How to design a more stable dental implant: A topology optimization approach

The body shape design is one of the most influential factors in the success of dental implants. This study presents a strategy to design the geometrical features of a threaded implant. The topology optimization technique is applied to identify appropriate spaces in the implant body to be removed for bone growth. The exact shape, position, and dimensions of the spaces are determined using a finite element model. This model consists of a mandibular segment, implant, abutment, and crown. During the optimization process, some grooves and holes are created in the implant by removing redundant materials. Bone growth into these spaces causes mechanical locking between the implant and surrounding bone. The smoothing process is performed following the optimization to remove stress concentration. The results indicate that this design strategy reduces the maximum displacement of the implant by approximately 20%. Moreover, a reduction in the implant’s volume and an increase in the contact area between the implant and bone are obtained. All mentioned issues would increase the stability and reduce the risk of implant loosening. Finally, using conventional production methods, the optimal implant was produced from titanium alloy to demonstrate the possibility of production of the proposed design.

Ossification of Non-vascularized Free-Fibula Graft for Mandibular Reconstruction after Resection of Ameloblastoma: Review of Literature and Presentation of 2 cases

Introduction: Ameloblastoma is a benign neoplasm of odontogenic epithelial origin occurring more commonly in the mandibular posterior region and rarely in the maxilla. About 50-60% of ameloblastomas occur in the mandibular ramus area, while only 10% is seen in mandibular anterior region. Ameloblastomas are slow growing, locally invasive, rarely malignant tumours affecting the jaw. Mostly commonly seen in the 4th-6th decade of life affecting males more commonly than females. The resection of the mandibular segment without adequate reconstruction leads to functional as well as esthetic loss. Case Report: Here we describe two case reports of ameloblastoma with segmental resection and reconstruction using fibula graft. Discussion & Review of Literature: Avascular fibula graft with its high bone density, ease of access to harvest, and tendency to show less resorption helps to achieve satisfactory esthetic contour and function in reconstruction of segmental defects of mandible Conclusion: This article describes two case reports of ameloblastoma with segmental resection and reconstruction using fibula graft along with review of literature.

Defining giant mandibular ameloblastomas – Is a separate clinical sub-entity warranted?

ABSTRACT Context: The term giant mandibular ameloblastoma (GMAs) while being in popular usage in the medical literature remains largely equivocal. Although a few authors have in the past attempted to ascribe definite criteria to this entity, these are by and large arbitrary and without any benefit in decision-making or contributing to its management. Aims: The aim of this study is to propose a set of objective criteria for GMAs that can be clinically correlated and thereby aid in the management of this entity. Patients and Methods: Of a total of 16 patients with ameloblastoma of the mandible presenting at our institute from August 2012 to September 2016, 11 patients were identified as having GMAs as per the criteria proposed. Results: The defects in the mandible following segmental resection ranged from 7 to 11.5 cm in length (mean: 9.3 cm). No clinical or radiological evidence of tumour recurrence was found during a mean follow-up period of 10.7 months (range: 2–28 months). Conclusions: Defining GMA based on objective inclusion and exclusion criteria allows segregation of these lesions, thereby helping to remove ambiguity, simplify decision-making and facilitate communication among treating reconstructive surgeons. Inclusion criteria include: (i) The segmental bone defect following resection with a minimum 1 cm margin of healthy bone should exceed 6 cm (ii) The segmental bone defect should involve the central mandibular segment.

The comparative biomechanics of the reinforced interdental crossover and the Stout loop composite splints for mandibular fracture repair in dogs

Summary Objectives: To describe a new technique, the reinforced interdental crossover composite splint (RIC), for transverse mandibular fracture repair in dogs. This technique was compared biomechanically with the established reinforced interdental Stout loop composite splint (RIS) technique. Methods: Six pairs of mandibles from young adult small breed dogs were used for the study. Osteotomies were created in a standardized fashion and fixed with either RIC or RIS. All composite splint constructs were tested biomechanically with a cantilever bending force, using a single column testing machine at a rate of 2 mm/min. The time of application, amount of composite used, ultimate force, stiffness, total displacement, and total energy absorbed during displacement of the rostral mandibular segment were calculated and compared between the two groups. Results: No significant difference was found when comparing the time of application of the RIC and the RIS techniques. All implants failed by either composite resin fracture over the region of the osteotomy or by fracture between the first and second molar followed by detachment of the resin from the lingual enamel surface of the first molar. Differences between the RIC and RIS in force (80.5 N ± 40.3 and 51.8 N ± 27.4. respectively) and stiffness (16.2 N/mm ± 4.4 and 10.1 N/mm ± 4.1 respectively) were significant (p = 0.03). However differences between the two techniques in displacement and total energy absorbed were not significant. Clinical significance: In experimentally fractured mandibles of young adult dogs there is evidence that RIC is biomechanically similar to RIS.