SingHealth has completed its investigations into the incident at the National Dental Centre Singapore (NDCS) where 72 packs of instruments which had undergone thermal washer disinfection but had not completed the final step of steam sterilisation, were used for patient treatment on 5 and 6 June 2017.

Following the incident, a full investigation was launched. It was overseen by the SingHealth Risk Oversight Committee, a committee of the SingHealth Board. A report of the findings and follow-up actions has been submitted to the Ministry of Health (MOH) on 30 June 2017.

The investigations identified human error as the cause of the incident. In addition, procedural weaknesses and a lack of vigilance of some staff involved had led to delays in escalation in incident management. The Committee has instituted measures to improve NDCS’ systems, processes and culture to prevent a recurrence. Specific measures have been taken to improve the competency of staff involved in the sterilisation and handling of instruments.

We apologise for the lapses, and have started on corrective actions for improvement.

Sequence of Events

On 5 June, an NDCS staff of the Central Sterile Supplies Department (CSSD) did not adhere to the established protocol to complete the final step of steam sterilisation of one batch of dental instruments (details of sterilisation process in Annex A). The affected batch of instruments was subsequently dispatched to the outpatient clinics on levels 2, 4 and 6 of the NDCS in the late afternoon of 5 June. The error was discovered by another NDCS staff at about that time. A recovery of the affected instruments was initiated after the supervisor was informed, but not all the affected instruments were retrieved. The manager of the CSSD was not informed.

On 6 June, prior to the start of clinic operations at 8am, the manager of the CSSD became aware of the incident when she noticed that the sterilisation records of one batch of instruments from the previous day was incomplete. Another recall of affected instruments was initiated.

At 4pm on 6 June, the issue was escalated to the senior management of NDCS. The Director of the NDCS immediately activated another round of recalls to ensure that all affected instruments were retrieved. Prior to the start of clinic hours on 7 June, all dental instruments were thoroughly checked and confirmed to have undergone the complete sterilisation process. Additional controls were also implemented to ensure the completeness of the sterilisation process.

It was assessed that among the 714 patients who had visited the outpatient clinics on Levels 2, 4 and 6 from the late afternoon of 5 June to the end of clinic hours on 6 June, up to 72 of them could have come in contact with the affected instruments(1). NDCS began contacting the patients on 10 June to inform them of the incident and reassure them of the extremely low risk of infection.

A detailed timeline of the incident is provided at Annex B.

Causes of the Lapse

The investigation committee assessed that the incident was a result of human error. In addition, procedural weaknesses and a lack of vigilance amongst some NDCS staff contributed to the delay in the escalation of the incident and the timely containment of the impact of the initial error.

The origin of the incident was an error made by an NDCS staff carrying out the sterilisation process. Other NDCS staff who were subsequently aware of the incident failed to adequately assess the potential impact of the incident, and to escalate the issue in a timely manner. As a result, while they had attempted recalls of the affected instruments, the full recall was not completed until the evening of 6 June, 24 hours after the error was first noticed.

At various points in the process from issuance of the instruments from the CSSD, through the receipt of the instruments in the clinics, and unpacking of instruments before use on patients, the error was not picked up even though sterilisation indicator strips attached to the packs of instruments had not changed colour(2). This reflects gaps in the level of vigilance on infection control and patient safety, and, in this particular context, instrument sterility.

In addition, there was no independent verification of the sterilisation process within CSSD. There was also a lack of clarity on the escalation and instrument recall processes.    

Corrective Actions

Following the incident, NDCS had implemented additional controls to ensure the completeness of the sterilisation process, so as to prevent any recurrence. Clear instructions were disseminated to remind all staff to check the sterility of all dental instruments prior to use.

NDCS has also carried an audit of all the sterilisation records in the six months prior to the incident.  The checks confirmed that sterilisation was documented to be completed in all other cases.

The Committee has set out the measures for implementation at NDCS. They fall into the following categories:

  • Enhance the standard operating procedures for sterilisation and use of dental instruments;
  • Refine the documentation and inventory accounting process for sterilisation and movement of dental instruments;
  • Strengthen the incident reporting and risk management frameworks; and
  • Conduct regular training and competency assessment of staff to ensure familiarity with the processes

SingHealth has appointed an Implementation Committee to ensure that NDCS implements and sustains the recommended corrective actions and recommendations for improvement. The SingHealth Incident Escalation Framework Committee has been tasked to review the existing incident escalation policy and provide guidance on when to trigger immediate escalation.

Disciplinary Actions

Disciplinary actions have been taken against four NDCS staff directly involved in this incident, including supervisors and senior NDCS management who have been found to have fallen short in their level of vigilance, and speed in escalation of incident management.  The disciplinary actions include warnings and financial penalties.

Mr Peter Seah, Chairman of SingHealth said, “Patient safety is our first priority. I would like to thank the committee for its work in reviewing the incident and making recommendations that will improve the robustness of our systems. We will ensure implementation of the corrective actions to prevent recurrence and work harder on strengthening a cluster-wide culture that places infection control and patient safety at the forefront of everything we do.”

(1) 72 packs of instruments were not retrieved through the recall. Each pack can only be used on 1 patient, but a patient can use more than 1 pack of instruments. 
(2) A change in the colour indicates a completion in the sterilisation process.




Annex A

Details of NDCS Instrument Sterilisation Process

1. At NDCS, the process of washing, disinfection and sterilisation of dental instruments is conducted in a Central Sterile Supplies Department (CSSD).  The functions of the CSSD are governed by work policies and standard operating procedures.

2. The steps involved in the sterilisation process are:

Step (i):   Contaminated instruments are thoroughly machine-washed to remove physical debris.

Step (ii):  As part of the machine washer-disinfector cycle, the instruments are then thermally disinfected at 90° for 5 minutes. This removes 99.99% of all organisms

Step (iii):   The disinfected instruments are then packed in a clean area, and sent into the steam steriliser at 121°C for 20 minutes. This destroys bacterial spores (Clostridium tetani and Clostridium perfringens).

- Clostridium perfringens is a gut bacteria and can occasionally be found in the mouth cavity. Disease caused by Clostridium perfringens is usually a result of food poisoning from unhygienic food preparations. Patients would typically recover within 1 week.

- Clostridium tetani causes tetanus, which is very rare in Singapore. Majority of Singaporeans are vaccinated for tetanus, and no screening tests are available. Symptoms include muscle stiffness and spasms. If patients do not show tetanus symptoms within 21 days, they are unlikely to have been infected.

3. The instruments are then loaded into trolleys, to be issued out to the SOC.

4. Verification checks are conducted at various stages of the sterilisation process and before the sterilized items are issued out and dispatched to the clinical areas for use.

5. On 5 June, Step (iii) of the sterilisation process was not activated.

Annex B

Timeline of NDCS Incident

Date / Time


5 June 2017, 12.30pm

  • A staff of the Central Sterile Supplies Department (CSSD) of the NDCS failed to complete the sterilisation process for one batch of dental instruments.

5 June 2017, 3.40pm

  • The affected batch of instruments was dispatched to Specialist Outpatient Clinics (SOCs) on levels 2, 4 and 6 of the NDCS.

5 June 2017, 4pm

  • Another CSSD staff noticed that the sterilisation indicator tapes had not changed colour on some packs of dental instruments[1], and alerted the first staff, as well as her immediate supervisor.
  • An immediate attempt was made to recall all affected instruments.

6 June 2017, 8am

  • The manager of the CSSD noticed that documentation from one batch of instruments was incomplete as she was reviewing the sterilisation records from the previous day.
  • She activated another attempt to recall all affected instruments.

6 June 2017, 4pm

  • The manager of the CSSD alerted the Chairperson of the Infection Control Committee.
  • Chairperson of the Infection Control Committee informed NDCS senior management including the Director of the NDCS.
  • Another recall was initiated to ensure that all affected instruments were retrieved.

7 June 2017, 8am, prior to start of clinic operations

  • All dental instruments were thoroughly checked and confirmed to have undergone the complete sterilisation process
  • Additional controls were implemented to ensure the completeness of the sterilisation process.
  • Preliminary investigations started

8 June 2017

  • SingHealth senior management were informed of the incident.

9 June 2017

  • SingHealth Rapid Response Resource team was activated.
  • MOH was informed of the incident.

10 June 2017

  • NDCS began contacting 714 patients who visited the SOCs on Levels 2, 4 and 6 from the later afternoon of 5 Jun to end of clinic hours on 6 Jun, to inform them of the incident, reassure them on the extremely low risk of infection, and address their concerns.

12 June 2017

  • NDCS notified the public of the incident after a majority of the patients had been informed.


[1] A change in colour indicates a completion in the sterilisation process.