Maxillary Implant Overdentures Research Articles

Axial and Nonaxial Retention Forces of Different Designs of Milled Bar Attachments for Maxillary Implant Overdentures: An In Vitro Study.

To compare the axial and nonaxial retention forces of different milled bar attachment designs for maxillary implant overdentures. Four implants were placed in the canine and second premolar areas of an edentulous maxillary ridge model and connected to a cobalt-chromium milled bar either with or without Locator attachments. According to the type of bar and overlying housing, the following groups (n = 10 each) were investigated: group 1 (MWM) = milled bar without attachments and metal housing; group 2 (MWP) = milled bar without attachments and PEEK housing; group 3 (MAM) = milled bar with Locator attachments and metal housing; and group 4 (MAP) = milled bar with Locator attachments and PEEK housing. Axial and nonaxial (anterior, posterior, and lateral) retention forces were measured both at baseline and after wear simulation, then compared between groups and dislodging directions. MAM showed the highest axial (53.20 ± 2.28 N) and nonaxial (anterior [33.80 ± 1.48 N], posterior [37.60 ± 2.07 N], and lateral [34.40 ± 1.67 N]) retention forces at baseline, followed by MAP, then MWM, and MWP (P < .001). MAP showed the highest axial (42.80 ± 2.28 N) and nonaxial (anterior [24.00 ± 1.58 N], posterior [29.40 ± 2.07 N], and lateral [27.80 ± 1.64 N]) retention forces after wear simulation, followed by MAM, then MWP, and finally MWM (P < .001). MAM showed the highest axial (25.25 ± 2.45 N) and nonaxial (anterior [28.29 ± 4.03 N], posterior [24.40 ± 3.25 N], and lateral [25.55 ± 1.65 N]) retention loss, followed by MWM, then MAP, and finally MWP (P < .001). For all groups, the highest retention forces were noted with axial dislodging, followed by posterior dislodging, then lateral dislodging, and finally vertical dislodging (P < .001). Milled bars with PEEK housings and Locator attachments for maxillary implant overdentures were associated with the highest axial and nonaxial retention forces after wear simulation, while milled bars with metal housing and no attachments showed the lowest forces. Milled bars with metal housing and attachments showed the highest retention loss, while milled bars with PEEK housing with no attachments showed retention gain.

Case Series on the Long-Term Effect of Three Different Types of Maxillary Implant-Supported Overdentures on Clinical Outcomes and Complications.

(1) Long-term data on maxillary implant overdentures (IODs) are scarce. This case series evaluated three types of IODs supported by six, four or three implants (Anyridge®, Mega’Gen Implant Co., Ltd., Daegu, South-Korea), after 3–5 years in function. (2) A total of 31 patients, with 132 implants, were non-randomly allocated based on available bone or financial limitations. IOD-6 received a telescopic overdenture; IOD-4 a bar; and IOD-3, non-connected implants with locator abutments. Implant survival, bone level changes, probing pocket depth (PPD), plaque index, bleeding on probing (BOP), and technical, biological and aesthetic complications were registered. Impact of suprastructures on bone loss and PPD was analyzed using mixed-effect linear regression models. Differences between groups were analyzed using the ANOVA test for BOP, and Kruskal Wallis test for complications. (3) In total, 23 patients participated in the follow-up (9 female, 14 male), with average age of 62.2 years; 7, 11 and 5 patients in IOD-6, IOD-4 and IOD-3, respectively. Implant survival after 4.4 years on average, was 98% in total; 100%, 97.8% and 93.3% for IOD-6, IOD-4 and IOD-3, respectively. Mean bone loss corresponded to 0.68 mm (SD 1.06, range −4.57–1.51), 0.39 mm (SD 1.06, range −3.6–2.43), and 1.42 mm (SD 1.68, range −5.11–0.74) for IOD-6, IOD-4 and IOD-3, respectively. A statistically significant difference was seen in bone level when comparing IOD-6 to IOD-3 (p = 0.044), and IOD-4 to IOD-3 (p = 0.018). Mean PPD was 3.8 mm (SD: 0.69; range 2.5–5.3), 3.5 mm (SD 0.59; range 2.33–5), and 3.2 mm (SD 0.56; range 2–4) for IOD-6, IOD-4 and IOD-3, respectively, and differed significantly between IOD-6 and IOD-3 (p = 0.029). Incidence of peri-implantitis was 1%. No differences were seen for complications between groups. (4) Maxillary IOD supported by four to six implants is the most reliable treatment regarding implant survival and peri-implant health. More research is needed in the clinical outcomes, in particular the peri-implant health, and complications of maxillary IODs, especially with a reduced number of implants.

Influence of Implant Distribution and Palatal Coverage on the Strain of Splinted Implant and Overdenture in Maxillary Implant Overdentures.

Implant overdentures with splinted attachments have been used in clinical practice, and the effect of splinting on implants has been reported frequently. However, the effect of implant configuration of more than four implants and covering the palate with an overdenture has not been sufficiently examined. The purpose of this study was to reveal the effects of implant configuration and palatal coverage on both implant and denture strain in maxillary implant overdentures using splinted implants. Six implants were placed in the anterior, premolar, and molar areas in a maxillary edentulous model. Four strain gauges were attached to the implant surface, and Dolder bar attachments were used to splint implants distributed in various configurations. Two types of maxillary experimental dentures (with/without palatal coverage) were fabricated, and two strain gauges were attached at the midline. A vertical load of 98 N was applied, and the strains on the dentures and implants were measured. The strain measurements were compared using one-way analysis of variance and t test (P = .05). When comparing the implant strains, the strain was significantly smaller on the anterior and premolar implants when six implants were used, but there was no significant difference among the different implant configurations in the strain on the molar implants. Strains on anterior implants of the palateless overdenture were significantly greater than those of the overdenture with palatal coverage. When four implants were used, the strain on the palatal side of dentures without palate was significantly greater than that on those with palatal coverage. When six implants were used, there was no significant difference in the strain on either side between two types of dentures. When implants were splinted to each other using a denture without palatal coverage, the strain of dentures when six or two anterior and two posterior implants were used was lower. The difference of denture strains between two types of dentures was not significant when six implants were used, but was significant for all other configurations. Also, the difference of implant strains between two dentures was significant in anterior implants regardless of implant configuration.

Influence of Rigid Bar and Nonrigid Double Crown Attachments on Maxillary Implant Overdentures: An In Vitro Study with Differential Bone Quality.

To evaluate the bending strain exerted on a maxillary implant overdenture supported by rigid bar and nonrigid double crown connectors in models of high- and low-quality bone. Four implants were embedded in acrylic resin models of an edentulous maxilla simulating good- and poor-quality bone at the canine and second premolar regions bilaterally. A bar (cross-section dimension: 5 × 5 mm; bilateral distal extension: 10 mm) and double crown connectors with a metal framework (same morphology as the bar) were attached to these implants and placed under a constant 49 N vertical load at the anterior and cantilever regions of both superstructures. The bending strain on the implants was measured by strain gauges attached to the implant surfaces. In good-quality bone with cantilever loading, the strain--which was highest near the load for both attachment systems--was highly concentrated in the rigid bar system but dissipated through the double crown connector. The directionality of the bending moment was homogenous on the two attachments. In poor-quality bone, strains were significantly lower and more variable, especially for double crown connectors, and there was heterogeneity in the directions of the bending moment. Within the limitations of this study, bar and double crown connectors have identical biomechanical features in good-quality edentulous maxillary bone, but have divergent properties in poor-quality bone.

Clinical Results for Maxillary Implant Overdentures with Prosthetic Systems: A Literature Review

Clinical Results for Maxillary Implant Overdentures with Prosthetic Systems: A Literature Review

Effect of Attachment Type on Implant Strain in Maxillary Implant Overdentures: Comparison of Ball, Locator, and Magnet Attachments. Part 1. Overdenture with Palate.

Implant overdentures with attachments have been used in clinical practice and the effect of attachments on implant strain has been frequently reported. However, most studies have focused on mandibular overdentures; there are few reports on maxillary overdentures. The purpose of this study was to examine the influence of attachment type on implant strain in maxillary overdentures under various implant configurations. A maxillary edentulous model with implants and experimental overdentures were fabricated. Four strain gauges were attached to each implant, positioned in anterior, premolar, and molar areas. Three types of unsplinted attachments-ball, locator, and magnet-were set on the implants under various implant configurations. A vertical occlusal load of 98 N was applied through the mandibular complete denture, and implant strain was compared using the Kruskal-Wallis test. Ball attachments caused the greatest amount of strain, while magnet attachments caused the least amount under all conditions. For all attachments, two anterior implants caused significantly more strain than four implants (P < .05). No significant difference was observed between subtypes in four-implant configurations except when using locator attachments. When using unsplinted attachments for maxillary implant overdentures, magnet attachments are recommended to reduce implant stress. Using only two implants, especially two anterior implants, is not recommended regardless of attachment type.

Effect of Attachment Type on Denture Strain in Maxillary Implant Overdentures: Part 1. Overdenture with Palate.

This study examined the effects of attachments on strain in maxillary implant overdentures supported by two or four implants. A maxillary edentulous model with implants inserted into anterior, premolar, and molar areas was fabricated, and three types of unsplinted attachments-ball, locator, and magnet-were set on the implants distributed under various conditions. Maxillary experimental dentures were fabricated, and two strain gauges were attached at the anterior midline on the labial and palatal sides. A vertical occlusal load of 98 N was applied and shear strain of the dentures was measured. On both sides, magnet attachments resulted in the lowest shear strain, while ball attachments resulted in the highest shear strain under most conditions. However, differences in shear strain among the three attachment types were not significant when supported by four implants, especially molar implants. Shear strain of the maxillary implant overdenture was lowest when using magnet attachments. Magnet attachments mounted on four implants are recommended to prevent denture complications when using maxillary implant overdentures.

Effects of Reinforcement on Denture Strain in Maxillary Implant Overdentures: An In Vitro Study Under Various Implant Configurations.

Maxillary implant overdentures are often designed without palatal coverage to maximize wearer comfort. Although palateless dentures have been reported to be less rigid than conventional dentures, and require reinforcement to prevent complications, there is little documentation about the effects of such reinforcement. The purpose of this study was to examine the effects of reinforcement on the strain on maxillary implant overdentures supported by implants in a variety of configurations. A maxillary edentulous model with implants inserted in the anterior, premolar, and molar area was fabricated. Five types of experimental overdentures, with and without reinforcement, were fabricated, and two strain gauges were attached at the anterior midline of the labial and palatal sides. A vertical occlusal load of 98 N was applied through a mandibular complete denture, and the shear strain on the denture was measured. The measurements were compared using the Kruskal-Wallis test (P = .05). On both the labial and palatal sides, the strain on the palateless dentures with reinforcement was significantly lower than the strain on palateless dentures without reinforcement in all implant configurations (P < .05). The labial strain on the palateless dentures with reinforcement was almost as low as the labial strain on dentures with palatal coverage in most implant configurations. Reinforcement of a palateless implant overdenture with residual ridge reinforcement and a palatal bar could reduce the strain in the anterior midline to almost the same level as a denture with palatal coverage. This type of reinforcement may prevent prosthetic and implant complications.

Can Reinforcement of Maxillary Implant Overdentures Decrease Stress on Underlying Implants?

Reinforcement of maxillary implant overdentures is necessary not only for preventing prosthetic complications but also for protecting underlying structures, as it makes the denture base more rigid. However, few studies have investigated the effects of reinforcement on the underlying structure. The purpose of this study was to examine the effects of reinforcement on implant stress under various implant configurations and denture designs. A maxillary edentulous model with implants and experimental overdentures with and without palatal coverage and three types of cast reinforcement was fabricated. Four strain gauges were attached to the implants in the anterior, premolar, and molar areas. A vertical occlusal load of 98 N was applied through the mandibular complete denture, and the strain on the implants was compared using one-way analysis of variance (P = .05). In dentures with palatal coverage, reinforcement significantly decreased the strain on the anterior and molar implants. In palateless dentures, reinforcement with a palatal bar decreased the strain most on the anterior and molar implants. Reinforcement of maxillary implant overdentures decreased the strain on underlying implants, regardless of the denture design and implant configurations.

Influence of Palatal Coverage and Implant Distribution on Denture Strain in Maxillary Implant Overdentures.

As maxillary implant overdentures are being increasingly used in clinical practice, prosthodontic complications related to these dentures are also reported more often. The purpose of this study was to examine the influence of palatal coverage and implant distribution on the shear strain of maxillary implant overdentures. A maxillary edentulous model with implants inserted in the anterior, premolar, and molar areas was fabricated. Two kinds of experimental overdentures, with and without palatal coverage, were also fabricated, and two strain gauges were attached at the midline of the labial and palatal sides. A vertical occlusal load of 98 N was applied through a mandibular complete denture, and the shear strain in each denture was compared by analysis of variance (P = .05). In all situations, the shear strain in palateless dentures was significantly higher than in dentures with palate on both sides (P < .05). In dentures with palate, the shear strain was lower when anterior implants were present. Palateless maxillary implant overdentures exhibited much higher strain than overdentures with palate regardless of the implant distribution; this may cause more prosthodontic and implant complications. The most favorable configuration to prevent complications in maxillary implant overdentures was palatal coverage that was supported by more than four widely distributed implants.

Preliminary Observations Regarding Treatment Outcomes in Patients Treated with Maxillary Implant Overdentures in a University Clinic.

To evaluate the outcome of maxillary implant overdenture treatment in a selected patient sample. Eighteen out of a total of 26 patients who were prescribed overdentures supported by two to six implants each attended a follow-up clinical assessment. Evaluative criteria included oral health-related quality of life records using the OHIP-14 questionnaire. Good stability and retention were observed, and mechanical failure items were recorded in eight patients. No significant differences in OHIP-14 scores were found between patients treated with two to three implants and patients treated with five to six implants, or between groups treated with a denture with palatal or horseshoe design coverage. Maxillary implant overdenture treatment was assessed as a viable treatment option for the selected patient sample, even when only two supporting implants were prescribed.

Effects of clip materials on stress distribution to maxillary implant overdentures with bar attachments

Statement of problemFracture of maxillary implant overdentures (IODs) is a frequent complication. However, no studies have examined the effects of clip materials on the stress applied to maxillary IODs. PurposeThe purpose of this study was to investigate the effects of clip materials for bar attachments on the stress applied to maxillary IODs without palatal coverage. Material and methodsThis study included finite element analysis and a model study. An edentulous maxillary model with 4 implants and an experimental overdenture with bar attachments was fabricated. Strain gauges were attached on the denture surface adjacent to the end of each clip. Four clip conditions (n=5) were prepared: 3 plastic clips, 1 plastic clip, 3 metal clips, and 1 metal clip. A vertical load of 50 N was applied on the IOD. The maximum principle strain (MPS) was statistically analyzed by 2-way ANOVA and the post hoc Tukey HSD tests with clip materials and clip numbers as factors (α=.05). ResultsThe greatest stress was observed on the resin surface around the end of the clip on the loaded side. The MPSs between both clip materials (P=.048) and numbers (P<.001) differed significantly on the palatal side of the end of the center clip on the loaded side: the MPSs of the metal clips were significantly larger than those of the plastic clips, and the MPS of 1 clip was significantly larger than for 3 clips. ConclusionsThe stress around plastic clips tended to be lower than that around metal clips.