BEUDAMED
    FDA Adverse Event Injury Summary report: N

    NSK

    MDR report key: 18919195 · Received March 17, 2024

    Report

    Report Number
    9611253-2024-00011
    Event Type
    Injury
    Date Received
    March 17, 2024
    Date of Event
    September 7, 2023
    Report Date
    April 18, 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
    DENTIST
    Health Professional
    Yes

    Narratives

    Additional Manufacturer Narrative · 0

    NAKANISHI IS STILL TRYING TO OBTAIN INFORMATION ABOUT THE EVENT, INCLUDING INFORMATION ABOUT THE PATIENT.

    Additional Manufacturer Narrative · 0

    THE DENTIST REFUSED TO PROVIDE INFORMATION ABOUT THE PATIENT'S GENDER AND WEIGHT. 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. C240221-02]. 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 [BBE90332]. THERE WERE NO PROBLEMS OBSERVED DURING MANUFACTURING OR TESTING NOTED IN THE DHR. THE REPAIR HISTORY SHOWED 1 SERVICE RECORD SINCE THE DEVICE WAS SHIPPED. THE REPAIR DETAILS ARE AS FOLLOWS: - JANUARY 2020: THE CARTRIDGE, DRIVE SHAFT, DOG CLUTCH, AND HEADCAP WERE REPLACED. WITH RESPECT TO THE REPAIR IN THE ABOVE LIST, THE SERVICE RECORD INDICATES 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 RISES IN TEMPERATURE AT THE TEST POINTS AS SHOWN BELOW; HOWEVER, THE TEMPERATURES WERE NOT HIGH ENOUGH TO CAUSE A BURN INJURY. THE MAXIMUM TEMPERATURE MEASURED 5 MINUTES INTO THE TEST WERE AS FOLLOWS: - TEST POINT (1): 38.1 DEGREES C - TEST POINT (2): 41.0 DEGREES C - TEST POINT (3): 31.6 DEGREES C - TEST POINT (4): 33.4 DEGREES C C) NAKANISHI CLEANED THE INSIDE OF THE HANDPIECE USING NAKANISHI PANA SPRAY PLUS. NAKANISHI THEN CONDUCTED TEMPERATURE TESTING OF THE DEVICE IN THE SAME MANNER AS ABOVE YET AGAIN. THERE WAS NO ABNORMAL RISE IN TEMPERATURE DURING THE 5-MINUTE TEST PERIOD. TEMPERATURE MEASUREMENTS 5 MINUTES INTO THE TEST WERE AS FOLLOWS: - TEST POINT (1): 33.7 DEGREES C - TEST POINT (2): 36.9 DEGREES C - TEST POINT (3): 30.4 DEGREES C - TEST POINT (4): 30.4 DEGREES C 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 THAT THE INTERNAL PARTS WERE SOILED BUT WERE NOT BROKEN. B) NAKANISHI TOOK PHOTOGRAPHS OF ALL THE DISASSEMBLED PARTS AND KEPT THEM IN THE INVESTIGATION REPORT NO. C240221-02. CONCLUSIONS REACHED BASED ON THE INVESTIGATION AND ANALYSIS RESULTS: A) NAKANISHI WAS NOT ABLE TO REPLICATE THE TEMPERATURE RISE AT THE TIME OF THE EVENT, BUT BASED ON THE FINDINGS IN THE VISUAL INSPECTION, AS WELL AS MANY YEARS OF EXPERIENCE, NAKANISHI CONSIDERS THE POSSIBILITY THAT THE CAUSE OF THE HANDPIECE OVERHEATING WAS ABNORMAL RESISTANCE DURING ROTATION DUE TO DEBRIS FROM THE SOILED AND ABRADED INTERNAL PARTS OR RESIDUAL LIQUID (EXCESSIVE WATER OR LUBRICATING OIL), WHICH INTERFERED WITH ROTATION. B) A LACK OF MAINTENANCE CAUSED THE ACCUMULATION OF DEBRIS AND THE RESIDUAL LIQUID ON THE INTERNAL PARTS, WHICH CAUSED DEBRIS OR LIQUID INGRESS INTO THE BEARING DURING ROTATION. THIS CONTRIBUTED TO THE HANDPIECE OVERHEATING. C) IN ORDER TO PREVENT A RECURRENCE OF THE HANDPIECE OVERHEATING, NAKANISHI TOOK THE FOLLOWING ACTIONS: C.1) NAKANISHI REVIEWED THE OPERATION MANUAL AND RECONFIRMED THE CLARITY AND UNDERSTANDABILITY OF THE INSTRUCTIONS. C.2) NAKANISHI REPORTED THE ABOVE EVALUATION RESULTS TO THE DENTIST AND REMINDED THE DENTIST OF THE IMPORTANCE OF MAINTENANCE AS INSTRUCTED IN THE OPERATION MANUAL AND CHECKING OF THE HANDPIECE PRIOR TO USE TO PREVENT OVERHEATING, AS INSTRUCTED IN THE OPERATION MANUAL.

    Description of Event or Problem · 0

    ON (B)(6) 2024, A DENTIST VISITED THE CENTRAL JAPAN DENTAL SHOW AND THERE COMPLAINED ABOUT AN NSK HANDPIECE OVERHEATING. THE DETAILS NAKANISHI OBTAINED ARE AS FOLLOWS: THE EXACT DATE WHEN THE EVENT OCCURRED IS UNKNOWN. THE DATE ENTERED IN B3 INDICATES THE BEST ESTIMATE. THE DENTIST WAS PERFORMING A DENTAL PROCEDURE ON A PATIENT USING THE Z95L HANDPIECE (SERIAL NO. UNKNOWN). DURING THE PROCEDURE, THE HANDPIECE OVERHEATED, AND THE PATIENT RECEIVED A WHITISH BURN INJURY TO THEIR LEFT BUCCAL MUCOSA. THE PATIENT COMPLAINED OF FEELING PAIN AFTER THEY LEFT THE DENTAL OFFICE.

    Description of Event or Problem · 0

    ON MARCH 25, 2024, TWO NSK Z95L HANDPIECES WERE RETURNED FROM A DISTRIBUTOR TO NAKANISHI FOR REPAIR. NAKANISHI MADE A PHONE CALL TO THE DENTIST AND OBTAINED ADDITIONAL INFORMATION ON THE ADVERSE EVENT INCLUDING INFORMATION ABOUT THE PATIENT. ACCORDING TO THE DENTIST, THERE ARE TWO DEVICES SUSPECTED TO BE INVOLVED IN THE EVENT, BUT THE DENTIST COULD NOT IDENTIFY WHICH ONE OF THE DEVICES ACTUALLY CAUSED THE EVENT. THEREFORE, NAKANISHI IS SUBMITTING TWO SEPARATE MDRS FOR THIS EVENT. THIS FOLLOW-UP REPORT IS REGARDING THE HANDPIECE WITH THE SERIAL NUMBER BBE90332. - THE EVENT OCCURRED ON (B)(6) 2023. - AT THE TIME OF THE EVENT, THE DENTIST WAS PERFORMING #6 AND #7 CROWN REMOVAL PROCEDURE ON THE PATIENT USING Z95L HANDPIECE (SERIAL NO. (B)(6). - THE PATIENT WAS UNDER LOCAL ANESTHESIA, AND THEN THE PATIENT AND THE DENTIST DID NOT FIND THAT THE HANDPIECE OVERHEATED. - THE PATIENT HAS HAD A FOLLOW-UP VISIT WITH THE DENTIST ON THE NEXT DAY AND THE DENTIST FOUND THAT THE PATIENT RECEIVED A CIRCULAR BURN INJURY ABOUT 1CM IN DIAMETER. - THE PATIENT IS REPORTED TO HAVE RECEIVED LASER TREATMENT FOR THE INJURY AND TO HAVE BEEN HEALED. - ACCORDING TO THE DENTIST, PATIENTS HAVE OCCASIONALLY COMPLAINED OF FEELING HOT DURING THE PROCEDURES.

    Devices

    Seq Brand Generic Product Code Manufacturer Model Lot UDI-DI
    169665 NSK HANDPIECE, CONTRA- AND RIGHT-ANGLE ATTACHMENT, DENTAL EGS NAKANISHI INC. Z95L

    Patients

    Seq Age Sex Outcome Treatment
    1 62 YR Female Other