Investigating the steam sterilization of dental handpieces

Winter, Sandra (2016) Investigating the steam sterilization of dental handpieces. PhD thesis, University of Glasgow.

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Dental handpieces are used in a wide variety of dental treatment and oral surgery. During patient treatment handpieces becom contaminated with patient material. Due to the design and function of the dental handpieces, internal contamination of handpiece components frequently occurs during use, raising the risk of iatrogenic infection. Dental handpiece lumens represent a challenge for both cleaning and steam sterilization due to limited access. Manufacturers of handpieces and benchtop sterilizers as well as international standards and several guidelines recommend use of a vacuum steam sterilization process for lumen devices; however, non-vacuum is used in many UK dental practices.
Therefore the aim of this thesis was to investigate if benchtop steam sterilization processes commonly used in dental practice are appropriate for sterilizing dental handpieces. Critical variables affecting the outcome of steam sterilization, such as pre-cleaning and lubrication were assessed.
In order to investigate the above stated aim, four research questions were formulated:
1- Investigating steam penetration into dental handpieces and lumens in general (chapter 4), which was approached using thermometric measurements, chemical and biological indicators were used in different handpiece types (high-speed turbines, slow-speed motors, surgical handpieces) and process challenge devices using non-vacuum and vacuum sterilization cycles in a laboratory setting (chapter 4) and in general dental practices (chapter 6).
2- Investigating the effect of pre-cleaning dental handpieces, contaminated with different test soils from the standards or clinical contamination after patient treatment using a washer-disinfector or a handpiece cleaner-lubricator, which was assessed using the o-phtalaldehyde and G-box method (chapter 7).
3- Investigating the effect of handpiece lubricating oil on microbial inactivation by altering different parameters during a steam sterilization process using a BIER/CIER vessel in St. Paul (MN, US) (chapter 5).
4- Investigating the effect of different humidity levels on chemical and biological indicators using a BIER/CIER vessel in Neuss (Germany) (chapters 3).
Thermometric measurements as well as assessment of chemical and biological indicators suggest that not all handpiece types can successfully be sterilized in all non-vacuum benchtop sterilizers. Especially the surgical handpiece appears to be difficult to sterilize. All non-vacuum sterilizers in general dental practice failed to sterilize handpieces. The comparison of the cleaning efficacy of a washer-disinfector and a handpiece cleaner-lubricator showed that a washer-disinfector is more efficient in cleaning the outside of a handpiece. Handpiece lubrication oil appears to impair steam penetration into handpiece lumens. Pre-conditioning in high humidity (90% RH) causes chemical indicators to perform a colour change and indicate successful sterilization quicker than ones pre-conditioned in low humidity (14% RH), which suggests that it is moisture rather than saturated steam that causes chemical indicators to indicate pass conditions.
Non-vacuum sterilization benchtop sterilizers are not adequate for sterilizing dental handpieces. A vacuum process is highly recommended in the interest of patient and staff safety. Chemical and biological indicators are not necessarily reliable and results should be interpreted with care.

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Keywords: Decontamination, sterilization, dental handpieces, dental instruments, protein detection, microbiology
Subjects: Q Science > Q Science (General)
Q Science > QR Microbiology
Colleges/Schools: College of Medical Veterinary and Life Sciences > School of Infection & Immunity
Supervisor's Name: Smith, Prof. Andrew
Date of Award: 2016
Depositing User: Sandra Winter
Unique ID: glathesis:2016-7057
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 01 Feb 2016 16:02
Last Modified: 12 Feb 2016 13:22

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