External Oblique Ridge Research Articles

Poster 98: Management of Mandibular Angle Fracture Using 3d Strut Plates - A Pilot Study

The use of rigid fixation methods have been the mainstay in the management of mandibular angle fractures. However these were associated with high complication rates owing to huge implant load, greater periosteal stripping and disruption of vascular supply. The introduction of semirigid fixation methods using Champy's 2 mm miniplate at the inferolateral border of the external oblique ridge transorally has been proved to have the best clinical outcomes, least complications and easier to apply1.

Treatment of mandibular angle fractures – Linea obliqua plate versus grid plate

ObjectivesTo 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. Material and methodsSixty 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 1year for both groups and the following complications were noted: infection, abnormality in fracture healing, nonunion, pain, hypoaesthesia and dysocclusion. ResultsThe overall average operation time (from intubation to extubation) was 102.1min (±44.1min). Single sided fractures treated with the grid plate needed in average 81.07min (±37.9min) of operation time while single sided fractures treated with the external oblique plate needed 89.3min (±42.2min). In multiple mandibular fractures, no significant change in the operation time between either plating system was found (118.8±35.2min).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). ConclusionIsolated 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.

Intraoral external oblique ridge compared with transbuccal lateral cortical plate fixation for the treatment of fractures of the mandibular angle: prospective randomised trial

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.

Distance Between External Cortical Bone and Mandibular Canal for Harvesting Ramus Graft: A Human Cadaver Study

The aims of this study are to determine the distance of the external surface of the buccal cortical plate to the inferior alveolar canal in the mandibular molar region and to propose a safe thickness for harvesting a mandibular ramus block graft. Thirty-four cadavers consisting of 26 dentate jaws and eight jaws in the edentulous molar region were used in this study. All mandibular ramus grafts were harvested by one investigator with the grafts extending from the external oblique ridge (EOR) and 15 mm inferiorly in the apico-coronal direction and extending from the mid-buccal aspect of the first molar to the mid-buccal aspect of the third molar in the mesio-distal direction. Measurements were made of the cortical bone thickness of the harvested ramus graft and from the cemento-enamel junction (CEJ) to the EOR, the CEJ to the mandibular border, and the CEJ to the inferior alveolar nerve (IAN). The average buccal cortical plate thickness in dentate mandibles was 2.76 +/- 0.13 mm, whereas in edentulous posterior mandibles it was 2.52 +/- 0.32 mm. The IANs were exposed in all jaws but were intact. The safe thickness to harvest ramus grafts was determined to be 2.5 to 3.0 mm.

Temporomandibular Joint Reconstruction With Costochondral Graft Using Modified Approach

12 patients presenting with long standing temporomandibular joint (TMJ) ankylosis were treated with a costochondral graft inserted through a modified approach. The age of the patients ranged from 5 to 17 years. A preauricular incision was made for resection of the ankylosed condyle. After release of the ankylosis the contralateral rib was harvested with costal cartilage. An intra-oral incision was made along the external oblique ridge to the mucobuccal fold and was used for resection of the coronoid process and insertion and fixation of the graft. The graft was fixed with a minimum of three titanium screws. The patients were instructed to start physiotherapy 1 week postoperatively and were followed up clinically and radiographically using 3D CT. Postoperative results were encouraging, the graft took well in all patients without postoperative infection or graft rejection. The graft was properly positioned in all cases. There were no visible scars as the preauricular scar is relatively hidden, no possibility of damaging the facial nerve or the marginal mandibular branch and shorter operating time.

Ridge plates versus transbuccal plates in the management of mandibular angle fractures; a prospective randomised trial

Aim: To assess whether there is a difference between the postoperative infection rate, occlusion and anatomical reduction of fractures of the angle of the mandible treated by an osteosynthesis plate positioned on the external oblique ridge via an intraoral approach or on the lateral aspect of the mandible via a transbucaal approach. Study design: A prospective randomised trial. Ethics committee approval was obtained and 350 consecutive patients, who provided consent, were entered into the trial over a period of 2½ years. Statistical analysis was performed using Fisher's Exact Test and Pearson Chi-Square Test. Results: Infection resulted in plate removal in 13% of patients. Fractured angles of the mandible treated via a transbuccal approach experienced significantly less infection ( P < 0.000). Smoking is related to increased risk of postoperative infection ( P < 0.00). Analysis was also made of oral hygiene, degree of fracture displacement, delay between incident and operative procedure, method of fracture reduction, alcohol consumption and postoperative occlusion. Conclusion: Fractures of the angle of the mandible should managed with an osteosynthesis plate placed on the lateral aspect of the mandible via a transbuccal approach.

Poster 207: Mandibular Angle Contour Surgery

Angular prominence of the mandible is an esthetic problem for some Asian women. Reduction of a prominent angle of the mandible is often requested to improve body image. We approach the reduction of the angle of the mandible differently depending on the lower facial contours. A prominent mandibular genial angle is reduced by angle resection. Oscillating saws are used to reshape the prominent mandibular angle into a smooth and round curve at the angle. A curved rasp, in a reciprocating saw hand piece, is helpful for smoothing the irregular bony cut surface. A square face with wide mandibular angles is reduced by a capital ostectomy of the outer cortex of the mandibular angle and posterior body. A horizontal bony incision is made from the external oblique ridge to the posterior border of the mandible. Then a reciprocating saw is used to osteotomize the external cortex of the lower third of the ramus and the lower two thirds of the posterior body of the mandible. An additional reduction procedure is added in patients with masseteric hyperplasia. Condylar fracture, bleeding from the facial artery, asymmetry, hypoesthesia of the lower lip, and unnatural appearance are the possible complications associated with mandible reduction surgery. Experienced oral and maxillofacial surgeons with advanced knowledge of the anatomy, physiology and pathology with the appropriate surgical skills should be able to avoid these complications.

The segmental ridge-split procedure.

This report details surgical procedures for ridge expansion by means of splitting the crest of an edentulous ridge. Atrophic bony ridges present a unique challenge to the dental implant surgeon. In the past, onlay grafts of bone harvested from the hip, maxillary tuberosity, symphysis of the chin, or external oblique ridge have all been used with success in reconstruction of atrophic ridges. However, bone onlay grafting procedures require a secondary surgical site, which exhibits typical postoperative morbidity associated with bone harvesting performed with chisels and burs. Additionally, onlay grafts often require a healing period of 6 months to a year before dental implants can be placed, and the onlay graft sometimes fails to fuse to the augmented site. The segmental ridge-split procedure provides a quicker method wherein an atrophic ridge can be predictably expanded and grafted with bone allograft, eliminating the need for a second surgical site.

A computer study of biodegradable plates for internal fixation of mandibular angle fractures

Purpose: This computer-based study was performed to determine the suitability of small biodegradable plate systems for mandibular angle fractures. Materials and Methods: In a 3-dimensional computer model of the mandible, fracture mobility and plate strain were calculated for bite forces applied on 13 bite points on the dental arch. The angle fracture was fixed with 2 polylactide (PLA) midiplates or with 2 PLA maxiplates. The first plate was positioned buccally on the external oblique ridge. Two positions of the second plate were studied: halfway up the height of the mandible or on the lower border. Maximum fracture mobility was set at a limit of 150 μm to enable undisturbed fracture healing. Maximum plate strain was set at the yield strain of PLA. Results: Fixation with the PLA maxiplates, with the second plate positioned halfway up the height of the mandible, resulted in fracture mobility below the set limit for all bite points. For the other PLA fixation strategies, fracture mobility exceeded the set limit. Fixation with the second plate positioned halfway up the height of the mandible generally resulted in less fracture mobility than with the plate positioned on the lower border. The yield strain of PLA was not exceeded in any of the fixation strategies. Conclusions: Based on the computer model, 2 PLA maxiplates are suitable for fixation of mandibular angle fractures. One plate should be positioned buccally on the external oblique ridge, and the other should be positioned halfway up the height of the mandible. © 2001 American Association of Oral and Maxillofacial Surgeons

Comparison between the rigidity of bicortical screws and a miniplate for fixation of a mandibular setback after a simulated bilateral sagittal split osteotomy

Purpose: This investigation compared the biomechanical stability of three bicortical screws with that of a single four-hole miniplate after 5-mm mandibular setback after a bilateral sagittal split osteotomy (BSSO) in cadaver mandibles. Materials and Methods: Thirty human cadaver hemimandibles underwent BSSO followed by two different rigid fixation techniques. All specimens had no third molar, bony pathology, or evidence of mandibular fracture, and there was no history of renal disease or hyperparathyroidism. The specimens were randomly divided into two groups. In group I, three bicortical screws were placed at the superior border, and in group II, one four-hole miniplate was secured on the external oblique ridge with four monocortical screws. The bony height of the mandible was recorded. Maximum resistance load (MRL), the greatest load recorded just before a sudden decrease in load level (bone or fixation failure), was recorded when the mandibles were tested in a compression machine. Multiple regression analysis was used to evaluate the differences in bone height and the MRL between groups I and II. Results: The mean bone height in groups I and II were 28.64 ± 2.50 mm and 28.72 ± 4.08 mm, respectively. The mean MRL in group I (20.49 ± 7.22 kg) was greater than in group II (17.41 ± 7.81 kg). The multiple regression analysis showed no significant difference in the bone height and the MRL between group I and group II (beta = 2.3492, P = .4114). Conclusion: There was no statistically significant difference in stability provided the two techniques.

Surgical anatomy of the buccal nerve

The buccal nerve may be damaged during surgical procedures which require an incision along the external oblique ridge of the mandible and this study was undertaken to clarify its surgical anatomy. The course and relationships of the nerve were determined in 20 formalin-fixed cadaver specimens. The number of major branches of the nerve ranged from 4 to 8 and a mean of 3 branches was present as the nerve crossed the external oblique ridge. In 14 dissections the main trunk of the nerve crossed the external oblique ridge within 3 mm of the deepest concavity, but in the other 6 it was 7–12 mm below this point. We conclude that incisions even 12 mm below the deepest concavity in the external oblique ridge could result in buccal nerve damage.

Modified technique for adapting a mandibular angle superior border plate

The use of a superior border plate for fixation of a fractured mandibular angle is not a new technique. Michelet et al I and Champy et al 2 describe the use of miniplates in the treatment of such mandible fractures. The difficulty with using a superior border plate, however, has been the varying angulation of the external oblique ridge, creating cumbersome access and placement. The following technique describes a modification using a large round bur to create a flat surface on which the plate is then easily adapted and fixated.

Prospective Review Of Integral Implants

There are several factors that strongly correlate to HA-coated implant success and the prevention of implant morbidity. Surgical placement must be performed without compromise in technique. Implants placed into thin ridges or those that had dehiscence of their surface did not uniformly gain bone attachment levels during the healing period. Countersinking implants in extraction sites was critical; labial bone implant defects should be grafted with particulate HA. HA grafts to labial bone defects at the time of implant placement surgery are still short-term. Primary closure of all implant surgical sites prevented epithelial invagination into the surgical site and is associated with improved bone height around implants. Premature exposure of the implant during the healing period is associated with crestal bone loss. Loading forces should be physiologic, with maintenance of a physiologic equilibrium by a balanced restoration. Bone bulk should be created or preserved. Bone around implants may adversely respond to excessive loading forces. In the posterior maxilla, crestal bone loss has been observed that seems to result from excessive cantilever-type forces placed on the implants or from when implants are placed in the posterior mandible developed progressive bone loss that was associated with several factors. These factors included articulation against a natural occlusion, a horizontal ridge contour level with the external oblique ridge, a nonhygienic restoration, and the lack of keratinized gingiva against the abutment. Whether titanium implants develop progressive bone loss in the face of these factors is unknown. The presence of keratinized gingiva strongly correlated to bone maintenance in the posterior mandible. Because of this statistically significant finding, implant exposure should preserve all keratinized gingiva by transposing it labially to the implants. Most patients who receive implants for dental restoration have lost teeth because of caries and periodontal disease. The patient's behavioural patterns need to be redirected to maintain excellent oral hygiene in order to prevent peri-implant gingivitis. A hygienic restoration may be one of the most important factors associated with excellent implant health. Immediately upon receiving their restoration, patients did well maintaining their peri-implant hygiene. However, many patients do not continue their peri-implant hygiene. However, many patients do not continue their new hygiene methods and need to be strongly reminded to maintain their oral hygiene. Some patients do better than others. For some, a porcelain restoration with the restoration subgingival is well tended, but for others 4 to 5 mm of space needs to be established in order to prevent gingival problems.(ABSTRACT TRUNCATED AT 400 WORDS)

Dental radiology and oral pathology

This article represents an overview of normal and pathological findings of the oral structures for the practicing radiologist. Some of the disease processes discussed are of dental etiology, whereas others are manifestations of systemic diseases. Normal tooth development is described followed by an overview of radiolucent, radiopaque, and mixed lucent-opaque lesions. In the radiolucent category, normal anatomical landmarks of the jaws include the mental foramen, mandibular canal, incisive canal and maxillary sinuses. Other lucencies that represent normal structures or variations include developing tooth buds and root apices, healing dental extraction sites, prominent submandibular fossae and nutrient canals. In the radiopaque category, normal anatomical landmarks of the jaws include the genial tubercle, mental ridge, external oblique ridge, walls of the submandibular canal, walls of the maxillary sinus, nasal septum, stylohyoid ligament, and zygomatic process. Other opacities that represent normal structures or variations include dental restoration material, dental endodontic material, retained roots, sialoliths, salivary duct calculi, calcified lymph nodes, recent extraction sites, hypercementosis, and foreign bodies. Pathological entities which present radiographically as lucencies, opacities, and mixed lucent-opaque areas include inflammatory lesions, cysts, fibro-osseous disease, benign neoplasms, malignant neoplasms, and lesions secondary to metabolic disorders.

Mandibular anatomy as it relates to rigid fixation of the sagittal ramus split osteotomy

Rigid fixation of osteotomy segments is frequently used to reduce relapse and allow for early mobilization of the mandible following the sagittal ramus split osteotomy. This study evaluated cortical bone thickness in the retromolar area of 49 human mandibles to determine if there is an advantage (in terms of cortical thickness) to placement of screws for rigid fixation at the external oblique ridge versus placement at the inferior border. The mandibles were sectioned vertically at three sites in the retromolar area, corresponding to the bone available for rigid fixation of the sagittal osteotomy. Cortical bone thickness was measured at the external oblique ridge and 5 mm above the inferior border. The buccal and lingual cortices were found to be significantly ( P < .001) thicker at the external oblique ridge than at the inferior border. This suggests that there may be an advantage in terms of stability to placement of internal fixation screws at the superior border.

下がく枝斜矢状切離こう合改善術とその術後評価 Ｉ 手術法と術中・術後の合併症

The method of intraoral oblique sagittal splitting oseotomy, a new modification of the sagittal splitting osteotomy, is presented. This procedure is distinct from Obwegeser-Dal Pont method in the following two points; 1. Horizontal osseous incision is made through the cortex medially, extending just only posterior and superior to the lingula. 2. Lateral bone cut is performed down the anterir border of the ascending ramus along the external oblique ridge directly to the inferior border of the mandible with slight oblique direction to the sagittal plane, not extending to the second molar.Thirty-two mandibular prognathism patients with or without anterior open bite have been corrected by this procedure. The advantages of this technique are reduction of operating time, less blood loss and fewer complications. This osteotomy is indicatd for mandibular prognathism with less than 15mm set back required.

Clinical application of the functional matrix: mandibular reconstruction and monobloc functional therapy

A 13-year-old black girl with an extensive ameloblastoma of the mandible required subtotal mandibular resection and immediate reconstruction with use of an autogenous, ipsilateral, corticocancellous graft from the iliac crest and monobic functional therapy. Twenty-seven months later, clinical evaluation showed normal mandibular function and no facial asymmetry. Bony architectural changes after 27 months included reformation of the coronoid process, angular process, and external oblique ridge; preservation of mandibular length and thickness; and maintenance of the alveolar ridge height. The reformation of the coronoid process suggests the importance of the functional matrix (temporalis muscle) in skeletal tissue growth. The monobloc appliance in conjunction with bone grafting is an effective means for transmission of biophysical stimuli and for maintenance of appropriate stress for remodeling of bone in the mandible.

Rationale for the Lingual Approach to Mandibular Osseous Surgery

The definitive treatment of periodontitis for pocket elimination and the establishment of periodontal architecture that can be effectively maintained with daily personal oral hygiene techniques is sometimes an elusive goal. Performing osseous reduction, primarily from the lingual aspect of the posterior mandible, definitely helps in accomplishing such a goal. This paper should not be interpreted to mean that osseous correction of bony defects should be approached strictly from the lingual, since almost all cases require some buccal recontouring if a satisfactory soft and hard tissue architectural form is to be achieved. Clinical observation and experience have shown that the anatomical patterns, seen in relation to the mandible, have a powerful effect on normal periodontal architecture as well as the types and locations of bony defects encountered. Tooth to bone relationships deserve attention. The buccal housing of the alveolar bone is frequently thin in the premolar region and occasionally on the first molar, while the external oblique ridge causes thicknened bone over the second molar. The vestibular depth on the buccal of the molars is often quite shallow, meaning that only a very limited amount of osteoplasty-osteoectomy can be performed from the buccal. The lingual housing of the alveolar bone is normally thickened and shelf-like from the distal of the third molars to the mesial aspect of the premolar region. Because the posterior teeth are inclined lingually from the second premolar distally, the buccal marginal bone height is higher occlusally than the lingual bone margins, with the interproximal bone therefore sloping somewhat apically and lingually. Interdental craters are the most common defect seen with the onset of periodontitis. Such defects in the lower arch tend to occur beneath the contact areas of the teeth, which are much further to the lingual than in the maxilla. The highest percentage of interproximal craters are shallow and not amenable to grafting techniques in the hands of most clinicians. These shallow craters are prime candidates for osseous reduction techniques. With the progression of periodontitis, the interproximal defects frequently extend to include infrabony lingual defects. Although obtaining lingual access for osseous reduction techniques is often difficult, osteoectomy-osteoplasty techniques performed primarily from the buccal of the posterior mandible frequently result in compromise of the lingual and over treating the buccal in terms of osteoectomy procedures. The lingual embrasure spaces are usually wider than on the buccal, and with adequate reduction of the mylohyoid ridge, greater access for oral hygiene procedures is provided.

Evaluation of postoperative localized osteitis in mandibular third molar surgery

A review of localized osteitis and a study of its occurrence in mandibular third molar surgery are presented, with a review of the literature and an evaluation of 1,080 procedures. In the procedures reviewed, a significantly increased incidence of localized osteitis was found to occur in women taking oral contraceptives and in those cases in which surgical access demanded elevation of a mucoperiosteal flap to expose the external oblique ridge of the mandible. Findings also indicate no advantage in suturing for approximation of the mucoperiosteal flap, provided the flap returns passively to its desired position.

Variable denture-limiting structures of the edentulous mouth: Part II. Maxillary border areas

The limiting structures of the mandibular arch exhibit greater variation than those of the maxillary arch, but the problems they present are not insurmountable. The variables considered in this article include: (1) the effect of tongue movement on the shape of the sublingual crescent space, (2) the prominence of the genioglossus attachment, (3) the prominence of the lingual ledge, (4) the proximity of the retromolar pad to the maxillary tuberosity at the established interridge distance, (5) the position of the external oblique ridge in relation to the residual ridge crest, (6) the positions of the buccinator and mylohyoid muscle attachments in relation to the ridge crest, (7) the activity of the mentalis muscle, and (8) habits and degree of neuromuscular control.