The implant survival rate of 100 % after 12 months is also in line with the results from previous studies with chemically modified SLA implants in various situations, including 100 % survival in early loading of mandibular overdentures [55], 100 % survival in single-tooth applications in the anterior maxilla [56], 96.8 % with maxillary sinus floor augmentation [57], and 98 and 97 % with immediate and early loading in posterior jaws [36], respectively. Excellent implant survival rates with early loading have also been achieved over longer time periods; for example, with chemically modified implants loaded after 21 days, 100 % survival and success were observed over 3 years in the posterior mandible [35].

Implant survival rates in the current study also compare well with survival and success rates obtained for SLA implants over an equivalent period of time. For example, Al-Nawas and colleagues achieved implant survival rates of 96.9 and 96.4 % for SLA implants loaded after 4 and 12 weeks, respectively [58], while Fischer and Stenberg achieved 100 % survival with SLA implants supporting early-loaded maxillary full-arch prostheses [59]. It should be remembered, however, that the patients enrolled in the current study were treated by highly experienced implant surgeons and were subjected to strict inclusion and exclusion criteria, although high survival rates with these implants have also been found in daily dental practice [60, 61].

The study was performed because early loading protocols for dental implants in Japan are still relatively uncommon, even though early loading of dental implants has elsewhere been demonstrated to be a viable treatment option to restore esthetics and function to the patient in a timely manner [12, 15, 16, 45] and has shown advantages in terms of preservation of hard and soft tissues [14], as well as providing psychological benefits for the patient. Few clinical trials on early loading have been conducted in the Japanese population, and the authors speculate that this may indicate a more conservative approach to implant rehabilitation among Japanese dentists and implant surgeons. However, a recent prospective, multicenter, non-interventional analysis of Straumann bone level implants with the chemically modified SLA surface in daily dental practice indicated that conventional loading is still very much the norm in most countries. In this analysis, the authors found that of 1113 implants, 68.6 % were loaded with a conventional loading protocol, while early loading was used in only 12.4 % of cases [61]. Conventional loading is therefore still very much favored, despite evidence that there are no clinically important differences between the different loading protocols regarding implant or prosthesis failure [12, 62] or crestal bone loss [12, 15]. It has been noted, however, that not all clinicians can achieve optimum results with early loading and that high primary implant stability may be a requirement for a successful procedure [62].