# Dento-Skeletal Class III Treatment with Mixed Anchored Palatal Expander: A Systematic Review
## 4 Discussion  
The purpose of this systematic review of the literature was to determine the effectiveness of treating Class III malocclusions using a mixed anchored palatal expander [56]. Due to a scarcity of studies on this issue, only nine publications, largely case series, were chosen for the following work (characterized by a high research specificity and innovative protocol aspect). All of the studies that were analyzed include in their protocol an RME appliance applied on a mini-screw anteriorly in the palate to obtain skeletal anchorage. Since the first molars are also included in the device design, it can be denominated as a bone- and tooth-borne appliance (hybrid hyrax). [PERSON] et al., [PERSON] et al. and [PERSON] et al. [4; 15; 49] employed the Alt-Ramec protocol, which resulted in a more significant disarticulation of the two parts of the maxilla than the other methods of maxillary expansion examined in this research. Because the ability of sutures to respond to therapy decreases with age, it has been suggested that starting maxillary traction with a facemask during the early mixed dentition period (around 8 years old) will provide the most skeletal benefit [47]. Skeletal anchorage, on the other hand, is treated at a later age, around 10 years old, when the characteristics of the bone allow for easier placement and stability [57]. When compared to pure bone-borne RPE devices such as distractors, the hybrid hyrax is surgically minimally invasive, and this is also important to avoid any periodontal inflammation [58; 59; 60; 61]. The use of first molars and mini-screws as, respectively, anterior and posterior anchoring units has various advantages. In fact, according to [PERSON] et al. [29], the hybrid hyrax can be employed even in individuals who have decreased anterior dental anchoring owing to missing primary molars, primary molars with resorbed roots or underdeveloped premolar roots. Moreover, the anterior teeth are excluded in the appliance, and regular orthodontic treatment can, therefore, be started early. Furthermore, in all tests, the miniscrews were implanted at paramedian sites in the anterior palate. This configuration is particularly beneficial for bone availability and safe isolation from vascular and nerve connections. The optimal size and direction of miniscrew insertions are identified on a cone-bean computed tomography (CBCT) scan and a 3-dimensional surgical guide to provide safe and reliable palatal miniscrew insertion [49]. Another significant benefit is that the combination of the hybrid hyrax with a maxillary protraction facemask is helpful to minimize dental adverse effects, such as teeth mesial migration. [PERSON] et al. and [PERSON] et al. [4; 15] specify that the teeth were partially implicated in the maxillary protraction utilizing hybrid hyrax for the transfer of forces to the underlying skeletal systems. The frequent unfavorable consequences of tooth-anchorage devices, such as buccal proclination of the upper incisors and lingual inclination of the lowers, are eliminated with this procedure. As a result, the therapy had both skeletal and dentoalveolar effects (maxilla protraction and mandible posterior displacement). Furthermore, the upper incisors displayed a forward displacement of 3.62 mm (Pr-VertT) and a retroclination of 2.26 degrees in reference to the palatal plane (U1-PP), according to [PERSON] et al. [49]. It is likely that the retroclination found in many patients treated with a bone-anchored facemask or hybrid tooth-skeletal anchoring is due to the treatment's skeletal benefits and the resultant diminution of the no-longer-required denotalveolar compensation. However, despite the anchorage provided by the two mini-screws, [PERSON] et al. [49] assessed the forward movement of the maxillary molars (although by less than 1 mm in all cases). The hybrid hyrax, according to [PERSON] et al. [29], minimized excessive forward movement of the upper molars produced by facemask protraction (1.6 migrated 0.4 \(\pm\) 0.6 mm mesially and 2.6 0.3 \(\pm\) 0.2 mm).