Defects in ProTaper S1 instruments after clinical use: longitudinal examination.

Area of Science:

• Endodontics
• Dental Materials Science

Background:

• ProTaper shaping instruments are widely used in endodontic procedures.
• Understanding instrument failure modes is crucial for patient safety and treatment success.

Purpose of the Study:

• To evaluate defects and failure modes of ProTaper S1 instruments after defined clinical use.
• To identify potential risks associated with repeated instrument usage.

Main Methods:

• 122 ProTaper S1 instruments were collected after clinical use from an endodontic clinic.
• Instruments were cleaned, autoclaved, and examined for separation and defects using scanning electron microscopy.
• Fractured and intact instruments were analyzed for microcracks, wear, and other surface alterations.

Main Results:

• 27 out of 121 instruments separated, primarily due to flexural fatigue.
• Microcracks, surface debris, pitting, and cutting edge wear were observed in both fractured and intact instruments.
• Most failures occurred without visible unwinding of the flutes, and only one instrument showed unwinding defects.

Conclusions:

• Multiple uses of ProTaper S1 instruments contribute to microcrack formation and cutting edge wear.
• Instrument failure is predominantly due to flexural fatigue rather than torsional fracture or unwinding.
• Further investigation into fracture mechanisms and the role of debris is warranted.