title: Histopathological, Microbiological, and Radiographic Analysis of Antimicrobial Photodynamic Therapy for the Treatment of Teeth with Apical Periodontitis: A Study in Rats' Molars.
abstract: OBJECTIVE
  The aim of this study was to evaluate in vivo, by histological and radiographic analysis, the response of apical tissues of rats' teeth with experimentally induced apical periodontitis, after one- and two-session endodontic treatment with and without photodynamic therapy (PDT). A microbiological analysis was also performed to verify bacterial reduction after each treatment.
  
  
  BACKGROUND
  Studies carried out in recent years highlighted the antibacterial potential of PDT when associated with conventional endodontic therapy in vitro. Although the antimicrobial effect of PDT is well-established, tissue response to PDT in teeth with apical periodontitis lacks studies.
  
  
  METHODS
  Thirty-two rats' root canals were assigned to four groups: one session/PDT-[chemomechanical preparation (CMP)+root canal filling (RCF)]; two sessions/PDT- [CMP+calcium hydroxide (CH) for 14 days+RCF]; one session/PDT+ [CMP+PDT+RCF], and two sessions/PDT+ [CMP+PDT+CH for 14 days+RCF]. For microbiological evaluation, samples were collected before and after proposed treatments. For radiographic and histological analysis, the animals were euthanized after 28 days and the mandibles surgically removed.
  
  
  RESULTS
  PDT associated with conventional endodontic therapy was able to promote significant bacterial reduction in root canals with induced apical periodontitis, but this reduction was not significantly different to conventional endodontic therapy alone. Although radiographic evaluation showed no significant differences, histological analysis showed lower scores for neutrophils/eosinophils in PDT-treated groups and macrophages/giant cells in CH groups.
  
  
  CONCLUSIONS
  The use of low-level laser as light source did not promote major improvement on radiographic and histological repair, but since the number of inflammatory cells slightly decreased, it may optimize repair by modulating inflammatory process. PDT may be indicated as an adjunct to conventional endodontic therapy for teeth with apical periodontitis, in association with an interappointment dressing with CH, in an attempt to produce better conditions to stimulate repair.
authors.affiliation: 1 Postgraduate Program in Dentistry, Pontifical Catholic University of Rio Grande do Sul (PUCRS) , Porto Alegre, RS, Brazil .
authors.forename: Alessandra Cesar
authors.initials: AC
authors.lastname: Trindade
authors.affiliation: 1 Postgraduate Program in Dentistry, Pontifical Catholic University of Rio Grande do Sul (PUCRS) , Porto Alegre, RS, Brazil .
authors.forename: José Antônio Poli
authors.initials: JAP
authors.lastname: de Figueiredo
authors.affiliation: 2 Laboratory of Immunology and Microbiology, Faculty of Biosciences, Pontifical Catholic University of Rio Grande do Sul (PUCRS) , Porto Alegre, RS, Brazil .
authors.forename: Sílvia Dias
authors.initials: SD
authors.lastname: de Oliveira
authors.affiliation: 2 Laboratory of Immunology and Microbiology, Faculty of Biosciences, Pontifical Catholic University of Rio Grande do Sul (PUCRS) , Porto Alegre, RS, Brazil .
authors.forename: Valdir Cristóvão
authors.initials: VC
authors.lastname: Barth Junior
authors.affiliation: 2 Laboratory of Immunology and Microbiology, Faculty of Biosciences, Pontifical Catholic University of Rio Grande do Sul (PUCRS) , Porto Alegre, RS, Brazil .
authors.forename: Stephanie Wagner
authors.initials: SW
authors.lastname: Gallo
authors.affiliation: 1 Postgraduate Program in Dentistry, Pontifical Catholic University of Rio Grande do Sul (PUCRS) , Porto Alegre, RS, Brazil .
authors.forename: Carina
authors.initials: C
authors.lastname: Follmann
authors.affiliation: 1 Postgraduate Program in Dentistry, Pontifical Catholic University of Rio Grande do Sul (PUCRS) , Porto Alegre, RS, Brazil .
authors.forename: Carlos Frederico Brilhante
authors.initials: CFB
authors.lastname: Wolle
authors.affiliation: 3 Postgraduate Dental Education Unit, University of Warwick, Warwick University Medical School , Coventry, United Kingdom .
authors.forename: Liviu
authors.initials: L
authors.lastname: Steier
authors.affiliation: 4 Department of Stomatology, School of Dentistry, Federal University of Santa Maria (UFSM) , Santa Maria, RS, Brazil .
authors.forename: Renata Dornelles
authors.initials: RD
authors.lastname: Morgental
authors.affiliation: 1 Postgraduate Program in Dentistry, Pontifical Catholic University of Rio Grande do Sul (PUCRS) , Porto Alegre, RS, Brazil .
authors.forename: João Batista Blessmann
authors.initials: JBB
authors.lastname: Weber
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D000890:Anti-Infective Agents / Q000494:pharmacology; D001707:Biopsy, Needle; D004195:Disease Models, Animal; D007150:Immunohistochemistry; D054023:Lasers, Semiconductor / Q000627:therapeutic use; D008297:Male; D008963:Molar / Q000187:drug effects / Q000528:radiation effects; D010485:Periapical Periodontitis / Q000000981:diagnostic imaging* / Q000188:drug therapy* / Q000473:pathology; D010778:Photochemotherapy / Q000379:methods*; D011861:Radiography, Dental / Q000379:methods; D011897:Random Allocation; D051381:Rats; D017208:Rats, Wistar; D012016:Reference Values; D018570:Risk Assessment; D012390:Root Canal Therapy / Q000379:methods*; D018709:Statistics, Nonparametric; D016896:Treatment Outcome
chemical_list: D000890:Anti-Infective Agents
keywords: biofilm; endodontics; laser; photodynamic therapy; photosensitizers; root canal disinfection