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

Model Number TI95L

Device Problems Overheating of Device (1437); Device Operates Differently Than Expected (2913); Temperature Problem (3022)

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

Event Date 09/24/2016

Event Type  Injury  

Manufacturer Narrative

Nakanishi contacted the dentist for more information on october 3, 2016 and october 5, 2016, but the dentist did not disclose the patient id and weight.

Event Description

On september 30, 2016, an nsk handpiece ti95l (gk900026) was returned to nakanishi from a distributor for repair.There was a note with the handpiece stating the handpiece had overheated and burned a patient.On october 5, 2016, nakanishi contacted the dentist for more information.The information nakanishi obtained is as follows.The event occured on (b)(6) 2016.The dentist was removing a fck (full cast crown) on tooth #6 in the right upper jaw using the ti95l.The patient received a 1cm diameter blister on the right side on her lip.When the handpiece touched the patient, the patient commented that the handpiece felt hot.The patient was not under local anesthesia.No malfunction was observed by the dentist prior to use.

Manufacturer Narrative

Upon receiving the device involved in the adverse event, nakanishi conducted a failure analysis of the returned device: methodology used: a) nakanishi examined the device history record for the subject ti95l device (serial number gk900026).There were no problems observed during the manufacturing or testing noted in the dhr.The repair history records showed one service record (march 2012) since the device was shipped.According to the service record, after repairing the handpiece (replacement of drive shaft, dog clutch, grip sleeve, cartridge, and elbow), nakanishi performed all of the necessary operation checks.Nakanishi confirmed that all of the criteria were met.B) investigation of overheating: b.1) temperature sensors were first attached to the exterior of the device at various test points (i.E.Most proximal to the patient, testing point (1), and along points further towards the distal end of the device, testing points (2) through (4)).The test was set up 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 point.Nakanishi rotated the motor at 40,000 min-1, which is maximum rpm for the motor that drives the handpiece (200,000 min-1 for the handpiece), with water spray, without any load, and measured the exothermic situation.B.3) nakanishi observed abnormal temperature rises at test points (1) and (2) 300 seconds after the start.Temperature measurements 300 seconds after the start are as follows: - test point (1): 46.6 degrees c, - test point (2): 50.4 degrees c, - test point (3): 41.6 degrees c, - test point (4): 39.2 degrees c.The temperature testing was conducted for the full 5 minute evaluation.C) identification of the specific failure mode(s) and/or mechanism(s) and the associated device components involved: c.1) nakanishi disassembled the handpiece and performed a visual inspection of the inside parts.- nakanishi observed that the bearing inner race (ball rolling surface) was worn.- nakanishi observed discoloration on the gear meshing portion.- nakanishi also confirmed wear to the gear meshing portion inside the cartridge gear part and the clutch gear part.C.2) nakanishi took photographs of all of the disassembled parts and kept them in a file.D) conclusion reached based on the investigation and analysis result: d.1) nakanishi identified that the cause of the overheating of the returned device was abnormal resistance during rotation caused by wear of the bearing inner race.D.2) a lack of maintenance causes the accumulation of dirt (abrasive powders/foreign materials) in the inside parts, which causes dirt/debris ingress into the bearing during rotation.This contributes to the handpiece overheating.D.3) in order to prevent a recurrence of the handpiece overheating, nakanishi took the following actions: d.3.1) nakanishi reviewed the operation manual and reconfirmed clarity and understandability of the instructions.D.3.2) nakanishi reported the above evaluation results to the dentist and reminded the dentist of importance of checking the handpiece prior to use to prevent overheating, 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
• Manufacturer (Section G): NAKANISHI INC.; 700 shimohinata; kanuma-shi, tochigi-ken 322-8 666; JA 322-8666
• Manufacturer Contact: kenneth block ; 1201 richardson dr.; suite 160; richardson, TX 75080 ; 9724809554
• MDR Report Key: 6050623
• MDR Text Key: 58183634
• Report Number: 9611253-2016-00060
• Device Sequence Number: 1
• Product Code: EGS
• Combination Product (y/n): N
• Reporter Country Code: JA
• PMA/PMN Number: K972569
• Number of Events Reported: 1
• Summary Report (Y/N): N
• Report Source: Manufacturer
• Source Type: distributor,foreign
• Reporter Occupation: Other
• Type of Report: Initial,Followup
• Report Date: 03/27/2017

1 Device was Involved in the Event

1 Patient was Involved in the Event

• Date FDA Received: 10/24/2016
• Is this an Adverse Event Report?: Yes
• Is this a Product Problem Report?: No
• Device Operator: Dentist
• Device Model Number: TI95L
• Device Catalogue Number: C448001
• Was Device Available for Evaluation?: Device Returned to Manufacturer
• Date Returned to Manufacturer: 09/30/2016
• Is the Reporter a Health Professional?: No
• Date Manufacturer Received: 09/30/2016
• Was Device Evaluated by Manufacturer?: Yes
• Date Device Manufactured: 09/09/2009
• 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: 48 YR