Sealing capacity of a photochromatic flowable composite as protective base in nonvital dental bleaching C. Llena 1,2 , J. Amengual 3 & L. Forner 4 1 Valencian Health Service; 2 Cardenal Herrera-CEU University; 3 Private Practice, Vinalesa; and 4 Department of Stomatology, University of Valencia, Valencia, Spain Abstract Llena C, Amengual J, Forner L. Sealing capacity of a photochromatic flowable composite as protective base in nonvital dental bleaching. International Endodontic Journal, 39, 185–189, 2006. Aim To evaluate microleakage of a flowable compos- ite used as a protective isolating base, applied with different adhesive systems. Methodology Seventy root-filled teeth were divided into seven groups. A flowable composite base (Tetric Flow Chroma) was used with three adhesive techniques (Syntac, Excite, Excite DCS; in the three cases with and without acid etching) and in a control group without dentine conditioning or adhesive placement. A 30% hydrogen peroxide solution was applied for 24 h in the pulp chambers, followed by the placement of a dye (silver nitrate) for 4 h. Each tooth was sectioned longitudinally, and examined under 4· magnification to assess the tooth/restoration dye leakage following a four-degree scale. Percentage of dye penetration was registered. Statistical analysis was made through the Tukey and Mann–Whitney U-tests. Results Maximum leakage (100% of specimens) was recorded in the control group without an adhesive system. In the groups subjected to acid etching, the percentage of leakage corresponded to Excite DSC (10%), followed by Syntac (20%) and Excite (30%). In the groups in which only an adhesive system was used, 50% of the teeth demonstrated dye leakage. Statistically significant differences in terms of leakage were observed between the control group and the experimental groups (P < 0.05). There were no sig- nificant differences among the experimental groups, but comparing the leakage percentages obtained between the groups in which the teeth were subjected to prior acid etching, and those in which no etching was carried out, observed differences were significant (P ¼ 0.04). Conclusions There were no significant differences between the adhesive systems in terms of leakage. Acid etching significantly reduced leakage. Keywords: bleaching, bonding system, cavity base, flowable composite resin, microleakage. Received 4 August 2004; accepted 11 October 2005 Introduction The bleaching of root-filled teeth requires protection of the pulp chamber in order to prevent progression of the bleaching agents through the dentinal tubules towards the cervical periodontal tissues from where such agents can give rise to post-bleaching external cervical root resorption (Fuss et al. 1989, Friedman 1997). Although the mechanisms by which this occurs have not been fully elucidated, some authors attribute the phenom- enon to localized inflammatory reactions caused by bleaching-mediated oxidative stress (Floyd 1990, Dahl- strom et al. 1997), while other investigators (Friedman et al. 1988, Madison & Walton 1990, Rotstein 1991, Heller et al. 1992, Heithersay et al. 1994, Weiger et al. 1994, Friedman 1997) consider it to be an immune response against dentine denatured by the action of the bleaching agents (Koulaouzidou et al. 1996). The appropriate placement of intracoronal and/or intra-radicular restorative materials provides an Correspondence: Carmen Llena, Valencian Health Service, Albuixech n° 8, 2 a , 46021, Valencia, Spain (Tel.: +34963604877; fax: +34963864144; e-mail: llena@uv.es). ª 2006 International Endodontic Journal International Endodontic Journal, 39, 185–189, 2006 185