nonsurgical retreatment

lecture given 6/1/2026 by the man, the myth, the legend, Zeim like dime

healed

functional, asymptomatic teethw ith no or minimal radiographic periradicular pathosis

nonhealed

nonfunctional, symptomatic teeth with or without radiographic periradicular pathosis

functional

a treated tooth or root that is serving its intended purpose in the dentition

what did penick report in 1961?

3 out of 10 cases that showed no evidence on radiograph of bony healing but histological examination revealed the formation of dense fibrous tissue

aka non-ideal healing, we would prefer bone

what is a major factor in long term healing?

apical periodontitis

what did the toronto study find?

92% healed w/o periapical radiolucency

74% healed with radiolucency

97% functional overall

aka apical periodontitis is a major factor in long term healing

2 major factors affected success rates in retreatment cases- presence of preopertive radiolucency, presence of preoperative perforation

t/f there are a lot of root canals done every year, but a low number of cases that go wrong, so it’s fine, endo is perfect

false- millions of root canals done with 86-98% success rate but even with a low number of cases, it adds up

t/f failure is a good word to use with patients

false- friedman has recommended using posttreatment disease because failure sounds like it was our fault and sometimes it isn’t!

what are the etiologies of undesirable outcomes?

iatrogenic procedureal errors- poor access cavity design, untreated canals (major and accessory)

canals that are poorly cleaned and obturated

complications of instrumentation- ledges, perforations, separated instruments

overextensions of root filling materials

persistant intra-/extracanal infection

coronal leakage

radicular cysts

what are the 4 groups of etiologic factors that clinicians should use to effectively treatment plan?

persistent or reintroduced intraradicular microorganisms

extraradicular infection

foreign body reaction

true cysts

persistent/reintroduced intraradicular microorganisms

root canal space/dentinal tubules are contaminated with microorganisms → periradicular tissue → apical periodontitis- inadequate cleaning/shaping/obturation/final restoration

ledge or separate instruments- causes an inability to remove or entomb the microorganisms

or new microorganisms can reenter the cleaned and obturated canal

it has been asserted that persistent or reintroduced microorganisms are the MAJOR causes of posttreatment disease

primary infection

untreated teeth- polymicrobial (10-30 species), primarily anaerobic flora

microorganisms in previously treated teeth

very few species or even one single species

primarily facultative anaerobic gram positive

commonly e. faecalis which is very resistant to disinfection

fungi like c. albicans have been found and may be responsible for the recalcitrant lesion

why does e. faecalis survive?

escapes intra-canal antimicrobial procedures

invades dentinal tubules to resist chrmomechanical preparation

endures periods of nutrient deprivation in the filled root canal

resistant to calcium hydroxide

survives in environment with low availability of nutrients

flourishes when the nutrient source is re-established

extraradicular infections

bacteria can invade the periradicular tissues- direct spread of infection from the canal space, extrusion of infected dentin chips, contamination with overextended/infected instruments

usually the host response can destroy these but some microorganisms are able to resist the immune defenses and persist in the apical tissues- extracellular matrix or protective plaque, a. israelii and p. propionicum can exist in periapical tissues and may prevent healing after RCT

foreign body reaction

outcome assessments generally show that filling material extrusion (radiographic flush or gross extension) leads to lower healing- may include inadequate canal preparation, inadequate obturation, vigorous overinstrumentation

gutta-percha/sealers are usualy well tolerated and healing can still sometimes occur esp if it has not been inoculated with microorganisms

true cysts

retained embyronic epithelium (epithelial cell rests of malassez) begins to proliferate due to the presence of chronic inflammation

this cyst formation may be an attempt to help separate the inflammatory stimulus from the bone

reported to be 15-42%

cannto determine radiographically

2 types- true cysts, periapical pocket cysts

periapical true cysts

contained lumen within a continuous epithelial lining, probably do not heal following NSRCT and usually require surgery

periapical pocket cysts

lumen is open to the root canal of the affected tooth

for a patient harboring true endodontic posttreatment disease, what are the 4 basic options for treatment?

do nothing

extract the tooth

nonsurgical retreatment

surgical retreatment

if you know the etiology of the posttreatment disease is persistent or reintroduced microorganisms, what are the treatment options?

NSRCT and/or SRCT

if you know the etiology of the posttreatment disease is persistent extraradicular infection, foreign body reaction, or true cyst, what are the treatment options?

SRCT

what needs to be true to be able to retreat a tooth?

tooth must be restorable and retreatable

apparently adequate root filling with no signs of coronal leakage- surgery could be the option

RCT seems below acceptable standard and no symptoms or signs of apical disease- no treatment unless new restoration with conservative retreatment

ledge or separated instrument that cannot be removed- possibly surgery (can frequently be bypassed by even if not can enhance surgery success

suspect a root fracture…

narrow based probing defect and/or J shaped lesion encompassing the root apex and extending in a coronal direction

apical surgery (apicoectomy, root resection, extraction) may be an option

nonsurgical retreatment

provides the most benefit with the lowest risk

greatest likelihood of eliminating the most common cause of posttreatment disease (intraradicular infection)

nonsurgical retreatment is usually less invasive than surgery and has a less traumatic postoperative course

may be more costly than surgical treatment

amount of time needed for retreatment is usually longer than surgical intervention

what are the healing rates for nonsurgical treatment?

74-98%

healing rates with apical surgery alone, only 59%

when apical surgery is preceeded by orthograde retreatment the incidence of complete healing rises to 80%

what are the steps of nonsurgical retreatment?

coronal access cavity prep

post removal

regaining access to the apical area

gutta-percha removal

removal of separated instruments

heat generation during retreatment procedure

management of canal impediments

finishing the retreatment

what are potential complications of post removal?

fracture of the tooth

tooth now unrestorable

root perforaton

post breakage

inability to remove the post

ultrasonic heat generation

what happens if you perforate?

first determine IF the tooth should be salvaged

should be repaired immediately

the prognosis will worsen with time

what obturation materials should be removed?

gutta-percha

silver points (1970s)

pastes

resilon (polyester material bonded)

carrier based

things that can help- contacting previous dentists to inquire, asking origin/country of RCT

gutta percha removal

ease of visibility

relative ease of removal- heat, solvents (chloroform, methylchlorofom, eucalyptol, halothane, turpentine, xylene)

mechanical instrumentation

t/f chlorform is a no-go now in dentistry

false- when used correctly it is safe and effective

when a separated instrument/foreign object is located in the (coronal/middle/apical) third, what should you do?

attempt retrieval, attempt retrival or bypass, surgical retreat

what are the most common causes of instrument separation?

improper use- overuse, applying too much apical pressure

limitations of physical properties- frictional stress, dry, overload flutes

inadequate access

anatomy- abrupt curves, anatomic ledges

manufacturing defects- seldom

do hand files or rotary files separate more often?

rotary files- 1.68-2.4%

hand files- 0.25%

what should be the first thing you do when you separate an instrument?

take a radiograph- location, size segment, canal anatomy, removal chances

inform pt and advise of its effect on prognosis

what is the prognosis of a RCT with a separated instrument?

depends on stage of instrumentation, preoperative status of pulp

can it be removed or bypassed?

if cannot be removed or bypassed in a necrotic pulp and apical periodontitis- uncertain prognosis, needs follow up with possible surgery or extraction

why is heat generated during retreatment?

soften canal filling materials, ultrasonics to dislodge posts and separated instruments

*how much can softening canal filling materials or ultrasonics raise the external root surface by?

10 degrees C or more, excess of 10 can damage the attachment apparatus

using ultrasonic vibration without coolant, temp can be raise by 10 in 15 seconds

t/f heat damage is time dependent

true- use water, take breaks, avoid using the highest setting

what are possible canal imediments?

a block or ledge in the apical portion- residual pulp tissue, necrotic tissue, dentinal mud (possibly infected debris), the area is not cleaned and sealed

persistent disease/posttreatment disease

how can you regain canal length and patency?

coronal portion of the canal can be enlarged to increase tactile feel

canal should be flooded with irrigant

gently probed with a precurved #8 or #10 file

the tip of the file has a small bend to aid in bypassing ledges

once bypassed, short-amplitude push-pull and slightly rotational movement keeping apical of ledge

what should you do if canal blockage or ledge cannot be negotiated?

clean/shape and obturate to that point

inform pt of complication and prognosis

regular reevaluation

of symptomatic- surgery or extraction

perforation

caries, resorption, iatrogenically (zip, strip, furcation)

clues in the diagnosis work up- radiographs, cervical/midroot may have epithelial down growth with periodontal defect/probing

nonsurgical (internally) or surgical (externally)

when do most iatrogenic perforations happen, according to kvinnsland et al?

53% during insertion of posts

47% during routine endo treatment

73% occur in the maxilla

in max anterior teet, nearly all perforations were located in the labial root aspect (underestimation of the palatal root inclination)

what factors affect the prognosis of a perforation?

location- generally more apical is more favorable, but coronal are easier to repair

time delay before repair- ability to seal, previous contamination

immediate repair better than delayed repair- breakdown of periodontium, inflammation, contamination

site- worse prognosis when in critical zone, coronal to critical zone is good bc easily accessible/adequate seal/no perio involvement, apical to critical one good bc usually adequate endo/ability to seal/they can be cleaned and sealed with a much lower risk of bacterial entry from oral cavity or chronic inflammatory lesion developing

critical zone

relative to the level of the crestal bone and epithelial attachment

why is the prognosis worse when a perforation happens in the critical zone?

close proximity to the gingival tissues leads to contamination of the perforation with bacteria from the oral cavity

a periodontal defect will be created by the apical migration of the epithelium into the perforation site

rapid pocket leads to lowest success rate of repair

furcation perforation sometimes respond the same way

based on prognostic factors, (fresh/old), (large/small), (apical/crestal/coronal) perforations have a good prognosis

fresh, small, apical or coronal

based on prognostic factors, (fresh/old), (large/small), (apical/crestal/coronal) perforations have a poor prognosis

old, large, crestal

what are the criteria of an ideal repair material?

superior seal, biocompatible, nontoxic, insoluble, regeration of periapical tissues (osteogenesis, cementogenesis)

in the past, what was used as perforation repair material?

amalgam, super EBA, various composites

what is now used as perforation repair material?

MTA, biodentine, bioceramic, geristore

MTA (mineral trioxide aggregate)

medical grade protland cement

seals well, even when with blood

very biocompatible

cementum-like material grows directly on

favorable long-term studies

disadvantges- long setting time, handling characteristics

biodentine

versatile, saves teeth, excellent sealing properties

sets in 10-12 minutes

6 min handling time, 6 min to set in mouth

BC-RRM

moldable/condesable putty consistency, syringe delivery, extremely resistant to washout, shortened setting time (20 min)

highly biocompatible, osteogenic, anti-bacterial, non-staining

geristore

dual cure resin ionomer

extremely biocompatible

paste-paste

self adhesive

what should you do if nonsurgical retreatment doesn’t work?

observation, endodontic surgery, extraction-replantation, extraction

functional retention of the tooth

somtimes a rooth with persistent apical periodontitis may remain in asymptomatic function for years

not complete healing, but retained without pain- regular recall revaluation