台灣成年人上顎正中門牙與額頭標誌點間最佳前後位置關係之研究

Abstract

顏面協調性的評估對於齒顎矯正與正顎手術的治療規劃具有關鍵性的影響，其中上顎與上門牙的前後位置（antero-posterior position, AP position）為重要參考指標。許多學者提出各種方法來決定上顎的前後位置，包括以中臉部和嘴唇的相對關係（E line, S line, B line）或是額頭輪廓的定位點（glabella, nasion）來作為決定上顎前後位置的參考。然而這些方法的準確性與臨床實用性仍具爭議。此外，目前常用之分析方法多源自歐美族群，對於台灣華人的適用性尚待驗證。 本研究旨在探討台灣華裔成人中，額頭與上門牙間是否存在穩定的前後關係，並比較不同參考平面：法蘭克福平面（Frankfurt horizontal plane, FH plane）與自然頭導向位（natural head orientation, NHO），及不同軟組織定位點，軟組織眉間（soft tissue glabella, STG）與軟組織鼻根（soft tissue nasion, STN），於正顎手術規劃之應用潛力。本研究分為三個部分，第一部分針對上顎與上門牙位於前後位置合宜的病人，共收案30位台灣華裔成人（15男15女），收案後蒐集其X光與臨床側臉照，利用2D軟體以額頭至鼻尖輪廓對齊，調整至NHO，並匯入Dolphin軟體標記標誌點，同時在NHO及FH plane下量測上顎正中門牙（U0）至軟組織眉間垂直線（soft tissue glabella vertical, STGv）與軟組織鼻根垂直線（soft tissue nasion vertical, STNv）在水平面的距離。第二與第三部分則收案上顎明顯前突或後縮病人各30位，方法類似，但僅在NHO進行分析。研究結果顯示，在NHO上所建立的兩條垂直參考線：STGv與STNv，皆能有效區分前後位置合宜的上顎，與過度前突或後縮上顎間的差別，其中上門牙與軟組織眉間垂直線的距離（U0-STGv）相較於上門牙與軟組織鼻根垂直線的距離（U0-STNv）具更高之診斷準確性與一致性。在上顎前後位置合宜的組別，男女平均U0-STGv=-5.4 mm，男生平均U0-STGv=-6.0 mm，女生平均STGv=-4.8 mm。以STNv為參考線的話，男女平均U0-STNv都很接近-0.9mm。研究同時分析了U0-STGv和U0-STNv在區分上顎合宜、前突與後縮狀態時的臨界值，提供具體且量化的數據，作為正顎治療規劃的參考。區分上顎前突和上顎前後位置合宜的臨界值，男女平均為U0-STGv=-3.05 mm、U0-STNv=1.85 mm。女性平均為U0-STGv=-2.2 mm、U0-STNv=3.9 mm。男性平均為U0-STGv=-3.3 mm、U0-STNv=1.85 mm。區分上顎後縮和上顎前後位置合宜的臨界值，男女平均為U0-STGv=-7.4 mm、U0-STNv=-2.1 mm。女性平均為U0-STGv=-6.2 mm、U0-STNv=1.8 mm。男性平均為U0-STGv=-8.9 mm、U0-STNv=-5.0 mm。建議未來擴大樣本規模並結合三維影像進行驗證與補強，以提升其準確性與臨床可用性。

Assessment of facial harmony plays a critical role in the treatment planning of orthodontic and orthognathic procedures, with the antero-posterior (AP) position of the maxilla and upper incisors being a key diagnostic parameter. Various methods have been proposed to determine the AP position of the maxilla, including those based on the relative position of the midface and lips (e.g., E-line, S-line, B-line) or forehead-based landmarks (e.g., glabella, nasion). However, there are concerns regarding the accuracy and clinical applicability of these approaches. Moreover, many of these methods are developed from Western populations, and their relevance to Taiwanese individuals remains to be validated. This study aimed to investigate whether a stable AP relationship exists between the forehead and upper incisors in Taiwanese adults. We also evaluated the clinical utility of different reference planes, the Frankfurt horizontal (FH) plane and natural head orientation (NHO), and various soft tissue landmarks, soft tissue glabella (STG) and soft tissue nasion (STN), for orthognathic treatment planning. This study included three parts. The first part analyzed 30 Taiwanese adults with ideal AP maxillary positions. Lateral cephalograms and profile photos were aligned to NHO, then analyzed using Dolphin software. The horizontal distances from the upper incisor tip (U0) to soft tissue glabella vertical (STGv) and soft tissue nasion vertical (STNv) were measured under both NHO and FH plane. The second and third parts used the same method for patients with maxillary protrusion or retrusion 30 patients with retruded maxilla but analyzed only under NHO. Results demonstrated that two vertical reference lines established under NHO, STGv and STNv, can effectively distinguish between optimal, protrusive, and retrusive maxillary positions. Among them, the distance from the upper incisor to STGv (U0-STGv) showed superior diagnostic accuracy and consistency compared to the distance from the upper incisor to STNv (U0-STNv). In the group with optimal maxillary position, the mean U0-STGv distance was –5.4 mm, with males averaging –6.0 mm and females –4.8 mm. Using STNv as the reference, the mean U0-STNv distance was close to–0.9 mm for both genders. The study also identified threshold values for U0-STGv and U0-STNv in the differentiation between optimal, protrusive and retrusive maxillary positions, providing quantitative and specific references for orthognathic treatment planning. The threshold values distinguishing maxillary protrusion from optimal AP position were, on average, U0-STGv = –3.05 mm and U0-STNv = 1.85 mm for both genders. For females, the thresholds were U0-STGv = –2.2 mm and U0-STNv = 3.9 mm; for males, U0-STGv = –3.3 mm and U0-STNv = 1.85 mm. To differentiate maxillary retrusion from optimal AP position, the mean thresholds were U0-STGv = –7.4 mm and U0-STNv = –2.1 mm for both genders. Specifically, females had thresholds of U0-STGv = –6.2 mm and U0-STNv = 1.8 mm, while males had U0-STGv = –8.9 mm and U0-STNv = –5.0 mm. Further research with larger sample sizes and incorporation of three-dimensional imaging is required to enhance the accuracy and clinical applicability of these findings.