Cortical bone thickness of the mandibular canal and implications for bilateral sagittal split osteotomy: a cadaveric study

Primary and supplementary anesthetic efficacy of a modified two-step buccal infiltration of 4% articaine in mandibular molars with symptomatic irreversible pulpitis: a randomized clinical trial

OBJECTIVES

To evaluate a modified two-step buccal infiltration (MBI) of 1.7 mL 4% articaine as primary or supplemental anesthesia in mandibular first and second molars diagnosed with symptomatic irreversible pulpitis (SIP).

MATERIALS AND METHODS

One hundred and eight patients with SIP were randomly assigned to one of three groups (n = 36). They were given an inferior alveolar nerve block (IANB) of 2% lidocaine with 1:80.000 epinephrine or a primary MBI of 4% articaine with 1:100.000 epinephrine in the IANB and MBI groups, respectively. Patients in the IANB + MBI group received an IANB followed by an MBI. Pain levels during the injection, access cavity preparation, and initial filing were recorded on the Heft-Parker visual analog scale (HP-VAS). No or mild pain (HP-VAS ≤ 54) upon access cavity preparation and initial filing was considered a success. Chi-square and Kruskal-Wallis tests were used to analyze the data.

RESULTS

MBI (77.8%) and IANB + MBI (94.4%) had both significantly higher success rates than IANB (50.0%) (P < .001). However, when the Bonferroni adjustment was applied, there was no statistically significant difference between the MBI and IANB + MBI techniques (P = .041 > .017). MBI was associated with significantly less injection pain than IANB (P < .001).

CONCLUSIONS

Both primary and supplemental MBI with 4% articaine were superior to IANB with 2% lidocaine in mandibular first and second molars diagnosed with SIP. Further research may be needed to confirm the findings of this study.

CLINICAL RELEVANCE

The findings of this study suggest that supplemental or primary MBI can be a clinically viable alternative to IANB, which has a relatively low success rate when managing mandibular molars diagnosed with SIP.

The Mandibular Canal: A Study to Determine If Cortical Bone Exists as a Protective Roof for the Inferior Alveolar Nerve

Placement of dental implants has many inherent risks, of which all clinicians must be aware. One of the most important concepts in dental implantology is avoidance of the vital structures present in the human jaws, which can have both immediate as well as long-standing implications. The inferior alveolar nerve (IAN) is one of these vital structures located in the posterior body of the mandible. Invasion of this sensory nerve with a dental implant can result in transient or permanent paresthesia, anesthesia, or dysesthesia. Radiographic imaging is done routinely order to assess the bone volume prior to implant surgery and plan for a safety zone above the IAN. The IAN is contained within the mandibular canal, and this structure is usually visualized during cone-beam computerized tomography (CBCT) scans. The mandibular canal, as it is viewed on CBCT, appears to have a cortical layer of bone protecting the IAN, and clinicians often discuss a bony layer of protection that can be felt by the clinician during osteotomy preparation. The purpose of this research project was to ascertain whether the mandibular canal has continuous or partial remnants of cortical bone lining the roof of the canal or whether the IAN simply travels through spongy, cancellous bone with no cortical bony protection.

Mandibular Canal Location and Cortical Bone Thickness in Males and Females of Different Age Groups: A Cone-beam Computed Tomography Study

AIM: The purpose of the study was to measure and compare the prevalence of mandibular canal (MC) location variations in regard to mandibular first molars in both genders at different age groups. METHODS: A retrospective study was performed on 80 cone-beam computed tomography scans. Distance between MC and apical apices of first molars, buccal and lingual cortical plates was measured in both sides. RESULTS: 80 scans with 160 sides were analyzed. Distances was measured bilaterally for all scans with mean (5.22 ± 0.77) in men versus (4.1 ± 0.7) in women at group age 31–40 apical to apices of first molars. The mean was (3.77 ± 0.62) in men versus (2.81 ± 0.47) in women at same age group at buccal side, lingually the mean was (4.02 ± 0.67) in men versus (3.67 ± 0.26) in women in the same age group. CONCLUSION: Our study showed that there were decrease in measurements in older age group in both genders and in female groups more than male groups but with no statistical significant difference.

Position of the mandibular canal before and after bilateral sagittal split ramus osteotomy: a cone beam computed tomographic study

The aim of this study was to evaluate the position of the mandibular canal (MC) before and after bilateral sagittal split ramus osteotomy (BSSRO) using cone-beam computed tomography (CT), and to compare the position of the MC in Class II and Class III patients in the preoperative period. Patients were divided into two groups: Class II (n = 38) and Class III (n = 41). Measurements of the superior, inferior, buccal, and lingual distances of the MC in relation to the cortical bone were taken at three levels in the proximal segment of the mandible. Results were analysed using the Kruskal-Wallis test (p < 0.05). In the Class II group the superior distance of the MC at levels 2 and 3, and the inferior distance at level 3 significantly decreased after BSSRO. In the Class III group, no significant differences were found at any level, and the inferior distances at all levels were smaller preoperatively than those in the Class II group. In the Class II group the position of the MC altered in relation to superior and inferior cortical bone after BSSRO. However, the position of the MC remained stable in the Class III group. Our results also suggest a deeper cut in inferior cortical bone in Class III patients.

Mechanical effects of residual bone mass, a maxillofacial prosthesis, and a reconstruction plate on the mandible after marginal resection

In this study, analytic models were used to simulate marginal resection in the area of the second premolar to the second molar region, and the mechanical effects on the mandible of residual bone mass, a maxillofacial prosthesis, and a reconstruction plate were evaluated by three-dimensional finite element analysis. As residual bone mass decreased, maximum principal stress increased near the anterior ramus of the mandible, and maximum shear stress increased at the anterior buccal region of the resected area. In the mandible with a maxillofacial prosthesis, the maximum principal stress distribution at the anterior ramus was lower, and the distribution of maximum shear stress at the anterior buccal region of the resected area was higher. When a reconstruction plate was used, maximum principal stress and maximum shear stress were lower. Thus, lower residual bone mass was associated with increased mandible deflection and torsion. In addition, presence of a maxillofacial prosthesis decreased deflection but increased torsion, and presence of a reconstruction plate decreased deflection and greatly decreased torsion. These findings suggest that decreased residual bone mass and maxillofacial prostheses increase fracture risk; however, presence of a reconstruction plate was effective in decreasing torsional stress, thereby reducing fracture risk in the mandible.

What factors affect the attachment of the inferior alveolar nerve to the buccal plate following sagittal split osteotomy?

PURPOSE

This study aimed to assess the factors that can possibly affect the positioning of the inferior alveolar nerve (IAN) in the proximal or distal segment following sagittal split osteotomy (SSO).

MATERIALS AND METHODS

This was a prospective cohort study. The patients were assigned according to the position of the IAN: the IAN was attached to the buccal plate in group 1 (27 SSOs), while it was in the distal segment in group 2 (83 SSOs).

RESULTS

The mean of the buccolingual thickness of the proximal segment at the vertical cut of the osteotomy (BLTP) was 5.0 ± 0.62 mm in group 1 and 4.16 ± 0.72 mm in group 2. The mean of the distance between the IAN and the external cortical bone at the distal of the second molar before the osteotomy (IANB) was 0.5 ± 0.24 mm in group 1 and 1.24 ± 0.45 mm in group 2. There were significant differences for the mean BLTP and IANB between the two groups (P = 0.001).

CONCLUSION

It seems that the thickness of the buccal plate of the proximal segment, the distance from the IAN to the external cortical bone, the osteotomy technique, and the presence or absence of impacted third molars may be associated with the positioning of the IAN following SSO.

Inferior alveolar nerve canal position in relation to mandibular molars: A cone-beam computed tomography study

Objective

This study was carried out to prevent the risk of iatrogenic injuries to the inferior alveolar nerve (IAN) canal associated with various surgical interventions in the area of mandibular molars, by using cone-beam computed tomography (CBCT).

Materials and Methods

The present retrospective study was carried out by using CBCT of 100 patients between 18 and 40 years of age group. The linear measurements were made in relation to the 1^st and 2^nd mandibular molars on both the sides. Linear distances between buccal and lingual aspects to the mandibular, buccal, and lingual cortical bone thickness; IAN canal diameter; and the superior corticated border of the IAN canal from the periapex of the 1^st and 2^nd mandibular molars. The statistical evaluation was done using SPSS V.20 (SPSS: an IBM company), and P < 0.05 was considered statistically significant.

Results

Both genders of all age groups showed statistically significant result (P < 0.00). All the linear measurements were statistically significant in relation to both the 1^st and 2^nd mandibular molars (P < 0.005), and also the bilateral comparison of the linear measurements showed statistically significant difference in relation to the mandibular 2^nd molar (P < 0.03) and 1^st molar (P < 0.04) among both the sexes.

Conclusion

Clinicians should be aware of the proximity of root apices and cortical plates to the mandibular canal when performing surgical and root canal procedures in the posterior mandible to avoid serious nerve injuries.

Mechanical analysis of the effects of implant position and abutment height on implant-assisted removable partial dentures

PURPOSE

An increasing number of clinical reports describe the use of dental implants as abutments in implant-assisted removable partial dentures (IARPD). We used three-dimensional finite element analysis to evaluate IARPD as a unilateral mandibular distal extension denture. Specifically, the mechanical effects of implant position and abutment height on the abutment tooth, denture, and denture-supporting tissue were assessed.

METHODS

The models analyzed were defects of the left mandibular second premolar and first and second molars prosthetically treated with an IARPD using one implant for each tooth position. There were two abutment heights: one equal to that of the mucosa and another that was elevated 2 mm above the mucosa. Six models were constructed.

RESULTS

For mucosal-level abutments, movement of the abutment tooth was lower for implants positioned distal to the abutment tooth than for those positioned medial to the abutment tooth. For elevated abutments, movement of the abutment tooth was lower for implants positioned medial to the abutment tooth than for those positioned distal to the abutment tooth.

CONCLUSIONS

The mechanical effects on abutment teeth at the same implant position differed in relation to implant abutment height.

Clinical anatomy of the accessory mandibular foramen: application to mandibular ramus osteotomy

PURPOSE

An accessory foramen around the mandibular foramen is called an accessory mandibular foramen (AMF). The clinical anatomy of the AMF has not been well described. The aim of this study was to reveal the clinical anatomy of the AMF for a better understanding of its implication during ramus surgeries.

METHODS

Twenty-two sides fresh-frozen cadaveric heads with a mean age of 76.2 ± 14.4 years at death underwent dissection. The neurovascular bundles passing through the AMF were observed. Additionally, a hemi-face of a latex injected embalmed cadaver was dissected medially to laterally and the neurovascular bundles of the AMF investigated.

RESULTS

A unilateral foramen, bilateral foramina, and absence of foramina were found in 45.4%, 18.2%, and 36.4%, respectively. The origin of the neurovascular bundle entering the AMF was a branch of the maxillary artery in 20% and a tributary of the inferior alveolar vein in 80%. In the latex embalmed cadaver, the AMF was found to contain a branch from the maxillary artery and a tributary of the maxillary vein.

CONCLUSION

Given the practical meaning of the specific AMF located in the operative field of the ramus osteotomy, we suggest these be named "foramina for ramus osteotomy."

Microsurgical Anatomy of the Superior Wall of the Mandibular Canal and Surrounding Structures: Suggestion for New Classifications for Dental Implantology

Our goal was to clarify the relationship between the superior wall of the mandibular canal and the presence of teeth. We also sought to study the structural changes of the mandibular canal after tooth loss. Twenty sides from 10 dry mandibles derived from six males and four females were used for this study. The age of the specimens at the time of death ranged from 57 to 91 years. The mandibles were cut in the midline resulting in 20 hemi-mandibles. The presence of teeth (from the second premolar to the third molar) was recorded for each hemi-mandible. The mandibular canal in the body of the mandible was divided into four areas, that is, Areas 1-4. The superior wall of the mandibular canal and a cancellous bone pattern above the mandibular canal were observed. Next, the mandibular canal was horizontally cut at its center and the superior wall of the mandibular canal observed inferiorly. A total of 75 areas (20 dentulous areas and 55 edentulous areas) were produced. The distal view was classified into three groups, Type I (trabecular pattern), Type II (osteoporotic pattern), and Type III (dense/irregular pattern). The Type I pattern was found in 60.0% (12/20) of the dentulous areas and 32.7% of the edentulous areas. While the Type II pattern was found in 15.0% (23/55) of the dentulous areas and 41.8% of the edentulous areas. The inferior view was classified into four groups depending on the surface of the superior wall of the mandibular canal, that is, Class I (trabecular pattern), Class II (osteoporotic pattern), Class III (dense/irregular pattern), and Class IV (smooth).The Class I pattern was seen most frequently (55.0%) in dentulous areas and the Class IV pattern (45.5%) most frequently in edentulous areas. Based on these results, we conclude that the superior wall of the mandibular canal could change following tooth loss. Clin. Anat. 33:223-231, 2020. © 2019 Wiley Periodicals, Inc.

Comparative Study of the Effect of Paranasal Augmentation With Autologous Bone in Orthognathic Surgery

PURPOSE

The purpose of the present study was to compare the effectiveness of the 3 orthognathic surgical options among the patients who had had mandibular prognathism with a concave midfacial profile.

PATIENTS AND METHODS

A total of 72 patients with mandibular prognathism with a concave midfacial profile were divided into 3 groups. We compared the lateral profile changes using lateral cephalograms. The images were taken before surgery (T0) and at least 6 months to 1 year after surgery (T1). After computerization of the preoperative cephalograms (T0), the surgical changes (T1 minus T0) were measured by computerizing the postoperative cephalograms. Group 1 (n = 21) had undergone bilateral sagittal split osteotomies, group 2 (n = 36) had undergone bilateral sagittal split osteotomy with autologous bone paranasal augmentation, and group 3 (n = 15) had undergone bilateral sagittal split osteotomies and Le Fort I osteotomy.

RESULTS

After surgery, all the landmarks and values showed changes. Among them, quantitative changes could be observed in all the cheek points and cheek lines. The average of the overall cheek points had increased by ∼0.56 mm in group 1, ∼1.85 mm in group 2, and ∼2.39 mm in group 3, horizontally.

CONCLUSIONS

The results of the present study suggest approximately comparative values among the 3 surgical options for patients and surgeons considering orthognathic surgery. In addition, autologous bone paranasal augmentation can be considered as an alternative for Le Fort I osteotomy in specific conditions.

Anatomical position of the mandibular canal in relation to the buccal cortical bone: relevance to sagittal split osteotomy

Objectives

Classification of the degree of postoperative nerve damage according to contact with the mandibular canal and buccal cortical bone has been studied, but there is a lack of research on the difference in postoperative courses according to contact with buccal cortical bone. In this study, we divided patients into groups according to contact between the mandibular canal and the buccal cortical bone, and we compared the position of the mandibular canal in the second and first molar areas.

Materials and Methods

Class III patients who visited the Dankook University Dental Hospital were included in this study. The following measurements were made at the second and first molar positions: (1) length between the outer margin of the mandibular canal and the buccal cortical margin (a); (2) mandibular thickness at the same level (b); (3) Buccolingual ratio=(a)/(b)×100; and (4) length between the inferior margin of the mandibular canal and the inferior cortical margin.

Results

The distances from the canal to the buccal bone and from the canal to the inferior bone and mandibular thickness were significantly larger in Group II than in Group I. The buccolingual ratio of the canal was larger in Group II in the second molar region.

Conclusion

If mandibular canal is in contact with the buccal cortical bone, the canal will run closer to the buccal bone and the inferior border of the mandible in the second and first molar regions.