Site Selection, Evaluation and Imaging for Dental Implants

Muralidhar Mupparapu

Historical Perspectives

Indications for Dental Implants

Patient Management with Dental Implants

Identification of the Implant Site

Selection of the Implant Site

Imaging of the Implant Site

Dental implants are prosthetic devices implanted into the oral tissues either beneath the mucoperiosteal layer or in the bone to provide retention and support for the fixed or removable prosthesis. Although fabrication of dental implants dates back to many decades, the advent of dental root form implants (DRFIs) have paved way for universal acceptance of implants as replacement for lost teeth. The dental implant restorations not only enhance the esthetics for the patients, but also improve the oral function for speech and mastication. Hence, the dental root form implants (Figure 1) gained immense popularity among the dental practitioners as well as the patients in the dental profession. Nothing is more important in the dental implantology than the precise evaluation and placement of the implant structures in the maxilla and mandible. In order to do this effectively, one needs to precisely understand the surgical anatomy of the maxillofacial region and the anatomical variations that might be encountered. Secondly, they need to grasp the biomechanics of the dental implant material. Fortunately, now, the science behind the dental implantology is strong, backed with research and evidencebased trials. The fruits of the decades of clinical trials using various dental implant materials along with numerous loading protocols have refined the predictability of dental implants for the maxillofacial region.

Figure 1 Diagrammatic representation of the typical implant fixture and the crown properly placed within the maxillary alveolus

Historical Perspectives

The treatment options that are available for replacement of single or multiple teeth in the oral cavity are removable partial denture (RPD), fixed partial denture (FPD) and implant prosthesis (IP). The RPDs which were not helpful in the maintenance of existing bone, compromise the esthetic result, need more bulk for cross-arch stabilization, easily trap food debris and plaque, and interfere with the speech and function. Similarly, the FPDs especially promote caries of the abutment teeth but if not well fabricated, lead to plaque retention in the pontic increasing periodontal risk, involve damage to adjacent teeth, fracturing of the porcelain, and have esthetic concerns for the anterior regions. The FPDs are contraindicated when there is poor abutment support, inadequate hard and soft tissues in the esthetic regions and in young patients with large pulp horns. The dental implants would be an ideal alternative for replacement of teeth.

Historically, there were three distinct forms of dental implants, namely, the subperiosteal (epiosteal), the transosseous (staple bone or transmandibular) and the endosteal (blade or plate, ramus-frame and root form) types. Dental practitioners should be familiar with the radiographic appearances of older dental implant systems although many of them are rarely used after the advent of the dental root form implants.

Subperiosteal implants are metallic meshes that are custom-built to fit over the alveolar processes and are located underneath the periosteum (Mupparapu and Beideman, 2000). Direct bone impressions via surgery would lead to the fabrication of mesh in a laboratory that fits under the mucoperiosteum (Figure 2). The framework normally rests on the mandible with no penetration into the bone. Two surgeries were involved in the fabrication of these implants. First surgery is for the impression and the second surgery is for the placement of the mesh. The first subperiosteal dental implant in the world was placed by George Dahl in Sweden. The first American subperiosteal implants were developed in 1947. Gershkoff and Goldberg placed the first subperiosteal complete denture implant manufactured with Vitallium (Moore and Hansen, 2004). Dr Leonard Linkow of New York made significant changes to the original design by incorporating fenestrations into the buccal peripheral struts which made it possible for the mucoperiosteum to reattach the bone in between these fenestrations. He also holds 35 patents on various designs of subperiosteal and oral implants. Multiple metallic posts extend from the mesh into the oral cavity crossing the mucoperiosteal barrier to support the prosthesis. Mandibular subperiosteal implants have been shown to be successful in many clinical studies and some of the implants reviewed were present in the mouth for more than 10 years. The success rate for these implants varied in many studies with higher success rate for 10-year periods and lower success rates for longer periods (Moore and Hansen, 2004). Computed tomography (CT) scans were also used to allow CAD/CAM fabrication of the framework, eliminating the need for impressions via surgery. Subperiosteal implants are no longer preferred after the success of endosteal implants although one can occasionally see them in clinical practice with varying degrees of presentation (Beddis et al, 2012).