Effect of Laser-Induced Dentin Modifications on Periodontal Fibroblasts and Osteoblasts: A New In Vitro Model Carlo Galli,* † Giovanni Passeri, † Antonio Cacchioli, ‡ Giacomo Gualini,* Francesca Ravanetti, ‡ Erida Elezi,* † and Guido M. Macaluso* Background: The erbium-doped:yttrium, aluminum, and garnet (Er:YAG) laser has been shown to be a promising tool for root treatment in periodontitis, but little information is available regarding the surface characteristics after this treat- ment, mainly because it is difficult to obtain standardized den- tin samples for in vitro studies. Methods: Commercially available standardized dentin disks were treated with an Er:YAG laser at different settings and used as a substrate for human primary osteoblastic cells (hOBs) and periodontal ligament fibroblasts (PLFs). Cell proliferation on untreated dentin was measured by 3-(4,5-dimethylthiazol- 2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay after 3, 6, 12, 24, and 48 hours of culture. The effects of the laser on dentin and cell morphology on treated and untreated samples were investigated by scanning electron microscopy after 3, 6, 24, and 48 hours of culture. Results: Dentin samples supported proliferation for both cell types, although growth kinetics were different. The laser dra- matically affected the dentin profile, creating a rough and irreg- ular surface. Cells grew easily on untreated dentin, but fewer cells were present on treated areas, often displaying long filo- podes. hOBs showed poorer adhesion to treated dentin than PLFs. Conclusions: The dentin disks provide a standardized and useful tool to study dentin surface modifications in vitro. PLFs behaved differently from hOBs on dentin, possibly because of their different affinity to this tissue and/or their differentiation state. The changes induced by the laser produced a less favor- able environment for cell adhesion or growth, and treated den- tin seemed to be more suitable for PLF adhesion compared to hOB adhesion. J Periodontol 2009;80:1648-1654. KEY WORDS Dentin; Er:YAG laser; laser; osteoblast; periodontal ligament fibroblast. T herapeutic protocols for periodon- tal diseases usually encompass a phase of scaling and root plan- ing performed by means of manual, sonic, or ultrasonic instruments. 1,2 The main goal of the treatment is the me- chanical removal of biofilm and calculus from the root of the tooth. This creates a healthy and smooth surface that can allow the healing of the periodontal tissues in the absence of pathogens and their byproducts that can cause and sustain the inflammation. One of the consequences of root planing is the removal of the thin cementum layer that covers the root and the exposure of the underlying dentin tissue to the wound. Therefore, in most periodontal thera- pies, dentin, and not cementum, is the substrate with which cells from the neighboring tissues interact during heal- ing. 3-5 Similarly, when performing a re- shaping of the root anatomy for reasons other than periodontitis, e.g., as a part of a periodontal plastic surgery procedure, dentin is one of the key tissues involved in periodontal healing. Beside mechanical instrumentation, the use of lasers has been proposed as a tool to create a root surface without cal- culus, contaminants, or a smear layer. 7-11 It has been shown that the erbium- doped:yttrium, aluminum, and garnet (Er:YAG) laser is a promising tool to per- form the removal of biofilm and cal- culus from the root 12-14 because of its * Unit of Periodontology, University of Parma, Parma, Italy. † Department of Internal Medicine, University of Parma. ‡ Section of Anatomy, Department of Animal Health, University of Parma. doi: 10.1902/jop.2009.090152 Volume 80 • Number 10 1648