Bending 30-gauge needles using a needle guide: fatigue life evaluation.

Area of Science:

• Dental materials science
• Biomedical engineering
• Medical device safety

Background:

• Dentists often bend needles for injections, raising concerns about fracture, lumen occlusion, and sharps handling.
• Previous research indicated 30-gauge needles fracture after 4-9 bends without a guide.

Purpose of the Study:

• To evaluate the fatigue life of 30-gauge dental needles when bent using a needle guide.
• To determine the number of 90° bends a needle can sustain before fracture.

Main Methods:

• 48 30-gauge needles were tested by two operators using a needle guide.
• Needles were bent to 90°, tested for anesthetic flow, then returned to 0° until failure.
• Failure was defined as anesthetic not passing through the needle tip due to fracture or occlusion.

Main Results:

• Needles sustained an average of 40.33 bends (minimum 20, median 40, maximum 54) before fracture.
• The needle lumen remained patent until fracture occurred in all trials.
• Operator differences were statistically significant (P < 0.001), but lot differences were not (P = 0.504).

Conclusions:

• Needle guides significantly increase the number of bends before needle fracture compared to previous studies (P < 0.000001).
• Further research should explore needle guides with other needle types and various operators.
• Investigating workplace safety and clinical applications of bent needles for anesthetic delivery is warranted.