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

Model Number Z95L

Device Problem Overheating of Device (1437)

Patient Problems Burn(s) (1757); Burn, Thermal (2530); Partial thickness (Second Degree) Burn (2694)

Event Date 12/22/2020

Event Type  Injury  

Manufacturer Narrative

The same adverse event in this report has been reported to the fda separately by the initial importer, (b)(4).

Event Description

On january 23, 2021, nakanishi became aware of a handpiece overheating through a complaint input into the complaint database by a distributor ((b)(4)).Details are as follows: - the event occurred on (b)(6) 2020.- a dentist was performing a posterior composite procedure on a patient using the z95l handpiece (serial no.(b)(4)).- the patient was under local anesthesia.- during the procedure, the patient complained about heat from the device.- the dentist observed blistering on the left dorsal of the patient's tongue and left cheek.- the injuries were immediately treated with a cool rinse and topical application of tx lidocaine ointment.- according to the dentist, there were no abnormalities observed in the device prior to use.- the patient has had a follow-up and is reported to be healing normally with no complications.

Manufacturer Narrative

Upon receiving the device involved in the mdr event from the distributor, nakanishi conducted a failure analysis of the returned device, which included measuring the operating temperature of the 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 z95l device [serial no.(b)(6) ].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 set a test bur in the handpiece, connected the handpiece to the motor, and tried to rotate the motor.However, the handpiece was locked and the motor 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 on the rear side of the cartridge was broken.The internal parts were discolored and soiled.B) nakanishi took photographs of all of the disassembled parts and kept them in investigation report #(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, as well as many years of experience, nakanishi identified that the cause of the handpiece overheating was abnormal resistance during rotation due to the broken bearing caused, which was by ingress of foreign materials into the handpiece.B) a lack of maintenance caused the accumulation of debris on the inside 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 clarity and understandability of the instructions.C.2) 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.

• 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
• MDR Report Key: 11306100
• MDR Text Key: 231146593
• Report Number: 9611253-2021-00007
• Device Sequence Number: 1
• Product Code: EGS
• Combination Product (y/n): N
• PMA/PMN Number: K182999
• Number of Events Reported: 1
• Summary Report (Y/N): N
• Report Source: Manufacturer
• Source Type: company representative
• Type of Report: Initial,Followup
• Report Date: 03/22/2021

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: Z95L
• Device Catalogue Number: C1034
• Was Device Available for Evaluation?: Device Returned to Manufacturer
• Date Returned to Manufacturer: 02/18/2021
• Initial Date Manufacturer Received: 01/23/2021
• Initial Date FDA Received: 02/10/2021
• Supplement Dates Manufacturer Received: 03/01/2021
• Supplement Dates FDA Received: 03/22/2021
• Is This a Reprocessed and Reused Single-Use Device?: No
• Patient Sequence Number: 1
• Patient Outcome(s): Other
• Patient Age: 48 YR
• Patient Weight: 48