The nasolabial angle is formed by the intersection of a line tangent to the columella and a line along the upper lip. Normative values vary by sex, with women typically presenting more obtuse angles (100–105°) and men more acute angles (90–95°) (6). The nasolabial angle (NLA) is schematically illustrated in Figure 1.

Beyond nasal base inclination, the NLA is strongly influenced by upper lip prominence and maxillary incisor position, making it highly sensitive to orthodontic tooth movement.

Several studies have investigated the effects of orthodontic camouflage treatments—such as premolar extractions and maxillary distalization—on facial profile and the nasolabial angle. As early as the 1980s, Lo and colleagues demonstrated that maxillary incisor retroclination was associated with a significant increase in the NLA when comparing treated and untreated individuals.

While no relevant changes were observed in untreated subjects during growth, the treated group exhibited a clear correlation between incisor retraction and angle opening: on average, each millimeter of maxillary incisor retraction resulted in an increase of approximately 1.63° in the nasolabial angle (7). Similar findings have been reported in extraction-based treatment protocols (8).

These data suggest that dentoalveolar mechanics may significantly influence facial aesthetics, even in the absence of skeletal changes.

Moreover, it should be emphasized that Class II malocclusion is a heterogeneous condition that may result from different skeletal and dentoalveolar patterns, including maxillary protrusion, mandibular retrusion, dental compensations, vertical discrepancies, and, in some cases, altered cranial base morphology. In addition, variations in nasal growth and facial development may further influence the soft tissue profile. Diagnosis and evaluation of treatment effectiveness are commonly based on cephalometric parameters such as the ANB angle, overjet (OJ), and assessment of the spatial relationship between the maxilla and mandible (9). While these measurements are essential for evaluating sagittal correction, they do not fully capture changes occurring in the nasolabial region.

Currently, functional appliances represent the treatment of choice for skeletal Class II malocclusions due to their documented ability to promote mandibular advancement. This forward repositioning improves occlusal relationships—often achieving a Class I molar relationship—and reduces excessive overjet (10).

Nevertheless, their effects are not purely skeletal. Anchorage loss frequently results in retroclination of maxillary incisors and proclination of mandibular incisors (2). While mandibular incisor proclination may reduce the available sagittal advancement, maxillary incisor retroclination may lead to increased nasolabial angle opening.

Despite these clinically relevant soft tissue implications, most studies on functional appliances have focused primarily on skeletal landmarks, particularly changes in pogonion position, with limited and sometimes conflicting evidence regarding modifications of the nasolabial angle (11–13).

Booij et al. compared Herbst therapy with premolar extraction treatment and observed an increase in the NLA in both groups, although the increase was greater in the extraction group (mean 2.3°) compared with the Herbst group (mean 0.7°) (14). Some years later, analogous results werealso reported by Janson et al., who likewise compared Herbst therapy with extraction treatment (15). Although less pronounced, the increase observed with the Herbst appliance remains clinically relevant, particularly in patients with severe overjet, in whom dentoalveolar compensations tend to be more marked.

Different treatment strategies may be adopted to minimize dentoalveolar side effects during functional correction of Class II malocclusion and thereby preserve the nasolabial angle. From a biomechanical perspective, the key objective is to control maxillary incisor retroclination and mandibular incisor proclination, independently of the specific appliance used.

To reduce dentoalveolar side effects, functional appliances are increasingly combined with skeletal anchorage. However, when temporary anchorage devices (TADs) are placed exclusively in the mandibular arch to control lower incisor proclination, reactive forces may be redirected to the maxillary dentition, potentially exacerbating maxillary incisor retroclination.

For this reason, simultaneous anchorage control in both arches appears biomechanically more consistent (16). Miniplate-supported protocols have been proposed, either by anchoring functional appliances directly to mandibular miniplates (17), or by supporting Class II elastics with miniplates in both arches (18).

Although effective, these approaches are relatively invasive and may not be routinely applicable.

A more conservative alternative involves the use of miniscrews as indirect skeletal anchorage combined with functional appliances (19–23).

One possible clinical application of this strategy involves the use of a functional appliance reinforced with miniscrews in both arches. For example, a Herbst appliance incorporating a fixed transpalatal bar and a lower acrylic splint can be reinforced with four orthodontic miniscrews—two in the mandible and two in the maxilla—connected via elastic ligatures delivering approximately 150–200 g of force.

Mandibular miniscrews, placed in interradicular vestibular areas, limit lower incisor proclination in synergy with the acrylic splint. Maxillary miniscrews, whether placed palatally or vestibularly depending on treatment objectives, help prevent upper incisor retroclination and thus contribute to preservation of the nasolabial angle (22–25).

By improving anchorage control, this strategy may allow sagittal correction while minimizing unfavorable soft tissue changes.