Stigma (letter) Stigma (letter) Stigma (ϛ) is a ligature of the Greek letters sigma (Σ) and tau (Τ), which was used in writing Greek between the Middle Ages and the 19th century. It is also used as a numeral symbol for the number 6. In this unrelated function, it is a continuation of the old letter digamma (originally Ϝ, cursive form ), which had served as a numeral since antiquity and was conflated with the σ-τ ligature in the minuscule handwriting of the Middle Ages. The στ ligature (, ) was one of many ligature forms that came into widespread use as
Dental torque wrench to the dental torque wrenches and the length of time in use presents stress on the material, fatigue can occur. The surgical motor is an electronic controlled torque-limiting device that also controls the speed. It is used with a twisted drill to make space in the bone for the implant or to fasten the screw (torque control can be with a torque-limiting attachment) with a screwdriver bit. In high precision areas such as aerospace applications motor or pneumatic torque wrenches are set at a lower torque value after which the final torque is set with a manual mechanical torque wrench,