L19. Chemomechanical Disinfection Flashcards
What is the origin of periodontal disease?
Bacterial, fungal and viral - developed into biofilms
What are oral biofilms?
Complex communities of microorganisms, embedded within a complex ECM, that are adherent to the dentinal surface and resistant to changes/ attempt of removal
What are the clinical objectives of endodontic therapy?
- Remove canal contents;
- Eliminate infection.
What is chemomechanical disinfection?
- Mechanical processes to debride and shape the RCs;
- Supplemented by chemical means to enhance biofilm disruption.
What are Dr Herbert Schilder’s design objectives?
- Create continuously tapering funnel shape;
- Maintain apical foramen in original position;
- Keep apical opening as small as possible.
(these create space to allow irrigating solutions and medicaments to effectively eliminate micro-organisms)
What is the minimum size of master file usually recommended for apical preparation?
25 (30 for stainless steel files)
25: 0.25mm
30: 0.30mm
Why is a minimum apical file size important?
Adequate space preparation for irrigation
What are the two main key properties of an endodontic irrigant?
- Killing of biofilm microbes;
- Detachment of biofilm.
State some other ideal properties of an endodontic 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;
- Non-toxic to periapical tissue;
- Non-allergenic;
- Does not react with negative consequences with other dental materials;
- Does not weaken dentine.
What irrigant is typically used in endodontics?
Sodium hypochlorite (NaOCl)
With regards to laboratory studies, why is sodium hypochlorite typically the irrigant of choice?
Shows to be very effective at killing and dislodging the biofilm
What can NaOCl offer, that other irritants can’t?
Also dissolves organic remnants (necrotic pulp tissue), this helps to disrupt the smear layer
What component of NaOCl provides the antimicrobial activity?
Hypochlorous acid (HOCl)
[the buffer ion which predominates in acidic/ neutral environments]
What is the concentration range of NaOCl used in endodontics?
0.5-6%
What concentration of NaOCl is typically used at GDH&S?
3% (sweet spot - effective but less side effects)
Why does effective irrigation of a root canal system require a relatively large volume of NaOCl?
NaOCl quickly looses activity so must be replenished
Why is it important to use an endodontic needle to apply irrigant?
- To improve apical irrigation;
- So irrigant flows where we want it to go (not straight through constriction - this can cause nerve damage).
What are endoactivators and why are they used?
- Ultrasonic (?) instruments;
- Used in root canals to improve mechanical agitation of debris removal/ biofilm disruption, alongside irrigant.
What is an alternative to an endoactivator?
Mechanical agitation - use of GP cone to pump in and out
What problems are associated with use of NaOCl?
- Possible effect on dentine properties;
- Inability to remove smear layer by itself;
- Effect on organic material.
What effects can NaOCl have on dentine properties?
- Dissolve/ modify organic content;
- Modulus of elasticity and flexural strength can decrease with an increase in NaOCl (as penetration does).
What is the smear layer in endodontics?
- Formed during preparation;
- Organic pulpal material and inorganic dentinal debris;
- Packs into tubules;
- Interferes with disinfection;
- Prevents sealer penetration
What is used to remove the smear layer?
17% EDTA solution (1-min contact time required)
[EDTA is a chelating agent]
What other risks organic are there when using NaOCl in a dental setting?
- Fabrics (discolouration);
- Ophthalmic injuries (can lead to blindness);
- Tissue necrosis due to apical extrusion;
- Allergies;
- Can interact with other materials/ solutions used and produce cytotoxic/ carcinogenic byproducts.
