endodontic success & failure

lecture given 5/19/2026

what are the goals of endodontic therapy?

restore teeth to proper form and function

eliminate or prevent infection

allow patients to maintain teeth that otherwise would be extracted

what is the range of success of conventional endodontic therapy?

61.1 - 94.8%

what is the general success rate of endodontic retreatment?

83%

the absence of what signs/symptoms can demonstrate clinical success of endodontic treatment?

no spontaneous pain, negative to percussion, negative to palpation, absence of sinus tract, absence of swelling

what radiographic features demonstrate success of endodontic treatment?

contours, width, and structure of PDL are normal

how long is a desirable follow up period for endodontic treatment?

4 years is desirable- minimum of 1 year

what is the etiology of failure of endodontic therapy?

presence of infection in root canal system

what is the triad of success of endodontic therapy?

diagnosis

cleaning, shaping, and 3D obturation

coronal restoration

what are the goals of cleaning, shaping, and 3D obturation?

eliminate organic material and bacteria from root canal system

prevent future bacterial contamination and infection

seal any remaining bacteria within the root canal system

what are options for post endodontic coronal restoration?

temporary restoration, post preparation, proper coronal restoration

quality of coronal restoration is important

temporary restoration

divergent access preparation

thickness of 4mm

cavit temporary recommended

immediate premanent restoration

post preparation

use of rubber dam

maintain 5mm of apical gutta-percha

heated carrier followed by rotary instrument

failure to adequately and properly restore the endodontically treated teeth may result in…

vertical fracture of tooth structure

proper coronal restoration should provide…

cuspal coverage to protect teeth under occusal forces against vertical fractures

t/f both anterior and posterior endo treated teeth need crowns

false- anteriors have similar success rates with crown or without, but premolars and molars have much lower success rate without crowns and should be crowned after RCT

what is more important- good endo or a good restoration?

ideally good endo and good restoration but poor endo with a good restoration has a higher success rate than good endo with a bad restoration

t/f the technical quality of the coronal restoration is significantly more important than the technical quality of the endodontic treatment for apical periodontal health

true

what factors have debated importance?

tooth type, age, sex, ethnicity, size of lesion

what are biological factors that may impact prognosis?

apical pathosis, pulp vitality, apical resorption, patient’s general health, pre and postoperative pain

what are therapeutic factors that may impact prognosis?

obturation quality, intra-canal medication, number of treatment sessions, procedural periapical disturbances, type of filling material

____ teeth have higher success rate than _____ teeth

vital, necrotic

teeth with periapical lesions have ____ success than teeth without lesions

lower

presence of bacteria at time of ______ will lower success rate

obturation

how many treatment sessions are needed for RCT?

vital cases- 1 visit

necrotic cases- 2, calcium hydroxide should be used between visits to eliminate infection

what can lead to endodontic failure?

inadequate treatment, missed canals, presumably calcified canals, presence of obstructions, perforations, coronal leakage, combination factors

if a RCT tooth is deemed to be a failure and access to canals is impossible, what should be done next?

surgery

if a RCT tooth is deemed to be a failure but access to canals is possible, what should be done next?

retreatment

if you take a radiograph of a RCT tooth and there is bone loss surrounding the entire root, what should be done?

extraction- the tooth is likely fractured

what are the commonly missed canals in mandibular molars?

2nd and 3rd distal canals

3rd mesial canal

what are the commonly missed canals in maxillary molars?

2nd mesio-buccal

2nd disto-buccal