Abstract
The aim of this prospective clinical study was to evaluate the short-term and long-term skeletal and dental changes after mandibular osteodistraction with tooth-borne appliances in adult orthodontic patients. The sample consisted of 10 non-growing Caucasian patients with a Class II skeletal relationship due to mandibular deficiency, together with Class II dental malocclusion. All patients underwent mandibular distraction osteogenesis (MDO) using the ROD1 tooth-borne device. Lateral cephalograms were evaluated at four time intervals: pretreatment (T1), after mandibular distraction (T2), after orthodontic fixed appliance therapy (T3), and at long-term observation 8-year post-distraction (T4). Statistical analyses compared the skeletal and dental changes in intervals T1–T2, T2–T3, T3–T4, T1–T4, and T2–T4. MDO with the ROD1 tooth-borne device produced significant long-term (T1–T4) increases in the SNB angle (2.3°), total mandibular length (5.9 mm), and corpus length (4.5 mm). Potential adverse sequelae included significant increases in mandibular plane angle (4.3°), lower anterior dental height (2.8 mm), and lower posterior dental height (2.5 mm). Significant increases in lower incisor proclination occurred during distraction (7.5°). Distraction osteogenesis with tooth-borne appliances offers a minimally invasive surgical method with stable results for correcting mandibular deficiency in non-growing patients.
Introduction
The orthodontic treatment of adult Class II patients with mandibular retrognathia often entails dental camouflaging or mandibular advancement surgery, including bilateral sagittal split or vertical ramus osteotomies. Distraction osteogenesis (DO), the biological process of new bone formation by gradually stretching the healing callus that joins surgically divided bone segments, has become an important alternative surgical technique for the craniofacial region. Mandibular DO (MDO) is frequently performed in young children with congenital craniofacial skeletal deformities including severe micrognathia, as well as children and adults with ankylosis of the temporomandibular joint (TMJ) to elongate the mandible, improve function, and enhance the soft tissue profile. However, MDO is performed less often in adult Class II patients for skeletal correction of mandibular retrognathia.
The advantages of MDO compared to the conventional orthognathic surgery include: enables extensive bone lengthening ; eliminates the need for bone grafting and inter-maxillary fixation ; the incremental skeletal movements allow for accommodation of the soft tissues ; reduces surgical stress ; and reduces the incidence of inferior alveolar nerve dysesthesia. The primary disadvantages of MDO include: the total length of treatment, which may take up to 3–4 months to ensure adequate stabilization of the regenerate, and the potential for bite opening.
The appliances used for MDO can be categorized with regard to whether they are internal or external, the direction of distraction, and the site of application. External devices are inserted through the skin to the mandible. These devices are capable of extensive distraction and multi-dimensional control; however they are conspicuous and bulky, and more likely to cause traction scarring on the face. Internal or intraoral devices are attached either to bone or less commonly to teeth adjacent to the osteotomy site. Some devices are attached to teeth and bone (known as hybrid devices), thereby providing both direct and indirect skeletal fixation. Most internal distractors are capable of unidirectional distraction only. Internal devices are less visible than external devices and will not cause scarring, though they are often limited to the extent and direction of distraction and the distraction rod may create excessive pressure on the lower lip.
In regards to intraoral devices, tooth-borne distraction offers numerous advantages in comparison to bone-borne distraction, including: eliminates the need for a second surgery to remove the distraction bone Plates ; the distraction screws are removable which maximizes the surgical access; and interdental distraction osteotomies and seating of the device are performed in an outpatient setting, which minimizes operation time, surgical morbidity, and hospital expenses. Despite these advantages, the current literature regarding bilateral intraoral MDO in adult patients has mainly been focused on bone-borne or hybrid appliances.
Hamada et al. presented a case report of bilateral MDO using a bone-borne appliance for the treatment of obstructive sleep apnea syndrome (OSAS) in a 31-year-old male with severe retrognathia (SNB = 67.4°). At the end of distraction, the cephalometric analyses revealed a 2.8° decrease in ANB, a 3.0° increase in mandibular plane angle (MPA), a 7.6° increase in lower incisor angulation, and a 3.5 mm increase in LL to E-line. After 3 years and 1 month of post-distraction orthodontic treatment, followed by 9 months in retention, ANB relapsed slightly (0.9°) and the mandibular incisors further proclined (1.2°), while the MPA remained constant.
Karacay et al. presented a case report of MDO using the MD-DOS bone-borne appliance in a 20-year-old male with a hyperplastic maxilla (SNA = 86°, ANB = 6°) and excessive overjet (16 mm). At the end of consolidation (10 weeks after distraction at the time of device removal), the cephalometric analyses revealed a 4° decrease in ANB, an 11 mm increase in total effective mandibular length, a 6 mm increase in corpus length, a 7° increase in y -axis, a 15° increase in lower incisor angulation, and 4 mm increase in LL to E-line. At the 1-year follow-up appointment (17 months after removal of the distraction device), ANB relapsed 2°, total mandibular length relapsed 4 mm, corpus length relapsed 2 mm, y -axis returned to the original pretreatment value, lower incisors maintained their proclination, and the lower lip maintained protrusion relative to the E-plane.
Mattick et al. presented three case reports of bilateral mandibular advancement by MDO using the intraoral bone-borne device in Class II adult patients (mean age 22 years). At the end of fixed orthodontic treatment (4–7 months post-distraction), cephalometric analyses revealed a mean 4.7° decrease in ANB, a mean 11.1 mm increase in total effective mandibular length, and a 1.8° decrease in lower incisor angulation.
Sadakah et al. performed bilateral MDO using a bone-borne appliance in two adult Class II patients (mean age 29 years) with TMJ ankylosis and retrognathia (mean SNB = 63°). At a mean 15 months post-distraction, the authors reported a mean 13° increase in SNB from the pretreatment value, despite a mean 4.5 mm of relapse in mandibular length.
In 1997, Razdolsky introduced the ROD1 (Oral Osteodistraction, LP, Buffalo Grove, IL, USA), a tooth-borne distraction device for multiplanar interdental distraction ( Fig. 1 ). The main indications for using ROD1 are in cases with skeletal Class II due to mandibular deficiency, especially when accompanied by lower incisor crowding and/or flaring in horizontal growth pattern. Currently, no prospective clinical study has evaluated the long-term effects of bilateral antero-posterior MDO using a tooth-borne appliance in non-growing patients. The purpose of this study was to evaluate the long-term skeletal and dental changes after antero-posterior mandibular distraction using the tooth-borne ROD1 distraction device in Class II adult orthodontic patients.
