Oral and Dental Diseases Research Center, Faculty of Dentistry, Shiraz University of Medical Sciences, Shiraz, Fars, Iran.
Department of Prosthodontics, Faculty of Dentistry, Shiraz University of Medical Sciences, Shiraz, Fars, Iran.
PLoS One. 2024 Apr 16;19(4):e0301799. doi: 10.1371/journal.pone.0301799. eCollection 2024.
Marginal fit significantly impacts the long-term success of dental restorations. Different pattern fabrication methods, including hand-waxing, milling, or 3D printing, may affect restorations accuracy. The effect of porcelain firing cycles on the marginal fit of metal-ceramic restorations remains controversial, with conflicting findings across studies.
The aim was to evaluate the potential effects of multiple porcelain firings (3, 5, 7 cycles) as well as pattern fabrication method (conventional hand-waxing, milling, and 3D printing) on the marginal adaptation of 3-unit implant-supported metal-ceramic fixed partial dentures. It was hypothesized that neither the wax pattern fabrication method nor repeated ceramic firings would significantly affect the marginal adaptation of metal-ceramic crowns.
In this in-vitro study, 30 Cobalt-Chromium alloy frameworks were fabricated based on pattern made through three techniques: conventional hand-waxing, CAD-CAM milling, and CAD-CAM 3D printing (n = 10 per group). Sixteen locations were marked on each abutment to measure the vertical marginal gap at four stages: before porcelain veneering and after 3, 5, and 7 firing cycles. The vertical marginal gap was measured using direct microscopic technique at ×80 magnification. Mean vertical marginal gap values were calculated and two-way ANOVA and Tukey's post hoc tests were used for inter-group comparisons (α = 0.05).
The 3D printing group showed significantly lower (P<0.001) mean vertical marginal gaps (60-76 μm) compared to the milling (77-115 μm) and conventional hand-waxing (102-110 μm) groups. The milling group exhibited a significant vertical gap increase after 3 firing cycles (P<0.001); while the conventional (P = 0.429) and 3D printing groups (P = 0.501) showed no significant changes after 7 firing cycles. Notably, the vertical marginal gap in all groups remained below the clinically acceptable threshold of 120 μm.
CAD-CAM 3D printing provided superior marginal fit compared to CAD-CAM milling and conventional hand-wax pattern fabrication methods. The impact of porcelain firing on the mean marginal gap was significant only in the milling group. All three fabrication techniques yielded clinically acceptable vertical marginal adaptation after repeated firings. Additive manufacturing holds promise to produce precise implant-supported prostheses.
边缘适合度对牙科修复体的长期成功有显著影响。不同的印模制作方法，包括手工蜡型、铣削或 3D 打印，可能会影响修复体的精度。瓷化循环对金属陶瓷修复体边缘适合度的影响仍存在争议，不同研究得出的结果相互矛盾。
本研究旨在评估多次瓷化（3、5、7 次循环）以及印模制作方法（传统手工蜡型、铣削和 3D 打印）对 3 单位种植体支持的金属陶瓷固定局部义齿边缘适应性的潜在影响。假设蜡型制作方法或重复瓷化均不会显著影响金属陶瓷冠的边缘适应性。
本体外研究中，根据三种技术（传统手工蜡型、CAD-CAM 铣削和 CAD-CAM 3D 打印）制作钴铬合金基底后，制作 30 个基底（每组 10 个）。在四个阶段（瓷层堆筑前和 3、5、7 次瓷化后），在每个基牙的 16 个位置标记点，以测量垂直边缘间隙。使用直接显微镜技术在×80 放大倍数下测量垂直边缘间隙。计算平均垂直边缘间隙值，并进行双向方差分析和 Tukey 事后检验进行组间比较（α=0.05）。
3D 打印组的平均垂直边缘间隙（60-76μm）明显低于铣削组（77-115μm）和传统手工蜡型组（102-110μm）（P<0.001）。铣削组在经过 3 次瓷化循环后，垂直间隙显著增加（P<0.001）；而传统组（P=0.429）和 3D 打印组（P=0.501）在经过 7 次瓷化循环后，没有明显变化。值得注意的是，所有组的垂直边缘间隙均保持在临床可接受的 120μm 以下。
CAD-CAM 3D 打印在边缘适合度方面优于 CAD-CAM 铣削和传统手工蜡型制作方法。瓷化对平均边缘间隙的影响仅在铣削组显著。三种制作技术在重复瓷化后均能获得临床可接受的垂直边缘适应性。增材制造有望生产精确的种植体支持的修复体。
