Scientific Concepts: Infection Control, Anatomy, Chemistry, and Electricity
Infection control
Bacteria are grouped by shape - cocci (round), bacilli (rod), spirilla (spiral) - and by whether they cause disease. Spores (tetanus, anthrax) survive ordinary disinfection; only sterilization destroys them. Learn the three levels precisely: sanitation is mechanical cleaning that reduces microorganisms; disinfection uses an EPA-registered hospital-grade product to destroy most, but not all; sterilization destroys all microbial life. Contact time printed on the label is mandatory - wiping a tool dry before the full contact time cancels the process. Porous items (files, buffers, wooden sticks, cotton) cannot be disinfected; use once and discard. Standard Precautions treat every client's blood and body fluids as infectious.
Anatomy and physiology
Skull bones: occipital, two parietal, frontal, two temporal, ethmoid, sphenoid. Separate muscles of mastication (masseter, temporalis) from muscles of expression (frontalis, orbicularis oculi, zygomaticus). Scalp nerves: trifacial (5th) and facial (7th). Main arteries: common carotid, then temporal, occipital, facial, and superficial temporal branches.
Chemistry and electricity
pH is logarithmic: each whole unit is a tenfold change. In electricity, amp is current, volt is pressure, ohm is resistance, watt is power. Galvanic current is constant direct current - the negative electrode (cathode) drives alkaline anaphoresis and desincrustation; the positive (anode) is acidic cataphoresis. High frequency is alternating current used in thermolysis.
Worked example
A pH 3 product versus a pH 6 product: three units of difference means 10³, or 1,000 times more acidic. Traps include calling the lower number "weaker," assuming a disinfectant kills spores, and swapping muscle names under time pressure.