Mandibular reconstruction using the anterior part of ascending ramus: report of two cases

Defining the ascending ramus: A search

STATEMENT OF PROBLEM

Lack of an accepted definition for the ascending ramus of the mandible means no common reference point is available for clinical or research dialogue.

PURPOSE

The purpose of this review was to determine whether the ascending ramus has been defined, by using a search of published studies.

MATERIAL AND METHODS

PubMed was searched, using terms "ascending ramus" and "mandible."

RESULTS

The search found no acceptable definition of the ascending ramus of the mandible.

CONCLUSIONS

An acceptable definition for the ascending ramus of the mandible is lacking, and one is proposed here.

Applications of coronoid process as a bone graft in maxillofacial surgery

The coronoid process can be easily harvested as a donor bone by an intraoral approach during many maxillofacial surgery procedures. The purpose of this study was to evaluate the utility of autogenous coronoid process bone grafts for maxillofacial reconstructive surgery. Twelve patients, who underwent coronoid process grafts for reconstruction of maxillofacial deformities due to trauma, alveolar atrophy, or temporomandibular joint ankylosis, were included in the study. There were 3 orbital defects after extended maxillectomy, 1 blowout fracture of the orbit, 2 cases of reconstruction after temporomandibular joint ankylosis surgery, 1 case of additional chin augmentation following horizontal flip genioplasty, 1 defect of anterior wall of maxilla due to trauma, 2 mandibular defects, and 2 cases of bone augmentation for implants.We recommend the use of coronoid process of the mandible as a source for autogenous bone graft as it can provide sufficient bone in quantity and quality for selected maxillofacial reconstructions.

Occurrence of the retromolar foramen in dry mandibles of South-eastern part of India: a morphological study with review of the literature

The retromolar foramen (RMF) is a rare anatomical structure situated in the retromolar fossa behind the third molar tooth. When it is present, the foramen is connected with the mandibular canal and is believed to transmit neurovascular structures that provide accessory source to the mandibular molars and the buccal area. Reports from the literature show that the presence of RMF could pose a challenge in complete blockage of the inferior alveolar nerve during mandibular surgeries. We report the incidence of retromolar foramen from ninety-four dry mandibles of south-eastern part of Karnataka State, India. The foramen was observed in 11 mandibles out of 94 included in the study (11.7%). In three mandibles, the foramen was present bilaterally (3.2%) and in three it was on the left side (3.2%) and in five it was on the right side (5.3%). For the first time, we also measured the dimensions of the retromolar area and distance of the foramen from third molar tooth to understand its risks during the surgical extraction of the lower third molar tooth. A thorough review of the literature has also been done to compare the present findings with the studies reported from the various populations.

The anomalous canal between two accessory foramina on the mandibular ramus: the temporal crest canal

OBJECTIVES

The temporal crest canal (TCC) is a variation of the bony canal with two accessory foramina that correspond to an entrance and an exit on the mandibular ramus. This study investigated the anatomical characteristics of the TCC using CBCT.

METHODS

The study population consisted 446 patients who had undergone CBCT. Sagittal, cross-sectional and three-dimensional images were evaluated for the presence of a TCC. The canals were classified into two types according to the configuration, and the location of the posterior accessory foramen of the TCC was also recorded.

RESULTS

6 TCCs were present in 4 of 446 patients (0.90% of the total population). All of the TCCs were observed in males, and all of the posterior foramina were located superior to the mandibular foramina on the medial aspect of the mandibular ramus. There were five noticeably curved and increasingly narrow canals (Type 1) and one slightly curved and uniformly wide canal (Type 2).

CONCLUSIONS

Precise knowledge of the TCC is clinically important for suitable local anaesthetic nerve block and the planning of surgical procedures that involve the mandibular ramus. Three-dimensional images of CBCT data are particularly effective for confirming the presence of this variation.

Cone beam CT findings of retromolar canals in a Korean population

PURPOSE

The identification of the variation involving the mandibular canal is important during surgical procedures in the mandible. This study aims to investigate the incidence, course, width, and location of retromolar canals in a Korean population using cone beam CT.

METHODS

The cross-sectional, sagittal, and three dimensional images from volumetric cone beam CT data of 446 patients were reconstructed using imaging analysis software for the presence of a retromolar canal. Retromolar canals were classified into three types according to the courses. The width and location (distance from the second molar) of retromolar canals were evaluated.

RESULTS

A retromolar canal was observed in 8.5 % of patients (38/446). Most retromolar canals had vertically curved courses (Type 1, 66.7 %), followed by horizontally curved courses (Type 2, 20 %). Type 3 retromolar canals, which run independently from separate foramina in the mandibular ramus, were rare (13.3 %). The mean width of a retromolar canal was 1.13 mm (SD ± 0.38, 0.60-2.00), and the mean distance to the second molar was 14.08 mm (SD ± 3.85, 8.50-24.00).

CONCLUSIONS

The incidence of retromolar canals in the Korean population was lower than that reported in the investigated ethnic groups. In the presence of a retromolar canal, local anesthesia may be ineffective. The damage to a retromolar canal may be unavoidable during surgical procedures involving the mandible and may result in paresthesia, excessive bleeding, postoperative hematoma, or traumatic neuroma.

Retromolar foramen and canal: a comprehensive review on its anatomy and clinical applications

The retromolar foramen (RMF) and retromolar canal (RMC) are the anatomical structures of the mandible located in retromolar fossa behind the third molar tooth. This foramen and canal contain neurovascular structures which provide accessory/additional innervation to the mandibular molars and the buccal area. These neurovascular contents of the canal gain more importance in medical and dental practice, because these elements are vulnerable to damage during placement of osteointegrated implants, endodontic treatment and sagittal split osteotomy surgeries and a detailed knowledge of this anatomical variation would be vital in understanding failed inferior alveolar nerve blockage, spread of infection and also metastasis. Although few studies have been conducted in the past showing the incidence and types in different population groups, a lacunae in comprehensive review of this structure is lacking. Though this variation posed challenging situations for the practicing surgeons, it has been quite neglected and the incidence of it is not well presented in all the textbooks. Hence, we made an attempt to provide a consolidated review regarding variations and clinical applications of the RMF and RMC.

Bifid mandibular canal: confirmation of limited cone beam CT findings by gross anatomical and histological investigations

OBJECTIVES

The aims of this study were (1) to assess the validity of limited cone beam CT (CBCT) in detecting the distribution of bifid mandibular canals in the retromolar region by comparing its findings with those of panoramic radiography and spiral CT imaging, and (2) to confirm the contents of such canals depicted on limited CBCT images by using gross anatomical and histological methods.

METHODS

Bilateral bifid mandibular canals of a Japanese cadaver were investigated. The canals depicted on panoramic radiography, spiral CT and limited CBCT images were compared. Cross-sectional limited CBCT images of these canals were compared with gross anatomical sections of the mandible and their contents were confirmed histologically.

RESULTS

The spiral CT and limited CBCT images showed the bilateral bifid mandibular canals in the retromolar region whereas the panoramic radiographs indicated the presence of only the left bifid mandibular canal. The canal distribution was more distinct in the limited CBCT images than in the spiral CT images and the cross-sectional limited CBCT images were consistent with the gross anatomical sections. Histologically, the canals contained several nerve bundles and arteries among which the largest nerve and artery were of a similar size.

CONCLUSION

Limited CBCT is valuable for assessing the distribution of bifid mandibular canals. It is clinically significant to accurately localize a bifid mandibular canal of the retromolar region because it contains a nerve bundle and artery.

Mandibular ramus/coronoid process grafts in maxillofacial reconstructive surgery

PURPOSE

To evaluate the utility of autogenous extended mandibular ramus and coronoid process bone grafts for maxillofacial reconstructive surgery.

PATIENTS AND METHODS

Twelve patients aged 23 to 76 years (mean, 52) who underwent extended ramus/coronoid process grafts for reconstruction of maxillofacial deformities due to trauma, alveolar atrophy, or iatrogenic nasal deformity. All patients had either unilateral or bilateral combined coronoid process-mandibular ramus bone grafts for their reconstruction. There was 1 nasal reconstruction, 2 unilateral mandibles, 1 bilateral mandible, 4 unilateral maxillas, 1 unilateral maxilla and mandible combined, and 1 bilateral maxilla and mandible combined.

RESULTS

The procedure was considered a success when the patient's deformities were reconstructed ad integrum and when there were no failures of the dental implants placed in the augmented areas as of the longest follow-up. All patients were successfully reconstructed. There was 1 infection at a donor site that resolved with local care and oral antibiotics. All but 1 of the maxillary and mandibular alveolar augmentations underwent endosteal implant placement approximately 4 to 6 months following grafting. The nasal reconstruction restored normal function and symmetry.

CONCLUSION

Using both the coronoid process of the mandible and the mandibular ramus as a source for autogenous bone graft can provide sufficient bone in quantity and quality for selected maxillofacial reconstructions.

Clinical and anatomical study of retromolar foramen and canal

PURPOSE

The retromolar canal is a rare anatomic variation of the mandible. The neurovascular content of the mandibular retromolar canal is very important for surgical procedures involving the retromolar area and there has been a lack of information on this subject. This study consists of anatomic research of the retromolar foramen and canal, planned after an impacted third molar tooth extraction operation in which we encountered a retromolar neurovascular bundle.

MATERIALS AND METHODS

Eighty sides of 40 mandibles were evaluated and the presence of the retromolar foramen and its relation to the last teeth, the transverse and sagittal distances of the retromolar trigone, and the distance of the retromolar foramen to the last socket of the arch were measured.

RESULTS

The neurovascular bundle includes striated muscle fibers, thin myelinated nerve fibers, numerous venules and a muscular artery. Of the 40 mandibles included in this study, retromolar foramens were found in 10 (25%). The presence of the retromolar foramen is not dependent on the last teeth of the arch. The dimensions of the retromolar trigone were measured and the presence of the retromolar foramen was found to be nonrelevant to the dimensions of the retromolar trigone. Retromolar foramen distance from the distal edge of the last socket of the arch was found to be 11.91 +/- 6.71 mm and 4.23 +/- 2.30 mm, respectively, from the second and third molars.

CONCLUSIONS

This study therefore clearly establishes the incidence and importance of the retromolar canal. This study shows that the retromolar foramen and canal can be seen occasionally in routine dental surgery. Due to the neurovascular bundle passing through it, the retromolar canal and foramen must be kept in mind in all anesthetic and surgical approaches regarding the retromolar area and mandible.

The medial surface of the mandible as an alternative source of bone grafts in orthognathic surgery

A technique of harvesting bone grafts from the medial surface of the angle of the mandible during a bilateral sagittal split osteotomy procedure is described. In 20 patients who underwent mandibular setback for the correction of class III dentofacial deformities, bone grafts were harvested from the medial mandibular angle and used for simultaneous augmentation of the midface or for interpositioning and stabilization of the maxilla after LeFort I maxillary anterior or inferior repositioning. The mean postoperative follow-up was 6 months (range, 3-12 months). No complications occurred, and postoperative morbidity was similar to that encountered by patients who undergo sagittal split osteotomy without bone harvest. The technique described shows that the medial mandibular angle is a suitable donor site for membranous bone grafts in patients who undergo sagittal split osteotomy.

Dorsal nasal reconstruction using bone harvested from the mandible

PURPOSE

This article describes a technique for reconstructing nasal deformities resulting from trauma. Bone harvested from the lateral ramus/body of the mandible is used to provide nasal support for major nasal deformities.

PATIENTS AND METHODS

Ten patients underwent repair of their nasal deformities with an autogenous bone graft harvested from the mandible. Primary bone grafting was used to repair a nasal deformity associated with a naso-orbito-ethmoidal fracture in 8 patients. Secondarily, 2 patients underwent placement of a graft for correction of a saddle nose deformity.

RESULTS

All patients achieved aesthetic results. There was maintenance of nasal projection and symmetry without displacement of the graft. None of the patients complained of an unnatural hardness of the nasal tip or dorsum. All grafts healed without evidence of infection, dehiscence, or necrosis.

CONCLUSION

The lateral ramus/body of the mandible provide an excellent donor site alternative for nasal reconstruction.

The ascending ramus of the mandible as a donor site in maxillofacial bone grafting

PURPOSE

The goal of this study was to quantify the amount of bone graft material present in the anterior part of ascending ramus while avoiding the inferior alveolar neurovascular bundle injury.

MATERIALS AND METHODS

This study was made on 16 samples of dry skull. Osteotomies were made in front of the mandibular canal from the mandibular notch to 3 mm posterior of the root of the third molar. The dimensions, the surface area, and the volume of the bone grafts were measured and evaluated.

RESULTS

The average dimensions of the graft material obtained from the anterior part of ascending ramus were 37.60 x 33.17 x 22.48 x 9.15 mm; the average bone volume was 2.36 mL; and the average surface area of the graft material was 495.13 mm(2).

CONCLUSION

The results of the present study show that the anterior part of ascending ramus can be used as the donor site for reconstruction of small bone defects in the oral and maxillofacial region.

Evaluation of the mandible as an alternative autogenous bone source for oral and maxillofacial reconstruction

The objective of this study was to quantify the amount of bone graft material present in the different regions of the mandible while avoiding the inferior alveolar neurovascular bundle, mental foramen and tooth injury. The study was carried out on 16 samples of dry, cadaverous skull. The dimensions of the anterior part of ascending ramus, mandibular symphysis and mandibular body in these samples were evaluated. The osteotomy lines in the anterior part of the ascending ramus were made in front of the mandibular canal from the mandibular notch to 3 mm posterior of the root of the third molar. The osteotomy line in the mandibular body was made just medial to the external oblique ridge from the ascending ramus to approximately 3 mm posterior to the mental foramen. Vertical osteotomy lines were then made from the cut ends of the first osteotomy down to the lower border of the mandible. The osteotomy lines in the mandibular symphysis were performed on the mandible with 5-mm safety margins caudal to the expected position of the mandibular dentition, anterior to the position of the mental foramen, and cephalad to the inferior border of the mandible. It was determined that the dimensions of the anterior part of the ascending ramus were 37.60 mm x 33.17 mm x 22.48 mm x 9.15 mm, and the thickest part of the graft material was 12.23 mm. The average horizontal length of the mandibular body bone was 35.10 mm, and the average vertical length was 19.13 mm. The dimensions of the bone graft obtained from the mandibular symphysis were 45.36 mm x 10.31 mm, and the average thickness was 9.63 mm. Based on the results of this study, it is apparent that the different regions of the mandible can reliably be selected as the harvest site in a variety of oral and maxillofacial reconstructive procedures.