Tilen Raphael, Patcas Raphael, Bornstein Michael M, Ludwig Björn, Schätzle Marc
Clinic for Orthodontics and Pediatric Dentistry, Center for Dental and Oral Medicine and Cranio-Maxillofacial Surgery, University of Zurich, Switzerland.
Oral and Maxillofacial Radiology, Applied Oral Sciences, Faculty of Dentistry, The University of Hong Kong, Hong Kong SAR, China.
Eur J Orthod. 2017 Nov 30;39(6):646-653. doi: 10.1093/ejo/cjx022.
There is only little knowledge on topographical predispositions of the nasopalatine canal as a limiting factor for insertion of mid-palatal temporary anchorage devices (TAD). The purpose of the study was to assess the course of the nasopalatine canal, the adjacent vertical bone quantity, and whether it might differ among vertical facial types, using pre-existing cone beam computed tomography (CBCT) scans.
Out of a consecutive sample collected from April 2008 to August 2012, only patient data depicting both upper and lower jaw completely were evaluated retrospectively. The linear measurements were taken on the respective midsagittal view perpendicular to the palate at the level of 1st molar/2nd premolar (5/6), 2nd premolar/1st premolar (4/5), and 1st premolar/canine (3/4). Screen-prints were used to measure the inclination of the nasopalatine canal in relation to the maxillary jaw base. Maxillary and mandibular divergence was assessed on rendered lateral cephalograms.
Out of 3869 pre-existing consecutive CBCT scans, data from 398 patients met the inclusion criteria and could be extracted. The mean vertical bone was 4.09 mm at the 5/6 level, 5.22 mm at the 4/5 level, and 3.14 mm at the 3/4 level, respectively. A statistically significant negative correlation exists between jaw divergence and the canal angulation with regard to the maxillary base. A statistically significant negative correlation exists between the canal angulation and vertical bone measurements at the 4/5 and 3/4 levels.
Vertical bone volume is sufficient at 4/5 level for TAD placement, and bares only a small risk for neuro-sensory impairment. Therefore, only in rare cases a CBCT is justified for palatal implant placement. The course of the nasopalatine canal is negatively correlated with the vertical skeletal facial pattern pointing to the fact that in hypodivergent patients a TAD might be placed in a more distal or paramedian region.
关于鼻腭管的局部解剖学易感性作为腭中临时锚固装置（TAD）植入的限制因素，目前了解甚少。本研究的目的是利用已有的锥形束计算机断层扫描（CBCT）图像，评估鼻腭管的走行、相邻垂直骨量，以及其在不同垂直面型之间是否存在差异。
从2008年4月至2012年8月收集的连续样本中，仅对完整显示上下颌的患者数据进行回顾性评估。在第一磨牙/第二前磨牙（5/6）、第二前磨牙/第一前磨牙（4/5）和第一前磨牙/尖牙（3/4）水平，于垂直于腭部的各自正中矢状面上进行线性测量。使用屏幕截图测量鼻腭管相对于上颌颌骨基部的倾斜度。在数字化侧位头影测量片上评估上下颌的离散度。
在3869例已有的连续CBCT扫描中，398例患者的数据符合纳入标准并可提取。在5/6水平，平均垂直骨量为4.09mm；在4/5水平，为5.22mm；在3/4水平，为3.14mm。下颌离散度与鼻腭管相对于上颌基部的角度之间存在统计学显著负相关。在4/5和3/4水平，鼻腭管角度与垂直骨测量值之间存在统计学显著负相关。
在4/5水平垂直骨量足以植入TAD，且神经感觉损伤风险较小。因此，仅在极少数情况下，腭部种植体植入时才有必要进行CBCT检查。鼻腭管的走行与垂直骨骼面型呈负相关，这表明在低角型患者中，TAD可能放置在更偏远或旁正中区域。
