significant differences between the groups in terms of total OHIP-TR-14 scores (P > .05). Although the average vertical bone resorption measured in group 2 at the end of 5 years was 1.38 mm, there was an average vertical bone loss of 1.45 mm in group 3, but this difference was not statistically significant (P > .05). Among the periodontal health indicators, there were no statistically significant differences in the mean values for periodontal indexes. According to results of the study, there were no differences in peri-implant vertical bone loss in groups 2 and 3, in periodontal health in mandibular overdentures with groups 2 and 3, or between total OHIP-TR-14 scores of patients in all groups.

Assessment of masticatory function of mandibular implant-supported overdenture wearers: A 3-year prospective study

Statement of problemWearers of mandibular complete dentures (CDs) often complain of retention and stability problems resulting in poor masticatory function. Evidence suggests that a mandibular overdenture (MOD) stabilized by 2 implants represents the treatment of choice to improve stability and masticatory function. Measurements are needed of the improvement in masticatory function after providing mandibular implant-stabilized overdentures. PurposeThe purpose of this prospective clinical study was to evaluate the changes in masticatory function from baseline (T0) to 3 months (T1) and 3 years (T2) in participants with MODs and to assess the effect of baseline mandibular bone height and volume on masticatory function after 3 years. Material and methodsParticipants were assessed for masticatory function by using masticatory performance involving paraffin wax cubes as an objective measure and by using masticatory ability involving a questionnaire as a subjective measure. Edentulous individuals presenting for replacement dentures were provided with conventional mucosa-supported prostheses and evaluated for masticatory function after a 3-month settling-in period (baseline measure). Before implant placement, baseline measures of bone height and volume were recorded from cone beam computed tomography (CBCT) images. The prostheses were then converted to implant-stabilized mandibular overdentures while any maxillary prostheses remained supported by the mucosa. Masticatory function was reassessed at 3 months and 3 years after insertion of the mandibular overdentures, and the mean changes from baseline were analyzed with the Wilcoxon signed-rank test. The effect of variables on masticatory function was determined by using multivariate linear regression analyses. ResultsA total of 23 participants were included in the study, with only 1 participant not completing the 3-year assessment. Significant improvement was observed in the masticatory performance (mixing ability index) (P<.01) and masticatory ability score (P<.001) from baseline to 3 months and baseline to 3 years. Bone height and volume had no significant effect on the improvement of masticatory function after conversion to an implant-stabilized mandibular overdenture. ConclusionsMasticatory function significantly improved after 3 months and was maintained over 3 years in participants with implant-stabilized mandibular overdentures. However, baseline bone height and volume had no significant effect on these changes in masticatory function after 3 years

A comparison of the retentive force of ball and socket attachment versus magnet attachment in mandibular overdentures: A randomized control trial

Aim: To compare the retention and patient satisfaction of implant-supported mandibular overdentures with ball and socket attachment versus magnet attachment. Materials and Methods: Twenty-four participants (10 males and 14 females) were divided into two equal groups (n = 12). Both groups received implant-supported mandibular overdentures retained by ball and magnet attachment. Two implants were installed in the canine region bilaterally. Evaluation of retention was made at overdenture insertion, 3, 6, and 12 months. Patient satisfaction evaluation with Oral Health Impact Profile Questionnaire-14 (OHIP-14) was made at overdenture insertion 3, and 12 months subsequently. Results: The ball group showed a statistically significantly higher retention force (P < 0.05) than the magnet group at insertion, 3 and 6 months. The ball group had a statistically significantly lower mean of physical disability and physical pain (P < 0.05) than the magnet group through all follow-up. One-way analysis of variance (ANOVA) test was used to compare between groups as well as to study the changes by time within each group. Conclusion: Both implant-supported mandibular overdenture retained with magnet or ball and socket attachments consider a successful treatment option with superior improvement in the ball and socket group.

Comparative evaluation of crestal bone levels around endosseous implants as influenced by conventional and diode laser during second-stage surgery in mandibular implant-supported overdenture: An in vivo study.

Aim:This study aims to evaluate and compare the crestal bone levels around implants as influenced by conventional and diode laser during second-stage surgery in an edentulous mandible using cone beam computed tomography (CBCT) and digital radiography (DR).Settings and Design:A split-mouth in vivo prospective study on edentulous patients involving placement of two implants in mandible followed by the comparison of two different techniques for second-stage surgery.Materials and Methods:The study was undertaken to evaluate the crestal bone change around 16 implant sites distributed in two groups (eight implants each) following two methods during second-stage surgery, i.e., Group 1 - Conventional second stage and Group 2 - Diode laser. Measurements were made on two sides (mesial and distal) using intraoral periapical and four sides (labial, lingual, mesial, and distal) using CBCT scans for both groups. These measurements were conducted at two time intervals for both, i.e., immediately after implant loading and twenty 4 weeks after implant loading. The values obtained were subjected to statistical analysis.Statistical Analysis Used:The normality of data was checked by Shapiro–Wilk's test. Intragroup comparison was compared using independent t-test by post hoc comparison by Bonferroni method (P < 0.05).Results:Crestal bone loss at the time of loading for Group 1 evaluated by CBCT was 0.950 ± 0.988 while after 24 weeks of loading, it was 1.388 ± 0.576. For Group 2, mean crestal bone loss was 1.200 ± 0.925 at the time of loading, and after 24 weeks, it was 1.512 ± 0.674. Crestal bone loss at the time of loading for Group 1 evaluated by DR was 1.075 ± 0.849 while after 24 weeks of loading, it was 1.562 ± 0.480. For Group 2, mean crestal bone loss was 1.162 ± 0.833 at the time of loading and after 24 weeks, it was 1.700 ± 0.498.Conclusions:In the present study, no statistically significant difference was observed in crestal bone loss between conventional and diode laser technique.

Evaluation of Stress Distribution on Mandibular Implant-Supported Overdentures With Different Bone Heights and Attachment Types: A 3D Finite Element Analysis.

The biomechanical behavior of the edentulous mandible with bone irregularities that has been rehabilitated with implant-supported overdentures has become an important factor for treatment planning. Restorative options, including dental implants with various attachments, affect the stress distribution. The purpose of this study was to evaluate the stress distribution of cortical bone around the implant neck and implant structures in overdentures with two different attachment types at the edentulous mandible and with different bone heights using three-dimensional finite element analysis. Five three-dimensional models of an edentulous mandible were designed and implemented. Ten models were constructed with ball and locator attachments. Static bilateral and unilateral vertical and oblique occlusal loads with magnitudes of 100 N were applied to the overdentures. The principal stresses were higher in the presence of oblique loads compared to vertical loads in all the analyzed models. Maximum principal stresses were observed around the mesial side of the contralateral implant, and the minimum principal stresses were noted around the distal side of ipsilateral implant during unilateral vertical loading. These patterns were reversed during oblique loadings. The ball attachment models yielded lower von Mises stress values than the locator models at all the loading conditions, while the stress distributions were similar in the models with the same and different bone levels. Correspondingly, bone corrections due to irregularities may not be necessary in terms of biomechanics. The results of this study may provide clinicians a better understanding for the mandibular overdenture design in the cases at which different bone heights exist.

What is the Impact of Implant-supported Mandibular Overdentures on Oral Health-Related Quality of Life? A Retrospective Study

Objective: Oral health-related quality of life (QoL) is significantly influenced by the type of the prostheses that is used for prosthetic rehabilitation of patients with complete edentulism. This study aims to retrospectively evaluate the outcomes of mandibular implant-supported overdentures (MODs) through patients’ perceptions by analyzing the results from OHIP-14 index.Methods: Relationships between OHIP-14 scores, and clinical and patient-based findings are investigated.Results: Forty-seven patients were included in the study. OHIP-14 scores ranged from 0 to 35, with a mean score of 5.81 (±6.89), indicating an overall “very high” quality of life. Patients with “very high” QoL had significantly lower pain scores than those with both “high” and “low” QoL (p=0.000, p=0.036 respectively). Further analysis revealed a positive correlation between total OHIP points and pain level (r= 0.738, p=0.000).Conclusion: Within the limitations of this study, it can be concluded that patients with complete edentulism of the mandible can effectively be rehabilitated with two implant-supported mandibular overdentures and be provided with a “very high” oral health-related QoL.

Improvement of Quality of Life with Implant-Supported Mandibular Overdentures and the Effect of Implant Type and Surgical Procedure on Bone and Soft Tissue Stability: A Three-Year Prospective Split-Mouth Trial.

In fully edentulous patients, the support of a lower dental prosthesis by two implants could improve the chewing ability, retention, and stability of the prosthesis. Despite high success rates of dental implants, complications, such as peri-implantitis, do occur. The latter is a consequence of crestal bone loss and might be related to the implant surface and peri-implant soft tissue thickness. The aim of this paper is to describe the effect of implant surface roughness and soft tissue thickness on crestal bone remodeling, peri-implant health, and patient-centered outcomes. The mandibular overdenture supported by two implants is used as a split-mouth model to scrutinize these aims. The first study compared implants placed equicrestal to implants placed biologically (i.e., dependent on site-specific soft tissue thickness). The second clinical trial compared implants with a minimally to a moderately rough implant neck. Both studies reported an improvement in oral health-related quality of life and a stable peri-implant health after three years follow-up. Only equicrestal implant placement yielded significantly higher implant surface exposure, due to the establishment of the biologic width. Within the limitations of this study, it can be concluded that an implant supported mandibular overdenture significantly improves the quality of life, with limited biologic complications and high survival rates of the implants.

Mandibular implant-supported overdentures in (frail) elderly: A prospective study with 20-year follow-up.

PurposeTo prospectively assess long‐term (20 year) clinical, radiographic, and patient‐reported outcomes of an elderly population provided with mandibular implant‐supported overdentures.Materials and MethodsA total of 53 elderly (aged ≥60 years at the time of treatment) were provided with two endosseous implants supporting a mandibular overdenture and a conventional maxillary denture. Outcome parameters—including implant loss, plaque index, gingival index, bleeding index, presence of calculus, probing depth, and satisfaction with implant‐supported overdenture—were scored 1, 5, 10, and 20 years after prosthetic treatment. Radiographic analysis was performed to assess peri‐implant bone changes. At the 20‐year evaluation, frailty (Groningen Frailty Index) and quality of life (EuroQol 5D) were additionally assessed.ResultsA total of 15 patients completed the 20‐year follow‐up. The 20‐year implant survival rate was 92.5%. Plaque index, bleeding index, and probing depth increased slightly over time, while gingival index and presence of calculus remained unchanged. Radiographic analysis revealed minor marginal bone loss during the first 10 years and no further loss thereafter. Participants were very satisfied with their prosthesis and reported a good quality of life. At the 20‐year evaluation, 64.3% of the patients were classified as frail.ConclusionsThe long‐term survival of implants supporting a mandibular overdenture is high. Although most elderly in the study became frail over time, peri‐implant health and marginal bone level remained at a satisfactory level.

Frequency of Lower Lip Paresthesia in Patients Receiving Implant-Supported Mandibular Dentures in Tabriz, Iran in 2017-2018

Background: Widespread use of dental implants in the past 15 years has resulted in an increase in complications associated with implant surgeries. The aim of the present study was to determine the frequency of lower lip paresthesia in patients receiving implant-supported mandibular overdentures. Methods: In this descriptive, cross-sectional study, 63 patients receiving implant-supported mandibular overdentures were evaluated. For clinical examination, the two-point discrimination test (2DP) was used before surgery and at 1-, 3- and 6-month postoperative intervals. Data was analyzed using descriptive statistical tests and chi-square test. Results: The results showed frequency rates of 19%, 4.8% and 4.8% for lower lip paresthesia at 1-, 3- and 6-month postoperative intervals. At 1-month postoperative interval, female patients exhibited a significantly higher rate of paresthesia compared to male patients (P = 0.035). Conclusions: Lower lip paresthesia was highly prevalent (19%) one-month after implant surgery; however, its frequency decreased over time. After 3 months, the frequency of paresthesia decreased by about 3 quarters (4.8%) and remained constant until 6 months after surgery. During the 1-month period after surgery, female patients had a high rate of paresthesia compared to male patients.

Three-dimensional finite element analysis of four-implants supported mandibular overdentures using two different attachments

Objective: To compare the biomechanical characteristics of four-implants mandibular overdentures supported by Locator attachment or bar-clip attachment under different mechanical loads using three-dimensional finite element analysis method. Methods: Two different models of four-implants supported mandibular overdentures using Locator attachment and bar-clip attachment (hereinafter called Locator model and bar-clip model) were established. Each model was subjected to five different mechanical loading conditions: 100 N vertical loading in central incisor (vertical load of incisor), 100 N vertical loading or oblique loading in canine (vertical or oblique loads of canines), 100 N vertical or oblique loading in mandibular first molar (vertical or oblique loads of mandibular first molar). The stress distributions in implants, peri-implant bone and mucosa were recorded under the above five conditions to evaluate the effects of different attachments on the biomechanical properties of implant-supported mandibular overdentures. Results: Regardless of loading conditions and types of attachments, the stress concentration in implants were located at the neck of implants, and the stress concentration in peri-implant bone was located in the cortical bone. The stress values in mucosa were always much smaller than those in implants and cortical bone. Regardless of loading positions (on canine or on mandibular first molar), the maximum stress at the bone interface around the implant under lateral loading was much higher than that under vertical loading. Under various loading conditions, the stress in implants and cortical bone of the Locator model (the highest von Mise stress value was respectively 79.5 and 22.3 MPa) were lower than that of bar-clip model (the highest von Mise stress value was 110.3 and 28.7 MPa respectively) while the maximum compressive stress in mucosa (0.198 MPa) in Locator model was slightly higher than that in the bar-clip model (0.137 MPa). Conclusions: In clinical practice, the lateral force applied to the implant-retained overdenture should be minimized to avoid complications caused by pathological loads. Under the same loading condition, the stress distributions in overdenture using Locator attachment are more dispersed, which is more conducive to long-term stability of implants.

Mandibular Overdentures Supported by Two vs Four Endosteal Implants: A Retrospective Cohort Study

Documentation of marginal bone resorption caused by implant-supported mandibular overdentures is scarce. This study sought to evaluate marginal bone resorption, survival rate, patient satisfaction, peri-implant soft tissue status, and prosthetic aftercare of mandibular overdentures supported by two vs four implants. This retrospective cohort study evaluated 92 edentulous patients presented to the Implant Center of Tehran University of Medical Sciences; out of which, 46 patients received overdentures supported by two Implantium implants (group A), while the remaining 46 received overdentures supported by four Implantium implants (group B). Standard radiographic indices were assessed following the delivery of overdenture and after 2 years of functional loading. Clinical evaluation was performed after 2 years of function. Data were analyzed using the t test (for continuous variables) and the Mann-Whitney test (for ordinal variables). In group A, two implants were lost in one patient. The groups were not significantly different in terms of clinical or radiographic parameters (p > 0.05). Patient satisfaction and prosthetic aftercare were not significantly different in groups A and B (p > 0.05). During the 2-year evaluation period, the clinical and radiographic parameters were the same in patients who received overdentures supported by two or four implants. Successful results may be obtained by the use of mandibular overdentures supported by two or four implants.

3D Finite Element Analysis to Assess the Stress Distribution Pattern in Mandibular Implant-supported Overdenture with Different Bar Heights

Proper stress distribution on dental implants is necessary in bar-retained implant overlay dentures. The purpose of the study is to comparatively assess the stress distribution pattern on the crestal bone at the bone-implant interface due to different bar heights using finite element models (FEMs). Eight 3D FEMs were developed from mandibular overdentures with two implants in the canine region separated by a distance of 20 mm. In these models, four different bar heights from the mucosa (0.5, 1, 1.5, and 2 mm) with 12 mm occlusal plane height were analyzed. A unilateral and a bilateral vertical load of 150 N were applied to the central occlusal fossa of the first molar and the stress of bone around the implant was analyzed by finite element analysis (FEA). By increasing the bar height, the maximum stress values around implants on the crestal bone were found to be increased in unilateral and bilateral loading models. In unilateral loading models, the maximum stress was found in a model with a 2 mm bar height (0.46 MPa) on the distal side of the ipsilateral implant, and in bilateral loading cases, the maximum stress was also found in a model with a 2 mm bar height (0.456 MPa). As the vertical cantilever increases (here the bar height), the maximum stress on the crestal bone increases. A minimum of 0.5 mm of space is sufficient between the mucosa and the inferior border of the bar to maintain oral hygiene. From the present study, it can be concluded that an increase in bar height causes an increase in stress levels on the peri-implant crestal bone.