pre-surgical procedures in orthognathic surgeries of mandible
DESCRIPTION
This is about the pre-surgical procedures which have to be analyzed before the orthognathic surgeries of mandible.TRANSCRIPT
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