european journal orthodontics vol[2]. 18 n. 1 año 1996 pag 2

8/13/2019 european journal orthodontics vol[2]. 18 N. 1 ao 1996 pag 2

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Europt an JOll rnal olOrtl lOdont ics 1 8 ( 1 9 96 ) 2 7 -4 0 l O 1 9 9 6 E ur op ea n O rt ho do nt ic S oc ie ty

r.I.

I

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Significance of the cant of the posterior occlusal plane inClass 11division 1 m alocclusions

K en ji F ush im a Yu ta ka K ita mu ra H iro aki M ita S ad ao S ato Yos hii S uz uk iand Young H KimD epartm ent ofOrthodontics Kanagawa Dental College, Yokosuka, Kanagawa, Japan, and*Weston , Massachuse tt s, USA

SUMMARYIn studying a groupof f if ty adult femaleswith C lass 11division 1 m alocclusion, itwas evident that the skeletal problems of this malocclusion involved small, retruded man-dibles accompanied by backward rotation. This skeletal pattern was considered to be influ-enced by the vertical dimension of the upper dentition in the buccal segment for mandibularfunction. .

The anterior and the posterior occlusal planes were examined to gain a detailed assess-m ent of the relationship between the dental and the skeletal patterns. The findings indicatedthat the steep cant of the posterior occlusal plane was strongly correlated with the following:1. Small, retruded mandible with backward rotation as the skeletal pattern.2. Short vertical height of the upper second molars and distal inclination of the upper

m olars as the dental pattern.The increased vertical height of the lower second premolars was found to be related tobackw ard rotation of the m andible.

In treating skeletal Class 11division 1 malocclusions, this study indicated that control ofthe vertical dim ension of the posterior teeth is extrem ely im portant.

Introduction

In o rth od on tic tre atm en t, cran io fac ia l g ro wth -l d k l l bl k l l i

I

I

the right and left prem olars which interferedw ith th e o cc lu sio n. F ush im ael a l. ( 19 89 ) e xa m-in ed th e v ertical h eig ht o f rig ht a nd le ft p oste rio r

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r. 28ted. In reality, the cant of the occlusal planelinked w ith the occlusal surfaces of posteriorteeth is steep (Fig. lA). In a case with a flato cc lu sa l p la ne (F ig . lB ), th e an te rio r m ov em en tof the mandible leads to separation of theposterior teeth, since the cant of the occlusalplane is of a sufficient degree in relation to thesagittal condylar path. O n the other hand, in acase with asevere occlusal curvature in theupper dentition (Fig. l C ), the posterior disclu-sion does not occur in anterior movement ofthe m andible beca use the difference of inclina-tions betw een the posterior occlusal plane andthe sagittal condylar path is smal\. In suchin cide nc es, the p re se nce o f cu sp al in te rfere ncein the terminal molars invariably preventsanterior m ovem ent of the m andible or invites a

temporomandibu la r dys func tion .S everal studies have stated that an excessivecurve of Spee is characterized in Class II divi-sion l m alocclusions (Jarabak and Fizzel, 1972;Nanda, 1983). This characteristic occlusionmight affect its ow n skeletal growth pattern.The m asticatory function is characterized as ath ree -d im ensio nal m and ib ula r m ov em en t to th eocclusal surface of the upper dentition. M oreattention should thus be focused on the occlusalcurvature in the upper dentition. Langlade(1978) emphasized the importance of upperanterior occlusal plane control and stated that

K. FUSHIMA ET AL.

the goal of intervention m ust be optim um func-tion, not just straight teeth.

To f it th is c ha ra cte ristic f ea tu re o f th e o cc lu sa lplane of the posterior dentition, a functionalocclusal plane has been used thus far. In thisarticle, the occlusal plane w ill be considered astw o planes divided into the anterior and poster-ior segments. In this sense, it seem s clear thatth e re la tio nsh ip be tw ee n th e oc clusa l d evia tionand the skeletal pattern is closely related.

T he purpose of this investigation w as:(1) to determine the occlusal deviation in the

upper dentition using tw o param eters, theanterior and the posterior occlusal planes;

(2) to establish the m ean value and the normalrange of the two occlusal planes in thenormal populat ion;

(3) to exam ine the relationship betw een thosetw o param eters and the skeletal patterns inC la ss I I d iv isio n 1 m alo cc lu sio ns;

(4) to classify C lass II division l m alocclusionby the param eter of the occlusal plane;

(5) to com pare the skeletal pattern betw een thegroups of C lass II division 1 m alocclusiona nd no rm al o cc lu sio n.

M a te ria ls a nd m eth od sLateral cephalograms of normal occlusionsam ples and of C lass II division l sam ples w ere


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POSTERIOR OCCLUSAL PLANE IN CLASS Il MALOCCLUSION 29

u tiliz ed in th is stu dy. N orm al o cc\u sio n sam ple sof 35 adult fem ales with an average age of 23years 4 m onths (range 22-27 years) who pos-sesse d a cce ptab ly g oo d o cc \u sio n w ith ou t m iss-ing teeth were obtained from students ofK an ag aw a D en ta l C olle ge.

U ntreated C lass 11 division l m alocc\usionsamples of 50 adult females taken at 16 yearsofag e an d IVA stag e ofd en tal age w ere se\ected

fram th e files o f K anag aw a D en tal C ollege. T heaverage age of these subjects was 19 years llmonths with a range of 16-25 years of age.

C ep halo metric m easu rem en ts o n th e o cc\u sa lp la nes, a s w ell a s th e sk ele ta l an d d en tal p attern sw ere o bta in ed u sin g th e fo llo win g c riteria.

Occ/usal planes

l. Anterior occ\usal plane-a line drawn fromthe incisal edge of the upper central incisorto the cusp tip of the upper second prem olar.

2. Posterior occ\usal plane-a line drawn framthe cusp tip of the upper second prem olar tothe midpoint of the upper second molarat th e o cc\u sa l su rface .

T he F rankfort horizon tal (FH ) plan e w as deter-m ined u tilizing anato mical po rion an d orbitaleas referen ce p oin ts (R ic ketts, 1 96 0).

Measurements (Fig. 2 )

A -O P: th e a nterio r an gle b etw een th e an te rio rocc\usal plane and the FH plane. W hen the

anterior occ\usal plane slopes upw ard and for-ward in re\ation to the FH plane, the angle isread as m inu s.

P -O P: the anterior an gle b etw een the p oster-ior occ\usal plane and the FH plane.

OP-diff.: the angular difference betweenA-OP and P-OP.

Skeletal pa ttern

Angular measurements (F ig. 3)1. M andibular plane angle (M P): the angle

between the mandibular plane and the FHplan e (D ow ns, 194 8).

2. Facial axis (FX): the angle between thefacial axis and the basion-nasion line(R ic ke tts, 1 96 0).

3. G onial angle (G O-A ): the angle betw een theposterior border line of the ramus and them a nd ib ula r p la ne .

4. Palatal plane angle (PP): the angle betweenthe palatal plane and the FH plane. A po si-tive value is given when the plane inclinesdownward and forward in relation to theFH plane (Kim , 1974).

5. Ramus inc\ination (RAM -I): the anglebetween the posterior border line of theramus and the FH plane.

Linear measurements (F ig . 4 )

1. Na perpendicular to A (A): the distance

,..


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I 30FH

Figure 4 L inear m easurem ents of the skeletal patterns.1. Na perpendicular to A (A). 2. Na perpendicular topogonion (POG). 3. Ramus height (RAM-H). 4.Mandibular length (MAND-L). 5. Maxillary length(MAX-L).

I j

from point A to the line drawn fromnasion perpendicular to the FH plane

(M cN am ara, 1983).2. N a vertical to Pog (PO G): the distance frompogonion to the line drawn from nasionperpendicular to the FH plane (M cN am ara,

)

K. FUSHIMA ET AL.

FH

Figure 5 Angular m easurem ents of the dental patterns.1. V I to FH. 2. Ll to MP. 3. FMIA. 4. V6 to FH. 5. V7to FH.

2. Ll to M P: the angle formed by the long axisof the low er central incisor and the m andib-ular plane (D ow ns, 1948).

3. FM IA: the angle formed by the long axis ofthe lower central incisor and the FH plane(Twe ed , 1 96 6).

4. U 6 to FH : the anterior-inferior angle form edby the long axis of the upper first molar andthe FH planeo


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POSTER IOR OC CLUSA L PLA NE IN C LA SS 11 M ALOC CLU SIO N

u tilized in th is stu dy. N orm al o cc lu sio n sam plesof 35 adult females with an average age of 23years 4 months (range 22-27 years) who pos-sessed ac cep tab ly g oo d o cclu sio n w ith ou t m iss-ing teeth were obtained from students ofK an ag aw a D en tal C olleg e.

U ntreated C lass 11 div ision 1 m alocclusionsamples of 50 adult females taken at 16 yearsof age and IVA stage of den tal age w ere selectedfram the files of K anagaw a D en tal C ollege. T heaverage age of these subjects was 19 years 11months with a range of 16-25 years of age.

C ep halo me tric m easu rem en ts o n th e o cclu salp la ne s, a s w ell a s th e s ke le ta l a nd d en ta l p atte rn sw ere o btain ed u sin g th e fo llo win g criteria.

Occ/usal planes

1. Anterior occlusal plane-a line drawn from

the incisal edge of the upper central incisorto the cusp tip of the upper second p rem olar.2. Posterior occlusal plane-a line draw n from

the cusp tip of the upper second premolar tothe midpoint of the upper second molarat th e o cclu sal su rface.

T he Frankfort horizontal (FH ) plane w as deter-m in ed u tilizin g an ato mical p orio n a nd o rb italea s re feren ce p oin ts (R ick etts, 1 96 0).

Measurements (Fig. 2)A -O P: th e an terio r an gle b etw ee n th e an terio r

occlusal plane and the FH plane. W hen the

anterior occlusal plane slopes upw ard and for-ward in relation to the FH plane, the angle isread as m inus.

P-O P: the anterior angle betw een the poster-ior occlusal plane and the FH plane.

OP-diff.: the angular difference betweenA-OP and P-OP.Skeletal pa ttern

Angular measurements (Fig. 3)1. Mandibular plane angle (MP): the angle

between the mandibular plane and the FHplane (D ow ns, 1948).

2. Facial axis (FX): the angle between thefacial axis and the basion-nasion line( Ric ke tts, 1 96 0) .

3. G onial angle (G O-A ): the angle betw een theposterior border line of the ramus and the

m an dib ula r p la ne .4. Palatal plane angle (PP): the angle betweenthe pala tal plane and the FH plane. A po si-tive value is given when the plane inclinesdownward and forward in relation to theFH plane (Kim , 1974).

5. Ramus inclination (RAM-I): the anglebetween the posterior border line of theramus and the FH plane.

Linear measurements (Fig. 4)1. Na perpendicular to A (A): the distance

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II

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i{

1 : r ~ ~

~: ~

;

3 0

I

F H

II

II

Figure 4 tinear m easurem ents of the skeletal patterns.1. Na perpendicular to A (A). 2. Na perpendicular topogonion (POG). 3. Ramus height (RAM-H). 4.Mandibular length (MAND-L). 5. Maxillary length(MAX-L).

from point A to the line drawn fromnasion perpendicular to the FH plane(M cN am ara, 1983).

2. N a vertical to Pog (POG ): the distance frompogonion to the line drawn from nasionperpendicular to the F H plane (M cN am ara,1983).

A P difference (A P-diff.): the distance of

K. FUSHIMA ET AL.

FH

Figure 5 Angular m easurements of the dental patterns.1. UI to FH. 2. Ll to M P. 3. FM IA. 4. U6 to FH. 5. U7to FH.

2. LJ to M P: the angle formed by the long axisof the low er central incisor and the m andib-ular plane (D ow ns, 1948).

3. FM IA: the angle formed by the long axis ofthe lower central incisor and the FH plane(Tw ee d, 1 96 6).

4. U 6 to F H: the anterior-inferior angle form edby the long axis of the upper first m olar andthe FH planeo

5. U 7 to F H: the anterior-inferior angle form edby the long axis of the upper second molar


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Table 1 Estimation of random errors n = 25).

Coeff ic ient ofMeasurement SE r el ia bi li ty ( l o)

A-OP 0.49 99.72P-OP 0.54 98.84

M P 0.54 99.89FX 0.57 99.61GO-A 0.57 99.88RAM-I 0.45 99.84PP 0.50 96.51

A 0.53 98.63PO G 0.64 99.71RAM-H 0.34 99.93MAND-L 0.45 99.88MAX-L 0.43 96.83

UI to FH 0.69 99.66Ll to MP 0.59 99.85FMIA 0.67 99.78U6 to FH 0.74 99.67U7 to FH 0.85 99.75

UI-PP 0.30 99.74U5-PP 0.34 99.19U7-PP 0.36 99.27Ll-MP 0.20 99.74L5-MP 0.36 99.69L7-MP 0.32 99.69U6-PTV 0.77 98.11

POSTERIOR OCCLUSAL PLANE IN CLASS Il M ALOCCLUSION 31

FH

pp

Figure 6 Linear m easurem ents of the dental patterns.1. UI-PP. 2. US-PP. 3. U7-PP. 4. Ll-MP. 5. L5-MP.6. L7-M P. 7. U 6-PTV.

buccal cusps of the lower second molar tothe m andibular plane.

7. U 6-PTV: the distance fram the distal crow nsurface of the upper first molar to the PTv ertic al lin e (R ic ke tts, 1 96 0).

M e as ur em e nt e rr orA ll lateral cephalogram s w ere traced and theirlandm arks w ere digitized by the sam e investi

In Class 11 division l sam ples, the relation-ship betw een the skeletal and dental patternswas assessed by means of the coefficient ofcorrelation


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Nonnal Class 11 division 1

Measurement n Mean SO n Mean SO I-test

MP 35 27.8 5.54 50 31.2 7.04 NSFX 35 84.9 4.05 50 80.8 4.55 ...GO-A 35 125.0 6.51 50 123.9 7.10 NSRMA-I 35 82.8 3.79 50 87.2 4.91 .. .PP 35 1.8 2.75 50 1.5 2.82 NS

A 35 0.0 4.00 50 -0.2 3.17 NSPOG 35 -5.9 6.73 50 -13.2 7.05 .. .AP-diff. 35 5.8 5.45 50 12.8 6.18 ...RAM-H 35 64.2 5.89 50 60.2 5.89 ..MANO-L 35 124.5 5.33 50 117.4 5.97 ...MAX-L 35 50.4 3.72 50 48.5 3.01 ..

..Significant at 5 per cent level; ..significant at 1 per cent leve ; . s ignificant at 0.1 per cent

le ve l; N S: n o s ig nific an t d iff er enc e.

,

~

I, 32 K. FUSHIMA ET AL.Table 2 Com parison of the skeletal pattens betw een C lass 11 division 1 group andn orm al o cc Iu sio n g ro up .

ev alu atin g th e d istrib utio n o f C lass 11 div isio n Isamples on the basis of I standard deviation(SO) of the norm al sam ple, it w as dem onstra-ted that the skeletal problems in the Class11 division l m alocclusion group were small(M AN O-L), retruded (PO G) m andible accom -panied by backward rotation (FX, RAM -l),an d su rprising ly, a sm all m ax illa (M AX -L ).

Dental pattern (Table 3 )T he m ea n o fth e an terio r o cclu sal plane (A -O P)

The distal inclinations of the upper first andsec on d m ola rs V6 to FH, V7 to FH) weresignif icant ly stronger P < 0.00 1). The verticalheight of the lower incisor (Ll-M P) was sig-nif icant ly larger P < 0 .0 1).

Relat ionships between the occ /usa l p lanes, den ta l

a nd sk eletal patterns in th e C la ss II divisio n 1malocc/usion group(Tables 4 and 5)I n e va lu atin g th e c or re la tio n c oe ff ic ie nt b etw ee nthe dental and the skeletal patterns in Class 11


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POSTERIOR OCCLUSAL PLANE IN CLASS 11 M ALOCCLUSION 33

Mandibular Plane AngleG on ial A ngle

Inler .. (dqru)

...50-58...)9._.50ll.5l-)9.2& J3.5I11.51-:1&...17 11.5t11.51-17.

Inter\'aal132.0 0-1 38. H

I H.25--1J2.00

111.50-125.25

11I.75--1I1UO

1 05 .0 0-1 1 1 .7 5

'M.25--105.oo

11Frcqucncy

10 10Frequeney

20

Faicial A xis

Intenal (dep'erl

.-E::_M _:1.0&-85.77.10-11.73.00---77.M69 73 .

01110Fnqucney

R am u s I nc li na ti on

Intenal (dqrft)

94.50-.-101.00

87._.5079.51-87.007UO 79.50

l.Frequency

JO

P alatal P la ne A ng le

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(a )10

Freqmcy20 .10

Poi nI AM andib ular L en gth

Intenal 11ft. I'.st-..A.$O'.50-6.502.50-'.500.50-2.50

.1.50-


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Normal Class 11 division I

Measurement 11 Mean SO 11 Mean SO (-test

A-OP 35 10.0 3.58 50 8.5 4.39 NSP-OP 35 14.9 3.85 50 18.3 4.73 ***OP-diff. 35 5.0 3.96 50 9.8 5.04 ***VI to FH 35 115.4 6.00 50 120.9 6.89 ***Ll to MP 35 94.6 6.40 50 99.6 7.89 **FMIA 35 57.5 6.53 50 49.3 7.61 ***U6 to FH 35 95.3 5.05 50 100.9 5.44 ***U7 to FH 35 99.9 6.94 50 107.5 7.24 ***UI-PP 35 30.1 2.45 50 30.2 2.47 NSU5-PP 35 26.5 2.02 50 26.7 1.67 NSU7-PP 35 21.8 2.37 50 20.5 2.33Ll-MP 35 44.7 3.01 50 46.9 2.85 **L5-MP 35 38.1 2.95 50 37.6 2.53 NS

.L7-MP 35 32.0 2.87 50 32.2 2.47 NSU6-PTV 35 19.9 5.22 50 18.3 3.28 NS

*S ig nif ic an t a t 5 p er c en t le ve l;**s ig nif ic an t a t I p er c en t le ve ;***s ig nif ic an t a t 0 .1 p er c en t

l ev el ; N S , n o s ig ni fi cant d if fe rence.

J

34 K. FVSHIMA ET AL.

Table 3 Com parison of the dental patterns between Class 11 division 1 group andn or ma l o cc lu si on g ro up .

Anterior Occlusal Plane(0.75) and U6-PTV (-0.46). In other words,a case with a steep posterior occlusal planewould likely have a distal inclination of theu pper m olars. P-O P also sh ow ed stro ng co rrela-

tion with a vertical height of the upper secondm olar (U7-PP) (- 0.65), while no significantrelatio nsh ip w as fo un d w ith the vertical h eigh tof the upper second prem olar (U 5-PP).

Inl 1 1 ')'7.75-2'.se14 17.7510.25-14.'.50-1'.25

2.75-6.582.75

10 211 O


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Normal S-POP

Measurement n Mean SO n Mean SO t-test

M P 35 27.8 5.54 23 33.5 6.64 ** *FX 35 84.9 4.05 23 78.6 4.21 ** *GO-A 35 125.0 6.51 23 123.5 7.00 NSRAM-I 35 82.8 3.79 23 89.9 3.76 ***PP 35 1.8 2.75 23 1.7 2.85 NS

A 35 0.0 4.00 23 -1.2 3.29 NSPO G 35 -5.9 6.73 23 -16.1 5.95 ***AP-diff. 35 5.8 5.45 23 14.7 6.26 ***RAM-H 35 64.2 5.89 23 57.7 5.63 ***MANO-L 35 124.5 5.33 23 IB.4 4.68 ***MAX-L 35 50.4 3.72 23 46.8 2.73 ***

* Sig nif ica nt a t 5 p er c en t lev el; * *s ig nif ica nt at I p er c en t lev el; ** *sig nific an t at 0 .1 p er c en tl evel ; N S : n o s ig nf ic an t d if fe re nc e.

Table 7 Comparison of the dental patterns between S-POP group and normalo cc \u sio n g ro up .

Normal S-POP

Measurement n Mean SO n Mean SO t-test

A-OP 35 10.0 3.58 23 9.7 4.92 NSP-OP 35 14.9 3.85 23 22.2 3.19 ** *OP-diff. 35 5.0 3.96 23 12.5 5.24 ** *U I to FH 35 115.4 6.00 23 120.0 6.99 *Ll to M P 35 94 6 6 40 23 99 2 8 55

1 36 K. FUSHIMA ET AL.Table 6 Comparison of the skeletal patterns between S-POP group and norm alocc \usion group .


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1

POSTERIOR OCCLUSAL PLANE IN CLASS II M ALOCCLUSION 37

the d iffe rence in U7-PP rose P < O . O O I despitethe lack of difference in U5-PP. The strongrelationship between P-OP and U7-PP wasalready found in Table 4. It could, therefore, bestated that a steep posterior occlusal planeis caused by a short vertical height of theupper second molar and not by an excessivevertical height of the upper second prem olar.

Discussion

In order to gain a better understanding of them orphological features of Class 11 division Imalocclusions, 50 adult fem ales w ith Class 11division I malocclusion were examined andcompared with 35 adult females with normaloc clusio n. It w as de mon stra te d tha t th e sk ele ta lproblem s of Class 11 division I m alocclusioninvolved a retruded m andible (P OG , A -P diff.),rotation of the mandible in a backward direc-tion (FX, RAM-I) and small mandible(RAM-H, M AND-L) (Fig. 7). The skeletalfeatures of C lass 11 division I w ere not charac-terized by overgrowth of the maxilla, but arestrained grow th of the m andible w ith a back-ward rotation. M cN am ara (1981) studied 277children w ith Class II malocclusion, and con-cluded that the m axilla w as in a neutral positionon average (point A to nasion perpendicular),and that mandibular skeletal retrusion (po-

The rel at ionship between occ /usa l p lane andmandibular posture

In tre ating ske le ta l C la ss II d ivision I m alo cc lu -sions, the advancement of the m andible with aforw ard rotation follow ed by condylar grow tha nd a da ptiv e r em od ellin g o f th e te mp or om a nd i-bu l ar joint are desirable in order to im prove theprofile, the m olar relationship, and the overjet.M echanics w hich cause a backw ard rotation ofthe m andible or exert the condyle load againstthe m andibular fossae should be avoided.

The mandibular position is influenced bythe vertical re1ationship of the dentition in thebuccal segm ents and the re1ationship betw eenthe occlusal plane of the upper dentition andthe inclination of the sagittal condylar path isanother aspect to consider (Dawson, 1989).Figure 9A shows that elongation of the pre-molars merely causes a backward rotation ofthe mandible around the hinge axis. In a casew ith a flat occlusal plane, as show n in Fig.98,if extrusion of the upper terminal m olar leadsto occlusal interference in the posterior den ti-tion, the m andible is able to adapt to an anteriorposition in order to evade the interference. Suchan anterior displacement of the mandible isaccom panied by a forw ard rotation beca use the

cant of the occlusal plane is flatter than that ofthe sagittal condylar path. It is, therefore, pos-sible to obtain occlusal contacts in anteriordentition, and occlusal stability with the


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r~='38

A

B

K. FUSHIM A ET AL.

eFigure 9 Schem atic ex plan ation of the vertical dim ensional influen ce of the posterior teeth on m an dibular p ostu re. A nye xtru sio n o f th e b uc ca l se gm en ts c au se s a b ac kw ard ro ta tio n o f th e m an dib le . (A ) T he e xtru sio n o f p re mo la rs m ere ly c au se sa back ward rotation of th e m andible around the hinge axis. (B ) In a case w ith a flat p osterior occlusal plane, th e m andibleis able to ad apt to an an terior position to evade the interference in the posterior d entition and to obtain occlusal stab ility.(C ) In a case w ith a steep p osterior o cclu sal p lan e, there is no an terior tooth contact an d n o occlusal stab ility in the anterio r

p ositio n o f th e m an dib le . N ote th at th e in clin atio n o f th e p oste rio r o cc lu sa l p la ne is c lo se to .th at o f th e sa gitta l c on dy la r p ath .. .sense as treatm ent of functional Class In. Forthis reason, the correction of a steep posterior

by anterior-inferior displacem ent, but also aforward rotation accompanied by descent of


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POSTERIOR OCCLUSAL PLANE IN CLASS 11 MALOCCLUSION 39

A BFigure 10 The occlusal plane and m andibular grow tho (A ) Im plant study by B j6rk and Skieller (1972)0 (B ) A case w ithfla t p oste rio r o cc lu sa l p la ne o (C ) A c ase w ith ste ep p oste rio r o cc lu sa l p la ne o

e

d isp la cem en t. T his sce nario is co nsid ered as o nepossible explanation for norm al m andibulargrowth which is largely dependent on changeof the occIusal planeo On the other hand, in acase with a steep posterior occIusal plane(Fig. 1OC), liule descent of the upper molarregion takes place, even in the presence offorward rotational growth of the maxi1la.C onsequently, m andibular grow th seem s to besuppressed and d irected m ore inferiorIy. Table6 shows the smalI size of the mandible(MAND-L, RAM-H) accompanied by back-ward rotation (M P, FX, RAM -I) in the

Avoid ing unfavourab le p rocedu re s such asClass 1I e las tics

In treating C lass 11 patients, C lass 11 elasticshave often be en used in order to eliminate anoverjet and establish a norm al m olar relation-ship. In practice, concern is focused more onth e co rrectio n o f th e an tero -p osterio r d ev iatio nby placing the upper incisors lingualIy and bysh iftin g th e lo wer m olars m esialIy. T he im po rt-

ant point is that the vertical changes take placein doing so. Such a treatm ent m odality shouldb e s cr utin iz ed c Io se ly p rio r to im p le me nta tio n.

Langlade (1978) stated that excessive use of


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40r==1 Conclusions

l. This study revealed that the skeletal prob-lems in Class II division l malocclusionswere affected by the fact that the m andibleis retruded, sm all, and ro tated in a backw ardorientation. The maxilla was found to besmall in s ize anterior-poster ior ly.

2. The anterior and the posterior occlusalp lanes were establ ished for thi s inves tiga tion .The normal mean of the former was 10.0degrees with a SD of 3.58, and the latter was14.9 degrees with a SD of 3.85. The norm alm ean of th e o cclu sal plan e d ifference w as 5.0degrees with a SD of 3.96.

3. It was found that a large number of Class 11d iv ision l m alocclu sion s h ad a steep po ster-ior occlusal plane and asevere occlusal cur-v ature in the upp er dentition.

4. T he steep can t of the posterior occlusal p laneshowed a strong correlation with a small,retrud ed m an dible w ith a b ackw ard ro tationas skeletal problems in Class II division lmalocc1usion.

5. A steep posterior occlusal plane was foundto b e co rre la te d stro ng ly w ith a sh ort v erticalheight of the upper second m olars.

6. The increased vertical height of the lowersecond prem olars w as found to be related tothe backw ard rotation of the m andible.

It has been demonstrated that the skeletal

K. FUSHIM A ET AL.

References

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16/16

T ab le 4 Correlation between the skeletal and dental patterns in the Class 11 d ivision 1 group. .o'..,tT1

Skeletal pat terns ~O

Denlal patterns MP FX GO-A RAM-I PP A PO G AP-diff. RAM-H MAND-L MAX-L ~O

0.39.. -0.51... 0.11 0.38.. 0.48 . 0.03 -0.54 . 0.60 . -0.32 -0.40.. -0.08(')

A-OP (')P-OP 0.65. -0.65... 0.30 0.50 . 0.18 -0.29 -0.63 . 0.56... -0.65... -0.69 . - 0.44.. rc::OP-diff. 0.28 -0.17 0.18 0.14 -0.25 -0.30 -0.12 0.00 -0.33 -0.30 -0.35 'UI to FH -0.53. 0.58... -0.20 -0.44.. -0.31 -0.02 0.62... -0.71 . 0.36 0.35 0.04 rLI to MP -0.50 . 0.33 - 0.46... -0.06 0.33 0.27 0.16 -0.05 0.34 0.06 0.33 .rFMIA -0.39.. 0.36.. -0.21 -0.25 -0.43.. -0.22 0.48. -0.64 . 0.39 0.35 -0.17 >U 6 to FH 0.54... -0.48... 0.33 0.29 0.31 -0.20 -0.56... 0.53... -0.57... -0.62 . -0.25 ZtT1U 7 to FH 0.43.. -0.42 0.18 0.35 0.25 -0.24 -0.52 . 0.45.. -0.57. -0.69 . -0.34 -UI-PP 0.45 -0.46 . 0.26 0.25 -0.29 0.16 -0.33 0.45.. -0.16 -0.05 -0.04 (')U5-PP 0.22 -0.23 0.09 0.17 -0.27 0.10 -0.11 0.17 0.07 0.17 0.04 rU7-PP -0.32 0.28 -0.23 -0.13 0.09 0.18 0.19 -0.13 0.50 . 0.49.. 0.42 >

'LI-MP 0.46 . -0.44 0.28 0.26 0.02 -0.18 -0.46... 0.45.. -0.11 0.11 0.00 'L5-MP 0.32 -0.40.. 0.05 0.38.. 0.15 -0.16 -0.48... 0.47... 0.10 0.16 0.13 ::::L7-MP -0.21 -0.15 -0.54 . 0.47... 0.12 -0.29 -0.24 0.12 0.47 . 0.09 -0.06 ;:U6-PVT -0.20 0.41 0.06 -0.37 -0.39.. 0.47 . 0.54... -0.37.. 0.18 0.48. 0.40. >r

O S ig nific an l a t 1 p er c en l le vel; . s ig nifica nt a l 0 .1 p er c en l le ve .

(')(')rc::'Oz

Denta l pa tt erns

Occlusal planes UI lo FH LI to MP FMIA U6 to FH U7 lo FH UI-PP U5-PP U7-PP LI-MP L5-MP L7-MP U6-PTV

A-OP -0.62... 0.30 -0.67... 0.48... 0.29 0.43.. -0.15 -0.21 0.12 0.21 0.09 -0.38P-OP -0.25 -0.24 -0.36.. 0.81... 0.75 . 0.26 0.02 -0.65 . 0.18 0.05 0.10 -0.46.OP-diff. 0.30 -0.49... 0.25 0.35 0.45.. -0.13 0.15 -0.42 0.06 -0.14 0.01 - 0.1O

Table 5 C orre la tio n b et we en t he o cc lu sa l p la ne s a nd th e d en ta l p att erns in th e C la ss 1 1 di vi sio n 1 g ro up .

Sig nif ic an t a l 1 p er ce nt le vel; ...s ig nific an t a l 0 .1 p er c en l lev e .

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european journal orthodontics vol[2]. 18 n. 1 año 1996 pag 2

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