MAUDE Adverse Event Report: NAKANISHI INC. NSK; HANDPIECE, CONTRA- AND RIGHT-ANGLE ATTACHMENT, DENTAL

Model Number X95L

Device Problems Overheating of Device (1437); Use of Device Problem (1670); Temperature Problem (3022)

Patient Problems Burn(s) (1757); Burning Sensation (2146); Injury (2348); Burn, Thermal (2530); Patient Problem/Medical Problem (2688)

Event Date 01/02/2019

Event Type  Injury  

Manufacturer Narrative

(b)(4).According to the distributor, the dentist refused to provide the patient's weight.

Event Description

On january 11, 2019, nakanishi received an e-mail from a distributor ((b)(4)) about a handpiece overheating.Details are as follows.The event occurred on (b)(6) 2019.The dentist was performing a crown preparation on a patient using the x95l handpiece (serial no.(b)(4)).The patient was under local anesthesia.When the patient complained of a burning sensation in the mouth to the dentist, the dentist immediately removed the handpiece from the patient's mouth.The dentist found a quarter sized, oval shaped burn on the patient's upper right cheek.No treatment for the injury was administered in the office at the time of the event.The practice has conducted a follow up with the patient over the phone, and the patient has reported that the injury is healing normally.The dentist determined that no further medical attention was required for the injury.

Manufacturer Narrative

Upon receiving the device involved in the mdr event from the distributor, nakanishi conducted a failure analysis of the returned device that included measuring the operating temperature of the device [c190111-01].These activities are described in more detail below.Methodology used: a) nakanishi examined the device history record and the repair history for the subject x95l device [serial number dbe90730].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 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.B.2) nakanishi attached a thermocouple (sensor to measure 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 (200,000 min-1 for the handpiece), with water spray, and measured the exothermic response.B.3) nakanishi measured the temperature rise of the returned handpiece set at 200,000 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 52 seconds after the start are as follows: - test point (1): 46.3 degrees c - test point (2): 61.8 degrees c - test point (3): 35.7 degrees c - test point (4): 35.8 degrees c the rise in temperature was so sudden that the test was concluded 52 seconds into the planned 5-minute evaluation period.Identification of the specific failure mode(s) and/or mechanism(s) and the associated device components involved: a) nakanishi disassembled the handpiece and performed a visual inspection of the inside parts.Nakanishi observed the following phenomena: - the bearing retainer (ball retaining part) on the cartridge rear side was broken.- the drive shaft and dog clutch were partially corroded.B) nakanishi took photographs of all of the disassembled parts and kept them in the investigation report #(b)(4).Conclusions reached based on the investigation and analysis results: 1) nakanishi identified that the cause of the overheating of the returned device was abnormal resistance during rotation caused by the broken bearing.2) nakanishi considers the possibility from many years of experience that the cause of the ball bearing being broken was the ingress of undesirable materials into the bearing.3) 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.4) in order to prevent a recurrence of the handpiece overheating, nakanishi took the following actions: 4.1) nakanishi reviewed the operation manual and reconfirmed the clarity and understandability of the instructions.4.2) 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.

• Brand Name: NSK
• Type of Device: HANDPIECE, CONTRA- AND RIGHT-ANGLE ATTACHMENT, DENTAL
• Manufacturer (Section D): NAKANISHI INC.; 700 shimohinata; kanuma-shi, tochigi-ken 322-8 666; JA 322-8666
• MDR Report Key: 8305079
• MDR Text Key: 135005700
• Report Number: 9611253-2019-00005
• Device Sequence Number: 1
• Product Code: EGS
• Combination Product (y/n): N
• PMA/PMN Number: K972569
• Number of Events Reported: 1
• Summary Report (Y/N): N
• Report Source: Manufacturer
• Source Type: company representative
• Type of Report: Initial,Followup
• Report Date: 01/11/2019,03/18/2019

1 Device was Involved in the Event

1 Patient was Involved in the Event

• Date FDA Received: 02/05/2019
• Is this an Adverse Event Report?: Yes
• Is this a Product Problem Report?: Yes
• Device Operator: Health Professional
• Device Model Number: X95L
• Device Catalogue Number: C600
• Was Device Available for Evaluation?: Device Returned to Manufacturer
• Date Returned to Manufacturer: 02/08/2019
• Was the Report Sent to FDA?: No
• Distributor Facility Aware Date: 01/10/2019
• Device Age: 4 YR
• Event Location: Outpatient Treatment Facility
• Date Report to Manufacturer: 01/11/2019
• Date Manufacturer Received: 02/21/2019
• Is This a Reprocessed and Reused Single-Use Device?: No
• Patient Sequence Number: 1
• Patient Outcome(s): Other
• Patient Age: 72 YR