EVALUATION OF DENTOALVEOLAR COMPENSATION IN VARIOUS SKELETAL DYSPLASIAS - A CEPHALOMETRIC STUDY

Dr. Avesh S~1ch.1n

Abstract :

Authors:

Dr. Avesh Sachan, B.D.S, M.D.S. Senior Resident, Department of Orthodontics, Faculty of Dental Sciences, IMS, B.H.U. Varanasi.

Dr. Vijay P. Sharma, B.D.S, M.D.S. Professor and Head, Department of Orthodontics and Dentofacial Orthopedics, Chhatrapati Shahuji Maharaj Medical University, Lucknow.

Dr. G.K. Singh, B.D.S, M.o.S. Associate Professor, Department of Orthodontics and Dentofacial Orthopedics, Chhatrapati Shahuji Maharaj Medica l University, Lucknow .

Dr. Gyan Prakash Singh, B.D.S, M.D.S. Assistant Professor, Department of Orthodonti cs and Dentofacia l Orthopedics, Chhatrapati Shahuji Maharaj Medica l University, Lucknow.

Dr. T.P. Chaturvedi, B.D.S, M.D.S. Professor, Department of Orthodontics, faculty of Dental Sciences, IMS, B.H.U. Varanasi.

Corresponding Author:

Dr. T.P. Chaturvedi, Professor, Faculty of Dental Sciences, Institute of Medica l Sciences, Banaras Hindu University, Varanas i 22 1 005, U.P. (India). E-mail : tpchaturvedi @rediffmail.com

The aim of this study was to evaluate and compare dentoalveolar compensations in various skeletal dysplasias

Methods: The sample consisted of 130 lateral head cephalograms of subjects age ranged between 15-24 years with a mean age of 19.5 years .. The sample was divided into four groups according to antero-posterior skeletal relationships as follows-Control

Control: Group comprising Normal occlusion and other three groups were of different malocclusions. Groupol - comprising of Skeletal Class-I malocclusion, Group-II - comprising of Skeletal Class-II malocclusion and Group-Ill-comprising of Skeleta l Class-III malocclusion based upon the Wit's appraisal, APP-BPP measurement and IJ-angle measurement, collectively. In this study dentoalveolar linear and angular measurements have been measured on the traCing of lateral head Cephalogram.

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Results: Among the angular variables Max.l to NA, Max.1 to SN, significantly higher in Group­III and Group- II as compared to Control Group and Group-I wh ile Md.1-SN and S-N-Id. significantly higher in Group-III as compared to other groups and Md.1-NB, Md.1 -MP (IMPA) and OP-SN significantl y higher in Group-II and lower in Group-III as compared to other groups. Max.1- Mand.1 significantly lower in Group-II compared to other groups . Among the linear variab les Max.1 to NA significantl y higher in Group-II and Group-III as compared to Control Group, w hile Max. 1 to N-pog., Md.1 to NB, Md.1 to N-pog, sign ificantly higher in Group-II and significantl y lower in Group-III. Conclusions: In skeleta l Class-II malocclusion upper incisors are proclined in the protrusive upper jaw, and lower incisor proclined in retrusive lower jaw, while in skeletal Class-III malocclusion lower incisurs are retroclined and upper incisors are proclined .

Key Words: Dentoa lveo lar compensation, Skeletal Dysplasias, J3-angle, APP-BPP and Wit' s appraisa l,

INTRODUCTION

Normal growth and development of face can attain and maintained no rm al occl usion and estheti cs because oro-fac ial equilibrium is maintained. Normal growth and development of jaws can be affected by various hereditary and environmental factors. The development of the upper and lower arches are not always perfect. Some physio logica l processes is needed to co-ordinate the erupt ion and position of the teeth rela tive to their basa l bones in order for a normal relationship between the upper and lower dental arches to be achieved and maintained. This mechanism is known as dentoa lveo lar compensation. For ex isting sagittal jaw discrepancies, compensatory incl ination of the maxi llary and mandibular incisors results in comprom ised dentoa lveolar and incisor relationships.

A better knowledge of dentoa lveolar compensation in di fferent skeletal pattern subjects may be usefu l to understand the orofac ial functi ons, diagnOS iS and treatment planning of individuals. The compensatory incl ination of the max illary and mandibular incisors try to attained in normal incisor relati onships in some cases des pi te some va r ia tion s in sag ittal jaw relati onships. The cant of the occlusa l plane trying adjusts sagittal relationships between the max illary and mandibular dental arches. Quantitative evaluation of the dentoa lveolar adaptation to jaw relationship would provide additional informati on for treatment planning.

Keeping this in mi nd thi s study was done with the aims and objectives of:

1. To eva luate dentoa lveola r compensa ti ons in va rious skeletal dysplasias.

2. Tn compare the dentoa lveolar compensations in various skeleta l dysplas ias.

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MATERIALS AND METHODS

The present study was conducled on 130 lateral head cephalograms of subjects age ranget! between 15-24 yea rs w ith a mean age of 19.5 years. The subjects was divided into four groups, Control Group, Group-I, Group-II and Group- III w ith di fferent ske letal malocclusi ons. The subjects of control groups ( normal occlusion ) were selected from the students of C.S.M. Medica l University, Lucknow, While thecephalograms nf the skeletal malocclusion Groups were obtained from the patient record files, and the patients attending the OPD of the Department of Orth odon ti cs and Dentofeciel Orthopaedics, Faculty of Dental Sciences, C.S.M. Medica l UniverSity, Lucknow.

The subjects was divided according to antero-posterior skeletal relat ionships as fo llows - Control Group comprising of 35 subjects w ith Normal occlusion and o th er three groups were o f d ifferent skeleta l malocclusiuns. Group-I - compris ing of 35 subjects wi th Skeletal Class- I malocc lu sion, Group-II -compri si ng of 35 subjects w ith Skeletal Class-II malocclusiun am.! Group-III - comprising of 25 subjects w ith Skeletal Class- III maloccl usion based upon the Wit's appraisal, APP-BPP measurement (Ram S. Nanda and Robert M.Merrill ) ' an d J3-a ngle measurement (Chong Yol Baik and Maria Ververidou, 2004)' co llecti vely. All these measurements were used to ensure the skelet,, 1 pattern s of the subjec ts (Fig. 1 }.Cephalometric Landmarks and Reference Plane used in the study given in Fig. 2,3,4.

The subjects of control groups were selected on the bases of clini ca l cxtlm inat ion and cepha lometri c anal ys is w ith followi ng featu res li ke Skeletal Class- I Pallern, pleas ing profil e, symmetr ica l face, Class- I molar relati onship, No rotations, No spacing, No crowding, Class- I canine relationship, normal Over jet and overbite, maximum intercuspation , No permanent

teeth miss ing, No history of orthodontic treatment and class-I skeletal pattern .

The subjects of malocclusion Groups were screened after clinical examination and following cephalometric parameter were used to access the skeletal pattern of Groups- I , GroupS-II and GroupS-III.

Group I : Skeleta l Class I malocclusion subjects were having

• Wit's appra isal (between 0 - 1 mm.)

• APP - BPP (2 mm - 8 mm).

• pangle between 27° - 35°.

Group II : Skeletal Class-II malocclusion subjects were having

• Wit 's appraisal more than 1.

• APP - BPP more than 8 mm.

• p angle less than 2r.

Group III: Skeletal Class III malocclusion subjects were having

• Wit 's appra isal less than 0 mm.

• APP - BPP less than 2 mm.

• p angle more than 35°.

The cephalograms were obtained over a un iversa l counter halancingtype of cephalostat w ith the Frankfort hori zontal plane para llel to the floor and the teeth in centric occl usion wi th relaxed lips. Kodak X-ray films (II" x '0") were exposed at 70 KVP; 40 mA for 1.8 seconds from a fixed distance of 60 inches. The lateral head cephalograms were traced on acetate tracing shE'ets 0.003 inch in thickness using a sharp 4H penci l over a view box using trans illuminated light in a dark room and any stray light rad iations were eliminated. Cranial registration marks were traced on the acetate tracing sheets after marking them on the cephalogram. Only Good quali ties of lateral cephalograms were taken for the study.

If the right and left structural outl ines were lacking in superimposi tion on each other, then the average between the two was drawn by inspection and there after cephalometric points were located to the arbitrary line so obta ined. The linear and angular measurements were made to the nearest 0.5 mm and 0.5° respectively with the help of sca le and protractor.

Statisti cal analysis Reliability of measurement was tested by doing double determ inations test and no stati stica ll y signi ficant differences was observed . The Dentoa lveolar linear and

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angular measurements (Fig. 5,6) have been measured over the traCing of lateral head Cephalogram and the Mean values and Standard Dev iation of d ifferent angular and linear variables were calcu lated within each Group. There after inter-group comparision of dentoa lveolar linear and angular measurements were done by student's 't ' test. The stati stica lly significant levels were predetermined at P <0.05, P <0.01, and P <0.001.

RESULTS Mean and standard deviation va lues of the Control group, Group- I (s keletal Class-I maloccl usion ), Group- II (s keletal Class - II malocclu sion) and Group-III (skeletal Class-III malocclusion) for the dento­alveolar angular measurement (in degree) and li near measurement (i n mm) parameters are presented in Table-I. The statistica l comparisons of Control group and malocclusion groups are presented in Table-II and inter group compari son of malocclusion groups are presented in Table-III.

Among th e D entoa lveo lar angul ar var iab les (Bar Di agram-1 (aJ, 1 (b)) the mean value of the M ax .1 toN A fo und to be ve ry sign i fi ­cantly higher in Group-III (p<O.OOl) and just cantly higher in Group-II (p< 0.05) as compared to Control Group and Group-I. Max .1 to SN, found to be higher very significantly in Group-III (p<O.OOl ) as compared to Control Group and Group-I while Max.1- Mand.1 ( Inter-incisa l angle) found to be lower very signifi cantly in Group-II (p<O.OOl ) as compared to Control Group and Group-I. Md.1-N B found to be very sign ifica ntly higher in Group-II (p<O.OOl ) as compared to Group-I and just signi ficantl y higher in Group-II (p< 0.05) as compared to Control Group while Md.l -NB found to be very significantly lower in Group-III (p<O.OOl) as compared to Control Group and signi ficantly lower in Group-III (p<O.Ol ) as compared to Group-I. Md.1-MP (IMPA) found to be very significantly higher in Group-II (p<O.OOl ) as compared to Group- I and significantly higher in Group-II (p<O.Ol ) as compared to Control Group while Md.l -MP (IMPA) found to be very significantly lower in Group-III (p<O.OO l ) as compared to Contro l Group and Group-I. Md.1-SN fo und to be very signifi cant ly lower in Group-II (p<O.OOl ) as compared to Contro l Group and Group­I. S-N-Id. found to be significantly higher in Group-III (p<O.Ol ) and very Signifi cantly lower in Group- II (p<O.OO1) as compared to Control Group whi le S-N­Id. found to be very signifi cantly higher in Group-II I (p<O.OO 1) and lower in G roup-II (p<O.OO1) as compared to Grou p-I. OP-SN fo und to be very signi ficantly higher in Group-II (p<O.OO l ) as compared to Control Group.

Among the Den toa lveo lar linear va ri ables (Bar Diagram-2) Max. l to NA significantly higher in Group­II and Group-III (p<O.Ol) as compared to Control Group and just significantly higher in Group-III (p< 0.05) as compared to Group-I. Max. l to N-pog. found to be very signi ficantly higher in Group-II (p<0.001) and very signifi cantly lower in Group-III (p<O.OO l ) as compared to Control Group and Group-I. Md.l to NB found to be very significantl y lower in Group-III (p<O.OOl ) as compared to Group-I and found to be significantly higher in Group-II (p<O. 01 ) as compared to Control Group while found to be just significantl y lower in Group-III (p<0.05) as compared to Control Group. Md.l to N-pog, found to be just significantl y higher in Group-II (p< 0.05) as compared to Control Group and found to be just significant ly lower in Group-l lI (p< 0.05) as compared to Control Group and Group-I. Maxil la ry alveular depth (MxAD) found to he just significantly lower in Group-IHp< 0.05) as compared to Control Group and Mandibular alveolar depth (MdAD) found to be significa ntly lower in Group-llI(p< 0.01) as compared to Contro l Group and just significant ly lower in Group-III (p< 0.05) as compared to Group- I.

DISCUSSION

Eva luati on of dentoa lveolar compensation in different skeletal patterns may be usefu l to know the limit of the natural dentoa lveo lar compensat ion, trea tment plan ning, treatment success and ior post-treatment stabi lity.Solow 1966', 19804; Bjork and Skieller 19725;

Ish i kawa et ai. , 2000 ' have sugges ted that malucclusions resul t from insufficient dentoalveolar compensati on to va riations in fac ial patterns.

The age group consi dered in this study was 15-24 years with the mean age 19.5 years, w hich represented a stable period in the growth and development of craniu­facia l compl ex .The ske letal malocclu sions were divided on the basis of Wit 's analys is (A. Jacobson, 1975)', APP-BPP measurement (Ram S.Nanda and Robert M.Merr ill , 1 9Q4)' and p-angle measurement (Chong Yo l Baik and M ar ia Ververid ou, 2004)' Collectively for better understanding of skeletal pattern. The use of occl usa l plane was, supported in earlier studies by Jenkins (1955)6, Moore (1959)9 and Harvold (1963)'0

In the investigation undertaken by Nanda and Merrill in (1994)' , the distance between the projections from points A and B on the palatal plane was found to be the best ind icator of sagittal jaw relationship. Now Beta angle (Chong Yol Ba ik and Maria Ververidou, 2004), used for assessment of skeleta l dysplas ias w ith grea t

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success as does not depend on any crania l landmarks or dental occlusion.

The present study shows that the Max.l to NA (Angle) increased in Group-III (Skeletal Class-III )(31 .28±S.21) when compared with skeletal Class-I pattern (23 .60± 6.0 5) As repo rt ed by Ho ld away (1 Y56) " a compensatory mechanism allowed a good occ lusion to be achieved in a subject with an acceptable fac ial balance related to vari ous skeletal api cal bases. This relati onship is achieved by relative tipping of incisors and change in occlusa l plane.

Similarly Coben (1955)" and Bibby (1980)" reported that to reduce the anterioposterior discrepancy between maxillary and mandibular apical bases, Class- III cases tried to achi eve proc lined max i llary inc isors. As opposed to the present study the procl inat ion of max illary incisurs decreased in Class- III by Denovan's (1954)14.

In the present stu dy for M ax.- l to SN ( angle ) highly signi ficant difference ('p'<O.OOl ) in mean va lue were found between Control Group (106.60:t5.04) w ith Group-III 111 2.n4",6.4Qi, Group-I (1 06.03±6.14) with Group-III (11 2.64±6.40).

Similar results were found by Bibby (1980) " · He also found that upper incisors incl ination was significantly different between all three skeletal Class-I , Class-II , Class-III malocclusion. According to him skeletal Class­III maloccl usion have relative ly proc lined upper inc isors and skeleta l C lass- II hav ing re lati vely retrocl ined maxillary incisors.

On the other hand, Ishikawa et ai. , (1999)' reported th at the upper inciso rs incl ined more lab iall y in negati ve overj et cases and upper 1 to SN is most appropriate method of describing dental compensation quantitati vely.S imilarly Antonija and Vorga (2003) 15 suggested upper incisors protrusion in relati on to max il lary base in subj ec ts w ith ma ndibul ar prognathi sm. These find ings suggested that the proc lin ati on of upper incisors as a result of dentoalveolar adaptation, which is characteristic for Class-III relati onship also supported the present study.

In the presen t study stati sti ca lly signifi cant di fference to a level of p<0.01 were found for Max. 1 to NA (Linear) measured when compari son made between Control Group (6.64± 1.34) w ith Group-II (7.53±2.95), between Control Gruup (6.64±1 .34) with Group-III (8.02:t2.83). The findings of present study indica ted that upper incisors are positioned forward in re lation to N-A line in skeletal Class- II and skeletal Class-III malocclusion as compare to Control Group, w hich proves th e procl ination of max illary incisors.

In the present study no statistica lly signifi cant difference was found in mean va lue of Max.1 to NA (Linear) between Group-II (7.53±2.95) and Gro up- III (S.02±2.83), which indicated that maxil lary incisors are positioned forward in Class- II and Class- III malocclusion in relation to N-A line in maxilla. In Class­II malocclusion maxilla is pos itioned forward while in Class-III malocclusion maxilla is positioned backward in relation to cranial base but linear distance betwccn upper incisors and N-A line shows no stati stica lly difference in mean value between Class-II and Class­III malocc lusion , that proves dento-a lvco lar compensation in class-III malocclusion.

The findings of study of Ismail Ceylan (2003)" also supported the results of present study. According to h im Maxl to N .A. (m m) meas urement showed statistica ll y significant difference among the different overjet (positive and negative overjet) groups. Mayury Kuramae (2005)" also evaluated high mean va lue of Max 1 to NA (Linear) for skeletal Class-III ma locclusion, reflected a denta l compensation, wh ich also supports the present study.

In the present study Max. l to N-Pog (Li near) value between Control Group and malocclusion groups were found very highly significant at the level of 'p' <0.001 between Control Group (10.20±2.64) wi th Group-II (14.39±3.41) between Control Group (1 0.20±2.64) with Group-III (3.80±4.49), between Group-I (10.1 0±3.18) with Group-II (14.39±3.41), between Group I w ith Group-III, between Group-II with Group-III.

Similarly Riedel (1952)26 measure the anterioposterior pOSition of the upper incisor to the facial plane. That was recorded with an average of between 5.5 and 6.Smm.in Patient exhibiting normal occlusion. In class III malocclusion maxillary incisors were found far behind this point. Maxi llary incisor were found about twice the distance anterior to the facial plane in the patients having class-lI,d ivl malocclusion.

In the present study when intergroup comparison were made between Control Group (normal occlusion) and various malocclusion groups. The differences in mean value of Md.1 to NB angular variable found were highly signif ica nt (p<O.OOl) between Control G ro up (28. 10±4.S6) with Group-III (2 0. 96±8.61) between Group-II (30.33±6.63) with Group-III (20.96±8.61). The di fference in mean value of Md.l to NB angular variables were also sign ificant (p <0.01) between Group-I (26.23±5.94) and with Group-II (30.33±6.63), between Group -I (26.23±5.94) w ith Gro up- III (20.96±8.61).

The present study is supported by Marcos Roberto et aI. , (2005)18 on skeleta l Class- II malocclusion .

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According to him the angular measurements for the mandibu lar incisors to NB present statistically signifi cant difference, showi ng mandibular incisors labia lly inclined.

The study of Bibby R.E. (1980)1J also supported the present study, according to him a consistent pattern appears to be operating which retroclines the lower incisors in the protrusive mandible of Class-III types. The pattern of lower incisors in Class-II malocclusion i s proc linat io n of lower incisors than Class-I malocclusion.

In the present study very high Sign ificant difference for Md.1 to MP at the level of <0.001 were found when the mean va lues of Group-III (85 .84:1:11.82) were compared with Control Group (97.86 ± 4.34), Group­I (94.95±7.28) and Group-II (1 01.28±5.13).There is also Significant difference to a level of p<O.Ol between Contro l Group (97.86±4.34) with Group-I I (101.28±5.13) .

Ismail Ceylan (2003)" who proved in their studies that Mand.l to MP angle statistica ll y sign ificant different among different overj et pattern. Bibby (1980)1J eva luate L 1 to Md. plane angle in various skeletal pattern Class-I (94.45±7.30) Class-II (97. 14±7.39) and Class- III (89.2 8±6.90).

Similar results were found by Antanija & Varga (2003)", they stated that IMPA angle represents the degree of protrusion and retrusion of lower incisors in relation to mandibular base. In relation to eugnathic patient (920), patients with mandibular prognathi sm have statistica lly sign ifica nt value of decreased for this angle (83.540) as a resu lt of dentoa lveolar adaptation. Tweed (1954) 19stated that the position of the lower incisor is vertica l for a stable maxi llo-mandibular relationship and their position in relation to the mandibular base w hich should be 90', is of great importance.

In the present study Md.l to SN shows statistica lly very highly signi iicant difference (p<O.OO1) in mean value when intergroup comparison were made between Contro l Grou p (52.18 ± 6.53) with Group-I I (44.9S±6.88), and Group-III (62.40±9.S1), between Group-I (52.53±7.21) w ith Group-II (44.95±6.88), and Group-III (62.40±9.51) between Group-II (44.95±6.88) w ith Group-III (62 .40±9.51). That is mandibular incisors are ve ry proc lined labia ll y in skeletal Class- II maloccl usion, w hile these were found uprigh t or retroclined in skeleta l Class-III malocclusion, Which was similar to the results found by Ohyama (1978)'·, R.B. Bibby (1980)1J, Sebata et aI., (1969)" who proved in their studies that lower incisors are relatively upright or retrocl ined in Class- III malocclusion due to dento­alveolar compensation.

Ishikawa and Nakamura (2000)" eva luated the dento­alveolar compensation in negati ve overjet cases by measuring sN-L 1 angle_ The sN-L 1 angle for normal overjet group were (S6.30±6.30) while for negative overjet were (60.40±9.20) these finding supports the present study. Shim H_Y. and ChangY.! . (2004)" were also found increased L 1 to sN angle in mandibular prognathism that is retrocli ned lower incisors. This study also supports the present study.

Highly significant statistica ll y difference (p~O .OOl ) in Md. l toN B ( linear ) were found, When comparison of Group III (S.20±2 .49) were made wi th Gro up I (6.93±2. t 9) and Group II (8.01 ±2.86) . Whil e

significant di fference (p~O .Ol ) were found between control group wi th Group II. These findings indicated forwa rd pos itioning of mandibular incisors in skeletal class ll maloccl usion and backward posi tioning in skeleta l class lll malocclusion. This was supported by Antonija and Vorga (2003)1', who found that the va lue of Md. l to NB linear (3.35mm) suggest the retrusion of mandibular incisors in relati on to mandibular apical base, in mandibular prognathic patients, because the va lue for eugnathic patients is 4.5mm. It is also a part of dentoa lveolar compensation.

The present stu dy showed signif ica nt ( p~O. Ol )

difference in Md. l to N pog.(l inear), when comparison were made between Group-II (6.46±3.80) wi th Group­III (4.00±2.86) while just signifi cant di fferences were fou nd in mea n va lu e between co ntro l Group(5.02±2.47) and with Group-II, between control Group with Group-III, between Group-I(S.90±2.69) w ith and Group-III. Findings suggested the forward posi ti on ing of ma nd ibul ar inciso rs i n Class- II malocclusion and backward positioning of mandibular inc isors i n Class- III malocc lu sion as a dent al compensation.

In the present study, Highly significant difference in the mean va ilies of M ax.l - M and.l linteri ncisa l angle) bei ng found at the level of 'p'<O.OOl ,when Group-II (11 6.25+ 10.1 0) compared w ith Co ntro l Group (127.51 +7.22), Group-I (127+10.94) and Group-III (130.24+ 12.50).

As the interincisal angle shows a decrease va lue in Group-II (skeletal Class-II malocclusion) and increase in Group- III (Ske leta l Class- III maloccl usion)as compared to Control Group and Group- I, Th is was supported by Ismai l Ceylan (2 003)1', who found that measurements of interincisa l angle showed stati stica lly signifi cant, decrease in pos itive overj et groups and increase in interincisa l angle in negati ve overjet groups. The present study is also supported by Antanija and Varga (2003)1" in their investigati on a mean va lue of

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interincisa l angle 136. 130 for prognathic patients and mean va lue of 131.50 for eugnathic pati ents. The in lerincisa l angle was more in the study of Antanija & Vorga than the present study probab ly due to d ifferent racia l and ethanic groups.

In our study, when intergroup comparison were made between Control Group, Group-I, Group-II and Group­III for angular variable SoN-Pro The mean va lue of S-N­Pr did not show any statistica lly Significant difference in between groups. s-N-Pr angle remain almost same in all sagittal skeletal pattern by the high capaci ty of adaptati on of the alveolar structure between upper central incisor teeth .

The present study is supported by Tallgren and Solow (11)1) 1)4 they concluded that alveo lar structu re is a fl ex ible area located between the facial skeletal and occlusal dynami CS. Alveolar structure tr ies tu establish and maintai n normal relati onship in different skeletal di spl as ias . Thi s i s so ca ll ed "dentoa lveo lar compensatory mechani sm" spontaneously made skeletal deviation . On the other hand the alveo lar stru c ture i s a lso in strumental in contro lling deve lopment of the jaws . Th e high capac ity of adaptation of the al veolar structure accounts for the fact that it does not onl y change wi th skeletal maturation (Mirzen Arat, 200 I )I"

s-N-Id angle shows very high statistically Significant djfference in mean va lue when comparison is made between Control Group (83.37±3.68) wi th Group-II (78.83±3.3 7), between Group-I (81. 90±3.75) w ith Group-II (78.83±3.37), between Group-I (81.90±3.75), w ith Group-II I (86. 18±4.4S ), between Group-II (78.83±3.37) w ith Group-III (86.1 8±4.4S).

In skeletal Class-II malocclusion S-N-Id. Angle is smaller as compare to Control Group and Class-I malocclusion dlle to mostly retrognathi c mandible as compare to cranial base. In skeletal Class- II malocclusion very much positi ve overj et indica tes inadequate dento­alveolar compensation . Infradentale, the alveolar poi nt which is present in mandible in severe skeletal Class-II malocclusion mandible is positioned much backward in relation to nasion poi nt. So, s-N-iel angle is small in Class- It malocc lu sion and dento-a lveo lar compensation is not properl y attained.

In skeletal Class-III malocclusion s-N-Id. is large, which is due to forward pos ition of mandible as compare to cranial base. In skeletal Class- III malocclusion there are chances of edge-to-edge bite or negative overj et presence and al veolus (lnfradentale) p laced forwardl y. So, increased S-N-Id angle in Class-III malocclusi on indicate inadequate dento-alveolar compensation.

OP-SN plane angle va lue between Control Group (12.77±3.96) with Group-I I (l7.09±4.4s) were found high ly significant at a level of 'p' <0.001 . Wh ich indicate severe canting of occl usa l plane in relation to cranial base. Th is canti ng of occlusa l plane may be because of dento-a lveo lar compensati on to attain normal occlusa l and incisa l relationship.

This is supported by the study of Ishikawa and Nakamura (2000)" indicated that for sag ittal jaw discrepancies normal incisor relat ionship can be attained by a combination of compensatory effects of the incisor incl ination and occlusa l plane angulation. This suggests the cli nica l importance of changing the occlusa l plane angulation in non-surgica l treatment of skeleta l ma locclusion.

Similarly Mitsui Miywki (2001)" was also stud ied that cant of occlusa l planes were strongly related to sagittal jaw relationship and played an important role in dento­alveolar compensation to obta in a normal incisor relationship and a Class-I molar relationship.

Maxillary alveolar depth (Mx.AD) is a di sta nce between shortest line above apex of max illary central incisors between maxillary mid sagitta l labi al and palatal alveolar cortical bone (Beckmann 1998)" (fig-4) .The mean va lue of Mx.AD in control Group was I S.S±4.00 in the present study.

When the mean and standard deviation va lues of MX.AD were compared in present study between Control Group wi th Group-I, Group-II wi th Group-III (malocclusion groups) the results were found to be almost insignificant in all intergroup comparison except in Group-II (skeletal Class-II malocclusion) at a level of 'p' <0.05 .

The present study is supported by Ismail Ceylan (2003)", who studied Mx.AD in va rious overjet Groups and found that Mx.AD does not shows stati stica ll y significant difference in between di fferent overj et groups.

Mandibular alveolar depth (Md.AD) is di stance between shortest line at apex of mandibular central incisors between mandibular mid sagittal lab ial and lingual alveolar cort ical bone. (Beckmann et aI. , 1998)". Mean and standard deviation va lue of Md.AD in Control Group was 9.29±1 .71 in the present study.

When inter group compari son were made for Md.AD in present study between control group, Group I, Group II and Group III, the mean value of Ma.AD shows sta ti stica ll y significant di fference in Group-III (skeletal Class-II I ma loccl usion) at a leve l of 'p ' <0.01 as compared to Control Group.

80

The findings of present study supported by Alka Singh (2003)" , who found no difference in Md.AD in Class­I and Class-II div .1 ma loccl usion. The significant difference in mean value of Group-III (7 .76±2.36), Control Group (9.29± 1.71) was supported by Nojima K. (1998)29 and Guo XX, & Wang c.L. (2005)'· who demonstra ted decreased M x.AD and in lingual incl inati on of symphys is in Class-III malocclusion.

Maxillary anterior alveolar and basal hei ght (Mx.AABH) is linear distance between mid point of alveo lar meatus of max ill ary central incisor and intersecti on between pa latal plane and max illary alveolar ax is (Beckmann et aI., 1998)27.

Wh en inter-gro up co mpa riso n were made fo r M xAABH, in present study between Control Group, Group-I, Group-II and Group-III. Mean of MxAABH did not show any sta ti stica lly sign ificant difference but shows a trend to less MxAABH in Class-III malocclusion and high value in Class-II maloccl usion.

The findings of present study is supported by Ismail Ceylan (2003)", Hua YM, Zhao BJ (2006)" and Bulent Baydas (2004)32, who suggested a increase MxAABH in pos itive overjet cases and decrease MxAABH in negative overjet cases. The findings are not signi ficant in present study probably due to low sample size.

Mandibular anterior alveolar and basal height (Md.AABH) is distance between mid point of alveolar mea tus of mandibular central incisors and intersection between symphysial surface and mandibu lar alveolar axis. (Beckmann et aI., 1998)27.

When inter group comparison were made between contro l Group, Group-I, Group-II and Group-III no statisti ca lly significant difference were found in mean va lue of Md.AABH in the present study. Th is study indicated that Md.AABH is not affected by skeleta l dysplsias.

The results of present study is similar as work done by Ismail Ceylan (2003)", who studied Md.AABH in di fferent overj et pattern and found no statistica ll y significant difference in mean va lue of Md.AABH .when intergroup comparison were done between different overj et groups.

Dentoalveolar compensation is mostly represented by procl inati on of upper and retrocli nat ion of lower dentoa lveo lar segment in ske leta l Class- III malocc lu sio n and proc lination of upper and procl ination of lower dentoa lveolar segment in skeletal class II malocclusion. A lthough presence of thi s compensatory process abnormal incisal relationship deve lops du e to in adequ ate dentoalveo lar compensation .

The present study was cross-sectional and soft tissue compensation was not considered. A further study with separa te male and female samples may be more informative for both sexes. Abnorma l Muscle activiti es and functions like, mouth breathing, tongue thrust,short lips and lip trap etc. should be investiga ted during development of skeletal dysplasias and malocclusion.

CONCLUSION

From this study, following conclusions may be drawn:

1. Dentoalvpnlar compensa tory changes in the position and ax ial inclination of the upper and lower incisors were found in Group- lI (ske letal Class- II malocclusion) and Group-lI l(skeletal Class­II I malocclusion).

2. In Group- II (skeletal Class- II malocclusion) upper incisors are proclined in the upper jaw, and lower incisor proclined in lower jaw.

3. In Group-III (ske letal Class- III malocclusion) a consistent rallern appears to be operating which retroclined the lower incisors and at the same time proclined the upper incisors as a compensatory process.

4. O P-SN found to be signifi cantl y higher in Group­II (skeletal Class-II malocclusion).

S. Maxillary alveolar depth (Mx.AD) found to be less in Group- II and Mandibu lar alveo lar depth (Md.AD) found to be less in Group-III as compared w ith Cnntrol Group.

REFERENCES

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81

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16. Ismail Ceylan, Ibrahim Yavur and Fatma Ars lan : Th e effec ts of overjet on dentoalveolar compensation. European/. of Orthodontics. 2001, 125:325- 330.

17. Mirzen Arat, Aysegul Koklu, Erhan Ozdiler, Meliha Rubenduz and Banu Erdogan.Cranio[aical growth and skeletal maturation a mixed longitudinal stud),. Ejo. 2001, 23(4): 355- 361.

18. M arcos Robert o de Frei ta s. Cep hal ometr ic charac teri za ti on o f skeletal Class- II, di v. l malocclusion in W hite Braz il ian subjects. I Appl Or,,1 Sci. 2005, 13(2) :198-203.

19. Tweed CH. The Frankfort mandibular incisor angle (FMIA) in orthodontic diagnosis. treatment planning and prognosis. Angle Or/hod 1954.24:121-169.

20. Ohyama H : A consideration of incisor axis in orthodontic treatment. I lap Orthod. 1978.37: 195-204.

21. 5eba ta M, Kikuchi m, oga mi K. Studies for establishing basis of construction of harmonious profile of Japanese. I lap Or/hod. 1969, 28:61-67.

22. Ish ikawa H, Nakamura S. Dentoalveo lar compensation in negative overjet cases. Angle Orthodontist. 2000, 70: 145-1 48.

23. Shim H.Y. Chang Y.J .: Dentoalveolar compensation according to skeletal di screpancy in norma l occlusion. KoreanlOrthod 2004. 34(5):380-393.

24. Mitsui M iyaki. Ishikawa Hiroyaki. Tsukada Haruka. Kitazawa Shinichi. Iwasaki Hiroshi and l ida Junichiro : Quantitative anal),sis oi dental compensa tion ior va nations in sagi ttal jaw re lationsh ips . O rt hodontic. Waves. 200 1, 60(3): 172-175.

25. Mayury Kuramae. Cephalometric evaluation of Class-III malocclusion of a modified Tweed­Merrifield analysis. Braz. j. of Oral Science. 2005, VoI.(4): 680-684.

26. Riedel R.A. The relation of maxi llary structures to cranium in malocclusIon and in normal occlus ion. Angle Or/hod. 1952, 22:142-145.

1 . .... -! • • • ..,... 1_ .-,-

Fig. I: Method's Used far Skeletal Pattern

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27. Beckmann S. H, Kui te rt R.B. Prahl -Andersen. Alveolar and skeletal dimensions associated wi th overbite. AmI Or/hod. 1998, 11 3:443-452.

28. Alka Singh. A cephalometric evaluation of lower facial height and its relationship with dento-a lveolar vert ical dimensions. Thesis submi tted for the partia l ful fil lment of requirements for the degree of M.D.S. (Orthodontics) C.S.M. Medica l U niversit)'. lucknow. 2003.

29. Nojima K. akakawaji K, Sakamoto T. Isshikiy. Re lationshi ps between mandibular symphysis morpholog), and lower incisor inclinat ion in skeletal Class- III malocclusion requiringorthgnathic surgery. Bull Tokyo Dent Coli. 1998, 39(3) : 175-181.

30. Guo xx, Wang Cl, Wei F.l. Xuly. Kou B. Study of the incisive alveo lar structure in different vertical facial t)'pe5 between osteal Class-III malocclusion and normal occlusion. ShanghaiKau Qiang Yi Xue. 2005, 14(6) : 593-596.

31. Hua Y.M. Zhao B.J. Dentoalveolar characteristics in skeleta l Class I patients with excessive overjet. Zhonghua Kau Qiang Yi Xue Za Zhi. 2006, 41 (8):486-487.

32. Bulent 8aydas. Ibrahim Yavuz. An investigation of maxillary and mandibular morphology in different overjet grou ps : Aust Or/hod. 2004.20: 11 - 18.

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Fig. 2 : landmarks Used Ji1 the Study

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Fig. J : landmarks Used in the Study

I ...... ,:0 ..... : ....... ' ... lH J _,~_' · ~~ S.Md·ION~

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Fig. 5: Angular Measurements

83

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Fig. 4 : Reference PliJnes Used in the Study

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Fig. 6 : liner Measurements (in mm)

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Bar Diagram - 1 (aJ : Comparison of Dentoalveolar Angular Variables

be/ween Control Croup and Malocclusion Croups (Croup-I, Croup-II, Croup-///J

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Bar Diagram - 1 (b) : Comparison of Dentoalveolar Angular Variables

between Conlrol Croup and Malocclusion Croups (Croup-I, Croup-II, Croup-III)

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Bar Diagram - 2 : Comparison of Dentoalveolar Angular Variables between Control Croup and Malocclusion Croups (Croup-I, Croup-II, Croup-///J

84

Table-I: Mean and SD of Dentoalveolar Angular and Linear Variables in Different Groups

CONTROL GROUP- I GROUP- II GROUP- III

S. GROUP (N = 35) (N = 35) (N = 25) VARIABLES

(N = 35) No. Mean SD Mean SD Mean SD Mean SD

DENTOALVEOLAR ANGULAR MEASUREMENTS (in degree)

1. Max. 1 to NA 24 .1 4 3.37 23.60 6.05 27.34 7.83 31.28 5.21

2. Max. 1 to SN 106.60 5.04 106.03 6. 14 108.80 7.77 11 2.64 b.40

3. Max. 1 to Mand. 1 127.51 7.22 127.40 10.94 116.25 10.1 G 130.24 12.50

4. SoN-Pro 86.03 3.9 1 86.40 5.09 85.25 3.33 85.32 4.27

S. Md. 1 to NB 28.10 4.86 26.23 5.94 30.33 6.63 20.96 8.61

6. Md. 1 to MP (lMPA) 97.86 4.34 94.95 7.28 101.28 5.13 85.84 11.82

7. Md. 1 to SN 52. 18 6.53 52.53 7.21 44.95 6.88 62 .40 9.51

8. S-N-Id 83.37 3.68 81.90 3.75 78.83 3.37 86. 18 4.45

9. OP to SN 12.77 3.96 15.54 4.52 17.09 4.45 13.80 5.92

DENTOALVEOLAR LINEAR MEASUREMENTS (in mm)

10. Max. 1 to NA 6.64 1.34 6.54 2.03 7.53 2.95 8.02 2.83

11. Max. 1 to N pog 10.20 2.64 10.10 3.18 14.39 3.4 1 3.80 4.49

12. Md. 1 to NB 6.80 1.92 6.93 2. 19 8.0 1 2.86 5.20 2.49

13. Md. 1 to N pog 5.02 2.47 5.YO 2.69 6.46 3.80 4.00 2.86

14. Maxil lary alveolar depth (MxAD) 15.50 4.00 14.18 3.33 13.6 3.50 13.42 3.94

15. Mandibular alveo lar depth (MdAD) 9.29 1.71 8.91 2.04 9.05 1.91 7.76 2.36

16. Max illary anterior alveolar and basa l height (MxAABH) 21.24 2.05 21.13 3.13 21.34 3. t 1 19.56 4.64

17. Mandibular anterior alveolar and basa l height (MdAABH) 32.49 2.90 33.06 3.50 33.24 2.85 32.32 3.76

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