الفهرس 
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Abstract
The aim of this study was to evaluate bone level changes in single maxillary implant-retained overdenture cases. Twenty-one patients were selected from the Prosthodontic Department, Faculty of Dentistry Alexandria University. All patients had edentulous maxilla opposed by natural mandibular teeth. Panoramic x-rays were done to all patients.
Occlussal plane alignment of the mandibular teeth was corrected; crown and bridge restorations were used in some cases. All patients received upper conventional denture.
The patients were divided into 3 groups. Each group consisted of 7 patients. Group (1) was treated with upper conventional denture. Group (2) was treated with overdenrture supported by 2 free standing implants with ball/o- ring attachment and group (3) was treated by overdenture supported with a bar/clip attachment. ,
Two implants were inserted in the canine region in groups (2 &3) to be away from any anatomical structures such as nasal floor or the max,illary sinus. The number of implants is thought to be enough due to the fact that the upper overdenture is supported by both the implants and the upper edentulous ridge.
The maxillary implant-supported overdenture retained by 2 implants has many advantages; it improves mastication due to increased retention and stability, it preserves the alveolar bone in the premaxilla and posterior ridge area. It dramatically improves the esthetics as the labial flange gives lip support also it improves phonetics better than the fixed denture as it close any airway spaces. And at the same time economically acceptable by the patient (135, 152,153,154).
Clinical and radiographic evaluation started from the time of loading and continued at 3 l110nths interval. The results were tabulated and statistically analyzed, it revealed that the least bone resorption was found in the bar group, the clinical evaluation revealed that it is not only dependant on the type of restoration, but it varies due to the oral hygiene of the patients.