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external oblique ridge [keywords]
- Impacted third molars in sagittal split osteotomies in mandibular prognathism and micrognathia. [Journal Article]
- Ann Maxillofac Surg 2014 Jan; 4(1):39-44.
The timing of removal of mandibular third molars (M3) in Sagittal Split Osteotomy (SSO) has been an issue of contention. The aim of this retrospective study is to identify the incidence of unfavorable fractures during SSO with the presence of M3 and to identify the association between unfavorable fractures with the factors specifically related to the M3.Retrospective analysis of consecutive bilateral sagittal split osteotomy (BSSO) patient's treatment records of 208 patients treated by a single surgeon was analyzed. The position of M3, fracture details, and demographics were collected. Descriptive statistics and Chi-square tests were employed in SPSS package. A P ≤ 0.05 was taken as significant.There were altogether 416 SSO performed. M3 was completely impacted in 88.9% of all instances, and in 85.6% of the instances, the bulk of the M3 was identified to be above the external oblique ridge. In 59.4% of the cases, M3 was positioned in alignment with the arch as observed during surgery. There were about 27 (6.5%) instances of unfavorable splits. A statistically significant relationship was observed with M3 root morphology and axial position of M3.This study for the first time has confirmed the spatial positioning of M3 as one of the several causes of unfavorable splits during SSO. An impacted M3 that lies below the oblique ridge, distoangularly/vertically oriented, with divergent/supernumerary root would cause unfavorable splits when the spreader is not used properly. Potential causes and influencing factors of the unfavorable splits are discussed.
- Effects of the Implant Design on Peri-Implant Bone Stress and Abutment Micromovement: Three-Dimensional Finite Element Analysis of Original Computer-Aided Design Models. [JOURNAL ARTICLE]
- J Periodontol 2014 May 17.:1-14.
Background: Occlusal overloading causes peri-implant bone resorption. Previous studies examined stress distribution in alveolar bone around commercial implants using three-dimensional finite element analysis (3D-FEA). However, the commercial implants contained some different designs. The purpose of this study was to reveal the effect of the target design on peri-implant bone stress and abutment micromovement. Methods: Six 3D implant models were created for different implant-abutment joints: external and internal models (EM, IM); straight and tapered abutment shapes (SA, TA); platform switching (PS) in the IM; modified TA neck design [reverse conical neck (RN)]. A static load of 100 N was applied to the basal ridge surface of the abutment at a 45° oblique angle to the long axis of the implant. (1) Stress distribution in peri-implant bone, (2) abutment micromovement in SA and TA models were analyzed. Results: Compressive stress concentrated on labial cortical bone and tensile stress on the palatal side in the EM and on the labial side in the IM. There was no difference in maximum principal stress distribution for SA and TA models. Tensile stress concentration was not apparent on labial cortical bone in the PS model (versus IM). Maximum principal stress concentrated more on peri-implant bone in the RN than in the TA model. TA model exhibited less abutment micromovement than the SA model. Conclusions: The study revealed the effects of the design of specific components on peri-implant bone stress and abutment displacement after implant-supported single restoration in the anterior maxilla.
- Iatrogenic mandibular fracture associated with third molar removal after mandibular angle osteotectomy. [Journal Article]
- J Craniofac Surg 2014 May; 25(3):e263-5.
The extraction of mandibular third molars is a common dental procedure. The complications include hemorrhage, pain, dental fracture, the displacement of teeth or fragments, iatrogenic damage or luxation of the second molar, neurologic injuries, soft tissue damage, subcutaneous emphysema, trismus, swelling, infection, and iatrogenic mandibular fracture. Fracture of the angle of the mandible associated with third molar removal is a rare but severe complication. This article describes a case of mandibular angle fracture associated with third molar extraction after mandibular angle osteotectomy, including a brief review of the literature. The removal of the mandibular angle and the outer cortex of the mandible, especially the external oblique ridge, may contribute to the bone fracture. We conclude that the extraction of the lower third molar must be before the removal of the mandibular angle, and a soft diet for at least 4 weeks postoperatively is essential to prevent late mandible fracture.
- [The experimental study of subcutaneous ectopic ossification with different proportional mixtures of human autologous bone and hydroxyapatite in nude mice]. [English Abstract, Journal Article, Research Support, Non-U.S. Gov't]
- Shanghai Kou Qiang Yi Xue 2013 Dec; 22(6):655-8.
To observe the effect of subcutaneous ectopic osteogenesis using different proportional mixtures of hydroxyapatite (HAP) and human mandible in nude mice.After obtaining external oblique ridge of mandible, autologous bone was mixed with HAP according to certain proportion. The mixtures were divided into 5 groups (group A: autologous bone/HAP=2/1; Group B: autologous bone/HAP=1/1; Group C: autologous bone/HAP=1/2; Group D: autologous bone/HAP=a quarter; Group E: HAP). The 5 groups of mixtures were respectively implanted into nude mice subcutaneously. After 8 weeks, the specimens were obtained and hard tissue sections were completed. The new bone formation was measured after trinitrophenol staining. The data was analyzed with SPSS 13.0 software package.The hard tissue section showed that new ectopic bone formation area was 9.1% (Group A), 16.1% (Group B), 6.1% (Group C), 3.8% (Group D), and 1.3% (Group E), respectively. New bone formation was the most in group B, while it was the least in group E. Significant differences were found between group B and other groups(P<0.05). However, there was no significant difference between group E and group C or D (P>0.05). The retention rate of HAP was the most in group E (30.3%) and the least (16.3%) in group A.During 8 weeks, human autologous bone mixed with HAP helps new bone formation in nude mice. The best ratio autologous bone and HAP was 1:1. This study provides certain reference basis for dentist to make lifting surgery outside the maxillary sinus using artificial bone graft. Supported by Science and Technology Project of Ningxia Hui Autonomous Region (2011zys271).
- Transoral Miniplate Fixation of Mandibular Angle Fracture with and without 2 Weeks of Maxillomandibular Fixation: A Clinical Trial Study. [Journal Article]
- Craniomaxillofac Trauma Reconstr 2013 Jun; 6(2):107-14.
Background and Objectives The ideal line of osteosynthesis in mandibular angle fractures indicates that a plate might be placed either along or just below the external oblique ridge. Some authors believe that using one miniplate at this line at the mandibular angle region provides sufficient strength to stabilize the fracture but others imply a second plate is required. Such controversies exist in the use of maxillomandibular fixation (MMF). The intention of the present study was to compare efficiency and complications of using one miniplate with and without MMF in mandibular angle fractures. Methods and Materials Forty patients with facial trauma with mandibular angle fractures including displaced and unfavorable fractures were categorized into two groups of 20 persons. In all patients, one miniplate was placed on the external oblique ridge. In the first group, patients had light maxillomandibular elastic bands just after surgery but no rigid MMF. In the second group, patients had rigid MMF for 2 weeks after surgery. Patients were followed to evaluate complications and treatment efficiency. Conclusions Our study showed that use of a single miniplate in the external oblique ridge is a functionally stable treatment for all types of angle fractures (including displaced and unfavorable fractures) except comminuted and long oblique fractures, which were not included in our study. Use of postoperative MMF did not improve the results.
- Nonsurgical correction of a Class III malocclusion in an adult by miniscrew-assisted mandibular dentition distalization. [Case Reports, Journal Article]
- Am J Orthod Dentofacial Orthop 2013 Jun; 143(6):877-87.
This article reports the successful use of miniscrews in the mandible to treat a 20-year-old Mongolian woman with a chief complaint of anterior crossbite. The patient had a skeletal Class III malocclusion with a mildly protrusive mandible, an anterior crossbite, and a deviated midline. In light of the advantages for reconstruction of the occlusal plane and distal en-masse movement of the mandibular arch, we used a multiloop edgewise archwire in the initial stage. However, the maxillary incisors were in excessive labioversion accompanied by little retraction of the mandibular incisors; these results were obviously not satisfying after 4 months of multiloop edgewise archwire treatment. Two miniscrews were subsequently implanted vertically in the external oblique ridge areas of the bilateral mandibular ramus as skeletal anchorage for en-masse distalization of the mandibular dentition. During treatment, the mandibular anterior teeth were retracted about 4.0 mm without negative lingual inclinations. The movement of the mandibular first molar was almost bodily translation. The maxillary incisors maintained good inclinations by rotating their brackets 180° along with the outstanding performance of the beta-titanium wire. The patient received a harmonious facial balance, an attractive smile, and ideal occlusal relationships. The outcome was stable after 1 year of retention. Our results suggest that the application of miniscrews in the posterior area of the mandible is an effective approach for Class III camouflage treatment. This technique requires minimal compliance and is particularly useful for correcting Class III patients with mild mandibular protrusion and minor crowding.
- [Study of the appearance difference of lower complete denture between functional and anatomic impression techniques]. [English Abstract, Journal Article]
- Shanghai Kou Qiang Yi Xue 2012 Apr; 21(2):170-4.
To compare the difference in oblique external ridge, oblique internal ridge and alveolar process crest of lower complete denture base made through functional impression and anatomic impression techniques.Fifteen patients were chosen to treat with two kinds of complete dentures through functional impression and anatomic impression technique respectively. 3D laser scanner was used to scan the three-dimensional model of the denture base and the differences of the surface structural between two techniques in alveolar process crest, external and internal oblique ridges were analyzed, using paired t test with SPSS 12.0 software package.Between the two techniques, there were significant differences in the areas of internal and external oblique ridge(P<0.01); there was no significant difference in the main support areas(P>0.05).The results explain why there is less tenderness when functional impression technique is applied. The differences measured also indicate that sufficient buffering should be made in external and internal oblique ridge areas in clinic.
- Treatment of mandibular angle fractures - linea obliqua plate versus grid plate. [Comparative Study, Journal Article]
- J Craniomaxillofac Surg 2012 Dec; 40(8):807-11.
To compare treatment outcomes, handling and long term results between two osseo-fixation systems for mandibular angle fractures - the external oblique ridge (external oblique) plate and the grid plate.Sixty patients with mandibular angle fracture were analyzed regarding their operative treatment: 30 patients were treated with an external oblique plate and compared to 30 patients treated with a grid plate on the vestibular cortex. The follow up period was at least 1 year for both groups and the following complications were noted: infection, abnormality in fracture healing, nonunion, pain, hypoaesthesia and dysocclusion.The overall average operation time (from intubation to extubation) was 102.1 min (± 44.1 min). Single sided fractures treated with the grid plate needed in average 81.07 min (± 37.9 min) of operation time while single sided fractures treated with the external oblique plate needed 89.3 min (± 42.2 min). In multiple mandibular fractures, no significant change in the operation time between either plating system was found (118.8 ± 35.2 min). After the follow up period fracture healing was considered clinically complete in all patients, but complications occurred significantly more often in the external oblique group (13.3%; N=8) than in the grid plate group (0%; N=0).Isolated mandibular angle fractures can be more effectively treated using grid plates than using other osteosynthesis techniques. It is an easy to use alternative to conventional miniplate systems with good clinical outcome and fewer complications. An angulated burr and screwdriver has to be used to put on the plate laterally.
- [The stress distribution of mandibular alveolar mucosa under functional impressive complete denture studied by 3-D finite element analysis]. [English Abstract, Journal Article, Research Support, Non-U.S. Gov't]
- Shanghai Kou Qiang Yi Xue 2012 Feb; 21(1):31-5.
To analyze the stress distribution and displacement of the mandibular alveolar mucosa under functional impressive complete denture.CT images were processed by Mimics and Geomagic studio, and the solid models and 3-D finite element models were established by Unigraphics NX. 3-D finite element analysis (3-D FEA) was used to study the stress distribution and displacement on the mandibular alveolar mucosa under functional impressive complete denture and anatomic impressive complete denture.The stress distribution on the mandibular alveolar mucosa under two types of complete denture were consistent, and arranged from large to small order as follow: alveolar process crest of molar area, alveolar process crest of anterior area, external oblique ridge and internal oblique ridge. At alveolar process crest and internal oblique ridge, the stress and Z-axis displacement of functional impressive complete denture were less than those of anatomic impressive complete denture.During masticatory period, the stress distribution on the mandibular alveolar mucosa under functional impressive complete denture is more even and more comprehensive than that under anatomic one.
- Intraoral external oblique ridge compared with transbuccal lateral cortical plate fixation for the treatment of fractures of the mandibular angle: prospective randomised trial. [Journal Article, Randomized Controlled Trial]
- Br J Oral Maxillofac Surg 2012 Jun; 50(4):344-9.
Since the initial description by Michelet et al. and research by Champy et al. the placement of a single, four-hole, monocortical, osteosynthesis plate has been considered an acceptable method of fixation for a fracture of the mandibular angle. We investigated the null hypothesis that there is no difference in the incidence of postoperative removal of an infected plate between miniplates placed on the mandibular external oblique ridge and those placed on the buccal surface of the mandible through a transbuccal approach to treat a fracture of the angle of the mandible. Patients were randomised to having their angle fractures treated with a ridge plate placed intraorally or transbucally. Other variables were investigated including the effect of smoking, drinking alcohol, oral hygiene, and the method of holding the reduction on removal of the plate, occlusal outcome, and degree of preoperative anatomical displacement and postoperative reduction. We also studied the operating time required for the two techniques, the effect of the presence and consequent removal of a wisdom tooth in the line of the fracture, and the effect of delay in taking the patient to theatre for subsequent removal of the plate for infection. Of the 261 angle fractures 34 (13%) plates were removed because of infection, and 6 of these (18%) required a further period of fixation, such as intermaxillary fixation, to treat non-union. The transbuccal plate had a significantly lower postoperative infection rate (6/124, 5%) than the ridge plate (28/137, 20%) (p=0.001). Smoking adversely affected the healing of angle fractures (p=0.000). Displacement of fractures is related to the infection rate (p=0.003), and there are no significant relations between delay in going to theatre or the presence and potential removal of a wisdom tooth in the line of the fracture and infection rate. There was a highly significant difference between the rate of removal of plates placed intraorally on the external oblique ridge, and plates placed transbucally (p=0.000). Transbuccal plates were far less likely to need removal for infection than ridge plates, odds ratio 5.05.