A Prospective Randomized-controlled Clinical and Histological Evaluation of Extraction Sites Augmented with Cortical Powder and Cancellous Particulate Allograft

Tooth extraction sites that heal without grafting are often associated with reduction of local bone dimension and volume sometimes leading to implant placement challenges^1,2.  Although tooth extraction sites heal adequately without intervention, reduction of un-grafted post-extraction ridge dimensions may be problematic for dental implant treatment planning. 

Bone tissue bank inventories usually include autologous bone augmentation materials with two particle size ranges described as: “crushed cancellous particulates” typically in the range of 500 – 800 microns diameter and “cortical powder” where granule dimensions are < 200 microns.  A user-perception that the cancellous particulates have greater performance than the cortical powder is reflected in the sales of the two products (Miami Tissue Bank communication).  This preference leads to shortages of cancellous particulate product when cortical powder is readily available.  Evidence is needed for demonstrating the equivalence of cancellous particulate and cortical powder allograft bone materials for grafting extraction sites.  This study was designed to assess the functional performance of the two autologous materials to allow consideration of therapeutic substitution of the powder for the particulates.      

This prospective, randomized-controlled study evaluates outcomes from patients needing multiple tooth extractions (pre-molar or molar) treated with either cortical powder, cancellous particulates, or without grafting (control).  Fresh extraction sites are randomly assigned to any of the three groups.  Study patients have an immediate post-extraction CT scan to establish baseline alveolar ridge dimensions and a five-month post-treatment scan to allow for analysis of ridge volume changes. A trephine drill is used as part of the osteotomy preparation and the bone material is evaluated histologically for assessment of vital (de novo) bone development and residual graft.  Bone samples are processed at the Hard Tissue Research Laboratory, University of Minnesota.  NanoTite Tapered Prevail dental implants (Biomet3i) placed in these study sites are monitored for 2 years to document integration success and maintenance of integration during support of prosthesis.

Fifteen patients were enrolled and treated between September 2009 and May 2010 having a total of 32 tooth extraction procedures.  The mean graft healing time was 6.5 + 0.3 months.   A total of 21 trephine cores were successfully obtained and processed for histological analysis and 30 dental implants were placed.  One implant placement effort was discontinued due to insufficient bone in a control site.  One implant failed to integrate and declared a failure after three weeks due to infection.  Histological outcomes for the samples obtained from study sites include a mean percent de novo bone of 85.1 ± 13.8 (SD), 88.5 ± 16.6, and 100% for cortical powder, cancellous particulate and control sites respectively.  

Histological and implant outcomes for molar extraction sites treated with the two allograft materials suggest a clinical equivalence between crushed cancellous particulates and cortical powder.   

References:

1. Covani U, Cornelini R, Barone A. Bucco-lingual bone remodeling around implants placed into immediate extraction sockets: a case series. J Periodontol. 2003;74(2):268-73.

2. Covani U, Cornelini R, Barone A. Vertical crestal bone changes around implants placed into fresh extraction sockets. J Periodontol. 2007;78(5):810-5.