Kang-Mi Pang

Biomechanical evaluation of magnesium-based resorbable metallic screw system in a bilateral sagittal split ramus osteotomy model using three-dimensional finite element analysis.

PURPOSE The aim of this study was to evaluate the stress distribution of a magnesium (Mg)-based resorbable screw system in a bilateral sagittal split ramus osteotomy (BSSO) and to compare its biomechanical stability with those of titanium (Ti)-based and polymer (IN)-based systems. MATERIALS AND METHODS A 3-dimensional BSSO model (10-mm advancement and setback) was constructed with Mimics. Bicortical screw fixation using Ti, IN, and Mg screws was performed with 4 different geometries of fixation. With an occlusal load of 132 N on the lower first molar, the von Mises stress (VMS) distribution was calculated using ANSYS. RESULTS The VMS distribution of Mg was more similar to that of Ti than to that of IN. In all cases, the highest VMS was concentrated on the screw at the most posterior and superior area. Stress was distributed mainly around the screw holes (cancellous bone) and the retromolar area (cortical bone). In the advancement surgery, fixation with 5 Mg screws (5A-Mg, 99.810 MPa at cortical bone) showed biomechanical stability, whereas fixation with the same number of IN screws did not (5A-IN, 109.021 MPa at cortical bone). In the setback surgery, although the maximum VMSs at cortical bone for Mg, IN, and Ti were lower than 108 MPa (yield strength of cortical bone), Mg screws showed more favorable results than IN screws because the maximum VMSs of Mg at cancellous bone were lower than those of IN. CONCLUSION The Mg-based resorbable screw system is a promising alternative to the IN-based system.

Human umbilical cord blood-derived mesenchymal stem cells promote regeneration of crush-injured rat sciatic nerves

Several studies have demonstrated that human umbilical cord blood-derived mesenchymal stem cells can promote neural regeneration following brain injury. However, the therapeutic effects of human umbilical cord blood-derived mesenchymal stem cells in guiding peripheral nerve regeneration remain poorly understood. This study was designed to investigate the effects of human umbilical cord blood-derived mesenchymal stem cells on neural regeneration using a rat sciatic nerve crush injury model. Human umbilical cord blood-derived mesenchymal stem cells (1 × 106) or a PBS control were injected into the crush-injured segment of the sciatic nerve. Four weeks after cell injection, brain-derived neurotrophic factor and tyrosine kinase receptor B mRNA expression at the lesion site was increased in comparison to control. Furthermore, sciatic function index, Fluoro Gold-labeled neuron counts and axon density were also significantly increased when compared with control. Our results indicate that human umbilical cord blood-derived mesenchymal stem cells promote the functional recovery of crush-injured sciatic nerves.

Masticatory muscle pain and progressive mouth opening limitation caused by amyotrophic lateral sclerosis: a case report.

This article reports a case of masticatory muscle pain and progressive limited mouth opening secondary to amyotrophic lateral sclerosis (ALS), popularly known as Lou Gehrigs disease. The symptoms were first mistaken as those of temporomandibular disorders, before fatty degeneration of all masticatory muscles were discovered on magnetic resonance imaging (MRI). ALS should be considered in the differential diagnosis process when the patient presents with longstanding progressive mouth opening limitation associated with pain. MRI could facilitate the diagnostic process.

Biologic properties of nano-hydroxyapatite: An in vivo study of calvarial defects, ectopic bone formation and bone implantation.

This study investigated the biologic properties of nano-hydroxyapatite (nHAp) using the rat calvarial defect, ectopic bone formation, and rabbit tibia implant installation models. Animals were divided into two groups: those implanted with nHAp, and negative controls (Collagen). Eight weeks after creating an 8 mm calvarial defect, bone regeneration was evaluated radiographically and histologically. To investigate ectopic bone formation, materials were injected into the right thigh muscle and were evaluated after 8 weeks. nHAp coated implant and conventional titanium implant were placed bilaterally in rabbit tibias. After 4 weeks, bone-implant contact (BIC), new bone area inside the thread, and removal torque were measured. In the calvarial defect model, radiographic and histologic analysis showed more bone formation in the nHAp Group; particularly, histologically assessed bone area (p=0.034) and microcomputed tomography assessed bone mineral density (p=0.034). In the ectopic bone formation model, calcification and expression of osteogenic biomarkers were seen in the nHAp-injected samples but in none of the controls. nHAp coated implant resulted in increased BIC, new bone area, and increased removal torque, with statistical significance for BIC (p=0.034). This study suggests that nHAp has potential as a coating material for dental implant surfaces and as a bone graft material.

Clinical outcomes of magnesium‐incorporated oxidised implants: a randomised double‐blind clinical trial

OBJECTIVES This study evaluated implant stability and clinical outcomes obtained with magnesium-incorporated oxidised implants (Mg titanate) and compared them to those blasted magnesium-incorporated oxidised implants (blasted Mg titanate). PATIENTS AND METHODS Mg titanate was manufactured using the microarc oxidation (MAO) process. To obtain blasted Mg titanate, the MAO process was performed after blasting with TiO₂ particles. The 15-month, randomised, double -blind clinical trial was conducted on 54 implants in 40 patients (Mg titanate, 27 implants in 18 subjects; blasted Mg titanate, 27 implants in 22 subjects), in whom 4.0 mm × 10 mm implants were placed to restore the unilateral loss of one or two molars in the mandible. The final prosthesis was attached 3 months postoperatively. Implant stability was measured by the implant stability quotient (ISQ) and periotest value (PTV) at the time of implant insertion, and 2, 3, and 15 months postoperatively. Marginal bone loss was evaluated at 2, 6, and 15 months postoperatively. Soft tissue analysis was performed at 15 months postoperatively. RESULTS Both implant systems showed high stability at all time points (>71). Mean marginal bone loss was 0.71 ± 0.65 mm and 0.75 ± 0.73 after 15 months in Mg titanate and blasted Mg titanate, respectively. There were no significant differences between the two implant surfaces with respect to ISQ(P = 0.988), PTV(P = 0.935), and marginal bone loss(P = 0.807) after 15 months. CONCLUSION The success rate after 1 year of follow-up was 100% for both magnesium-incorporated oxidised implants. There were no significant differences in the clinical outcomes between the two surfaces at 15 months follow-up.

Influencing factor on the prognosis of arthrocentesis

Objectives The purpose of this article is to evaluate factors influencing prognosis of arthrocentesis in patients with temporomandibular joint (TMJ) disorder. Materials and Methods The subjects included 145 patients treated with arthrocentesis at the Dental Center of Ajou University Hospital from 2011 to 2013 for the purpose of recovering mouth opening limitation (MOL) and pain relief. Prognosis of arthrocentesis was evaluated 1 month after the operation. Improvement on MOL was defined as an increase from below 30 mm (MOL ≤30 mm) to above 40 mm (MOL ≥40 mm), and pain relief was defined as when a group with TMJ pain with a visual analog scale (VAS) score of 4 or more (VAS ≥4) decreased to a score of 3 or more. The success of arthrocentesis was determined when either mouth opening improved or pain relief was fulfilled. To determine the factors influencing the success of arthrocentesis, the patients were classified by age, gender, diagnosis group (the anterior disc displacement without reduction group, the anterior disc displacement with reduction group, or other TMJ disorders group), time of onset and oral habits (clenching, bruxism) to investigate the correlations between these factors and prognosis. Results One hundred twenty out of 145 patients who underwent arthrocentesis (83.4%) were found to be successful. Among the influencing factors mentioned above, age, diagnosis and time of onset had no statistically significant correlation with the success of arthrocentesis. However, a group of patients in their fifties showed a lower success rate (ANOVA P=0.053) and the success rate of the group with oral habits was 71% (Pearsons chi-square test P=0.035). Conclusion From this study, we find that factors influencing the success of arthrocentesis include age and oral habits. We also conclude that arthrocentesis is effective in treating mouth opening symptoms and for pain relief.

Clinical outcome of conservative treatment of injured inferior alveolar nerve during dental implant placement

Objectives Infererior alveolar nerve (IAN) damage may be one of the distressing complications occurring during implant placement. Because of nature of closed injury, a large proportion is approached non-invasively. The purpose of this study was to analyze the outcomes of conservative management of the injured nerve during dental implant procedure. Materials and Methods Sixty-four patients of implant related IAN injury, who were managed by medication or observation from January 1997 to March 2007 at the Department of Oral and Maxillofacial Surgery, Seoul National University Dental Hospital, were retrospectively investigated. The objective tests and subjective evaluations were performed to evaluate the degree of damage and duration of sensory disturbance recovery. Tests were performed on the day of the first visit and every two months afterward. Patients initial symptoms, proximity of the implant to the IAN, time interval between implant surgery and the first visit to our clinic, and treatment after implant surgery were analyzed to determine whether these factors affected the final outcomes. Results Among the 64 patients, 23 had a chief complaint of sensory disturbance and others with dysesthesia. The mean time until first visit to our hospital after the injury was 10.9 months.One year after nerve injury, the sensation was improved in 9 patients, whereas not improved in 38 patients, even 4 patients experienced deterioration. Better prognosis was observed in the group of patients with early visits and with implants placed or managed not too close to the IAN. Conclusion Nearly 70% of patients with IAN injury during implant placement showed no improvement in sensation or dysesthesia with the conservative management. Earlier decision for active treatment needs to be considered because of possibility of deterioration of symptoms and unsatisfactory recovery.

Mandibular condylar-ramal reconstruction using vascularised costochondral graft based on the serratus anterior composite flap

BACKGROUND Nonvascularised autogenous costochondral rib grafts are the gold standard for replacement of the mandibular ramus and condyle. However, condylar defects present a difficult condition to treat when soft tissue defects are involved. Thus, we used vascularised costochondral grafts (VCGs) with a cartilaginous cap based on the serratus anterior muscle flap to reconstruct these composite defects. The purpose of this study was to evaluate the advantages and effectiveness of VCGs based on long-term observation. METHODS We evaluated 15 patients who underwent mandibular condyle and ramus reconstruction using VCG after a mean follow-up of 75.9 months (range 46-156 months). Our 15 case of mandibular reconstruction with a serratus anterior/rib composite free flap due to congenital or acquired defects involved a total of 18 condyles (bilateral reconstruction in 3 cases and unilateral reconstruction in 12 cases). RESULTS Our success rate with the use of the serratus anterior/rib composite free flap was 100%, and there were no cases of resorption or malunion of the graft. The mean maximum mouth opening (MMO) at the last follow-up was 31.29 ± 7.56 mm (range 15-45 mm). Although two patients exhibited excessive growth of the graft, deficient growth of the graft was also found in our paediatric patients. Four patients who developed ankylosed TMJ during the follow-up period received additional gap arthroplasty. CONCLUSION VCG based on a serratus anterior flap was an excellent treatment modality for patients with uni-or bilateral composite defects of the ramus and condyle, in which soft tissue and hard tissue, including both bone and cartilage, were necessary.

Recombinant human fibroblast growth factor-2 promotes nerve regeneration and functional recovery after mental nerve crush injury

Several studies have shown that fibroblast growth factor-2 (FGF2) can directly affect axon regeneration after peripheral nerve damage. In this study, we performed sensory tests and histological analyses to study the effect of recombinant human FGF-2 (rhFGF2) treatment on damaged mental nerves. The mental nerves of 6-week-old male Sprague-Dawley rats were crush-injured for 1 minute and then treated with 10 or 50 μg/mL rhFGF2 or PBS in crush injury area with a mini Osmotic pump. Sensory test using von Frey filaments at 1 week revealed the presence of sensory degeneration based on decreased gap score and increased difference score. However, at 2 weeks, the gap score and difference score were significantly rebounded in the mental nerve crush group treated with 10 μg/mL rhFGF2. Interestingly, treatment with 10 μg/mL rhFGF had a more obviously positive effect on the gap score than treatment with 50 μg/mL rhFGF2. In addition, retrograde neuronal tracing with Dil revealed a significant increase in nerve regeneration in the trigeminal ganglion at 2 and 4 weeks in the rhFGF2 groups (10 μg/mL and 50 μg/mL) than in the PBS group. The 10 μg/mL rhFGF2 group also showed an obviously robust regeneration in axon density in the mental nerve at 4 weeks. Our results demonstrate that 10 μg/mL rhFGF induces mental nerve regeneration and sensory recovery after mental nerve crush injury.

Maximal strength and endurance scores of the tongue, lip, and cheek in healthy, normal Koreans

Objectives The purpose of this study was to establish normative data for healthy Korean adults by measuring the maximal strength and endurance scores of the tongue, lip, and cheek, and to examine correlations between these measurements. Materials and Methods This study included 120 subjects that were divided into three groups according to age: young (20-39 years), middle-aged (40-59 years), and older (over 60 years); and by gender. Measurements were taken using the Iowa Oral Performance Instrument (IOPI). Results The mean maximal tongue strengths were as follows: young men (46.7±10.2 kPa) and women (32.1±7.9 kPa), middle-aged men (40.9±9.3 kPa) and women (36.9±8.6 kPa), and older men (35.2±9.0 kPa) and women (34.5±6.9 kPa). The mean tongue endurance scores were: young men (28.8±12.6 seconds) and women (20.8±13.5 seconds), middle-aged men (17.0±8.5 seconds) and women (15.3±5.2 seconds), and older men (15.8±6.7 seconds) and women (17.9±8.1 seconds). The mean maximal lip strengths were: young men (11.6±3.0 kPa) and women (11.4±3.8 kPa), middle-aged men (11.4±4.2 kPa) and women (11.1±5.1 kPa), and older men (14.5±3.9 kPa) and women (11.7±2.6 kPa). The mean lip endurance scores were: young men (41.1±23.9 seconds) and women (22.4±21.7 seconds), middle-aged men (24.3±10.3 seconds) and women (30.5±13.4 seconds), and older men (24.9±11.0 seconds) and women (12.8±7.6 seconds). The mean maximal cheek strengths were: young men (24.5±4.6 kPa) and women (20.5±4.3 kPa), middle-aged men (25.2±6.4 kPa) and women (21.2±5.5 kPa), and older men (22.4±5.3 kPa) and women (18.0±4.8 kPa). The mean cheek endurance scores were: young men (47.8±24.4 seconds) and women (43.9±25.0 seconds), middle-aged men (27.3±11.3 seconds) and women (20.0±14.6 seconds), and older men (21.7±14.5 seconds) and women (17.2±11.4 seconds). Conclusion The data collected in this study will provide an important database of standardized measurements for maximal strength and endurance scores of the tongue, lip and cheek in healthy, normal Koreans.