Efficiency of Microosteoperforation for Accelerating Posterior Segment Intrusion in Skeletal Open Bite Cases

Instrument and procedures I. Diagnostic Procedures 1. Medical and dental history. 2. Comprehensive clinical examination. a. Extraoral examination. b. Intraoral examination. c. Functional examination. 3. Diagnostic records a. Photographs. b. Orthodontic study models. c. Lateral cephalometric records to verify the eligibility of the case. D. Analysis of records and treatment planning. Once the case fulfilled the inclusion criteria, full skull CBCT was taken before starting treatment. Interventions 1. Impression for fabrication of acrylic splint covering the occlusal surface of the whole maxillary posterior segment bilaterally. 2. Placement of miniscrews , two in each side, one placed in the Zygomatic buttress and the other one placed palatal to the first permanent molar. 3. Micro-osteoperforation using propel accelerator in Group I (MOP group). 4. Cementation of acrylic splint and force application using four closed coil spring on each side. 4. Follow up every four weeks and impression to measure amount of intrusion. III. Methods of data collection. 1. CBCT before intrusion, and CBCT after intrusion. 2. Digital models analysis. IV. Statistical Analysis.

I. Diagnostic Procedures Detailed and comprehensive patient diagnosis was performed guided by the evaluation sheet used at the Department of Orthodontics, Faculty of Dentistry, Ain Shams University. The diagnostic procedure included the following steps: 1. Medical and dental history Full history was obtained for each patient including patient's name, sex, age, chief complaint, medical and dental history. 2. Comprehensive clinical examination a. Extraoral examination Frontal examination included the examination of the patient's facial type, symmetry, vertical facial proportions, and lip competence. Smile examination comprised detailed smile analysis involving gingival display on smiling, smile arc, smile symmetry and width of buccal corridors. All the patients included in the study showed normal or increased gingival display on smiling. Profile examination incorporated the inspection of facial profile type, lip protrusion and nasolabial angle, lip competence and vertical facial proportions. b. Intraoral examination Full and detailed intraoral examination included number of teeth present in the oral cavity, oral hygiene, periodontal condition of all teeth, the presence of any caries, broken restorations, and missing teeth. Examining the malocclusion in all planes of space was performed as follows, in the anteroposterior plane, Angle molar classification, canine relationships and overjet were determined. In the vertical plane, amount of open bite was measured from the incisal edge of the maxillary central incisor to that of the mandibular central incisor. In the transverse plane, the midlines and the posterior occlusion were checked to determine any midline shift or presence of posterior crossbite. Arch form, palatal vault shape and depth were also clinically examined. Patients included in the study showed anterior open bite with class I or Class II molar relationship. c. Functional examination Patients were carefully examined to determine the mode of breathing. Mouth breathing patients were referred to ENT consultation to check for patency of airway and remove any causes of respiratory obstruction prior to treatment. Tongue examination was carefully performed at rest and during function (swallowing and speech) to determine the resting tongue posture and the presence of any tongue thrust habit during function. Those cases who needed habit breaking appliances were addressed during fixed treatment phase following the intrusion phase. 3. Diagnostic records A full set of orthodontic records was taken for every patient as part of the routine procedure for the treatment of patients in the outpatient clinic of the Orthodontic Department, Ain Shams University, including: a. Photographs• For each case, a full set of extraoral and intraoral photographs were taken. Extraoral photographs included frontal views (rest and smile), and profile view while intraoral photographs included frontal, right side, left side, and occlusal (maxillary and mandibular) views. All photographs were obtained via a 20.3 mega pixel digital camera. b. Orthodontic study models • Alginate impressions were taken for the upper and lower arches of each patient using suitable-sized perforated trays and alginate impression material mixed according to the manufacturer's instructions. Each impression was poured with improved orthodontic stone material. Wax bites were obtained using modelling pink wax in order to maintain proper occlusion during trimming to obtain articulated orthodontic study models. c. Orthodontic Radiographic records • Lateral cephalometric radiographs A lateral cephalometric radiographic image was taken for each patient and was used to measure several linear and angular measurements that determined growth pattern, steepness of mandibular plane and vertical dentoalveolar growth. Those measurements were analyzed for screening patient's eligibility for the study and to confirm the presence of vertical dysplasia. All the cases had posterior vertical dentoalveolar excess and anterior open bite.

• Orthopantomogram radiograph An Orthopantomogram radiograph was taken and used to detect any dental or bone anomalies, and evaluate the general periodontal condition & bone level, & position of third molars.

All the previously gathered data were analyzed and once the diagnosis of the case fulfilled the inclusion criteria, the patient was given a full explanation for the treatment plan and was asked to sign a detailed written informed consent of agreement in which the aim of the study, the methodology and possible complications were clearly described.

Formulation of the problem list and treatment plan. All the previously gathered data were analyzed, then used to formulate the problem list and eventually develop the treatment plan. If the treatment plan included posterior segment intrusion to allow closure of open bite by mandibular autorotation, the patient was included in the study. Patients were then asked to sign a detailed written informed consent of agreement in which the aim of the study, the methodology and possible complications were clearly described. Patients were randomly allocated into the MOP or control groups, and intervention procedures were then started. II. Interventions Pretreatment Cone Beam Computed Tomography (CBCT). All patients enrolled in this study were imaged using the i-CAT CBCT scanner at the department of Oral Radiology, Faculty of Dentistry, Ain Shams University. The procedures completed in this study were as follows: Micro-osteoperforation (MOP) Group I, a duplicate was taken for the maxillary arch to fabricate the maxillary acrylic splint. miniscrew implants were inserted on both sides. Micro-osteoperforations were performed by Propel accelerator. The splint was cemented in place. Immediate intrusion force was applied using closed coil springs. The details are as follows: 1. Placement of four self-drilling and self-tapping Titanium TADs, with a size of 1.8 mm in diameter and 10 mm in length. They were placed at the following sites: two buccal implants placed bilaterally at the Zygomatic buttress area and the two palatal implants placed bilaterally at the palatal region. After palpating the Zygomatic buttress in the buccal sulcus apical to the mesiobuccal cusp of the maxillary first molar, a short vertical vestibular incision (1-1.5 cm in length) was made. The lower aspect of the Zygomatic process of the maxilla was exposed by blunt dissection, then the implant was inserted at the oblique area present between the horizontal and vertical shelves of the Zygomatic buttress just above the upper first molar, 14-16 mm above the maxillary occlusal plane , at an angle of 55-70° to the maxillary occlusal plane. An easy adaptable thick ligature wire (0.014) was ligated through the hole at the implant head to form a hook to facilitate attachment to the eyelets of the coil spring in case the implant gets covered by soft tissue overgrowth. The patients were instructed to follow strict oral hygiene instructions and the insertion site was allowed to heal for one week. After one week, the palatal miniscrew implants were inserted bilaterally at an anteroposterior position apical to the first molars (approximately at the mesiopalatal line angle), and mediolaterally at approximately 3mm to 5mm lateral to the median palatine. 2- At the same visit, micro-osteoperforations were performed in group I before by the Propel® Excellerator MOP device following the manufacturer instructions. Three MOPs were performed in a linear pattern at the buccal side, mesial and distal to the roots of all maxillary premolars and molars except distal to maxillary second molars due to lack of accessibility. The depth of perforations was adjusted based on the estimated thickness of the gingiva and alveolar bone ranging from 5 mm at the premolar region to 7 mm at the molar region. The perforations were made 2-3 mm away from apex of interdental papillae to avoid their damage and within the attached gingiva area to avoid soft tissue rolling around the micro-tip. 3- Appliance assembly and force application were initiated at the same visit after MOPs to benefit from the inflammatory reaction initiated by the minor bone injuries. Then it was cemented in place with temporary cement which provided good seal, low solubility and was easily removed during follow-up visits. Intrusion force was applied by Nickel-Titanium (Ni-Ti), medium force (150 g) closed coil springs. Four springs were attached on each side extending from the hooks of the appliance buccally and lingually at one end and to the zygomatic and palatal implants' head at the other end. The total force magnitude was 600 g per side, divided to 300 g from the buccal and palatal sides. This force was uniformly distributed via the acrylic splint along the long axis and over the root surface area of maxillary molars and premolars. The mandibular arch was stabilized by a vacuum retainer extending to the last distal tooth in the arch fabricated from thermoplastic sheets of 1 mm thickness to prevent compensatory eruption of mandibular molars during maxillary intrusion. The desired amount of activation was produced by controlling the length of the coil springs through ligation ties to adjust the length producing the required force on each side. 4-Follow-up The patients were recalled at two- and four-weeks intervals. At the two weeks recall visit, the coil springs were checked for their attachment integrity.

Every four weeks, the appliance was removed, and alginate impressions were taken for the upper arch. Those impressions were then poured in hard stone and scanned using desktop R 700 scanner. Intrusion was continued until 1-2mm positive overbite was achieved as clinically measured by a metal ruler graduated in mm.

Control group 1. The same procedures were performed in the same manner as in MOP group except for micro-osteoperforation step. Those procedures included impression taking for fabrication of intrusion splint, miniscrew implant placement with the same size, manner and sites, appliance assembly and force application. The same follow-up protocol was advocated as well.

Then records including CBCTs before and after intrusion were obtained to analyze difference in skeletal, dental, and soft tissue measurements between the groups. Digital models obtained at four weeks were analyzed and superimposed to determine the rate of intrusion and to detect the presence of any difference between the groups.

Inclusion criteria

• Clinical anterior open bite involving the incisors and canines ranging from -3 mm to -8 mm
• Skeletal open bite confirmed by pretreatment cephalometric angular and linear measurements.
• Maxillary posterior vertical dentoalveolar excess guided by the analysis of Burstone et al.
• Normal incisor display at rest and during smile.
• Non-growing postpubertal adolescent and adult patients with CVM 6 according to Baccetti et al.
• Full set of permanent dentition regardless of third molars.
• Good oral hygiene.

Exclusion criteria

• Skeletal Class III cases.
• Patients suffering from any systemic diseases or congenital anomalies affecting bone.
• Patients with previous orthodontic treatment.