Department of Oral Rehabilitation and Biosciences, Oregon Health & Science University School of Dentistry, Portland, Oregon, USA.
Graduate Prosthodontics, Texas A&M University College of Dentistry, Dallas, Texas, USA.
J Prosthodont. 2024 Jan;33(1):86-94. doi: 10.1111/jopr.13658. Epub 2023 Feb 15.
Intraoral scanners are used widely as an alternative to conventional impressions, but studies on the influence of finish line location and saliva contamination on scanning trueness are lacking. The purpose of this in vitro study was to evaluate the influence of finish line location and saliva contamination on the scanning trueness of crown finish lines.
Three ivorine teeth were prepared for all-ceramic crowns with finish lines placed equigingivally, 0.5 mm subgingivally, and 1.0 mm subgingivally. A single-cord technique was used for gingival retraction, and a total of 180 intraoral scans were made using two intraoral scanners (Emerald; Planmeca USA Inc., Hoffman Estates, IL, USA & Trios 3; 3Shape A/S, Copenhagen, Denmark). The prepared teeth were separated from the dentoform and scanned using the same intraoral scanners to create reference scans. All scans were imported to the design software (Dental System 2019; 3Shape A/S, Copenhagen, Denmark). After marking the finish lines of prepared teeth, intraoral scans were aligned to the reference scans for comparisons. Vertical and horizontal marginal discrepancies were measured at four different measuring points (buccal, lingual, mesial, and distal) and analyzed. Two-way ANOVA and Tukey HSD tests were used for statistical analysis (α = 0.05).
The average vertical and horizontal discrepancies from various groups ranged from -33 to 440 µm. For both intraoral scanners, subgingival finish line groups showed greater vertical and horizontal discrepancies compared with equigingival finish line groups. Saliva contamination significantly increased both vertical and horizontal discrepancies for all finish line locations. The discrepancy increases due to saliva contamination were greater for the subgingival groups.
Subgingival finish lines were not accurately captured using the intraoral scanners. The presence of saliva significantly reduced scanning trueness, and this was amplified when the finish lines were located subgingivally.
口内扫描仪作为传统印模的替代方法被广泛应用，但关于边缘线位置和唾液污染对扫描精度的影响的研究还很缺乏。本体外研究的目的是评估边缘线位置和唾液污染对牙冠边缘线扫描精度的影响。
为全瓷冠制备了三颗象牙牙，边缘线分别置于平齐牙龈、龈下 0.5mm 和龈下 1.0mm。采用单根技术进行牙龈退缩，使用两种口内扫描仪（美国 Planmeca 公司的 Emerald 和 3Shape A/S 的 Trios 3）共进行 180 次口内扫描。将预备牙与牙托体分离，使用相同的口内扫描仪进行扫描以创建参考扫描。将所有扫描导入设计软件（3Shape A/S 的 Dental System 2019）。在标记预备牙的边缘线后，将口内扫描与参考扫描对齐进行比较。在四个不同的测量点（颊侧、舌侧、近中侧和远中侧）测量垂直和水平边缘差异，并进行分析。使用双向方差分析和 Tukey HSD 检验进行统计分析（α=0.05）。
来自不同组的平均垂直和水平差异范围为-33 至 440μm。对于两种口内扫描仪，龈下边缘线组的垂直和水平差异均大于平齐牙龈边缘线组。唾液污染显著增加了所有边缘线位置的垂直和水平差异。龈下组因唾液污染导致的差异增加更大。
口内扫描仪无法准确捕捉龈下边缘线。唾液的存在显著降低了扫描精度，而当边缘线位于龈下时，这种影响会放大。
