BEUDAMED
    FDA Adverse Event Injury Summary report: N

    NSK

    MDR report key: 9471087 · Received December 15, 2019

    Report

    Report Number
    9611253-2019-00058
    Event Type
    Injury
    Date Received
    December 15, 2019
    Date of Event
    November 26, 2019
    Report Date
    December 18, 2019
    Manufacturer
    NAKANISHI INC.
    Product Code
    EGS
    PMA / PMN Number
    K972569
    Adverse Event
    Yes
    Product Problem
    Yes
    Report Source
    Manufacturer report
    Reporter Location
    JA
    Reporter Occupation
    003

    Narratives

    Additional Manufacturer Narrative · 0

    UPON RECEIVING THE DEVICE INVOLVED IN THE MDR EVENT, NAKANISHI CONDUCTED A FAILURE ANALYSIS OF THE RETURNED DEVICE THAT INCLUDED MEASURING THE OPERATING TEMPERATURE OF THE DEVICE [C191127-01]. THESE ACTIVITIES ARE DESCRIBED IN MORE DETAIL BELOW. METHODOLOGY USED: A) NAKANISHI EXAMINED THE DEVICE HISTORY RECORD AND THE REPAIR HISTORY FOR THE SUBJECT Z95L DEVICE [SERIAL NO. (B)(6) ]. THERE WERE NO PROBLEMS OBSERVED DURING THE MANUFACTURING OR TESTING NOTED IN THE DHR. THE REPAIR HISTORY SHOWED 2 SERVICE RECORDS (FEBRUARY 2018 AND MARCH 2019) SINCE THE DEVICE WAS SHIPPED. ACCORDING TO THE SERVICE RECORDS, AFTER REPAIRING THE HANDPIECE (REPLACEMENT OF CARTRIDGE, DRIVE SHAFT, DOG CLUTCH, AND HEADCAP FOR BOTH OF THE REPAIRS), NAKANISHI PERFORMED ALL OF THE NECESSARY OPERATION CHECKS, AND CONFIRMED THAT ALL OF THE CRITERIA WERE MET. B) NAKANISHI CONDUCTED TEMPERATURE TESTING OF THE RETURNED DEVICE IN THE FOLLOWING MANNER: B.1) TEMPERATURE SENSORS WERE ATTACHED TO THE EXTERIOR OF THE DEVICE AT VARIOUS TEST POINTS. THIS INCLUDED THE POINT MOST PROXIMAL TO THE PATIENT (TESTING POINT (1)) AND POINTS FURTHER TOWARD THE DISTAL END OF THE DEVICE (TESTING POINTS (2) THROUGH (4)). THE TEST SETUP WAS PREPARED TO TAKE TEMPERATURE MEASUREMENTS AT ALL POINTS SIMULTANEOUSLY, INCLUDING A REFERENCE MEASUREMENT AT AMBIENT ROOM TEMPERATURE. B.2) NAKANISHI ATTACHED A THERMOCOUPLE (SENSOR TO MEASURE TEMPERATURE) TO EACH OF THE TESTING POINTS. NAKANISHI ROTATED THE DEVICE'S MOTOR AT 40,000 MIN-1, WHICH IS THE MAXIMUM RPM FOR THE MOTOR THAT DRIVES THE HANDPIECE (200,000 MIN-1 FOR THE HANDPIECE), WITH WATER SPRAY, AND MEASURED THE EXOTHERMIC RESPONSE. B.3) NAKANISHI MEASURED THE TEMPERATURE RISE OF THE RETURNED HANDPIECE SET AT 200,000 MIN-1 (MOTOR REVOLUTION 40,000 MIN-1). NAKANISHI OBSERVED AN ABNORMAL TEMPERATURE RISE AT TEST POINTS (1) AND (2) A FEW SECONDS AFTER THE START. TEMPERATURE MEASUREMENTS 35 SECONDS AFTER THE START ARE AS FOLLOWS: TEST POINT (1): 70.5 DEGREES C. TEST POINT (2): 120.9 DEGREES C. TEST POINT (3): 28.0 DEGREES C. TEST POINT (4): 28.1 DEGREES C. THE RISE IN TEMPERATURE WAS SO SUDDEN THAT THE TEST WAS CONCLUDED 35 SECONDS INTO THE PLANNED 5-MINUTE EVALUATION PERIOD. IDENTIFICATION OF THE SPECIFIC FAILURE MODE(S) AND/OR MECHANISM(S) OF THE ASSOCIATED DEVICE COMPONENTS WAS CONDUCTED AS FOLLOWS: A) NAKANISHI DISASSEMBLED THE HANDPIECE AND PERFORMED A VISUAL INSPECTION OF THE INTERNAL PARTS. NAKANISHI OBSERVED THE FOLLOWING PHENOMENA: THE HEADCAP WAS DEFORMED AND REMAINED PRESSED IN THE HANDPIECE. THERE WAS EVIDENCE OF CONTACT WITH THE PUSH BUTTON AND THE OPENING/CLOSING PART ON THE REAR SIDE OF THE CARTRIDGE B) NAKANISHI TOOK PHOTOGRAPHS OF ALL OF THE DISASSEMBLED PARTS AND KEPT THEM IN INVESTIGATION REPORT #C191127-01. CONCLUSIONS REACHED BASED ON THE INVESTIGATION AND ANALYSIS RESULTS: A) NAKANISHI IDENTIFIED THAT THE CAUSE OF THE OVERHEATING OF THE RETURNED DEVICE WAS FRICTION HEAT GENERATED BY CONTACT WITH THE PUSH BUTTON AND THE OPENING/CLOSING PART ON THE REAR SIDE OF THE CARTRIDGE. THIS CONTACT WAS CAUSED BY THE HEADCAP BEING DEPRESSED DUE TO DEFORMATION DURING ROTATION (SLIDING FAILURE). B) NAKANISHI CONSIDERS THE POSSIBILITY FROM MANY YEARS OF EXPERIENCE THAT MISUSE OR MISHANDLING DURING MAINTENANCE APPLIED PRESSURE ON INTERNAL PARTS, LEADING TO DEFORMATION OF THE HEADCAP, WHICH THEN DEPRESSED THE HEADCAP TO REMAIN IN THE HANDPIECE DURING ROTATION. C) ALSO, FAILURE TO CHECK THE HANDPIECE BEFORE USE LED TO USER IGNORANCE OF ABNORMALITIES IN THE INTERNAL PARTS, WHICH CONTRIBUTED TO THE HANDPIECE OVERHEATING. D) IN ORDER TO PREVENT A RECURRENCE OF THE HANDPIECE OVERHEATING, NAKANISHI TOOK THE FOLLOWING ACTIONS: D.1) NAKANISHI REVIEWED THE OPERATION MANUAL AND RECONFIRMED THE CLARITY AND UNDERSTANDABILITY OF THE INSTRUCTIONS. D.2) NAKANISHI REPORTED THE ABOVE EVALUATION RESULTS TO THE DENTIST, AND REMINDED THE DENTIST OF THE IMPORTANCE OF USING AND CHECKING THE HANDPIECE PRIOR TO USE TO PREVENT OVERHEATING AS INSTRUCTED IN THE OPERATION MANUAL.

    Additional Manufacturer Narrative · 1

    THE DENTIST REFUSED TO PROVIDE THE PATIENT'S WEIGHT.

    Description of Event or Problem · 1

    ON NOVEMBER 27, 2019, NAKANISHI RECEIVED A PHONE CALL FROM A DEALER ABOUT AN NSK HANDPIECE OVERHEATING. UPON RECEIPT OF THE INFORMATION, NAKANISHI CONTACTED THE DENTAL OFFICE FOR FURTHER INFORMATION ABOUT THE EVENT. THE DETAILS NAKANISHI OBTAINED FROM THE COMMUNICATION WITH THE DENTIST ARE AS FOLLOWS: THE EVENT OCCURRED ON (B)(6) 2019. THE DENTIST WAS FORMING A RESIN COMPOSITE IN A CORE BUILD-UP PROCEDURE USING THE Z95L HANDPIECE (SERIAL NO.: (B)(4)). THE PATIENT WAS NOT UNDER ANESTHESIA. DURING THE PROCEDURE, THE PATIENT COMPLAINED ABOUT THE HEAT FROM THE HANDPIECE, AND THE DENTIST FOUND A BURN INJURY APPROXIMATELY 1-CENTIMETER IN DIAMETER ON THE PATIENT'S PALATE. THE DENTIST GAVE THE PATIENT AN OINTMENT FOR THE BURN.

    Devices

    Seq Brand Generic Product Code Manufacturer Model Lot UDI-DI
    1265715 NSK HANDPIECE, CONTRA- AND RIGHT-ANGLE ATTACHMENT, DENTAL EGS NAKANISHI INC. Z95L

    Patients

    Seq Age Sex Outcome Treatment
    1 37 YR Other