A three-dimensional finite element analysis of resected mandibular bone to determine the most stable implant positions for a fixed prosthesis

This study was conducted to determine the most secure implant positioning on the marginally resected mandible to support a fixed complete denture through finite element analysis. Three or four implants were placed at near, middle, or far positions from the resected margin in a simulation model with a symmetrical marginal defect in the mandibular symphysis. The height of the residual bone was 5, 10, or 15 mm. The four possible implant patterns for 3 or 4 implants were defined as: (1) asymmetrically isolated position one to position two, (2) asymmetrically isolated position one to position three, (3) asymmetrically isolated with greater length position one to position two, and (4) two implants symmetrically positioned on each side of the defect. The von Mises stress in the resected and peri-implant bone with respect to the occlusal force was calculated. Initially, as the peri-implant bone stress around isolated implant at the near position was greater than at the middle and far positions regardless of the residual bone height, the near position was excluded. Second, the von Mises stress in the resected bone region was > 10 MPa when the isolated implant was at the far position, and it increased inversely depending on the bone height. However, the stress was < 10 MPa when the isolated implant was placed at the middle position regardless of the bone height, and it was significantly lower compared to the far position, and equivalent to the symmetrically positioned implants. Furthermore, the use of greater length implant reduced the peri-implant bone stress, which was even lower than that of the symmetrically positioned implants. These results suggest that the asymmetrically positioned three-implant-supported fixed denture, using a greater length isolated implant, placed neither too close to nor too far from the resected margin, can be an effective alternative to the symmetrically positioned four-implant-supported fixed denture.

The Length of Peri-Neural Spreading in Clinically Mandibular Invaded Oral Cavity Squamous Cell Carcinoma

Background: The objective of surgical management of oral squamous cell carcinoma (OSCC) is adequate resection with a clear margin. However, there is still a debate as to the optimal length for a mandibular resected margin. Objective: To examine the length of peri-neural spreading in T4 mandibular invaded oral cavity squamous cell carcinoma. Materials and Methods: Twenty-eight T4 pathological OSCC specimens that involved mandible and serial slices were studied and the length of tumor spreading along the inferior alveolar nerve (IAN) was determined. Tumor characteristics, risk factors, and survival were analyzed. Results: The incidence of peri-neural invasion was 11.11%, and IAN invasion was found in 14.29% of the tumor-invaded mandibular marrow. The length of tumor spreading along IAN was 3 to 12 mm. Poor prognostic factors of T4 OSCC were it being located on the tongue (HR 14.16), was pathological N2-3 (HR 31.05), and had high-risk features such as peri-neural invasion, lymphovascular invasion, and extra-nodal extension. Conclusion: A mandibular resected margin of at least 18 mm is recommended as a clear surgical margin in cases of T4 mandibular invasion OSCC. Keywords: Oral cancer, Perineural invasion, Inferior alveolar nerve, Squamous cell carcinoma, Mandibulectomy

The Length of Peri-Neural Spreading in Clinically Mandibular Invaded Oral Cavity Squamous Cell Carcinoma

Background: The objective of surgical management of oral squamous cell carcinoma (OSCC) is adequate resection with a clear margin. However, there is still a debate as to the optimal length for a mandibular resected margin. Objective: To examine the length of peri-neural spreading in T4 mandibular invaded oral cavity squamous cell carcinoma. Materials and Methods: Twenty-eight T4 pathological OSCC specimens that involved mandible and serial slices were studied and the length of tumor spreading along the inferior alveolar nerve (IAN) was determined. Tumor characteristics, risk factors, and survival were analyzed. Results: The incidence of peri-neural invasion was 11.11%, and IAN invasion was found in 14.29% of the tumor-invaded mandibular marrow. The length of tumor spreading along IAN was 3 to 12 mm. Poor prognostic factors of T4 OSCC were it being located on the tongue (HR 14.16), was pathological N2-3 (HR 31.05), and had high-risk features such as peri-neural invasion, lymphovascular invasion, and extra-nodal extension. Conclusion: A mandibular resected margin of at least 18 mm is recommended as a clear surgical margin in cases of T4 mandibular invasion OSCC. Keywords: Oral cancer, Perineural invasion, Inferior alveolar nerve, Squamous cell carcinoma, Mandibulectomy

The Length of Peri-Neural Spreading in Clinically Mandibular Invaded Oral Cavity Squamous Cell Carcinoma

Background: The objective of surgical management of oral squamous cell carcinoma (OSCC) is adequate resection with a clear margin. However, there is still a debate as to the optimal length for a mandibular resected margin. Objective: To examine the length of peri-neural spreading in T4 mandibular invaded oral cavity squamous cell carcinoma. Materials and Methods: Twenty-eight T4 pathological OSCC specimens that involved mandible and serial slices were studied and the length of tumor spreading along the inferior alveolar nerve (IAN) was determined. Tumor characteristics, risk factors, and survival were analyzed. Results: The incidence of peri-neural invasion was 11.11%, and IAN invasion was found in 14.29% of the tumor-invaded mandibular marrow. The length of tumor spreading along IAN was 3 to 12 mm. Poor prognostic factors of T4 OSCC were it being located on the tongue (HR 14.16), was pathological N2-3 (HR 31.05), and had high-risk features such as peri-neural invasion, lymphovascular invasion, and extra-nodal extension. Conclusion: A mandibular resected margin of at least 18 mm is recommended as a clear surgical margin in cases of T4 mandibular invasion OSCC. Keywords: Oral cancer, Perineural invasion, Inferior alveolar nerve, Squamous cell carcinoma, Mandibulectomy