Many randomized controlled clinical trials have been published about dental implants. They have demonstrated long-term success in the rehabilitation of edentulous patients [1, 2] as well as patients with single or multiple teeth replacements [3, 4].

While this type of trials have an indispensable place in establishing a new product or a new operation technique regarding safety and efficacy, the results are viewed with a degree of caution by doctors in their daily practice because of the inherent weaknesses of controlled studies, such as very strict inclusion criteria, extremely motivated study patients, and extended treatment time. Hence, there is a growing interest to investigate the survival rates and adverse events (AE) encountered in daily practice. Systematic longitudinal studies reflecting the regular use of implants treatment were published to supplement the systematic assessment of implants [5]. Besides many retrospective studies [5,6,7], few observational clinical trials with a large number of patients are available [8,9,10,11].

While observational clinical trials are of high interest for daily practice, one drawback is their high dropout rate over the observed period in comparison to randomized controlled clinical trials, which may bias the results: a drop-out rate of 35% to nearly 50% has been published [8, 12]. The participating patients seem less willing to accept follow-up visits [13, 14] than in controlled randomized trials. To avoid any drop-out bias, it is therefore very important for treating doctors and their dental hygiene specialists to motivate patients to attend follow-up appointments.

The investigation of patient-related outcome measures (PROMs) have become important due to the fact, that clinical success has to be in line with the satisfaction of the patients with the restoration. The degree of individual patient satisfaction is the result of psychological and physiological factors. But the choice of which PROMs to use should be restricted to those most appropriate for the study question and at a minimum, these data should be gathered at two time points: at baseline and at a designated point post-treatment. Ideally, multiple assessments are desirable to discriminate short- versus long-term treatment effects [15,16,17,18].