目的:研究不同温度条件下新型大气压冷等离子体(radio-frequency atmospheric-pressure glow discharge,RF-APGD)处理对牙本质粘接强度的影响。方法:(1)收集新鲜拔除的、无龋坏的、完整的第三磨牙52颗,采用精密低速切割机制备平行于牙合中层牙本质薄片,每颗离体牙制备1片 [(900±100) μm]。将52个中层牙本质薄片随机分为对照组和实验组,其中对照组4片,无处理;实验组48片,按新型RF-APGD等离子体不同处理温度(4 ℃、10 ℃、20 ℃、30 ℃)平均分为4组,每大组12片。每大组按照不同处理时间(10 s,20 s,30 s)平均分为3个小组,每小组4片。采用扫描电镜观察脱矿牙本质表面形貌。(2)收集20颗完整第三磨牙随机分为对照组和4个实验组,每组4颗。对照组,无处理;4 ℃、10 ℃、20 ℃和 30 ℃ 4个实验组,每组采用新型RF-APGD等离子体处理20 s。实验组及对照组采用低速水冷精密切割机垂直于牙长轴去除牙合面牙釉质,暴露中层牙本质;采用32%磷酸酸蚀剂对牙本质表面进行酸蚀;采用牙本质粘接剂和树脂进行牙本质-树脂粘接,采用万能力学机进行牙本质-树脂粘接试件即刻微拉伸强度测定,观察不同温度新型RF-APGD等离子体处理对牙本质-树脂即刻粘接性能的影响。结果:(1)扫描电镜观察脱矿牙本质表面形貌显示,30 ℃和20 ℃新型 RF-APGD 等离子体处理组,脱矿牙本质胶原纤维表面经新型RF-APGD等离子体处理10 s即会出现微结构的破坏;10 ℃新型RF-APGD等离子体处理脱矿牙本质表面 20 s,即会出现牙本质胶原纤维之间间隙变小、表面结构坍塌等现象;4 ℃新型RF-APGD等离子体处理10 s、20 s及30 s,脱矿牙本质表面胶原纤维网状结构均能维持蓬松结构。(2)牙本质-树脂即刻微拉伸强度结果显示,对照组为(47.4±0.5) MPa,4 ℃、10 ℃、20 ℃和30 ℃新型RF-APGD等离子体处理组分别为(57.8±0.7) MPa、(51.9±0.7) MPa、(29.7±1.0) MPa和(22.2±1.5) MPa,其中4 ℃新型RF-APGD等离子体处理组所获得的微拉伸强度最高,与其他各组相比,差异具有统计学意义(P<0.05), 4 ℃和10 ℃新型RF-APGD等离子体处理组和对照组相比,牙本质-树脂微拉伸粘接强度分别提高了21.9%和9.5%。结论:4 ℃新型RF-APGD等离子体对脱矿牙本质胶原纤维的处理,较更高温度的新型RF-APGD等离子体更有利于提高牙本质-树脂的即刻粘接性能。

Objective: To investigate the effect of different treatment temperatures of a novel cold atmospheric plasma jet treatment on the resin-dentin bonding. Methods:(1) Fifty-two freshly extracted, non-carious and intact third molars were collected. The occlusal one-third of the crown was removed by means of a water-cooled low-speed Isomet saw. One dentin disc [(900 ±100) μm] was prepared for each tooth. The fifty-two dentin discs were randomly divided into control group and experimental groups, of which four were in control group, and forty-eight were divided into four experimental groups according to the different treatment temperatures (4 ℃, 10 ℃, 20 ℃ and 30 ℃) of the novel radio-frequency atmospheric-pressure glow discharge (RF-APGD) plasma jet, twelve in each group. Each experimental group was divided into three subgroups according to different treatment time (10 s, 20 s and 30 s), with four in each subgroup. The occlusal one-third of the crown was removed by means of a water-cooled low-speed Isomet saw. The morphology of demineralized dentin surfaces was analyzed using field emission scanning electron microscopy. (2) Twenty unerupted, non-carious and intact third molars were randomly divided into five groups, four in each group: control group, untreated; 4 ℃, 10 ℃, 20 ℃ and 30 ℃ experimental groups, each group was treated with the RF-APGD plasma jet for 20 s. The micro-tensile resin dentin bond strength was tested after 20 s RF-APGD plasma jet treatment with different temperatures, using a universal mechanical machine. Results:(1)The field emission scanning electron micro-scopy results indicated that when compared with the control group, a 10 s RF-APGD plasma jet treatment with 30 ℃ and 20 ℃ collapsed the collagen scaffold. Collagen fibrils maintained an uncollapsed three-dimensional structure after the 4 ℃ RF-APGD plasma jet treatment for even 30 s treatment. (2) The microtensile resin dentin bond strength results of the 4 ℃ RF-APGD plasma jet treatment group (57.8±0.7) MPa were significantly higher than that of the control group [(47.4±0.5) MPa] and 10 s, 20 s and 30 s RF-APGD plasma treatment group [(51.9±0.7) MPa,(29.7±1.0) MPa and (22.2±1.5) MPa] with statistically significant difference (P<0.05). Compared with the control group, the micro-tensile bond strength increased about 21.9% and 9.5% after 4 ℃ and 10 ℃ RF-APGD plasma jet treatment, respectively. Conclusion:Compared with other treatment temperatures, this novel RF-APGD plasma jet treatment with the temperature of 4 ℃ can preserve the three-dimensional morphology of demineralized dentin better, and can improve the resin-dentin bonding.