Graduate Prosthodontics, Texas A & M University System Health Science Center, Baylor College of Dentistry, Dallas, TX 75246, USA.
J Prosthet Dent. 2010 Aug;104(2):122-32. doi: 10.1016/S0022-3913(10)60105-9.
Fabrication of indirect complete crowns that are in occlusal harmony upon insertion remains a problem in restorative dentistry, and dental stone cast expansion may play a role.
This 3-part investigation compared occlusal contacts in a simulated patient with a harmonious occlusion with centric occlusion equal to maximum intercuspation (CO=MI) and an inharmonious occlusion (CO not equal MI) with mounted stone casts, and compared the occlusal contacts after fabrication of a posterior complete crown fabricated on equilibrated and nonequilibrated dental stone casts.
A dentoform mounted in a semi-adjustable articulator served as the simulated patient and control. In part 1, a single set of maxillary and mandibular ADA type IV and V derived dental stone casts were fabricated and mounted (CO not equal MI), and occlusal contacts/near contacts were compared. In part 2, 10 type IV and 10 type V cast mountings (CO=MI) were compared. In part 3, 10 type IV cast mountings were fabricated for adjustment (experimental) and 10 for no adjustment (control). A mandibular ADA type IV gold alloy complete crown was fabricated and adjusted on each set of casts and then returned to the dentoform. Vinyl polysiloxane interocclusal records of all mountings were scanned for optical density, and contacts were used to quantify occlusal contacts as exhibiting contact or near contact. Data were analyzed with Kruskal-Wallis ANOVA and Mann-Whitney U tests (alpha=.05).
The cast adjustment protocol (intervention) was successful in eliminating the majority of the occlusal disharmony in the casts believed to be caused by the effects of stone expansion. Actual and near contact areas for cast mountings of the equilibrated simulated patient were significantly different from those of the simulated patient (P<.001; P=.001, respectively). Actual and near contact areas for inserted crowns fabricated from adjusted casts were significantly different from those of the simulated patient (P<.001; P=.007, respectively), but actual contact areas were not different from those of the simulated patient with no crown inserted.
In this study, occlusal contacts of a simulated patient (dentoform) could not be accurately replicated with mounted dental stone casts. A cast adjustment procedure can aid in fabrication of a crown with a more accurate occlusion.
在修复牙科中，制作与正中咬合（CO）一致的间接全冠仍然存在问题，而石膏铸造膨胀可能会对此产生影响。
本研究分为三个部分，比较了具有和谐咬合（CO=MI）的模拟患者的咬合接触情况，与具有不和谐咬合（CO 不等于 MI）的石膏铸模的咬合接触情况，并比较了在平衡和非平衡石膏铸模上制作的后牙全冠的咬合接触情况。
半可调式牙颌模型上的牙雕作为模拟患者和对照组。在第一部分中，制作并安装了一组上颌和下颌 ADA 类型 IV 和 V 衍生的石膏铸模（CO 不等于 MI），并比较了咬合接触/近接触情况。在第二部分中，比较了 10 个 ADA 类型 IV 和 10 个 ADA 类型 V 的铸模安装情况（CO=MI）。在第三部分中，制作了 10 个 ADA 类型 IV 的铸模用于调整（实验组）和 10 个 ADA 类型 IV 的铸模用于不调整（对照组）。然后，在每个铸模上制作并调整了一个下颌 ADA 类型 IV 的金合金全冠，并将其放回牙雕上。所有铸模的乙烯基聚硅氧烷印模记录均进行了光学密度扫描，并利用接触情况来量化咬合接触，以确定接触或近接触。数据采用 Kruskal-Wallis ANOVA 和 Mann-Whitney U 检验进行分析（α=.05）。
铸模调整方案（干预）成功消除了铸模中大多数被认为是由石膏膨胀引起的咬合不和谐。平衡模拟患者的铸模安装的实际和近接触区域与模拟患者的有显著差异（P<.001；P=.001）。从调整后的铸模上制作的插入牙冠的实际和近接触区域与模拟患者的有显著差异（P<.001；P=.007），但与未插入牙冠的模拟患者相比，实际接触区域没有差异。
在本研究中，模拟患者（牙雕）的咬合接触无法通过安装的石膏铸模准确复制。铸模调整程序有助于制作更准确咬合的牙冠。
