FINAL DR MANISH

ACKNOWLEDGEMENT

To begin with, I thank the most merciful and compassionate, the ALL MIGHTY GOD.

An enterprise such as this can only be accomplished with proper guidance, assistance

and encouragement which I received by my guide Dr.P.P.BISWAS, Associate Professor,

Department of Orthodontics and Dentofacial Orthopaedics, Bapuji Dental College and

Hospital, Davangere. His valuable suggestions not only during this dissertation but entire my

post-graduation brought me to this stage.

It is with utmost sincerity and deep sense of appreciation that I thank my beloved

teacher Dr.K.SADASHIVA SHETTY, Principal, Professor and Head, Department of

Orthodontics and Dentofacial Orthopaedics, Bapuji Dental College and Hospital, Davangere.

A mere word of thanks is not sufficient to express his unflinching support, keen

surveillance, inestimable aid, and continued inspiration during the preparation of this

dissertation. He has enlightened me about the absorbing and stimulating world of

orthodontics with his truly encyclopedic knowledge and experience. During these three

years of post graduation his demands for perfection set a strong foundation on learning the

basics, logical thinking and working systematically in every aspects of my life. As his

postgraduate student, I have not only gained knowledge but also other humane qualities of

life.

His discipline, principles and scientific approach to his art of orthodontics shall always

be my guiding start to follow his trodden path in the quest for perfection. I am indeed

fortunate to be among the few who have had the honour of being his disciple, for which I will

be ever grateful. Last, but not the least, I require his blessings forever, before I venture out

into this competitive world.

I am indebted to Dr.RAMANJULU T., Dr.DIVAKAR K., Associate Professors for their

efficacious guidance and altruistic co-operation and support throughout my post-graduation

course.

I am very grateful to Dr.ALIREZA JAFARI NAIMI, Dr.JEBBY JACOB,

Dr.KRISHNAKANTH REDDY, Dr.ASHUTOSH SHETTY, Dr.PRASHANTH C.S., Dr.SUNIL

SUNNY, Assistant Professors who were very helpful, cheerful and encouraging in the

preparation of this dissertation.

I am thankful to Mr.SANGAM B.K., Bio-Statistician, J.J.M. Medical College,

Davangere for his service in carrying out the statistical analysis.

I also thank Mr.Surendra of M/s.DYNA COMPUTERS and Mr.Vamshi of M/s.

PACE COMPUTERS for organization and neat typing of this manuscript.

My special thanks to my friend Dr.AMIT SHAIKH, who has helped me in and out in

the preparation of this dissertation. I am thankful to Dr.ASHISH GUPTA, for helping me to

present this dissertation in a neat form.

A lot of thanks and appreciation to all my colleagues and non-teaching staff for being

with me and helping me directly or indirectly throughout the course.

Finally words are not suffice to express my gratitude to my PARENTS, My brother

Mr.AMARISH GOYAL and my wife Dr. NEELAM GOYAL It is their love, prayers and

sacrifices that made my education possible. Thank you all for being there.

Dr.MANISH GOYAL

1

CONTENTS

PAGE NO.

1. INTRODUCTION 01

2. AIMS AND OBJECTIVES 03

3. REVIEW OF LITERATURE 04

4. MATERIALS AND METHODS 16

5. RESULTS 28

6. DISCUSSION 52

7. SUMMARY AND CONCLUSION 55

8. BIBLIOGRAPHY 56

2

LIST OF ILLUSTRATIONS

PHOTOGRAPHS :

Armamentarium used in this study.

FIGURES :

1. Hard-Tissue Analysis (Angular parameters)

2. Hard-Tissue Analysis (Linear Parameters)

3. Soft-Tissue Analysis (Angular Parameters)

4. Soft-Tissue Analysis (Linear Parameters)

5. Dental Analysis (Angular and Linear parameters)

TABLES :

TABLE 1 Skeletal Measurements (Angular)

TABLE 2 Skeletal Measurements (Linear)

TABLE 3 Soft Tissue Measurements (Angular)

TABLE 4 Soft Tissue Measurements (Linear)

TABLE 5 Dental Measurements

TABLE 6 Linear Sagittal Changes of Soft Tissue Landmarks after movements of skeletal

landmarks (Expressed in percentage)

SUPERIMPOSITIONS OF INDIVIDUAL SUBJECTS :

Basion-Nasion Line registered at CC point.

Superimposition : I

Superimposition : II

Superimposition : III

Superimposition : IV

Superimposition : V

Superimposition : VI

Superimposition : VII

Superimposition : VIII

BARGRAPHS :

Graph I : Angles : SNB, ANB, N-A/Pg-A

Graph II : Angles : MP-HP, N-Pg/FH

Graph III : Linear : N-B (11 HP), N-Pg (11 HP), N-Pg (11FH)

Graph IV : Linear : ANS – Mn, Go to Pg

Graph V : Angles : G-Sn-Pg’, Sn-Gn-C, Cm-Sn-Ls

Graph VI : Angles : Ns-Pg’/FH, Ns-Pg’/Pg’-Ls, Li-Ils/FH, Sn-Ls/FH

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Graph VII : Linear : G-Pg’, G-Sn and Sn-Mn (HP), Sn-Gn and Gn-C

Graph VIII : Linear : Li to (Sn-Pg’), Ils to (Li-Pg’), E-line

Graph IX : Linear : Pg-Pg’, Ls-U1/Sls-A, Sls-Ls

Graph X : Isi-Isa/Iii-Iia, Iii/Isi (Hor), Iii/Isi (vert)

Graph XI : Iii-Iia/MP, Iii/A-Pg

1

INTRODUCTION

The facial deformity caused by mandibular prognathism has long been of great mutual

interest to the orthodontist and the oral surgeon. The deformity of the lower jaw is readily

expressed as a profile disfigurement, since the soft tissues of the face depend on the lower

jaw for much of their contour. The dental literature is replete with various surgical techniques

for the correction of mandibular prognathism.

The selection of the proper type and site of osteotomies in orthognathic surgery is

based on the extent of the dentofacial deformity, the degree of the desirable jaw movement,

and the anticipated soft-tissue changes following surgical intervention. Improvement of the

stomatognathic function is a major reason for seeking combined orthodontic surgical therapy,

but the consequences of surgery on facial appearance are of great importance, even for the

patient whose chief complaint is not dominated by the cosmetic rationale.

Therefore an accurate prediction of the postoperative facial profile comprises an

essential and integral part of the diagnostic and treatment planning procedures of the

combined surgical orthodontic therapy.

Surgical correction of Class III dentofacial deformities may be accomplished by

maxillary advancement, mandibular setback, or bimaxillary procedures. In some instances,

the choice between these procedures is not straight forward. While any of these approaches

are usually equally effective in correcting the dental malocclusion, each procedure affects the

patient’s appearance differently, with only 1 resulting in the most esthetically pleasing profile.

During the last 20 years, several cephalometric investigations have reported on the

alterations of the soft tissue profile that accompany mandibular setback, thus enlightening

our understanding of the interplay between dentoosseous and soft tissues and providing data

for predicting postsurgical soft tissue response.

However, soft tissue response after mandibular set back osteotomies is in many

instances subject to individual variation, and the predictability of soft tissue changes is not a

precise science.

Alterations of the soft tissue profile that accompany mandibular setback surgery have

been addressed by several studies. While there is general agreement on the anticipated

average impact of surgery, little is known about the influence of factors such as gender,

presurgical facial morphology, soft tissue tonicity, magnitude of surgical repositioning and

skeletal relapse on soft tissue response. Knowledge of possible effects of these variables

could improve the accuracy of presurgical predictions.

2

The aims of the present cephalometric study were (1) to describe the

interrelationships of the soft tissue and dentoskeletal profiles following total mandibular set

back osteotomies and (2) to detect whether there were cephalometric variables that could

contribute to an accurate prediction of the surgical effect on the soft tissue profile.

3

AIMS AND OBJECTIVES

The aims of the present retrospective cephalometry study were :

1) To describe the interrelationships of the soft tissue and dentoskeletal profiles after total

mandibular setback osteotomies.

2) To detect whether there were any cephalometric variables that could contribute to an

accurate prediction of the surgical effect on the soft tissue profile.

4

REVIEW OF LITERATURE

The surgical correction of mandibular prognathism falls into two categories;

mandibular osteotomy which involves sectioning of the ramus of the mandible at various

locations, and mandibular ostectomy which involves the removal of a section of bone from

the mandible.

Hullihen (1849)1 reported a surgical procedure used in the correction of a mandibular

deformity. He described an ostectomy procedure which effectively lengthened the body of

the mandible.

Blair (1898)1 pioneered the surgical correction of mandibular prognathism in this

country, presented a report on a resection of the mandible in the bicuspid area, a procedure

which severed the nerve and blood supply of the mandible.

Babcock (1910)1 reported on a horizontal osteotomy of the mandible above the

mandibular sulcus, an operation which preserved the mandibular vessels.

Harsha (1912)1 reported on a mandibular body ostectomy posterior to the last molar

tooth which also preserved the mandibular artery and nerve.

Limberg (1925)1 was one of the first to describe orthodontic treatment performed

before the necessary surgical procedure.

Dingman (1944)1 refined the ostectomy procedure by introducing a two stage bilateral

ostectomy of the mandible. Intraoral cuts were made to the level of the mandibular canal

and after a suitable healing interval, the external sectioning of the mandible and subsequent

repositioning of the mandibular fragments were accomplished.

Moose (1945)1 wrote on a strictly intraoral approach to a horizontal osteotomy of the

ramus of the mandible with a special power driven Cayo saw.

Goldstein (1947)1 was the first to objectively evaluate mandibular prognathism cases

which were surgically corrected. He studied seven cases treated by combined surgical and

orthodontic methods. Orientated cephalometric headplates, photos, and study models

comprised his records for evaluation. He discussed bony union, function, and position of the

mandibular fragments after surgery.

Steiner C.C., Hills B.Calif (1953)29 proposed a composite analysis which he believed

would provide the maximum clinical information with the least number of measurements.

Certain measurements were selected and the averages were determined in a series of

individuals with normal occlusions. By comparing the traced readings of patients with

malocclusions, to those of normal occlusions the degree of deviation from the normal was

determined. The analysis comprises of various parts of the skull namely, the skeletal, dental

and soft tissues. The skeletal analysis relates the upper and lower jaws to the skull and to

5

each other. The dental analysis entails the upper and lower incisor teeth to their

respective jaws and to each other. Finally, the soft tissue analysis provides a means of

assessing the balance and harmony of the lower face profile.

Biederman (1954)1 was the first to apply commonly used cephalometric

measurement standards to surgically treated cases. He investigated five surgically treated

cases of mandibular prognathism using orientated cephalometric headplates and came to

the conclusion that facial esthetic nd occlusion of these cases were markedly improved.

Lubowitz (1957)1 presented a case report of the surgical correction of mandibular

prognathism using cephalometric measurements as a basis for his report along with photos

of the patient and of study models.

Burstone C.J. (1958)5 presented a method of direct integumental analysis,

employing angular readings that describe profile components to the skull as a whole

(inclination angles) and to each other (contour angles). These readings are made from

oriented lateral headplates exposed to show both hard and soft tissue detail. The average

morphology and variation of acceptable profiles are described, based on the Herron sample.

The hypothesis is explored that average inclination, contour, and proportion is related to

profile excellence. Graphic comparison to the Herron sample by use of the integumental

profile grid expedites the analysis of malocclusion deformity and the study on soft tissue

changes occurring during growth and treatment.

Aaronson S.A., Monica S. (1967)1 investigated the cephalometric measurements,

the net hard and soft tissue changes occurring after the surgical correction of mandibular

prognathism by the subcondylar osteotomy procedure and to demonstrate the need for future

investigation of all facets of surgical correction of mandibular prognathism on a

cephalometrically orientated basis. They concluded that the facial concavity in regard to the

relationship of the hard and soft tissue chin to the upper face, was decreased by this surgical

procedure; facial esthetics was improved. The mandible was repositioned posteriorly in all

cases. The changes in angulation of the skeletal analysis measurements showed varying

degrees of correlation to the posterior displacement of the chin (pogonion). The soft tissue

contour of the upper lip, the maxillary sulcus of the upper lip, the lower lip, the mandibular

sulcus of the lower lip, and the soft tissue chin were altered by the surgical procedure. The

greatest variation in response and least amount of change of the soft tissue profile was

exhibited by the upper lip and maxillary sulcus of the upper lip. The least amount of variation

and the greatest amount of change of the soft tissue profile was exhibited by the lower lip,

the mandibular sulcus of the lower lip, and the soft tissue chin. The lower lip and the soft

6

tissue chin, being posteriorly repositioned in all cases, assumed a better esthetic

relationship to the rest of the soft tissue profile.

White R.P. et al (1971)32 studied the changes in facial heights of 46 patients who had

undergone mandibular osteotomies. It was found that there was an increase in the anterior

facial height with a decrease in the posterior facial height. Inspite of the increase and

decrease of the anterior and posterior facial heights there was little effect on the patients

profile. They concluded that predicting the postoperative profile in addition to the occlusal

changes is the best method of avoiding an undesirable result.

McNeill R.W. et al (1972)25 proposed a new method of surgical orthodontic treatment

planning which circumvents this limitation by combining the usual cast sectioning and

repositioning procedures along with cephalometric prediction of the post-surgical skeletal and

soft tissue relationships. A prediction technique was suggested for correction of mandibular

retrognathism and prognathism. They concluded that dental casts and objective

cephalometic analysis should be augmented with cephalometric prediction of the projected

post-surgical relationship of dentoskeletal and facial soft tissue structures.

Robinson S.W. et al (1972)27 studied the changes of soft tissue landmarks relative to

hard tissue landmarks in cases of mandibular prognathism treated by a combined

orthodontic surgical approach and showed significant correlation’s between changes in soft

and hard tissue landmarks in the horizontal plane but not in the vertical direction.

Hershey H.G. and Smith L.H. (1974)14 studied pretreatment and post treatment

cephalometric roentgenograms of twenty four patients who had undergone surgical

orthodontic correction of mandibular prognathism to describe the response of the soft tissue

profile and concluded that significant change in the morphology of the upper lip was

observed as a decrease in prominence of the upper lip in relation to its sulcus and observed

clinically as a flattening of the upper lip. Change in the morphology of the lower lip was also

significant. The prominence of the lower lip increased in relation to its sulcus, producing a

more everted appearance with treatment. The increase in lower lip prominence was

approximately twice the amount of upper lip flattening. The pretreatment thickness of the

soft tissues of the lips was not a significant factor in determining their response to surgery.

The hard tissue movement versus soft tissue response relationship was similar for large and

small amounts of surgical movement.

Lines P.A. and Steinhauser E.W. (1974)24 did a preliminary study of soft tissue

changes following surgical orhtognathic procedures, he analysed 41 cases before treatment

and at least three months after surgery. He measured between constructed hard tissue and

7

soft tissue points located on each before and after film tracing. Comparisons were

made, and ratios of soft and hard tissue changes were formulated. He concluded that in all

the cases of total mandibular setback the soft tissue chin follows the bony chin in a ratio very

close to 1:1. The lower lip at the vermilion border, however, only followed the mandibular

incisal edge at a relationship of 75% or a ratio of 3:4. It was interesting that in all cases, the

upper lip at the vermilion border followed the mandible backward for approximately 20% of

the mandibular movement, even though no maxillary hard structures were moved.

Worms F.W., Isaacson R.J. and Speidel M.T. (1976)35 has described the importance

of adequate and proper diagnosis in mandibular surgical cases and also discussed the

various methods of pre-surgical removal of dental compensation orthodontically with the help

of various profile analysis and concluded that evaluation of soft tissue contour and vertical

proportionality must be recognized as an essential element in surgical orthodontic diagnosis

and treatment planning.

Burstone C.J. et al (1978)6 designed a dento-skeletal cephalometric analysis based

on the standards obtained from a longitudinal study at child research council of the University

of Colorado School of Medicine. The analysis describes the horizontal and vertical position of

facial bones by use of a constant coordinate system, thereby representing the size of the

bones by linear dimensions and their shapes by angular measurements. They concluded

that measurement being primarily linear and angular they can be readily applied to prediction

overlays and study cast mountings to serve as a basis for evaluation of post-treatment

stability.

Hillesund E., Fjeld D. and Zachrisson B.U. (1978)15 investigated the reproducibility

of the soft tissue profile in lateral cephalograms with particular reference to relaxed and

closed lip positions in patients with large overjets. Also variations in upper and lower lip

thickness in patients with different lip positions and degrees of overjet were measured. The

material comprised thirty five children with marked overjet (more than 8 mm) and a group of

thirty two children with "normal” horizontal and vertical incisor relationships. All patients were

recorded twice at 3 week intervals. Both times two cephalograms were taken, one with the

lip in light contact and another with the teeth in occlusion but with lips relaxed. They

concluded that both from the standpoint of reliability and from a desire to accurately evaluate

profile changes associated with orthodontic treatment, cephalograms of persons with large

ovejets should be taken with the lips relaxed. Also, head films of patients with normal incisor

relationship may be taken with the lips in relaxed position because the reproducibility of the

soft tissue profile is fully acceptable. Thus, cephalogram taken with the lips relaxed and the

8

teeth in occlusion seem to provide the most correct reproduction of lip position and

morphology.

Suckiel J.M. and Kohn M.W. (1978)30 analyzed statistically a series of fifty patients

treated surgically for mandibular prognathism to study relative soft and hard tissue changes.

Changes in the soft tissue of the chin and in the lower lip position relative to the underlying

mandibular structures are well related in a nearly 1:1 ratio. Upper lip modifications have

been shown to be less well related to mandibular repositioning. The ratio of change of

mandibular landmarks to soft tissue points and their over all positional change can be helpful

in presurgical treatment planning of patients with mandibular prognathism.

Kajikawa Y. (1979)20 undertaken a study to investigate changes of the facial soft

tissue profile which have resulted from surgical correction of Class III malocclusion by

movement of the underlying skeletal and dental structures and to evaluate the results by

comparing them with normal soft tissue profiles. The patients consisted of 11 males and 22

females in whom skeletal Class III malocclusion was corrected surgically when they were

between 14 and 26 years of age. Lateral cephalograms that were taken in centric occlusion

before and after surgery were used to evaluate changes in hard and soft tissue during

treatment. The soft tissue profile of the patients was closely related to the underlying skeletal

and dental structures and was characterized by prominence in the region from the lower lip

to the chin associated with the turned up contour of the upper lip.

Legan H.L., Dollar, Burstone C.J. (1980)22 developed a simplified and relevant soft

tissue analysis that is applicable to planning treatment for patients requiring orthognathic

surgery. Standards presented described young adult Caucasians and concluded that facial

improvement is one of the major objectives of surgical procedures which should be

measured directly and his soft tissue analysis evaluates both horizontal and vertical aspects

of face including lip length and posture. If a prime objective of orthognathic surgery is facial

improvement, soft tissue analysis is important in treatment planning.

Wisth P.J. (1981)34 examined forty four patients, 10 years after their mandibular

protrusions had been surgically corrected, related the findings to those of previous

examinations 6 weeks and 2 years postoperatively. The intention was to describe changes in

facial morphology, dental arches, and marginal bone height in the anterior region and to

record the patients feelings in relation to functional esthetics and social fitness. In the

majority of the patients the mandible was in a relatively stable position. A small increase of

the mandibular prognathism was however common. The length of the mandibular dental

arch was reduced, and so was the mandibular intercanine width. The mandibular intermolar

width was increased. The mandibular anterior teeth displayed a continuous tendency toward

9

crowding. The majority of the patients were satisfied with the treatment in relation to

appearance, function and social fitness.

Heldt L, Haffke E.A. and Davis L.F. (1982)13 in their two fold study reviewed the

pertinent literature related to psychosocial factors which influence cosmetic surgical success,

and second to report the results of a preliminary study conducted to determine the influence

of psychosocial factors on the success of orthognathic procedures and found that structured

interview appears to be a very effective means of gaining insight into the psychosocial

factors that influence a person considering orthognathic treatment. Pretreatment interviews

would help in identifying favorable candidates and would serve as a guide to patient

management. The entire profession needs to be more acutely aware of the psychological

importance of the proper timing of treatment. Concern with appearance and a desire for

correction are very great during adolescence. This is also the age during which optimal

psychological benefits can be realized. Therefore, special efforts to identify these patients

early in adolescence and to institute treatment as soon as possible are critical.

Bachmann J. and Wisth P.J. (1983)4 evaluated the methods for prediction of the soft

tissue profile subsequent to oblique subcondylar ostoetomy for correction of mandibular

protrusion. The first one included distalization of the mandible into an Angle Class I

relationship. The amount of distalization and any vertical changes were transferred to the

tracing, and the anticipated new profile was drawn. The second method was based on the

profile means of a group of “normal” persons and was aimed at correction of both sagittal

and vertical discrepancies. The study included fifty patients. A double set of prediction

tracings was made according to both methods and compared the results with the actual

postoperative results and with a “normal” control group. Both methods were usable, as the

predictions were considered satisfactory if they were within one standard deviation from the

mean of the control group. The sagittal changes were somewhat exaggerated by both

analyses. The vertical changes were much better expressed by the profile prediction. Such

changes are difficult to create by the vertical subcondylar osteotomy. Consequently, the

model prediction seems most suitable for planning profile changes in surgical techniques that

include mobilization of one main mandibular fragment.

Holdaway R.A. (1983)16 presents a soft tissue analysis which demonstrates the

inadequacy of using a hard tissue analysis alone for treatment planning. He states that for

adolescents the normal or usual thickness of the soft tissue at point A is 14 to 16 mm. As

point A is altered by tooth movement, headgear, etc., the soft tissue will follow this point and

remain the same thickness. When there is taper in the maxillary lip immediately anterior to

the incisor, as in protrusive dentures, the tissue will thicken as the incisors are moved

10

lingually until the tissue approaches the thickness at Point A. When the lip taper has

been eliminated, further lingual movement of the incisor will now cause the lip to follow the

incisors in a one to one ratio. These concepts are predictable in adolescents when the lip

thickness at point A is within the normal range. Some exception are as follows ; Even if there

is lip taper, if the tissue thickness at point A is very thin the lip may follow the incisor

immediately and still retain the taper. If the tissue at point A is very thick, the lip may not

follow incisor movement at all. Adult tissue reaction is similar to the first exception.

Eventhough there may be lip taper, the lips will usually follow the teeth immediately. He also

illustrated a normal or acceptable range of variation for facial harmony related to variations in

skeletal convexity.

Holdaway R.A. (1984)17 described the Visual Treatment Objective (VTO) into 10

steps by evaluating treatment effects on such things as mandibular growth behaviour and

anchorage conservation in order to increase accuracy and concluded that VTO is completely

practical as a treatment planning procedure to approach the proposed orthodontic changes

from a soft tissue analysis perspective, making changes only to the point where the best

possible soft tissue profile is established, and then compute the tooth movement necessary

to develop ideal profile relationships.

Athanasiou A.E., et al (1989)3 examined 48 adults with various dentofacial

deformities to determine the craniomandibular functional status of patients who seek

orthognathic surgery and the functional parameters of the patients were compared with

those of a normal population. The relationship between function and morphology also

studied. He include a clinical examination of dysfunction an evaluation of the number and

intensity of occlusal contacts, a kinesiographic analysis of mandibular movements at the

incisors, an evaluation of ramal and condylar vertical symmetry by means of dental rotational

panoramic radiography and an examination of profile and frontal cephalograms. Results

showed that the patients seeking orthognathic surgery showed craniomandibular functional

patterns different from those of the normal group or healthy population. However, because

no significant correlations were found among specific morphologic and functional

characteristics and dysfunctional status (with the exception of condylar asymmetry, the

maximal deviation of a maximal opening closing movement defined on the sagittal plane, and

the inclination of the maxillary central incisor in relation to the anterior cranial base),no clear

cause effect relationship was proved.

Fanibunda K.B. (1989)10 did a retrospective study of 33 patients. He investigated the

changes occurring in the facial profile following surgical correction of mandibular

prognathism. The parameters measured included surface area, shift of selected points,

11

facial outline length and directional measurement in addition to the sella-nasion plane.

The calculation of linear regression equations enabled prediction of the shift of selected soft

tissue points and facial outline length. It was considered, that the analysis provides an

accurate picture of the behaviour of the soft tissues in response to a given amount of bony

movement showing correction of the deformity.

Lew K.K.K. et al (1990)23 investigated with serial lateral cephalometric radiographs,

the changes in the facial contour associated with total mandibular setback surgery for the

correction of mandibular prognathism in a sample of Chinese patients and concluded that

posterior movement of pogonion, point B and the mandibular incisal edges was accompanied

by posterior movement of 95% at soft tissue pogonion (r=0.96), 89% at soft tissue point B

(r=0.83), and 67% at labrale inferius (r=0.81) respectively. The correlation between changes

in the labrale superius and mandibular setback appeared to be dependent on both the

amount of mandibular setback and the degree of mandibular rotation during the setback

surgery. They concluded that results with B.S.S.O. for treating mandibular prognathism is

satisfactory and less of complications.

Gjorup H. and Athanasios A.E. (1991)12 did a study to describe the inter

relationships of the soft tissue and dentoskeletal profiles after total mandibular setback

osteotomies and to detect whether there were any cephalometric variables that could

contribute to an accurate prediction of the surgical effect on the soft tissue profile. The

presurgical and postsurgical lateral cephalograms of 50 consecutively treated patients (37

females and 13 males) were used. The assessment of the results disclosed that

considerable facial changes and improvement took place after the surgical procedure. The

skeletal and soft tissue facial profiles were straightened and the posture of the lips was

improved.

Vasir N.S. et al (1991)31 did a study on 15 patients presenting with a Class III

malocclusion treated by a sagittal split osteotomy for assessing skeletal and dental changes.

All patients received orthodontic treatment with Straight wire appliances both prior to and

following surgery These appliances were also used for fixation. The lower incisors were

proclined by 8.4 degrees before surgery with little change in upper incisor inclination. With

surgery, there was a mean reduction of 4.3 degrees in the angle SNB. Following surgery,

the relapse in mandibular position was minimal and was not related to the dental changes

during this period. Changes in the vertical skeletal parameters were generally small. The

study shows a range of variations which indicates that the relapse is a multifactorial problem.

Athanasiou A.E. (1993)2 reviewed the various morphologic and functional

implications of the surgical orthodontic management of mandibular prognathism, thus

12

providing amore complete determination of the efficacy of this modality of treatment

and concluded that (1) After treatment considerable improvement takes place on the soft

tissue and dentoskeletal profile, occlusal tooth contacts, and temporo mandibular joint

function and pain; (2) Surgical management of mandibular prognathism can be associated

with decreased maximum interincisal opening; (3) Although immediately after surgery there

is a tendency for the condyles to be distracted downward and anteriorly from their

preoperative position, in long term postsurgery the condyles, on the average, regain their

initial position; (4) Compensatory alterations in the pharyngeal, suprahyoid, and infrahyoid

muscular regions take place postoperatively; (5) Skeletal changes after mandibular setback

to correct mandibular prognathism occur frequently, but their magnitude and patterns exhibit

variation and are not necessarily detrimental.

Ingervall B., Thuer U. and Vuillemin T. (1995)19 studied the stability and the effect

on the soft tissue profile of mandibular setback with sagittal split osteotomy and rigid internal

fixation prospectively in 29 consecutive patients, 17 to 55 years old, who had mesial

occlusion. Profile cephalometric radiographs were taken immediately before and shortly

after surgery as well as 14 months postsurgically. The mean setback of the mandible 1 to 8

days after surgery was 6.0 mm. On average, there was also a small decrease in the anterior

facial height. The setback relapsed an average of 1.1 to 1.3 mm, so that at the follow up the

mean net effect was 80%. In eight patients, the net effect on the labial fold and the soft

tissue chin were closely correlated with those on their underlying hard structures. On

average, the labial fold and the chin followed the hard structures to 106% and 107%

respectively. The mean net effect for the lower lip was only 88% of the setback of the

mandibular incisor. The soft tissue facial height followed the decrease in the skeletal facial

height to 60%. The setback procedure also affected the upper lip, which an average,

retruded and lengthened 1.0 to 2.0 mm.

Schatz J.P., Tsimor P. (1995)28 evaluated the stability of combined surgical

orthodontic correction of Class III malocclusions. He observed changes at surgery and at 1

year postsurgery in a sample of 13 patients undergoing mandibular setback by bilateral

sagittal split osteotomy. The average posterior movement of the chin at surgery was 7.27

mm of point B, 6.39 mm at pogonion, and 5.72 mm at menton. Changes from postsurgery to

1 year follow up revealed statistically significant differences in horizontal measurements in

which a forward movement of the mandible at point B, pogonion, and menton indicated a

relapse tendency. Although vertical changes were minimal, soft tissue points followed

relapse of the chin to the same extent.

13

Capelozza F.L. (1996)7 presented the influence of the presurgical orthodontic

preparation on the surgical correction of mandibular prognathism. The study involved the

cephalometric examination of two groups of patients, who were considered either adequately

or inadequately treated during the presurgical orthodontic phase. The result showed that

dental compensation is common in both the maxillary and mandibular arches. Such

compensation is more frequently eliminated from the mandibular arch during presurgical

orthodontic treatment. There was some correlation between decompensation and the

amount of mandibular reduction during surgery and a strong correlation between

cephalometric postsurgical mandibular excess and the lower anterior facial height.

Kolokitha C.E. et al (1996)21 evaluated the validity of the predictions of a

computerized cephalometric system regarding dentoskeletal and soft tissue profile changes

after mandibular setback and maxillary impaction osteotomies. Tracings of lateral

cephalograms taken at the end of preoperative orthodontics and approximately 1 year after

the operation were digitized and entered into the Dentofacial Planner. For the mandibular

setback group, the computerized predictions tended to place the mandible less posteriorly

than the actual situation and to significantly underestimate the mandibular plane angle, the

total anterior skeletal and soft tissue facial heights, the lower anterior skeletal facial height,

and the upper lip height.

Chunmaneechote P., Friede H. (1999)8 did a study to investigate the facial soft

tissue profile changes after mandibular setback surgery and to apply the data generated in

an effort to improve the accuracy of the predicted profile line in our present cephalometric

software program Quick Ceph Image Pro. Forty one Caucasian subjects, who had

undergone mandibular setback surgery by use of vertical ramus osteotomy, were divided into

two groups with 23 and 18 patients in each sub sample. The minimum age at surgery of the

whole sample was 17.2 years and the postsurgical cephalogram was taken at least 5.5

months after surgery. The upper lip thickness decreased and the lower lip thickness

increased after surgery. The findings of this study on the accuracy and precision of the

software a the digitizer revealed rather low accuracy but acceptable precision.

Enacar A., Taner T. and Toroglu S. (1999)9 evaluated the soft tissue profile changes

resulting from double jaw surgery (maxillary advancement and mandibular setback) and

mandibular setback alone. He evaluated the measurements on the preoperative and

postoperative cephalometric radiographs of 24 skeletal Class III patients. The results

demonstrated significant correlations and suggested that the soft tissue ratios seen in double

jaw surgery were similar to those in mandibular setback surgery alone, with the exception of

14

the changes in nasal tip projection and the upper lip area. In both groups, (1) The

skeletal and soft tissue facial profiles were straightened, and the posture of the lips was

improved. (2) A backward rotation of the mandible was measured, (3) The change in the

nasolabial and mentolabial angle was not predictable. However, nasolabial angle increased

and labiomental angle decreased significantly in both groups, improving the dentofacial

esthetics, (4) The lower lip moved posteriorly in response to the posterior movement of

pogonion. The horizontal change of lower lip was predictable, whereas the horizontal soft

tissue pogonion movement was not predictable in double jaw surgery group only. (5) An

increase in the horizontal soft tissue movement from the tip of the nose to the free end of the

upper lip was observed, (6) The nasal tip projection followed the movement of the underlying

skeletal structure significantly and predictably. (7) E-Upper lip distance decreased, and this

change was predictable, with a ratio of 1.8:1.

Gaggl A., Schultes G. and Karcher H. (1999)11 analysed the changes in soft tissue

profile after sagittal split ramus osteotomy and mandibular setback. He recorded the soft

tissue changes relative to had tissue references by means of computer supported

measurements of preoperative and postoperative standardized lateral skull radiographs of 60

Class III patients. An average backward transposition of the osseous pogonion of 7.1 mm

was recorded. Relative to movement of this reference point in the sagittal plane, the soft

tissue pogonion moved 83.9% the soft tissue menton moved 98.9%the labrale superior

moved 32.0% the stomion moved 45.2% and the labrale inferior moved 79.6%. The same

measurements were performed in the vertical plane, and changes in soft tissue references

were analyzed. There was a marked difference in soft tissue changes after mandibular

retropositioning when compared with results after mandibular advancement reported in the

literature and concluded that it is of great importance to consider both the direction and the

surgical method when predicting profile changes in the vertical as well as sagittal plane after

orthognathic surgery.

Hu J., Wang D., Luo S. and Chen Y. (1999)18 did a study to investigate the soft

tissue profile changes after surgical correction of mandibular prognathism in Chinese

patients and evaluated the sex differences in the ratios of soft tissue to hard tissue change.

Forty three adult Chinese patients (18 men and 25 women) with mandibular prognathism

were treated by intraoral oblique or vertical ramus osteotomy. Lateral cephalometric

radiographs were taken presurgically and between 6 to 12 months postsurgically, and

specific soft and hard tissue point were digitized and analyzed with a computer aided system.

As a result of surgical setback of the mandible, the soft tissue to hard tissue change ratios

were Li:Ii = 0.71:1, Is:B=0.90:1, Pg’:Pg = 0.94:1 for the males; and Li-Ii=0.82:1, Is:B = 0.92:1,

15

Pg’:Pg = 1.06:1 for the females and they concluded that the changes in soft tissue

were closely correlated with the hard tissue movement after surgical setback of mandible.

The average ratios of soft tissue to hard tissue change in horizontal direction appear to show

a gender difference, which suggests the need for different ratios when predicting the results

of orthognathic surgery.

Mobarak K.A. et al (2001)26 assessed long term changes in the soft tissue profile

following mandibular setback surgery and investigated the presence of factors that may

influence the soft tissue response to skeletal repositioning. The subjects enrolled were 80

consecutive mandibular prognathism patients operated with bilateral sagittal split osteotomy

and rigid fixation. Lateral cephalograms were taken at 6 occasions; immediate presurgical,

immediate postsurgical, 2 and 6 months postsurgical, and 1 and 3 year post surgical.

Females generally demonstrated greater ratios than males with a statistically significant

difference for the upper lip and chin (P<.05). Postsurgical alterations in the profiles were

more predictable in patients with larger setbacks compared to patients with smaller ones.

16

MATERIALS AND METHODS

1. DATA COLLECTION :

Pre-treatment, Pre-surgical and post-surgical lateral cephalograms of 8 adult patients

who had been treated successfully at Department of Orthodontics and Dentofacial

Orthopedics, Bapuji Dental College and Hospital, Davangere were obtained. The age group

of these patients ranged from 17 to 25 years, with a mean age of 21 years. Post-surgical

cephalograms were taken two months following surgery. All the patients used in the study

were treated by Pre-adjusted Edgewise appliance for pre-surgical decompensation with or

without extractions. Bilateral sagittal split osteotomy for mandibular set back procedure was

carried out under the supervision of a single surgeon.

2. MATERIALS USED IN THE STUDY :

1. Standardized pre-treatment, pre-surgical and post-surgical cephalograms.

2. 0.3 mm acetate tracing paper

3. 0.3 mm lead pencil.

4. Geometry Box (Scale, Protractor, Setsqures, Eraser, Sharpener).

5. Scotch tapes

6. Tracing board

7. Black, green and red pilot pens

8. Scissors and calculator

3. CRITERIA FOR SELECTION OF PATIENTS :

The primary selection criterion were :

1. Patient was a non-growing adult.

2. Patient had a natural dentition supporting the lips.

3. Patient demonstrated a severe class III skeletal malocclusion with an ANB of -1 to -5 and

prognathic mandible for which surgical intervention was necessary.

4. Mandibular setback procedure was carried out by bilateral sagittal split technique and in

two of the cases genioplasty was also performed.

The technique employed in taking the cephalograms was as follows :

1. All radiographs of each subject were taken using the same machine.

2. Each cephalogram was taken with the patients teeth in habitual occlusion and lips at rest

position.

3.

17

4. ANALYSIS OF LATERAL CEPHALOGRAMS :

Profile cephalograms were taken in occlusion under standardized conditions with a

cephalostat. Among the various surgical cephalometric analysis for estimating the amount of

hard and soft tissue changes, the Legan Burstone, Steiner’s, McNamara, Rickett’s,

Holdaway and Rokosi Jarabak analysis were employed in this study. These analysis include

certain angular and linear measurements for both hard and soft tissues, which were easily

applicable for the study.

The various hard tissue landmarks include :

1. Sella (S) : The point representing the geometric center of the pituitary fossa (Sella

turcica).

2. Nasion (N) : the most anterior point of the frontonasal suture in the mid sagittal plane.

3. Subspinale (A) : The deepest point in the mid sagittal plane between the anterior nasal

spine and prosthion, usually around the level of and anterior to the apex of the maxillary

central incisors.

4. Pogonion (Pg) : The most anterior point in the midsagittal plane of the contour of the chin.

5. Supramentale (B) : The deepest point in the mid sagittal plane between infradentale and

pogonion, usually anterior to and slightly below the apices of the mandibular incisors.

6. Anterior nasal spine (ANS) : the most anterior point of the nasal floor, the tip of the pre-

maxilla in the mid sagittal plane.

7. Menton (Mn) : The lowest point on the contour of the mandibular symphysis.

8. Gnathion (Gn) : The midpoint between pogonion and menton located by bisecting the

facial line N-Pg and the mandibular plane.

9. Mandibular plane (MP) : A plane constructed from menton to the gonion of the mandible.

10.Gonion (Go) : Located by bisecting the posterior ramal plane and the mandibular plane

angle.

11.Horizontal plane (HP) : A plane constructed by drawing a line at 7o from sella nasion

plane. It is a surrogate of Frankfort horizontal plane.

12.Fronkfort horizontal plane (FH Plane) : A plane constructed by drawing a line from porion

to orbital.

13.Sella nasion plane (SN Plane) : A plane constructed by drawing a line from sella to

nasion.

18

The soft tissue landmarks include :

1. Glabella (G) : The most prominent point in the mid sagittal plane of the forehead.

2. Columella point (Cm) : The most anterior point on the columella of the nose.

3. Subnasale (Sn) : The point at which the nasal septum merges with the upper cutaneous

lip in the mid sagittal plane.

4. Labrale Superius (Ls) : A point indicating the mucocutaneous border of the upper lip.

5. Labrale Inferius (Li) : A point indicating the mucocutaneous border of the lower lip.

6. Mentolabial sulcus (Ils) : The point of greatest concavity in the midline between the lower

lip and chin.

7. Soft tissue pogonion (Pg’) : The most anterior point on soft tissue chin.

8. Soft tissue Gnathion (Gn) : The constructed midpoint between soft tissue pogonion and

soft tissue menton.

9. Soft tissue menton (Mn') : Lowest point on the contour of the soft tissue chin.

10.Cervical point (C) : The innermost point between the submental area and the neck

located at the intersection of lines drawn tangent to the neck and submental area.

11.Superiorlabial Sulcus (Sls) : The point of greatest concavity in the midline of the upper lip

between subnasale and labrale superius.

12.Nasion soft tissue (Ns) : The point of deepest concavity of the soft tissue contour of the

root of the nose.

13.Pronasale (Pn) : The most prominent point of the nose.

The Dental Landmarks include :

1) Incision inferior apical (Iia) : The midpoint on the bisection of the apical root width of the

most prominent mandibular incisor.

2) Incision inferior incisal (Iii) : The incisal edge of the mandibular central incisor.

3) Incision superior apical (Isa) : The midpoint on the bisection of the apical root width of the

most prominent maxillary incisor.

4) Incision superior incisal (Isi) : The incisal edge of maxillary central incisor.

ANGULAR PARAMETERS FOR HARD TISSUE EVALUATION :

1. SNB-Angle : It is the angle formed by the line drawn from sella-nasion to point-B. it

relates anterio-posterior position of mandible to the cranial base.

2. N-A-Pg-Angle (Angle of facial convexity) : It is the angle formed by the line N-A and a line

from A to pogonion. It gives an indication of overall facial convexity.

3. MP-HP Angle : Angle formed between a line from gonion to menton and HP as it

intersects gnathion. It indicates the divergence of the mandible.

19

4. ANB Angle : It is the angle formed by the line NA and N-B. It relates the anterior-

posterior position of mandible to the maxilla.

5. N-Pg/FH : It is the angle formed by the line N-Pg to FH plane. It relates the mandible to

anterior cranial base.

LINEAR PARAMETERS FOR HARD TISSUE EVALUATION :

1. Horizontal Skeletal Profile :

1. N-B (11HP) : A perpendicular line from HP is dropped through nasion. The N-B line is

measured in a plane parallel to HP from the perpendicular line dropped from N. This

measurement describes the horizontal position of apical base of the mandible in relation

to N. Therefore, a quantitative assessment of the anteroposterior position of the

mandible and the degree of mandibular horizontal dysplasia can be evaluated.

2. N-Pg (11HP) : Similar measurements are made like those of N-A and N-B points. It

indicates the prominence of the chin.

2. Vertical Skeletal Relations :

A line drawn from ANS to Mn is evaluated. It indicates the lower third facial height,

which may be helpful in evaluating the facial height pre-surgically and post-surgically.

3. Mandibular Measurement :

A line from gonion to pogonion establishes the length of the mandibular body.

4. N-Pg/FH : It is the linear distance measured from nasion perpendicular to pogonion. It

evaluates the relationship of the mandible to cranial base.

ANGULAR PARAMETERS FOR SOFT TISSUE EVALUATION :

1. G-Sn-Pg (Angle of Facial Convexity) : Angle formed by the line joined from subnasale to

soft tissue pogonion, indicates a Class II (or) Class III skeletal patterns.

2. Sn-Gn-C (Lower face throat angle) : Formed by intersection of lines Sn-Gn and Gn-C. A

critical angle which evaluates the treatment planning to correct the antero-posterior facial

dysplasias.

3. Cm-Sn-Ls (Naso Labial Angle) : Angle formed by intersection of columella of nose,

subnasale and labrale superius. Evaluates the change in the upper lip and to assess

antero-posterior maxillary dysplasias.

4. Ns-Pg’/FH : It is the angle formed by the line Ns-Pg’ to FH plane. It relates the mandible

to anterior cranial base.

5. Ns-Pg’ /Pg’-Ls : It is the angle formed by the lines Ns-Pg’ and Pg’-Ls. It evaluates the

changes in the upper lip.

20

6. Li-Ils/FH : Angle formed by the line Li-Ils to FH plane. It evaluates the inclination of lower

lip.

7. Sn-Ls/FH : Angle formed by the line Sn-Ls to the FH plane. It evaluates the inclination of

the upper lip.

LINEAR PARAMETERS FOR SOFT-TISSUE EVALUATION :

1. G-Pg’ : It is measured by drawing a line perpendicular to glabella and parallel to HP and

gives an indication of mandibular prognathism (or) retrognathism.

2. G-Sn and Sn-Mn (HP) : The ratio of middle third facial height to lower third facial height is

measured perpendicular to HP. Ratio should be approximately 1:1.

3. Sn-Gn and C-Gn : Ratio of distance from subnasale to gnathion and cervical point to

gnathion is measured. Ratio is little larger than 1. It explains the relation of the neck to

the projection of the chin.

4. Li to (Sn to Pg’) : A line is drawn from subnasale to soft tissue pogonion and measured

perpendicular to the most prominent point of the lower lip. It indicates the lip position in

antero-posterior direction.

5. Ils to (Li-Pg’) : The labiomental sulcus is measured from the depth of the sulcus

perpendicular to Li-Pg’ line, evaluates whether the sulcus is deep (or) shallow.

6. E-line : A line drawn from tip of the nose to the soft tissue pogonion evaluates the position

of upper lip and lower lip.

7. Pg-Pg’ : Measurement obtained from a line drawn from hard tissue pogonion to soft

tissue pogonion, evaluates the thickness of the soft tissue chin.

8. Ls-U1,/Sls-A : It is the ratio obtained by lines drawn from Ls to U1, and Sls-A. It

evaluates the thickness of upper lip.

9. Sls-Ls : It is the linear distance from Sls to Ls. It evaluates the curvature of upper lip.

Measurements for Dental Evaluation :

1) Isi-Isa/Iii-Iia (Interincisal angle) : It is the angle formed by the intersection of lines from Isi-

Isa and Iii-Iia. It evaluates the relationship between the upper and lower incisor

inclination.

2) Iii / Isi (Horizontal) : The linear distance between Iii and Isi. It evaluates the sagittal

relationship between maxillary and mandibular incisors.

3) Iii/Isi (Vertical) : The linear distance between Iii and Isi. It evaluates the vertical

relationship between maxillary and mandibular incisors.

4) Iii-Iia/MP : It is the angle formed by line joining Iii and Iia to mandibular plane. It evaluates

the inclination of lower incisor in relation to mandibular plane.

21

5) Iii/A-Pg : The linear distance between the line from A to Pg and Iii. It evaluates the lower

incisor inclination in relation to maxilla and mandible.

22

ARMAMENTARIUM USED IN THE STUDY

23

24

25

26

27

28

RESULTS

The present study consists of 8 patients who were in the age group of 17 to 25 years with a

mean age of 21 years. Lateral cephalograms; pre-treatment, pre-surgical and post-surgical

were taken in habitual occlusion. The surgical technique performed was bilateral sagittal

split osteotomy for mandibular setback with rigid internal fixation by screws. The magnitude

of setback was between 4-6 mm.

To evaluate the dento-skeletal and soft tissue changes, pre-treatment and pre-surgical

cephalograms were superimposed over post-surgical cephalogram with Ba-Na line

registered at CC-point.

To compare pre-treatment, pre-surgical values with post-surgical values paired t-test

was used. A P-value of <0.05, 0.01 was considered to be statistically significant (S), P-value

<0.001 Highly significant (HS) and P-value > 0.05 to be insignificant statistically (NS).

SNB :

The mean difference between pre-surgical and pre-treatment is 0.25 (0.46) (NS),

between post-surgical and pre-treatment is –4.38 (1.69) (HS) and between post-surgical

and pre-surgical is –4.63 (1.85) (HS).

ANB :


between post-surgical and pre-treatment is 4.75 (0.71) (HS) and between post-surgical and

pre-surgical is 4.63 (1.06) (HS).

N-A/Pg-A :

The mean difference between pre-surgical and pre-treatment is –0.75 (1.16) (NS),

between post-surgical and pre-treatment is 2.50 (2.62) (S) and between post-surgical and


MP-HP :


between post-surgical and pre-treatment is 0.75 (1.75) (NS) and between post-surgical and

pre-surgical is 0.75 (1.75) (NS).

N-Pg/FH :

The mean difference between pre-surgical and pre-treatment is -0.50 (0.53) (S),



29

N- B (11 HP) :

The mean difference between pre-surgical and pre-treatment is 0.75 (0.46) (S),



N-Pg (11 HP) :

The mean difference between pre-surgical and pre-treatment is -0.63 (0.92) (NS),



N-Pg (11 FH) :

The mean difference between pre-surgical and pre-treatment is -0.50 (0.53) (S),



ANS-Mn :


between post-surgical and pre-treatment is –0.25 (2.05) (NS) and between post-surgical

and pre-surgical is –0.63 (1.60) (NS).

Go to Pg :




G-Sn-Pg’ :




Sn-Gn-C :

The mean difference between pre-surgical and pre-treatment is –0.75 (0.71) (S),



Cm-Sn-Ls :




30

Ns-Pg’/FH :




NS-Pg’/Pg’-Ls :




Li-Ils/FH :




Sn-Ls/FH :



and pre-surgical is -1.88 (0.99) (HS).

G-Pg’ (11HP) :




G-Sn and Sn-Mn ( HP) :




Sn-Gn and Gn-C :




Li to (Sn-Pg’) :

The mean difference between pre-surgical and pre-treatment is 0.88 (0.35) (HS),


pre-surgical is –0.88 (1.46) (NS).

31

Ils to (L1-Pg’) :



pre-surgical is 2.13 (1.81) (S).

E-Line :


between post-surgical and pre-treatment is –0.11 (1.00) (NS) and between post-surgical

and pre-surgical is –0.85 (3.13) (NS).

Pg-Pg’ :




Ls-U1/Sls-A :



pre-surgical is –0.01 (0.06) (NS).

Sls – Ls :




Isi – Isa /Iii - Iia :



pre-surgical is 0.75 (0.71) (S).

Iii/Isi (HOR) :




Iii/Isi (VERT) :The mean difference between pre-surgical and pre-treatment is –0.63 (0.52)

(S), between post-surgical and pre-treatment is 0.38 (0.74) (NS) and between post-surgical

and pre-surgical is 1.00 (0.53) (S).

32

Iii-Iia/MP :




Iii/A-Pg :

The mean difference between pre-surgical and pre-treatment is 2.38 (0.52) (HS),


pre-surgical is –2.13 (1.25) (S).

In the present study two of the cases were treated with vertical reduction and

augmentation genioplasty along with setback osteotomy for mandibular prognathism.

The results in these two cases revealed that there was a significant decrease in the

lower anterior facial height and shift of point pogonion in forward and upward direction

subsequent to setback osteotomy.

The angular and linear measurements related to pogionion, soft and hard tissue angle

of facial convexity, facial plane angle, mandibular plane angle and chin throat angle showed

significant changes in those two cases.

33

SKELETAL MEASUREMENTS

Angular (Deg.)

Measure

mentT T1 T2

T1-T T2-T T2-T1

Diff. P* Diff. P Diff. P

1. SNB85.00

5.55

85.25

5.65

80.63

4.53

0.25

0.46

0.17

NS

-4.38

1.69

<.001

HS

-4.63

1.85

<.001

HS

2. ANB-2.63

1.19

-2.50

1.41

2.13

0.99

0.13

0.35

0.35

NS

4.75

0.71

<.001

HS

4.63

1.06

<.001

HS

3.

N-A/Pg-A

-3.63

2.07

-4.38

1.85

-1.13

1.36

-0.75

1.16

0.11

NS

2.50

2.620.03 S

3.25

2.19

<.01

HS

4. MP-HP25.13

3.18

25.13

3.18

25.88

4.49

0.00

0.00

1.00

NS

0.75

1.75

0.26

NS

0.75

1.75

0.26

NS

5.

N-Pg/FH

89.75

3.45

89.25

3.20

85.13

2.85

-0.50

0.530.03 S

-4.63

2.20

<.001

HS

-4.13

1.89

<.001

HS

Paired t-test

P<.05, P<.01 Significant (S)

P<.001 Highly Significant (HS)

P>0.05 Not significant (NS)

34

SKELETAL MEASUREMENTS

Linear (mm)

Measure

mentT T1 T2

T1-T T2-T T2-T1


1. N-B

11HP)

3.13

5.96

3.88

6.24

-1.25

5.06

0.75

0.46<.01 S

-4.38

1.92

<.001

HS

-5.13

1.96

<.001

HS

2. N-Pg

(11

HP)

4.75

6.41

4.13

5.69

0.63

0.92

-0.63

0.92

0.09

NS

-4.13

1.81

<.001

HS

-3.50

1.31

<.001

HS

3. N-Pg

(11

FH)

2.38

4.31

1.88

4.39

-2.00

3.21

-0.50

0.530.03 S

-4.38

1.92

<.001

HS

-3.88

1.89

<.001

HS

4. ANS-

Mn

72.00

9.91

72.38

9.38

71.75

9.91

0.38

0.92

0.28

NS

-0.25

2.05

0.74

NS

-0.63

1.60

0.30

NS

5. Go to

Pg

83.75

4.23

83.75

4.23

79.13

3.72

0.00

0.0

1.00

NS

-4.63

0.92

<.001

HS

-4.63

0.92

<.001

HS

35

SOFT TISSUE MEASUREMENT (Changes)

Angular (Deg.)

Measure

mentT T1 T2

T1-T T2-T T2-T1


1. G-Sn-

Pg’

10.00

3.59

9.75

3.58

13.38

2.83

-0.25

0.71

0.35

NS

3.38

0.92

<.001

HS

3.63

1.06

<.001

HS

2. Sn-Gn-

C

99.50

6.57

98.75

6.61

103.75

6.34

-0.75

0.710.02 S

4.25

0.89

<.001

HS

5.00

1.20

<.001

HS

3. Cm-

Sn-Ls

92.75

11.08

93.25

7.30

97.50

8.04

0.50

4.75

0.77

NS

4.75

6.39

<.001

HS

4.25

2.66

<.001

HS

4. Ns-

Pg’/FH

91..88

3.56

92.13

3.72

88.00

3.63

0.25

0.46

0.17

NS

-3.88

0.64

<.001

HS

-4.13

0.35

<.001

HS

5. NS-

Pg’/Pg’-

Ls

13.13

3.91

12.63

1.31

16.13

3.23

-0.50

0.53<.05 S

3.00

1.20

<.001

HS

3.50

1.41

<.001

HS

6.

Li-Ils/FH

49.63

8.11

50.75

7.94

46.38

8.47

1.13

0.64<.01 S

-3.25

1.98

<.001

HS

-4.38

1.60

<.001

HS

7

Sn-Ls/FH

97.75

11.61

96.50

11.65

94.63

11.39

-1.25

0.89<.01 S

-3.13

0.83

<.001

HS

-1.88

0.99

<.01

HS

36

SOFT TISSUE MEASUREMNETS (Changes)

Linear (mm)

Measure

mentT T1 T2

T1-T T2-T T2-T1


1. G-Pg’

(11

HP)

4.50

8.64

4.63

8.86

0.50

8.05

0.13

0.35

0.35

NS

-4.00

1.07

<.001

HS

-4.13

1.13

<.001

HS

2. G-Sn

&

Sn-Mn

(HP)

0.94

0.18

0.94

0.18

0.95

0.16

0.00

0.0

1.00

NS

0.01

0.03

0.77

NS

0.00

0.0

1.00

NS

3. Sn-Gn

& Gn-C

1.53

0.28

1.53

0.29

1.60

0.35

0.00

0.06

1.00

NS

0.07

0.12

0.13

NS

0.07

0.09

0.06

NS

4. Li to

(Sn-Pg’)

6.38

1.85

7.25

1.75

6.38

2.62

0.88

0.35

<.001

HS

0.00

1.51

1.00

NS

-0.88

1.46

0.13

NS

5. Ils to

(Li-Pg’)

3.13

3.09

3.13

3.09

5.25

4.68

0.00

0.0

1.00

NS

2.13

1.81<.05 S

2.13

1.18<.05 S

6. E-Line-0.71

2.78

0.03

4.82

-0.83

2.00

0.74

2.18

0.37

NS

-0.11

1.00

0.76

NS

-0.85

3.13

0.47

NS

7. Pg-Pg’10.63

3.81

10.63

3.81

11.88

3.48

0.00

0.0

1.00

NS

1.25

0.46

<.001

HS

1.25

0.46

<.001

HS

8. Ls-

U1/Sls-A

0.67

0.11

0.71

0.10

0.71

0.09

0.05

0.05<.05 S

0.04

0.04<.05 S

-0.01

0.06

0.76

NS

9. Sls-Ls7.50

2.07

7.63

2.26

6.25

1.83

0.13

0.35

0.35

NS

-1.25

0.46

<.001

HS

-1.38

0.52

<.001

HS

37

DENTAL MEASUREMENTS

Measure

mentT T1 T2

T1-T T2-T T2-T1


1. Isi-

Isa/Iii-Iia

126.88

9.75

131.13

3.56

131.88

3.91

4.25

7.74

0.16

NS

5.00

7.48

0.10

(NS)

0.75

0.71<.05 S

2. Iii/Isi

(HOR)

-2.25

1.28

-3.75

1.58

1.25

0.71

-1.50

2.33

0.11

NS

3.50

0.76

<.001

HS)

5.00

1.77

<.001

HS

3. Iii/Isi

(VERT)

1.75

0.89

1.13

0.64

2.13

0.35

-0.63

0.52<.05 S

0.38

0.74

0.20

(NS)

1.00

0.53<.01 S

4. Iii-

Iia/MP

91.75

4.10

97.13

6.58

98.13

5.30

5.38

4.17<.01 S

6.38

3.16

<.001

HS)

1.00

1.41

0.09

NS

5. Iii/A-

Pg

7.13

2.70

9.50

2.73

7.38

3.38

2.38

0.52

<.001

HS

0.25

1.04

0.52

(NS)

-2.13

1.25<.01 S

38

LINEAR SAGITTAL CHANGES OF SOFT TISSUE LAND MARKS AFTER MOVEMENTS OF

SKELETAL LANDMARKS (EXPRESSED IN PERCENTAGE)

Ls Li Ils Pg’

B

(-4.5)

-0.9

(20%)

-3.75

(83%)

-4.3

(96%)

-4.38

(97%)

Pg

(-4.5)

-0.65

(14%)

-3.09

(69%)

-3.70

(82%)

-3.90

(87%)

39

CASE : 1

PRE-TREATMENT PRE-SURGICAL POST-SURGICAL

SUPERIMPOSITION : BASION-NASION AT CC POINT

Pre-Treatment

Pre-Surgical

Post-Surgical

40

CASE : 2



Pre-Treatment

Pre-Surgical

Post-Surgical

41

CASE : 3



42

Pre-

Treatment

Pre-Surgical

Post-Surgical

CASE : 4



43

Pre-Treatment

Pre-Surgical

Post-Surgical

CASE : 5


Pre-Treatment

Pre-Surgical

Post-Surgical

44

CASE : 6


Pre-Treatment

Pre-Surgical

Post-Surgical

45

CASE : 7


Pre-Treatment

Pre-Surgical

Post-Surgical

46

CASE : 8


Pre-treatment

Pre-Surgical

Post-Surgical

47

48

0.75

-4.38

-5.13

-0.63

-4.13

-3.50

-0.50

-4.38

-3.88

-6.00

-5.00

-4.00

-3.00

-2.00

-1.00

0.00

1.00

T1-T T2-T T2-T1 T1-T T2-T T2-T1 T1-T T2-T T2-T1

GRAPH - IIIN-B(||HP) N-Pg(||HP) N-Pg(||FH)

0.38

-0.25

-0.63

0.00

-4.63 -4.63

-5.00

-4.50

-4.00

-3.50

-3.00

-2.50

-2.00

-1.50

-1.00

-0.50

0.00

0.50

T1-T T2-T T2-T1 T1-T T2-T T2-T1

GRAPH - IVANS-Mn Go to Pg

49

-0.25

3.383.63

-0.75

4.25

5.00

0.50

4.75

4.25

-1.00

0.00

1.00

2.00

3.00

4.00

5.00


GRAPH - V G-Sn-Pg' Sn-Gn-C Cm-Sn-Ls

0.25

-3.88-4.13

-0.50

3.00

3.50

1.13

-3.25

-4.38

-1.25

-3.13

-1.88

-5.00

-4.00

-3.00

-2.00

-1.00

0.00

1.00

2.00

3.00

4.00

T1-T T2-T T2-T1 T1-T T2-T T2-T1 T1-T T2-T T2-T1 T1-T T2-T T2-T1

GRAPH - VI Ns-Pg'/FH Ns-Pg'/Pg'-Ls Li-Ils/FH Sn-Ls/FH

50

0.13

-4.00 -4.13

0.00 0.01 0.00

0.00

0.07 0.07

-4.50-4.00-3.50-3.00-2.50-2.00-1.50-1.00-0.500.000.50


GRAPH - VII G-Pg' G-Sn & Sn-Mn(|_HP) Sn-Gn & Gn-C

0.88

0.00

-0.88

0.00

2.13 2.13

0.74

-0.11

-0.85

-1.00

-0.50

0.00

0.50

1.00

1.50

2.00

2.50


GRAPH - VIIILi to(Sn-Pg') Ils to (Li-Pg') E-Line

0.00

1.25 1.25

0.05 0.04

-0.01

0.13

-1.25-1.38

-1.50

-1.00

-0.50

0.00

0.50

1.00

1.50


GRAPH - IX Pg-Pg' Ls-U1/Sls-A Sls-Ls

51

4.25

5.00

0.75

-1.50

3.50

5.00

-0.63

0.38

1.00

-2.00

-1.00

0.00

1.00

2.00

3.00

4.00

5.00


GRAPH - X Isi-Isa/Iii-Iia Iii/Isi(Hor) Iii/Isi(VerT)

5.38

6.38

1.00

2.38

0.25

-2.13

-3.00

-2.00

-1.00

0.00

1.00

2.00

3.00

4.00

5.00

6.00

7.00

T1-T T2-T T2-T1 T1-T T2-T T2-T1

GRAPH - XIIii-Iia/MP Iii/A-Pg

52

DISCUSSION

The untreated mandibular prognathism patient presents with a discrepancy in jaw size

or position between the maxilla and the mandible. Commonly, the teeth are partially

compensating for the discrepancy. The mandible is relatively too far anterior and

consequently the lower incisors are usually tipped posteriorly. The maxillary incisors are

more variable but most often are anteriorly inclined in varying degrees.

Orthodontic correction alone of such a problem must be designed to push these

dental compensations to even greater amounts. Clearly, this is often an unstable and

esthetic compromise when gross discrepancies in jaw size or position exist. In the

orthodontic surgical approach the presurgical orthodontic objectives are just the opposite. All

dental compensations are removed. When the teeth are appropriately related to their

respective jaws, the jaw to jaw discrepancy will appear clinically more severe. This is not only

desirable but beneficial to treatment. The interdigitation requirements of the dentition

determine the positioning of the jaws at surgery. Surgery done in the presence of abnormal

tooth positions will result in jaw positioning dictated by these same tooth positions. Usually

this will mean only a partial correction of the mandibular prognathism. If the discrepancy has

been temporarily worsened by removing dental compensations, the surgery can fully correct

the jaw imbalance.

Class III patients typically have a concave profile characterized by an upper lip with a

turned up contour that is too far behind the esthetic line, small nasolabial angle, a protrusive

lower lip, and a poorly defined mentolabial fold.

The first report of a surgical procedure used in the correction of a mandibular

deformity was by Hullihen in 1849.1 He described an osteotomy procedure which effectively

lengthened the body of the mandible. In 1898 Blair,1 who pioneered the surgical correction

of mandibular prognathism, presented a report on a resection of the mandible in the bicuspid

area, a procedure which severed the nerve and blood supply of the mandible.

In early 1960’s surgical procedures for mandibular prognathism became common after

intraoral approach to orthognathic surgery was popularized by European surgeons,

particularly Trauner and Obwegeser.33 Modifications in osteotomy design, the evolution of

special instrumentation for stabilization and the versatility of the procedure for fixation

allowed for corrections in three planes of space making the sagittal split osteotomy, the

mandibular procedure most often performed today.

The basic osteotomy pattern includes horizontal cuts through the mandibular cortical

bone first on the medial side above the lingula, down the anterior ramus on to the superior

aspect of body of the mandible and then curving inferiorly through the cortical plate including

53

the inferior border. These cuts may be made with a rotary instrument or with the

reciprocating saw and should extend only through the cortex and slightly into the medullary

bone. Following these basic principles, bony parts were reduced into the desired position,

stabilized and then fixed by rigid internal fixation. The main advantages of this form of fixation

compared to intermaxillary one are;

1. Shorter period of intermaxillary immobilization and

2. Primary bone healing is attained by the use of compression allowing the union of bony

fragments to take place much earlier.

When properly managed, rigid fixation techniques are exacting and leave little room

for error in planning or performance of the surgical procedures.

In general, posterior repositioning of the mandible by bilateral sagittal split osteotomy

yields a significant change at the chin, labiomental fold and the lower lip selective to the

antero-posterior bone change and in contrast a mild posterior movement of the upper lip.

The upper lip retruded and lengthened after mandibular setback surgery as shown by

other studies (Lines and Steinhauser, 20%; Hershey and Smith, 20%; Kajikawa, 15% to

25%; Gjorup and Athanasiou, 16%; Bengt Ingerwal, 23% ; Karim Mobarak, 25%).

In the present study the upper lip, retruded an average of 20% and 14% of the

setback of point-B and Pogonion respectively.

Assessment of the results of the present study demonstrated that considerable facial

changes and improvement took place following the mandibular setback. The skeletal and soft

tissue facial profiles were straightened and posture of lips was improved. The normal incisal

relationship that was achieved became influential on the soft tissues overlying both incisors

and led to better lip competence and posture.

The upper part of the lower lip generally does not follow the setback of the hard tissue

as closely as the labial fold or the soft tissue chin follows the hard tissues. In other studies

the net effect for the lower lip has been found to vary between 66% and 105% (Bjork et al

92% to 105%, Lines and Steinhauser, 75%, Hershey and Smith 98%, Suckiel and Kohn

83%, Kajikawa, 66% to 75%, Group and Athanasiou, 93%, Bengt Ingervall, 88%; Karim

Mobarak, 100%).

In the present study the lower lip followed the point-B and pogonion by 83% and 69%

respectively.

An additional factor was the relative deeping of mentolabial fold in relation to hard

tissue structures as reported by several authors (Kojikawa, 92% to 112% ; Gjorup and

Athanasiou, 103%; Bengt Ingerval, 106%; Karim Mobarak 100%). The soft tissue chin and

mentolabial fold generally follow their corresponding bony structures in about 1:1 ratio.

54

The present study showed that posterior movements at point-B and pogonion was

accompanied by deepening of mentolabial sulcus by 96% and 82% respectively.

The effects on the soft tissue chin due to hard tissue changes as described in other

studies are Bjork et al 88% - 97%, Liner and Steinhauser, 100%; Messley and Smith, 90%;

Suckiel and Kohn, 95%; Kojikawa,80% - 104%; Gjroup and Athanasiou 91%; Bengt

Ingervall,107%; Karim Mobarak 94%.

In the present study the posterior movement of soft tissue chin following point-B and

pogonion was 97% and 87% respectively. While there was increase in the soft tissue chin

thickness.

A study of this kind may contain a certain amount of inherent error in the form of

radiograph tracing error, differences in muscular tonus on radiographs of the same patient,

and error in locating the rather vaguely defined soft tissue landmarks. This type of error may

mask or exaggerate the relatively small changes in soft tissue.

It appears reasonable to assume that, with further cephalometric investigation of all

the various aspects of the surgical correction of mandibular prognathism, a more objective

diagnosis and prognosis could be made.

55

SUMMARY AND CONCLUSION

A sample of 8 patients were evaluated retrospectively after an average of 2 months of

surgical setback of the mandible. The age group of these patients was from 17 to 25 years

with a mean age of 21 years. The purpose of this study was to see how closely the soft

tissues are related to the underlying skeleton after mandibular setback osteotomy. Pre-

treatment, Pre-surgical and post-surgical lateral cephalograms were taken in habitual

occlusion with lips at rest position. The surgical technique performed was bilateral sagittal

split osteotomy for mandibular setback with rigid internal fixation. Various hard and soft

tissue, angular and linear parameters from Legan-Burstone, McNamara’s, Steiner’s,

Rickett’s, Holdaway and Rokosi’ Jarabak analysis were employed in this study to compare

the pre-treatment, pre-surgical and post-surgical lateral cephalograms of the patients treated

with mandibular setback osteotomy.

The conclusions indicated from this study were as follows :

1. The facial concavity, in regard to the relationship of the hard and soft tissue chin to the

upper face, was decreased by this surgical procedure; facial esthetics was improved.

2. The mandible was repositioned posteriorly in all cases and the lower denture base

assumed a more normal relationship to the upper denture base.

3. The changes in angulation of the skeletal analysis measurements showed varying

degrees of correlation to the posterior displacement of the chin (pogonion).

4. The soft tissue contour of the upper lip, the maxillary sulcus of the upper lip, the lower lip,

the mandibular sulcus of the lower lip, and the soft tissue chin were altered by the

surgical procedure.

5. The least amount of change of the soft tissue profile was exhibited by the upper lip and

maxillary sulcus of the upper lip. There was a tendency for the upper lip to be slightly

posteriorly displaced, and the maxillary sulcus contour of the upper lip to become more

obtusely angulated after the surgical procedure.

6. The greatest amount of change of the soft tissue profile was exhibited by the lower lip, the

mandibular sulcus of the lower lip, and the soft tissue chin. The lower lip and the soft

tissue chin were posteriorly displaced in all cases with a tendency for a downward

displacement. There was also a tendency for the mandibular sulcus contour of the lower

lip to become more acutely angulated.

7. The lower lip and the soft tissue chin, being posteriorly repositioned in all cases, assumed

a better esthetic relationship to the rest of the soft tissue profile.

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