Effectiveness of antimicrobial photodynamic therapy mediated by butyl toluidine blue in preventing medication-related osteonecrosis of the jaws in rats.

BACKGROUND: Medication-related osteonecrosis of the jaws (MRONJ) is difficult to treat, therefore, prevention would be the ideal clinical approach. This study evaluated the effectiveness of antimicrobial photodynamic therapy (aPDT), mediated by butyl toluidine blue (BuTB) in the prevention of MRONJ-like lesions after tooth extraction in rats. METHODS: Twenty-eight senescent female rats were distributed in groups: VEH and VEH-aPDT, treated with vehicle, ZOL and ZOL-aPDT, treated with 100 µg/Kg of zoledronate, both treatments every three days over seven weeks. After three weeks from the commencement of treatment, the mandibular first molar was extracted. For the VEH and ZOL groups, no local treatment was performed, while with the VEH-aPDT and ZOL-aPDT groups, photodynamic treatment was carried out at 0, 2, and 4 days after extraction. For aPDT, 500µl of BuTB solution was deposited on the dental extraction site (0.5 mg/ml; 60 s), followed by irradiation with low-level laser (InGaAIP; 660 nm; 35 mW; 74.2 J/cm²; 60 s). After 28 postoperative days, euthanasia was performed. The hemimandibles were processed to: (1) histological analysis of tissue repair; (2) histometric analysis of the percentage of newly formed bone tissue (PNFBT) and percentage of non-vital bone tissue (PNVBT); (3) immunohistochemical analysis for tartrate-resistant acid phosphatase (TRAP). RESULTS: The ZOL and ZOL-aPDT groups showed less TRAP-positive cells when compared with VEH and VEH-aPDT. The ZOL group demonstrated great compromise in the tissue repair process, consistent with MRONJ-like lesions. VEH, VEH-aPDT and ZOL-aPDT presented a favorable tissue repair process. PNFBT in the ZOL group was lower than in the VEH, VEH-aPDT and ZOL-aPDT groups, whereas PNVBT in the ZOL group was higher than in the VEH, VEH-aPDT and ZOL-aPDT groups. CONCLUSION: aPDT mediated by BuTB prevented the occurrence of MRONJ-like lesions after tooth extraction in rats.

Efetividade da terapia fotodinâmica antimicrobiana utilizando butil azul de toluidina e laser de baixa potência na prevenção da osteonecrose dos maxilares associada à terapia medicamentosa / Effectiveness of antimicrobial photodynamic therapy using butyl toluidine blue and low-level laser in preventing the occurrence of medicationrelated osteonecrosis of the jaws

O presente estudo teve como objetivo avaliar a efetividade e a segurança do emprego de múltiplas sessões de aPDT, utilizando o butil azul de toluidina (BuAT) e a irradiação com laser de baixa potência (LBP), no sítio de extração dental de ratas com os principais fatores de risco para a ocorrência da osteonecrose dos maxilares associada à terapia medicamentosa (ONM-M). Vinte e oito ratas senescentes foram distribuídas em quatro grupos experimentais: VEI, VEI-aPDT, ZOL e ZOL-aPDT. O protocolo de tratamento teve duração de 7 semanas. Um dia antes do início deste protocolo foi instalada uma ligadura de algodão ao redor do primeiro molar inferior esquerdo para indução da periodontite experimental (PE). Nos grupos VEI e VEI-aPDT, as ratas receberam injeções intraperitoneais de 0,45ml de solução de cloreto de sódio 0,9% (veículo) a cada três dias. Nos grupos ZOL e ZOL-aPDT, as ratas receberam 0,45ml do veículo acrescido de 100µg/Kg do zoledronato a cada três dias. Após três semanas do início do protocolo de tratamento a ligadura foi removida e foi realizada a exodontia do primeiro molar inferior esquerdo. Nos grupos VEI e ZOL não foi efetuado nenhum tratamento local no sítio de extração dental. Nos grupos VEI-aPDT e ZOL-aPDT foram realizadas sessões de aPDT aos 0, 2, e 4 dias pós exodontia. Para a aPDT depositouse sobre o sítio de extração dental 300µl de BuAT (concentração: 0,5mg/ml; tempo de pré-irradiação, 60s) em seguida foi realizada a irradiação com laser de baixa potência (laser: InGaAIP; 660nm; 35mW; 74,2J/cm²; 60s) emissor: InGaAlP; comprimento de onda: 660 nm, laser visível - vermelho; potência: 35 mW; densidade energética por ponto: 74,2 J/cm2 ; tempo de aplicação: 60s). Decorridos 28 dias pós-operatórios foi realizada a eutanásia. As hemimandíbulas foram devidamente processadas para assegurar que no sítio de extração dental fossem efetuadas: 1) análise clínica; 2) análise histológica da reparação tecidual; 3) análise histométrica da Porcentagem de Tecido Ósseo Neoformado (PTOnf); 4) análise histométrica da Porcentagem de Tecido Ósseo Não Vital (PTOnv) e; análise imunoistoquímica de células TRAPpositivas. Os dados foram submetidos à análise estatística com nível de significância de 5%. Os grupos ZOL e ZOL-aPDT apresentaram menor quantidade de células TRAP-positivas quando comparados com os grupos VEI e VEI-aPDT. O grupo ZOL apresentou grande comprometimento do processo de reparação tecidual, condizentes com um quadro de ONM-M. Os grupos VEI, VEI-aPDT e ZOL-aPDT apresentaram um processo de reparação tecidual favorável do sítio de extração dental. No grupo ZOL a PTOnf no sítio de extração dental se mostrou menor que nos grupos VEI, VEI-aPDT e ZOL-aPDT. No grupo ZOL a PTOnv se mostrou maior que nos grupos VEI, VEIaPDT e ZOL-aPDT. No grupo ZOL-aPDT a PTOnv se apresentou maior que nos grupos VEI e VEI-aPDT. O emprego de múltiplas sessões de aPDT, utilizando o BuAT e LBP, no sítio de extração dental de ratas senescentes tratadas com alta dose de zoledronato se mostrou uma estratégia terapêutica segurança e efetiva para evitar a ocorrência da ONM-M pós exodontia(AU)

The present study aimed to evaluate the effectiveness and safety of using multiple aPDT sessions, using butyl toluidine blue (BuTB) and low-level laser irradiation (LLL), at the dental extraction site of rats with the main risk factors for the occurrence of medication-related osteonecrosis of the jaws (MRONJ). Twenty-eight senescent rats were distributed in four experimental groups: VEH, VEH-aPDT, ZOL and ZOL-aPDT. The treatment protocol lasted 7 weeks. One day before the beginning of this protocol, a cotton ligature was installed around the mandibular first molar left to induce experimental periodontitis (EP). In the VEH and VEH-aPDT groups, the rats received intraperitoneal injections of 0.45 ml of 0.9% sodium chloride solution (vehicle) every three days. In the ZOL and ZOL-aPDT groups, the rats received 0.45 ml of the vehicle plus 100 µg / Kg of zoledronate every three days. Three weeks after the beginning of the treatment protocol, the ligature was removed and extraction of the mandibular first molar left was performed. In the VEH and ZOL groups, no local treatment was performed at the tooth extraction site. In the VEH-aPDT and ZOL-aPDT groups, aPDT sessions were performed at 0, 2, and 4 days after extraction. For aPDT, 300µl of BuTB was deposited on the dental extraction site (0.5mg / ml; pre-irradiation time, 60s), followed by irradiation with low-level laser (laser: InGaAIP; 660nm; 35mW; 74.2J / cm²; 60s). After 28 postoperative days, euthanasia was performed. The hemimandibles were properly processed to ensure that at the tooth extraction site: 1) clinical analysis; 2) histological analysis of tissue repair; 3) histometric analysis of the Percentage of Neoformed Bone Tissue (PNFBT); 4) histometric analysis of the Percentage of NonVital Bone Tissue (PNVBT) and; immunohistochemical analysis of TRAP-positive cells. The data were submitted to statistical analysis with a 5% significance level. The ZOL and ZOL-aPDT groups showed less TRAP-positive cells when compared with the VEH and VEH-aPDT groups. The ZOL group showed great compromise in the tissue repair process, consistent with MRONJ. The groups VEH, VEH-aPDT and ZOL-aPDT presented a favorable tissue repair process at the dental extraction site. In the ZOL group, the PNFBT at the tooth extraction site was lower than in the VEH, VEH-aPDT and ZOL-aPDT groups. In the ZOL group, PNVBT was higher than in the VEH, VEHaPDT and ZOL-aPDT groups. In the ZOL-aPDT group, PNVBT was higher than in the VEH and VEH-aPDT groups. The use of multiple aPDT sessions, using BuTB and LLL, at the dental extraction site of senescent rats treated with a high dose of zoledronate proved to be a safe and effective therapeutic strategy to prevent the occurrence of MRONJ after tooth extraction(AU)

Effects of butyl toluidine blue photosensitizer on antimicrobial photodynamic therapy for experimental periodontitis treatment in rats.

AIM: This study evaluated three concentrations of butyl toluidine blue (BuTB) for antimicrobial photodynamic therapy (aPDT) in experimental periodontitis (EP) in rats. MATERIAL AND METHODS: EP was ligature-induced at the first mandibular molar in 105 rats. Ligature was removed after 7 days and animals were distributed into the following treatments: SRP, scaling and root planing (SRP) plus saline solution; BuTB-0.1, SRP plus BuTB at 0.1 mg/mL; aPDT-0.1, SRP plus BuTB at 0.1 mg/mL and InGaAlP diode laser (DL) irradiation; BuTB-0.5, SRP plus BuTB at 0.5 mg/mL; aPDT-0.5, SRP plus BuTB at 0.5 mg/mL and DL irradiation; BuTB-2.0, SRP plus BuTB at 2 mg/mL; aPDT-2.0, SRP plus BuTB at 2 mg/mL and DL irradiation. Five animals from each group were submitted to euthanasia at 7, 15 and 30 days post-treatment. The furcation area was submitted to histological, histometric and immunohistochemical (TGF-ß1, OCN and TRAP) analyses. RESULTS: aPDT-0.5 group presented a better tissue remodeling in all periods, resolution of the inflammatory response and bone neoformation areas at 30 days. aPDT-0.5 also resulted in higher immunolabeling patterns of TGF-ß1 at all periods (p < 0.05) and of OCN at 30 days (p < 0.05). CONCLUSION: aPDT-0.5 showed the best benefits for inflammatory response and periodontal repair process.