Manufacturing Order Matters? Exploring the Impact of Heat Treatment and Machining Sequences on the NiTi Instruments...

Area of Science:

• Materials Science
• Biomaterials Engineering
• Dental Materials

Background:

• Nickel-titanium (NiTi) instruments are crucial in endodontics.
• Manufacturing processes, including heat treatment timing, can influence NiTi alloy properties.
• Understanding these effects is vital for optimizing instrument design and clinical performance.

Purpose of the Study:

• To compare the metallurgical and mechanical properties of two NiTi endodontic instruments manufactured with different heat treatment sequences.
• To evaluate the impact of pre-machining versus post-machining heat treatment on instrument performance.

Main Methods:

• Two groups of Procodile NiTi instruments (Procodile Q: heat-treated before machining; Procodile +HT: heat-treated after machining) were analyzed (n=74 each).
• Evaluated parameters included design, NiTi composition, phase transformation temperatures, cyclic fatigue, torsional fatigue, bending load, buckling strength, cutting ability, microhardness, and surface roughness.
• Statistical analysis employed the Student's t-test and Mann-Whitney test (α=0.05).

Main Results:

• Both instrument groups exhibited similar designs and NiTi compositions.
• Procodile Q showed a slightly higher austenitic start temperature and significantly superior cyclic fatigue resistance at both 20°C and 35°C (p<0.001).
• Procodile Q also demonstrated higher surface roughness (p=0.041), while other mechanical properties showed no significant differences (p>0.05).

Conclusions:

• The sequence of machining and heat treatment has a minimal impact on the overall mechanical performance of Procodile NiTi instruments.
• The manufacturing order primarily influences cyclic fatigue resistance and surface roughness.
• These findings suggest that minor adjustments in manufacturing can optimize specific instrument characteristics without compromising general efficacy.