Kaijin Hu

Selection of optimal dental implant diameter and length in type IV bone: a three-dimensional finite element analysis

This study aimed to create a 3D finite element model for continuous variation of implant diameter and length, thereby identifying their optimal range in type IV bone under biomechanical consideration. Implant diameter ranged from 3.0 to 5.0mm, and implant length ranged from 6.0 to 14.0mm. The results suggest that under axial load, the maximum Von Mises stresses in cortical and cancellous bones decrease by 50% and 27%, respectively; and under buccolingual load, by 52% and 60%, respectively. Under these two loads, the maximum displacements of implant-abutment complex decrease by 39% and 43%, respectively. These results indicate that in type IV bone, implant length is more crucial in reducing bone stress and enhancing the stability of implant-abutment complex than implant diameter. Biomechanically, implant diameter exceeding 4.0mm and implant length exceeding 9.0mm are the combination with optimal properties for a screwed implant in type IV bone.

Optimal design of thread height and width on an immediately loaded cylinder implant: A finite element analysis

In this study, we used a finite element method to evaluate the maximum Von Mises stresses in jaw bones of immediately loaded implant with different thread heights and widths, and the maximum displacements in implant-abutment complex. The implant thread height ranged from 0.20 to 0.60 mm, and the thread width ranged from 0.10 to 0.40 mm. Compared to those in standard designed implants, the maximum Von Mises stresses in cortical and cancellous bones with axially loaded implants decreased by 18.85% and 47.46%, respectively, and by 16.38% and 63.46%, respectively in buccolingually loaded implants. The maximum displacement of implant-abutment complex loaded axially and buccolingually decreased by 13.78% and 6.97%, respectively. These results indicated that thread height played more important roles in affecting bone stresses and implant-abutment complex stability than thread width. Immediately loaded cylinder implants with thread height exceeding 0.44 mm and width ranging from 0.19 to 0.23 mm caused the lowest stresses to the type B/2 bone.

Transport distraction osteogenesis using nitinol spring: an exploration in canine mandible.

Some experiments in rabbits have presented the potential feasibility of using shape memory alloy spring for continuous distraction osteogenesis. To confirm the effectiveness of such method, we established canine models for the exploratory experiments of transport distraction osteogenesis using nitinol springs. Simple devices, including an internal 60-mm long sinusoid-shaped nitinol springs were used in the study. All dogs needed only one operation. In theoperation, osteotomy was performed to create a 40-mm unilateral segmental mandibular body defect and a tooth-bearing transport bone disc. After reconstructive fixation of the remnant mandible, the spring was constricted and anchored across the distraction gap to activate transport distraction immediately. At the second experimental stage, an ePTFE sheet was further fixed to protect the defect and distraction gap before closing the incision. Control dogs underwent the same operation except for anchoring of the spring to examine the spontaneous bone regeneration. Automatic bone transportation, as a gradual slowdown process, was observed under the effect of the spring. The transport disc could get to the opposite side of the defect, or stopped halfway when ePTFE sheet intervened. Mandibular reconstruction was achieved in all these dogs and better in dogs with sheet protection. No integrated bone mass was found in the defect of control dogs. The study further proves that continuous distraction osteogenesis using nitinol springs is a practical technique, although the devices need more improvement for better control of the process of distraction and the quality of regenerated bone.

Modified dextrose prolotherapy for recurrent temporomandibular joint dislocation

Conservative interventions with simple procedures and predictable benefits are expected by patients with recurrent dislocation of the temporomandibular joint (TMJ). We have introduced a modified technique of prolotherapy that comprises injection of lignocaine and 50% dextrose at a single site in the posterior periarticular tissues. We studied the effects in 45 younger patients (age range 17-59 years) with non-neurogenic recurrent dislocation of the TMJ, and confirmed the therapeutic effect after more than a years follow-up. There were appreciable improvements in the number of episodes of dislocation and clicking after the injection. The overall success rate, defined as the absence of any further dislocation or subluxation for more than 6 months, was 41/45 (91%). Of the 41 rehabilitated patients, 26 (63%) required a single injection, 11 (27%) had 2 treatments, and 4 (10%) needed a third injection. All patients tolerated the injections well. The modified dextrose prolotherapy is simple, safe, and cost-effective for the treatment of recurrent dislocation of the TMJ.

The role of the lateral pterygoid muscle in the sagittal fracture of mandibular condyle (SFMC) healing process

The aim of this study was to examine the role of the lateral peterygoid muscle in the reconstruction of the shape of the condyle during healing of a sagittal fracture of the mandibular condyle. Twenty adult sheep were divided into 2 groups: all had a unilateral operation on the right side when the anterior and posterior attachments of the discs were cut, and an oblique vertical osteotomy was made from the lateral pole of the condyle to the medial side of the condylar neck. Ten sheep had the lateral pterygoid muscle cut, and the other 10 sheep did not. Sheep were killed at 4 weeks (n=2 from each group), 12 weeks (n=4), and 24 weeks (n=4) postoperatively. Computed tomograms (CT) were taken before and after operations. We dissected the joints, and recorded with the naked eye the shape, degree of erosion, and amount of calcification of the temporomandibular joint (TMJ). In the group in which the lateral peterygoid muscle had not been cut the joints showed overgrowth of new bone and more advanced ankylosis. Our results show that the lateral pterygoid muscle plays an important part in reconstructing the shape of the condyle during the healing of a sagittal fracture of the mandibular condyle, and combined with the dislocated and damaged disc is an important factor in the aetiology of traumatic ankylosis of the TMJ.

Selection of the implant transgingival height for optimal biomechanical properties: a three-dimensional finite element analysis

We evaluated the effects of the transgingival height of an implant on the maximum equivalent stress in jaw bones and the maximum displacement in implant-abutment complex by a finite element method. The transgingival height ranged from 1.0-4.0 mm. Under axial load, the maximum equivalent stress in the cortical bone could be reduced by up to 4.7%, and under a buccolingual load, the maximum equivalent stresses in the cortical and the cancellous bones could be reduced by 17.3% and 18.5%, respectively. The maximum displacement of the implant-abutment complex could be reduced by 4.1% and 48.9% under axial and buccolingual loads, respectively. When the transgingival height was in the range of 1.7-2.8 mm, there was minimum stress in the jaw bones and minimum displacement in the implant-abutment complex. Data indicated that transgingival height played a more important part in protecting a dental implant under a buccolingual load than under an axial load; and transgingival heights ranging from 1.7-2.8 mm were biomechanically optimal for a screwed implant.

A clinical study of ultrasound-guided intralesional injection of bleomycin A5 on venous malformation in cervical-facial region in China

OBJECTIVES To evaluate the therapeutic outcome of ultrasound-guided intralesional injection of bleomycin A5 on treatment of venous malformation (VM) in cervical-facial region. METHODS Seventy-five patients (32 male, 43 female), ranging in age from 13 to 60 years old, suffering from VM in cervical-facial region were admitted to and treated at our hospital between June 2006 and February 2007. Of all the patients, 54 malformations were located in the facial region, eight in the submental region, 10 in the submandible region, and three in the cervical region; all were treated by ultrasound-guided intralesional injections of bleomycin A5. The size of the lesions ranged from 6 x 9 mm to 32 x 39 mm. Injection of bleomycin A5 on venous malformation was then carried out through the inspection of ultrasonography. Repeated course of bleomycin A5 injection was administrated for larger malformations. The amount was 8 mg each time. The therapeutic interval was two to four weeks. The therapeutic outcome on venous malformation was evaluated by physical examination and ultrasonography with Doppler according to the Shou standards, including four grades; cured, basically cured, improved, and invalid. The complications were also observed during and after injection. RESULTS The duration of follow-up ranged from 6 to 24 months. The average times of treatment were 1.64 times. Among them, 42 patients (56%) received only one time of treatment, 21 (28%) patients received two times, nine (12%) patients received three times, and three (4%) patients received four times. According to criteria of therapeutic outcome, the results showed cured in 63 patients (84%), basically cured in 10 patients (13.33%), improved in two patients (2.67%), and none ineffective. Seventy-one patients (94.67%) had local swelling in injection region for several days and two patients (2.67%) developed temporary dizziness after treatment. There were no other complications recorded. CONCLUSIONS Intralesional injection of bleomycin A5 establishes a promisingly effect way for patients suffering from VM in the cervical-facial region under ultrasound guidance.

Matrix metalloproteinase and its inhibitor in temporomandibular joint osteoarthrosis after indirect trauma in young goats.

Our aim was to examine the change in expression of matrix metalloproteinases (MMP-13), matrix metalloproteinases-3 (MMP-3), and tissue inhibitor of matrix metalloproteinase-1 (TIMP-1) in the articular cartilage of goats with experimentally-induced osteoarthrosis of the temporomandibular joint (TMJ) at various times. Osteoarthrosis was induced in 20 goats in the bilateral TMJ and 5 goats acted as controls. There were 5 goats in each group, and a group was killed at 7 days, and 1, 3, and 6 months postoperatively. The samples were collected, and the joints evaluated histologically. Immunofluorescence was used to detect the presence of MMPs and TIMP-1 in the articular disc and condylar cartilage. The ultrastructure of the articular disc and condylar surface at 1 month was examined with scanning electron microscopy (SEM). Osteoarthrosis of the TMJ progressed gradually over time. MMP-13, MMP-3, and TIMP-1 were expressed strongly in the TMJ soon after injury; MMP-13 became gradually weakened, and MMP-3 strengthened later. None of these were expressed in the normal condyle. After a month the surface of the arthrotic condyle was uneven, and the underlying collagen fibrils were exposed in irregular fissures on the surface. The secretion of TIMP-1 was related closely to the changes of MMPs during osteoarthrosis of the TMJ. The unbalanced ratio between them caused degradation of the matrix of the cartilage and might be the cause of osteoarthrosis of the TMJ.

Secondary Healing After Removal of Large Keratocystic Odontogenic Tumor in the Mandible: Enucleation Followed by Open Packing of Iodoform Gauze

PURPOSE The aim of this retrospective study was to present the findings of an open packing method after enucleation of large keratocystic odontogenic tumors (KCOTs) in the mandible. PATIENTS AND METHODS We performed a retrospective case series study of 27 patients with KCOTs larger than 5 cm treated at our institution between September 2003 and September 2008. A conservative surgical treatment was applied, which involved enucleation of the primary lesion and open packing of the residual osseous defect with iodoform gauze for secondary healing. Bone regeneration, tumor recurrence, and surgical complications were observed and analyzed. We used the χ(2) test and Pearson correlation coefficient for statistical analysis. RESULTS The postoperative follow-up time was 52.3 months on average (range, 24 to 84 months). The packing gauze was changed every 2 weeks after enucleation, and the total duration for packing was 10.2 months on average (range, 7-15 months). Bone regeneration and satisfactory secondary healing were observed clinically and radiographically after treatment. Only 1 case had a recurrence 6 months after initial treatment, which was attributed to insufficient bony unroofing during enucleation. The recurrent lesion was re-treated by the same method, and no recurrence occurred in the following 6 years. No serious complications from this method of treatment were observed. No significant variables were found to be related to the recurrence. CONCLUSIONS Enucleation with subsequent open packing was shown to be a conservative and comfortable treatment for patients and appears to be an effective choice for the management of large KCOTs in the mandible.

Alveolar ridge preservation with deproteinized bovine bone graft and collagen membrane and delayed implants.

Abstract To evaluate clinically and radiographically an alveolar ridge, preservation technique with deproteinized bovine bone graft and absorbable collagen membrane and then restoration with delayed implants were done. The study included 30 patients. The trial group’s sockets were filled with deproteinized bovine bone graft (Bio-Oss) and covered with absorbable collagen membrane (Bio-Gide). The control group’s sockets healed without any treatment. Panoramic radiograph and computed tomography were taken immediately after graft and 3 and 6 months later to evaluate the height, width, and volume change of the alveolar ridge bone. Dental implants were inserted in all sockets at 6 months, and osseointegration condition was evaluated in the following 12 months. All sockets healed uneventfully. In the trial group, the mean (SD) height reduction of the alveolar ridge bone was 1.05 (0.24) mm at 3 months and 1.54 (0.25) mm at 6 months. The width reduction was 1.11 (0.13) mm at 3 months and 1.84 (0.35) mm at 6 months. Bone volume reduction was 193.79 (21.47) mm3 at 3 months and 262.06 (33.08) mm3 at 6 months. At the same trend, in the control group, the bone height reduction was 2.12 (0.15) mm at 3 months and 3.26 (0.29) mm at 6 months. The width reduction was 2.72 (0.19) mm at 3 months and 3.56 (0.28) mm at 6 months. Bone volume reduction was 252.19 (37.21) mm3 at 3 months and 342.32 (36.41) mm3 at 6 months. There was a significant difference in alveolar ridge bone height, width, and volume reduction in the 2 groups. The osseointegration condition had no significant difference between the 2 groups. This study suggested that the deproteinized bovine bone graft and absorbable collagen membrane were beneficial to preserve the alveolar ridge bone and had no influence on the osseointegration of delayed implant.