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

Model Number SGS-E2S

Device Problems Overheating of Device (1437); Temperature Problem (3022)

Patient Problems Burn(s) (1757); Injury (2348); Patient Problem/Medical Problem (2688)

Event Date 04/07/2017

Event Type  Injury  

Manufacturer Narrative

(b)(4).The information received from (b)(4) is as follows.- on april 17, 2017, and april 20, 2017, (b)(4) contacted the dental office by phone and email to request patient information, but the dental office did not disclose the patient information.- no service has been conducted at (b)(4) on the subject device ((b)(4)).

Event Description

On april 24, 2017, nakanishi received an email from a distributor ((b)(4)) describing a patient injury.Details are as follows.- on april 13, 2017, (b)(4) was made aware of an unconfirmed patient injury from information provided from the incoming service repair paperwork.- the event occurred on (b)(6) 2017.- (b)(4) immediately contacted the dental office and spoke with the dentist's assistant.- the dentist's assistant stated that the neck of the handpiece became extremely hot and burned a patient's lip.- no other information regarding the patient was available at this time.- (b)(4) contacted the dental office to obtain more information , and the nsk patient information form was immediately forwarded to the dental office to be completed.

Manufacturer Narrative

Upon receiving the device involved in the mdr event from a distributor, nakanishi conducted a failure analysis of the returned device that included measuring the operating temperature of the device [c170425-13-1].These activities are described in more detail below.Methodology used: nakanishi examined the device history record and the repair history for the subject sgs-e2s device [serial number (b)(4)].There were no problems observed during the manufacturing or testing noted in the dhr.There were also no repair history records since the device was shipped.Nakanishi conducted a visual inspection of the returned device and performed a simple movement test.There were no visible abnormalities, such as cracks or dents, on the outside of the handpiece.Nakanishi then set a test bur in the handpiece and rotated it by hand.Nakanishi observed that the bur did not rotate smoothly.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 a temperature) to each of the testing points.Nakanishi rotated the device's motor at 40,000 min-1, which is the maximum rpm for the motor that drives the handpiece (80,000 min-1 for the handpiece), and measured the exothermic response.Nakanishi measured the temperature rise of the returned handpiece set at 80,000 min-1 (motor revolution 40,000 min-1).Nakanishi observed an abnormal temperature rise at test point (1) and (2) a few seconds after the start.Temperature measurements 198 seconds after the start are as follows: test point (1): 62.7 degrees c, test point (2): 63.7 degrees c, test point (3): 43.8 degrees c, test point (4): 48.7 degrees c.Since the temperature rose high enough to cause a burn injury before the planned 5 minute evaluation period, the test was concluded 198 seconds.Nakanishi cleaned the inside of the handpiece using nakanishi pana spray plus.Nakanishi observed debris being expelled from the head of the handpiece by using a white filter to catch anything that was expelled.After cleaning and lubricating the handpiece as defined in the operation manual, nakanishi measured the temperature of the handpiece for the entire 5-minute evaluation period.After cleaning, nakanishi did not observe any abnormal temperature rise to cause a burn injury in the evaluation.However the temperatures nakanishi observed were higher than normal level as follows.Test point (1): 43.0 degrees c, test point (2): 41.1 degrees c, test point (3): 43.5 degrees c, test point (4): 49.9 degrees c.Identification of the specific failure mode(s) and/or mechanism(s) and the associated device components involved: nakanishi disassembled the handpiece and performed a visual inspection of the inside parts.Nakanishi observed the following phenomena: there was significant debris and rust on the bearings incorporated in the testing point (1).- there was also extensive debris on the bearing in the testing point (2).Nakanishi took photographs of all of the disassembled parts and kept them in a file.Nakanishi then replaced the soiled bearings and measured the exothermic situation yet again.There was no abnormal rise in temperature during the test period (see below).Nakanishi confirmed that the returned handpiece was operating as expected and within temperature specifications once the soiled bearings had been replaced.Test point (1): 42.3 degrees c, test point (2): 39.6 degrees c, test point (3): 38.8 degrees c, test point (4): 42.3 degrees c.Conclusions reached based on the investigation and analysis results: nakanishi identified that the cause of the overheating of the returned device was abnormal resistance during rotation caused by the soiled bearings due to the ingress of undesirable materials into the bearing.A lack of maintenance causes the accumulation of debris on the inside parts, which causes debris ingress into the bearing during rotation.This contributes 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 clarity and understandability of the instructions.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.

Manufacturer Narrative

On (b)(6) 2019, nakanishi was informed by the distributor (nam) that nam had taken the following actions as a part of the ifu recall activities.In (b)(6) 2018 (exact date unknown), the distributor sent the updated operation manuals that contain the detailed reprocessing method, which had been provided by nam earlier, to the dental office to prevent the devices from overheating.On (b)(6) 2018, nam confirmed the receipt of the operation manuals through the activity sheet mailed by the dentist.

• 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
• MDR Report Key: 6563159
• MDR Text Key: 75089018
• Report Number: 9611253-2017-00026
• Device Sequence Number: 1
• Product Code: KMW
• Combination Product (y/n): N
• PMA/PMN Number: K171155
• Number of Events Reported: 1
• Summary Report (Y/N): N
• Report Source: Manufacturer
• Source Type: distributor,health profession
• Remedial Action: Recall
• Type of Report: Initial,Followup,Followup,Followup
• Report Date: 04/22/2017,08/05/2019

1 Device was Involved in the Event

1 Patient was Involved in the Event

• Date FDA Received: 05/12/2017
• Is this an Adverse Event Report?: Yes
• Is this a Product Problem Report?: No
• Device Operator: Dentist
• Device Model Number: SGS-E2S
• Device Catalogue Number: H266001
• Was Device Available for Evaluation?: Yes
• Was the Report Sent to FDA?: No
• Distributor Facility Aware Date: 04/13/2017
• Device Age: 1 YR
• Event Location: Other
• Date Report to Manufacturer: 04/22/2017
• Date Manufacturer Received: 07/20/2019
• Is This a Reprocessed and Reused Single-Use Device?: No
• Removal/Correction Number: 9611253-060818-001-R
• Patient Sequence Number: 1
• Patient Outcome(s): Other