Implant success and survival rates in daily dental practice: 5-year results of a non-interventional study using CAMLOG SCREW-LINE implants with or without platform-switching abutments

Success and survival rates of endosseous implants are well-documented in a number of controlled clinical trials and systematic reviews [1–3]. Generally, controlled trials evaluate endosseous implants in specific clinical situations; thus, the patient population is subjected to rigorous inclusion criteria and follow-up. Accordingly, controlled clinical trials do not reflect the real-life situation in private practice. Numerous factors including experienced clinicians, specialized clinics, restricted inclusion and exclusion criteria, specific indications, and increased time spent during follow-up, may affect or even bias the results, outcomes, or reported implant success and survival rates [4]. Consequently, there is an increasing trend in assimilating and reporting real-life data [4] allowing for the evaluation and assessment of dental implants in daily practice. An observational, non-interventional study in a non-homogeneous population better reflects daily practice than a controlled clinical study.

Various studies have reported on success and survival of endosseous implants in private practice settings. In a 5-year prospective observational study on 590 patients, Cochran et al. [5] evaluated 990 implants placed under routine private practice conditions. Very high cumulative survival and success rates were achieved after 3 years (> 99%) and 5 years (97%) of loading. These results were found to be comparable with the rates of survival and success of the same sand-blasted, large grit, acid-etched (SLA) implants achieved in a controlled, prospective, multicenter clinical study (Cochran et al. 2002 as cited in [5]).

Nevertheless, observational studies performed in private practice are not without their flaws; studies have shown that patients may be poorly motivated to attend follow-up appointments [6, 7], and results from various studies imply that, in non-controlled clinical settings, follow-up attendance may drop when patient satisfaction is high [6–8]. In contrast, regular follow-up appointment attendance is integral to the study design in controlled clinical trials; therefore, the patient’s obligated attendance to follow-up appointments may mask their natural behavior when satisfied.

In the present study, CAMLOG SCREW-LINE implants with the Promote plus surface (sandblasted and acid-etched surface) were used. These implants in combination with platform-matching abutments have been shown to have high long-term success rates ranging from 97.8 to 100% at 5-year to 10-year follow-up [9–13]. They can be restored with either platform-matching or platform-switching abutments with the difference that platform-switching abutments have a narrower diameter than the implant, leading to an implant-abutment mismatch. The effects of platform switching on hard tissue outcomes are well-studied, with there being a tendency to better outcomes with respect to crestal bone loss with platform switching [14–23]. Regarding the CAMLOG SCREW-LINE implants, the effect of platform switching and platform matching was evaluated in a randomized controlled clinical trial (RCT) [21, 23]. At 1-year follow-up, implant success rates were 97.3% and 100%, and at 3 years, implant survival was 97.3% and 97.1%, for platform-switching and platform-matching implants respectively. Platform-switching implants showed a positive effect on marginal bone loss already at 1-year follow-up, and significantly less marginal bone loss was reported with the platform-switching versus platform-matching technique at 3 years (0.28 ± 0.56 mm vs. 0.68 ± 0.64, respectively; p = 0.002).

To understand the performance of the CAMLOG SCREW-LINE implants used with platform-switching and platform-matching abutments outside of a controlled clinical environment, we conducted a prospective, non-interventional study in private practice. The primary objective was to provide data for a life table analysis on the performance of the implants in private practice, to show the probability of survival and success of the dental implants after a follow-up time of 5 years post-loading. Secondary objectives were to evaluate patient satisfaction through the assessment of appearance, ability to chew, ability to taste, comfort, general satisfaction, and fit. The outcomes were also reported for platform-switching and platform-matching subgroups.

This large, multicenter study provides real-life long-term data on 285 implants placed in 196 patients. The results show that the placement of CAMLOG SCREW-LINE implants with platform-matching or platform-switching abutments results in high survival and success in the long term. The overall success rate for implants was 97.1% at 5-year post-loading, and 97.4% and 96.2% for implants with platform-switching and platform-matching abutments, respectively, according to Albrektsson et al. [30]; the overall survival rate was 98.6%. For comparability to other studies, the success rates were assessed post hoc according to Buser et al. [29], revealing a 5-year overall success rate of 98.0%, and 100% and 97.4% for implants with platform-matching and platform-switching abutments, respectively.

These results compare positively with the results achieved for the CAMLOG SCREW-LINE implants in an RCT [23]. Here, the 3-year success rates—according to Buser et al. [29]—were 97.3% for platform-switching and 97.1% for platform-matching implants. In contrast, the present study achieved better 3-year success rates—according to Buser et al. [29]—for both platform-matching (100%) and platform-switching (99.4%) implants. Other private practice studies achieved similar results to our study, with success rates at 3 years of 93.5% for SLActive implants [4] and 99.12% and 97.58% at 3 and 5 years, respectively, for comparable SLA surface implants [5]. These studies [4, 5] also applied the success criteria, according to Buser et al. [29], namely absence of pain, infection, neuropathies or paresthesia, peri-implant infection with suppuration, mobility, and continuous radiolucency around the implant. Slight differences in success rates are seen with the two criteria [29, 30]. In our study, the success rates are lower at 5-year follow-up, according to Albrektsson et al., because bone level changes were measured to fulfill the first criterion (< 0.2 mm bone loss annually after the first year of loading). At 3-year follow-up, bone loss was noted in one patient (reclassified as peri-implantitis at the 4-year follow-up) and an important bone loss (due to poor oral hygiene and bruxism; two implants) in a patient with psychosocial issues who could not be treated during the study. Such a patient would not have been included in an RCT. Consequently, three implants were lost based on the bone loss criterion. Being able to measure bone level changes is also dependent on the availability of evaluable radiographs. In our study, these were taken as per standard clinical protocol using the available equipment, which may differ to that available in a university clinic, a setting commonly found in controlled clinical studies. Thus, some radiographs were not digitized and were difficult to read. Also, if the protocol does not stipulate radiography, then the natural behaviors of patients in private practice are revealed. Some patients refused radiographs, other patients were followed up by referring dentists, and radiographs were not exchanged. Additionally, if radiographs are routinely acquired, the clinician is still reliant on follow-up attendance. Accordingly, the success rates measured in the present study should be assessed collectively. Other studies not assessing bone level changes may report higher success rates than those achieved if bone level changes were evaluated [4, 5].

Other factors need to be considered when reporting success [32]. Papaspyridakos et al. reported a relationship between the number of success criteria and the success rate: the higher the number of success criteria, the lower the reported success rate [32]. Also, the common criterion of bone loss being < 2.0 mm during the first year of function, followed by < 0.2 mm annually thereafter, may no longer be suitable, particularly with new implant systems, such as platform-switching implants, which lead to minimal crestal bone remodeling (Prosper et al. and Trammell et al. cited in [32]). Over the 5-year study period, we report < 2.0 mm bone level change for all implants, 0.1–0.5 mm for 40%, and no bone loss or bone gain for 38% of all implants. Additionally, bone loss was 0.32 ± 0.66 mm and 0.13 ± 0.29 mm for the platform-switching and platform-matching subgroups. Of note, in this study, the platform-matching and platform-switching groups were very unbalanced (67 vs. 206 implants) because the decision to choose abutment type was the clinician’s choice according to the clinical situation. Furthermore, very few radiographs were available for the platform-matching subgroup; thus, differences between the two subgroups are not conclusive. Nevertheless, the minimal crestal bone loss of 0.32 mm observed for platform-switching implants is comparable with the data reported in other studies on platform-switching implants [17, 23]. The bone gain of 0.12 ± 0.42 mm at 1-year follow-up [17] and of 0.16 ± 0.53 mm at 3 years follow-up [23] have been reported. In these studies, the outer geometry of the implant was comparable; however, Rocha et al. [23] used implants of the same kind while Moergel et al. [17] used implants with a conical connection.

The importance of the vertical soft tissue thickness has recently been reported [33, 34]. Platform-switching implants placed in thick tissues led to the preservation of the crestal bone level, while this was not observed in thin mucosal tissues. These studies were not yet published in the planning phase and initiation of the present study. Accordingly, pocket probing depth measurements were performed rather than vertical soft tissue thickness. These measurements may be biased; it is thought that the probe may stop at the horizontal shift instead of the pocket depth, yet, to our knowledge, there is no reference supporting this. In daily practice, probing was sometimes not performed if the implants showed no pathological findings. On the one hand, the variety of bone level changes in this study may be explained by different vertical soft tissue thicknesses, but cannot be validated due to these missing data. On the other hand, there are multiple confounding factors influencing the change in bone level, such as the size of the platform (mismatch), occlusal loading, and the microgap.

Additional to the standard success criteria, patient-reported outcomes are important factors when evaluating an implant system [32]. In our study, if the patient was satisfied, no further radiographs were taken, and the implant was deemed successful. Furthermore, in some success criteria, overall patient satisfaction should be good or excellent for the treatment to be successful (Levi et al. cited in Papaspyridakos et al. [32]). Our study reveals an exceptionally high level of patient satisfaction. The majority of patients reported excellent outcomes for all measured categories at each time point throughout the study, with most remaining patients reporting good outcomes (Fig. 4). No patient reported a poor outcome, and a maximum of three patients at any given time reported fair outcomes. The parameters assessed by patients are closely related to soft tissue outcomes, which reflect oral hygiene and soft tissue health. The soft tissue parameters assessed in our study were MPI, SBI, PPD, and Jemt papilla score. For MPI, a statistically significant increase was observed from loading to the 5-year follow-up; however, the MPI at 5-year follow-up was, at 0.38 ± 0.52, still very low, with 0 equaling no detection of plaque and 1 equaling plaque only detectable after running a probe across the smooth marginal surface of the implant [27]. Similarly, the SBI remained very low throughout the study, despite a significant increase from loading to 5-year follow-up. At 5-year follow-up, the overall SBI was 0.32 ± 0.49, reflective of no bleeding given that 0 equals no bleeding and 1 equals isolated bleeding spots visible [27]. The PPD initially decreased within the first 6 months from which point it significantly increased to 2.34 ± 1.18 mm at 5-year follow-up. Nevertheless, the measured mean PPD still reflects the norm for conventionally placed implants, which at 2–4 mm is indicative of healthy tissues [35]. The same trend was observed for the Jemt papilla score [28], which significantly increased from loading to 5-year follow-up (2.14 ± 0.95). The ideal papilla score of 3 [28]corresponds to the optimal soft tissue contours; thus, the scores achieved in our study are close to the ideal. Although we observed some significant differences in these parameters between the platform-switching and platform-matching subgroups at 5 years, these are not clinically significant.

Our study should be particularly noted for its ability to recall patients for follow-up appointments. Patient attendance at follow-up appointments in trials performed in private practice can be troublesome [4, 6–8], and the inability to obtain full data from all patients at the later stages of a study may limit the interpretation of the final results. We obtained data for the 70% of patients completing the study at 5 years; this minimizes the limitations in the interpretation of results seen in comparable studies [5–8]. Although this study was performed in private practice, the investigators are very experienced in implantology and of good standing and understand the importance of follow-up and maintenance of good oral health. We observed a maximum of only five patients with poor oral hygiene at any given time (data not shown); additionally, the three late implant failures were in two patients with peri-implantitis or poor hygiene. The appearance of poorer oral hygiene later in the study also appears to correspond with the drop in follow-up attendance, which again supports the importance of follow-up. All other complications could be resolved and were not persisting. Furthermore, patients selected for inclusion in this study were optimal candidates for dental implants. Though the inclusion criteria predestinate the patient selection to some extent, the clinician’s expertise likely influences selection of a “good” patient. The patients included in our study had good overall health; American Society of Anesthesiologists (ASA) scores of 1 were observed for 85.6% of patients, and 74% of patients had never smoked.

A limitation of this study was the imbalance in the use of platform-matching and platform-switching abutments. Platform-switching abutments are relatively new, and in practice, the “newer” method (platform switching) was likely chosen over the conventional method. Platform-switching implants have been shown to have better outcomes with regards to bone level changes, but overall patient satisfaction does not differ between the two types [23], also supported by the results of our study. Another limitation may be the non-homogeneous study population. There were no exclusion criteria apart from the standard contraindications for an implant treatment, and the patients descend from the standard pool of private practices. Nevertheless, the success and survival rates were very high and were comparable with clinical data obtained in well-controlled clinical trials with multiple inclusion and exclusion criteria.

Within the limitations of this study, we conclude that the CAMLOG SCREW-LINE implants placed with both platform-matching and platform-switching abutments in patients in a private practice setting seem to achieve clinical outcomes comparable with those achieved in controlled clinical trials. The crestal bone changes over a 5-year period were mainly limited to < 1 mm and could be interpreted as proper peri-implant tissue stability. We also draw attention to the importance of patient education and regular follow-up on clinical outcomes. The patients in our study were highly satisfied with their implants, soft tissue parameters were excellent, and bone level changes were minimal, leading to good overall success and survival of the implants.