This guest blog explores the principles of incisor positioning, the fundamental in orthodontic treatment planning that directly influences aesthetic and stability outcomes. While the principles behind incisor positioning and its impact on space requirements have guided clinicians for decades, they remain scattered across research and clinical training. This blog, and subsequent series of blogs, consolidates these principles. This blog will explore radiographic and clinical targets for planned incisor position and examine optimal incisor inclination, with key guidelines for each topic based on hallmark orthodontic references.
The blog is part of a series of blogs on the Mathematics of Orthodontics by Daniel Richmond, an orthodontist from Ontario, Canada I came across on social media. Daniel has put together an innovative online resource for orthodontic space analysis, the Ortho Calculator, I found the website interesting and very useful in terms of ensuring a structured and comprehensive orthodontic assessment for space planning (I have no conflict of interest).
In an era where artificial intelligence can align teeth with the click of a button, what sets the orthodontist apart as true specialists? Basic alignment of contact points is a given, but the ability to precisely position the incisors in three planes of space is what leads to both functional excellence and facial harmony (Gianelly, 1995; McLaughlin et al., 2001). A well-positioned incisor contributes to enhanced anterior esthetics, which is ultimately what drives patients to seek orthodontic care (Dimberg et al., 2015). This raises a question: where exactly should the incisors be positioned?
Cephalometric analyses have long been used to determine the ideal anteroposterior (AP) position of the incisors, typically by measuring the incisal edge relative to skeletal landmarks (Ellis & McNamara, 1986). While norms from Steiner or Downs offer a standardized reference, they are based on averages that may not adapt well to patients with jaw discrepancies—particularly Class II and Class III skeletal patterns.
A more flexible approach is the Simplified Radney Analysis, as described by Creekmore. This method stems from Radney’s observation that the edges of the lower incisors (L1s) consistently align with the NA line regardless of skeletal pattern (Creekmore, 1997). Based on this, the recommendation is that L1s should be positioned 0.5 mm ± 2 mm to the NA line, and the upper incisors (U1s) should be positioned 5 mm ± 2 mm anterior to the NA line (Figure 1).
Figure 1. Simplified Radney Analysis on a Class I patient.
The ranges reflect the role of dental compensation in achieving ideal overjet. In Class II cases, the U1-NA distance decreases, and in Class III cases, it increases. This pattern intuitively mirrors the goal of camouflaging underlying skeletal imbalances. This aligns with the findings of Casko and Shepard, who described the adaptive nature of dental compensation across skeletal patterns in untreated patients with ideal occlusions (Figure 2) (Casko & Shepherd, 1984).
Figure 2. Simplified Radney Analysis on a Class II and Class III patient illustrating the L1s falling on the NA line in both cases. (Adapted from Casko and Shepard).
By relating upper and lower incisors to a maxillary reference point, this method supports individualized treatment planning rooted in facial balance and natural dental compensation. It also offers practical efficiency as it requires only one reference line to evaluate planned incisor position.
Guideline: Planned U1 position = just ahead of the NA line (to achieve ideal overjet)
Though cephalometric analysis is foundational in treatment planning, it should be complemented by clinical evaluation to capture the full esthetic picture. This is where soft tissue reference points become particularly valuable. There is consensus regarding the AP position of the U1s relative to facial soft tissue landmarks. Andrews introduced the forehead’s facial axis (FAA) as a reference, emphasizing the role of the forehead in planning incisor position (Andrews, 2008). He proposed positioning the U1s anterior to the FFA point and posterior to glabella.
While this concept sparked meaningful discussion and advanced soft tissue-driven planning, its reliance on forehead morphology can be somewhat cumbersome in clinical use.
Subsequent research has built upon this concept and consistently supported a glabellar vertical line (GVL) as a practical and reliable clinical reference line for achieving esthetically optimal incisor placement (Adams et al., 2013; Carruitero et al., 2019; He et al., 2019). Studies evaluating profile esthetics suggest that incisors positioned on or just behind GVL are generally rated as the most balanced and harmonious (Figure 3). Naini elaborates on this, noting that U1s should align approximately with a true vertical line dropped from soft tissue nasion, glabella, or a midpoint between the two—with variation depending upon the morphology of the nasal-glabellar region (Naini & Gill, 2017).
Racial and ethnic differences may also influence ideal position, with research supporting a more protrusive U1 position in Asian and Black populations (Cho et al., 2021; Gidaly et al., 2019). Nevertheless, using GVL as a reference in a smiling profile photograph offers a stable and reproducible guide for planning upper incisor position in harmony with facial structure.
Guideline: Planned U1 position = on or just behind GVL
Figure 3. Clinical assessment of U1 position in the AP plane relative to GVL.
We have established the ideal AP position of the incisors, but their inclination also plays a critical role. Although many cephalometric norms exist to guide incisor inclination, they are heavily influenced by skeletal anatomy and can become misleading if individual variation and facial morphology are not considered (Arnett & Bergman, 1993; Ellis & McNamara, 1986; Naini et al., 2019).
To ensure a clinically esthetic result, incisor inclination should be assessed in the context of the patient’s smile in natural head position. Whether assessed on a cephalometric radiograph or in smiling profile photographs, studies consistently show that when in natural head position, U1s that are parallel to a true vertical line (TVL) are perceived as the most esthetic (Figure 4) (Ghaleb et al., 2011; Naini et al., 2019). Excessive proclination is generally viewed as less desirable than slight retroclination.
Guideline: Labial surface of U1 = parallel to TVL
Figure 4. Assessment of U1 inclination relative to TVL.
This target works best for Class I, normocephalic patients. For Class II or Class III cases, dental compensation of incisors becomes necessary not only in the AP plane, but also in terms of inclination. Inclination targets must therefore be adjusted to camouflage disproportionate jaw relationships and achieve ideal overjet; in Class II cases, U1s are typically more retroclined, and in Class III cases, they often finish more proclined. L1s follow the opposite trend (Figure 5) (Casko & Shepherd, 1984; Creekmore, 1997).
Figure 5. Changes in incisor inclination reflecting dental compensation.
This second section explored incisor positioning in orthodontic diagnosis and treatment planning, outlining radiographic and clinical guidelines for achieving optimal AP position and inclination. It highlighted how these targets must adapt to skeletal discrepancies and facial morphology to achieve balanced esthetics and functional harmony.
The next blog will explore how planned incisor position influences space requirements and connects with the broader mathematical framework of treatment planning.
Contents: Daniel Richmond 
Visit the Ortho Calculator at www.orthocalculator.org/
REFERENCES
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1 comment
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