evaluation of radiographs. A surgical sterfl is also useful when the fixtures are implanted. The optimal position from a prosthetic point of view can be visualized. 121. What are the treatment modalities for a totally edentulous jaw? • Overdenture supported by implants • Fixed “high-water” prosthesis • Conventional fixed crown and bridges using implants 122. Describe the concept of implant-supported overdenture. An implant-supported overdenture is supported both by the implants and the edentulous ridge covered by resilient mucosa. The surgeon must accommodate for this resiliency in the attachments of the implants to permit small rotational movements. 123. What are the indications for the overdenture treatment? This treatment modality is a comparatively simple procedure with relatively low cost and meets the demands imposed by many patients. The most common indications are: • Retention of denture • Compromised hygiene skills (i.e., reduced dexterity, as with elderly people) • Interarch positions (difficulty ir placing proper interdental relationships with fixed restorations) • Phonetics/esthetics (especially in the maxilla, an overdenture may improve esthetic and/or phonetic results compared with an implant-supported fixed prosthesis). 124. How many implants are necessary to support the overdenture? The number of implants ranges from a minimum of two fixtures to an ideal of four. It is also important to consider the loading forces on the implant. 125. What is the effect of loading forces on implant-supported overdentures? The loading forces are important to fixture survival because overloading can lead to implant failure. To reduce improper loading conditions, the following points should be considered: 1. The implants should be positioned as perpendicular to the occlusal plane as possible. 2. Shear loads and bending movements are reduced if leverages are shortened by using short abutments and low attachments. 3. Resilient attachments reduce bending movements. Occlusal forces are shared between fixtures and overdenture-bearing mucosa. 4. Extension bars represent a potential risk of overloading.
Dental Secrets SE By Stephen T.Sonis, D.M.D., D.M.Sc. Converted to e-book by sari_barazi@hotmail.com
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