Berning Jamie A, Snyder Christopher J, Hetzel Scott, Sarment David P
Midwest Mobile Veterinary Dentistry, Dublin, OH, United States.
Veterinary Dentistry and Oral Surgery, Department of Surgical Sciences, University of Wisconsin-Madison School of Veterinary Medicine, Madison, WI, United States.
Front Vet Sci. 2020 Jan 17;6:485. doi: 10.3389/fvets.2019.00485. eCollection 2019.
The mandibular first molar (M1) tooth of the dog is commonly involved in dental procedures. Tooth roots and the mandibular canal can vary in location, which has not been described on a large scale. The objective of this study was to describe the three-dimensional anatomic relationship of the mandibular M1 tooth roots and the mandibular canal in dogs. Cone-beam computed tomography (CBCT) was used to evaluate the anatomic relationship between the M1 tooth roots and the mandibular canal. CBCT images were collected from 101 canine cadaver heads from a variety of unknown breeds. All skulls used in this study were mesaticephalic, confirmed by facial index calculations. The position of the apex in relation to the mandibular canal and in relation to the buccal and lingual cortices was recorded and analyzed in relation to mandibular bone height: root length ratio. When evaluating the apex in a buccal-lingual relationship, the tooth roots were found to be located closer to the lingual cortex in 73.3% of M1 roots. Tooth root apical positions were found to be symmetric between the right and left side of the mouth in 93% of mesial roots and 95% of distal roots. Apical positions relative to the mandibular canal within the same tooth were found to be consistent in 52% of teeth. Teeth with roots dorsal to the mandibular canal were associated with the largest mandibular bone height: root length ratio. CBCT provides a more precise overview than dental radiographs of three-dimensional anatomy. The tooth root position can be estimated in a clinical setting based on the ratio of mandibular bone height to tooth root length obtained from intraoral radiographs. Understanding the relative location of important anatomic structures is key to avoiding complications associated with various dental procedures. This study has documented that assessing anatomic structures with 2D imaging alone is flawed, and the large majority of dogs have M1 roots closer to the lingual aspect than the buccal aspect of the mandible.
犬的下颌第一磨牙（M1）通常涉及牙科手术。牙根和下颌管的位置可能会有所不同，但尚未有大规模的描述。本研究的目的是描述犬下颌M1牙根与下颌管的三维解剖关系。采用锥形束计算机断层扫描（CBCT）来评估M1牙根与下颌管之间的解剖关系。从101个来自各种未知品种的犬类尸体头部采集CBCT图像。通过面部指数计算证实，本研究中使用的所有头骨均为中头型。记录并分析根尖相对于下颌管以及相对于颊侧和舌侧皮质的位置，并与下颌骨高度：牙根长度比相关联。在评估根尖的颊舌关系时，发现73.3%的M1牙根更靠近舌侧皮质。在93%的近中牙根和95%的远中牙根中，发现牙根尖位置在口腔的左右两侧对称。在52%的牙齿中，同一颗牙齿内根尖相对于下颌管的位置是一致的。牙根位于下颌管背侧的牙齿与最大的下颌骨高度：牙根长度比相关。与牙科X光片相比，CBCT能提供更精确的三维解剖概况。在临床环境中，可以根据从口腔X光片中获得的下颌骨高度与牙根长度的比值来估计牙根位置。了解重要解剖结构的相对位置是避免各种牙科手术相关并发症的关键。本研究证明，仅用二维成像评估解剖结构存在缺陷，并且绝大多数犬的M1牙根更靠近下颌骨的舌侧而非颊侧。
