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Use of Narrow-Diameter Implants in Treatment of Severely Atrophic Maxillary Anterior Region With Implant-Supported Fixed Restorations
Stuart J. Froum, DDS; Sang-Choon Cho, DDS; Salvatore Florio, DDS; and Craig M. Misch, DDS, MDS
Abstract: The edentulous anterior atrophic maxilla represents a challenge for the surgeon and restorative dentist. Soft- and hard-tissue augmentation procedures are often required prior to, or simultaneously with, implant placement. A well-planned treatment protocol, patient compliance, and collaboration between the treating clinicians and the laboratory are requirements in achieving predictable long-term outcomes that satisfy patient expectations. Avoiding transmucosal loading and movement of the graft during the healing phase are crucial factors in achieving lasting success. In this case report, a fixed provisional restoration supported by four immediately loaded narrow-diameter implants (NDIs) was used to enable function during healing and protect the grafted site. Two of the NDIs, along with three conventional-diameter implants, were subsequently used to support the final restoration. NDIs with diameters of less than 3 mm can achieve excellent long-term osseointegration and may be used together with conventional implants for definitive prosthodontic treatment as demonstrated by the 11-year follow-up reported in this case.
Placing implants in prosthetically ideal positions in the atrophic maxilla is challenging and often requires soft- and hard-tissue augmentation procedures prior to, or simultaneously with, implant placement.1,2 Considering the complexity and treatment time, correct sequential planning is crucial to achieving predictable long-term results while satisfying the patient’s expectations for function and esthetics. The use of narrow-diameter implants (NDIs) presents an invaluable modality for restoring an edentulous atrophic maxillary area in the provisionalization, augmentation, and final restorative phases of therapy.
All NDIs in this case report were category 1, according to the Klein classification, and are defined as implants with a less-than-3-mm diameter.3 These implants have been used to support removable and fixed dental prostheses since they were introduced in 1994.4 Among the articles that have been published on NDIs reporting survival rates comparable with conventional implants, Klein et al,3 in a systematic review of the literature, reported NDI survival rates between 90.9% and 100%.
The original function of NDIs was to support fixed interim prostheses during the osseointegration phase of conventional implants to avoid transmucosal loading that could compromise the final outcome. Following this initial healing period, the NDIs would be removed. It was later reported that the removal of these implants could be difficult because of the various degrees of integration they achieved.5 Froum et al6 confirmed this finding in a histologic study with machined-surface transitional implants. They analyzed the percentage of bone-to-implant contact (BIC) for NDIs after an average functioning period of 10.8 months. The values obtained were similar to the percentage of BIC of conventional turned, machined-surface implants. The results indicated that NDIs were able to achieve the same degrees of integration as implants with conventional diameters.6
In 2004 the US Food and Drug Administration approved the use of NDIs in the human jawbone for long-term use.7 Several authors have showed successful results when NDIs were used to support definitive prostheses.8-12 Furthermore, in a 2013 systematic review, Bidra and Almas13 reported a 94.7% survival rate of NDIs (diameter <3 mm) when used exclusively for definitive prosthodontics treatment. NDIs have been successfully used to support both transitional and fixed prostheses, thus providing clinicians with a simplified treatment option in areas of limited alveolar bone dimensions. In addition, they typically cost less than conventional implants and, in many cases, are able to be placed with a flapless procedure, which decreases patient postsurgical discomfort and morbidity.
This case report presents an 11-year follow-up of a patient in whom NDIs were used to support both the provisional and final restorations. The planning and sequencing of the procedures, including provisionalization, ridge augmentation, and final NDIs-conventional implants–supported restorations, will be discussed to illustrate the use of NDIs in the various phases of treatment.
In 2004, a 30-year-old male was referred to the Ashman Department of Periodontology and Implant Dentistry of New York University College of Dentistry. The patient was a nonsmoker with an unremarkable medical history. His chief complaint was discomfort with his existing six-unit removable partial denture (Nos. 7 through 12), which he said he “could not tolerate” (Figure 1). He desired a fixed prosthesis. Two years earlier, severe trauma to the anterior maxilla had caused the loss of teeth Nos. 7 through 12 and the subsequent loss of supporting bone and soft tissues (Figure 2 and Figure 3). A computerized tomography scan revealed a deficient volume of buccolingual crestal bone and the need for a bone regeneration procedure prior to implant placement.
The treatment plan was to first provide the patient with a fixed provisional restoration that would afford function and protect the planned grafted site. Four NDIs were planned to support an acrylic provisional prosthesis prior to the augmentation procedure and during the healing period. This was to be followed by replacement of two of the NDIs with three conventional-diameter implants to support the definitive prosthesis.