## 1 Background  
TMJ ankylosis is usually investigated by clinical examination and with imaging studies such as CT or RMI [1; 2; 3; 4; 5]. TMJ ankylosis has been categorized into four different entities by [PERSON] et al., taking into account the severity of the situation and recommending a specific surgical treatment based on the type of the defect: Type I: Presence of fibroadhesions at the condy; Type II: Bone fusion with condyle remodeling and an intact medial pole; Type III: Ankylotic mass, mandibular ramus union with the zygomatic arch and medial pole intact; Type IV: Complete ankylotic mass, total union of the mandibular ramus with the zygomatic arch [6; 7; 8; 9].  
Trauma is the leading cause of TMJ ankylosis globally. In pediatric patients this may be due to falls or even peripartum injuries due to the use of forceps or other obstetric devices, provoking an hemorrhosis mechanism that results in ankylosis [10]. Other etiological factors that can be the cause of this pathological condition are, regardless of age, infections, especially those involving the middle ear, and others, such as rheumatoid arthritis, neoplastic processes, congenital anomalies and recurrent temporomandibular joint ankylosis [11; 12; 13; 14].  
As mentioned before, TMJ ankylosis usually leads to a series of facial deformities due to the impaired mandibular growth processes, such as retrognathia and retrogenia, if bilateral [11; 15; 16].  
If the deformity is asymmetrical and the ankylosis involves just one side, this abnormality of the mandible's growth process commonly progresses because of two factors: the loss of the condylar fibroartilage and the inactivity of the joint itself. The condylar growth cartilage does not represent the primary growth site of the mandible, but it is certainly crucial for the correct development of the condylar head, neck, and the ramus to the angle of the mandible. Similarly to other joints, this inevitably provokes an inhibition of condylar linear and cross-sectional growth.  
There are several surgical techniques that could be applied to treat TMJ ankylis in pediatric patients: Costochondral Grafting; Gap arthroplasty or Interposition Gap arthroplasty; Bone distraction; Coronoidectomies; and Total joint replacement, which is the common final stage correction surgery, both with alloplastic custom-made or stock prosthesis [10; 14; 17; 18]. The timing and the ideal sequence of the various interventions is still debated. This is particularly true in subjects with craniofacial deformations, also syndromic, requiring multiple reconstructive procedures where incidence, risk factors, clinical course and long-term outcomes are mostly unknown. The success of these procedures is determined by the maintenance of maximal incision opening, the prevention of reankylosis and the stimulation of mandible growth [19].  
Here we present a case of a pediatric patient who underwent surgery at our clinic. This patient had already undergone previous surgery to remove the anhydride block and restore the joint functionality, without complete treatment success. It was therefore decided to make her a candidate for a custom-made alloplastic prosthetic reconstruction of the TMJ.