____________________________________________________________________________________________________________________________________________________________________ Research Article ____________________________________________________________________________________________________________________________________________________________________ Clinical and microbiological effect of calcium hydroxide protection in indirect pulp capping in primary teeth ALICE SOUZA PINTO, DDS, MS, FERNANDO BORBA DE ARAÚJO, DDS, MS, PHD, RENATA FRANZON, DDS, MARCIA CANÇADO FIGUEIREDO, DDS, MS, PHD SANDRA HENZ, DDS, MS, FRANKLIN GARCÍA-GODOY, DDS, MS & MARISA MALTZ, DDS, MS, PHD ABSTRACT: Purpose : To evaluate clinically and microbiologically the effect of calcium hydroxide (CH) on carious dentin on primary teeth submitted to indirect pulp capping (IPC). Methods : Twenty 4-7 year-old subjects with 42 treated teeth participated in the study. The treatment consisted of incomplete excavation of the demineralized dentin, application of a CH or gutta-percha (GP) layer and sealing with a resin-based composite for 4-7 months. After cavity preparation and sealing, the dentin was evaluated clinically (color and consistency) and microbiologically. Dentin samples were cultured on blood agar under aerobic and anaerobic conditions, in Mitis Salivarius agar and Rogosa SL agar. Results : 39 teeth (20 in the CH Group and 19 in the GP Group) were reopened 4-7 months post-treatment for clinical and microbiological evaluation. In all teeth, the initial demineralized dentin was wet and soft or leathery. In the CH Group, 10% of the lesions were yellow, 80% light brown and 10% dark brown and in the GP Group, 94.7% were light brown and 5.3% dark brown. After treatment, the dentin was dry, 90% (Group CH) and 84.2% (Group GP) were dark brown. The final consistency was either leathery or hard. Three samples in the CH Group and five in Group GP changed from soft to leathery; only one sample (GP) remained leathery. 85% in the CH Group and 68.4% in GP Group turned hard after treatment. All bacterial counts decreased significantly by the end of treatment. In the CH Group, the bacterial (Log 10 CFU + 1) anaerobic growth decreased from 4.84 ± 1.31 to 1.35 ± 1.54, aerobic from 4.09 ± 1.04 to 0.92 ± 1.30 and lactobacilli from 3.24 ± 1.22 to 0.36 ± 0.89, respectively; the mutans streptococci from 2.05 ± 1.84 to 0.14 ± 0.60. In GP Group, anaerobic growth decreased from 5.22 ± 0.96 to 2.02 ± 1.65 and aerobic from 4.23 ± 1.37 to 1.08 ± 1.29 and lactobacilli from 2.06 ± 1.81 to 0.00 ± 0.00, respectively; the mutans streptococci from 3.16 ± 1.59 to 0.28 ± 0.84. (Am J Dent 2006;19:382-387). CLINICAL SIGNIFICANCE: The resin-based composite sealing of dentin caries lesions in primary teeth, with or without calcium hydroxide liner over the infected remaining tissue, may help preserve dental tissue as well as pulp vitality.  Prof. Fernando Borba de Araújo, Department of Pediatric Dentistry, Faculty of Dentistry, UFRGS, Rua Ramiro Barcelos, 2492, Bom Fim, Porto Alegre, Rio Grande do Sul, Brazil. E-: fernando.araujo@ufrgs.br Introduction Dental caries is known as a bacteriological infectious disease, transmissible among humans. Its treatment, according to health promotion concepts, is to reestablish the patient’s oral balance by controlling etiologic factors with non-invasive pro- cedures, such as dietary and hygiene instruction and/or profes- sional fluoride application. However, a retentive dentin lesion, considered a plaque retention factor, hampers the patient’s control of the disease. These situations demand invasive inter- vention with carious tissue removal and cavity sealing, providing the patient conditions to improve his/her oral health. Most clinicians use visual and tactile exams to diagnose and remove carious lesions, which are based on dentin hardness. 1 However, this method does not guarantee complete bacterial removal from the dentin. 2 In fact, bacteria usually remain even when all soft dentin is removed. 3 Studies evaluating partial removal of carious dentin demonstrated a reduction in the number of cariogenic micro- organisms 4-6 and absence of further lesion progression. 6-10 The complete removal of bacteria in deep carious lesions might result in pulp exposure. In such cases, a layer of carious tissue is left over the pulp. This procedure is called indirect pulp capping (IPC). Calcium hydroxide (CH) liner is usually the material of choice because it is alkaline, biocompatible, induces pulp-dentin remineralization and decreases bacterial infec- tion. 6,11-13 However, it is not clear if the high rate of success of this treatment and inactivation of the remaining carious dentin (dentin is harder with substantial reduction in cultivable microflora) is due to the sealing of the carious dentin (isolation from the oral cavity) or the liner material (CH) placed over the infected remaining tissue. This study evaluated, clinically and microbiologically, the performance of primary molars with deep caries cavities sealed with a resin-based composite after partial removal of infected dentin at the pulpal wall, with or without previous application of CH. The null hypothesis tested in this study was that the application of gutta-percha (GP) over dentin would not affect the clinical and microbiological behavior of the restoration. Materials and Methods Sample and inclusion criteria – The sample consisted of 42 human primary molars with deep caries lesions, comprising 19 occlusal, 12 proximal-occlusal, nine lingual-occlusal and two mesial-occlusal-distal cavities from eight girls and 12 boys (4-7 years old). The main inclusion criteria were absence of spontaneous pain, swelling or fistula, tooth mobility not compatible with chronological age, and all cavity margins in enamel. Radiographic criteria were caries lesions at the internal half of the dentin thickness, absence of pulp contact with the lesion and alterations suggesting degenerative pulp conditions. The study was approved by the Ethics Committee of the UFRGS (Federal University of Rio Grande do Sul, Port Alegre,