surgical proedures in orthodontics


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surgical proedures in orthodontics

  1. 1. 10.2 Major surgical procedures 1. Introduction Our understanding of the concepts of craniofacial growth is continually evolving andd the application of this knowledge to clinical practice particularly to the surgical field is also enormously increasing. The surgeons now a days are able to correct the various orofacial abnormalities that have resulted from arrested and perverted development of cranio facial complex. Major surgical procedures that are undertaken concurrent with orthodontic therapy are 1. Orthognathic surgeries which deals with surgical correction of jaws. 2. Facial esthetic/cosmetic surgeries like rhinoplasty, blepharoplasty etc.., 3. facial reconstruction surgeries like cleft palate and lip repair surgeries etc.., The aim of this chapter is to provide a basic view of the principles of orthognathic surgery. Orthognathic surgery is the surgical correction of underlying skeletal anomalies or malformations involving the mandible or the maxilla.. Modification of a severe skeletal discrepancy in adults is not possible by redirection of growth as growth potential is culminated. They cannot be effectively masked by camouflage. In such adult patients surgical correction may be indicated. Orthognathic surgeries are major surgical procedures carried out along with orthodontic therapy to correct dento-facial deformities or severe oro-facial disproportions involving the maxilla, the mandible or both in combination. Surgery is not a substitute for orthodontics in these patients. Instead, it must be properly coordinated with orthodontics and other dental treatment to achieve good overall results. This orthognathic surgeries are combined surgical orthodontic procedures which involve the team work of orthodontist, an maxillofacial surgeon and some times plastic surgeon. The team, led by the orthodontist and the oral surgeon, carefully develops a problem list, which is reviewed with the patient. The desired outcome of the ideal treatment plan of orthodontic treatment and jaw surgery is to achieve stability, function, and facial balance. Malformations of the jaws or skeletal aberration may be present at birth (congenital), or they may become evident as the patient grows and develops (acquired). They can cause esthetic disharmony, structural and functional deficiencies and defects. These include disfigurement of face , masticatory problems, abnormal speech patterns, breathing problems, early loss of teeth and
  2. 2. dysfunction of the temporomandibular joint. The objective of orthognathic surgery is to restore the esthetic harmony, functional efficieny and structural balance . 2. Principle of Orthognathic surgery Orthognathic surgery basically involves planned intentional fracturing or sectioning of the facial skeletal parts and repositioning them as desired in acceptable functional position. Orthognathic surgeries can be performed in the maxilla as well as the mandible or both the jaws to correct jaw discrepancies in all the three planes of space. They can be done at the level of basal bone itself or limited to alveolar bone. They should be performed as a team with the oral surgeon and the orthodontist being important members of the team. 3. Indications of orthognathic surgery 1. Skeletal discrepancy– Significant Class II or III skeletal patterns 2. Facial imbalances or asymmetries– Long lower face, gummy smile etc.., 3. Limitations of tooth movements – Need to keep teeth relatively upright and in the bone 4. Relapse potential of orthodontic treatment– Excessive dental extrusion (vertical elastics), expansion or tipping or teeth may not be stable 4 .Steps in orthognathic surgery The planning and execution of orthognathic surgeries are done in a methodical manner. The following are the steps involved in Orthognathic surgery: i. Clinical diagnosis and evaluation ii. interdisciplinary approach and pre orthodontic dental care iii. Pre-surgical orthodontics iv. Surgical treatment objective ( STO) v. Mock surgery vi. Surgery and stabilization vii. Post-surgical orthodontics and occlusal detailing. viii. retention i. Clinical diagnosis and preoperative evaluation Pre-operative diagnosis is very important for the success of orthognathic surgery.
  3. 3. The diagnosis is aimed at determining the nature, position, severity and the possible etiology of the dento-facial deformity. The extent of the malocclusion in all the three planes is thouroughly evaluated. a. General medical evaluation : The patient’s general medical history should be recorded to rule out any systemic condition that may compromise the surgical procedure. b. Dental evaluation :- The patient’s overall dental health should be evaluated. Particular attention is paid towards the muscles of mastication and Temperomandibular joint. Pulpo -periodontal problems should be controlled prior to the surgical intervention. b. Socio – psychological evaluation : The patients is to be assessed to determine whether he /she is aware of the dentofacial deformity and expectation from treatment outcome. This helps in determining the patient's motivation towards surgery c. Cephalometric evaluation: Cephalometric evaluation is an important and obligatory tool in locating the nature and severity of the skeletal problems and in selecting the favourable sites for surgical correction. Cephalometric analyses often have been used as the cornerstone in the differential diagnostic process for skeletal imbalances. The lateral cephalogram and anteroposterior cephalogram are evaluated. The commonly used Cephalometric analysis are the Burstone analyses and the Quadrilateral analysis. Frontal cephalometric analysis helps in determining facial asymmetry. Cephalometric analyses using a Jacobson or Broadbent Bolton template method and the Moorrees mesh are able to graphically qualify (demonstrate which jaw is not in balance) and quantify (demonstrate the degree to which each jaw, both dental and skeletal component, contribute to the imbalance). The template proved to be a simple, quick, and reliable tool to demonstrate the direction and approximate amount of surgery needed to correct the skeletal disharmony Indications for surgery include the problems that are too severe for orthodontics alone. The amount and range of movement possible can be evaluated from Epker’s envelope of of discrepancies. The envelope of discrepancy outlines the limits of hard tissue change toward ideal occlusion . The limits vary both by the tooth movement that would be needed (teeth can be moved further in some directions than others) and by the patient's age . Growth potential in children helps to treat conditions by orthodontics alone ( 10mm of overjet) but the same has to be treated by surgical means in adults. . d. Radiographic examination : A complete radiographic survey of the maxillofacial region is necessary prior to the surgical intervention . Intra-oral periapical radiographs : These radiographs help in determining the
  4. 4. condition of the teeth and alveolar bone. Presence of pathology around the tooth can also be determined using these radiographs. Any pulpal or periodontal infections should be eradicated before surgery Panaromic radiographs : Orthopantomogram or OPG offers a wide range view of the entire dentofacial region. It gives us the periapical and periodontal status of the dentition. Any impacted/embedded or ectopic teeth, which may come in the line of the osteotomy should be preferably extracted 6 months prior to surgery. These radiographs are also useful in evaluation of maxillary sinuses , temperomandibular joint. and other bony pathologies in maxillo mandibular region. Panoramic view points out to the asymmetry of the face also Submento-vertex view : This view is used to determine the buccolingual thickness of the mandible as well as degree of deformity of the face. It is also useful is assessing the condition of condyles. Hand wrist –X-rays : They are useful for growth assessment and to determine skeletal age or maturity. Orthogntahic surgeries are indicated after active growth period or after attaining skeletal maturity. e. Photographs: Preoperative photographs are necessary in order to have a record of pretreatment profile. Both the extraoral facial photographs and the intraoral photographs are taken. Frontal and lateral facial photographs are usually taken in a natural head position. Morphometric measurements can also be done on these photographs g. Evaluation of masticatory system: The temperomandibular joint is evaluated by inspection, palpation, auscultation and by radiographic examination to evaluate joint movements and an pathology. Muscles of mastication are inspected and palpated to evaluate the force of contraction and any underlying pathology.
  5. 5. Epker envelope of discrepancy ( fig 1) The maximum amount of movements possible by three different means of treatment is given by Epker envelope of discrepancies. It has three envelops. The perimeter of each envelope gives the maximum range of movements possible by different methods of treatment. Inner envelope-only orthodontic treatment Middle envelope- orthodontic and growth modification Outermost envelope—orthognathic surgery Table showing the amount of movement possible at incisor region by different methods ( anterioposterior and vertical direction). Refer figure.- Epker envelope of discrepancies -- ‘A” and “B” Amount of retraction Amount of Amount of Amount of bite possible protraction bite opening closing possible ( intrusion)poss ( extrusion)possi Maxillary Mandible Max. Mand ible ble Max Mand Max Mand Only Orthodontic Treatment 7 mm 2mm 4mm 4mm 2 mm 3 mm 2 mm 5mm Orthodontic tooth movement combined growth modification 12 mm 5 mm 5 mm 10mm 5 mm 6 mm 6 mm 5 mm Orthognathic surgery 15 mm 25 mm 10 mm 12mm 15mm 10mm 10 mm 15 mm Possibility of each type of treatment is not symmetric with respect to plane of space. For example tooth movement by orthodontic means alone is more possible anterioposteriorly than vertical direction. Growth modification is more effective in mandibular deficiency(10mm) than mandibular excess( 5mm) - ( 1) There is more potential to retract than protract the teeth
  6. 6. - (2) There is more potential for extrusion (correction of open bite) then intrusion (correction of deep bite) - (3) since growth of the maxilla cannot be modified independently of the mandible, the growth modification envelope for the two jaws is same. -- (4) surgery to move the jaws back has more potential than to advance the mandible Table showing the amount of movement possible at posterior region by different methods ( transverse and vertical direction). Refer figure.- Epker envelope of discrepancies -- ‘c” and “D” Amount of expansion Amount of Amount of Amount of possible on each side contraction intrusion extrusion possible on each possible possible Maxillary Mandible side Max Mand Max Mand Max. Mand Only Orthodontic Treatment 3 mm 2mm 4mm 3mm 3 mm 2mm 2 mm 1 mm Orthodontic tooth movement combined growth modification 4 mm 4mm 3 mm 2 mm 3 mm 6 mm 4 mm 5 mm Orthognathic surgery 7 mm 5mm 4 mm 3 mm 10mm 10mm 10 mm 10 mm
  7. 7. 2.pre orthodontic dental care Any indicated periodontal or general dental care related to maintaining teeth or improving dental health should be performed prior to orthodontics and surgical intervention. The objective is to maintain as many teeth as possible and stabilize the periodontium. Restorative work has to be completed in indicated cases. 3. Pre - surgical orthodontics The aim of the Presurgical orthodontics is to position the teeth to the most desirable position over basal bone in preparation for intended surgery. During this presurgical orthodontic phase occlusal detailing is not done. This pre surgical orthodontic fixed appliance will remain in place during surgery and provide fixation during healing. Preferabbly the fixed appliance should be edgewise or straightwire appliance. After surgical fixation is released, another shorter period (4 to 6 months) of orthodontics is indicated to detail the occlusion before retainers are fitted. The following procedures are undertaken as part of pre surgical orthodontics. 1.Tooth alignment within the arches : Spacing ,rotations and crowding are to be eliminated during the presurgical orthodontic treatment. Fixed appliances are preferred as they offer better control and it is possible to align several teeth. Space may be needed for these maneuvers which can be gained by interdental stripping or even extractions. Extractions during presurgical orthodontics is generally undertaken to relieve moderate to severe crowding within the dental arches and to accommodate segmental bone cuts. If space calculations permit to align the arch it is better to avoid extractions at this stage.Extractions can be done at the time of surgery. 2.Inter arch coordination : Any cross bites whether localized or segmental should be corrected at this phase. Crossbites with narrow maxillary arch require some form of arch expanision procedures. As a general rule orthodontic expansion or contraction to co-ordinate the upper and the lower arches should be carried out prior to the surgery so as to provide correct post- operative occlusal interdigitation. 3.Incisor inclinations and Decompensation : Most of the severe skeletal jaw discrepancies are partly compensated by change in axial inclination of the anterior teeth in opposite direction. For example in class II skeletal condtions the upper anteriors retrocline to compensate for maxillary prognathism and lower incisors procline to compensate for mandibular retrognathism. This is called as natural compensation. In mild skeletal cases this compensation is further enhanced by comouflage by selective extraction of certain teeth which is
  8. 8. described in earlier chapters. In contrast to dental camouflage, in preparation for orthognathic surgery, it is necessary to remove any dental compensations present and to place the teeth in a favorable position with their supporting bone. This is called as presurgical decompensation. This usually means that the planned movement of the teeth before surgery must be in the opposite direction from the movement with dental camouflage treatment ( fig 2) . For example in Class II skeletal malocclusions associated with mandibular retrognathism, there is natural dental compensation in the form of proclined lower anteriors to partially offset or mask the skeletal discrepancy. In such cases decompensation is typified by maxillary anterior teeth proclination and mandibular anterior teeth retroclination. In Class lll patients with prognathic mandible dental compensation is exhibited in the form of lingually tipped lower incisors and proclined upper central incisors . In such cases decompensation is typified by retroclination of maxillary anteriors and proclination of mandibular anteriors. In other words after presurgical decompensation the condition appears to be still worse. This should be explained to the patient as the condition is temporary and gets corrected after surgery. 4.The surgical treatment objective (STO) The postsurgical profile of the patient can be predicted with some degree of
  9. 9. accuracy by cephalometric means. This is called as “surgical treatment objective (STO)" or “prediction tracing". It is a two-dimensional visual projection of the changes in osseous, dental, and soft tissues as a result of orthodontics and orthognathic surgical correction of the dentofacial and occlusal deformity. The purpose of the STO is threefold: (1) establish presurgical orthodontic goals, (2) develop an accurate surgical objective that will achieve the best functional and esthetic result, and (3) create a facial profile objective which can be used as a visual aid in consultation with the patient and family members Essentially, after knowing the location and severity of deformity; the osteotomy and the extent of movement of the osteotomized segment is determined. On an acetate tracing of the cephalogram, the osteotomized segment is cut out and moved as calculated. The soft tissue follow the movement of bone in a ratio determined by the type of movement and the technique performed. These tissue changes are marked on the tracing to give the postoperative profile. However, these soft tissue changes are only meant to be a guide for prediction tracings and are variable. 5.Mock surgery : Using prediction tracings as a guide a surgical plan is formulated and then the surgery is simulated on articulated working models The models are cut and repositioned in the desirable position and the segments secured in their new position with sticky wax. The mock surgery thus helps in evaluation of treatment outcome and any possible modifications required in the surgical treatment plan are noted. The acrylic occlusal splints are constructed in new occlusal position which are of immense help post surgically. 6.Surgery and stabilization( fig 3) The next step involves the intentional or surgical fracturing and repositioning of the bony segments. Immobilization of bone fracture sites is a necessity for proper healing of the bone. The upper and lower arch are stabilized with the help of the existing fixed appliance. Intermaxillary fixation usually spans for 6-8 weeks following which the splint is removed. However with the advent of reigid immobilization fixation techniques such as screws and plates, the time period of intermaxillary fixation is greatly reduced. This helps in early mobilization of jaws. .
  10. 10. 7.Post – surgical orthodontics During this phase, the final detailing of the occlusion and esthetic root paralleling is carried out. Most cases of post-surgical orthodontics are completed by 4-6 months ------------------------------------------------------------------------------------------- Surgical methods and techniques . 1. .correction of anterior posterior discrepancies Maxillary surgeries :- ( fig 4, 5 and 6)The maxilla can be virtually moved in all the three planes by Lefort I surgery. The maxilla can be advanced by lefort I down fracture and interposing grafts in retromolar area( fig 40 The maxilla can be technically retracted backwards but is rarely done. There is anatomical skeletal restrictions for set back of whole maxilla.( fig 5) This can be overcome by anterior segmental osteotomies and retraction of the anterior segment after removal of premolar segment.( fig6)
  11. 11. Mandibular surgeries ( fig 7) :- Bilateral sagittal split osteotomy( BSSO) introduced by Trauner and Obwegeser's is still the choice for mandibular surgeries . It is used for both advancement and retraction of the mandibular ramus but it is commonly used for mandibular set backs as condylar segments are easily controlled. The BSSO is done by introral method and the two parts are immobilized by rigid immmobilisation mehods like screws,pins etc. There is early mobilization of the jaws as the period of Intermaxillary fixation (IMF) is considerably reduced. The main drawback is injury to inferior alveolar nerve. The other method used is Trans oral vertical oblique ramus osteotomy(TOVRO) which is limited to mandibular setbacks. This procedure requires less time than BSSO and less likely to produce nerve damage. The disadvantage is that
  12. 12. extended period of jaw immobilization after surgery. Another drawback is difficulty in controlling the condylar fragments . Bimaxillary dentoalveolar protrusion is treated by maxillary and mandibular anterior segmental osteotomies. 2. correction of vertical discrepancies maxillary surgeries ( fig 9 and 10) The skeletal openbites can be corrected by a LeFort I downfracture of the maxilla, with superior repositioning of the maxilla in the posterior region after removal of bone from the lateral walls of the nose, sinus, and nasal septum. The mandible autorotates and do not require separate surgeries unless there is gross anterioposterior discrepancy.( fig 9) The maxilla can be impacted in deep bite cases after performing lefort I surgery. This improves the gummy smiles in vertical maxillary excess cases ( fig)
  13. 13. Mandibular surgeries: In skeletal openbites with long faces the ramal surgeries can be done to rotate the mandible anteriorly upwards and posteriorly downwards. This lengthens the ramus and stretches the muscles associated with ptyerygomandibular sling . However this is highly unstable due to improper neuromuscular coordination of muscles . The deep bite cases are best treated by sagittal split mandibular ramus surgery to rotate the mandible slightly forward and down and the gonial angle area up. Anterior subapical surgeries can also be performed to relieve the deep bite ( Fig 10)
  14. 14. 3. correction of transverse discrepancies The maxilla can be expanded laterally or constricted with reasonable stability. The amount of constriction possible is less than the range of expansion. The only transverse movement easily achieved in the mandible is constriction, although limited expansion is possible. Maxillary surgeries . Maxillary constriction or expansion can be accomplished easily by segmenting the maxilla in the course of LeFort I downfracture Expansion is done with parasagittal osteotomies in the lateral floor of the nose or medial floor of the sinus that are connected by a transverse cut anteriorly. A midline extension runs forward between the roots of the central incisors. If constriction is desired, bone is removed at the parasagittal osteotmies. Mandibular surgeries Movements in the posterior region are limited by the condyle-glenoid fossa relationship. In the anterior region the expansion across the canine can be achieved by distraction osteogenesis. The constriction of the arches can be possible by osteotomies by removal of teeth if spacings doesnot exist.
  15. 15. . Problem / Surgical treatment Deformlty 1. Bilateral Sagittal split osteotomy ( BSSO) with Mandibular mandibular set back prognathism 2. Oblique sub condylar (sub sigmoid) osteotomy. 3. Some times reduction genioplasty is required. Mandibular 1. BSSO with mandibular advancement. retrognathism 2. Mandibular Total Subapical Advancement when change in the profile is not anticipated. 3. A forward sliding genioplasty of the chin may be required in addition Horizontal chin Genioplasty . Some times implants may be used to augment deficiency the chin appearance. Maxillary Lefort I osteotomy /Maxillary segmental (anterior) set back protrusion Maxillary retrusion Lefort I osteotomy with maxillary advancement Bimaxillary Maxillary and mandibular segmental osteotomy for set back of protrusion anterior maxilla and mandible Maxillary Lefort I osteotomy of maxilla to advance and impact maxilla deficiency and BSSO with mandibular set back mandibular excess Maxillary vertical Lefort I osteotomy with maxillary impaction excess Open bites Dento alveolar open bites Minor dento-alveolar open bites can be treated by maxillary and mandibular anterior segmental osteotomy. B. Skeletal open bite (with Angle's Class I or II) These patients usually have vertical maxillary excess. Le forte I osteotomy with maxillary impaction is done C. Skeletal open bite (with Angle's Class III) . They have increased length of ramus and mandibular body. Sagittal split osteotomy is done to displace mandibular body upwards and backwards
  16. 16. If there is an associated maxillary retrognathism a Le forte I with maxillary advancement is done In case the patient also exhibits a vertical maxillary excess, then Ie Forte I with maxillary impaction is done . Deep bite Lower anterior dento-alveolar segmental osteo~omy to bring the lower incisor segment downwards and forwards Maxillary Usually these are associated with vertical and sagittal constriction/expan problems. sion Lefort I with parasagittal osteomies is done for expansion and contraction Mandibular Anterior body osteotomies constriction Mandibular Distraction osteogenesis. expansion Genioplasty Techniques. The chin can be augmented either by using an osteotomy of the lower border of the mandible to reposition the symphysis or by adding an implant material. The ostetomies are preferred approaches. A wedge shaped portion of the symphysis and inferior border are segmented by osteotomy. This segment can be advanced to augment chin contour. This is called as advancing genioplasty and is used in cases with deficiency of chin. A wedge of bone can be removed above When reduction is desired. This is called as reduction genioplasty and is used in cases with prominent chins. It can be down grafted to increase lower face height. The distal aspects of the wedge can be flared or compressed if narrowing of the anterior portion is needed. It can also be shifted sideways to correct asymmetry,. Thus the chin can be controlled in all the three planes by this plastic surgery.
  17. 17. Silicone implants can be used to augment the chin. The main drawback is the problems with bone resorption under the silicone material and migration of the implant . porous hydroxylapatite in block form can also be used but it is difficult to adapt at the time of surgery and is not immune to the problems of resorption and migration. Osteodistraction Osteodistraction is a technique of bone lengthening that uses the body's natural healing mechanisms to generate new bone. An osteotomy (corticotomy) is made in an area of bone deficiency, and an external fixator is used to slowly elongate the bone to its new dimension while natural ossification produces new bone at the site of distractions. Although osteodistraction was pioneered by surgeons in the 1880s, Codivilla of Bologna, Italy, produced the first published accounts in 1905 . In 1949 Dr. Gavriel O. Ilizarov began to develop new ways of applying the principle of osteodistraction. . Ilizarov's principles. Surgeons who have used or modified the distraction procedure have relied on Ilizarov's basic principles, which can be expressed as the law of tension stress. These principles include the following  Latency period The latency period is the time interval between the surgical procedure and the initiation of application distraction forces.; Ilizarov recommended a delay of 5 to 7 days
  18. 18.  Rate of distraction Achieving the correct rate of distraction is important for proper activity of cells and bone formation. The optimal rate currently is considered to be 1 mm per day  Rhythm of distraction The term rhythm of distraction refers to the number of distraction events per day.For example,a 1 mm a day rate could be divided into a rhythm of 0.5mm twice a day or 0.25 mm four times a day. In 1994 Aronsons found that either of those two rates is clinically acceptable,but a continuous distraction force is ideal  Frame stabilityThe capacity of the fixator to stabilize the newly formed bone within the area of distraction isknown as the frame stability. Aronson found that the fixation must be stable enough to support the newly formed microcolumns of bone. Application of distraction osteognesis in craniofacial complex. Current developments and refinements in the design of intraoral distraction devices have allowed orthodontists to treat patients with a variety of anteroposterior and transverse problems that previously were difficult to manage other than through major surgery
  19. 19. Intraoral corticotomies performed in conjunction with skeletal toothborne distraction appear to offer significant advantages over classical treatment of micrognathia in Class Il mandibular deficiency patients and thus can be used to lengthen the mandibles.( fig 12). It is also useful in widening of the mandible along with the lengthening procedures Another application is in the increase in the transverse diameter of maxilla ie.., arch expansion. It can also be used in cases of maxillary deficiencies for lengthening procedures. The principles of osteodistraction appear to open the door for the new millennium to a more conservative form of treatment for some of the skeletal jaw imbalances prevalent in modern orthodontic practice. COSMETIC SURGERIES They are surgical procedures carried out to improve the esthetic appearance of the patient. These surgeries can involve the nose and the chin. Cosmetic surgery of the nose is called rhinoplasty. They are undertaken to correct abnormal configuration of the nose. Cosmetic surgery of the chin is referred to as genioplasty.
  20. 20. Essay type questions 1. Describe the different orthognathic surgeries for class II skeletal condi tions Short answer questions 1) Bilateral sagittal split osteotomy ( BSSO) 2) Genioplasty 3) Osteigenesis distraction 4) Mandibular surgeries 5) Lefort I surgeries. 6) preSurgical orthodontics 7) decompensation.