Primary stability evaluation of mono and dual-thread miniscrews in different insertion angles

The aim of this in-vitro study is, to evaluate the primary stability of tapered mono and dual-thread miniscrews inserted with different angles.In this study 60 self-drilling miniscrews with a diameter of 1,6 mm and a length of 8,0 mm were used. Of these 60 miniscrews, 30 were mono-thread and the remaining 30 were dual-thread miniscrews. These miniscrews were applied to bone blocks prepared from ilium of bovine. There are four groups of miniscrews according to thread designs and insertion angles. The first group consists of 15 mono-thread miniscrews which were inserted with an angle of 90° to the bone surface, the second group consists of 15 mono-thread miniscrews which were inserted with an angle of 60° to the bone surface, the third group consists of 15 dual-thread miniscrews which were inserted with an angle of 90° to the bone surface and finally the fourth group consists of 15 dual-thread miniscrews were inserted with an angle of 60° to the bone surface. All implant stability quotient (ISQ) values of miniscrews were measured with resonance frequency analysis (RFA) and statistically evaluated.When groups were compared, it has been revealed that there is no statistically significant difference between 90° and 60° insertion angles of mono-thread miniscrews (p<0.01). Furthermore, it was also revealed that the ISQ values of dual-thread miniscrews inserted with an angle of 90° were statistically significantly higher when compared to those of mono-thread miniscrews inserted with an angle of 90° and mono and dual-thread miniscrews inserted with an angle of 60° (p<0.01). Finally, results also indicated that dual-thread miniscrews inserted with an angle of 60° has the same stability values with those of mono-thread miniscrews inserted with different angles.In conclusion, as the number of threads of perpendicularly inserted dual-thread miniscrews attached to the cortical bone increases, the stability also increases compared to perpendicularly inserted mono-thread miniscrews. Besides, the change in insertion angle of dual-thread miniscrews from 90° to 60° causes a reduction in primary stability values.