Front-block technical note: dental and bone borne distractors

Accuracy of mandibular anterior subapical osteotomy by virtual planning in orthognathic surgery using patient-specific implants

INTRODUCTION

Mandibular anterior subapical osteotomy (MASO) is a complementary procedure during orthognathic surgery to correct proclination or extrusion of the anterior incisors when orthodontic movements fail. The increasing use of patient-specific implants (PSI, titanium plates) in orthognathic surgery has extended to this procedure. Digital orthognathic surgery planning involves manufacturing cutting/drilling guides and specific implants to provide better accuracy and allow complex movement with reduced surgical times compared to conventional planning. This study aimed to assess the accuracy of computer-aided surgery with patient-specific implants in mobilising the MASO segment according to planning.

METHODS

Eleven consecutive patients with mean age 26.82 years (15-41, SD = 10.65) were treated with MASO in addition to other conventional orthognathic procedures incorporating digital planning and patient-specific implants. A three-dimensional "stl" format file of the mandibular dental arch was obtained using an intraoral scanner at the end of the surgical procedure. The accuracy of the MASO segment displacement imposed by PSI was assessed by comparing preoperative 3D-planned mandibular dental arch with the immediate postoperative 3D-measured arch, using surface superimposition and 7 standard dental landmarks. Deviations between the preoperative and postoperative landmarks were calculated and compared to determine whether MASO segment repositioning is sufficiently accurate to be safely used to reposition the incisor/canine axis.

RESULTS

Quantitative analysis revealed an absolute linear difference of 0.66 mm (SD = 0.51) between preoperative 3D digital dental arch impression and postoperative planned 3D dental arch. Overall, the median absolute discrepancies in the x-axis (right-left direction), y-axis (antero-posterior direction), and z-axis (supero-inferior direction) were respectively 0.56 mm (SD = 0.42), 0.77 mm (SD = 0.45) and 0.65 mm (SD = 0.61).

CONCLUSION

A high degree of accuracy between the virtual plan and the immediate postoperative result was observed. According to our results, PSI can be used safely with accuracy in MASO as an adjunct to other conventional orthognathic procedures.

Combined mentalis weakening and periosteal flaps in mandibular anterior alveolar corticotomy-assisted orthodontics with bone grafting

Inter-alveolar augmented corticotomies with bone grafting may be used before orthodontic treatment in cases of root out or in major proclination movements in the lower anterior region. Bone graft particle spreading with reduced confinement and strong labial muscle contractions may cause graft resorption. Herein we describe a combined orthodontic corticotomy technique involving periosteal flap grafting confinement and a surgical muscle-weakening flap to avoid resorption.