R OOT R ESORPTION Whats to blame, bad genes, bad mechanics or bad luck? Lecture 6 – Dr. Ingrid Reed 1

D EFINITION 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.,

D EFINITION 3 Root Resorption (RR) Microscopic areas of lacunae that occur on surfaces and areas of the root under compression Not detectable on radiographs EARR and RR Distinct but related RR detected histologically may Be a preliminary step towards EARR

R OOT R ESORPTION - M ECHANISM 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 4

E XTERNAL A PICAL R OOT R ESORPTION 5 Why the apical portion? Force concentration Periodontal fiber orientation increased stress Cementum Apical third cellular cementum patent vasculature softer cementum Coronal third Acellular cementum

M EASUREMENT OF R OOT R ESORPTION 6 Measurement Length of root Degree of root resorption Periapical film – best Panos may overestimate by 20&

R OOT RESORPTION CLASSIFICATION METHOD 0 = no visible root resorption (0 mm) 1 st degree = mild, apex blunt, diffuse (1-2mm) 2 nd degree = moderate, apex disappears, looks like half moon with no taper (2-4 mm) 3 rd degree = severe, excessive blunting, apex is discontinuous, resorption is > ¼ of the root (> 4 mm) 7 Jiang et al., 2010 Sharpe 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% 8

E TIOLOGY & S USCEPTIBILITY 9 Cellular Genetics Orthodontic treatment Age Gender Dental morphology Force direction & amount Extraction versus nonextraction Treatment duration Distance and direction of tooth movement

G ENETIC F ACTORS Genetic IL-1B genotype Decreased IL-1B cytokine less bone resorption more strain on tooth increase root resorption 10

S USCEPTIBILITY 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 11

S USCEPTIBILITY Force levels Light (25 gms) 3.49 fold > volumetric resorption Heavy (225 gms) fold > volumetric resorption Direction of tooth movement Intrusion causes 4 x more resorption than extrusion 12

S AMESHIMA STUDY - ( AJO 119:5) D IAGNOSTIC F ACTORS 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 13

T REATMENT F ACTORS 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 14

R ULE 1 15 Never, ever move a tooth with a fixed or removable appliance without taking a radiograph

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17 9/25/03 Patient K.B.

18 5/24/07 Patient K.B.

19 s.p. 11/4/2003

20 s.p. 11/19/2008

TREATMENT 21 Stop orthodontic force Root resorption continues until a functional PDL is established If resume treatment PAs every 3 months, light forces

22 R EADINGS 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: 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: 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