--- title: "Lower Lip S-Line Position in FaceIQ Labs Harmony Analysis: What It Measures" description: "FaceIQ Labs' Lower Lip S-Line Position is the lower lip's signed distance from a line running from the nose-base/tip midpoint to the soft-tissue chin, on the side view." canonical: "https://appear.faceiqlabs.com/support/harmony/lower-lip-s-line-position" --- # Lower Lip S-Line Position in FaceIQ Labs Harmony Analysis: What It Measures Lower Lip S-Line Position is a side-view, lips-region Harmony measurement in FaceIQ Labs: the lower lip's signed perpendicular distance from the S-line, which runs from the midpoint of the nose base and tip to the soft-tissue chin. Negative means the lip is in front of the line, positive means behind, and zero means contact. ## Key facts - The measurement is the perpendicular lower-lip distance to the S-line multiplied by the photo scale. - In FaceIQ, negative means the lip lies in front of the line; positive means it lies behind the line; zero means contact. - FaceIQ Labs approximates the S-line's nasal endpoint as the midpoint between the nose base and nose tip; the line runs to the soft-tissue chin. - Millimeter values are estimates: FaceIQ scales the photo using an assumed 190 mm hairline-to-chin height. - The S-line concept comes from Steiner's soft-tissue profile analysis; FaceIQ's midpoint-based version may differ from tracing the original nasal S-curve. - The guide's example values (+2 mm, 0, −1 mm) illustrate the calculation and are not a target range. - FaceIQ Labs standardizes side photos to the Frankfort horizontal plane during landmarking. - The guide cites Buschang, Fretty & Campbell (2011), which compared five lip reference lines in 79 orthodontic patients. ## What does Lower Lip S-Line Position measure? Lower Lip S-Line Position in FaceIQ Labs' Harmony analysis is the signed distance from the lower lip to the S-line, a reference line running from the midpoint between the nose base and nose tip to the soft-tissue chin. It is calculated on the side view as the perpendicular lower-lip distance to that line multiplied by the photo scale. ## How do I read a negative, positive or zero value? - Negative in FaceIQ Labs: the lower lip lies in front of the S-line. - Positive in FaceIQ Labs: the lower lip lies behind the S-line. - Zero: the lower lip touches the S-line. - The guide's example values are illustrative and are not a target range. ## Why does the lower lip's position relative to the S-line matter? FaceIQ Labs uses Lower Lip S-Line Position to relate the lower lip to the nose–chin framework of the side profile. Reading it alongside Upper Lip S-Line Position helps show how each of the two lips relates to the same reference line, rather than judging one lip alone. ## Where does the S-line come from and how does FaceIQ Labs adapt it? The S-line is Steiner's line from soft-tissue profile analysis. FaceIQ Labs adapts it by approximating the nasal endpoint with the midpoint between the nose base and nose tip. The guide notes this construction may differ from tracing the original nasal S-curve, so the result approximates the classic line. ## Where does this measurement sit in FaceIQ Labs' analysis? Lower Lip S-Line Position is a side-view, lips-region measurement in the Harmony pillar of FaceIQ Labs, which measures 70+ facial ratios and angles compared to ideal ranges adjusted for gender and ethnicity. Side photos are standardized to the Frankfort horizontal plane during landmarking, and Harmony is weighted roughly 60% front photo and 40% side photo. ## What does a worked example of Lower Lip S-Line Position look like? FaceIQ Labs gives one worked example: a lower lip an estimated 2 mm behind the S-line reads +2 mm. Moving it onto the unchanged line gives zero, and a lip 1 mm in front of the line gives −1 mm. These values explain the calculation; they are not a target range. ## How accurate are the millimeter values for Lower Lip S-Line Position? The millimeter values for FaceIQ Labs' Lower Lip S-Line Position are estimates, not calibrated physical measurements. FaceIQ scales the photo using an assumed 190 mm hairline-to-chin height. A midpoint-based S-line is also an approximation, and lip posture or movement of either endpoint changes the distance; the measure does not isolate tooth position. ## What research does the Lower Lip S-Line Position guide cite? The FaceIQ Labs guide cites one source: Buschang, Fretty & Campbell (2011), 'Can commonly used profile planes be used to evaluate changes in lower lip position?' It compared five lip reference lines, including Steiner's S-line, in 79 orthodontic patients, and found that moving reference points can make a lip appear to move backward even when it moves forward. ## Does research validate FaceIQ Labs' scoring for this measurement? No. FaceIQ Labs states that its score weights and reference ranges are model settings, and that the papers cited in the Lower Lip S-Line Position guide explain history or related evidence but do not collectively validate the scoring system. ## What other lip measurements are in FaceIQ Labs' Harmony guides? - Upper Lip S-Line Position - Lower Lip E-Line Position - Upper Lip E-Line Position - Lower Lip Burstone Line - Upper Lip Burstone Line - Holdaway H Line - Mentolabial Angle ## Frequently asked questions ### Does a negative Lower Lip S-Line Position value mean my lip is worse? The FaceIQ Labs guide does not say negative values are worse. It defines negative as the lip lying in front of the S-line and positive as behind it, with zero meaning contact, and says its example values are not a target range. ### Is the millimeter value for lower lip position an exact measurement? No. FaceIQ Labs scales the photo using an assumed 190 mm hairline-to-chin height, so the values are estimates rather than calibrated physical measurements. ### How does FaceIQ Labs' S-line differ from Steiner's original S-line? FaceIQ Labs approximates the nasal endpoint as the midpoint between the nose base and nose tip, rather than tracing the original nasal S-curve. The guide notes this construction may differ from the original. ### Which line is the lower lip measured against? The S-line, which runs from the midpoint between the nose base and nose tip to the soft-tissue chin. The lower lip's perpendicular distance to it is multiplied by the photo scale. ### Does this measurement isolate tooth position? No. FaceIQ Labs says lip posture and movement of either line endpoint change the distance, and the measurement does not isolate tooth position. ## Pages on this host This is one page of several on this host. 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