ORIGINAL ARTICLE Effect of CO 2 laser on root caries inhibition around composite restorations: an in vitro study Jociana Bandeira de Melo & Fernando Seishim Hanashiro & Washington Steagall Jr. & Miriam Lacalle Turbino & Marinês Nobre-dos-Santos & Michel Nicolau Youssef & Wanessa Christine de Souza-Zaroni Received: 28 February 2012 / Accepted: 26 December 2012 / Published online: 5 January 2013 # Springer-Verlag London 2013 Abstract The aim of the present study was to investigate the in vitro effect of CO 2 laser on the inhibition of root surface demineralization around composite resin restora- tions. For this purpose, 30 blocks obtained from human molar roots were divided into three groups: group 1 (nega- tive control), cavity prepared with cylindrical diamond bur + acid etching + adhesive + composite resin restoration; group 2, cavity prepared with cylindrical diamond bur + CO 2 laser (5.0 J/cm 2 ) + acid etching + adhesive + composite resin; and group 3, cavity prepared with cylindrical diamond bur + CO 2 laser (6.0 J/cm 2 ) + acid etching + adhesive + composite resin. After this procedure, the blocks were submitted to thermal and pH cycling. Root surface demineralization around the restorations was measured by microhardness analysis. The hardness results of the longitudinally sec- tioned root surface were converted into percentage of min- eral volume, which was used to calculate the mineral loss delta Z (ΔZ). The percentage of mineral volume, ΔZ, and the percentage of demineralization inhibition of the groups were statistically analyzed by using analysis of variance and Tukey–Kramer test. The percentage of mineral volume was higher in the irradiated groups up to 80 μm deep. The ΔZ was significantly lower in the irradiated groups than in the control group. The percentage of reduction in demineraliza- tion ranged from 19.73 to 29.21 in position 1 (50 μm), and from 24.76 to 26.73 in position 2 (100 μm), when using 6 and 5 J/cm 2 , respectively. The CO 2 laser was effective in inhibiting root demineralization around composite resin restorations. Keywords Carbon dioxide laser . Root caries . Composite resin restorations Introduction There have been constant advancements in Dentistry, seek- ing the development of new techniques and materials, which offer characteristics closer to those of natural teeth, are more resistant to caries development, and are capable of restoring patients’ lost tooth structure. However, this improvement in techniques and materials has not resulted in a reduction of recurrent caries at the tooth/restoration interface. Clinical studies have shown that secondary caries lesions are the most common cause of replacing restorations [1–4]. This fact is even more severe at the root surface owing to the clinical limitations of restorative treatment because of difficult access to the lesion and isolation of the operative field [5]. Thus, new methodologies have been studied in an endeavor to control recurrent caries in this region. Root lesions are more frequent in elderly patients [6–8] and are usually related to factors such as reduced salivary flow, reduced manual dexterity, and motor coordination J. B. de Melo : M. N. Youssef : W. C. de Souza-Zaroni (*) School of Dentistry, Cruzeiro do Sul University (UNICSUL), Av. Dr. Ussiel Cirilo, 225, 08060-070 São Paulo, Brazil e-mail: wansouzazaroni@gmail.com F. S. Hanashiro : W. Steagall Jr. : M. L. Turbino : M. N. Youssef Department of Restorative Dentistry, School of Dentistry, University of São Paulo (USP), Av. Prof. Lineu Prestes, 2227, Cidade Universitária, 05508-900 São Paulo, Brazil M. Nobre-dos-Santos Department of Pediatric Dentistry, Faculty of Dentistry of Piracicaba, State University of Campinas (UNICAMP), Av. Limeira, 901, P.O. Box 52, 13414-903 Piracicaba, São Paulo, Brazil Lasers Med Sci (2014) 29:525–535 DOI 10.1007/s10103-012-1259-0