Daniele Botticelli Niklaus P. Lang Dynamics of osseointegration in various human and animal models - a comparative analysis Authors’ affiliations: Daniele Botticelli, ARDEC Academy, Ariminum Odontologica, Rimini, Italy POI - Programa Odontol ogico Internacional, Cartagena de Indias, Colombia Niklaus P. Lang, Center for Dental Medicine, University of Zurich, Zurich, Switzerland University of Bern, Bern, Switzerland Corresponding author: Dott. Daniele Botticelli Centro Hist orico, Av. Venezuela Edificio City Bank, Piso 5, Oficina 5G 130001-Cartagena de Indias Colombia Tel\Fax: 0057/5/6468359 e-mail: daniele.botticelli@gmail.com Key words: animal studies, histology, human studies Abstract Objective: To investigate the sequential events of osseointegration in various model situations. Material and methods: A series of eight recent sequential studies on the early phases of osseointegration performed in various species analyzing new bone apposition and parent bone resorption at the implant surfaces have been studied. One human, six dog and one rabbit studies were analyzed for old and new bone percentages, assessed at least at 4 periods of the early osseointegration. Data on new and old parent bone in contact with the implant surfaces were collected. The interception point of the two proportions of new and old bone was calculated in terms of osseointegration (y; %) and period of the interceptions (x; days). Results: It has been shown that the interception point of old and new bone proportions was strongly influenced by the choice of the model adopted (human, dog, rabbit), by the density of the surrounding bone (cortical, spongy, trabecular) and by the implant geometry. Implant surface configuration, time of implantation and load influenced the interception point to a lesser degree. The fastest rate of osseointegration was observed in the rabbit model followed by the dog model. The slowest osseointegration rate was seen in humans. Osseointegration was documented best in spongiosa bone when compared to cortical bone. The moderately rough surfaces gave rise to faster osseointegration than did the turned implant surfaces. Conclusions: The interception points may provide information on efficacy of early osseointegration. The slope of the line (m) is related to the efficacy of bone appositions. The sequential processes of osseointegration involve both bone resorption and bone apposi- tion, as described histologically in human (Bosshardt et al. 2011; Lang et al. 2011) and animal studies (Berglundh et al. 2003; Abra- hamsson et al. 2004; Rossi et al. 2014; Favero et al. 2016a, 2016b; Mainetti et al. 2015, 2016). An accurate illustration of these processes was first reported in a dog study (Berglundh et al. 2003; Abrahamsson et al. 2004). In that experiment, a trough was prepared within the threads of solid screw implants. Thus, after implant installation, a chamber was obtained, delineated by the trough walls and the parent bone. The sequential events that occurred within the chamber were studied at different time periods, between 2h and 12 weeks. Implants with two different sur- face configurations, SLA (S a 2.29 Æ 0.59 lm) and turned (S a 0.35 Æ 0.17 lm), were used. It was shown that the chambers were initially occupied by a coagulum, followed by a primi- tive granulation tissue that was subsequently replaced by a provisional matrix formation. Bone apposition onto the implant surface was first seen after 1 week of healing. During the first periods examined (2 h and 4 days), old parent bone in primary contact with the pitches of the implant threads was found at a percentage of 6.3% and 6.5% at the SLA and turned surfaces, respectively. After 1 week, bone apposition onto the implant surfaces increased to a total percentage of new/old bone-to-implant contact of 24.8% at the SLA and 13.9% at the turned surfaces, respec- tively. At the 2-week period of observation, bone resorption of the parent bone at the implant surface was observed. Despite this resorptive process, the total amount of new/ old bone-to-implant contact increased to about 50% and 20% at the SLA and turned surfaces, respectively. The highest value of bone-to-implant contact was found after 4 weeks at the SLA surface, reaching a value of 64%. The percentage subsequently decreased to about 59% after 12 weeks of healing. At the turned surface, however, a Date: Accepted 27 April 2016 To cite this article: Botticelli D, Lang NP. Dynamics of osseointegration in various human and animal models - a comparative analysis. Clin. Oral Impl. Res. 00:2016,1–7. doi: 10.1111/clr.12872 © 2016 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd 1