MAUDE Adverse Event Report: NAKANISHI INC. NSK; HANDPIECE, AIR-POWERED, DENTAL

Model Number	Z890L
Medical Device Problem Code	Overheating of Device (1437)
Health Effect - Clinical Code	Partial thickness (Second Degree) Burn (2694)
Type of Reportable Event	Serious Injury
Additional Manufacturer Narrative
Patient information and date of the adverse event have not been provided by the dental practice at the time of this report.A follow-up report will be made if this information is made available by the dental office.
Event or Problem Description
On (b)(6) , 2025, nakanishi became aware of a handpiece overheating through a complaint input into the complaint database by a distributor (nsk america).According to the distributor, 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 dentist was performing a dental procedure on a patient using the z890l handpiece (serial no.(b)(6) ) - during the procedure, the back of the handpiece head overheated, and the patient received a thermal burn injury to their inner cheek.
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 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 z890l 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 temperature testing of the returned device in the following manner: b.1) temperature sensors were attached to the exterior of the handpiece head at 2 test points.This included the side of the head (testing point (1)) and push button of the head (testing points (2)).The test setup was prepared to take temperature measurements at both 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 handpiece at 0.28mpa with water spray and measured the exothermic response.B.3) nakanishi measured the temperature rise of the returned handpiece set at 0.28mpa.The maximum temperature measured in the 5-minute test were as follows: - test point (1): 24.7 degrees c.- test point (2): 27.1 degrees c.Nakanishi did not observe temperatures high enough to cause a burn injury.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 contact traces on the surfaces of the cartridge and headcap caused by a push button being pressed during rotation.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 did not identify the exact cause of overheating of the returned device because nakanishi was not able to replicate the temperature rise at the time of the event, but based on the findings in the visual inspection, as well as many years of experience, nakanishi considers the possibility that the cause of the handpiece overheating was frictional heat generated by contact between the headcap and the cartridge, which was caused by the push button being pressed during rotation.B) misuse by the user leads to the contact between the headcap and the cartridge, which 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 using the device as instructed in the operation manual.

• Brand Name: NSK
• Common Device Name: HANDPIECE, AIR-POWERED, 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: 23785469
• Report Number: 9611253-2025-00061
• Device Sequence Number: 5029869
• Product Code: EFB
• UDI-Device Identifier: 04589551385348
• UDI-Public: (01)04589551385348(11)231219
• Combination Product (Y/N): N
• Initial Reporter State: IL
• Initial Reporter Country: US
• PMA/510(K) Number: K230888
• 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: Dentist
• Type of Report: Initial,Followup
• Report Date (Section B): 03/03/2026

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: Z890L
• Device Catalogue Number: PA23720001
• Was Device Available for Evaluation?: Device Returned to Manufacturer
• Is the Reporter a Health Professional?: Yes
• Type of Report(Section G): Thirty-Day
• Initial Date Received by Manufacturer: 11/21/2025
• Supplement Date Received by Manufacturer: 02/10/2026
• Initial Report FDA Received Date: 12/11/2025
• Supplement Report FDA Received Date: 03/02/2026
• Was Device Evaluated by Manufacturer? (Y/N): Yes
• Date Device Manufactured: 11/10/2023
• 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