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Model Number SGS-E2S |
Device Problem
Overheating of Device (1437)
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Patient Problems
Burn(s) (1757); Partial thickness (Second Degree) Burn (2694)
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Event Date 08/02/2021 |
Event Type
Injury
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Manufacturer Narrative
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The dentist refused to disclose the patient's weight.The same adverse event in this report has been reported to the fda separately by the distributor, nsk america corporation, under report number 1422375-2021-00021.
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Event Description
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On august 20, 2021, nakanishi became aware of a handpiece overheating through a complaint input into the complaint database by a distributor (nsk america).Details are as follows: the event occurred on (b)(6) 2021.The dentist was performing a 3rd molar extraction on the patient's teeth #1, 16, 17, and 32 using the sgs-e2s handpiece (serial no.(b)(4)).During the procedure, the dentist observed a second degree burn (blistering) on the patient's lower lip.The patient is reported to be healing normally without the need for additional medical treatment at this time.According to the dentist, the dentist did not note any heat from the device during the procedure, and the device has been removed from use at the practice since the event.
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Manufacturer Narrative
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Upon receiving the device involved in the mdr event from the distributor, nakanishi conducted a failure analysis of the returned device, which included measuring the operating temperature of the device [report no.(b)(4)].These activities are described in more detail below.Methodology used: a) nakanishi examined the device history record and the repair history for the subject sgs-e2s device [serial no.A(b)(6)].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 (b)(4), which is the maximum rpm for the motor that drives the handpiece ((b)(4) for the handpiece), with water spray, and measured the exothermic response.B.3) nakanishi measured the temperature rise of the returned handpiece set at (b)(4) (motor revolution (b)(4)).Nakanishi observed an abnormal temperature rise at test points (1) and (2) a few seconds into the test.Temperature measurements 110 seconds after the start of the test were as follows: - test point (1): 94.9 degrees c.- test point (2): 61.0 degrees c.- test point (3): 40.0 degrees c.- test point (4): 43.6 degrees c.The increase in temperature was so sudden that the test was concluded 110 seconds into the planned 5-minute evaluation period.Identification of the specific failure mode(s) and/or mechanism(s) of the associated device components was conducted as follows: a) nakanishi disassembled the handpiece and performed a visual inspection of the internal parts.Nakanishi observed debris on the internal parts; the bearing especially was heavily soiled and abraded.B) nakanishi took photographs of all the disassembled parts and kept them in investigation report no.(b)(4).Conclusions reached based on the investigation and analysis results: a) nakanishi determined that the cause of the overheating of the returned device was abnormal resistance during rotation due to the damaged bearing.Nakanishi considers the possibility from many years of experience that the cause of the damaged bearing was the ingress of undesirable materials into the bearing, leading to abrasion.B) a lack of maintenance caused the accumulation of debris on the internal parts, which caused debris ingress into the bearing during rotation.This contributed to the handpiece overheating.C) in order to prevent a recurrence of the handpiece overheating, nakanishi took the following actions: c.1) nakanishi reviewed the operation manual and reconfirmed the clarity and understandability of the instructions.C.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.
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Search Alerts/Recalls
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