chemomechanical disinfection Flashcards
what is a biofilm
- bacteria and fungi develop into biofilm
- complex communities adhering to dentinal surfaces embedded in a matrix
what is biofilm resistance
- antimicrobial may fail to penetrate beyond the surface layers of the biofilm
- antimicrobials Amy be trapped and destroyed by enzymes
- antimicrobials may not be active against non-growing microorganisms
- expression of biofilm-specific resistance genes
- stress response to hostile environmental conditions
- protective environment where elaboration to evade attempts to eradicate them
what are the clinical objectives of endodontic therapy
- removing canal contents
- eliminating infection
how can root canal make end hard
- very complex
- all complexities enhance the ability of the bacteria and the fungi to evade our attempts to eradicate them
what is chemomechanical disinfection
- employ mechanical means to deride and shape canal and supplement this with chemical means in order to enhance biofilm destruction
what are the design objectives of endo treatment
- create a continuously tapering funnel shape
- maintain apical foramen in original position
- keep apical opening as small as possible
what does mechanical preparation do
- creates space to allow irrigating solutions and medicaments to move effectively eliminate micro-organisms from the root canal system
what are the stages in mechanical preparation
- preparation of tooth
- access cavity preparation
- creating a straight-line access
- initial negotiation
- coronal flaring
- working length determination
- apical preparation
why do we start coronally
- eradicate the most significant infected parts of root canal surface coronally first then move apically where there is less infected material
- as instrument goes deeper it is less likely to carry with it infective material down
apical preparation size?
- determined by initial size of root canal apex
- passive exploration known as gauging
- apical preparation controversial
- usually at leat ISO size 25 to allow adequate irrigation
what are the ideal properties of an irrigant
- low cost
- washing action
- reduction of friction
- improving cutting of dentine by the instruments
- temperature control
- dissolution of organic and inorganic matter
- good penetration within the root canal system
- killing of planktonic microbes
- killing of biofilm microbes
- detachment of biofilm
- non-toxic to periodical tissues
- non-allergenic
- does not react with negative consequences with other dental materials
- does not weaken dentine
what is used as an irrigant
- sodium hypochlorite = one of most successful
- Chlorhexidine used but does not give a complete kill of bugs
how does NaOCl work
- ionises in water into Na+ and the hypochlorite ion OCl-
- establishes equilibrium with hypochlorite acid
- at acid/neutral HOCl predominates
- at pH 9 or above HOCl- predominates
why do we use NaOCl
- potent antimicrobial activity
- dissolved pulp remnant and collagen
- only root canal irrigant that dissolves necrotic and vital tissue
- helps disrupt smear layer by acting on organic component
what factors are important for NaOCl function
- concentration
- volume
- contact
- mechanical agitation
- exchange
what concentration of NaOCl is used
- used between 0.5-6%
- 0.5% not very active against organic tissue but 6% very active
- need to find a sweet spot between them
- many use 5%
- need good anti microbial activity and organic activity
what volume of NaOCl should be used
- sufficient volume
- becomes inactive very quickly
- need to replenish it
how long should NaOCl be in canal
- long enough to have an effect
- longer it is in canal the more likely to remove tissue
what things can help get irrigant to where we want it
- radio-opaque contrast media
- real-time imagine of bioluminescent bacteria
- thermal image analysis
- computational fluid dynamic
- stained dentine and NaOCl
- digital subtraction
- 3D mapping with microCT
what needles are best for irrigation
- use a syringe in needle system
- use safe needles so side vented or shaped to prevent outpouring ahead of needle
- but then don’t get irrigant at the apex as well
what is the problem with straight cut or oblique cut needles
- get force of irrigant ahead of needle which could cause it to go through apex and damage the soft tissue
- but it does get to the apex
what is mechanical agitation
- either use a sonic device or an ultrasonic device where we create fluid flow and exchange of irrigant
- use it because syringe irrigation alone is not effective enough
what is used for mechanic agitation
- endoactivator
- manual dynamic irrigation
what is an endoactivator
- used for mechanical agitation
- sonic device
- fibre tips that vibrate
- agitates solution and gets debris removal and biofilm destruction
what is manual dynamic irrigation
- used for mechanical agitation
- use in DH
- place GP point in Canale and pump irrigant in and out
what are some problems with NaOCl
- possible effect on dentine properties
- inability o remove smear layer itself
- effect on organic material
how does NaOCl affect dentine
- will dissolve organic tissue so will modify or dissolve organic content in dentine
- penetration of NaOCl into dentine
- root structure is thin so in some parts, a significant portion of dentine could be structurally altered
what is a smear layer
- formed during preparation
- organic pulpal material and inorganic dentinal debris
- superficial 1-5µm with packing into tubules
- smear layer limits disinfection of tubules
- prevents sealer penetration
what can be used along with NaOCl to remove smear layer
- 17% EDTA
- 10% citric acid
- MTAD
- sonic and ultrasonic irrigation
how long must EDTA be applied for
- 1 minutes
why can’t EDTA and NaOCl both be present in root canal at same time
- dentine is made more susceptible to NaOCl is used with EDTA
- it is a chelating agent so captures organic content and exposes collagen which can then be acted on by NaOCl
how do you use NaOCl and EDTA
- withdraw or aspirate one irrigant dry then use the other and withdraw, aspirate and dry
- some say use sterile water between irrigants
what are some NaOCl complications
- discolouration of fabrics
- ophthalmic injuries = need eye protection
- apical extrusion leading to tissue necrosis = need to keep in in canal and not use too much pressure
- allergic reactions
how does Chlorhexidine work
- the positively charged Chlorhexidine molecule is attracted to the negatively charged phospholipid in the cell wall
- Chlorhexidine binds to the cell wall causing it to rupture
- the rupturing of the cell wall causes fluid to lead leading to lysis and cell death
is Chlorhexidine good as an irrigant
- somewhat active against biofilm but unable to disrupt them
- well proven track record as antimicrobial
- poor choice as irrigant
- biocompatibility considered acceptable
- risk of anaphylactic reaction
how does Chlorhexidine react with NaOCl
- forms para-chlroaniline
- brown substance
- cytotoxic and carcinogenic
what is the proposed cleaning and shaping or canal
- once canal preparation is complete, the canal should be finally irrigated with
= 3% NaOCl throughout instrumentation and at leat 30ml after complete with MDI at least 10 minutes prior to obturation
= 17% EDTA for 1-minute penultimate rinse
= NaOCl final rinse to ensure adequate activity - dry canal using absorbent paper points between irrigants
- won’t penetrate until complete penetration
