Purpose: The study evaluated and compared the local reaction and material absorption characteristics of NovaBone Dental Collagen Wound Dressing with a predicate dental collagen wound dressing, ACE Resorbable Collagen Plug (RCP) upon implantation into an open socket extraction site of minipigs. Necropsy was performed 2, 4, or 8 weeks after initial implantation.
Methods: Twelve minipigs underwent bilateral surgery to remove the second and third premolars on the right and left mandible. Empty sockets on the animals’ left side received the ACE-RCP (control article) and those on the contralateral side received the NovaBone Dental Collagen Wound Dressing (test article). Figure 1 maps out the implantation sites.
Animals were randomized and assigned to three groups consisting of four animals per group. Animals assigned to Group 1 were sacrificed 14 days post-surgery, those in Group 2 were sacrificed 27 or 29 post-surgery (2 animals/day), and those assigned to Group 3 were sacrificed 56 days post-surgery. Local reactivity and material absorption (defined as the physical disappearance of the implanted material from the implantation site) were evaluated via histologic methods at each sacrifice interval. Lighted microscopic evaluations were performed consisting of semi-quantitative evaluation of paired sections for tissue and inflammatory reactions and residual collagen implant absorption.
Results: All animals survived to scheduled termination. Overall, animals gained weight throughout the course of the study. There were no adverse changes in appearance, behavior, or activity in animals that were attributed to either the test or control articles. No gross observations attributed to the test or control articles were noted at necropsy (Figure 2). Neither the control nor test implant sites contained recognizable implant material. The predominant implant site findings were fibrosis and osteoneogenesis, which were present in all implant sites at all sacrifice intervals.
Adipose tissue infiltrates in implant sites was also similar in the control and test article sites at all sacrifice intervals. This finding was least frequent 14 days post-surgery but had increased 27-29 days post-surgery at which time it plateaued. Cellular infiltrates were most frequent 14 days post-surgery and progressively decreased at subsequent sacrifice intervals. All of these observations were expected responses to the extraction and implant procedure and none were considered to be adverse. The severity scores are summarized in Figure 3.
Conclusions: None of the implant sites contained recognizable implant material suggesting that both test and control articles were completely resorbed within 14 days of implantation. Cellular infiltrates were most frequent 14 days post-surgery and progressively decreased at each subsequent sacrifice interval. All of these observations were expected responses to the extraction and implant procedure and none were considered to be adverse. The mean implant site scores for the control and test articles were similar at each sacrifice interval and decreased between day 14 and day 56 post-surgery. Based on the similarity and frequency of the histologic findings and the mean group implant site scores, NovaBone Dental Collagen Wound Dressing and the predicate ACE-RCP perform similarly in vivo.
Dr. Dawn Ruben, D.V.M.; Hans Peter Dyke, J.D.; Dr. Melinda Tyner, Ph.D.
References:
[1] H. Lee, M. Choi, J. Chang, J. Jung, M. Kim, N. Lee, J. Kim, and M. Choi. Dental Imaging Characterization of Micropigs. Korean Journal of Veterinary Research. 2010; 50(4): 311-317