Following the surgical release of the mentalis muscle, lip incompetence and/or an increase in lower incisor exposure may be seen due to undesirable attachment of the muscle fibres. The aim of this study was to evaluate the extent of lip ptosis, lower incisor exposure, and other soft tissue changes following bone graft harvesting from the mandibular symphysis when the mentalis muscle is reapproximated precisely to its original position. Seventeen consecutive patients who underwent bone graft harvesting from the mandibular symphysis were included in this study. The mentalis muscle was isolated, identified, marked, and reapproximated precisely during the bone harvesting operation. Digital lateral cephalograms obtained preoperatively and at 6 months postoperative were analyzed and compared by paired samples t -test to determine the horizontal and vertical soft tissue changes in the lower lip and chin. Although the soft tissue thickness at soft tissue point B and at soft tissue pogonion had increased significantly at 6 months after chin bone graft harvesting, there were no significant changes in lower incisor exposure or other positional alterations of the lower lip ( P < 0.05). Precise reattachment of the mentalis muscle in its original position helps to avoid significant vertical positional changes in the lower lip. Increases in soft tissue thickness can be observed following bone graft harvesting from the mandibular symphysis.
Alveolar ridge augmentation is a routine procedure performed by clinicians so that implants of the desired width and length can be inserted. The autogenous bone grafts for alveolar ridge augmentation are commonly harvested from intraoral donor sites such as the mandibular ramus and symphysis. Bone graft harvesting from the mandibular symphysis has been reported to be a reliable procedure that offers easy access and an adequate bone tissue volume for grafting. However, previous studies on this subject have reported certain soft tissue changes due to the release of the mentalis muscle during the graft harvesting procedure.
The mentalis muscle is the only muscle that is exposed during the surgical approach for symphysis bone graft harvesting. It is the sole elevator of the lower lip and chin. Although there are no fibres that pass into the lower lip, the mentalis muscle also provides major vertical support to the lower lip.
The surgical approach to the osteotomy site when harvesting a bone graft from the symphysis necessitates degloving most of the chin and detachment of the mentalis muscle. If the mentalis muscle is either not functioning or not precisely repositioned after surgery, the result may be extremely unaesthetic because of possible chin ptosis and lip incompetence. Careful reapproximation of the mentalis muscle during flap closure is recommended to avoid these complications.
Most previous studies on the mandibular symphysis bone graft harvesting procedure have focused on the bone graft itself rather than the neighbouring soft tissues. Lip and chin contour alterations following mandibular symphysis bone grafts have been evaluated previously, with several changes in the vertical plane reported. It has been suggested that further studies are needed to assess the alterations in the soft tissues, such as the lip and chin, after the bone graft block has been harvested from the donor area. However information is still missing on the soft tissue changes following a mandibular symphysis bone graft harvesting procedure that enables precise repositioning of the mentalis muscle during closure of the surgical flap.
The aim of this study was to compare vertical and sagittal profile changes in the lower lip and chin following mandibular symphysis bone graft harvesting with precise reattachment of the mentalis muscle during closure of the mucoperiosteal flap.
Materials and methods
Seventeen consecutive adult patients who underwent a mandibular symphysis bone graft harvesting procedure were included in this study. Thirteen were female and four were male, and their mean age was 42.5 ± 9.7 years. All were American Society of Anesthesiologists (ASA) category I. All procedures were performed between January and June 2014.
Exclusion criteria were as follows:
Patients who had undergone previous operations for bone harvesting from the same field,
Bone-related systemic diseases such as osteoporosis, which could alter bone remodelling,
Patients who received orthodontic treatment during the study,
Patients whose central incisors and/or first molars were missing,
Patients who received restorations on their first molars or incisors during the study.
All surgical procedures were performed under local anaesthesia by the same oral and maxillofacial surgeon.
Local anaesthetic (4 ml 2% lidocaine with 1:200,000 epinephrine) was administered along the mucosal incision line and mental foramen point for bleeding and pain control. A superficial incision was made through the lower labial mucosa with a scalpel, leaving at least 5 mm of non-keratinized mucosa superiorly between the bilateral lower cuspids. Subsequently, a sub-mucosal incision was made to expose the mentalis muscle. Following the mentalis muscle dissection, the lower and upper ends of the muscle were marked with 3-0 resorbable suture material to suture the muscle in its original position, in accordance with the technique described by Chaushu et al. ( Fig. 1 ). Periosteal incision and mucoperiosteal dissection were performed with the marker sutures left on both edges of the muscle fibres. The bilateral mental nerves were identified and protected during the creation of the mucoperiosteal flap. Periosteal attachment of the mental protuberance was preserved in all patients. The osteotomy was performed at least 5 mm below the root apices and 5 mm away from the mental foramen with a piezoelectric surgical device (VarioSurg 50/60 Hz; NSK, Tochigi, Japan). Corticocancellous bone grafts were harvested by straight or inclined osteotomies. No grafts or biomaterials were used to fill the bony defects at the donor sites. The soft tissue closure was completed in two stages. First the mentalis muscle layer was closed by initial marking material with two horizontal mattress sutures, and then the mucosa layer was sutured with 3-0 Vicryl suture material with a simple suturing technique.