3/6 John Mazz - GTR and Regeneration Flashcards
How quickly do epithelial cells, CT fibroblasts, bone cells, and PDL cells migrate?
How long until the gingival sulcus is reepithelialized after gingivectomy?
Engler ‘66
Epithelial cells: 0.5 mm/day
CT fibroblasts: 0.5 mm/day
Bone cells: 0.05 - 0.06 mm/day
PDL cells: 0.05 - 0.06 mm/day
The gingival sulcus is reepithelialized after 7 days
How long does it take until “full healing” of connective tissue occurs after gingivectomy?
Ramfjord ‘66
21-35 days
How thick is periosteum?
300 - 500 microns
What did Melcher describe in his 1976 article regarding tissue migration?
Melcher ‘76
Melcher posited that these four cell types were responsible for rebuilding the components of the periodontium but that they competed to occupy the periodontal space based on how fast they could migrate to the area. For example, if fibroblasts from the gingival connective tissue occupy the space adjacent to the alveolar bone and PDL, alveolar bone would not form vertically into the space because the gingival fibroblasts are not osteogenic. He hypothesized that placing autogenous, and therefore osteogenic, grafting material in the area of desired alveolar bone growth may be sufficient to exclude gingival connective tissue, give the fibroblasts farther to travel, and give the osteogenic cells more time to colonize the site for better regenerative potential (Melcher, 1976).
Describe the studies by Karring et al 1985, and the study by Bower ‘89, on periodontal regeneration
Karring ‘85
Animal histology study - using 4 monkeys
Periodontitis was induced; up to 50% alveolar bone was lost. Roots were cleaned, removed granulation tissue and cementum, removed crowns, and sealed with primary closure. Histology was done at 3 months postop.
Histology showed that Cementum and PDL fibers are regenerated by cells from the PDL that migrate coronally during healing.
Bowers ‘89
Human regeneration study
Part I included submerged and non-submerged periodontally involved teeth where root surfaces were cleaned and covered with the flap or left open, with no additional grafting or barrier used in either group. Regenerated attachment was seen only in the submerged group, bolstering Karring’s findings.
Different cells, if they colonize a GTR space first, will result in different tissues:
* Epithelial cells result in long junctional epithelium formation
* gingival connective tissue cells result in root resorption
* bone cells result in ankylosis
* cells from the PDL result in new cementum and PDL fibers constituting new attachment.
Describe the first studies that examined GTR
Nyman ‘82
* GTR was attempted on a severely periodontally compromised mandibular lateral incisor prior to extraction. The flap was reflected, the root cleaned, and a Millipore filter with a 0.22μm pore size was used as the barrier.
* This barrier extended from 1mm apical buccal bone crest to 2mm coronal to the CEJ and was secured in place on the tooth with resin.
* The tooth was extracted en bloc with the buccal periodontium and histologic analysis showed that dentogingival epithelium proliferated coronally on the outside of the barrier while new cementum and collagen fibers extended up the root 5mm coronal to where the cementum had been denuded. At the apical extent of the surgical site, new bone had filled in the vertical bony defect.
Haney ‘93
Animal histology study; GTR using ePTFE
5 beagle dogs; defects were created surgically bilaterally.
One side of the mouth had the experimental treatment, ePTFE membrane + CAF, while the other side was the control, CAF only.
Histologic analysis showed that JE formation was shorter in teeth with membranes and usually ended coronal to the membrane. Bone regeneration was greater in membrane treated teeth and was strongly correlated to the area beneath the membrane, but only in teeth without membrane exposure. Cementum formation was minimal across both treatments. Finally, root resorption was increased in membrane treated teeth. From these results, Haney came to five important conclusions:
1) Connective tissue repair to the root surface is a function of wound stability
2) Bone regeneration is dependent on space provision
3) Exclusion of gingival connective tissue from the root surface does not prevent root resorption
4) Provisions for guided tissue regeneration do not necessarily support cementum regeneration
5) Complete gingival coverage of the barrier membrane appears critical for optimal healing.
Describe the PASS principle, as described by Wang & Boyapati in 2006
Primary Closure with passive adaptation of the flaps is important to minimize wound remodeling and contraction; membrane exposure also decreases the volume of bone gained and leads to more complications like infection.
Angiogenesis is important for bone growth as sufficient blood flow to the site will bring in growth factors, cytokines, and progenitor cells to regenerate the site.
Space Creation/Maintenance is accomplished using bone graft materials, tenting screws, or reinforced membranes and allows for the proliferation of bone and PDL cells throughout the area of desired attachment apparatus regeneration. Finally, when Stability of the initial blood clot achieved and maintained, a predictable wound healing sequence occurs which relies heavily on the multitude of growth factors, cytokines, and signaling molecules that are present in the initial clot.
What are the indications for GTR?
Nibali ‘21: A defect depth >4 shows a statistically significant association with radiographic bone gain at 12 months post-surgery. This was true for both GTR and EMD
(NSSD for CAL gain was found.)
Also, narrower angles (< 37 degrees) showed statistically sig. radiographic bone gain 12 months post-surgery.
