Pre-Surgical procedures in orthognathic surgeries of mandible.

ORTHOGNATHIC SURGERIES OF MANDIBLE

By:

Dr. R. Seshan Rakkesh. B.D.S

Introduction Types of Skeletal and Dentofacial deformities. Associated problem list. Clinical features. Treatment List. Presurgical Analysis Collecting patient data Frontal view analysis Profile

Final treatment options.

Synopsis:

Defenition: It is the surgery in which the jaw bones are intentionally

sectioned at various sites to correct the dentofacialdeformities and then repositioned at the desired position.

Osteotomy: Simple splitting of the bone.

Ostectomy: Removal of part of the bone .

Introduction:

Dentofacial deformities are considered in three planes

- Antero posterior plane

- Vertical plane

- Transverse plane

Mandibular

Excess : Mandibular prognathism

Deficiency : Mandibular retrognathism

Maxilla

Excess : Vertical Maxillary Excess (VME)

Deficiency : Vertical Maxillary Deficiency (VMD)

Types of Severe Skeletal and DentofacialDeformities.

Combination

Bimaxillary protrusion.

Nasomaxillary hypoplasia associated with prognathicmandible.

Nasomaxillary hypoplasia associated with cleft lip and palate.

Facial Symmetry

Asymmetric prognathism of the mandible.

Unilateral condylar hyperplasia.

Hemifacial hypertrophy (rare)

Clinical Features:

• Facial Features:

1. Prominent chin is the dominant feature

2. A Concave profile.

3. Lip incompetance.

4. Obtuse gonial angle.

5. Middle third of the face appears to be deficient.

6. Labiomental fold may be diminished / absent.

7. Nasolabial angle may be acute.

8. Anterior facial height may be increased.

MANDIBULAR EXCESS:

• Dental Features:

1. Angle’s class III malocclusion will be seen.

2. Reverse horizontal overjet in the incisor area.

3. Posterior cross bite.

4. Maxillary teeth may be protrusive.

5. Mandibular anterior teeth may be tilted lingually

6. An anterior open bite may be seen.

Facial features:

Convex profile.

Bird face deformity.

Short upper lip.

Everted lower lip.

Acute gonial angle.

Lip strain evident during closure of mouth.

MANDIBULAR DEFICIENCY

Dental features:

Angle’s class II molar malocclusion.

Increased overjet.

Accentuated curve of spee of lower anterior.

Fanning of lower anterior teeth or crowding.

Skeletal deep bite may be present.

Asymmetrical mandibular prognathism. With anterior open bite .

Without anterior open bite.

Unilateral condylar hyperplasia. Hemimandibular elongation.

Hemimandibular hypoplasia.

Hemifacial hypertrophy (rare).

CONDITIONS WITH FACIAL ASYMMETRY.

With Anterior open bite: Severe facial asymmetry

Eccentric bilateral mandibular protrusion.

Deviation of the chin.

High gonial angle.

Midline of mandibular arch shifted

Without anterior open bite: Eccentric bilateral mandibular protrusion.

Deviation of chin.

Class III dental malocclusion.

Associated mandibular hypoplasia.

Asymmetrical mandibular prognathism

Hemimandibular Elongation: Horizontal displacement of mandible & chin to

unaffected side.

Lateral crossbite on unaffected side.

Occlusal plane slopes upward to the unaffected side.

Sever cases – Lateral open bite on the affected side.

IOPA, OPG – Elongation of the condyle.

Hemimandiblar hyperplasia: One side of face enlarged.

Unilateral bowing of inf. Border of mandible.

Lip line slopes downward on affected side.

Associated TMJ pain symptoms on the affected side.

RADIOLOGICALLY – Enlagered hemimandible on the

affected side.

Unilateral Condylar Hypoplasia

Esthetic problem.

Functional problems.

Psycological problems.

Impairment of mastication.

Associated speech problems.

Succeptibility to caries and periodontal problems.

Possibe TMJ joint pain dysfunction.

Impact on digestion – general health.

ASSOCIATED PROBLEM LIST

Severe skeletal dentofacial deformity can be corretedby:

Growth modification.

Orthodontic camouflage.

Orthognathic surgery.

TREATMENT OPTIONS

Useful in children where the growth potential and modification of growth can be achieved.

Achieved using. High pull headgear – complete or partial maxillary fixed

appliance.

Myofunctional appliance – 14 to 16 hrs a day.

Limitations – only small amount of changes can be brought.

GROWTH MODIFICATIONS

Biologically accepted compensations, to mask the skeletal malocclusion by orthodontic treatment.

Done only if:

Orthodontist is able to carry out biologically acceptable dental compensations.

With desired soft tissue results.

Willingness of patient to cooperate.

Growth potential study is done.

ORTHODONTIC CAMOUFLAGE

Surgical repositioning of the jaw and / or dentoalveolar segments.

For correction of severe skeletal discrepancy.

ORTHOGNATHIC SURGERY

Achieve best function.

Achieve best aesthetics.

Achieve best stability.

Oral and Maxillofacial surgeons and Orthodontist are equal partners.

Objective of surgery

Can be done only when the patient is in actively growing stage.

Must be warned about the resurgery later on.

Best timing is when the growth potential of patient is over.

Timing of surgery

Phase 1: Assemble the database. Synthesize the problem list. Diagnosis. Team conference.

Phase 2: Interdisciplinary problem list. Dentofacial problems in order of priority. Tentative treatment plan. Patient / team conference. Definitive plan.

Diagnosis and Treatment planning

Phase 3: Preparatory therapy – endodontic periodontics, prosthesis.

Definitive orthodontic – surgical treatment.

Continuous team monitoring, re-evaluation, interaction, modifying therapy.

Phase 4: Maintenance.

Produce a concise list of patient’s problems.

Synthesize the various treatment possibilities into a rational plan that gives maximum benefit to patient.

Goal of surgery

Personal data. Facial esthetic analysis. Lateral cephalometric analysis Occlusal analysis and Model analysis

Dental arch form Dental alignment Dental occlusion. Tooth mass relation

Final treatment plan Presurgical orthodontics. Surgery plan Postsurgical orthodontics Maintenance.

STEPS IN PROCESS

Two types of facial analysis is done before the surgery. They are. Frontal view analysis Profile / lateral view analysis

Face is divided into-upper third -middle third-lower third

Face evaluation-patient is asked to sit in upright position -pupillary plane ,plane of ear,frankfort horizontal

plane parallel to the floor-patient should be examined with the teeth in centric

position, relaxed lips& in straight position

Facial esthetic analysis

14 landmarks are to be assessed in the front view analysis as recommended by LARRY WOLFORD.

Forehead, eyes, orbits and nose – symmetry, size and deformity.

Normal intercanthel distance is 32 + 3mm. Normal intepupillary distance is 65 + 3mm. Intercanthal distance, alar bone width and palpebral fissure

width must be equal.. 1/2* intercanthal distance = width of nasal dorsum.

2/3* intercanthal distance = width of nasal lobule. Vertical line through medial canthus and perpendicular to the

pupillary plane should be + 2mm on the alar bases. Upper lip

males – 22 + 2mmfemales – 20 + 2mm

Frontal view analysis

Normal upper tooth to lip relationship exposes 2.5 + 1.5 mm of incisal edge with lips in repose.

Face should be reasonably symmetric, both vertically and transversely.

lip incompetence if present should be measured from upper lip stomion to lower lip stomion in centric occlusion and lip repose (0-3 mm)

Smile line –

The vermilion of the upper lip should fall at the cervicogingivalmargin with 1-2 mm of exposed gingiva. ( asked to give full smile to detect a ‘gummy smile’).

The distance from the gabella to subnasal and subnasal to menton should be 1:1.(upper lip length normal).

The length of the upper lip should be 1/3 the length of lower facial third.

Lower eyelid in level with or slightly above most inferior aspect of iris.

For determining vertical and antero -posterior plane problems of the jaws.

Facial profile can be: Straight profile.

Convex profile.

Concave profile.

Profile or Lateral view analysis

Facial contour angle :

Relative cancavity or convexity of the facial profile.

Normal -> -8 to -11 degrees.

Formed between the upper facial contour plane and the upward extension of the lower facial contour plane.

If angle is anterior to the upper contour plane then it is negative.

Nasolabial angle :

Formed at the subnasale by a line drawn tangent to the base of the nose with a line from the upper lip to subnasale.

Normal -> 100 ° to 110° in males and 110 ° to 120 ° in female

Larger angulation indicates convex face ( associated to recessive chin).

Lip position : Upper lip must protrude over lower facial contour plane by

3.5mm.

Lower lip protrude by 2.2mm.

Lower lip, Chin-throat angle : Angle between a line from the lower lip to the soft tissue

pogonion and a line drawn tangent to the soft tissue contour below body of mandible.

Normal -> 110 ° + 8 °.

Larger angulation indicates recessive chin.

Lower angulation indicated excessive chin.

Chin to throat length : Distance between angle of the throat and soft tissue menton.

Normal -> 51 + 6 mm.

Increased value shows concave face and acute lower lip, chin throat angle.

Forehead Nasofrontal angle

Eyes Interpupillary distance – 6.5 mmIntercantha distance – 3.5 mmOutercanthal disance – 9.8 mm

Nose Length, width, projection and nasolabial angle - 90° to 120°

Lips Interlabial gap – 3 mmLength, width, procumbency and recumbency

Chin Mentolabial sulcus, lip chin complex,Prominence and deficiency.

Evaluation of 5 major esthetic masses of the face.

Basic occlusal relationship

Anterior overbite or open bite

Anterior overjet and any cross bite

Health of the dentition

Tooth size discrepancies

Curve of wilson & spee

Dental crowding

Missing, carious, periodontal evaluation

Anatomical functional tongue abnormalities

Dental modal analysis

Oral Examination

CEPHALOMETRIC ANALYSIS

By SALZMAN(1964)

Establishing two dimensional relationships of craniofacial components

Classifying skeletal &dental abnormalities

Analyzing growth & development responsible for dentofacial pattern

Planning treatment for orthodontic

Determining dentofacial growth changes at after treatment

Predicting hard & soft tissue contours

SOFT TISSUE LANDMARK

Glabella

Soft tissue nasion

Subnasaale

Labiale superius

Labiale inferius

Soft tissue pogonion

Soft tissue menton

Angle of throat

The upper&lower facial contour plane

CEPHALOMETRIC PREDICTION TRACING

By BELL,PROFITT,WHITE(1980)

Simple and accurate method of prediciting results

Quantification of the surgical movements

Accurately predict the resultant facial profile

Provides a visual aid with a single overlay

Comparing with actual postsurgical

cephalometric tracing for re-evaluating

the surgical results

Posteroanterior cephalometricanalysis

Assessing asymmetry of the facial skeleton by using three vertical lines

FIRST LINE-Midline of nose&chin&dentalarch

SECOND LINE-Line passing through zygomatic arch

THIRD LINE-Passing through the angle of the mandible

CEPHALOMETRIC POINTS&PLANES

Nasion

Anterior nasal spine

Sella

Pogonion

Posterior nasal spine

Point(A)

POINT(B)

Subnasale

MADIBULAR SURGERIES

Two types of mandibular surgeries. Mandibular body osteotomies.

1. Intraoral procedures. Ant. Body osteotomy

Post. Body osteotomy

Midsymphysis osteotomy

2. Segmental subapical mandibular surgeries. Ant. Subapical mandibular osteotomy.

Post. Subapical mandibular osteotomy.

Total subapical mandibular osteotomy.

3. Genioplasties. Augmentation genioplasty

Reduction genioplasty

Straightening genioplasty

Lengthening genioplasty

Types of surgery

Mandibular ramus osteotomies

1. Subcondylar ramus osteotomy

Extraoral subcondylar ramus osteotomy(subsigmoid).

Intraoral subcondylar ramus osteotomy(subsigmoid).

Arching ramus osteotomy(extraoral).

2. Intraoral modified sagittal split osteotomy.

Mand. Body surgeries - Degloving vestibular incision intraorally.

Extra oral ramus osteotomies - submandibular Ridson’s incision and postramal Hind’s incision.

Intra oral ramus osteotomies – incision similar to 3rd

molar extraction.

SOFT TISSUE INCISIONS

INDICATION:

Mandibular prognathism with functional posterior occlusion

Class III malocculsion with or without anterior open bite

Anterior Body Osteotomy

INDICATION

Missing Posterior teeth

Class III deformity

For correction of Cross Bite

Posterior body steotomy

The Complete vestibular incision can be planned if it is combined with posterior or anterior body osteotomy

Midsymphysis Osteotomy

Used to reposition anterior,posterior oe entire mandibular dentoalveolar segment

Ant. Subapical mandibular osteotomy.

Post. Subapical mandibular osteotomy.

Total subapical mandibular osteotomy

Segmental Subapical MandibularSurgeries

INDICATION

Correcting mandibular dento alveolar proclination

Closing mild anterior open bite

Leveling an accentuated curve of spee

Correcting mandibular dental arch asymmetry

Used as an adjunctive with other surgical procedures:

With anterior maxillary osteotomy to correct bimaxillaryprotrusion

With mandibular advancement to level the curve of spee

With genioplasty procedure

Anterior Subapical MandibularOsteotomy

INDICATION

Uprighting the posterior segment which is in extreme linguoversion or buccoversion

Closing a Premolar or molar space

Levelling Supraerupted Posterior teeth

Posterior Subapical MandibularOsteotomy Procedure

Total Subapical MandibularOsteotomies

Genioplasty can be used as a single procedure or it can be used as an adjunctive procedure along with other major osteomies of the jaw bone.

Deformities of the chin should be considered in all 3 planes,

AP

Vertical

Transverse

It can be used to augment, reduce, straighten or lengthen the chin.

GENIOPLASTIES

Used to increase the chin projection.

Sliding horizontal osteotomy of the symphysisregion.

Autogenous bone graft

Alloplastic material – silastic, hydroxyapatite.

Augmentation Genioplasty

Reduction of the symphysis region can be achieved both in the anteroposterior and vertical planes or in both planes depending on the need of the patient.

Reduction Genioplasty

Indication:* In Facial asymmetry, where the complete correction of the

asymmetry cannot be achieved by appropriate jaw osteotomies. E.g., TM joint ankylosis.

* The horizontal osteotomy is done and segment Is shifted laterally and than contoured to get desired result.

Straightening Genioplasty Procedure

MANDIBULAR RAMUS OSTEOTOMIES

It was proposed by Caldwell – Letterman in 1954.

The indications for extraoral subsigmoid vertical ramus osteotomy are,

Major setback of mandible more than 10 mm.

Asymmetric setback of the mandible.

Reoperation of previously operated case.

Subcondylar Vertical Osteotomy

Also called as - Bilateral Sagittal Split Osteotomy

It performed on the mandibular ramus and body.

First described by Obwegeser and Trauner and later modified by Dal Pont, Hunsuck and Epker.

Transoral incision, similar to that used for IVRO.

The osteotomy splits the ramus &the posterior body of the mandible sagittally, Which allows either setback or advancement.

This is highly cosmetic procedure, as it is done intraorally plus there is broader bony contact of the osteotomised segments ensuring good healing.

Drawback:

* High level of operative skill

* Experience tominimize the surgical complication.

Intraoral Modified Sagittal Split Osteotomy