We show here that increasing thread length and reducing pitch can increase primary implant stability without changing the size of an implant. Compared with the standard single-threaded implant with a 1.2-mm pitch/lead (12S), torque values and ISQ were significantly increased by doubling the thread length by adding the second thread (06D) or by reducing pitch/lead and lead angle of a single-threaded implant (06S). The torque and ISQ values of 06S were greater compared with those of 06D. Thus, when primary stability must be increased without changing the size of the implant, increasing the thread length and reducing the pitch/lead and lead angle to that of a single-threaded implant is considered more effective versus using a double-threaded implant. Secondary stability occurs in delayed loading and is little affected by thread design. However, multiple threads are chosen when immediate loading is clinically required. Therefore, a single-threaded implant is considered more effective than a double-threaded implant. When immediate loading is required, the failure of the implant may be avoided with the use of single threads. The displacement and micromotion associated with a single-threaded implant is comparable to that of a double-threaded implant with the same pitch and a 2-fold greater lead and lead angle. The torque and ISQ values presented here support the conclusion that 06S outperformed 06D.

Microscopic observations revealed that 06S achieved increased primary stability compared with 06D and explain why the doubled-threaded length of 06D or 06S did not have double the torque value of that of 12S. The three non-self-tapping implants were associated with bone damage, which was more severe using 06D compared with 06S and 12S. We attribute this increased severity of damage using 06D to its shorter pitch compared with that of 12S and larger lead angle compared with those of 12S and 06S.