BEUDAMED
    FDA Adverse Event Injury Summary report: N

    NSK

    MDR report key: 6876745 · Received September 19, 2017

    Report

    Report Number
    9611253-2017-00049
    Event Type
    Injury
    Date Received
    September 19, 2017
    Date of Event
    August 10, 2017
    Report Date
    October 12, 2017
    Manufacturer
    NAKANISHI INC.
    Product Code
    EGS
    PMA / PMN Number
    K972569
    Adverse Event
    Yes
    Product Problem
    Yes
    Report Source
    Manufacturer report
    Reporter Location
    WI, US
    Reporter Occupation
    DENTIST

    Narratives

    Additional Manufacturer Narrative · 0

    EXEMPTION NUMBER E2016004. NAKANISHI INC. (MANUFACTURER) IS SUBMITTING THE REPORT ON BEHALF OF (B)(4). (B)(4) IS LISTED HERE AND MR. (B)(6) BECAUSE MR. (B)(6) IS THE OFFICIAL CORRESPONDENT OF BOTH NAKANISHI INC. AND (B)(4).

    Description of Event or Problem · 0

    ON (B)(6) 2017, NAKANISHI RECEIVED AN E-MAIL FROM A DISTRIBUTOR (B)(4) ABOUT A HANDPIECE OVERHEATING. DETAILS ARE AS FOLLOWS. ON (B)(6) 2017, (B)(4) WAS MADE AWARE OF THE EVENT BY INCOMING SERVICE REPAIR PAPERWORK. THE EVENT OCCURRED ON (B)(6) 2017. A DENTIST WAS PERFORMING AN OD RESTORATION OF A PATIENT'S TOOTH #18 USING Z95L (SERIAL NO.: (B)(4)). THE PATIENT WAS UNDER ANESTHESIA. DURING THE PROCEDURE, THE DENTIST FOUND A DIME-SIZED BURN ON THE LEFT SIDE OF THE CHEEK. THE DEGREE OF THE BURN IN UNKNOWN. NO BURN TREATMENT WAS PROVIDED TO THE PATIENT, AND NO FOLLOW-UP IS SCHEDULED FOR THE PATIENT. ACCORDING TO THE DENTIST, THERE WERE NO ABNORMALITIES OR MALFUNCTIONS OBSERVED PRIOR TO THE EVENT WITH THE DEVICE.

    Additional Manufacturer Narrative · 1

    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 OPERATING TEMPERATURE OF THE DEVICE [C170830-10]. THESE ACTIVITIES ARE DESCRIBED IN MORE DETAIL BELOW. METHODOLOGY USED: 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. THERE WERE NO RECORDS INDICATING NAKANISHI (THE MANUFACTURER) REPAIRED THE DEVICE SINCE THE DEVICE WAS SHIPPED. NAKANISHI RECEIVED THE REPAIR RECORDS FROM NSK AMERICA (NAM), WHICH INCLUDED THE DETAILED INFORMATION ABOUT THE REPAIR NAM CARRIED OUT, ALONG WITH THE REPAIR TEST RESULTS THAT INDICATE THE REPAIRED DEVICE PASSED EVERY TEST ITEM. NAKANISHI KEPT THE TEST RESULTS IN A FILE. 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 RESPONSE. 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 22 SECONDS AFTER THE START ARE AS FOLLOWS: TEST POINT (1): 65.6 DEGREES C, TEST POINT (2): 63.5 DEGREES C, TEST POINT (3): 40.3 DEGREES C, TEST POINT (4): 28.3 DEGREES C. THE RISE IN TEMPERATURE WAS SO SUDDEN THAT THE TEST WAS CONCLUDED 22 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 CARTRIDGE FRONT SIDE WAS BROKEN. THE CARTRIDGE REAR BEARING WAS ABRADED. THERE WAS DEBRIS IN THE HEADCAP. NAKANISHI TOOK PHOTOGRAPHS OF ALL OF THE DISASSEMBLED PARTS AND KEPT THEM IN A FILE. NAKANISHI THEN REPLACED THE BROKEN CARTRIDGE (INCLUDING THE BEARING) WITH A NEW CARTRIDGE AND MEASURED THE EXOTHERMIC SITUATION YET AGAIN. THERE WAS NO ABNORMAL RISE IN TEMPERATURE DURING THE 300-SECOND-TEST PERIOD (SEE BELOW). NAKANISHI CONFIRMED THAT THE RETURNED HANDPIECE WAS OPERATING AS EXPECTED AND WITHIN TEMPERATURE SPECIFICATIONS ONCE THE DAMAGED CARTRIDGE HAD BEEN REPLACED. TEST POINT (1): 39.4 DEGREES C, TEST POINT (2): 41.4 DEGREES C, TEST POINT (3): 38.4 DEGREES C, TEST POINT (4): 38.2 DEGREES C. 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 UNDESIRABLE MATERIALS INTO THE BEARING. A LACK OF MAINTENANCE CAUSES THE ACCUMULATION OF DEBRIS ON THE INSIDE PARTS, WHICH CAUSES DEBRIS INGRESS INTO THE BEARING DURING ROTATION. 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 NSK AMERICA AND DIRECTED NSK AMERICA TO REMIND THE USER OF THE IMPORTANCE OF MAINTENANCE, AS INSTRUCTED IN THE OPERATION MANUAL.

    Devices

    Seq Brand Generic Product Code Manufacturer Model Lot UDI-DI
    655227 NSK HANDPIECE, CONTRA- AND RIGHT-ANGLE ATTACHMENT, DENTAL EGS NAKANISHI INC. Z95L

    Patients

    Seq Age Sex Outcome Treatment
    1 25 YR Other