L21. Obturation of the Cleaned and Shaped Root Canal Flashcards
What is the objective of RCT?
To provide and environment that allows healing of periradicular tissues so that the tooth is retained as a functional unit in the dental arch
What are the three components to RCT?
[outcome dependent on all three]
- Preparation;
- Disinfection;
- Obturation.
Why do we fill the root canal system?
To prevent the passage of microorganisms and fluid along the root canal and to fill the whole canal system (apical foramina, dentinal tubules and accessory canals)
Where should the preparation (and therefore WL) end?
At the apical constriction - at the junction of pulpal and periapical tissue, as close as possible to CDJ
How can you determine the WL?
- Electronic apex locator;
- Radiographically.
What are the potential problems of using the wrong WL (>2mm short of apex)?
Outcomes diminished - significant amount of bacteria left behind
What areas of the root canal system are bacteria/ inflammatory cells sometimes left behind?
- Accessory canals;
- Dentinal tubules.
Obturation is a 2-part system, what are these parts and what do each obturate?
- Core: bulk - sits in canal;
- Seal: penetrates tubules.
How is the timing of obturation usually determined?
- Signs;
- Symptoms;
- Pulp status;
- Periapical status;
- Difficulty;
- Patient management.
[often carried out in more than one tx visit: e.g. disinfect/ dress, pt sent away, obturation if symptoms have resolved]
What are the ideal properties of an obturation material?
- Biocompatibility;
- Dimensionally stable;
- Able to seal;
- Unaffected by tissue fluids;
- Insoluble;
- Non-supportive of bacterial growth;
- Radiopaque;
- Removal from the canal if retreatment needed.
What is gutta-percha (GP)?
- Most common core material;
- Semi-solid;
- Produced from juice of trees;
- Same polymer as natural rubber, isoprene;
- Trans-isomer of polyisoprene.
What are the constituents of GP?
- 20% GP;
- 65% zinc oxide (filler);
- 10% radiopacifiers;
- 5% plasticisers.
What are the three main types of obturation techniques?
- Cold lateral compaction;
- Size-matched cones;
- Thermal techniques (warm vertical compaction/ continuous wave/ carrier-based obturation).
What are the main advantages with cold lateral compaction?
- Most commonly taught;
- Low cost;
- Ability to control the length of the fill.
What are the main disadvantages of cold lateral compaction?
- Voids;
- Spreader tracts;
- Incomplete fusion of GP cones;
- Lack of surface adaption.
What are the main advantages of size-matched cones (~single point obturation)?
- Tight apical fit;
- Easier;
- Faster.
What are the main disadvantages of size-matched cones?
- Leaves very little space for accessory cones;
- More space as you come coronally; requires more sealer.
What’s the main advantage of thermal techniques?
Fills spaces (dentinal tubules/accessory canals) much better than cold lateral compaction
What’s the main disadvantage of thermal techniques?
Require good apical control to prevent extrusion past apex (into periapical area/ nerves/ maxillary sinus)
What technique is often used to obturate large, open apexes?
Bioceramic cements
[usually to act as an apical plug, then backfilled with GP]
What’s the main advantage of bioceramic cements?
They provide alkaline conditions which are osteoinductive (cementum/ bone growth alongside)
What are the functions of a sealer?
- Seal space between dentinal wall and core;
- Fills voids and irregularities in canal, lateral canals and between GP points used in lateral compaction;
- Lubricates during obturation.
What are the ideal properties of a sealer?
- Exhibits tackiness to provide good adhesion;
- Establishes a hermetic seal;
- Radiopacity;
- Easily mixed;
- No shrinkage on setting;
- Non-staining;
- Bacteriostatic or does not encourage growth;
- Slow set;
- Insoluble in tissue fluids;
- Tissue tolerant;
- Soluble on retreatment.
What are the four main types of sealer?
- Zinc oxide eugenol based;
- Glass ionomer sealers;
- Resin sealers;
- Calcium silicate sealers.
What are the main advantages of zinc oxide eugenol based sealers?
- Effective antimicrobial;
- Cytoprotection;
- Resin acids affect lipids in cell membranes (antimicrobial);
- Although toxic, may overall be beneficial with longlasting antimicrobial effect combined with cytoprotection.
What are the main disadvantages of zinc oxide eugenol based sealers?
- Resin acids affect lipids in cell membranes (cytotoxic);
- Free eugenol which remains can act as an irritant;
- Lose volume with time due to dissolution (but resins can modify this);
- i.e. lacks long-term stability and apical seal can breakdown.
What is the main advantage of glass ionomer sealers?
Good dentine bonding properties
What are the main disadvantages of glass ionomer sealers?
- Minimal antimicrobial activity;
- Greater solubility (lacks long-term stability);
- Removal upon retreatment is difficult;
- Little clinical data to support use.
What are the main advantages of resin sealers?
- Long history of use;
- Paste-paste mixing;
- Slow-setting (8hrs);
- Good sealing ability;
- Good flow;
- Initial toxicity declines after 24 hours;
- Hydrophilic;
- Good penetration into tubules;
- Biocompatible;
- Good radio-opacity.
What are the main advantages of calcium silicate sealers?
- High pH during initial 24 hour setting (antimicrobial);
- Hydrophilic;
- Enhanced biocompatibility;
- Does not shrink on setting;
- Non-resorbable;
- Excellent sealing ability;
- Easy to use (no mixing).
What’s the main disadvantage of calcium silicate sealers?
Quick-set (3-4hrs), requires moisture
What type of sealer is used in GDH&S?
Resin - AH26
What is the choice of sealer dependent on?
Technique being used e.g. can’t use zinc oxide eugenol sealer with heating GP (not compatible), can use Epoxy/ AH plus
After obturation, how should the quality of filling be checked?
By radiograph
What factors do you check on an obturated root canal, on a radiograph?
- Root apex with 2-3mm of the periapical region clearly identifiable (length);
- Canal should be filled completely (unless space is needed for a post);
- No space between canal filling and canal wall should be seen;
- There should be no canal space visible beyond the end-point of the root canal filling;
- Taper;
- Density.
What materials are used for a primary seal, before the coronal restoration?
- Vitrebond;
- RMGI;
- RIM (?).
Is the apical or coronal seal more important?
Both need to be as good as each other for best outcome
At what level of the tooth should obturation finish and why is this important?
- At orifice, or just below;
- GP rapidly becomes infected if directly exposed to oral bacteria;
- ZnO/ eugenol are cytotoxic and form effective antibacterial barrier.
[make sure finished surface is clear of sealer and GP, using alcohol, as will ensure best application of primary seal/ restoration]
What is regenerative endodontics?
- At research level;
- Endodontic treatment that replaces damaged structures like pulp/ dentine by regeneration.
What is important to consider (as an individual) for performing routine endodontic treatment?
- One or two techniques/ materials, depending on case;
- Keep it simple;
- Respect biological principles;
- Disinfection and irrigation is key (no filling material or technique can compensate for inadequacy here).
