### Relationship between Speech Sound Disorders and Malocclusion  
Within the general population, 4.9% of adolescents and 3.5% of adults have speech-sound disorders (SSDs) [24; 25]. However, among DFD patients, a noTable 90% of Class III patients, 83% of AOB patients, and 73-87% of Class II patients present with SSDs [4; 26]. Patients with DFD present with a biological or organic impediment to proper speech, akin to a motor speech disorder. However, SSDs in DFD patients result not from a neurological or muscular pathology but from structural abnormalities in their vocal tract, particularly within the oral cavity. As a result, we describe patients with DFD as having structural SSDs, with obligate speech errors and distortions due to abnormal oral and vocal tract anatomy. The large discrepancy in prevalence of articulation pathologies between DFD subjects and the general population suggests a direct relationship between speech distortion and severe malocclusion. The interaction between speech, malocclusion, and its correction is an area of active investigation, with implications for the clinical management of DFD patients with SSDs [26]. Understanding the principles of speech pathology and its presentation and management in DFD patients is relevant for speech-language pathologists (SLPs), orthodontists, and oral and maxillofacial surgeons (OMFSs). OMFS and orthodontic providers manage care for DFD patients over years and are uniquely positioned to evaluate malocclusion severity and detect speech issues for proper referral and interdisciplinary management with SLPs early in development. Figure 1: Tongue posture in DFD patients pre and postoperatively. **(A)** In DFD patients with AOB, the tongue tip is positioned more anteriorly, commonly resulting in a lisp [19; 20; 21]. **(B)** In Class II DFD patients, the back of the tongue is positioned more posteriorly in the oral cavity [22]. **(C)** In DFD patients with Class III malocclusion, the tongue appears to have a flatter surface because these patients present with a larger mandible [23]. **(D)** After orthognathic surgery, the maxilla and mandible are in a Class I skeletal relationship and anterior tooth relationships show a proper 2 mm overbite and 2 mm overjet. Tongue positioning changes postoperatively, relative to the preoperative position seen in the DFD groups. In the AOB group, the tongue placement becomes more posterior due to the positive overbite. In the Class II population, the tongue moves more anteriorly due to the mandible being advanced during surgery [22]. Postoperative DFD patients with Class III correction demonstrate increased tongue height, with a resting position against the palate and the tip of the tongue touching the lingual surface of the anterior upper incisors and the anterior palate [23]. Muscle origin and insertion points are shown by hash marks on the hyoid bone and mandible in **(D)**. The genioglossus (GG), hyoglossus (HG), and styloglossus (SG) represent the lingual musculature and are indicated by lines with dots at the tip. The floor of the mouth muscles includes the phylhoyoid (MH) and geniohyoid (GH), both indicated by arrows. Insertion and origin points are consistent before and after orthognathic surgery. Figure 2: Clinical presentations of Class I AOB, II and III malocclusions in DFD patients. (**A**) Lateral cephalogram (ceph.) radiograph showing a DFD patient with a skeletal and dental AOB, with a posteriorly tipped maxillary palatal plane, a high mandibular plane angle, increased lower facial height, and two planes of occlusion in the maxillary dentition. (**B**) Ceph.