root resorption and non-vital bleaching

lecture given 6/15/2026

resorption

a condition associated with either a physiologic or a pathologic process resulting in a loss of denin, cementum, and/or bone

internal resorption

a pathologic process initiated within the pulp space with the loss of dentin and possible invasion of cementum

may or may not perforate to the external root surface

what is the etiology of internal resorption?

trauma, infected coronal pulp, metaplastic tissue, extreme heat during cutting

the loss or alteration of the odontoblastic layer and predentin is a prerequisite

histology of internal resorption

granulation tissue with multinucleated giant cells

loss of odontoplastic layer

necrotic pulp coronal to granulation tissue

bacteria in dentinal tubules

no adjacent bone resorption

what are the clinical manifestations of internal resorption?

asymptomatic

discovered in routine radiographs

vital pulp

pink tooth

what is the radiographic appearance of internal resorption?

fairly uniform radiolucent enlargement of the pulp canal

what is the treatment for internal resorption?

perform root canal therapy as soon as possible

what is the prognosis for internal resorption?

good

fair/poor if perforated externally

external resorption

resorption initiated in the periodontium and initially affecting the external surfaces of the tooth

what are the classifications of external resorption?

surface (early stage, histologic condition, cannot be observed clinically)

replacement (late stage)

inflammatory (mid stage)

surface resorption

a physiologic process causing small superficial defects in the cementum and underlying dentin that undergo repair by deposition of new cementum

what is the etiology and histology of surface resorption?

minor luxation injury, orthodontic movement

small resorptive lacunae with local inflammatory response

what are the clinical manifestations of surface resorption?

asymptomatic

what is the radiographic appearance of surface resorption?

invisible (histological condition, not visible)

replacement resorption

a pathologic loss of cementum, dentin, and PDL with the ingrowth of bone into the defect and fusion of bone to dentin with a loss of physiologic mobility and the lack of radiolucency at the resorptive interface

sounds like ankylosis to me

what is the histology of replacement resorption?

direct contact between bone and dentin without a separating PDL and cemental layer

what is the etiology of replacement resorption?

extensive trauma, replantation

avulsion if outside of the socket for over 1 hr, esp if dry

what are the clinical manifestations of replacement resorption?

lack of mobility, metallic sound to percussion, infraocclusion in the developing dentition

ultimately tooth is lost due to loss of root support

inflammatory resorption

a pathologic loss of cementum, dentin, and bone resulting in a defect in the root and adjacent bony tissue

what are the classifications of inflammatory resorption?

cervical, lateral, apical

what is the etiology of inflammatory resorption?

dental trauma, pulp necrosis, excessive mechanical forces, intracoronal bleaching, pressure from impacted teeth, tumors, replantation

unprotected or altered root surface attracting resorbing cells and inflammatory response maintained by infection

what is the histology of inflammatory resorption?

periodontal infiltrate with lymphocytes, plasma cells, and polymorphonuclear leukocytes

mutlinucleated giant cells resorbing root surface

what is the radiographic appearance of inflammatory resorption?

progressive radiolucent areas of the root and adjacent bone

mottled appearance

what are the clinical manifestations of inflammatory resorption?

depends on the pulpal status

pink spot is common in cervical resorption

what is the pulp status during inflammatory resorption?

apical → necrotic: treatment with endo therapy, good prognosis

lateral → necrotic: early diagnosis is key, perform endo treatment, Ca(OH)2 medicament, could be reversed, surgical treatment if needed

cervical → vital: pulp plays no role but could get exposed

external cervical resorption

invasive cervical resorption (ICR)

relatively uncommon form of cervical resorption according to literature

however, it is the most commonly encountered clinically

how is invasive cervical resorption diagnosed and managed?

CBCT imaging- extent and location of defect, proximity to the pulp, restorability of the tooth, pulp status

type of defect- closed resorptive, open resorptive

external resorption

resorption initiated in the periodontium and initially affecting the external surfaces of a tooth

surface, inflammatory, or replacement

cervical, lateral, or apical

how can you differentiate between external and internal resorption via radiographs?

take fims with a change in angulation of the x ray beam

internal resorption- root canal outline is distorted, root canal and the defect appear continuous

external resorption- root canal outline is normal, appears running through radiolucent defect, always accompanied by resorption of bone

CBCT imaging is key in diagnosis and treatment planning

vitality testing for external vs internal resorption

negative response in apical and lateral external inflammatory resorption

positive response in cervical resorption

positive response in internal resorption

nto always accurate

pink spot

internal resorption OR some cervical resorption

the dental profession has an obligation to treat discoloration…

in the most conservative manner possible

tooth bleaching

the method of choice based on conservation of tooth structure and its effectiveness in lightning tooth discoloration

what are the causes of external discoloration?

tobacco, colored plaques, food stains, drug stains (chlorhexidine, NOT tetracycline)

what are the systemic factors that can cause internal discoloration?

porphyria, amelogenesis imperfecta, fluorosis, tetracycline

what are the local factors that can cause internal discoloration?

trauma, protein degradation products, pulp remnants, agents used in RCT, metallic salts (mercury, silver, copper, iodine)

what is the etiology of tooth discoloration?

trauma → free red blood cells → hemolysis → hemoglobin → iron + hydrogen sulfide → iron sufide (black compound)

pulp necrosis → protein degradation products → greyish tooth discoloration

what are the indications for non-vital bleaching?

etiology, complete obturation of the root canal system, intact tooth structure

what are contraindications for non-vital bleaching?

extensive restorations, crown defects (fractures, hypoplastic enamel), severely undermined enamel, discoloration due to metallic salt (lower confidence in effectiveness)

what are commonly used bleaching agents?

sodium perborate

3% hydrogen peroxide

30% hydrogen peroxide (superoxol)

3-15% carbamide peroxide (opalescence)

what are commonly used non-vital bleaching agents?

thermocatalytic technique (superoxol + heat)

walking bleach technique (sodium perborate + water or H2O2)

combination

which bleaching technique is occasionally associated with external root resorption?

intra coronal bleaching with H2O2

what is the pathogenic mechanism of external root resorption after non-vital bleaching?

diffusion of H2O2 through the radicular dentin

cementum defects, mainly at the CEJ, significantly enhance the H2O2 seepage

how much of the population has cementum defects that may be present in anterior teeth (would be affected in non-vital bleaching)?

25%

what can be used as a barrier during non-vital bleaching?

IRM, ZOE, composite, glass-ionomer

is the material or barrier thickness and its relation to the CEJ more important when trying to prevent H2O2 seepage?

barrier thickness and its relation to the CEJ!

what are recommendations for the barrier when doing non-vital bleaching?

a 2mm intracoronal isolating base, placed at the CEJ level

the barrier should block all dentinal tubules leading from the pulp chamber which reach the tooth surface apical to the epithelial attachment, so that the bleaching agent stays inside the access cavity

what is the problem with using the labial CEJ as a guide for barrier placement?

it leaves the proximal dentin tubules unprotected

what are the procedure steps of non-vital bleaching?

diagnosis- determine reason for discoloration, check the vitality of the tooth, complete RCT, retreat if obturation is inadequate

record shade- a photograph and a shade guide provide legal and treatment references to mesure the progress of color enhancement

record barrier probing

tooth isolation

access cavity

remove gutta percha to a level of 2mm below the CEJ to make space for the barrier material

transfer barrier probing

place barrier material

check barrier outline, probing MLD

bleach- thermocatalytic or walking bleach technique