BEUDAMED
    FDA Adverse Event Injury Summary report: N

    NSK

    MDR report key: 6675164 · Received June 28, 2017

    Report

    Report Number
    9611253-2017-00031
    Event Type
    Injury
    Date Received
    June 28, 2017
    Date of Event
    June 6, 2017
    Report Date
    July 18, 2017
    Manufacturer
    NAKANISHI INC.
    Product Code
    EGS
    PMA / PMN Number
    K972569
    Adverse Event
    Yes
    Report Source
    Manufacturer report
    Reporter Location
    JA
    Reporter Occupation
    OTHER

    Narratives

    Additional Manufacturer Narrative · 1

    THE DENTIST DID NOT PROVIDE THE PATIENT IDENTIFIER AND WEIGHT WHEN NAKANISHI VISITED THE DENTIST ON (B)(6) 2017. UPON RECEIVING THE DEVICE INVOLVED IN THE MDR EVENT FROM A DISTRIBUTOR, NAKANISHI CONDUCTED A FAILURE ANALYSIS OF THE RETURNED DEVICE THAT INCLUDED MEASURING THE TEMPERATURE OF THE OPERATING DEVICE [C170613-13-01]. 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 NUMBER (B)(4)]. THERE WERE NO PROBLEMS OBSERVED DURING THE MANUFACTURING OR TESTING NOTED IN THE DHR. THE REPAIR HISTORY SHOWED 1 SERVICE RECORD ((B)(6) 2016) SINCE THE DEVICE WAS SHIPPED. ACCORDING TO THE SERVICE RECORD, AFTER REPAIRING THE HANDPIECE (REPLACEMENT OF CARTRIDGE, DRIVE SHAFT AND DOG CLUTCH), NAKANISHI PERFORMED ALL OF THE NECESSARY OPERATION CHECKS AND CONFIRMED THAT ALL OF THE CRITERIA WERE MET. NAKANISHI CONDUCTED TEMPERATURE TESTING OF THE RETURNED DEVICE IN THE FOLLOWING MANNER: 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. NAKANISHI ATTACHED A THERMOCOUPLE (SENSOR TO MEASURE A 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 SITUATION. 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 POINT (1) AND (2) A FEW SECONDS AFTER THE START. TEMPERATURE MEASUREMENTS 10 SECONDS AFTER THE START ARE AS FOLLOWS: TEST POINT (1): 56.2 DEGREES C; TEST POINT (2): 75.3 DEGREES C; TEST POINT (3): 32.3 DEGREES C; TEST POINT (4): 24.4 DEGREES C. THE RISE IN TEMPERATURE WAS SO SUDDEN THAT THE TEST WAS CONCLUDED 10 SECONDS INTO THE PLANNED 5 MINUTE EVALUATION PERIOD. IDENTIFICATION OF THE SPECIFIC FAILURE MODE(S) AND/OR MECHANISM(S) AND THE ASSOCIATED DEVICE COMPONENTS INVOLVED: NAKANISHI DISASSEMBLED THE HANDPIECE AND PERFORMED A VISUAL INSPECTION OF THE INSIDE PARTS. NAKANISHI OBSERVED THE FOLLOWING PHENOMENA: THE BEARING RETAINER (BALL RETAINING PART) ON THE PUSH BUTTON SIDE WAS BROKEN. THERE WAS DIRT INSIDE THE CARTRIDGE/HEADCAP. NAKANISHI TOOK PHOTOGRAPHS OF ALL OF THE DISASSEMBLED PARTS AND KEPT THEM IN A FILE. CONCLUSIONS REACHED BASED ON THE INVESTIGATION AND ANALYSIS RESULTS: NAKANISHI IDENTIFIED THAT THE CAUSE OF THE OVERHEATING OF THE RETURNED DEVICE WAS ABNORMAL RESISTANCE DURING ROTATION CAUSED BY THE BROKEN BEARINGS DUE TO THE INGRESS OF DIRT INTO THE BEARING. A LACK OF MAINTENANCE CAUSES THE ACCUMULATION OF DIRT IN THE INSIDE PARTS, WHICH CAUSES DIRT INGRESS INTO THE BEARING DURING ROTATION, LEADING TO THE BROKEN BEARINGS. THIS CONTRIBUTES TO THE HANDPIECE OVERHEATING. IN ORDER TO PREVENT A RECURRENCE OF THE HANDPIECE OVERHEATING, NAKANISHI TOOK THE FOLLOWING ACTIONS: NAKANISHI REVIEWED THE OPERATION MANUAL AND RECONFIRMED CLARITY AND UNDERSTANDABILITY OF THE INSTRUCTIONS. NAKANISHI REPORTED THE ABOVE EVALUATION RESULTS TO THE DENTIST AND REMINDED THE DENTIST OF THE IMPORTANCE OF MAINTENANCE, AS INSTRUCTED IN THE OPERATION MANUAL.

    Additional Manufacturer Narrative · 1

    NO INFORMATION ABOUT PATIENT HAS BEEN PROVIDED BY THE DENTIST AT THIS MOMENT. NAKANISHI IS SCHEDULED TO VISIT THE DENTAL OFFICE TO OBTAIN THE INFORMATION.

    Description of Event or Problem · 1

    ON (B)(6) 2017 NAKANISHI VISITED THE DENTIST AND OBTAINED DETAILED INFORMATION ON THE EVENT. THE PROCEDURE THE DENTIST WAS PERFORMING AT THE TIME OF THE EVENT WAS REMOVING A CROWN FROM THE PATIENT'S TOOTH. THE PATIENT WAS NOT ANESTHETIZED. THE PATIENT COMPLAINED ABOUT THE HANDPIECE OVERHEATING. THE DENTIST WAS MADE AWARE OF A PINKY-SIZED BLISTER IN THE PATIENT'S MOUTH. THE PATIENT RECEIVED LASER IRRADIATION AS A TREATMENT FOR THE BURN. THE DENTIST DETERMINED THAT NO OTHER MEDICAL INTERVENTION WAS NECESSARY FOR THE INJURY. THERE WERE NO ABNORMALITIES OR MALFUNCTION OF THE DEVICE PRIOR TO USE.

    Description of Event or Problem · 1

    ON JUNE 13, 2017, NAKANISHI RECEIVED A PHONE CALL FROM A DISTRIBUTOR SAYING THAT AN NSK HANDPIECE HAD OVERHEATED AND BURNED A PATIENT. UPON RECEIPT OF THE INFORMATION, NAKANISHI STARTED AN INVESTIGATION AND FOUND THE SUBJECT DEVICE RETURNED FOR REPAIR AT NSK SERVICE CENTER. THERE WAS A NOTE WITH THE DEVICE STATING THAT: - THE EVENT OCCURRED ON (B)(6) 2017. - A DENTIST WAS PERFORMING A DENTAL PROCEDURE USING THE NSK HANDPIECE Z95L (SERIAL NO. (B)(4)). - DURING THE PROCEDURE, THE HANDPIECE OVERHEATED AND BURNED THE PATIENT.

    Devices

    Seq Brand Generic Product Code Manufacturer Model Lot UDI-DI
    455278 NSK HANDPIECE, CONTRA- AND RIGHT-ANGLE ATTACHMENT, DENTAL EGS NAKANISHI INC. Z95L

    Patients

    Seq Age Sex Outcome Treatment
    1 60 YR Other