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Furcation Depth and InterrootSeparation Dimensions for 5Different Tootti Types

Chris Ward, DMD'/Henry Greenwell, DMD, JD, MSD"/John W. Wittv^er, DDS MS"'/Connie Drisko, DDS""

The purpose of this study wos to document mean, standard deviation, ondrange ot furcation depth and interroot separation dimensions af 5 multi-roofed tooth types. A fof oi ot 412 extracted feeth were examined andclassified as: maxillary first molar maxillary second malar maxiiiary first pre-moiar, mandibuiar first malar, and mandibular secand malar The furcationdepth was measured at the level of the furcation dome and 3 ond 5 mmapical to the dome. Interraat separation was measured 3 and 5 mm apicalto the furcation dame. Mean furcation depth at the dome was 7.48 mmbuccaity and Ó.Ó7 mm mesiodistaity for maxillary first molars; 6.69 mm buc-caily and 5.94 mm mesiodistaity far maxiiiary second moiars; 3.54 mmmesiodistdliy for maxiiiary first premoiars; 7.96 mm buccoiingudtiy formandibuidr first moiors; and 7.46 mm buccoiingudtiy for mondibuior sec-ond moiars interroot separation dimensions 3 mm apiodi to the damewere: 2.58 mm buccaliy, 4.17 mm mssiaily, and 4.48 mm distatiy for maxii-iary first malars; 1.92 mm buccatly 3.89 mm mesialiy and4.04 mm distatiyfar maxiilory secand molars; 2.47 mm mesiatly and 2.58 mm distaity tar max-iliary first premolors; 3.15 mm Puccaliy and 2.95 mm iinguatiy for mondibu-tar first moiars; and 2.54 mm Pucoally and 2.75 mm linguaily tor mandiPuiarsecond malars. (int J Periodontics Restorative Dont 1999; 19:251-257.)

'Endodontics Resident Aibert Einsfein Coiiege of Dentistry,Phiiodeiphio, Pennsyivania.

•'Associate Protessor and Director, Groduate Periodontics,University of Louisviile, Kentucky

*'-Profes5or ond Assistant Director, Graduate Periodontics,University of Louisviiie, Kentucky.

•'"Professor and Choirperson, Deportmenf of Periodontics, Endo-dontics, and Dental Hygiene, University of Louisville, Kentucky.

Reprint requests: Dr Henry Greenweli, Graduate Periodontics,School of Dentistry, universify of Louisville, 501 South Preston. Room236, Louisville. Kentuci<y «292.e-mail: PerioHenry@aol.com

A furcation invoivemenf existswhen periodonfal disease hascoused bone résorption andconnective tissue attochmentloss into the bifurcotion or trifur-cafion of G muitirooted tooth.This is considered one of themost serious compiicotions ofperiodontal diseose. Until re-cently, such teeth were given aquestionabie prognosis andoften considered an indicationfar foofh/root resection or evenextraction.

The furcation areas ot thetooth con be divided into 3parts; (1) the area of root sepa-rotion where the 2 roots areseparoted by aiveolar bone; (2)the root trunk, which is the areabetween the cementoenameljunction ond the root separa-tion and usuaiiy contoins agrooved, often concave, parfjust coronai to fhe furcotioncailed the "fiufe"; and (3) thefurcofion roof or dome, which isthe portion just coronoi to thefurcai bone.'

Lindhe and Nyman^ ciassi-fied the turcation invoivements

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as Degree i, ii, or ili. Degree Iinvelvement denotes horizontolloss of periedental tissue supporfless than 3 mm within fhe furca-tion area. Degree II invelvementindicates G horizontai less efsuppert exceeding 3 mm butnot encompassing fhe totalwidth ef the furcation area.Degree III refers fo horizanfal"threugh-and-fhrough" destruc-tion ef the periodontGi tissues inthe furcation.

Grant et o i ' reporfedanether method of classificationthaf is in mere common use inthe United States. Class i de-notes involvement of the fluteenly, CIGSS il denetes invoive-ment partially under the roof ordome, and CIGSS Ili involvemenfindicGtes fhreugh-Gnd-threughless ef furcafien bone andGtfGChment, Glickman 's ClinicalPeriodantoiogy^ uses a similGrclassificatian wifh Grade Ithraugh IV invelvement. The pri-mary difference is the GrGde IV,which means no soft fissue cov-erage of the through-and-fhrough furcation defecf,

Tarnow and Fletcher" pre-senfed a subclossificofien thattakes into account the probe-able verticai depth fram fhereof of fhe furcation opieallyThe following subclasses oredefined: subcloss A = 0 to 3 mmprobeabie depth from fhe roefof the furcG; subclGSS B = 4 te 6mm prebeable depth fram thereof of the turco; ond subclassC = 7 mm or greafer probeabiedepfh from the roef af fhe

furcG. Furcations con thus Peclassified as Class I subclass A, B,or C; Class II A. B, or C; or Cioss IliA, B. or C. This system is descrip-tive of bofh fhe horizontai andverfical cempenents of furca-fien bene loss.

The roie of furcafien dimen-sions in predicting treatmentoutcome has had some otten-tien, primoriiy in the regenerG-tive treatment of Ciass iil furco-fions. Penteriero ef GI^ repertedthat Ciass iii turcotien defeatswifh an entrance height afgreofer fhan 3 mm did nof heaiwith complefe closure. They alsoreported that when fhe cross-sectienal area of fhe furcationopening exceeded 4 mm^cemplete closure was notachieved. Mehlbouer* found onreentry that hard tissue elesurewas not achieved in Class III fur-cation defects if fhe verticalentrance height was greaterthan 4 mm.

Frem a ciinicol standpeint onarrow interroot separationmeans there is minimol beneGVGÜGble OS G cell source for Gheaiing defect. It also meansthat there is little bone te serveas a seurce ef vascularify for theheoling wound. The amount ofperiodontal iigament celis avail-abie is more dependent on theroot circumference than en fheinferreet seporafian dimensien.

Horizontal furcGfion depfhCGn Gise affecf the Gmount efbane available fo serve os acell ond vGscular source. Thisdepfh will vary wifh fhe general

level of horizenfal Pene lossaround fhe feofh. Since reefstaper in an apicol direction, hor-izentGi furcation depfh willdecrease with increasing heri-zontai bene less.

The purpose of fhis sfudyWGS fo document mean ondrGnge deta for furcation depthand interreet separation dimen-sions of 5 differenf muitirootedteeth types. This infermaticn isneeded to provide referencemeosurements of potentiai sig-nificance in regenerative furca-tion therGpy

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fig 1 Measuremenf method far furcaticn depth ot maxiiiarymoiars.

fig 2 Meosurement method for furcation depth otmondibuiar moiars.

Mettiod and materials

A tofol of 412 mulfirootedhumon feeth were randomiyselected from a oolleotion ofexfrocted teeth obtained troma privóte dentoi practice and oUnited Stotes Army DentoiClinic ot Fort Knox. Kentucky.The teefh were extrocted fordifferenf fypes of dentol condi-tions (endodontic, periodontoi,prosthodontic. orthodontic,nonrestorabie oaries, etc) ondwere coiiected primoriiy fromCauoosion potients.

The teeth with intact rootswere fixed and stored in 10% for-malin untii use. They were thenpioced in 3% sodium hypochio-rite soiution for 3 hours fo aid inremoving the remaining sotf tis-sue. All teeth were corefuiiydebrided of tissue fags and coi-ouius using uitrasonic anO hondinsfrumentotion. The coiculus

wos removed with minimoi aifer-otion of the tooth surtaoe.

The 412 exfrocted teethwere examined ond ciossifiedinto 5 morphoiogic tooth types:moxiiiory firsf moiors. moxiiiorysecond molars, moxiiiory firstpremoiars. mondibulor firstmoiors, and mondibuior secondmoiors. idenfificotion of fhetooth type wos bosed on toothmorphoiogy. Third moiors ondteeth with fused roots wereexciuded from the study Unoni-mous ogreement of 3 periodon-tisfs OS to fhe tooth type wosreouired or fhe tooth wos ex-cluded from fhe sfudy. The re-moining feeth were required tomeet the foiiowing inoiusion cri-terio: (1) no oories or restora-tions in the furoofion area of atieost one furcation; and (2)infacf roofs ot the point of rootseporotion ond 3 ond 5 mmapiooi to fhe roof seporafion.

The finoi somple of 273 teethinciuded: 95 maxiilory firsf mo-lars, 54 moxiiiory second moiors.3Ó maxiliory first premoiors. 49mandibuior first moiors, ond 39mandibuior second moiors.

The teeth were then exom-ined using teiescopio lenseswith2.óx mognificotion.The fol-lowing areas of eoch toothwere marked with o mechoni-coi penoii OS reference points:(1) point of root seporation; (2)3 ond 5 mm opioal fo the rootseparofion; ond (3) iine ongieson the furcol ospeof of eochroof. Furcotion depth was meo-sured from on imoginory pianethot wos ievel with the root sur-foces to the some imaginorypione on the opposite side ofthe tooth at the levei of the fur-cation dome and from 3 and 5mm apicai to the dome (Figs 1ond 2). interroot separofion wosmeasured from furcotion line

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Level

BuccalDome3 mm5 mm

Mesiai/distaDome3 mm5 mm

Totai teeth

Furcation depth of maxillary teeth

n

908987

92888295

First molarsMean±SD

¡mm)

7.48 ± 0.858,75 ± 0.989,55 ±1.08

6.67 ±0.526.58 ± 0.626.27 ± 0.73

Range¡mm)

6.00-10.007.00-11.007,00-13,00

5.73-7.995.30-8,224,69-8.11

n

434339

53494754

Second molarsMean ± SD

(mm]

6.69 ±1.027.73 ± 0.958,30 ± 1,14

5.94 ± 0.485,52 ±0,575.00 ± 0.66

Range(mm)

4.00-9.006,00-9,506,50-10,75

4,78-5,744,14-6,383.35-6.31

n

36363336

First premoiarsMean±SD

(mm)

3.54 ±0,483.05 ±0.542.57 ±0.59

Range(mm)

2.75-5.081,90-4,601.48-4.10

^ ^ ^ ^ ^ 1 Furcation depth of mandibular teeth

Level

Buccai/linguaiDome3 mm5 mm

Totai teeth

n

45494449

First molarsIVlean±SD

(mm)

7.96 ± 0,687,35 ±0.786.57 ±0,92

Range(mm)

6.47-9.395.99-9.174,55-8.72

n

39393839

Second molarsMean±SD Rar>ge

|mm) (mm)

7.46 ±0.74 5.40-8.566,62 ±0,75 4,44-7,815,76 ±0,75 4,20-6,80

ongle to furcation iine angie ofthe roots ot 3 ond 5 mm apicalto the furcation dome. Meo-surements were mode witii adigitoi micrometer caiiper to0.01 mm by one operator. Twomeosurements seporoted Py otieost 10 minutes were tai<en bythe some operotor ond themeon ot these two measureswos used. If the meosurementsdiffered by more thon 0.2 mm.

then the tooth was reexominedand remeosured. Data wereanalyzed and the mean, ston-dord deviation, ond rongewere coiculoted tor eoch mea-surement.

Results

The meon, standord deviotion,ond range ot turcotion depthfor all ieveis, the turcation dome,ond 3 and 5 mm apicai to thedome oppeor in Tobies 1 and 2.The meon, standard deviotion,and ronge ot interroot separa-tion for 3 and 5 mm apioal tothe dome oppeor in Tobies 3and 4.

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255

IBLevel

Buccai3 mm5 mm

Mesiai3 mm5 mm

Distai3 mm5 mm

Totai teeth

Interroot separation of maxillary teeth

n

9188

9590

928495

First moiarsMean±SD

(mm)

2.58 ± 0.612.83 ± 0.84

4.17 ±0.675.37 ± 0.82

4.48 ± 0.815.97 ± 0.96

Range(mm)

1.28-4.091.12-5.62

2.59-6.593.25-7.45

2.44-6.164.15-8.21

n

5249

5145

504954

Second molarsMean±SD

(mm)

1.92 + 0.601.97 + 0.80

3.89 ± 0.864.85 ± 1.09

4.04 + 0.795.09 + 1.07

Range¡mm)

0.50-3.160.26-3.57

1.48-5.841.40-7.03

1.89-5.572.26-7.06

n

3633

363336

First premoiarsMean + SD

(mm)

2.47 + 0.552.88 + 0.75

2.58 + 0.682.98 + 0.85

Range(mm)

1.15-3.501.32-4.29

1.00-4.351.36-4.89

Level

Buccal3 mm5 mm

Lir;gua!3 rnm5 mm

Total teeth

Interroot separation of mandibular teeth

First molarsMean + SD Range

n (mm) (mm)

48 3.15 ±0.56 1.49-4.4545 3.53 ±0.77 1.69-5.70

48 2.95 ±0.74 1.42-4.2745 3.24 ±0.94 1.25-5.4449

n

3938

393839

Second molarsfvlean ± SD Range

(mm) (mm)

2.54 ±0.59 1.56-3.902.71 +0.70 1.64-4.60

2.75 ±0.60 0.82-3.592.41 ±0.74 0.92-3.98

Discussion

The results of Pontcriere ef a\^ond Mehibauer* in freafingCloss III furcafien defects sug-gesf fhaf fhe verfical enfranceheighf of fhe defeof may be asignificanf focter in predictingregenerative treatment out-come. Using soft tissue mea-sures, Pontoriero et ai^ faundfhat compiete ciesure was not

achieved if fhe verficai en-france heighf was greafer fhan3 mm. iviehibauer* found fhothard fissue closure was ncfebfained when the verficaientrance height was greaterfhan 4 mm.

Ponfcriere ef al^ aise exom-ined fhe effecf of cross-seo-tional area of the defecfenfrance. which ccmbines thefactors of entrance height and

width. They did not achievecomplete ciosure when thecross-sectienal area exceeded4 mm^. This implies that furca-tion width (interrcet separatien)may alse have an infiuence onheaiing. Pepelassi et a l ' re-perted that Ciass iii furcafiondefecfs responded more fover-ably to grafting when theamount of interroof separafionwas 2 mm er greater.

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in general furcation depthwas found to decrease in anapical direction except tor thebuccal turcation of maxiliorymoiars, where the depth in-creased. This was because offlaring of fhe poiafal root. Interms ot regenerative heaiingfhis means that as vertical en-tronce height increases, theamount of available bone tis-sue decreases. Since rootstaper in an apicai direction,root circumference decreoses;fhis reduces the amount otperiadontai l igoment ceilsovoiiabie to repopuiote theheaiing wound. For moxiiiarymolar buccai turcations theamount of bone increases withincreasing vertical entranceheight but the amount of peri-odontai l igoment cells de-creases because ot the apicaitaper of the roots.

Between the 3 and 5 mmmeasurement points interrootseparation increased tor ali fur-ootions except the iinguai as-pect of the mandibuiar secondmolar. This was because at thepincher-like curvature of theseroofs, which converged be-fween the 3 and 5 mm paints.The mean of fhe maxillary buc-cal turcations was approxi-mafely 2 fo 2.5 mm, while themesial and disfal meons wereabouf 4 to 4,5 mm, Mandibuiarmolar inferroot seporatianswere approximqteiy 2.5 to 3.0mm. According to the observa-tion of PepelassJ et al ' 2 mm orgreater interroot separation

provides more favorable regen-erative healing; on average, aiimaxiiiary and mandibular molarfurcations meet this criteria.There may be an upper limit,however, at which the amountof interroot separation be-comes an inhibiting factor. This isimplied by Pontoriero et oi,^who tound that a crcss-seo-tionai entrance orea ot greaterthan 4 mm^ is not conducive tocomplete furcation closure.Thus fhe wider maxillary mesialand distal turcotions would, onaverage, exceed this cross-sec-tional orea with minimoi verticaldefect height.

Criticoi dimensions—height,width, and depth—for optimairegenerative heaiing may varyfor different furcotions depend-ing on the furcation defectarchitecture. These dimensionshave not been systemoticoliystudied but could provide vaiu-able prognostic informationabout Ihe oufcome of regen-erafive therapy Growth foctorsand other adjunctive compo-nents of regenerative therqpyhave the potential to increasethese criticai dimensions andmake regenerotive therapymore predictable in largerdefects.

This study sample was pri-mariiy from Coucasian pafients;therefore, the data may notapply to all rociai groups. Thisdata does, however, providereference measurements fortherapeutic appiicafion withinthe iimits of the sample studied.

Additionai clinicai reseorch isneeded to define critical furca-tion dimensions for regenerativeperiodontai therapy.

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Acknowledgments References

The authors gratefuiiy ocknowiedgethe donation of extracted teeth by DrsBen Strong and James SIrong, Taylors-ville, Kentucky. Extracted teeth donoledbv Dr Steven Sutley, Chief Of Orol andMaxiliofacial Surgery. Ireland ArmyHospitai, Ft Knox, Kentucky are alsogratefully acknowledged. This studywould not have been possible withouttheir help in procuring the extractedteelh.

1. Grant D. Stern I. Everetf F. Periodontics.SI Louis: Mosby 1979:785-786.

2. Lindhe J, Nyman S. The effeot ofploque confroi and surgicai pockete i Im i nation on the establish meni andmaintenance af periadontal health:A longitudinal study in coses otdduonced diseose. J Clin PerioOontoi1975;2(2):ó7-79.

3. Carranzo F. Glickmon's Clínico!PerioOonlology. Phiiodeiphja: WBSaunders, 1990:2ö3,

4. Tornow D, Fletcher P Ciassification ofthe verticol component of furcatianinvoivemenl,J Periodontoi 19Bil;55(5):283-234.

5. Pontoriero R. Lindhe J. Nymon S.Karring T. Rosenberg E, Sonovi F.Guided tissue regenerotion in theIreotment of furcation defects inmandibular molars A clinical studyot Degree ill involvements. J ClinPeriodonlol 1989:ló(3):l70-174.

ó. Mehlbauer M improved ClosureRote of Class III Furcations withPhysicaiiy Assisted Cell Migrationand Resorbable Membranes (thesis).Univ of Louisville. 1995.

7. Pepeiassi E. Bissada N, Greenweii H,Faroh C. Doxycyline-tricaioiumphosphofe composite groft facili-tates osseous heoling in advonoedperiodontai furootion defeots. JPeriadontoi 1991:62{2):1OÓ-115.

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