The number of bleaching sessions influences pulp tissue damage in rat teeth.
BACKGROUND
Hydrogen peroxide tooth bleaching is claimed to cause alterations in dental tissue structures. This study investigated the influence of the number of bleaching sessions on pulp tissue in rats.


METHODS
Male Wistar rats were studied in 5 groups (groups 1S-5S) of 10 each, which differed by the number (1-5) of bleaching sessions. In each session, the animals were anesthetized, and 35% hydrogen peroxide gel was applied to 3 upper right molars. Two days after the experimental period, the animals were killed, and their jaws were processed for light microscope evaluation. Pulp tissue reactions were scored as follows: 1, no or few inflammatory cells and no reaction; 2, <25 cells and a mild reaction; 3, between 25 and 125 cells and a moderate reaction; and 4, 125 or more cells and a severe reaction. Results from each experimental group were compared between groups and within groups to the corresponding unbleached upper left molars and analyzed for significant differences using the Kruskal-Wallis test (P < .05).


RESULTS
All tissue sections showed significant bleaching-induced changes in the dental pulp. After 1 bleaching session, necrotic tissue in the pulp horns and underlying inflammatory changes were observed. The extent and intensity of these changes increased with the number of bleaching sessions. After 5 sessions, the changes included necrotic areas in the pulp tissue involving the second third of the radicular pulp and intense inflammation in the apical third.


CONCLUSIONS
The number of bleaching sessions directly influenced the extent of pulp damage.
Department of Endodontics, Araçatuba Dental School, UNESP-Universidade Estadual Paulista, São Paulo, Brazil. Electronic address: lucianocintra@foa.unesp.br.
Luciano Tavares Angelo
LT
Cintra
Francine
F
Benetti
Aguinaldo Cândido
AC
da Silva Facundo
Luciana Louzada
LL
Ferreira
João Eduardo
JE
Gomes-Filho
Edilson
E
Ervolino
Vanessa
V
Rahal
André Luiz Fraga
AL
Briso
D000818:Animals; D003782:Dental Pulp / Q000187:drug effects*; D003786:Dental Pulp Cavity / Q000187:drug effects; D003790:Dental Pulp Necrosis / Q000139:chemically induced; D003809:Dentin, Secondary / Q000187:drug effects; D006861:Hydrogen Peroxide / Q000008:administration & dosage* / Q000009:adverse effects; D008297:Male; D008963:Molar / Q000187:drug effects; D009804:Odontoblasts / Q000187:drug effects; D011671:Pulpitis / Q000139:chemically induced; D051381:Rats; D017208:Rats, Wistar; D013997:Time Factors; D019227:Tooth Apex / Q000187:drug effects; D014073:Tooth Bleaching / Q000379:methods*; D058205:Tooth Bleaching Agents / Q000008:administration & dosage* / Q000009:adverse effects; D014092:Tooth Root / Q000187:drug effects
D058205:Tooth Bleaching Agents; D006861:Hydrogen Peroxide
Hydrogen peroxide; pulp reaction; tooth bleaching