Facemask therapy induces forward displacement of the maxilla and decreases forward displacement of the mandible. This is accomplished by stimulating cellular activity in circummaxillary sutures and the maxillary tubercle [19, 20]. Although conventional facemask therapy has proven to be an efficient method for treating skeletal class III malocclusion, because of unwanted dentoalveolar effects of conventional tooth-borne face masks, there have been numerous attempts to develop a method of skeletal face mask anchorage. Kokich et al. used an intentionally ankylosed deciduous tooth as an anchor point, Singer et al. and Enacar et al. introduced osseointegrated implants as anchors, Hong et al. placed a hexagonal implant in the palatal bone and used this as an anchor point, Kircelli and Pektas inserted two miniplates in the lateral nasal wall of the maxilla and placed elastics in the hooks of the miniplates, and De Clerck et al. used two miniplates inserted in the infrazygomatic crest and two miniplates inserted between the canine and the first premolar in the mandible as anchors [12, 21–25].
In SAFM protocol, there are some controversies about proper magnitude of maxillary protraction force. Nguyen et al. . applied initial force of 100 g on each side and increased force up to 200 g after 1 month. But Sar et al.  delivered protraction force of 400 g on each side and acquired proper maxillary advancement. Some clinicians think that elastic force of 400 g on each side is insufficient and need even more force for adequate maxillary protraction, but there is lack of substantial studies about proper protraction force.
The relationship between facemask therapy and airway volume increase has been widely investigated [16, 17, 26, 27]. However, controversy remains concerning the effectiveness of facemask therapy on airway dimension increases. Hiyama et al. and Kaygisiz et al. reported that pharyngeal airways improved after correcting maxillary retrusion by facemask therapy [16, 17]. On the other hand, Baccetti et al. and Mucedero et al. found that there were no significant increases in pharyngeal airway volume after face mask therapy [26, 27]. In the present study, we observed increases in pharyngeal airway volume after treatment in both groups of patients.
This study used a modification of Kircelli’s miniplate anchorage system because of its relative simplicity and effectiveness. Conventional miniplates used to treat trauma patients were initially employed, but screw loosening and plate detachment from the maxilla happened frequently because of the bone flexibility in young patients. So, the fixation system was changed to a locking system in order to increase stability and make screw loosening less likely. However, our plate and screw fixation method still has some disadvantages. Although we used locking fixation system, there was one patient who showed loosening of miniplate and consequently needed removal of miniplate and re-operation was performed just lateral to former position. According to Sar et al. , loosening of miniplate were up to 7% and in that case, the miniplate should be replaced. In addition to screw loosening, these miniplates were not designed for skeletal anchorage, they need to be modified preoperatively. Another disadvantage involves the hook at the last hole. This hook has internal threads for the locking system. Although surgeons smooth the threads before placement, some sharp edges remain, which can cause the elastics to break. These problems originate from the fact that we used miniplates designed for trauma or orthognathic surgery. If this skeletal anchorage method gains popularity, a plate and screw system optimized for this purpose could be created.
Changes in airway measurements were assessed using lateral cephalometric radiographs. Although lateral cephalograms can only provide two-dimensional information, they have been used to efficiently analyze pharyngeal airway spaces. Not only are they simple and easy to use but there is also a significant correlation between airway space measured with a lateral cephalogram and measured with computed tomography according to Riley and Powell . Various studies have used lateral cephalometric films to investigate pharyngeal airway changes. It is widely accepted that there is a correlation between head posture and pharyngeal airway volume [16, 29]. Therefore, all lateral cephalometric radiographs should be taken with the head in a natural position, and the cephalometric films used in this study were taken following standard rules.
One limitation of this study is that it lacks a control (untreated) group. Comparison of linear and areal measurements between a control group and TBFM and SAFM groups would be ideal. However, in order to acquire cephalometric radiographs of control subjects, patients with skeletal class III malocclusion would have to be left untreated, which causes an ethical dilemma. Also, the study involves exposure to radiation, which is another ethical issue. Fortunately, there is precedence for carrying out studies of this nature without an untreated control group.
Airway passages usually expand as individuals grow up. Some authors have conducted research on the correlation between physical growth and pharyngeal airway volume [30–34]. According to Taylor et al., most posterior pharyngeal wall growth occurred in two spurts, from 6 to 9 years of age and from 12 to 15 years of age; growth of airways in individuals 9 to 12 years old is very limited . The subjects in the current study consisted of 20 boys and 32 girls, with a mean age of 10.7 years and a mean treatment time of 15.5 months. Therefore, we can assume that the extent of natural pharyngeal airway growth in these subjects would be insignificant and the airway increases we observed was induced by face mask treatment.
Both the TBFM and SAFM groups showed increased pharyngeal airway measurements after treatment, but the SAFM group showed statistically significantly greater increases than did the TBFM group in four measurements. The SAFM subgroups had greater SPPA and IPA increases than did the TBFM subgroups. These findings suggest that SAFM therapy is more effective than TBFM therapy for increasing airway volume.
It is uncertain why the upper airway space increased by maxillary protraction. Some possible explanations are as follows. First, the protraction force of the face mask may induce forward movement of the maxilla, especially PNS; this could cause anterior displacement of the soft palate and consequently increase upper airway space . Second, the anterior position of the tongue is altered by facemask treatment. This may be induced by increased volume of the oral cavity or by clockwise rotation of the mandible. The altered tongue posture could lead to an anterior shift of the soft palate and increased upper airway space .
Recently, pediatric obstructive sleep apnea (OSA) has attracted a great deal of attention. Many treatment modalities are available for pediatric OSA. Some authors proposed that maxillary protraction can be a solution for OSA . Hiyama et al.  suggested that maxillary protraction appliances could contribute to improvements in respiratory function in patients with maxillary hypoplasia. Similarly, Hüsamettin et al.  implied that maxillary protraction could alleviate respiratory discomfort in patients with maxillary retrusion, and Verse et al.  found that intraoral devices were effective in approximately 50–70 percent of patients with obstructive sleep apnea. Conley  evaluated the effects of dental treatment in pediatric patients with obstructive sleep apnea. According to that study, maxillary protraction with palatal expansion has the potential to treat pediatric OSA patients. However, there are still an insufficient number of studies on the effects of maxillary protraction on treatment outcomes of OSA, such as measurements of polysomnography. Given the results of the current study, increased upper airway dimensions resulting from use of SAFM could contribute to the treatment of pediatric OSA. Unfortunately, none of our subjects reported a history of OSA, so further studies using specific measurements of OSA are needed in order to evaluate SAFM as a treatment for OSA.