MAUDE Adverse Event Report: NAKANISHI INC. NSK; HANDPIECE, CONTRA- AND RIGHT-ANGLE ATTACHMENT, DENTAL

Model Number Z85L

Device Problem Overheating of Device (1437)

Patient Problem Burn(s) (1757)

Event Date 02/19/2024

Event Type  Injury  

Event Description

On march 1, 2024, a nsk z85l handpiece was returned from a distributor to nakanishi for repair.There was a note with the device stating that the device had overheated and burned a patient.Upon receipt of the information, nakanishi made a phone call to the dealer and visited the dental office for further information about the event including information about the patient.According to the dentist, two patients were involved with the device.Therefore, nakanishi is submitting two mdrs for the two patients.The details nakanishi obtained about the first patient are as follows.The details nakanishi obtained are as follows.- the event occurred on february 19, 2024.- the dentist was performing a tooth forming on a patient using the z85l handpiece (serial no.(b)(6) ).- the patient was under anesthesia.- after the procedure was completed, the dentist found that the patient received a burn injury with a blister to the patient's buccal mucosa.- the dentist did not find that the handpiece overheated because the dentist was wearing gloves at the time of the incident.- according to the dentist, there was no abnormalities observed in the device prior to use.- the dentist applied an oral ointment to the burn injury.- the dentist has had a follow up with the patient and the burn injury is reported to have healed normally with no additional medical treatment necessary.

Manufacturer Narrative

The dentist refused to provide any information 's age, gender, and weight.Upon receiving the device involved in the mdr event, nakanishi conducted a failure analysis of the returned device [report no.(b)(4) ].These activities are described in more detail below.Methodology used: a) nakanishi examined the device history record and the repair history for the subject z85l device [ (b)(6) ].There were no problems observed during manufacturing or testing noted in the dhr.The repair history showed 2 service records since the device was shipped.The repair details are as follows: - february 2021: the cartridge, dog clutch, and drive shaft were replaced.- december 2021: the cartridge, dog clutch, and drive shaft were replaced.With respect to the repairs in the above list, the service records indicate that nakanishi performed all of the necessary operation checks and confirmed that all of the criteria were met.B) nakanishi connected the handpiece to the motor and tried to rotate the motor.However, the handpiece was locked and did not rotate at all.Therefore, nakanishi was not able to conduct temperature testing of the device.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 gears, dog clutch, and headcap 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 could not replicate the temperature increase from the event, but based on the findings in the visual inspection, nakanishi determined that the cause of the handpiece overheating was frictional resistance generated by contact between the ball bearing retainer, the outer and inner races, and bearing balls, which was caused by the broken ball bearing.B) nakanishi also considers the possibility from many years of experience, that the cause of the broken bearing retainer 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.

• Brand Name: NSK
• Type of Device: HANDPIECE, CONTRA- AND RIGHT-ANGLE ATTACHMENT, DENTAL
• Manufacturer (Section D): NAKANISHI INC.; 700 shimohinata; kanuma-shi, tochigi-ken 322-8 666; JA 322-8666
• Manufacturer (Section G): NAKANISHI INC.; 700 shimohinata; kanuma-shi, tochigi-ken 322-8 666; JA 322-8666
• Manufacturer Contact: sean kaufman ; 1800 global parkway; hoffman estates, IL 60192 ; 2245128921
• MDR Report Key: 18994380
• MDR Text Key: 338889426
• Report Number: 9611253-2024-00015
• Device Sequence Number: 1
• Product Code: EGS
• Combination Product (y/n): N
• Reporter Country Code: JA
• PMA/PMN Number: K972569
• Number of Events Reported: 1
• Summary Report (Y/N): N
• Report Source: Manufacturer
• Source Type: Other,Foreign
• Reporter Occupation: Non-Healthcare Professional
• Type of Report: Initial
• Report Date: 03/28/2024

1 Device was Involved in the Event

1 Patient was Involved in the Event

• Is this an Adverse Event Report?: Yes
• Is this a Product Problem Report?: Yes
• Device Operator: Health Professional
• Device Model Number: Z85L
• Device Catalogue Number: C1062
• Was Device Available for Evaluation?: Device Returned to Manufacturer
• Date Returned to Manufacturer: 03/04/2024
• Initial Date Manufacturer Received: 03/01/2024
• Initial Date FDA Received: 03/28/2024
• Was Device Evaluated by Manufacturer?: Yes
• Date Device Manufactured: 04/05/2018
• Is the Device Single Use?: No
• Is This a Reprocessed and Reused Single-Use Device?: No
• Type of Device Usage: Reuse
• Patient Sequence Number: 1
• Patient Outcome(s): Other
• Patient Sex: Female
• Patient Ethnicity: Non Hispanic
• Patient Race: Asian