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

Model Number Z95L

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

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

Event Date 05/24/2018

Event Type  Injury  

Manufacturer Narrative

The dentist refused to provide information about the patient's id, age and weight in the conversation with nakanishi.

Event Description

On may 25, 2018, nakanishi received a phone call from a dealer about an nsk handpiece overheating.Upon receipt of the information, nakanishi visited the dental office for further information about the event.The details nakanishi obtained from the dentist are as follows.The event occurred on (b)(6) 2018.The dentist was performing a cavity preparation of tooth #3 of the patient's upper right jaw using the handpiece z95l (serial no.(b)(4)).The patient was not under anesthesia.During the procedure, the patient complained about the handpiece overheating.The dentist found a one-centimeter burn injury on the patient's upper right lip.

Manufacturer Narrative

Upon receiving the device involved in the mdr event, nakanishi conducted a failure analysis of the returned device that included measuring the operating temperature of the device [c180528-04].These activities are described in more detail below.Methodology used: a) nakanishi examined the device history record and the repair history for the subject z95l device [serial (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.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 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 (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 (1) and (2) a few seconds after the start.Temperature measurements 21 seconds after the start are as follows: test point (1): 70.8 degrees c, test point (2): 95.0 degrees c, test point (3): 44.5 degrees c, test point (4): 28.3 degrees c, the rise in temperature was so sudden that the test was concluded 21 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 that the bearing retainer (ball retaining part) on the cartridge rear side was broken.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 due to the ingress of undesirable materials into the bearing.2) 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.3) in order to prevent a recurrence of the handpiece overheating, nakanishi took the following actions: 3.1) nakanishi reviewed the operation manual and reconfirmed the clarity and understandability of the instructions.3.2) nakanishi reported the above evaluation results to the dentist and reminded the dentist of the importance of pre-use checks and 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
• Manufacturer (Section G): NAKANISHI INC.; 700 shimohinata; kanuma-shi, tochigi-ken 322-8 666; JA 322-8666
• Manufacturer Contact: kenneth block ; 800 e campbell rd.; suite 202; richardson, TX 75081 ; 9724809554
• MDR Report Key: 7600472
• MDR Text Key: 111015965
• Report Number: 9611253-2018-00028
• 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: foreign,health professional,o
• Reporter Occupation: Other
• Type of Report: Initial,Followup
• Report Date: 07/03/2018

1 Device was Involved in the Event

1 Patient was Involved in the Event

• Is this an Adverse Event Report?: Yes
• Is this a Product Problem Report?: Yes
• Device Operator: Dentist
• Device Model Number: Z95L
• Device Catalogue Number: C1034
• Was Device Available for Evaluation?: Device Returned to Manufacturer
• Date Returned to Manufacturer: 05/30/2018
• Is the Reporter a Health Professional?: No
• Was the Report Sent to FDA?: No
• Initial Date Manufacturer Received: 05/25/2018
• Initial Date FDA Received: 06/14/2018
• Supplement Dates Manufacturer Received: 06/06/2018
• Supplement Dates FDA Received: 07/03/2018
• Was Device Evaluated by Manufacturer?: Yes
• Date Device Manufactured: 11/07/2012
• 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