Osseointegration of functionally graded Ti6Al4V porous implants: Histology of the pore network.

The additive manufacturing of titanium into porous geometries offers a means to generate low-stiffness endosseous implants with a greater surface area available for osseointegration. In this work, selective laser melting was used to produce gyroid-based scaffolds with a uniform pore size of 300 µm or functionally graded pore size from 600 µm to 300 µm. Initial in vitro assessment with Saos-2 cells showed favourable cell proliferation at pore sizes of 300 and 600 µm. Following implantation into rabbit tibiae, early histological observations at four weeks indicated some residual inflammation alongside neovessel infiltration into the scaffold interior and some early apposition of mineralized bone tissue. At twelve weeks, both scaffolds were filled with a mixture of adipocyte-rich marrow, micro-capillaries, and mineralized bone tissue. X-ray microcomputed tomography showed a higher bone volume fraction (BV/TV) and percentage of bone-implant contact (BIC) in the implants with 300 µm pores than in the functionally graded specimens. In functionally graded specimens, localized BV/TV measurement was observed to be higher in the innermost region containing smaller pores (estimated at 300-400 µm) than in larger pores at the implant exterior. The unit cell topology of the porous implant was also observed to guide the direction of bone ingrowth by conducting along the implant struts. These results suggest that in vivo experimentation is necessary alongside parametric optimization of functionally graded porous implants to predict short-term and long-term bone apposition.

Factors Modulating Fallow Period of Aerosol-Generating Dental Procedures in a Clinical Setting.

The COVID-19 pandemic has resulted in amended regulations and guidelines governing the practice of dentistry and dental hygiene to ensure the protection of both patients and clinicians from transmission of the SARS-CoV-2 virus. These guidelines include changes in personal protective equipment and, under some guidelines, the institution of a fallow period after any aerosol-generating procedure (AGP). This study aimed to investigate the effect of both ventilation and 4-handed dentistry in clinical practice with patients undergoing supportive periodontal therapy (SPT) by air polishing, ultrasonic and hand instrumentation in a closed operatory. We studied 34 patients during SPT using either 2- or 4-handed dentistry in an operatory with either 0 or 20 additional air changes/h (ACH). Under clinical conditions, 20 additional ACH are adequate to eliminate aerosols produced during an SPT and before the cessation of the AGP. The presence of an assistant had no significant effect on the time needed for aerosol particles to return to baseline values following the AGP. This study supports the efficacy of 20 additional ACH during the process of AGP, but does not support the need for an extended fallow period or 4-handed dentistry to provide additional high-volume evacuation throughout the procedure.