MAUDE Adverse Event Report: NAKANISHI INC. NSK; HANDPIECE, ROTARY BONE CUTTING

Model Number Z-SG45L

Device Problem Overheating of Device (1437)

Patient Problem Burn(s) (1757)

Event Date 06/14/2022

Event Type  Injury  

Event Description

On (b)(6) 2022, nakanishi received a phone call from a dealer about an nsk handpiece overheating.The details nakanishi obtained are as follows: the event occurred on (b)(6) 2022.The dentist was performing a dental procedure on a patient using the z-sg45l handpiece (b)(4).During the procedure, the handpiece overheated, and the patient received a burn injury to their buccal mucosa.The dentist applied an oral ointment to the patient.

Manufacturer Narrative

The dentist refused to provide about the patient's weight.This event occurred in japan, but similar products are marketed in the us under k211584.Upon receiving the device involved in the mdr event, 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: nakanishi examined the device history record and the repair history for the subject z-sg45l device (b)(4).There were no problems observed during manufacturing or testing noted in the dhr.The repair history showed 4 service records since the device was shipped.The repair details are as follows: june 2018: the cartridge, drive shaft, and dog clutch were replaced.February 2019: the cartridge was replaced.March 2021: the cartridge, drive shaft, and dog clutch were replaced.May 2022: same as above.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.Nakanishi conducted temperature testing of the returned device in the following manner: 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.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 (120,000min-1 for the handpiece), with water spray, and measured the exothermic response.Nakanishi measured the temperature rise of the returned handpiece set at 120,000min-1 (motor revolution 40,000min-1).Nakanishi observed an abnormal temperature rise at test points (4) 5 minutes after the start of the test.Temperature measurements about 5 minutes after the start of the test were as follows: test point (1): 31.3 degrees c; test point (2): 33.4 degrees c; test point (3): 43.2 degrees c; test point (4): 51.9 degrees c.Nakanishi cleaned the inside of the handpiece using nakanishi pana spray plus.Nakanishi then conducted temperature testing of the device in the same manner as above yet again.There was no abnormal rise in temperature during the 5-minute test period.Temperature measurements 5 minutes into the test were as follows: test point (1): 31.7 degrees c; test point (2): 32.4 degrees c; test point (3): 37.8 degrees c; test point (4): 38.4 degrees c.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 that the cartridge, the drive shaft, and the headcap 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: nakanishi did not identify the exact cause, but based on the findings in the temperature testing, as well as many years of experience, nakanishi considers it is possible that the cause of handpiece overheating was the excessive lubricating oil generating heat during rotation into the handpiece cartridge.A lack of maintenance caused the excessive lubricating oil on the internal parts, which contributed to the handpiece overheating.In order to prevent a recurrence of the handpiece overheating, nakanishi took the following actions: nakanishi reviewed the operation manual and reconfirmed the clarity and understandability of the instructions.Nakanishi reported the above evaluation results to the dentist and directed the dentist to remind the user of the importance of maintenance as instructed in the operation manual.

• Brand Name: NSK
• Type of Device: HANDPIECE, ROTARY BONE CUTTING
• 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: 14951778
• MDR Text Key: 295477024
• Report Number: 9611253-2022-00046
• Device Sequence Number: 1
• Product Code: KMW
• Combination Product (y/n): N
• Reporter Country Code: JA
• 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: 07/08/2022

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: Z-SG45L
• Device Catalogue Number: C1107
• Was Device Available for Evaluation?: Device Returned to Manufacturer
• Date Returned to Manufacturer: 06/27/2022
• Initial Date Manufacturer Received: 06/15/2022
• Initial Date FDA Received: 07/07/2022
• Was Device Evaluated by Manufacturer?: Yes
• Date Device Manufactured: 04/11/2014
• 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 Age: 55 YR
• Patient Sex: Female
• Patient Ethnicity: Non Hispanic
• Patient Race: Asian