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external oblique ridge [keywords]
- Three dimensional finite element analysis of the stress distribution around the mandibular posterior implant during non-working movement according to the amount of cantilever. [Journal Article]
- J Adv Prosthodont 2014 Oct; 6(5):361-71.
In case of large horizontal discrepancy of alveolar ridge due to severe resorption, cantilevered crown is usually an unavoidable treatment modality. The purpose of this study was to evaluate the clinical criteria for the placement of the aforementioned implant crown.The mandible model with 2 mm thick cortical bone and cancellous bone was fabricated from CT cross-section image. An external connection type implant was installed and cantilevered crowns with increasing offset of 3, 4, 5, 6, and 7 mm were connected. Vertical load and 30° oblique load of 300 N was applied and stress around bone and implant component was analyzed. A total of 14 cases were modeled and finite element analysis was performed using COSMOS Works (Solid works Inc, USA).As for the location of the vertical load, the maximum stress generated on the lingual side of the implant became larger according to the increase of offset distance. When the oblique load was applied at 30°, the maximum stress was generated on the buccal side and its magnitude gradually decreased as the distance of the offset load increased to 5 mm. After that point, the magnitude of implant component's stress increased gradually.The results of this study suggest that for the patient with atrophied alveolar ridge following the loss of molar teeth, von-Mises stress on implant components was the lowest under the 30° oblique load at the 5 mm offset point. Further studies for the various crown height and numbers of occusal points are needed to generalize the conclusion of present study.
- What Method for Management of Unilateral Mandibular Angle Fractures Has the Lowest Rate of Postoperative Complications? A Systematic Review and Meta-Analysis. [REVIEW]
- J Oral Maxillofac Surg 2014 Nov; 72(11):2197-2211.
The aim of the present study was to determine which method for internal fixation through a transoral approach has the lowest complication rate for patients with mandibular angle fractures (MAFs).To address our study purpose, we designed and implemented a systematic review with meta-analysis. To identify the studies to include in the review, a comprehensive electronic search without date or language restrictions was performed in April 2014. The inclusion criteria were studies of humans, including randomized or quasi-randomized controlled trials (RCTs), controlled clinical trials (CCTs), and retrospective studies, with the aim of comparing fixation techniques (1 vs 2 miniplates, external oblique ridge vs lateral border miniplate placement, and geometric vs conventional miniplate) in the management of MAFs. The incidence of postoperative complications was analyzed. Only those studies in which a transoral approach had been used (with or without transbuccal instrumentation) were selected.A total of 20 publications were included: 9 RCTs, 3 CCTs, and 8 retrospective studies. Eight studies had a low risk of bias, 11 studies a moderate risk of bias, and 1 a high risk of bias. A statistically significant difference was found between a single superior border miniplate and the use of 2 miniplates. The cumulative odds ratio (OR) was 0.63, indicating that the use of 1 miniplate in MAF fixation decreased the risk of postoperative complications by 37% compared with using 2 miniplates. Comparing a miniplate placed on the external oblique ridge to one placed on the lateral surface of the mandible resulted in a cumulative OR of 2.10, indicating that the use of the transbuccal miniplate decreased the risk of postoperative complications by 110% compared with a miniplate placed on the external oblique ridge. Comparing geometric and standard miniplates, the OR was 0.29, indicating that the use of a geometric miniplate decreased the risk of postoperative complications by 71% compared with using conventional miniplates.The results of the meta-analysis have shown that the use of 1 miniplate is superior to using 2 in reducing the incidence of postoperative complications in the management of MAFs. In addition, our results showed that the transbuccally placed lateral miniplate was better at reducing the incidence of postoperative complications than one placed on the external oblique ridge using a transoral approach. Finally, geometric miniplates performed better than conventional miniplates in reducing postoperative complications.
- 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.