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

Model Number	Z95L
Medical Device Problem Code	Overheating of Device (1437)
Health Effect - Clinical Code	Partial thickness (Second Degree) Burn (2694)
Date of Event	03/10/2026
Type of Reportable Event	Serious Injury
Event or Problem Description
On april 10, 2026, nakanishi became aware of a handpiece overheating through a complaint input into the complaint database by a distributor (nsk america).Details are as follows: the event occurred on march 10, 2026.The dentist was performing a filling procedure on teeth numbers 3, 4, 5, 28, 30 of a patient using the z95l handpiece (serial no.(b)(6).During the procedure, the handpiece head overheated abnormally, and the patient received a thermal burn injury to their inner cheek mucosa.No medical treatment was required at the time of the injury.The patient has had a follow up visit after the incident and is reported to have healed normally without need for additional medical treatment.
Additional Manufacturer Narrative
The end-user declined to provide patient information.
Additional 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 (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 conducted a visual inspection of the returned device and observed that the headcap was separated from the device and that the bearing was broken.Therefore, nakanishi was not able to conduct temperature testing on 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 other internal parts were soiled and discolored.B) nakanishi took photographs of all the disassembled parts and kept them in the 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, nakanishi identified that the cause of the handpiece overheating was abnormal resistance during rotation due to the broken bearing retainer.B) 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.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 the 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 distributor and directed the distributor to remind the user of the importance of maintenance, as instructed in the operation manual.

• Brand Name: NSK
• Common Device Name: 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: 25038940
• Report Number: 9611253-2026-00019
• Device Sequence Number: 10325012
• Product Code: EGS
• UDI-Device Identifier: 04560264575448
• UDI-Public: (01)04560264575448
• Combination Product (Y/N): N
• Initial Reporter State: WA
• Initial Reporter Country: US
• PMA/510(K) Number: K182999
• Number of Events Summarized: 1
• Summary Report (Y/N): N
• Serviced by Third Party (Y/N): Unknown
• Reporter Type: Manufacturer
• Report Source: Company Representative,Distributor
• Initial Reporter Occupation: Administrator/Supervisor
• Type of Report: Initial,Followup
• Report Date (Section B): 06/09/2026

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
• Operator of Device: Health Professional
• Device Model Number: Z95L
• Device Catalogue Number: C1034
• Was Device Available for Evaluation?: Device Returned to Manufacturer
• Date Returned to Manufacturer: 04/21/2026
• Type of Report(Section G): Thirty-Day
• Initial Date Received by Manufacturer: 04/10/2026
• Supplement Date Received by Manufacturer: 05/21/2026
• Initial Report FDA Received Date: 04/30/2026
• Supplement Report FDA Received Date: 06/09/2026
• Was Device Evaluated by Manufacturer? (Y/N): Yes
• Date Device Manufactured: 01/28/2020
• Is the Device Labeled for Single Use? (Y/N): No
• Is This a Single-Use Device that was Reprocessed and Reused on a Patient? (Y/N): No
• Usage of Device: Reuse
• Patient Sequence Number: 1
• Outcome Attributed to Adverse Event: Other
• Patient Sex: Unknown