Implant Stability and Histological Evaluation of a Dental Implant Assembly with Tantalum Based Porous Material: An Experimental Study in Hound Dogs
A porous tantalum material (TM) has an ability to facilitate osseointegration and provide a substrate for cell adhesion that has made it desirable to use in orthopedic surgery1,2. The objective of this study was to compare the implant stability and biological tissue responses of an experimental dental implant assembly with porous TM shell and a tapered self tapping implant with an apical vent (control) placed in the extraction socket (Type 1: immediate placement) of a canine model. A total of 48 implants with 4.1mm diameter and 13mm length (24 each of TM & control) were placed bilaterally in the extraction sockets in premolar and molar regions of the mandibles of six hound dogs (4 implants per side). Two animals each were euthanized at 2, 4& 12 week time-points post implantation. Implant stability quotient (ISQ) measurements were recorded for each dog at the time of surgery and necropsy using resonance frequency analysis (RFA) to determine implant stability. Calcein was administered to all animals 4 & 11 days prior to necropsy to evaluate the rate of new bone formation. Histopathology (Sanderson's bone stain and Van Gieson counter stain) and calcein label assessments were performed on the sections from each implant. Osseointegration of control implants was achieved via bone on-growth whereas the TM implants achieved both osseointegration via ongrowth around the threaded sections as well as ingrowth through the pores of the TM shell. The ISQ values illustrated an increasing trend for TM implants over the 12-week healing period whereas the control implants, though ISQ values were greater than 60, did not demonstrate any such trend (Fig 1a). Further, statistically significant differences were detected between the ISQ values for TM and control implants in the early healing phase (Weeks 2&4), TM implants had higher mean values. The histopathology findings indicated that there was no evidence of acute inflammation or bacterial infection for any TM or control implants. There was low incidence of mild chronic inflammation and minimal fibrosis for both types of implants. No significant differences were detected between the TM and control implants for any of the histopathological parameters. Higher amounts of newly formed bone were observed in the sites placed with TM implants (Fig 1(b) &(c)) than those placed with control implants. The current findings suggest that TM implants with both ongrowth and ingrowth (due to active bone formation in the TM pores) potentially, provide good bone anchorage during early healing period when placed in extraction sockets. The results indicate that the TM implants when placed in extraction sockets provide equivalent or better implant stability and no increased risk for infection as compared to the clinically documented control implants.
Reference:
1. Koussostathis SD, Tsakotos G, Papkostas I, Macheras G. Biological Processes at bone- tantalum interface. A Review Article. J of Orthopaedics 2009;6(4)e3 http://www.jortho.org/2009/6/4/e3/index.htm
2. Bobyn JD, Stackpool G, Toh K-K, et. al. Bone ingrowth characteristics and interface mechanics of a new porous tantalum biomaterial. J Bone Joint Surg. 1999; 81-B:907-914.
Figure 1: (a) Summary of ISQ values for control and TM groups immediately after placement and at 2, 4 & 12 weeks post surgery. (b) Histology section with calcein labeling demonstrating new bone formation in and around pores of the TM implant at 12 weeks post surgery. (c) Histology section stained with Sanderson's Bone Stain demonstrating bone in-growth into the pores of the TM implant at 12 weeks post surgery.