# A Brief Review on Micro-Implants and Their Use in Orthodontics and Dentofacial Orthopaedics
## 3 Results
### Use in Orthodontic Clinical Practice and Dento-Facial Orthopedics
The anterior palatal bone was significantly thicker in males than females in the anterior palate, whilst in the posterior palate there was no significant sex-related difference. The thickness tended to decrease in the posterior direction, except in women at \(2\,\mathrm{mm}\) lateral from the reference line. In all investigated areas the palatal soft tissue was significantly thicker in males than females. The bone thickness decreased and the soft tissue thickness increased as the lateral distance from the reference line increased. Another similar study [51] showed that the palatal bone was thinner in cases with class III malocclusion than in those with class I malocclusion, with significant differences in some areas. Palatal bone was thicker inthe middle region of the midline area. The palatal bone was significantly thinner in area 9.0 mm before the transverse palatine suture in the midline area, 9.0 mm before and after the transverse palatine suture in the middle area, and 9.0 mm after the transverse palatine suture in the lateral area. The study concluded that anterior and middle palatal areas are safer for putting micro-implants, while the thinness of the posterior palatal bone increases the risk of failure and perforations. Micro-implants can be used as orthodontic anchorage in infra-zygomatic areas. A research study was performed to investigate the insertion torque and pull-out strength of three brands of infra-zygomatic mini-implants. Their mechanical strength proved to depend on their design [52]. Cleft lip and palate is the most common craniofacial malformation clinical characterized by underdeveloped maxilla in transverse and sagittal dimension; it can be corrected by surgical repair of the cleft followed by orthodontic treatment [53]. Bone-anchored rapid palatal expanders had the advantage of directly anchoring the expansion appliance to the palatal bone with less dental secondary effects. The greatest stress caused by the bone expander which used OMIs as anchor system was observed in the mid-palatal suture area at the implant insertion site on the cleft side along the palatal slopes and was equally distributed superiorly to the alveolar and basal bone [53]. In conventional expanders the greatest stress was observed at tooth level both on the cleft side and on the opposite side. The zygomaticomaxillary suture experienced maximum stress, followed by the zygomat-cotemporal and nasomaxillary sutures. Displacement in the transverse plane was highest on the cleft side, and in the antero-posterior plane was highest in the posterior region [53]. The OMIs can be used as direct or indirect anchorage elements for molar up-righting in all three spatial planes [54]. The direct method is simpler because it requires one OMI and a single bracket or button, reducing the patient's discomfort and chair time compared to the indirect anchorage. It eliminates the unwanted movement of the anchorage unit. Direct anchorage has limitations in cases of rotated or limgually tipped molars because they need more than a single force to upright their position. OMIs are a reliable solution in the treatment of tipped or impacted molars. Micro-implant assisted molar intrusion in maxillary helped the prosthetic rehabilitation in mandible [55]. The maxillary molars extruded in time after opposite molar extractions in mandible could be easily intruded by using OMIs placed palatal or both buccal and palatal and placing on them intrusive forces. These procedures created a minimum of 5-8 mm for rehabilitation on implants of the posterior sector of the mandible, in adult patients [55]. The distalization with micro-implant-aided sliding mechanics proved less distal tipping of the posterior teeth and the method seemed efficient for patients with mild arch length discrepancies even without making therapeutic extractions, except the third molars [56].