Disinfection Flashcards
Q99 : What are the advantages of coronal pre-flaring?
Explanation:
a) Eliminates interferences and eases instrumentation (Leeb, JOE - 1986)
b) Better tactile sensation of the root canal space (Stabholz et al JOE - 1995)
c) Increase efficacy of EAL (Ibarrola et al, JOE, 1999)
d) Less stresses on rotary files and thus minimizes the chances of instrument separation (Roland et al JOE - 2002)
Q100 : Are there any antagonistic interactions between NaoCl and EDTA?
Explanation:
NaOCI can lose the free available chlorine when in contact with chelators such as EDTA or citric acid. This can result in reduction in the tissue dissolution capability and the antimicrobial activity of NaOCI. (Rossi-Fedele et al, JOE 2012)
Q101: What are the limitations of Ca(OH)2 as an intra-canal medicament?
Explanation:
It cannot render the canal bacteria free (Law & Messer, JOE 2004)
A number of micro-organisms are resistant to Ca(OH)2 such as:
a) E. faecalis (Distel et al, JOE - 2002)
b) Candida (Waltimo et al, IEJ - 1999)
Q103 : Describe the mechanism of action of NaOCI irrigant?
NaOCl has an antibacterial effect and tissue dissolving ability. When the hypochlorous acid (a substance presents in NaOCI) comes into contact with organic tissue, it will release chlorine that will
1- inhibit bacterial cells enzymatic activity
2-binds to protein amino group and forms chloramines that will inhibit the bacterial cellular metabolism
3- chloramines will lead to degradation and hydrolysis of amino acids
4-also the high pH of NaOCI will interfere with cytoplasmic membrane integrity
(Estrela et al, Braz Dent J, 2002)
Q104 : Should endodontic treatment be performed in single or multiple visits with Ca(OH)2 as an intra canal medication?
This is a controversial topic.
There is enough evidence that the use of Ca(OH)2 would result in reduction of the level of intra-canal bacteria within the canal and can contribute to healing (Katebzadeh et al, JOE- 1999), (Katebzadeh et al, IEJ - 2000), (Shuping et al, JOE 2000). McGurkin Smith et al, JOE- 2005)
Sjogren et al (IEJ - 1991) showed that the 7-day Ca(OH)2 dressing efficiently eliminated bacteria which survived chemo mechanical instrumentation of the canal. They also showed that achieving proper root canal disinfection cannot be achieved in one visit and without the support of an intra canal medication (Sjogren et al, 1997)
On the other hand, In a systematic review & meta-analysis of the literature by Sathorn et al (IEJ, 2005) the difference in healing rate between these two treatment regimens was not statistically significant”
In an overview of systematic reviews by Moreira et al (JOE 2017) Single and multiple visits showed similar repair or success rates regardless of the pulp or periapical conditions. There was, however, a slight positive trend toward a decreased incidence of postoperative complications and a higher effectiveness and efficiency in single treatment sessions
The overall consensus is the Ca(OH)2 will assist reducing the level of intra canal bacteria inside the root canal space but it may not necessarily have an impact on the outcome of endodontic treatment.
Q105 : What are the disadvantages of long-term application of intra-canal medicaments?
Andreasen et al. (Endod Traumatol - 2002) showed that long-term application of Ca(OH)2 as a root canal dressing may increase risk of root fracture. Similar findings were concluded by Yassen et al (IEJ - 2013) who showed that 3-months application of TAP, DAP or Ca(OH)2 paste medicaments significantly reduced the root fracture resistance of extracted teeth compared to a one week application.
In addition, from a clinical perspective, maintaining the tooth on a long-term intra-canal medicament means that the placement of the final restoration will be delayed. In a recent study by Pratt et al (JOE - 2016), delaying placement of full coverage restoration (crown) on RCT teeth by 4 months can result in 3 times more extraction compared to teeth restored within 4 months.
Q106 : Why it is not recommended to mix NaOCI and CHX irrigation during root canal instrumentation ?
According to Basrani et al. (JOE 2007) NaOCI when mixed with CHX produces PCA (para-chloroaniline) in an amount directly related to NaOCl concentration which is carcinogenic.
The reaction between NaOCl and CHX coats the canal surface and occludes the dentinal tubules in the coronal and middle thirds of the canal (Bui et al. JOE 2008)
Q107 : What is the composition of Qmix? and is it an effective irrigant?
Qmix is a combination of smear layer removal (EDTA) and antibacterial (CHX + detergent). Unlike regular CHX, Qmix does not interact with NaOCI and it has been recommended as a final rinse following NaOCl.
Stoijicic et al. (IEJ 2012) found QMIX and NaOCI were superior to CHX and MTAD under laboratory conditions in killing E faecalis and plaque bacteria in planktonic and biofilm culture. Ability to remove smear layer by QMIX was comparable to EDTA
Later Wang et al. (JOE 2012) utilized Confocal Laser Scanning Microscopy (CLSM) for evaluation of biofilm disinfection. They found that Qmix was as effective as 6% NaOCl for antibacterial effects on 1-day old biofilm (“young”) but 6% NaOCI > QMix for 3-week-old biofilm.
Q108 : What does the term “vapor lock” means? and how to get over the “vapor lock” effect formed during irrigation?
Vapor lock is the entrapment of gases in the canal during irrigation preventing irrigant from reaching the apical area (Tay et al, JOE - 2010)
How to get over the vapor lock:
1) Larger canal preparation
2) Negative apical pressure irrigation
3) Irrigation activation
Q109 : Will preheating NaOCl improves its antimicrobial effect?
Sirtes et al. (JOE 2005) showed that Preheating NaOCI solutions can improve their pulp tissue dissolution capacity and efficacy against E. faecalis. They showed that 1% solution at 60 C was significantly more effective than 5.25% solution at 20 C
This study, however, was performed in vitro. Clinically, preheating NaOCl may not be as effective, as maintaining a high temperature of the irrigant inside the canal (inside the body) for long time is not possible. The body can very rapidly reduces the temperature of the irrigant to the normal body temperature. If a high temperature is maintained for a long time, it may result in damage of the PDL and necrosis of the bone.
Therefore, the concept is valid but the clinical implications are not.
Q110 : What is the volume of EDTA needed to efficiently remove the smear layer after rotary instrumentation?
1 ml of EDTA was just as effective in removing the smear layer as 10 ml when left for 1 min inside the canal. (Crumpton et al, JOE - 2005)
Q111 : What is the advantage of using high conc of NaOCI irrigant during root canal treatment?
Gordon et al (JOE - 1981) showed that increasing the conc of NaOCI can improve the dissolution capacity for vital and necrotic pulp tissue.
Harrison & Hand (JOE - 1981) showed that dilution of 5.25% NaOCI inhibits its antibacterial property. They also showed that the presence of organic matter (such as pulp tissue) can reduce the antibacterial property of 5.25% NaOCI.
Other studies showed no difference in the antimicrobial properties of the different conc of NaOCI ranging from 1% to 5.25% (Baumgartner & Cuenin, JOE,1992), (Siqueira et al, JOE - 2000)
It should be noted that studies that showed no difference or similar effect between the different concentrations of NaOCI either used large volume of NaOCI or exposed the canal to NaOCI for a long time. These studies also sampled the canal from the main root canal space and did not examine the depth of penetration in the dentinal tubules.
Zou et al. (JOE - 2010) showed that increasing the Conc of NaOCI as well as longer exposure time will allow its deeper penetration into the dentinal tubules.
It appears to be useful to use a higher conc of NaOCI during cleaning and shaping to compensate for the limited contact time of NaOCI in the root canal space particularly at the apical area, since NaOCI only reaches the apical area towards the end of the mechanical preparation.
Q112 : Are rotary files more superior to hand-files in reducing the level of intra-canal bacteria?
No
Dalton et al. (JOE - 1998) showed that NiTi rotary and stainless-steel hand-files instrumentation techniques were not significantly different in their ability to reduce intra-canal bacteria. Rotary files, however, may result in faster mechanical instrumentation allowing more time for irrigation.
Q113 : Describe the composition of the smear layer?
The smear layer consists of bacteria, organic pulpal materials and inorganic dentinal debris that accumulates on the radicular canal wall during cleaning and shaping. This layer can block the dentinal tubules and may persist even following irrigation.
Peters & Barbakow (JOE - 2000) showed that even irrigation with EDTA and NaOCI will not result in complete removal of the smear layer from the canal.
Q114 : Can intra-canal medicaments reduce/prevent post-op pain?
That depends on the intra-canal medicament used.
Post-treatment pain is neither prevented nor relieved by medications such as Ca(OH)2 or IKI. (Maddox et al, JOE - 1977)
Intra-canal corticosteroids medicaments, however, can reduce post-op pain. Intra-canal medicaments containing corticosteroids such as Ledermix (Tetracycline + corticosteroid) has been shown to minimize the amount of post-op pain following root canal procedures in several studies. (Ehrmann et al, IEJ - 2003) (Negm, OOOOE - 2001)
