The effects of bone remodeling on biomechanical behavior in a patient with an implant-supported overdenture.

This study aimed to clarify the effects of bone remodeling on biomechanical behavior in a patient with a mandibular implant-supported overdenture by comparing computed tomography-based finite element analyses (CT-FEA) with two time points of CT data. The present FEA was based on CT data collected from a 62-year-old female subject, who wore a mandibular implant overdenture supported by four dental implants with bar attachment. Two kinds of FE models were constructed from CT data taken at two time points: pre-implantation (Original-model) and 12 years post-implantation (Aged-model). FE models consisted of patient-specific model geometry and heterogeneous material properties. The deviation analysis was carried out to assess the changes in bone mass over a period of 12 years. The results show an averaging of intraosseous stress and strain energy density between the implant regions in the Aged-model. The results of the morphological assessments demonstrated that the bone mass and quality had significantly changed over 12 years. Area-specific bone resorption was also observed at the bone surrounding each implant. The combined findings indicate that the averaging of mechanical variables was due to chronological changes in bone morphology, suggesting adaptation to mechanical loads by peri-implant bone remodeling.

Effect of peri-implant bone resorption on mechanical stress in the implant body: In vivo measured load-based finite element analysis.

BACKGROUND: Research on resolving implant fracture is still gaining attention as it can be a serious treatment failure outcome. The implant fracture is likely to occur due to increased stress in implant body associated with peri-implant bone resorption. OBJECTIVE: This study aimed to investigate the relationship between degree of peri-implant bone resorption and stress distribution in implant body by using finite element analysis (FEA). METHODS: The magnitude and direction of loads on implants at the mandibular molar region were measured with 3D piezoelectric force transducers in a patient during maximal voluntary clenching, grinding and tapping to obtain input for the FEA as the loading condition. Simplified finite element bone models were generated to simulate the six patterns of peri-implant bone resorption progression which the bone levels from implant platform were set at 0, 1, 2, 3, 4 and 5 mm. Three types of implants with different diameters (3.5, 4.0 and 5.0 mm), corresponding abutments and screws were created. FEA using the in vivo measured load was conducted to investigate how peri-implant bone loss affects stress distribution in the implant body. RESULTS: Loading condition affected stress distribution in the implant body. As bone resorption increased, von Mises stress in the implant body became larger, which was marked in smaller diameter implants, and this change was amply demonstrated when the bone resorption increased from 0 to 2 mm. CONCLUSION: The FEA demonstrated that as peri-implant bone loss increased, the magnitude of stress in the implant increased, especially in small diameter implants.

Hermeticity of a hollow obturator model using CAD and rapid prototyping technologies.

STATEMENT OF PROBLEM: Although closed hollow obturator prostheses provide the benefit of minimized weight, they also pose challenges. They are complex to fabricate, and contaminated water can easily enter the hollow section through the joined part, making them unsanitary and leading to malodor and increased weight. PURPOSE: The purpose of this in vitro study was to investigate the hermeticity and durability of a hollow obturator model fabricated by using computer-aided design (CAD) and rapid prototyping (RP) techniques and to evaluate the possibility of its clinical use. MATERIAL AND METHODS: Leak testing was used to evaluate the hermeticity and durability of hollow spherical obturator specimens with an outer diameter of 30 mm and 2 different wall thicknesses (1.5 and 2.0 mm). Six specimens were fabricated for each of the wall thicknesses by using CAD and RP techniques. The accumulation of fluids in the hollow obturator specimens was evaluated every day by using megascopic observation with photoirradiation from the base of the specimens. The amount of water absorption and the rate of increase in the weight of the 2 specimens were calculated and compared. Statistical analysis was performed by using the Mann-Whitney U test (α=.05). RESULTS: The application of CAD and RP techniques made it possible to fabricate a hollow obturator model specimen with completely unified parts. The 1.5-mm specimen showed an absorption rate (2.61%) that significantly exceeded that of the 2.0-mm specimen (2.53%) on day 130 (P=.006). By the end of the observation period, the 1.5-mm specimen exhibited large amounts of water absorption and destruction. The 1.5-mm-thick wall had reduced hermeticity than the 2.0-mm-thick wall. CONCLUSIONS: A fully unified hollow obturator model with 2.0-mm-thick walls was fabricated by using CAD and RP techniques. The absence of any joints prevented fluid accumulation, making this method suitable for the fabrication of hollow prostheses.

Changes in oral health-related quality of life after oral rehabilitation with dental implants in patients following mandibular tumor resection.

Oral rehabilitation with prosthodontic treatment considerably influences the well-being and quality of life of patients after ablative oral tumor surgery. This study evaluated the effects of implant-supported prostheses (ISPs) on oral health-related quality of life (OHRQoL) and chewing ability in 10 patients who requested ISPs after mandibular oral tumor resection. OHRQoL was assessed using the Japanese version of the Oral Health Impact Profile (OHIP-49) before and one year after ISP placement. Chewing ability, including self-assessed masticatory ability and occlusal force, was examined at one year after ISP placement. The initial mean total OHIP-49 score of 65.3 ± 9.79 decreased to 46.0 ± 8.14 at one year after ISP placement. Mean OHIP-49 score decreased in all domains, whereas self-assessed masticatory ability increased within one year of ISP placement. There were no significant differences between prosthesis types with respect to the mean OHIP-49 score or self-assessed masticatory ability. In conclusion, ISP placement improves OHRQoL and the self-assessed masticatory ability. Moreover, the prosthesis type might not significantly affect OHRQoL.