restoration of endodontically treated teeth

lecture given 9/10/2026

accurate diagnosis and treatment planning (before/after) root canal therapy are critical

before duh

is the tooth restorable or should it be restored?

is it periodontally sound?

what is the condition of the adjacent teeth?

is the tooth an abutment for a single crown, FPD, or RPD?

what are the restorative options for endodontically treated teeth?

crown (full coverage restoration)

onlay (partial coverage restoration)

direct restoration

what factors should be considered for the restoration of endodontically treated teeth?

tooth structure loss- the % of extraction for teeth with less than 29.5% of remaining coronal tooth structure was 3x higher compared to that of teeth with greater than 29.5% residual tooth structure

terminal or nonterminal tooth and number of neighboring contacts

presnce of cracks

occlusal factors

how does terminal or nonterminal tooth and number of neighboring contacts impact the consideration for the restoration of endodontically treated teeth?

teeth with two remaining proximal contacts had superior survival to those with only one

how does presence of cracks impact the consideration for the restoration of endodontically treated teeth?

96% survival, over a 2-4 year period, for crowned root filled teeth with cracks extending to the level of the canal orifice and up to 5mm beyond

how does coronal coverage impact success rate?

extremely high failure rate for posterior pulpless teeth when these teeth lacked a restoration that covered the cusps

a significantly improved success rate for pulpless teeth that were crowned

10 yr retrospective study- teeth restored with crowns had a higher estimated survival rate (91%) when compared with those restored with direct restorations (76%)

what helps to dissipate the occlusal forces in dentine?

the free water contained within the dentinal tubules and matrix

the effects of dehydration have been suggested as a possible contributing factor for the development of vertical root fractures

what are the success rates for pulpless molars without coronal coverage?

1 yr- 96%

2 yr- 88%

5 yr- 36%

what is the purpose of a core?

primarily to replace missing coronal tooth structure sufficiently to provide adequate retention and resistance for the crown that will eventually restore the function and the aesthetics of the tooth in treatment

what is the purpose of a post?

there is inadequate remaining coronal tooth structure to retain a core for an artificial crown

according to retrospective studies, placement didn’t increase resistance to fracture or dislodgement of the crown, amount of tooth structure dictates necessity- ONLY USE IF IT IS INDICATED

how can you increase the probability of success of pulpless teeth restored with posts and cores?

apical seal

proper length of the post

ferrule effect

ferrule

parallel walls of dentin extending coronally from the crown margin

after being encircled by a crown provides a protective effect by reducing stresses within a tooth

there must be at least ______mm vertical heigh and ____mm of dentin thickness, ____ degrees around the tooth to get true ferrule effect

>1.5mm

1mm

360

ferrule reduces the potential for…

root fracture

post fracture

post and core dislodgement

failure of cement seal of artificial crown

what clinical studies back up ferrule?

all post fractures showed a similar pattern of a lack of ferrule effect of the metal collar at the crown margin area and a sharp interface between post and core

significantly increased fracture resistance with an increase in ferrule thickness >1.5mm

the ferrule effect should have a minimum thickness of 2mm

residual walls should also be a 2mm thickness

how can you increase ferrule?

crown lengthening, forced eruption, subgingival prep

how does the length of the post affect success rates?

longer posts = higher success rates

when length of the post = the length of the crown → 2.5% failure rate

when the post was ¼ the length of the crown → 25% failure rate

10 fold increase!

posts associated with vertically fractured endodontically treated teeth- 2/3 of them were the result of extremely short, terminating in the cervical 1/3 of roots

peak shear stresses increased substantially as post length decreased

after thermomechanical loading, specimens restored with a 3mm post length yielded significantly lower fracture values than with a post inserted 6mm

if the crown is double the length of the post…

the force of the crown is doubled in the root

if the crown to post ratio is 1:1…

the force of the crown on the root is equal

if the post is ¼ the length of the crown…

the force is multiplied by a factor of 4

higher chance of complications with (shorter/longer) posts

shorter

provided that the post lengths were equal to the length of the clinical crown, the succcess rate was (low/high)

high (96%)

when the radiographic width of the post exceeded ½ of the width of the root, the success was much (higher/lower)

lower

tapered posts showed _______ between the CEJ and the apex vs to parallel sided posts where the stresses were ___________

equal stress distribution

concentrated apically

apical seal

at least 4 to 5mm of apical gutta percha must be retained in order to avoid reinfection of the periapical region

what are the types of post and core?

cast post and core- direct or indirect technique

prefabricated- metal, fiber-reinforced composite, all ceramic

what are the advantages of cast post and core?

they are custom fit to the root configuration

are adaptable to large irregularly shaped canals and orifices

what are the disadvantages of cast post and core?

expensive

requires two appointments

temporization between appts is more difficult

may require the removal of additional coronal tooth structure

zinc phosphate

liquid is phosophoric acid/powder-zinc oxide

advantage- long history of success, inexpensive, long working time, reaches 75% of strength in 1 hr and brittle hard within 10 min

disadvantages- soluble in oral fluids, bond is mechanical

zinc polycarboxylate

liquid is polyacrylic acid/powder zinc oxide

advantages- chemical bond (weak), inexpensive, easy to manipulate

disadvantage- soluble in oral fluids, undergoes plastic deformation

glass ionomer

powder is glass (aluminum silicate fluoride glass)/liquid polyalkalnic acid

advantages- chemical bond, relatively inexpensive, easy to manipulate, fluoride release (skeptisim)

disadvantages- very soluble in oral fluids, prolonged final set (days)

resin modified glass ionomer cement

powder is glass (aluminum silicate fluoride glass)/liquid polyalkalnic acid + resin (hydrophilic resin HEMA)

advantages- chemical bond/acid from cement, resin bond, fluoride release, good compressive strength, easy to manipulate

disadvantages- expansion (hygroscopic), soluble in oral fluids

resin cement

advantages- bond to tooth, high compressive strength, essentially insoluble

disadvantages- technique sensitive (etch the whole canal, application of bonding agent), very expensive, sensitivity to eugenol (poisions the catalyst), inhibition layer (cement line)

what are the indications for a prefabricated posts?

multiple rooted teeth with canals that are relatively circular in cross section

what are contraindications for prefabricated posts?

large, tapered canals

small, single rooted teeth like mandibular anteriors

what are advantages of prefabricated posts?

one office visit

ease of placement

less expensive to fabricate

can be made with composite cores allowing for final impression on the same day

what are disadvantages of prefabricated posts?

are best used in canals that are round

the core is retained mechanically and can disengage from the post

requires dentin removal at the apical 1/3

what are the core materials that can be used, ranked in strength order?

silver amalgam

composite resin

silver modified glass ionomer cement

fiber post system

carbon or silica fibers bounded by a matrix of polymer resin

are fiber or metal posts preferable?

no clinical evidence exists that the use of fiber posts reduces the occurrance of root fractures in vivo

no superiority of either rigid or flexible posts on tooth and/or restorable survival

most reported failures were root fracture and debonding- no significant difference was observed between fiber post and metal post in terms of root fracture or debonding

no difference was found in survival and success rates when treating endodontically treated teeth either with glass fiber reinforces or metal posts

the use of metal posts can be associated with an increased rate of root fracture

the use of fiber posts can be associated with an increased rate of secondary caries

what are the stats on fiber posts?

risk factors- anterior teeth, the number of remaining cavity walls

the number of cavity walls and the presence of ferrule wwere the key factors governing the longevity of the postendodontic restoration, rather than the material used for the post

3 yr follow up- teeth with ferrule (>2mm) 6.67% failure rate, teeth without ferrule (<2mm) 26.2% failure rate

how should you bond to root-canal dentin?

removal of thick smear layer

15 sec, 40% H3PO4 (mineral removal), rinse and dry

60 sec, 10-15% NaOCl (collagen removal), rinse and dry

folllowed by applying sulfinic acid sodium for 10 sec with rubbing motion and air-dry, this will prevent negative polymerization effects of NaOCL

how should you cement 3M fiber post?

clean or disinfect the root canal wtih 2.5-5.25% sodium hypochlorite solution

rinse immediately with water and dry with paper points

do not use hydrogen peroxide, other disinfectants, and EDTA solutions because their residues can impair the adhesion strength and curing reaction of relyX unicem cement

what is important to know about NaOCl?

it is a strong proteolytic and oxidizing agent

residual oxygen and oxidizing byproducts inihibits free-radiacal polymerization

clearfil DC activator

reducing/neutralizing residual oxidants (contains sulfinic acid/sulfinate-type reducing agent)

apply it with brush or dab it on with a micro brush

leave in contact for 30 sec

rinse and gently airdry

OR

apply 10% sodium ascorbate solution

leave in contact for 5-10 minutes

gentle agitation/friction while applying can help the solution penetrate the dentin

rinse thoroughly

what are the parts of 10 MDP (methacryloyloxydecyl dihydrogen phosphate), and what are they for?

methacrylate functional group- polymerization

phosphoric-acid ester functional group- ionic bonding with CA of Hap

spacer with adequate length- efficient separation of both functional end groups, provides hydrophobicity

phosphoric acid ester functional group for etching- enables micromechanical interlocking and nano-layering

tldr for this whole lecture

importance of proper diagnosis and treatment planning

coronal coverage for premolars and molars

3 factors for proper post and core- 360 degree ferrule effect, length of post, apical seal

proper post and core design material