The Impact of CO2 Laser Treatment and Acidulated Phosphate Fluoride on Enamel Demineralization and Biofilm Formation

Introduction: This study evaluated the impact of CO2 laser treatment and acidulated phosphate fluoride (APF) on enamel demineralization and biofilm formation, using in vitro and in situ designs.Methods: Demineralized enamel slabs were distributed among 8 groups: placebo, placebo + continuous CO2 laser, placebo + repeated CO2 laser, placebo + ultrapulsed CO2 laser, 1.23% APF, APF + continuous CO2 laser, APF + repeated CO2 laser and APF + ultrapulsed CO2 laser. In the in vitro study, 15 enamel slabs from each group were subjected to a pH-cycling regimen for 14 days. In the cross over in situ design, 11 volunteers wore palatal appliances with demineralized enamel slabs for 2 periods of 14 days each. Drops of sucrose solution were dripped onto enamel slabs 8×/day. Biofilms formed on slabs were collected and the colony-forming units (CFU) of Streptococcus mutans and Lactobacillus were determined. Results: For both in vitro and in situ studies, there was no significant difference between treatments (P > 0.05). However, all treatments increased microhardness of demineralized enamel (P < 0.05). After a further in situ cariogenic challenge, with the exception of the placebo, all treatments maintained microhardness values (P < 0.05). Microbiological analysis showed no difference in Streptococcus mutans (P > 0.05) or Lactobacillus (P > 0.05) counts between groups. Conclusion: The results suggest that APF gel combined with the CO2 laser, regardless of the pulse emission mode used, was effective in controlling enamel demineralization, but none of the tested treatments was able to prevent bacterial colonization

Selective caries removal using Er:YAG laser and dentin biomodification with chitosan

O objetivo deste estudo foi avaliar o efeito da remoção seletiva da lesão de cárie utilizando laser de Er:YAG, seguida da biomodificação da dentina com quitosana. Os objetivos específicos foram: 1) Avaliar os elementos químicos e a morfologia da superfície dentinária, bem como, a microdureza da subsuperfície (experimento 1) e 2) Avaliar a resistência de união da interface resina/dentina e sua morfologia após 24h, 6 e 12 meses de envelhecimento dos espécimes, a perda de massa seca e a resistência à degradação do colágeno (experimento 2). Lesões de cárie em dentina foram criadas pelo método de ciclagem do pH (14 dias) em 208 espécimes bovinos. Os espécimes foram divididos de acordo com método de remoção seletiva da lesão de cárie: broca (em baixa rotação) ou laser de Er:YAG (250 mJ/4Hz). Os espécimes receberam ácido fosfórico a 35%, e foram subdivididos de acordo com a biomodificação da dentina: sem biomodificação ou quitosana a 2,5%. No experimento 1, os espécimes foram submetidos às análises de Espectroscopia Eletrônica de Análise Química (EDS) e Microscopia Eletrônica de Varredura (MEV) da superfície e microdureza da subsuperfície dentinária. No experimento 2, os espécimes foram submetidos a resistência de união à microtração e MEV da interface adesiva após 24h, 6 e 12 meses de armazenamento em água, avaliação da perda de massa seca e liberação de hidroxiprolina (HYP). Os dados foram analisados por meio de testes paramétricos e não paramétricos (=0.05). A remoção seletiva da lesão de com laser de Er: YAG promoveu aumento da microdureza da dentina afetada (p=0,03) e redução na quantidade de Ca (00,05). Após 24h, os maiores valores de resistência de união foram obtidos para a broca em comparação ao laser Er:YAG (p0,664; p>0,263) e a liberação de hidroxiprolina (p>0,6347; p>0,4274) não foram influenciadas, respectivamente, pelo método de remoção da cárie ou pela biomodificação dentinária. A remoção seletiva da dentina cariada com o laser de Er: YAG aumentou a microdureza da dentina afetada por cárie, alterando sua morfologia superficial e composição química. A biomodificação com quitosana não influenciou a composição estrutural e química da dentina residual. Após 24h de armazenamento em gua, a resistência de união da resina composta à dentina foi afetada pelo laser de Er:YAG. No entanto, a resistência de união à dentina irradiada foi mantida, enquanto a dentina tratada com broca apresentou redução contínua. A biomodificação com quitosana, independente do método de remoção utilizado, preservou a resistência de união e a interface adesiva ao longo de 12 meses. O laser de Er:YAG e a biomodificação com quitosana não influenciaram na perda de massa seca e na liberação de hidroxiprolinaThe aim of this study was to evaluate the effect of Er:YAG laser for selective removal of carious lesion, followed by biomodification with chitosan. The specific objectives were: 1) To evaluate the chemical elements and the morphology of the dentin surface, as well as, the subsurface microhardness (Experiment 1). 2) To evaluate the microtensile bond strength (TBS) and adhesive interface after 24h, 6 and 12 months of water storage, the dry mass loss and dentin collagen degradation (Experiment 2). Dentinal caries lesions were created in 208 bovine specimens by pH-cycling method (14 days). Specimens were divided according to the carious removal method: bur (low-speed handpiece) or Er:YAG laser (250 mJ/4Hz). Specimens were treated with 35% phosphoric acid and were subdivided according to dentin biomodification: without chitosan (control) and 2.5% chitosan. For the experiment 1, specimens were submitted to Energy Dispersive X-Ray Spectroscopy (EDS) and Scanning Electron Microscopy (SEM) and subsurface microhardness of the dentin. For the experiment 2, specimens were submitted to microtensile bond strength and SEM analysis of the adhesive interface after 24h, 6 and 12 months of storage in water, evaluation of dry mass loss and hydroxyproline release (HYP). Data were analyzed by parametric and non-parametric tests (=0.05). The selective caries removal with Er:YAG laser increased the microhardness value of caries-affected dentin (p=0.03) and reduced the amounts of Ca (00.05). After 24h, the highest bond strength values were found for bur compared to Er:YAG laser (p0.664; p>0.263) and HYP release (p>0.6347; p>0.4274) were not influenced, respectively, by the carious removal method or by dentin biomodification. The selective removal of carious dentin with Er:YAG laser increased microhardness of residual caries-affected dentin changing its surface morphology and chemical composition. The biomodification with chitosan did not influence the structural and chemical composition of residual dentin. After 24 hours of water storage, the composite resin bond strength to dentin was affected by Er:YAG laser. However, the bond strength to irradiated-dentin was maintained, while the bur-treated dentin showed a continuous reduction. Biomodification with chitosan, regardless of removal method used, preserved the bond strength and adhesive interface over 12 months. The dry mass and the hydroxyproline release were not influence