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 »  Home  »  Dental Implant 3  »  The Adaptation of Implant-Supported Superstructures to the Alveolar Crest: A Follow-Up of 49 Cases
The Adaptation of Implant-Supported Superstructures to the Alveolar Crest: A Follow-Up of 49 Cases
Introduction - Materials and methods.

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Stefan Ahren, DDS
Private Practice, Vänersborg, Sweden.

Karl-Erik Kahnberg, DDS, PhD
Department of Oral and Maxillofacial Surgery, Faculty of Odontology, Göteborg University, Göteborg, Sweden.

In all cases, implant treatments are intended to create the most favorable conditions for oral hygiene procedures. Fixture survival has been reported to be very successful, especially in the lower jaw. The importance of oral hygiene procedures to prevent the development of peri-implant inflammations has also been enunciated. However, taking into consideration phonetic problems and food impaction problems with implant superstructures that leave a considerable gap between the bridge and the alveolar crest, we have tried to construct the bridge with close adaptation to the alveolar crest in a series of patients. The risk of poor oral hygiene is obvious, but phonetic, esthetic, and functional aspects can be markedly improved. In the severely resorbed jaws, the design of the superstructure has to compensate for the considerable loss of alveolar bone. It is also important to make the tissue compensation as similar to the surrounding oral mucosa as possible. In the single tooth restoration, both oral surgeons and prosthodontists are eager to make the rehabilitating solution as esthetic as possible by means of deep positioning of the implant and short abutments. If the same concept is applied to the edentulous patients, the clinician could obtain a dentoalveolar substitute, which is a direct continuation of the maxilla or the mandible, with the use of esthetic abutments and close adaptation to the soft tissue. These procedures are done without augmentation surgery and transplant procedures (if there is enough bone for conventional implants). The main risks of implants that are kept below rigid bridge constructions are the difficulties associated with oral hygiene measures and possible marginal bone resorption that result from periodontal disease. However, if the marginal bone conditions, soft tissue conditions, and fixture survival are acceptable, then there are several benefits to improving esthetics, phonetics, and function with these types of prostheses. The objective of this paper is to present the outcomes of 49 consecutive edentulous cases in which a close adaptation of the superstructure has been made. The patients have been followed for up to six years.

A consecutive series of 49 patients received a total of 252 fixtures (Nobel Biocare AB, Göteborg, Sweden). There were 17 patients with edentulous mandibles, 20 patients with edentulous maxillas, nine partially edentulous cases, and three single-tooth implant cases. There were 21 women and 28 men in the patient group. The mean age of the men was 65.8 years, and the mean age of the women was 64.0 years. In the lower jaw, self-tapping MARK IIB fixtures (length, 10–18 mm) were used. Standard fixtures (length, 10_20 mm) were used in all cases in the upper jaw. The standard healing time was 4 months in the mandible and 6 months in the maxilla. Both mandibles and maxillas represented the categories 3 and 4 according to the Cawood classification19 of bone volume and bone quality. No surgical complications were noticed, and the healing was uneventful in all patients during both implantation and abutment connection. Estheticon (Nobel Biocare AB, Göteborg, Sweden) abutments (length, 1–2 mm) were used in all cases, enabling a close adaptation of the superstructure to the alveolar crest.
The prosthetic treatment started five to seven weeks after the procedure, enabling the gingival tissue to shrink as much as possible before initiating the prosthodontic procedure. In connection with impression taking and occlusal registration, the dental set-up construction was designed in collaboration between the dentist, the dental technician, and the patient. Photographic documentation was an extremely useful guide for the dental technician’s work. When the metal construction was tested in the patient, the adaptation against the alveolar process was carefully checked. Four weeks after the installation of the implant superstructure, the internal screws were further controlled and tightened if necessary (Figs. 1, 2, and 4).

Fig. 1. Design of the initial type of superstructure with space between the crest and the bridge to allow for cleaning procedures. Tightly adapted superstructure in the upper jaw.
Fig. 2. A closely adapted bridge construction in the upper jaw.
Fig. 3. The bridge has been removed annually to examine the gingival tissue.
Fig. 4. Adaptation of the superstructure to an irregularly formed alveolar crest in the upper jaw.

Design of the initial type of superstructure with space between the crest and the bridge to allow for cleaning procedures. Tightly adapted superstructure in the upper jaw

Radiographic examinations, including panoramic radiograph and intraoral radiographs, were performed before the procedure and after the abutment connection.
The intraoral radiographs were done with a periodic standardized reproducible intraoral technique by using an occlusal impression material. Annual examinations, consisting of the removal of the superstructure and the inspection of the periimplant soft tissues (Fig. 3), were performed. All patients received thorough oral hygiene instruction from a professional dental hygienist who informed them about the use of dental floss, intradental brushes, and wound rinse. The patients were also continually controlled by a dental hygienist every third month for oral hygiene procedures. The surgical procedures were without complications in all of the cases and were done according to a standard procedure with conventional implant surgery. Crestal incisions were used in most of the cases. Abutment connections were made with 1-mm to 2-mm Estheticon abutments.