## 1 Introduction  
Skeletal Class II can result from maxillary prognathism, mandibular retrognathism, or their combination. Dental characteristics often include the relationship of the upper first permanent molars and canines with their antagonists in Class II, the protrusion of the upper incisors, a mainly decreased overbite, and a narrow maxilla with a high palate, which can result in a bilateral crossbite; in Class II, division 2, upper incisors are retruded. Additionally, the presence of an open or deep bite, adenoid vegetations, tonsillar hypertrophy, and functional disorders such as mouth breathing and infantile swallowing may be observed [1, 2, 3]. Functional appliances are frequently used during the growth phase to encourage the forward movement of the lower jaw. They have shown short-term success in correcting Class II malocclusions by decreasing overjet mostly due to tipping of the lower front teeth [4]. Several appliances play a crucial role in modifying mandibular growth. Traditional appliances such as Twin Block and Herbst and the various activators are commonly used [5]. The Herbst appliance uses a telescopic rod to advance the mandible while also preventing the maxilla from moving forward, while the Twin Block appliance uses upper and lower plates to reposition the mandible forward. The activator-type appliances apply masticatory muscles' forces to move the mandible forward. Additionally, advancements in orthodontics have led to the development of functional clear aligners which can include mandibular advancement elements like custom attachments and elastic [6]. These studies mainly measured effects on hard and soft tissues using lateral ceps, and not soft tissue scans. Our study focuses on therapy with the functional Twin Block appliance and the impact of this therapy on soft tissue, with traditional cephalometric characteristics used to demonstrate effects of Twin Block therapy. The goal of the therapy, depending on the dental and skeletal characteristics of the patient, is to create more harmonious skeletal and soft tissue relations. The skeletal effect of the Twin Block appliance is the increase in the total length of the mandible, the increase in the height of the ascending ramus, and the posterior direction of the condylar growth [7]. Dentoalveolar changes that can be observed include the retrusion of the upper incisors and protrusion of the lower incisors, and reduction in overbite. Additionally, there is extrusion of the lower molars, which increases the vertical dimension of the occlusion [8]. Soft tissue changes are reflected in an increase in the height of the lower third of the face, and the forward movement of the lower lip and chin, which ultimately results in an improved facial profile appearance [8; 9]. Research has also confirmed a significant reduction in facial convexity, lip incompetence, and protrusion of the upper lip, and the inclination of the columellar line [9]. Three-dimensional (3D) facial scanning has emerged as a reliable and efficient method for assessing changes in facial soft tissues. Combined with artificial intelligence (AI)-based analysis, facial scanning is emerging as a powerful approach for early disease detection [10]. Beyond internal structural and functional abnormalities, many diseases are associated with distinctive craniofacial features. These facial phenotypes can serve as clinically relevant biomarkers, particularly in the diagnosis of genetic syndromes, metabolic disorders, and neuromuscular conditions [10]. Compared to conventional imaging techniques, 3D facial scans capture the entire face without radiation exposure or angular distortion, enabling the precise quantification of linear and angular distances, area superimposition, and volumetric analysis [11; 12]. A high degree of precision and accuracy is making 3D facial scans suitable for monitoring in orthodontic practice.