BEUDAMED
    FDA Adverse Event Injury Summary report: N

    NSK

    MDR report key: 14796028 · Received June 24, 2022

    Report

    Report Number
    9611253-2022-00041
    Event Type
    Injury
    Date Received
    June 24, 2022
    Date of Event
    May 18, 2022
    Report Date
    June 24, 2022
    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

    THE DENTIST REFUSED TO PROVIDE ANY INFORMATION ABOUT THE PATIENT OTHER THAN THE ETHNICITY AND RACE. UPON RECEIVING THE DEVICE INVOLVED IN THE MDR EVENT, NAKANISHI CONDUCTED A FAILURE ANALYSIS OF THE RETURNED DEVICE [REPORT NO. C220607-05]. 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 [D2090386]. THERE WERE NO PROBLEMS OBSERVED DURING MANUFACTURING OR TESTING NOTED IN THE DHR. THERE WERE ALSO NO REPAIR HISTORY RECORDS SINCE THE DEVICE WAS SHIPPED. 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) A FEW SECONDS INTO THE TEST. TEMPERATURE MEASUREMENTS ABOUT 40 SECONDS AFTER THE START OF THE TEST WERE AS FOLLOWS: TEST POINT (1): 65.1 DEGREES C. TEST POINT (2): 75.0 DEGREES C. TEST POINT (3): 33.4 DEGREES C. TEST POINT (4): 32.6 DEGREES C. THE INCREASE IN TEMPERATURE WAS SO SUDDEN THAT THE TEST WAS CONCLUDED ABOUT 40 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 INTERNAL PARTS WERE SOILED, ABRADED, 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 ABNORMAL RESISTANCE DURING ROTATION DUE TO THE BROKEN BEARING RETAINER. NAKANISHI 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, LEADING TO ABRASION. B) A LACK OF MAINTENANCE CAUSED THE ACCUMULATION OF DEBRIS ON THE INTERNAL PARTS, WHICH CAUSED DEBRIS 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 DISTRIBUTOR AND DIRECTED THE DISTRIBUTOR TO REMIND THE USER OF THE IMPORTANCE OF MAINTENANCE AS INSTRUCTED IN THE OPERATION MANUAL.

    Description of Event or Problem · 0

    ON JUNE 14, 2022, NAKANISHI MADE A PHONE CALL TO THE DENTAL OFFICE ABOUT AN INVESTIGATION RESULT OF A COMPLAINT AND BECAME AWARE OF AN NSK HANDPIECE OVERHEATING FROM THE COMMUNICATION. THE DETAILS NAKANISHI OBTAINED IS AS FOLLOWS. THE EVENT OCCURRED ON (B)(6) 2022. THE DENTIST WAS PERFORMING A DENTAL PROCEDURE ON THE UPPER RIGHT JAW OF A PATIENT USING THE Z95L HANDPIECE (SERIAL NO. (B)(4)) THE DENTIST FOUND A BURN INJURY AFTER THE PROCEDURE. THE DENTIST DETERMINED THAT NO MEDICAL TREATMENT WAS REQUIRED FOR THE INJURY. ACCORDING TO THE DENTIST, THERE WAS NO ABNORMALITIES OBSERVED IN THE DEVICE PRIOR TO USE.

    Devices

    Seq Brand Generic Product Code Manufacturer Model Lot UDI-DI
    982856 NSK HANDPIECE, CONTRA- AND RIGHT-ANGLE ATTACHMENT, DENTAL EGS NAKANISHI INC. Z95L

    Patients

    Seq Age Sex Outcome Treatment
    1 Unknown Other