Today, replacing missing teeth with dental implants is considered the standard treatment for single-tooth spaces. Numerous clinical studies have shown that single-tooth implant treatment is predictable and has a high success rate even after long-term follow-up.
Starting in the mid-1960s, dental implants were initially used to support restorations in fully edentulous patients and subsequently also in partially edentulous patients. Nearly 20 years later, single implants were introduced as a treatment option for patients with single-tooth spaces. However, single-implant treatment presents challenges related to aesthetic and mechanical issues, such as the need to address abutment screw rotation. The restorative components of implants, i.e., abutments and crowns, have gone through several stages of development with a focus on design and improvements in the materials used.
Currently, many patients worldwide are treated with single-tooth implants. Common causes of single-tooth spaces include trauma and dysplasia, which suggests that many of these patients are young. Although several studies on single-tooth implants have reported 5-10 years of follow-up, it is critical to understand complications that may arise over longer periods of time. This is particularly important for young patients, who are expected to retain their implants for a long period of time.
Per-Ingvar Brånemark and colleagues recognized long ago the importance of documenting and clinically following up the first patients treated with implants to confirm the efficacy of treatment. Therefore, a 3-year prospective study was conducted at the Brånemark Clinic in Gothenburg on the first 16 patients worldwide treated with Brånemark single implants. Now, almost 40 years later, almost all of the patients have been re-evaluated, providing us with data on the long-term outcomes of these treatments.
The aim of this study was to follow up on first-time patients who had undergone single-tooth implant treatment 38 to 40 years ago and to report on implant survival and complication rates.
This study included a group of consecutive patients who were treated with a single crown supported by a maxillary or mandibular implant at a single clinic (the Brånemark Clinic, Public Dental Health Service, Gothenburg, Sweden). This group of patients has been described in a previous publication [ 9 ]. Briefly, the study examined 16 patients (8 females, 8 males) aged between 14 and 48 years who were treated with single-tooth implants in their permanent teeth. A total of 23 Brånemark system implants (Nobel Biocare AB, Gothenburg, Sweden) with turned surfaces were placed, of which 5 were conical.
The study population included patients with partial edentulism, dental trauma, and tooth loss due to apical or periodontal disease. Implants were placed between December 1982 and November 1985, and healing abutments were attached between June 1983 and May 1986. Different superstructure designs were used, including hexagonal interfaces and conical abutment cylinders with telescopic superstructures, with the goal of enhancing stability and esthetics.
In this study, the same patients were invited to the clinic for follow-up, except for deceased patients. Patients were included if they agreed to participate in the study. Follow-up examinations were performed by two prosthodontists in the same clinic. Data recorded during follow-up included clinical assessment of technical and biological complications, radiological assessment, intraoral scans, and clinical photography.
All data collection procedures were performed in accordance with the 2013 amendment to the 1964 Declaration of Helsinki for biomedical research involving human subjects. This study was approved by the Swedish Ethical Review Board (Dnr. 2023-00888-01). Informed consent was obtained from each participant. This study was conducted in accordance with the STROBE statement guidelines for observational studies.
The primary objective of this study was to evaluate implant survival, and secondary objectives were to assess long-term implant safety and performance by evaluating the frequency of biological and technical complications and marginal bone level (MBL) and its changes.
Baseline radiographs were taken at the time of prosthesis installation, and paired radiographs were obtained at follow-up 38–40 years after surgery. All MBL measurements were performed by two experienced prosthodontists using Planmeca Romexis 3D imaging software (Planmeca Oy, Helsinki, Finland). These measurements were defined as the distance from the reference point (implant platform) to the level of the most apical bone. MBL was recorded both mesially and distally and was expressed as the mean value calculated as (mesial + distal)/2. Negative MBL values indicated a bone level below the reference point, whereas positive values indicated a bone level above the reference point. Marginal bone level change (MBLC) was calculated using paired radiographs, with negative values indicating bone loss.
All 16 patients treated and included in the original study were followed up and examined, except for three patients. One patient with two implants was excluded from the 3-year FUP because one implant failed 30 months after surgery and the second implant was restored. Of the remaining 15 patients, one had died and one was excluded because the implant was connected to a full-mouth implant-supported prosthesis.
All but one of the 13 included patients with 18 implants were examined by two experienced prosthodontists. One female patient was unable to come to the clinic, and the clinical examination was performed by the patient’s general dentist. The main characteristics of the 13 included patients (54% female) who underwent 18 implants are shown in Table 1 . The mean age at surgery was 23.0 ± 5.35 years (range: 14–34 years) and the mean age at follow-up was 61.9 ± 5.51 years (range: 53–73 years) (mean follow-up: 38.9 ± 0.8 years; range: 37.9–40.5 years).
The causes of edentulism in the patients studied were trauma (54%) and hypoplasia (46%). Sixteen of the 18 implants (89%) were placed in the maxilla, with the majority of implants being used to restore maxillary incisors (72%). All implants were placed according to a two-stage surgical protocol with delayed loading, and none of the implants received bone grafting before placement. The second surgery was performed 7.0 ± 2.1 months (range: 5.0–11.2 months) after implantation, and loading occurred 3.0 ± 2.4 months (range: 0.0–9.7 months) after the second surgery or 10.1 ± 3.1 months (range: 5.2–15.8 months) after the first surgery.
Single-tooth implant survival is high, and in this small group of patients, the long-term prognosis of the implant is good. However, the likelihood of replacing an implant-supported crown increases over time.
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