Cosmetic dentistry beauty & science

technique _ periodontal regenerative therapy I populations can populate the defect following a surgical intervention: (1) epithelial cells, which are the fastest proliferating and the fastest migrating cellsofallfivegroups,(2)gingivalconnectivetissue cells, (3) alveolar bone cells, (4) periodontal liga- ment cells, (5) cementoblasts. Guided tissue regen- erationusesbarriermembranesexcludingfromthe woundareaepithelialandconnectivetissuecellsin ordertoallowtheslowercellgroupstopopulatethe defect and determine the regeneration of the new ligament. Epithelial cells are in fact inhibited from growing via contact inhibition. Contact inhibition isthenaturalprocessofarrestingcellgrowthwhen twoormorecellscomeintocontactwitheachother or with a solid surface. In a Petri dish cell culture, normal epithelial cells proliferate and migrate centripetally until reaching the borders of the Petri capsule. In GTR, epithelial cell migration stops when the epithelium covers the membrane and comes into contact with the root surface. Thesecondmechanismisthebloodclotstability mechanism.Thefibrincomponentofthebloodclot canattachtothealveolarbone,gingivalconnective tissue and root surface. It has been demonstrated by Wikesjo and coworkers that when the blood clot is not allowed to attach to the root surface, epithe- lial down-growth occurs and new connective tis- sue attachment formation is precluded. Instead, if the fibrin attachment to the root surface is not disrupted by any mechanical or physical trauma, the epithelium migrates over the clot and stops migrating when meeting the clot-root interface. Both of these mechanisms well explain how it is possible to direct wound healing toward regenera- tion, repair in relation to the adopted technique or biomaterial used, whether it is a membrane, a bone substitute or just a stabilised clot. The first human histologic evidence of a newly regenerated periodontal ligament dates back to 1982 when Nyman et al.2 used a Millipore filter on amandibularincisorwhichwaspreviouslyinvolved in periodontitis, allowing cells originating from the periodontal ligament to repopulate the root surface during healing. Since then, a number of publications have shown histological evidence of a newly regenerated ligament with various surgi- cal techniques, different biomaterials and growth factors. At the meantime, we should still keep in mind that epithelial down-growth is reversible. Already in the 1980’s, Listgarten et al.3 had demonstrated— in an animal model evaluating access flaps—that while the length of the junctional epithelium did not change between the three months and the twelve months postoperative dates, this measure was “pushed” in a coronal direction thus reducing sulcus depth and increasing the length of the con- nective tissue attachment. _Conclusion In light of this, the importance of maintaining the structural integrity of the gingival tissues as opposedtoapocketeliminationprocedure(i.e.api- cally positioned flaps, osseous resective surgery) mustbeincreasinglystressed,especiallywhensur- gical treatment in the aesthetic area is warranted. Periodontal therapy has been reshaped pro- foundly by the great amount of research and liter- ature produced in the last few decades. What used to be a discipline of large, invasive flaps, has now evolved to a discipline mainly encompassing non- surgical therapy, risk management strategies, and minimally invasive flaps for the treatment of lo- calised defects. This transformation rendered peri- odontal therapy of the aesthetic area a much less invasive and more acceptable approach, which has to be embraced by all practitioners dedicating their profession toward this exciting and continuously evolving specialty._ Editorial note: A list of references is available from the author. Figs. 6a–b_The one-year result shows a pocket depth of 3 mm with a gain of 10 mm when compared to the baseline. In the radiographic image, biomaterial is still detectable with an optimal bone filling. I 27cosmeticdentistry 3_2013 Giulio Rasperini Department of Biomedical,Surgical and Dental Sciences,Unit of Periodontology,Foundation IRCCS Ca' Granda Polyclinic,University of Milan,Milan, Italy Via XX Settembre,119 29121 Piacenza,PC,Italy giulio@studiorasperini.it _contact implants Fig. 6a Fig. 6b