Flashcards in Post and Core Deck (75):
What system is used to prepare parallel sided post-core preps and for what type of canal?
Straight, narrow, circular canals
What system is used to prepare tapered post-core preps and for what type of canal?
RelyX Drill system
Straight sided drills with step back technique
For tapering, ovoid canals
What steps should be taken for preparing a post-hole prior to placement of both direct and indirect post cores?
1. Take pre-op, evaluate legnth, shape, diameter of root canal
2. Place rubber dam
3. Access pulp chamber and canal
4. Use size 3 gates glidden bur or relyX universal bur (depending on parapost or relyX system). Set stopper at (measured tooth length - 5) mm
5. Enter canal and ream down this distance with bur slowly and continually rotating
6. Re-take radiograph to verify length of post adequate, leave 5mm root filling at apex
7. Complete canal prepartion according to whether post-hole will be tapered or parallel (increase bur size as appropriate. With larger burs go once in once out in a single motion rather than going up and down, and avoid forcing)
After preparation of a post-hole, how would you proceed with a direct anterior post-core?
1. Select appropriate post size corresponding to bur size used in hole preparation (same colour)
2. Try post in hole, check fit and adjust length as necessary
3. Remove post and Irrigate post hole with Milton's solution and dry with paper points
4. Clean post with alcohol swab and air dry
5. Mix RelyX Unicem cement, attach elongation tip and extrude cement into canal. Ensure cement starts at the bottom of the post hole and fills up the entire canal
6. Re-insert the post and clean off excess cement. Light cure for 40 seconds (if no light cure wait 5mins)
7. Remove the rubber stopper
7. Etch and Build CR core to ideal tooth shape for PBM
(DO NOT USE LENTULO SPIRAL TO SEND CEMENT DOWN POST HOLE BEFORE SEATING POST AS MAY SET BEFORE POST IS FINISHED SEATING)
After preparation of a post-hole, how would you proceed with an indirect post core?
1. Irrigate with Milton's solution and dry with paper points
2. Make a PBM crown prep on remaining tooth structure (Doing the PBM before doing the impression allows impression to be taken of both the prep and post hole at the same time, thus getting shape of entire base of final crown)
4. Place appropriate anti-rotation devices as indicated by tutor
5. Select smooth sided plastic impression post (size 1 brown or size 2 yellow) and try out (should seat to base of post hole without binding but should have some resistance)
6. Use hot lechron to cut/shorten impression post to tooth length + create flat retentive mushroom on top of post (super heat lechron and hold horizontally)
7. Use microbrush to lightly coat coronal 2/3 of post with PVS adhesive and allow 10 mins to dry
8. Select copper band that fits loosely around tooth, coat inside with PVS adhesive (in clinic would use impression tray)
9. Syrigine light body Honigum impression material onto mixing pad, use lentulo spiral at very slow speed to spin light body material down post hole to fill post hole.
10. Insert plastic impression post into canal to full depth, fit copper band around tooth, inject light body material into the band, allow to set (6 mins), carefully remove.
Never use serrrated plastic post to take impression: it will not withdraw
*Function of PVS adhesive is to glue post and copper band to impression material
What burs are found in the RelyX system? What are they used for?
-Universal bur: Remove gutta percha from canal
-Yellow coated drill: one size up from universal (0.7mm apical, 1.30mm coronal, 6% taper)
-Red coated: one size up from yellow (0.8mm apical, 1.60mm coronal, 8% taper)
-Blue coated: one size up from red (0.9mm apical, 1.90mm coronal, 10% taper)
*All lengths 20mm
What speed of the drill is recommended for removal of gutta percha from a canal using either the Universal RelyX bur or the gates glidden size 3?
1000-2000RPM in slow speed handpiece
Why should wire cutters never be used to cut a post?
-Posts are fibre reinforced
-Cutting with wire cutters (that are designed to compress until material reaches break point) causes post to split, thus reducing structural integrity
How long should the Unicem relyX capsule be mixed for? What is it used for?
-Contains cement for post
-10 seconds with Rotamix, if another mixing machine 15 seconds
Does the elongation tip go on the unicem capsule before or after mixing?
What is the issue with having a modulus of elasticity greater than dentine of the post?
-Risk root fracture as too stiff/resists being deformed
Should a serrated plastic post be used to take an impression of a post hole and why?
No, it will not withdraw
How do you do a posterior direct core (without post)?
Modification to Post Preparation Steps:
-Rather than leaving 5mm of gutta percha in canals, remove only the coronal 3-4mm of gutta percha (you’re not going to be able to pack resin or amalgam 12mm into the canal properly)
-No need to use relyX or Parapost drills, the gates glidden will be sufficient (as there is no need to prepare the canals to house a relyX or parapost post)
-Post-op radiograph optional (quite easy to guage if you’re down 3mm)
1. Assess the need for additional retention and add retentive features as needed
2. Build up core in amalgam or CR
Once an indirect post impression has been prepared, how do you construct a temporary post-crown?
1. Select crown former correct size + tooth
2. Select Parapost temporary anodized aluminium post size and try in tooth and adjust, fit temp crown former over top to assess height (trim with wire cutters). Roughen surface if necessary
3. Place post back in hole (having post in hole when placing temporary crown means that post gets attached to Protemp crown)
4. Discard first few mm then syringe Protemp into crown former
5. Place onto tooth and leave for 3mins to set
6. Remove crown former (by placing plastic underneath crown former and lifting it off (post should come out with temporary)
7. Trim excess
8. Remove celluloid crown former from temp crown
9. Smooth off margins and try in tooth to check if margins flush
10. Mix RelyX TempCem NE
11. Apply cement to post
12. Place on tooth and remove excess cement (3mins to set)
What is the size order for parapost drills?
(smallest to largest)
What is the size order for glates glidden burs?
1, 2, 3
Why is non-eugenol cement used?
-Eugenol Inhibit polymerisation reaction of resin
Is it easier to remove cement before or after setting?
Why can Panavia cement only set in the roots but not on the benchtop if uncured?
Oxygen inhibits set
What is a temporary post from the Parapost brand made of?
What are two types of Parapost permanent posts and what is the difference between the two?
-Stainless steel: shinier
Which canal is generally longest and straightest in a molar?
What size do gates glidden burs go up?
-Yellow, red, blue
Why must you wait the full 5 minutes for RelyX Unicem cement to cure for Titanium posts even after light curing?
*If using Titanium post, need to wait full 5 mins (unlike the RelyX fibre posts that can transmit light down, and cure apical cement, Titanium posts cant do this so said cement requires full 5 mins to set
How is sonic fill used?
1. Sonic energy modifies stabilising particles thus drastically decreasing viscosity and allowing for manipulation and adaptation
2. Once sonic energy removed stabilising particles re-stabilise and viscosity increases to allow moulding and shaping
What is the volumetric shrinkage of Sonic Fill? Who conducted the study?
Dr J.Y Thompson
Was there a signficant difference in marginal integrity and cusp displacement for Sonic Fill restorations compared to other restorations? Dr Roland Frankenberger
Are there any difference of sonic fill vs other materials in terms of:
Dr. Carlos Munoz
-Micro + marginal: No
-Voids: fewer in sonic
What is the fracture toughness and flexural strength of sonic fill? Dr Jeff Thompson
Fracture: 2 MPa . m^1/2
Flexutral: 190 MPa
Was there a significant difference in longevity between sonic fill and Premise over 24 months? Drs Marc Geissberger and Parag Kachalia
What was the success rate of sonic fill vs Herculite ultra success rate? (Frankenberger R, Schulz M, Roggendorf MJ, Holl S, Geislingen et al.
In study by Willashausen, Fink, Earnst et al.) were the results similar in sonic fill vs premise for:
Which did authors conclude to be superior technique?
No difference but authors concluded sonic fill to be superior technique
What are the advantages of fibre posts such as RelyX?
-Root fractures reduced (due to dentine like elastic properties)
-Meets aesethetic demand of all ceramic due to translucent properties
-Easier to remove from hole if endodontic treatment needs to be redone
What are the disadvantages of RelyX fibre posts? How are they overcome?
-Require adhesive bonding of post (etch, primer bond) which is really hard to do in a canal; overcome by using RelyX unicem which allows usage without
What are relyX fibre posts composed of?
-Glass fibres arranged parallel and embedded in a composite resin matrix. Glass fibres distributed evenely
How many mastication cycles are RelyX posts said to survive?
What three methods does RelyX Unicem bond with RelyX fibres posts?
(Microporosities in RelyX posts from manufacturing)
-Covalent bonds/chemical bonds
(between Resin matrix of post and resin in cement)
(Between post and cement molecules)
What is the approximate bond strength between RelyX Unicem and RelyX fibre posts without pre-treatment?
What is the bond strenght between RelyX unicem and dentine?
What material is Luxacore based on?
-Used for core build ups
Luxacore releases fluoride
What is Luxacore composed of?
-Barium glass (69%)
Bis-GMA based matrix of dental resins
What is the working time of Luxacore?
1 minute 30 seconds
What is hte setting time of luxacore?
4mm: 40 s
self cure: 5minutes
What is the compressive strength of luxacore?
What is the transverse strength of luxacore?
What is the diametrical tensile strength of luxacore?
What is the water sorption of luxacore?
What is the function of the post, core and coronal restoration?
-Post: retain core; distribute stress along root
-Core: replace lost coronal structure; retention, foundation for coronal restoration, interim restoration
-Coronal restoration: restore function, aesthetics and resistance
What factors should be taken account into deciding whether or not to do a post?
Role of tooth
What are the different ways of classifying posts? What are in each category?
-Post metallic; core metallic
-Post metallic; core non metallic
-Post non-metallic; core non-metallic
-One piece post-core crown (historical)
-Attached post core; separate crown
-Post, core, crown all separate
Method of construction
-Custom made cast metal (indirect)
-Custom made fibre-reincforced composite (direct)
What are the classifications of pre-fabricated posts?
-Parallel (more retentive, distribute load more passively, less conservative)
-Tapered (conform better to canal, venting reduces hydrostatic pressure in cementation, may cause wedging action of root)
-Stepped (parallel coronal, tapered apical)
-Serrated (most preferred and recommended)
-Smooth (least retentive)
-Threaded (like a screw, most retentive but increased risk of fracture)
Mechanism of retention
-Active (engage dentine in root canal)
-Passive (do not engage dentine)
What are the ideal characteristics of posts?
Aesthetics (won't interfere with full ceramic crowns), radiopaque, biocompatible, functional strength (compressive + flexural)
Large enough to resist bending + give retention
Not too wide else root fracture
Recommended width 1/3 of root diameter
(metallic posts come thinner due to higher rigidity)
-2/3 the length of the canal
-Should be equal to crown height of decoronated tooth
-If tooth periodontally affected then post should extend to one half the length that is supported by bone
-Withstand functional stress
Can bond to resin cements
Elastic modulus similar to dentine
What are the desirable properties of a core?
Aesthetics (won't interfere with full ceramic crowns), radiopaque, biocompatible, high strength
-Ability to bond with tooth and dowel
-Ease of manipulation
-Short setting time
What are the indications of indirect cast metal post core systems?
-Over flared root canal
-Elliptical root canal
-Avoid core displacement
What is the ferrule effect?
-Circumferential collar of dentine apical to core assists crown retention and provides resistance to splitting of root (both of these is done by preventing tipping by providing extra length to walls of core)
-1.5-2mm of ferrule desirable
Blood must be removed from the impression surface while constructing indirect posts
What is the role of a temorary post and crown?
-Protect tooth structure
-Prevent tooth drift
HOw can post retained restorations fail?
Loss of retention
Where do the highest compressive and tensile forces occur?
How much post length should extrude from the canal to give adequate core retention?
How do you remove an alloy post?
-Create space around post with fine diamond
Does a post strength endontically treated teeth?
What are the best canals to put posts in in molars?
-Widest and straightest
-Usually distal in lowers and palatal in uppers
What factors should be considered in avoiding perforation on a premolar root?
-Less tooth substance
Smaller pulp chambers
Proximal root invaginations
Mandibular 4 inclined lingually relative to root
What is the success rate of custom fabricated cast gold post and cores? What are some of their disadvantages?
90.6% at 6 years.
-Aesthetics, overcome by using PBM post and core to mask shade
-Two visits and lab fabrication required, overcome by prefabricated post
What is an issue with stainless steel posts?
What is an issue with brass posts?
What is an issue with pure titanium posts? What are the advantages?
-Lower physical properties (compressive and flexural strength)
-Low radiopacity: looks similar to gutta percha
-Least corrosive and most biocompatible
What are the + and - of ceramic posts?
-High flexural stregnth
-High fracture toughness
Poor resin bonding capability to dentine
What is the failure rate of fibre reinforced posts over 1-6 years?
What are the + and - of metallic cores (gold and amalgam)?
Basic comparisons: strength, aesthetic, setting time, solubility, condensing
-Co efficient of thermal expansion similar to tooth substance
-Easy to condense
-Require an additional appointment (gold need casting, amalgam extended set)
-Mercury concern for amalgam in patients
What are the + and - of CR cores?
Basic comparisons: strength, aesthetic, setting time, solubility, condensing
-Rapid setting, can prep at same appointment
-Hydroscopic expansion (water adsorption)
-Technique sensitive: voids as can not be condensed like amalgam
-Incompatible with ZOE in RCT sealers-->incomplete cure but usually does not affect bond if dentine is properly cleaned along canal and exterior surface
Why should GIC be avoided as a core?
-Low physical properties (tensile, compressive, fracture resistance, modulus of elasticity
-Poor bonding to dentine and enamel
-High solubility + moisture sensitive
-If RMGIC water absorption may fracture all ceramic crowns
However advantage in anticariogenic propeties