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

Model Number SGS-E2G

Device Problems Overheating of Device (1437); Device Issue (2379); Temperature Problem (3022)

Patient Problems Burn(s) (1757); Injury (2348)

Event Date 08/01/2016

Event Type  Injury  

Manufacturer Narrative

(b)(4).Nakanishi is submitting two separate mdrs for this event because two handpieces might have been involved.This mdr is regarding the handpiece with the serial number (b)(4).(b)(4) made the following attempts to obtain further information, including patient information, from the dentist, but no other information was obtained.On august 8, 2016, (b)(4) made a phone call to the dental office and left a voice mail.(b)(4) sent form qa-011, additional information request, requesting the information by email.No reply was received.August 9, 2016, (b)(4) called the office and left a message for the dentist through a receptionist.At this time, (b)(4) confirmed that the office received the form sent on august 8, 2016.No response from the dentist was received.August 10, 2016, (b)(4) sent an email offering assistance with the form qa-011 and requesting to speak with someone to obtain the information.A contact person was offered.The contact person committed verbally to forward the requested forms.August 12, 2016, (b)(4) sent an email to the dental office offering assistance.No response.August 15, 2016, (b)(4) contacted the office and left a message for the contact person.No response.

Event Description

On august 23, 2016, nakanishi received an e-mail from a distributor ((b)(4)) about a handpiece overheating.Details are as follows.On august 8, 2016, (b)(4) was made aware of unconfirmed patient burn by the incoming service repair notes.The event occurred on (b)(6) 2016.A dentist was removing third molars from a patient's mouth using a handpiece, sgs-e2g.During the procedure, the patient's lip was severely burned.There are 2 possible sgs-e2g handpieces involved in the event (serial no.(b)(4)), but the dentist cannot identify which handpiece actually caused the event.With respect to the handpiece with serial no.(b)(4), the dentist did not feel an excessive rise in temperature in the handpiece while in use.

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 temperature of the operating device [(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 sgs-e2g 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 situation.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 (2) a few seconds after the start.Temperature measurements 14 seconds after the start are as follows: - test point (1): 48.6 degrees c.- test point (2): 92.8 degrees c.- test point (3): 30.1 degrees c.- test point (4): 32.0 degrees c.The rise in temperature was so sudden that the test was ended only 14 seconds into the planned 5 minutes evaluation period.Nakanishi washed the inside of the handpiece using nakanishi pana spray plus.Nakanishi observed dirt 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.Even after cleaning, nakanishi still observed a quick rise in temperature, as follows.- test point (1): 46.1 degrees c.- test point (2): 69.6 degrees c.- test point (3): 31.4 degrees c.- test point (4): 33.6 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 inner race coming off and breakage of the inner race in the bearings.Nakanishi took photographs of all of the disassembled parts and kept them in a file.C) nakanishi then replaced the broken bearing 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 damaged bearing had been replaced.- test point (1): 47.7 degrees c.- test point (2): 42.0 degrees c.- test point (3): 37.0 degrees c.- test point (4): 37.7 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 broken bearings due to the ingress of dirt into the bearing.A lack of maintenance causes the accumulation of dirt in the inside parts, which causes dirt ingress into the bearing during rotation, leading to the broken bearings.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 july 20, 2019, nakanishi was informed by the distributor (nam) that nam had taken the following actions as a part of the ifu recall activities.- on december 13, 2018, nam sent the updated operation manuals that contain the detailed reprocessing method to the dental office to prevent the devices from overheating.- on december 17, 2018, nam confirmed the receipt of the operation manuals by the dentist through usps certified receipt.

• 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: 5956229
• MDR Text Key: 54942050
• Report Number: 9611253-2016-00051
• 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: company representative
• Remedial Action: Recall
• Type of Report: Initial,Followup,Followup,Followup
• Report Date: 08/23/2016,08/05/2019

1 Device was Involved in the Event

1 Patient was Involved in the Event

• Date FDA Received: 09/16/2016
• Is this an Adverse Event Report?: Yes
• Is this a Product Problem Report?: No
• Device Operator: Dentist
• Device Model Number: SGS-E2G
• Device Catalogue Number: H185
• Was Device Available for Evaluation?: Device Returned to Manufacturer
• Date Returned to Manufacturer: 08/24/2016
• Was the Report Sent to FDA?: No
• Distributor Facility Aware Date: 08/08/2016
• Device Age: 10 YR
• Event Location: Other
• Date Report to Manufacturer: 08/23/2016
• 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