Biomechanical Analysis of Palateless Splinted and Unsplinted Maxillary Implant-Supported Overdentures: A Three-Dimensional Finite Element Analysis.

The objective of this study was to compare the distribution of stress in the maxillary bone, dental implants, and prosthetic components supporting implant-supported maxillary overdentures with partial palatal coverage, in both splinted and unsplinted designs. Two models of maxillary overdentures were designed using the Exocad Dental CAD program, which included cancellous and cortical bone. The complete denture design and abutments (locator abutments in the unsplinted and Hader bar with Vertix attachments placed distally in the splinted variant) were also designed. The denture material was PEEK (Polyetheretherketone), and the method used to analyze patient-specific 3D X-ray scans was 3D QCT/FEA (three-dimensional quantitative computed tomography-based finite element analysis). Loading was divided into three load cases, in the frontal region (both incisors of the denture) and distal region (both molars and first premolar of the denture). The forces applied were 150 N with an oblique component with a buccal inclination of 35° in the frontal region, and 600 N with a buccal inclination of 5° (molars) or solely vertical (premolar) in the distal region. The model with locator abutments showed higher stresses in all load cases in both analyzed implant variants and in the maxilla. The differences in stress distribution between the splinted and unsplinted variants were more significant in the distal region. According to the results of the present study, the amount of stress in bone tissue and dental implant parts was smaller in the splinted, bar-retained variant. The findings of this study can be useful in selecting the appropriate prosthetic design for implant-supported maxillary overdentures with partial palatal coverage.

Immediate loading of dental implants in edentulous mandibles using Locator attachments or Dolder bars: A 9-year prospective randomized clinical study.

AIM: To evaluate the long-term survival, incidence of prosthetic/technical and biological complications and the oral-health-related quality of life in patients with an edentulous mandible who were fitted with overdentures on two immediately loaded implants in the symphyseal area. MATERIALS AND METHODS: Forty-six patients with edentulous mandibles received two immediately loaded implant-retained dentures with either two Locator attachments or egg-shaped bar attachments. Implant outcomes were recorded after a period of observation of 9 years and included prosthetic complications, modified gingiva index (mGI), modified plaque index (mPI), oral health impact profile (OHIP-G) and radiographic estimation of bone loss. RESULTS: In 2020/2021, 27 patients with 54 implants were still available for follow-up. In total, nine implants in six patients were lost. Survival was 89.1% in the bar group and 91.3% in the Locator group. Implant success was 84.6% in the Locator group and 76.9% in the bar group. The mPI values were significantly higher in the bar group than in the Locator group, whereas no difference was seen in the mGI values. During the observation period, 152 prosthetic complications occurred, but the OHIP-G score did not differ significantly. CONCLUSIONS: There was no difference in implant survival between Locator or joint bar attachments over a 9-year observation period. Joint bar attachments were associated with slightly more complications, while patients in the Locator group were able to maintain better oral hygiene. The study was registered in the German Register of Clinical (Trials DRKS00004245).

Maxillary implant overdentures on two or four implants. A prospective randomized cross-over clinical trial of implant and denture success and survival.

OBJECTIVES: To determine implant survival and success of four conventionally but initially asynchronously loaded implants in implant-supported overdentures for the edentulous maxilla, in participants with opposing mandibular two-implant overdentures. MATERIAL AND METHODS: Twenty-six participants received four implants in the region of the maxillary canines and molars. After healing, 24 of these participants (mean age: 68.3 years) were randomly allocated to one of two treatment groups, and the adapted overdenture was attached to two unsplinted cylindrical attachments. The other two matrixes remained unattached to the implants for 3 months. After this period, the other two implants were loaded for 3 months (cross-over design). Then, all four implants were loaded for another 3 months. Kaplan-Meier curves were used to evaluate survival and success of implants and dentures. RESULTS: During the active prosthetic study phase, three participants lost one implant. Two participants lost three implants during the recall period. Implant survival after loading was 93.8% after a mean observation period of 3.1 years. Denture survival was 100%, but denture success was 95.8%, due to major prosthetic complications. Most participants preferred four implants to two. CONCLUSIONS: Within the limitations of the study, it can be concluded that maxillary implant overdentures on two or four implants are both recommendable treatment options. Two posterior implants are not superior to two anterior implants under overdentures retained by unsplinted cylindrical attachments. Implant and prosthetic complications and aftercare measures are common but are mostly easy to handle. However, 23 of the 24 participants preferred the 4-implant maxillary overdenture.

Customization of attachments in tooth supported overdentures: Three clinical reports.

In elderly patients with few remaining teeth, overdenture is a good treatment option. Roots beneath the denture protect the alveolar ridge, offer proprioception and improve retention, stability and masticatory efficiency of dentures. Customization of attachments available is a viable alternative for some patients in which prefabricated attachments cannot be placed or in which cost is a factor; to improve the final outcome of the treatment. Due to competitive commercialization, implant treatment has become the norm in current dentistry and the concept of tooth supported overdentures has eclipsed, but with proper case selection, thorough treatment planning and modifications in the denture such as customization of attachments, amalgam stops, cross-linked teeth, and metallic mesh can be applied to prolong the longevity and success of the attachment overdenture prosthesis.

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

PURPOSE: To evaluate the influence of implant position on clinical and radiographic outcomes of Locator-retained mandibular overdentures MATERIALS AND METHODS: Fifteen edentulous participants with compromised bone at canine regions of the mandible were given 2 implants in the premolar areas (study group, PM). The control group (CA) consisted of 15 participants who received 2 implants in the canine regions, matched to PM and assigned as historical control. For study and control groups, mandibular dentures were constructed and attached to the fixtures with Locator attachments using the delayed loading protocol. Clinical (plaque scores, gingival scores, pocket depth, and implant stability) and radiographic (marginal bone loss) outcomes were assessed after denture delivery (T0), 6 months (T6), and 12 months (T12) later. RESULTS: The survival rate was 100% in both groups. All clinical and radiographic parameters increased significantly with time. No significant difference in plaque scores, gingival scores, or implant stability between groups was observed. PM group recorded significantly higher pocket depth and marginal bone loss than CA group at T6 and T12. CONCLUSIONS: Within the limits of this short-term clinical study, canine position for implants retaining mandibular overdentures with Locator attachments is preferred over the first premolar position, as it was associated with reduced peri-implant pocket depth and marginal bone loss after 1 year.

Clinical performance of LOCATOR® attachments: A retrospective study with 1-8 years of follow-up.

The use of LOCATOR® attachments in implant-supported removable dental prostheses (ISRDPs) has been evidenced with conflicting clinical behavior in literature. This retrospective study aimed to investigate the long-term clinical performance of LOCATOR® attachments by evaluating the frequency of the encountered mechanical complication events (MCEs) and the factors that play a role in attachment wear (AW). The study recruited participants with ISRDPs on LOCATOR® attachments. Clinical parameters, number of MCEs (attachment replacements, attachment loosenings, denture cap-related events, loss of retention and/or insert, and implant fractures), and AW were recorded. Nonparametric tests were applied for statistical analyses (𝛼=0.05). Baseline demographics for the recruited 47 participants (mean age: 72.0 ± 9.0 years) revealed an implant survival rate of 94.9% (mean observation period: 54.8 months), average peri-implant probing depths, bleeding on probing scores, and plaque scores of 1.80 ± 1.50 mm, 0.70 ± 0.90, and 0.81 ± 0.90, respectively. MCEs were directly influenced by the time in use (p < 0.001). The most frequently encountered MCEs were loss of retention (p < 0.001) and denture cap-related complications (p = 0.004). AW was found to be significantly higher in the maxilla than in the mandible (p = 0.028); in the maxilla, the vestibular (p = 0.005) and mesial (p = 0.01) aspects were the most common wear sites. Maxillary implant overdentures revealed more vestibular AW (p = 0.013). In prostheses supported by >3 implants, vestibular (p = 0.046) and mesial (p = 0.032) AW were common. Lingual AW (p = 0.021) was observed more frequently when the support was <3 implants. Loss of retention and AW are the most common complications encountered with LOCATOR® attachments. Therefore, a modification in the attachment design along with an amelioration of the attachment surface may help decrease the maintenance needs and further enhance its clinical performance.

Influence of Implant Positions and Occlusal Forces on Peri-Implant Bone Stress in Mandibular Two-Implant Overdentures: A 3-Dimensional Finite Element Analysis.

The aim of this study was to evaluate and compare the bone stress around implants in mandibular 2-implant overdentures depending on the implant location and different loading conditions. Four 3-dimensional finite element models simulating a mandibular 2-implant overdenture and a Locator attachment system were designed. The implants were located at the lateral incisor, canine, second premolar, and crossed-implant levels. A 150 N unilateral and bilateral vertical load of different location was applied, as was 40 N when combined with midline load. Data for von Mises stress were produced numerically, color coded, and compared between the models for peri-implant bone and loading conditions. With unilateral loading, in all 4 models much higher peri-implant bone stress values were recorded on the load side compared with the no-load side, while with bilateral occlusal loading, the stress distribution was similar on both sides. In all models, the posterior unilateral load showed the highest stress, which decreased as the load was applied more mesially. In general, the best biomechanical environment in the peri-implant bone was found in the model with implants at premolar level. In the crossed-implant model, the load side greatly altered the biomechanical environment. Overall, the overdenture with implants at second premolar level should be the chosen design, regardless of where the load is applied. The occlusal loading application site influences the bone stress around the implant. Bilateral occlusal loading distributes the peri-implant bone stress symmetrically, while unilateral loading increases it greatly on the load side, no matter where the implants are located.

Evaluation of the clinical effects of implant-supported overdenture with ball or Locator attachment / 实用口腔医学杂志

Objective:To evaluate the clinical effects of ball attachment and Locator attachment for implant-supported overdenture.Methods:67 cases with edentulous jaw were treated with 150 Straumann and Bego implants and implant-supported overdentures using ball attachments Locator attachments,respectively.All cases were followed up regularly,biological and mechanical complications were observed,the patient satisfaction after restoration was compared between groups.Statistical analysis was performed using SPSS 17.0 software.Results:Follow-up was completed in 58 cases,25 with ball attachment,26 with Locator attachment and 7 with ball changed by Locator.Biological complications comparison showed that the incidence of gingival hyperplasia in the ball group was higher than that in the Locator group(P ＜ 0.05).There was no statistical difference of mechanical complications between the 2 groups (P ＞ 0.05),but the incidence of all kinds of mechanical complications in the Locator group was less than those in the ball group,the average repair frequency of the ball and Locator group was 1.9 times and 0.9 times respectively.Patients'satisfaction on chewing and retention was higher in the Locator attachment group than that in the ball attachment group(P ＜ 0.05).No statistical difference was found in patients' satisfaction between genders (P＞0.05),and no correlation of satisfaction was found with patients' age and follow-up time.Conclusion:The clinical effects of implant-supported overdenture using the Locator attachment is superior to that using the ball attachment.

Influence of different lubricants on the retentive force of LOCATOR(®) attachments - an in vitro pilot study.

OBJECTIVE: The aim of this in vitro pilot study was to evaluate the influence of an artificial saliva (AS) lubricant on the retentive force of a stud-type attachment (LOCATOR(®) ) for implant overdentures (IODs). METHODS: Twenty custom-made models simulating a two-IOD with parallel implant situation were fabricated using LOCATOR(®) attachments. The in vitro testing was carried out with an Instron(®) universal testing machine for a total of 10,000 insertion-removal cycles, for each model, in two different aqueous test mediums (Group 1: 0.9% sodium chloride solution (NaCl), n = 10; Group 2: AS, n = 10). Changes in the mean retentive force (F) were plotted against the cycle numbers #10, #100, #1000, #5000, and #10,000. Mixed regression models were applied for statistical analyses. RESULTS: A mixed regression (not considering interactions) predicted, compared to cycle #10, higher retentive forces at cycles #100 (P < 0.0001), #1000 (P = 0.017), similar forces at #5000 (P = 0.277), and lower forces at #10,000 (P = 0.012); there was no overall effect of the medium (P = 0.159). A second statistical model, employing the interaction term "cycle##medium", confirmed similarly the effect. Although the interaction term was significant at cycle #100 (p = 0.045), there was no significant difference between the two groups (P = 0.140). CONCLUSION: In this in vitro pilot experiment, there was no difference in mean retentive forces of the LOCATOR(®) attachments when tested with either 0.9% NaCl or a Glandosane(®) -like artificial saliva lubricant. A larger scale study may still confirm the superiority of either lubricant for quasiclinical bench experiments.