Supramandibular canal portion superior to the fossa of the submaxillary gland: a tomographic evaluation of the cross-sectional dimension in the molar region

Mylohyoid Ridge as a Predictor of Available Bone for Implant Placement: A Cone-Beam Computed Tomography (CBCT) Retrospective Observational Study

Introduction: The posterior mandibular region, due to the presence of vital structures, poses a high risk during implant placement because of its susceptibility to neurovascular injury and perforation of the lingual cortex. A breach in implant length and available bone height may lead to serious intraoperative and postoperative complications. Prediction of the exact location of the inferior alveolar nerve and submandibular fossa anatomy is a prerequisite for ideal implant placement, which is always not possible with conventional radiographic and clinical techniques.

Materials and methods: One hundred ten cone-beam computed tomographies (CBCTs) of patients were acquired from the radiological archives of a radiological center in Chennai. DICOM files from CBCT were exported to Bly Sky Plan software. Cross-sections of the second molar and first molar were extracted following the inclusion criteria. The linear dimension between the mandibular canal and mylohyoid ridge and anatomic variables of the submandibular fossa were measured digitally on the left and right sides using software measuring tools. Descriptive statistics were done. The unilateral and bilateral site and gender differences were evaluated. Bone height superior to the mandibular canal was correlated with the submandibular fossa parameters; depth of undercut in the vertical and horizontal directions; and angle of the undercut.

Results: The mandibular canal was on average 5.5 mm and 4 mm inferior to the Mylohyoid ridge in the second molar region and first molar region, respectively, with the right and left sides showing no statistically significant difference. The depth of fossa undercut in vertical and horizontal dimensions was higher in the second molar region compared to the first molar region. The height of the deepest point of the undercut in the vertical dimensions showed a positive correlation with the bone available between the mandibular canal and the mylohyoid ridge.

Conclusion: Keeping 2 mm of safety factor in consideration, implants can be safely placed up to the mylohyoid ridge in 100% of cases and 2 mm below the mylohyoid ridge in 78.9% of cases in the mandibular second molar region. In keeping with a safety factor of 2 mm, implants can be safely placed up to the mylohyoid ridge in 82.6% of cases and 2 mm below the mylohyoid ridge in 43.1% of cases in the first molar region. A more pronounced undercut was seen in the second molar region than in the first molar region. Deeper fossa undercuts in vertical dimension are associated with more inferior positioning of the mandibular canal.

Prosthetically driven immediate implant placement at lower molar area; an anatomical study

PURPOSE

To examine the effectiveness and safety of immediate implant placement (IIP), we evaluated the risk of lingual plate perforation (LPP) and mandibular canal perforation (MCP) associated with posterior mandible anatomy using cone beam computed tomography (CBCT) images.

MATERIALS AND METHODS

A morphological study of the molar sockets of 135 patients (age: 18-84 y) was done and its relationship to the mandibular canal was investigated. The risk of LPP and MCP was recorded as yes or no. Mandibular cross-sectional morphology was defined as one of three types (U-P-C) using the criteria of Chan et al.

RESULTS

The risk of LPP was significantly higher for second molars (p = 0.0001), and the risk increased with age (p = 0.039). There was a strong relationship between the risk of LPP and cross-section type U (p = 0.0001). The mean root to alveolar canal (RAC) distance (mm) of males was significantly higher than that of females. The mean RAC value was 5.02 mm for males and 3.49 mm for females. There was no statistically significant relationship between the risk of MCP and sex. There was a significant relationship between the risk of MCP and cross-section type U (p = 0.0001). Although the MCP risk was higher in second molars, there was no statistically meaningful relation between MCP and tooth type.

CONCLUSION

The results suggest that IIP in the mandibular molar area carries a high risk of MCP and LPP. Based on the elevated level of risk, a delayed implant protocol should be considered.

Submandibular fossa augmentation in implant dentistry

Background

There are two limiting factors for determining the dental implant fixture length in mandibular posterior edentulous region: Inferior dental canal and submandibular fossa.

Purpose

Submandibular fossa augmentation is a suggested way to overcome the problem of lingual undercut beneath the mylohyoid ridge in implant dentistry.

Materials and Methods

Patients with lingual posterior bony undercut that interferes with the placement of a standard implant with a length of 10 mm were enrolled in this study.

Results

This method was used for eight patients in 10 sites. Increased implant length and decreasing the chance of sublingual hematoma due to lingual cortical plate perforation are the results of this study.

Conclusions

Submandibular fossa augmentation is a new technique to improve the maneuver of oral surgeons to increase dental implant length in the presence of deep lingual bony undercut.