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

Device Problem Insufficient Information (3190)

Patient Problem Burn, Thermal (2530)

Event Type  Injury  

Event Description

Imp ref: (b)(4).

Manufacturer Narrative

Upon receipt from nsk america of the device involved in the mdr event, nakanishi conducted a failure analysis of the returned device that included measurement of the temperature of the operating device [c141106-14-1].These activities are described in more detail below.Methodology used: nakanishi examined the device history record for the subject sga-e2s [serial number (b)(4)].There were no problems observed during the manufacturing or testing noted in the dhr.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 rotating the bur by hand to observe bearing condition.Nakanishi observed that the bur did not rotate smoothly.The device was configured for temperature testing in the exact state in which it was returned.Specifically, no lubrication or cleaning was performed on the returned device before this first test in order to characterize the device under conditions that would duplicate the use situation at the time of the event.Temperature sensors were first attached to the exterior of the device at various test points (e.G., most proximal to the patient and along points further toward the distal end of the device).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 a, b, c and d.Nakanishi rotated the handpiece at 40,000min-1, which is maximum rpm for the motor that drives the handpiece (80,000 min-1 for the handpiece), with no water spray and measured the exothermic situation.Nakanishi measured the temperature rise of the returned handpiece set at 80,000min-1 (motor revolution 40,000min-1).Nakanishi confirmed the temperature rise at the test points a and b (points close to the patient) as follows after the beginning of the measurement; (a) 65.9 degree c and (b) 80.0 degree c.The rise was so sudden that the temperatures, 65.9 degree c and 80.0 degree c were observed only within 2 minutes into the planned 5 minutes evaluation period.Identification of the specific failure mode(s) and/or mechanism(s) and the associated device component(s) involved.Nakanishi cleaned the inside of the handpiece using nakanishi pana-spray as defined in the operation manual.Nakanishi observed dirt/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.Even after cleaning, nakanishi still observed a quick rise in temperature.Nakanishi disassembled the handpiece and performed a visual inspection of the inside parts.Nakanishi observed damage on the cartridge bearing.Nakanishi then replaced the damaged bearing and measured the exothermic situation yet again.There was no abnormal temperature rising during the test period.Nakanishi confirmed that the returned handpiece was operating as expected and within temperature specifications once the damaged bearing had been replaced.Conclusions reached based on the investigation and analysis results.Nakanishi identified that the cause of overheating of the returned device was due to damage to the bearing.The damage observed caused abnormal rotation resistance, which would result in the handpiece overheating.The damage observed is consistent with a lack of proper lubrication and cleaning after use.A lack of maintenance causes accumulation of abrasive powders in the head, which cause damage to the bearing.The damaged parts will contribute to the handpiece overheating.

Manufacturer Narrative

On july 20, 2019, nakanishi was informed by the distributor (b)(4) that (b)(4) had taken the following actions as a part of the ifu recall activities.On october 15, 2018, (b)(4) sent the updated operation manuals that contain the detailed reprocessing method to the dental office to prevent the devices from overheating.On october 22, 2018, (b)(4) confirmed the receipt of the operation manuals by the dentist through usps certified receipt.

• Brand Name: NSK
• Type of Device: HANDPIECE, ROTARY BONE CUTTING
• MDR Report Key: 4385947
• MDR Text Key: 22160595
• Report Number: 9611253-2014-00033
• 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: User Facility,user facility
• Remedial Action: Recall
• Type of Report: Initial,Followup,Followup,Followup
• Report Date: 08/02/2019

1 Device was Involved in the Event

1 Patient was Involved in the Event

• Date FDA Received: 12/05/2014
• Is this an Adverse Event Report?: No
• Is this a Product Problem Report?: No
• Device Operator: Other
• Date Manufacturer Received: 07/20/2019
• Removal/Correction Number: 9611253-060818-001-R
• Patient Sequence Number: 1