ROOT RESORPTIONWhat’s to blame, bad genes, bad mechanics or bad luck?

Lecture 6 – Dr. Ingrid Reed

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DEFINITION

External Apical Root Resorption (EARR) The loss of root structure involving the apical region to

the extent that it can be seen on standard radiographs*

An unavoidable pathologic consequence of orthodontic treatment**

*Hartsfield et al., 2004** Yamaguchi et al., 2008 2

DEFINITION

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Root Resorption (RR)• Microscopic areas of lacunae thatoccur on surfaces and areas of the root under compression• Not detectable on radiographs

EARR and RR• Distinct but related• RR detected histologically mayBe a preliminary step towards EARR

ROOT RESORPTION - MECHANISM

Tooth movement – bone remodeling Hyalinized areas of PDL – cementum near

this area is attacked by clast cells, usually repaired

Root as well as bone remodeling – feature of orthodontic tooth movement

Large defects at the apex – become separated from root

These islands of cementum are resorbed and not repaired – shortening of roots

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EXTERNAL APICAL ROOT RESORPTION

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Why the apical portion? Force concentration Periodontal fiber

orientation increased stress

Cementum Apical third

cellular cementum patent vasculature softer cementum

Coronal third Acellular cementum

MEASUREMENT OFROOT RESORPTION

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Measurement Length of root Degree of root

resorption Periapical film – best Panos may

overestimate by 20&

ROOT RESORPTIONCLASSIFICATION METHOD

0 = no visible root resorption (0 mm) 1st degree = mild, apex blunt, diffuse (1-

2mm) 2nd degree = moderate, apex disappears,

looks like half moon with no taper (2-4 mm) 3rd degree = severe, excessive blunting,

apex is discontinuous, resorption is > ¼ of the root

(> 4 mm)7

Jiang et al., 2010Sharpe et al., 1987

INCIDENCE

No orthodontic treatment 7-13%

Orthodontic Treatment > 3mm of resorption 33% > 5 mm 2% of adolescents, 5% adults > ¼ of both maxillary central root lengths 3%

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ETIOLOGY & SUSCEPTIBILITY

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Cellular Genetics Orthodontic

treatment Age Gender Dental morphology Force direction &

amount Extraction versus

nonextraction

Treatment duration Distance and

direction of tooth movement

GENETIC FACTORS

Genetic IL-1B genotype Decreased IL-1B cytokine → less bone resorption

→ more strain on tooth → increase root resorption

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SUSCEPTIBILITY

Orthodontic Treatment – tooth movement Time in fixed appliances Amount of tooth movement

Gender – no difference Age -

Younger patients – cementoid has protective mechanism Adults – reduced ability to repair

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SUSCEPTIBILITY

Force levels Light (25 gms) 3.49 fold > volumetric resorption Heavy (225 gms) 11.59 fold > volumetric

resorption Direction of tooth movement

Intrusion causes 4 x more resorption than extrusion

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SAMESHIMA STUDY - (AJO 119:5)

DIAGNOSTIC FACTORS

Maxillary anterior teeth primarily (avg. 1.4mm)

Worse in maxillary laterals with abnormal root shape (pipette, pointed, dilacerated)

Adults > children in mandibular anterior only Asian < Caucasian or Hispanic ↑ overjet but not overbite associated with

greater root resorption Male = female

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TREATMENT FACTORS

Premolar extraction > non extraction Duration of treatment → increase Horizontal displacement of incisors (overjet)

→ increase No difference

Slot size Archwire type Use of elastics Types of expansion

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RULE 1

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Never, ever move a tooth with a fixed or removable appliance without taking a radiograph

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9/25/03Patient K.B.

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5/24/07Patient K.B.

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s.p. 11/4/2003

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s.p. 11/19/2008

TREATMENT

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Stop orthodontic force Root resorption continues until a functional

PDL is established If resume treatment PA’s every 3 months,

light forces

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READINGS  Al-Qawasmi RA, Hartsfield JK, Jr., Everett ET, Flury L, Liu L,

Foroud TM, Macri JV, Roberts WE. Genetic predisposition to external apical root resorption. Am J Orthod Dentofacial Orthop 2003;123:242-52.

Han G, Huang S, Von den Hoff JW, Zeng X, Kuijpers-Jagtman AM. Root resorption after orthodontic intrusion and extrusion: an intraindividual study. Angle Orthod 2005;75:912-8.

Hartsfield JK, Jr., Everett ET, Al-Qawasmi RA. Genetic Factors in External Apical Root Resorption and Orthodontic

Treatment. Crit Rev Oral Biol Med 2004;15:115-22

Special thanks to Dr. Julie Olsen for the use of some of her material

Text pages 349-351

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