**3. Options for TMJ reconstruction in patients with dentofacial deformities**

TMJ reconstruction can generally be achieved by using two basic methods:


Autogenous materials are popular for TMJ reconstruction in pediatric patients (especially costochondral graft) due to their growth capacity. However, the unpredictability of growth is a problem (excessive growth or no growth), as well as unpredictable bone graft stability and donor site morbidity. The use of allogenous materials is not suitable for TMJ reconstruction with concurrent orthognathic surgery [11–13].

Allogeneic prostheses can be partial or total.

Partial replacement (typically a prosthetic replacement of the mandibular condyle, which is inserted into the joint fossa) is again not a suitable for DFD. The longterm use of these prostheses is associated with an increased risk of fossa resorption due to direct contact of the head of the prosthesis with the bone fossa [13].

The ideal solution for TMJ reconstruction with DFD is total joint replacement (TJR). Total joint replacement consists of [14, 15]:


Total prostheses are available in two versions- stock prostheses and patient-fitted prostheses [15, 16].

Stock prostheses are usually manufactured in several sizes, with the ideal size of prosthesis components selected during surgery [16]. If these prostheses are used in orthognathic surgery, it must be kept in mind that this is an altogether compromise solution. Stock prostheses have the same shape and mandibular advancement is usually only achieved as a result of the inappropriate distal inclination of the prosthesis, or by moving the prosthesis behind the posterior branch of the mandible. An ideal result can only be achieved by using patient-fitted prostheses, whose shape is designed to concurrently allow the planned repositioning of the lower jaw (**Figure 1**). Another advantage of patient-fitted prostheses is their improved fit and osseointegration, thus resulting in less friction and micromovement, better stability and potentially longer mean durability [17, 18]. When the zygomatic arch and glenoid fossa were absent, the

#### **Figure 1.** *TMJ prosthesis design enabling mandibular advancement.*

fossa component was custom-fitted to the base of the skull and lateral temporal bone morphology [11] (**Figures 2** and **3**).

Relative contraindications of alloplastic total TMJ replacement are [19, 20]:

1.uncontrolled systemic disease

**Figure 2.** *22 years old man with HFM (absence of joint structures and absence of zygomatic arch).*


Today, the previously unequivocal refusal to use TJR in pediatric patients with a growing skeleton [14] is changing, as it is no longer considered an unsuitable indication [21, 22]. Growth activity of the mandible is observed when employing TJR even in growing skeletons [21]. The use of TJR of the TMJ in children is possible in the following indications [21]:


#### **Figure 3.** *22 years old man with HFM (planned reconstruction of joints structures and zygomatic arch).*


It must be realized that TJR is joint replacement that is not equivalent to the physiological joint. TJR does not allow the same movement as the physiological joint. The components of the prosthesis mainly allow rotational movement, while the physiological joint allows rotation, as well as translational movement. Joint replacements only exhibit slight translation (pseudo-translation), which causes deviations in mouth opening in unilateral TJR (movement deviates to the side of the TJR). Some authors report improved translational movement when performing lateral pterygoid muscle reattachment [23, 24].
