The SspB cysteine protease of Staphylococcus aureus is expressed in an operon, flanked by the sspA serine protease, and sspC, encoding a 12.9-kDa protein of unknown function. SspB was expressed as a 40-kDa prepropeptide pSspB, which did not undergo autocatalytic maturation. Activity of pSspB was reduced compared with 22-kDa mature SspB, but it was equivalent to mature SspB after incubation with SspA, which specifically removed the pSspB N-terminal propeptide. SspC abrogated the activity of pSspB when incubated in a 1:1 complex but had no effect on SspA or papain. Activity of the pSspB⅐SspC complex was restored when incubated with SspA, and SspC was cleaved by SspA but not pSspB. Thus, SspC maintains pSspB as an inert zymogen, and SspA is required for removal of the propeptide and inactivation of SspC. Like the papain protease family, SspB cleaved substrates with a hydrophobic amino acid at P2 but had a strong preference for arginine at P1. It did not cleave casein, serum albumin, IgG, or IgA, but it promoted detachment of cultured keratinocytes and cleaved fibronectin and fibrinogen at sites recognized by urokinase plasminogen activator and plasmin, respectively. It also processed high molecular weight kininogen in a manner resembling plasma kallikrein. Thus, SspB exhibits a novel maturation mechanism and mimics the specificity of plasma serine proteases.

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Effective apical irrigation is one of the most important root canal procedures that has stood as a long‐standing challenge for the clinician. Despite the myriad of technological advances seen in the last few decades such as nickel–titanium rotary files of various designs and new irrigation delivery systems, very few seem to reliably impact upon a clinician's ability to deliver and replenish irrigant in the most apical part of a root canal. Replenishing irrigant in the apical third is complicated by the multitude of factors that affect the efficacy of this procedure. The current research provides detailed insight on how the principles of fluid mechanics work to explain the physical impediments to thorough irrigation, and how the biological impediments, in the form of biofilm, prevent disinfection despite adequate irrigation. The recent introduction of new irrigation and agitation modalities, coupled with a new understanding of the old problem through novel research techniques, provides a vision to the future and will establish a new standard of irrigation in this field.

Negative pressure during irrigation contributes to improved safety as compared to high-positive pressure.

The power of ultrasonic vibrations has been harnessed in the field of dentistry—evolving in its use and purpose—for just over 60 years. The first section of this review describes the evolution and various applications of ultrasound in dentistry, and examines in detail the ultrasonic tools that have been developed for endodontic purposes. The second section of this review describes the use of ultrasonics during specific endodontic procedures, from access to obturation, incorporating as much as possible the most recent and relevant research available to date.