An evaluation of three-dimensional facial changes after surgically assisted rapid maxillary expansion (SARME): an observational study

Abstract

Background: The abnormal facial features in maxillary transverse deficiency (MTD) are minimal and limited to a deficiency of the middle facial third, narrow nares and nasal base, and deepened nasolabial folds. The surgical expansion of the narrow maxilla has most obvious effects on widening of the maxillary dental arch and expansion of the maxillary and palatal structures in the transverse plane, however sagittal changes also occurs. The purpose of this observational study was to evaluate the three-dimensional (3D) facial soft tissue changes following surgically assisted rapid maxillary expansion (SARME).

Methods: In 15 skeletally mature patients with severe maxillary transverse deficiency, the planned maxillary expansion (on average 8.8 mm ± 2.3 mm) was achieved with a bone-borne palatal distractor. The 3D optical scans of the facial surface were obtained before and six months after SARME. In the first part, we defined different anatomical landmarks on both scans and compared cephalometric measurements. In the second part, we registered both 3D scans in the same workplace using the regional best-fit method (forehead, supraorbital and nasal root regions were selected for the superimposition) and conducted surface analysis.

Results: The largest differences between the pre- and post-operation scans were observed in the paranasal and cheek area (1.4 ± 1.0 mm). Significant differences occurred for an increased nasal width, a decreased upper-face height with an unchanged lower height, an increased vertical philtrum height and an increased nasolabial angle. A significant increase in the facial profile angle was also observed, resulting in an increased facial convexity and anterior displacement of the upper-lip area.

Conclusions: The widening of the nose and increased projection in the cheek and paranasal area in the lateral direction after maxillary expansion were confirmed; moreover, facial convexity increases, reflecting the underlying advancement of the maxilla.

Keywords: 3D scanning; Facial scan; Facial soft tissue; Maxillary expansion; Maxillary osteotomy.

Fig. 1

The Synthes transpalatinal distractor we use at our clinic. The image presents the distractor and the site of site of its placement during operation

Fig. 2

Clinical photographs and 3D scans of the patients before surgery (upper raw) and 6 months after surgery (lower raw) showing slight changes in the area of upper lip

Fig. 3

3D facial image with anthropometric landmarks. En face view on the left side and profile view on the right side. In picture 1 presented inner eye distance (enL-enR), outer eye distance (exL-exR), nasal ala width (alL-alR), facial width (zyL-zyR), gonion width (goL-goR), mouth width (chL-chR), intermental width (meL-meR); in picture 2 face height (g-pg), upper face height (g-sn), lower face height (sn-pg); in picture 3 nasal dorsum length (n-prn), nasal tip protrusion (prn-sn), vertical philtrum height (sn-st); in picture 4 facial profile angle (n-sn-pg) and in picture 5 nasolabial angle (cm-sn-ls) and nasal width angle (acL-prn-acR)

Fig. 4

3D facial image with selected parameters in the transverse (1), vertical (2, 3), and sagittal planes (4, 5)

Fig. 5

Left—Facial surface divided into five main areas (1–5) using four horizontal planes. Four vertical planes additionally subdivide areas 2–4 into the central, medial and lateral regions (r-right, c-central, l-left, M-medial, L-lateral. Middle—Color map of the superimposed 3D scans, and color histogram on the right, demonstrating the degree of deviation between the pre- and post-operation facial images of one selected patient. The increased blue saturation corresponds to the positive distance, which is most intensively seen in the paranasal area and in the area superior and lateral to the upper lip and the red saturation corresponds to backward changes

Fig. 6

The mean facial differences between the pre- and post-operative scan in the observed regions in mm (the value presents the sum of displacement vectors for all the points in observed region). The red color presents the areas with backward changes and the grey color the forward changes