Background

Placing implants in the esthetic zone remains challenging due to anatomical limitations and expectations for an immediate and visually pleasing restoration.^1,2 Narrow diameter implants are indicated in clinical situations with limited bone volume and/or limited interdental space, or sites with congenitally missing teeth. They are intended for single or multiple unit applications to rehabilitate the lateral incisors in the maxilla and/or lateral and central incisors in the mandible.

Aim

The aim of this five-year open, prospective, multi-center clinical study is to evaluate esthetic results, marginal bone loss, and overall survival and success rate of a narrow diameter implant after immediate provisionalization.

Material and methods

• The study included patients in need of implants for the replacement of maxillary lateral incisors or mandibular lateral and central incisors.
• Patients were treated with a 3.0 mm diameter implant (NobelActive, Nobel Biocare AB, Göteborg, Sweden) placed either in extraction or healed sites and immediately provisionalized with an acrylic crown within 24 hours.
• A minimum insertion torque of 35 Ncm without further rotation was required to be eligible for immediate loading.
• The evaluated outcomes included implant survival and success, as well as marginal bone levels and marginal bone remodeling. Standardized clinical and radiographic examinations were performed at implant insertion, and are ongoing at 6 months, one year, two years, three years, and five years post-implantation.
• Peri-implant soft tissue health parameters including papilla score, plaque accumulation, and bleeding index as well as the Pink Esthetic Score (PES) were evaluated at each follow-up visit.
• Implant survival was calculated based on a life-table analysis. Marginal bone remodeling and the PES results were evaluated using a paired Wilcoxon signed-rank test.

Results

• A total of 77 patients (49 women and 28 men) with an average age of 41 years (min. 18, max. 80 years) received 91 implants. 63 patients received a single implant and 14 patients with congenitally missing teeth received two implants.
• 59 implants were inserted in the maxilla and 32 in the mandible. 67 implants were placed in healed sites and 24 in fresh extraction sockets.
• The mean insertion torque was 38.9 ± 4.6 Ncm. All implants were judged stable at insertion and were immediately provisionalized.
• 71 patients with 82 implants completed the one-year follow-up visit.
• Three implants failed yielding the cumulative survival rate (CSR) of 96.7%. Cumulative success rate at implant level was equal to CSR.
• All three failures occurred within the first three months after implant insertion. In addition, two patients experienced accidental biting in the implant area and lost the implant or had it explanted. No implant fracture occurred.
• Marginal bone levels were -0.47 ± 1.11 mm at insertion (n = 85), -1.02 ± 0.96 mm at six months (n = 80) and -0.81 ± 0.82 mm at one year (n = 77).
• After initial bone remodeling from insertion to six months, bone gain was observed from six months to one year (both p < 0.05) (Table 1).
• The soft tissue parameters, including the papilla, plaque, and bleeding indices as well as the Pink Esthetic Score (PES) improved over the one-year follow-up. (Figures 1 & 2).

Clinical Case

A 20-year old female with aplasia in region 12 and 22 requested treatment with implant-based restorations. Due to limited interdental space two 3 mm narrow platform implants were placed. Both implants were immediately loaded with resin crowns with only one impression. Three months later the patient received the final all-ceramic crowns. The implants and the restorations continue to remain stable.