Preparation of surgical splints in bi jaw surgery

SRGICAL SPLINT PREPARATION FOR ORTHOGNATHIC SURGERY

1. PREPARATION OF SURGICAL SPLINTS IN BI JAW SURGERY Presented by Sai kiran.K

2. Surgical orthodontics is a term that refers to surgical procedures carried out as an adjunct or conjunction with orthodontic treatment Surgical procedures are carried out to correct severe dentofacial abnormalities that cannot be treated by growth modification procedures or orthodontic camouflage  

3. The planning of orthognathic surgery is done in a methodical order. Steps involved are : 1. Pre operative evaluation 2. Pre surgical orthodontics 3. Mock surgery 4. Surgery and stabilization 5. Post surgical orthodontics

4. INDICATIONS: Severe Dento -facial Deformities

5. Cleft patients

6. Asymmetries

7. 1. Preoperative Evaluation Systematic evaluation of the patient with dentofacial deformity : To adequately evaluate individuals with dentofacial deformities and subsequently plan treatment for them certain examinations are done in the routine.

8. A. General patient evaluation : 1. Medical history 2. Dental evaluation a)Dental history consideration b)General dental consideration c) Periodontal consideration B. Socio psychologic evaluation  C. Esthetic facial evaluation 1. Frontal analysis 2. Profile analysis  

9. D. Lateral cephalometric evaluation 1. soft tissue relations 2. skeletal relations 3. dental relations   E. Panoramic and/or full mouth periapical radiographic evaluation    

10. 2)PRESURGICAL ORTHODONTICS Main function is to prepare the patient for surgery. Procedures undertaken are 1.Alignment of teeth 2.Space closure 3. Coordination of arches 4.Intrusion of teeth.

11. 3)MOCK SURGERY Soon after the completion of pre-surgical orthodontic treatment , mock surgery is performed on the upper and lower models , mounted on a hinged or anatomical articulator. The models are cut and repositioned in the desirable position . The segement are placed in their new position using sticky wax.Thus mock surgery helps in evaluation and modification of surgical treatment plan.It also helps in preparation of occlusal splint.

12. 4)SURGERY AND STABILIZATION Next Step involves surgical fracturing and repositioning of bony segments, the teeth of upper and lower arches and wired in occlusion to the splints. The orthodontic arch wire and brackets can be used for intremaxillary fixation and kept in place for 6-8 week following which the splint is removed

13. 5)POST SURGICAL ORTHODONTICS During this phase , final detailing of occlusion and esthetic root paralleling is done .most cases of post surgical orthodontics are completed by 4-6 months.

14. Guidelines for Positioning Casts for Splint Fabrication: Keep things symmetrical in the transverse plane Bring incisors in an ideal relationship, not overcorrecting Keep skeletal midlines correct If wire osteosynthesis/MMF, bring incisors in an edge-to-edge relation

15. MODEL SURGERY Model surgery simulates actual surgery, in the dental arch models of the patient. It gives the three dimensional understanding of the post operative relationship of the jaws. Major aims of the model surgery: -To get the definite idea about the extent of bone / arch advancement or reduction required in the surgery. - To get a post-operative relationship of the jaws, dentition and occlusion. -To decide about the post-surgical orthodontic treatment. -As a vehicle for fabrication of splints for stabilization after surgery.

16. Face-bow record To record the relation of the max to the hinge axis (condyles) To establish the same relation b/n the max cast and the mechanical hinge of the articulator

17. Conditions where facebow transfer is required: -If the condyles will be separated from the dentition, there is no advantage in maintaining this relationship during model surgery -Arbitrary articulator is satisfactory. -If the condyle dentition relationship will be preserved at surgery and the mand will rotate to a new position ,which occurs primarily when the max is repositioned without mand ramus surgery. -In 2-jaw surgery,the mand position with the condyle intact is the guide for positioning the max before the mand surgery is completed.

18. Semi Adjustable Articulator Allows the manipulation of the max and mand casts in 3 planes of space within the articulator When mounted the manipulation will be analogous to surgical movements of the jaws with the face

19. Procedure Patient is made to sit upright. Orbitale is marked –by palpating the infraorbital rim. Softened piece of base plate wax is wrapped around the bite fork and positioned around the max teeth, pressed into max teeth to get indentations. Ear pieces are placed in position, orbitale pointer should coincide with the orbitale reference point. All locking screws are tightened. This assembly is positioned on the articulator.

20. Model Surgery- Mandibular surgery Patient’s maxilla is used as template. As the maxillary position remains constant, semi adjustable articulator and face bow transfer are not always required.

21. Max and mand casts are held together in ideal relationship ,secured with sticky wax and then plaster mounted on a simple hinge articulator in the desired occlusion Mandible advanced to desired position

22. After the plaster has set the casts are separated and the single hinge motion of the articulator will allow accurate reproduction of occlusal relationship and mand rotation for construction of surgical template.

23. Final surgical splint is constructed of acrylic resin

24. Combined max and mand surgery In this technique, in addition to the impressions and sqash bite, a face-bow recording is taken. The working models are anatomically trimmed and articulated on the semi adjustable articulator using the face-bow recording and then the standard squash bite.

25. 2. Horizontal and vertical reference lines are drawn on the mounting plaster to register the post-operative position of each maxillary and mandibular segments before surgery. Two sets of parallel horizontal lines A/A and B/B are drawn on the upper and lower models. These are easily done by rotating the detached model with the felt pen.

26. The B lines should be just clear of the apices of the teeth, and not less than 15mm from the A lines. The actual distance between the A and B lines is then recorded on the plaster. These lines will be used to plan the vertical movements.

27. 3. Three vertical lines VC, VB, VM are drawn from upper base line (A) to the lower baseline (A) on each buccal segment. These lines pass through the buccal surfaces of the upper cuspid, bicuspid and the distal cusp of the last upper molar tooth., and they are extended to their occluding partners. These will help to indicate the anteroposterior movements achieved by the model surgery. Upper and lower midlines are also drawn .

28. Marked models with the recorded distances

29. 4. The vertical distances from the buccal cusp tips of the three reference teeth to their A base lines are recorded to help calculate any vertical movements. Transverse changes are recorded by the inter-canine and inter-molar distances measured across the palate and recorded by taking reference points on the canine tips and the mesiobuccal cusp of the first molars.

30. Cuspal reference points are used for transverse changes

31. 5. When all the reference lines have been drawn and the measurements completed, the osteotomy lines are draw between A and B lines to correspond with the bone cuts. The plaster mounting assembly is then sectioned at the osteotomy sites with a saw or large abrasive disc and the whole arch or segments are repositioned in the planned post-operative position.

32. Interrupted line is the proposed osteotomy site

33. 6. After making the horizontal cut, rotate the dental midline on the model to match the facial midline on the mounting plaster. Maxilla is reassembled with the wax after the osteotomy cuts. Mandible closes in to the intermediate occusal relationship. Intermediate splint is prepared in its new position. Fabricated splint is placed on the unoperated mand and this serves to reposition the mobile max

34. Once this is stabilised the mand is repositioned in the desired occlusal relation using the final splint. This is determined using the max arch as a template.

35. Precautions: Thick splints can introduce errors if articulator mounting is not accurate,there is great possibility of error when the mand rotates into position Splint removal post surgically must occur simultaneously with removal of stabilizing wires

36. CONCLUSION: A combination of cephalometric prediction and model surgery gives the surgeon a satisfactory idea of the esthetic and occlusal result of the surgery. This also helps the team to decide on the method of combining orthodontics and orthognathic surgery.

37. References: Contemporary Orthodontics – W.R. Proffit Esthetic Orthodontics & Orthognathic Surgery - David.M.Sarver Orthodontics ; Current Principles & Techniques – T.M.Graber & R.I.Vanarsdall.Jr