• The Journal of Advanced Prosthodontics
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• v.8 no.2
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• pp.85-93
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• 2016

PURPOSE. The purpose of this study was to determine the effect of anchorage systems and palatal coverage of denture base on load transfer in maxillary implant-retained overdenture. MATERIALS AND METHODS. Maxillary implant-retained overdentures with 4 implants placed in the anterior region of edentulous maxilla were converted into a 3-D numerical model, and stress distribution patterns in implant supporting bone in the case of unilateral vertical loading on maxillary right first molar were compared with each other depending on various types of anchorage system and palatal coverage extent of denture base using three-dimensional finite element analysis. RESULTS. In all experimental models, the highest stress was concentrated on the most distal implant and implant supporting bone on loaded side. The stress at the most distal implant-supporting bone was concentrated on the cortical bone. In all anchorage system without palatal coverage of denture base, higher stresses were concentrated on the most distal implant and implant supporting bone on loaded side. CONCLUSION. It could be suggested that when making maxillary implant retained overdenture, using Hader bar instead of milled bar and full palatal coverage rather than partial palatal coverage are more beneficial in distributing the stress that is applied on implant supporting bone.

• The Journal of Korean Academy of Prosthodontics
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• v.42 no.4
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• pp.397-411
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• 2004

Purpose: The purpose of this study was to determine the effect of anchorage systems and palatal coverage of denture base on load transfer in maxillary implant-supported overdenture. Material and methods: Maxillary implant -supported overdentures in which 4 implants were placed in the anterior region of edentulous maxilla were fabricated, and stress distribution patterns in implant supporting bone in the case of unilateral vertical loading on maxillary right first molar were compared with each other depending on various types of anchorage system and palatal coverage extent of denture base using three-dimensional photoelastic stress analysis. Two photoelastic overdenture models were fabricated in each anchorage system to compare with the palatal coverage extent of denture base, as a result we got eight models : Hader bar using clips(type 1), cantilevered Hader bar using clips(type 2), Hader bar using clip and ERA attachments(type 3), cantilevered milled-bar using swivel-latchs and frictional pins(type 4). Result: 1. In all experimental models, the highest stress was concentrated on the most distal implant supporting bone on loaded side. 2. In every experimental models with or without palatal coverage of denture base, maximum fringe orders on the distal ipsilateral implant supporting bone in an ascending order is as follows; type 3, type 1, type 4, and type 2. 3. Each implants showed compressive stresses in all experimental models with palatal coverage of denture base, but in the case of those without palatal coverage of denture base, tensile stresses were observed in the distal contralateral implant supporting bone. 4. In all anchorage system without palatal coverage of denture base, higher stresses were concentrated on the most distal implant supporting bone on loaded side. 5. The type of anchorage system affected in load transfer more than palatal coverage extent of the denture base. Conclusion: To the results mentioned above, in the case of patients with unfavorable biomechanical conditions such as not sufficient number of supporting implants, short length of the implant, and poor bone quality, selecting a resilient type attachment or minimizing the distal cantilevered bar is considered to be an appropriate method to prevent overloading on implants by reducing cantilever effect and gaining more support from the distal residual ridge.

• The Journal of Korean Academy of Prosthodontics
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• v.55 no.3
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• pp.292-299
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• 2017

Long-term alveolar bone resorption in edentulous patient causes difficulty in denture use. Applying an implant overdenture with 2 to 4 implants to edentulous patient is easily approachable. Moreover, it improves denture stability, support, and retention. Milled bar, the attachment used in implant overdenture, can be used to induce better stability and retention to the supporting structure than conventional bar. It has become convenient to use due to the development of CAD/CAM system which had allowed the simplification of dental techniques. In this case, application of conventional maxillary full denture and mandibular overdenture made of CAD/CAM milled bar with 4 implants showed satisfactory results in the patient who had used upper and lower full dentures for a long time.

• The Journal of Korean Academy of Prosthodontics
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• v.47 no.2
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• pp.240-246
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• 2009

Statement of problem: Insertion of endosseous implants in the atrophic maxilla is often complicated because of lack of supporting bone. Augmentation of the floor of the maxillary sinus with autogenous bone & bone substitute graft has been proven to be a reliable treatment modality, at least in the short term. The aim of this study is to evaluate the factors of implant survival rate associated with maxillary sinus lift with grafts. Material and methods: The sinus floor was augmented with bone grafts derived from modified Caldwell-luctechnique(71 subject, 93 sinus, 180 implants), the autogenous bone or autogenous+Bio-oss. Before implant installation the width and height of the alveolar crest were increased in the first stage procedure in 10 patients while in the other 61 patients augmentation and implant installation could be performed simultaneously width and height of the alveolar crest > 4 mm) or delayed installation. Results: In all case bone volume was sufficients for implant insertion. 14 of 180 inserted implants were lost during follow up and the healing period Patient received implant supported overdenture(5 patients) or fixed bridge(62 patients). Conclusion: Within the limit of the result of this study, we conclude that bone grafting of the floor of the maxillary sinus floor with bone for the insertion of implants might be a reliable treatment modality and the autogenous bone graft and delayed installation method might be the factors for good results.

• The Journal of Korean Academy of Prosthodontics
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• v.50 no.3
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• pp.156-161
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• 2012

Purpose: This study was conducted to obtain difference in fracture strength according to the diameter of one-body O-ring-type of mini implant fixture, to determine the resistance of mini implant to masticatory pressure, and to examine whether overdenture using O-ring type mini implant is clinically usable to maxillary and mandibular edentulous patients. Materials and methods: For this study, 13 mm long one body O-ring-type mini implants of different diameters (2.0 mm, 2.5 mm and 3.0 mm) (Dentis, Daegu, Korea) were prepared, 5 for each diameter. The sample was placed at $30^{\circ}$ from the horizontal surface on the universal testing machine, and off-axis loading was applied until permanent deformation occurred and the load was taken as maximum compressive strength. The mean value of the 5 samples was calculated, and the compressive strength of implant fixture was compared according to diameter. In addition, we prepared 3 samples for each diameter, and applied loading equal to 80%, 60% and 40% of the compressive strength until fracture occurred. Then, we measured the cycle number on fracture and analyzed fatigue fracture for each diameter. Additionally, we measured the cycle number on fracture that occurred when a load of 43 N, which is the average masticatory force of complete denture, was applied. The difference on compressive strength between each group was tested statistically using one-way ANOVA test. Results: Compressive strength according to the diameter of mini implant was $101.5{\pm}14.6N$, $149{\pm}6.1N$ and $276.0{\pm}13.4N$, respectively, for diameters 2.0 mm, 2.5 mm and 3.0 mm. In the results of fatigue fracture test at 43 N, fracture did not occur until $2{\times}10^6$ cycles at diameter 2.0 mm, and until $5{\times}10^6$ cycles at 2.5 mm and 3.0 mm. Conclusion: Compressive strength increased significantly with increasing diameter of mini implant. In the results of fatigue fracture test conducted under the average masticatory force of complete denture, fracture did not occur at any of the three diameters. All of the three diameters are usable for supporting overdenture in maxillary and mandibular edentulous patients, but considering that the highest masticatory force of complete denture is 157 N, caution should be used in case diameter 2.0 mm or 2.5 mm is used.