Abdulla Fahad, Khamis Hassan, Milosevic Alexander, Abuzayda Moosa
BDS MSc Former resident, Department of Prosthodontics, Hamdan Bin Mohamed College of Dental Medicine, Mohamed Bin Rashid University (MBRU) of Medicine and Health Sciences, Dubai, UAE.
BSc MSc DEA PhD, Department of Biostatistics, Hamdan Bin Mohamed College of Dental Medicine, Mohamed Bin Rashid University (MBRU) of Medicine and Health Sciences, Dubai, UAE.
J Clin Exp Dent. 2018 Dec 1;10(12):e1192-e1197. doi: 10.4317/jced.55269. eCollection 2018 Dec.
This study aimed to determine the degree of taper and total occlusal convergence angles (TOC) for all-ceramic bonded crown preparations carried out by private practitioners in Dubai, UAE.
A convenience sample of all-ceramic crown preparations carried out by private dental practitioners were scanned (Carestream CS 3500) from casts and the digital images assessed. The degree of taper was measured on the axial walls of each crown preparation and the bucco-lingual and mesio-distal convergence angles subsequently calculated.
A total of 154 dentists prepared a total of 206 crown preparations (72 anterior, 134 posterior). The mean convergence angles mesio-distally for all preparations was 24.6° (sd 11.8º), and for the bucco-lingual it was 32.6° (sd 15.3°). The mean TOC was 28.6°. In anterior preparations, the mean bucco-lingual convergence angle was 38.8° (sd 12.2°) compared to 29.3° (sd 15.5°) for posterior preparations (<0.001). Mean mesio-distal convergence anteriorly was 20.6° (sd 10.18°) compared to 26.7° (sd 12.16°) posteriorly (<0.001). Distal and buccal taper were significantly greater on posterior teeth (<0.001) compared to anteriors whereas lingual taper was greater on anterior teeth (<0.001). Mesial taper was not different. Premolars had significantly lower convergence values compared to other teeth.
Bucco-lingual and mesio-distal convergence angles significantly exceeded the clinically acceptable convergence angle of between 10° and 22°. Greater axial taper is recommended for resin bonded all-ceramic crowns but reliance on adhesion in such preparations rather than parallelism may reduce retention and have increased biologic cost to pulp health. All-ceramic crown preparations, convergence angles, axial taper.
本研究旨在确定阿联酋迪拜的私人执业医生进行的全瓷粘结冠修复体预备的锥度程度和总咬合聚合角（TOC）。
从模型上扫描由私人牙科医生进行的全瓷冠修复体预备的便利样本（Carestream CS 3500），并对数字图像进行评估。在每个冠修复体预备的轴壁上测量锥度程度，随后计算颊舌向和近远中向聚合角。
共有154名牙医制备了总共206个冠修复体（72个前牙，134个后牙）。所有修复体近远中向的平均聚合角为24.6°（标准差11.8°），颊舌向为32.6°（标准差15.3°）。平均TOC为28.6°。在前牙修复体中，颊舌向平均聚合角为38.8°（标准差12.2°），而后牙修复体为29.3°（标准差15.5°）（<0.001）。前牙近远中向平均聚合角为20.6°（标准差10.18°），而后牙为26.7°（标准差12.16°）（<0.001）。与前牙相比，后牙的远中向和颊侧锥度明显更大（<0.001），而前牙的舌侧锥度更大（<0.001）。近中锥度无差异。与其他牙齿相比，前磨牙的聚合值明显更低。
颊舌向和近远中向聚合角显著超过了临床上可接受的10°至22°的聚合角。对于树脂粘结全瓷冠，建议采用更大的轴面锥度，但在此类预备中依赖粘结而非平行度可能会降低固位力，并增加对牙髓健康的生物学成本。全瓷冠修复体预备、聚合角、轴面锥度。
