Alkawari Huda M, Baidas Laila F, Alyahya Areen A, Alotaibi Renad A, Alshayea Eman I
Department of Pediatric Dentistry and Orthodontics, College of Dentistry, King Saud University, PO Box 68004, Riyadh, 11527, Saudi Arabia.
College of Dentistry, King Saud University, PO Box 68004, Riyadh, 11527, Saudi Arabia.
BMC Oral Health. 2025 Feb 1;25(1):172. doi: 10.1186/s12903-025-05548-8.
A decrease in oral pH levels may have detrimental effects on vacuum-formed retainers since an acidic oral environment could impact the mechanical and physical properties of these retainers. The present In vitro study aimed to evaluate the effect of simulated gastric acid at pH 4 and 1.2 on the surface microhardness, flexural strength, and color change of three different types of orthodontic retainer materials.
A total of 144 vacuum-formed commercially available retainer materials: copolyesters, polypropylene, and PET-G (n = 48/group) were evaluated. Each specimen was immersed in distilled water, and then the specimens were divided into two subgroups: those with a pH of 4 and those with a pH of 1.2. The microhardness test was performed using Innovatest, the flexural strength was evaluated by a universal testing machine, and the color change was analyzed using a spectrophotometer. The data were analyzed using One-Way ANOVA and independent sample t test at a significance value of P ≤ 0.05.
Our findings indicated a significant decrease in flexural strength in all the experimental groups after immersion in pH 1.2 and 4 solutions (P < 0.001), with PET-G being the most affected material, followed by copolyester and polypropylene. Only copolyester demonstrated a significant decrease in surface microhardness following immersion in a pH 4 solution (P = 0.025). All materials exhibited the greatest degree of color alteration CP (P = 0.006), PP (P = 0.001), and PET-G (P = 0.009) respectively.
The study concluded that copolyester adversely affects flexural strength, surface microhardness, and color when subjected to immersion in simulated gastric acid. Therefore, care is recommended for patients diagnosed with gastroesophageal reflux disease.
口腔pH值降低可能会对真空成型保持器产生有害影响，因为酸性口腔环境可能会影响这些保持器的机械和物理性能。本体外研究旨在评估pH值为4和1.2的模拟胃酸对三种不同类型正畸保持器材料的表面显微硬度、抗弯强度和颜色变化的影响。
共评估了144种市售真空成型保持器材料：共聚酯、聚丙烯和PET-G（每组n = 48）。每个标本浸入蒸馏水中，然后将标本分为两个亚组：pH值为4的亚组和pH值为1.2的亚组。使用Innovatest进行显微硬度测试，通过万能试验机评估抗弯强度，并使用分光光度计分析颜色变化。使用单因素方差分析和独立样本t检验对数据进行分析，显著性值P≤0.05。
我们的研究结果表明，所有实验组在浸入pH值为1.2和4的溶液后抗弯强度均显著降低（P < 0.001），其中PET-G受影响最大，其次是共聚酯和聚丙烯。只有共聚酯在浸入pH值为4的溶液后表面显微硬度显著降低（P = 0.025）。所有材料分别表现出最大程度的颜色变化，CP（P = 0.006）、PP（P = 0.001）和PET-G（P = 0.009）。
该研究得出结论，共聚酯在浸入模拟胃酸时会对抗弯强度、表面显微硬度和颜色产生不利影响。因此，建议对诊断为胃食管反流病的患者予以注意。
