The Nippon Dental University

Bisphosphonate-related osteonecrosis of the jaw (BRONJ) is a debilitating condition characterized by alveolar bone destruction associated with bisphosphonate medications, such as zoledronate. Zoledronate use is associated with an increased incidence of BRONJ. In rodent models, accurate replication of BRONJ stages depends on the route of zoledronate administration. This systematic review evaluates the reproducibility of BRONJ characteristics in rodent models by analyzing the effects of different zoledronate injection routes on clinical, histopathological, and radiological outcomes.

A systematic literature search was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analysis guidelines using keywords related to BRONJ and zoledronate. The following data were collected from the selected studies: characteristics of mice and rats; zoledronate dose, duration, and route of administration. The BRONJ stage was determined in these studies based on clinical, histopathological, and radiological features of alveolar bone necrosis.

Zoledronate treatment notably affected the reproducibility of BRONJ characteristics. Mice and rats exhibited distinct characteristics in producing BRONJ, depending on the route of zoledronate injection. Subcutaneous, intraperitoneal (IP), and intravenous (IV) injections in rats consistently produced exposed alveolar bone, the main criterion for clinical BRONJ. IP and IV zoledronate injection in mice produced a clinical BRONJ model. Neither mice nor rats exhibited differences in BRONJ characteristics according to sex.

Rodent models of BRONJ mimic the staging and characteristics of BRONJ observed in humans. Rat BRONJ models were more consistently reproducible when the zoledronate administration route was tailored to achieve specific research objectives.

Dental implants have become a reliable solution for oral rehabilitation, but their long-term success can be compromised by factors such as mechanical overload. To ensure the mechanical durability of implants, standardized testing in accordance with the DIN EN ISO 14801 is conducted, in which titanium implants (Young's modulus of approximately 100 GPa) are embedded in brass, a material with similarly high stiffness. However, the mechanical properties of brass differ significantly from those of alveolar bone, potentially affecting test outcomes. This study examines how different embedding materials affect the mechanical behavior of dental implants, specifically microgap changes and deformation at the IAC under load.

Two conical dental implants were embedded in either methyl methacrylate-based adhesive (PMMA) or brass. A 250 N load was applied at a 45° angle to the implants. Synchrotron-based microcomputed tomography (µCT) was used to assess microgap formation and 3D deformation at the implant shoulder before and under load application. Deformation was analyzed using Avizo Fire software to estimate volumetric changes at the implant shoulder.

The results showed that implants embedded in brass exhibited larger microgap changes (53 μm) and greater deformation at the implant shoulder (32 μm) compared to those embedded in PMMA (microgap: 40 μm).

The findings suggest that brass, with higher stiffness than PMMA or bone, does not accurately replicate the mechanical conditions of bone, leading to a difference in microgap behavior and deformation at the implant shoulder, suggesting a difference in the wear mechanism and stress-strain distribution in the surrounding bone. These results question the use of brass in mechanical implant testing and highlight the need for more realistic embedding materials to improve the predictive value of implant testing.

The aim of this study was performed to investigate the apparent diffusion coefficient (ADC) for distinguishing between benign and malignant lesions in submandibular and sublingual spaces.

Thirteen patients with benign and malignant lesions in submandibular and sublingual spaces were evaluated by MRI. The MRI were obtained by a 1.5 T MR unit using a head coil, and included T1-weighted image (T1WI), T2-weighted image (T2WI) and diffusion-weighted image (DWI). The ADC maps were calculated automatically by the DWI obtained with b = 800 s/mm². We placed regions of interest (ROI) to measure the ADC values on ADC maps, and the ADC value were automatically analyzed. The ADC in benign and malignant lesions were compared by Mann-Whitney U test with a 5% significance level.

Regarding all lesions, T1WI, T2WI and DWI showed low-, high- and high-signal intensity area, respectively. The ADC of malignant lesions (1.10 ± 0.05 × 10^-3 mm²s^-1) was lower than those of benign lesions (2.36 ± 0.64 × 10^-3 mm²s^-1, p = 0.001).

The ADC could be effective for the objectively and quantitatively diagnosis of submandibular and sublingual malignant tumors.