BEUDAMED
    FDA Adverse Event Injury Summary report: N

    NSK

    MDR report key: 20530676 · Received October 25, 2024

    Report

    Report Number
    9611253-2024-00052
    Event Type
    Injury
    Date Received
    October 25, 2024
    Date of Event
    September 17, 2024
    Report Date
    November 25, 2024
    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

    THE DENTIST REFUSED TO PROVIDE INFORMATION ABOUT THE PATIENT'S WEIGHT AND GENDER.

    Additional Manufacturer Narrative · 0

    UPON RECEIVING THE DEVICE INVOLVED IN THE MDR EVENT, NAKANISHI CONDUCTED A FAILURE ANALYSIS OF THE RETURNED DEVICE, WHICH INCLUDED MEASURING THE OPERATING TEMPERATURE OF THE DEVICE [REPORT NO. C241003-07]. 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 MANUFACTURING OR TESTING NOTED IN THE DHR. THE REPAIR HISTORY SHOWED 3 SERVICE RECORDS SINCE THE DEVICE WAS SHIPPED. THE REPAIR DETAILS ARE AS FOLLOWS: - (B)(6) 2019: THE CARTRIDGE AND HEAD CAP WERE REPLACED. - (B)(6) 2019: REPEAT REPAIR. THE HANDPIECE WAS ADJUSTED. - (B)(6) 2024: THE CARTRIDGE, DOG CLUTCH, AND DRIVE SHAFT WERE REPLACED. WITH RESPECT TO THE REPAIRS ABOVE, THE SERVICE RECORDS INDICATE THAT 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 40,000MIN-1, WHICH IS THE MAXIMUM RPM FOR THE MOTOR THAT DRIVES THE HANDPIECE (200,000MIN-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 200,000MIN-1 (MOTOR REVOLUTION 40,000MIN-1). NAKANISHI OBSERVED AN ABNORMAL TEMPERATURE RISE AT TEST POINTS (1) AND (2) 10 SECONDS INTO THE TEST. TEMPERATURE MEASUREMENTS ABOUT 10 SECONDS AFTER THE START OF THE TEST WERE AS FOLLOWS: - TEST POINT (1): 65.8 DEGREES C. - TEST POINT (2): 95.7 DEGREES C. - TEST POINT (3): 25.9 DEGREES C. - TEST POINT (4): 24.0 DEGREES C. THE INCREASE IN TEMPERATURE WAS SO SUDDEN THAT THE TEST WAS CONCLUDED ABOUT 10 SECONDS INTO THE PLANNED 5-MIMUTE 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: - THE BEARING RETAINER IN THE BALL BEARING ON THE REAR SIDE OF THE CARTRIDGE WAS BROKEN. - THE DRIVE SHAFT AND INSIDE OF THE HEAD CAP WERE SOILED AND DISCOLORED. B) NAKANISHI TOOK PHOTOGRAPHS OF ALL THE DISASSEMBLED PARTS AND KEPT THEM IN THE INVESTIGATION REPORT NO. (B)(4). CONCLUSIONS REACHED BASED ON THE INVESTIGATION AND ANALYSIS RESULTS: A) NAKANISHI DETERMINED THAT THE CAUSE OF THE HANDPIECE OVERHEATING WAS FRICTIONAL RESISTANCE GENERATED BY CONTACT BETWEEN THE BALL BEARING RETAINER AND THE OUTER AND INNER RACES, AND BEARING BALLS, WHICH WAS CAUSED BY THE BROKEN BALL BEARINGS. B) NAKANISHI ALSO CONSIDERS THE POSSIBILITY FROM MANY YEARS OF EXPERIENCE, THAT THE CAUSE OF THE BROKEN BEARING RETAINERS WAS THE INGRESS OF UNDESIRABLE MATERIALS INTO THE BEARING, WHICH INTERFERED WITH ROTATION. C) A LACK OF MAINTENANCE CAUSED THE ACCUMULATION OF DEBRIS ON 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 MAINTENANCE AND CHECKING OF THE HANDPIECE PRIOR TO USE TO PREVENT OVERHEATING, AS INSTRUCTED IN THE OPERATION MANUAL.

    Description of Event or Problem · 0

    ON SEPTEMBER 30, 2024, NAKANISHI RECEIVED A PHONE CALL FROM A DISTRIBUTOR ABOUT AN NSK HANDPIECE OVERHEATING. UPON RECEIPT OF THE INFORMATION, NAKANISHI MADE A PHONE CALL TO THE DENTAL CLINIC FOR FURTHER INFORMATION ABOUT THE EVENT INCLUDING INFORMATION ABOUT THE PATIENT. THE DETAILS NAKANISHI OBTAINED ARE AS FOLLOWS. - THE EVENT OCCURRED ON (B)(6) 2024. - THE DENTIST WAS REMOVING AN INLAY AND A CARIES FROM #6 TOOTH OF A PATIENT'S UPPER LEFT JAW USING THE Z95L HANDPIECE (SERIAL NO. (B)(6). THE PATIENT WAS UNDER INFILTRATION ANESTHESIA. - DURING THE PROCEDURE, THE PATIENT COMPLAINED OF FEELING PAIN, AND THEN THE DENTIST OBSERVED A WHITISH BURN INJURY OF ABOUT 10 MM IN DIAMETER TO THE PATIENT'S BUCCAL MUCOSA. - THE PATIENT HAS HAD FOLLOW-UP VISIT WITH THE DENTIST AND IS REPORTED TO BE HEALING NORMALLY.

    Devices

    Seq Brand Generic Product Code Manufacturer Model Lot UDI-DI
    1092909 NSK HANDPIECE, CONTRA- AND RIGHT-ANGLE ATTACHMENT, DENTAL EGS NAKANISHI INC. Z95L

    Patients

    Seq Age Sex Outcome Treatment
    1 49 YR Female Other