Prosthodontic Management of Mandibular Defects


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Prosthodontic Management of Mandibular Defects

  1. 1. Prosthodontic management of Mandibular Defects
  2. 2. Contents • Introduction • Challenge • Classification of mandibular defects • Complications • Factors affecting treatment of mandibulectomy patients • Relating surgical and prosthetic considerations in mandibulectomy patients • Treatment plan • Management of mandibular deviation • Implant supported prosthesis • Conclusion • References
  3. 3. Introduction
  4. 4. • Mandible is a single bone that creates • Peripheral boundaries of the floor of mouth • Facial form (Lower third of face) • Speech • Swallowing • Mastication • Respiration • Disruption of the mandible has the potential to disrupt any of these
  5. 5. Rehabilitation of mandibulectomy patients should therefore consider both form and function . Thomas Taylor
  6. 6. Surgical resection of tumor often includes a partial mandibular resection, a partial glossectomy, a partial resection of the floor of the mouth, and a radical neck dissection. The extent of surgery and the effects of radiation therapy and chemotherapy determine the amount of rehabilitation needed by a given patient.
  7. 7. Oral reconstruction of the patient who has a partially resected mandible is one the most challenging procedures confronting the maxillofacial
  8. 8. Classification of mandibular defects
  9. 9. Mandibular Defects Developmental Acquired (Mandibular prognathism/ Pathology Trauma retrognathism) (tumors) (Fractures) Surgical Mandibulectomy Gunning splints
  10. 10. Acc to etiology - Laney(1979) 1. Acquired: - Marginal - Segmental a) Anterior body b) Lateral to midline - Body only - Ramus - Body with disarticulation
  11. 11. 2. Congenital - Incomplete formation - Incomplete ossification e.g.) hypoplasia, mandibulofacial dysostosis,etc 3. Developmental as a result of postnatal insults e.g.) trauma during birth, surgery, etc
  12. 12. Acc to amount of resection - Laney• Continuity defect (marginal resection) - Inferior border and its continuity preserved - No deviation - Less facial disfigurement - Occlusion rarely changed - Can be :- anterior defect posterior defect • Discontinuity defect (segmental resection) - Complete segment of mandible from alveolar crest to inferior border removed - Mandible deviates to resected side - Marked facial disfigurement - Occlusion altered - Can be :- lateral discontinuity defect midline discontinuity
  13. 13. Acc to Cantor and Curtis (1971) Class 1 Radical alveolectomy with preservation of mandibular continuity
  14. 14. TISSUES RESECTED - Portion of alveolar process and body of mandible - Lingual and buccal sulcus mucosa - Portion of base of tongue and mylohyoid muscle - Lingual and inferior alveolar nerves - Sublingual and Sub maxillary salivary glands - Sometimes anterior part of digastric muscle FEATURES 1. Least debilitating. 2. Can raise the floor of the mouth causing reduction in tongue mobility. 3. Ability to shape and control the tongue may be lost due to loss of some intrinsic muscles.
  15. 15. Class 2 : Lateral resection of mandible distal to cuspid
  16. 16. TISSUE RESECTED - condyle, ramus and body of mandible distal to cuspid - mylohyoid, hypoglossal,ant belly of digastric, internal pterygoid,masseter,external pterygoid, pharangoglossal & palatoglossal muscles, most of intrinsic muscles of tongue. - hypoglossal , lingual and inferior alv nerves - adjacent buccal and lingual mucosa FEATURES 1 Speech, swallowing, saliva control, manipulation of food impaired. 2. Facial disfigurement apparent 3. Disarticulation and loss of muscles of mastication will hampered mandibular movements 4. Taste ,sensory and motor losses more extensive as compared to class 1
  17. 17. Class 3 Lateral resection of the mandible to midline
  18. 18. TISSUE RESECTED all those described in class 2 in addition to the anterior portion of the mandible, geniohyoid, genioglossus, remaining portion of mylohyoid muscle with lingual and buccal mucosa. FEATURES 1. Restricted tongue mobility due to loss of tip of tongue and genioglossus muscle 2. Speech, swallowing,saliva control and manipulation of food severely restricted. 3. Facial disfigurement is worse due to loss of anterior part of mandible 4. Disarticulation and reduction in amount of basal bone reduce prosthodontic prognosis.
  19. 19. Class 4 Lateral bone graft & surgical reconstruction
  20. 20. • Lateral bone and split thickness skin or pedicle graft can be performed on patients who have had: - radical alveolectomies - resection of mandible distal to cuspid with or without disarticulation. • Three types of bone grafts are possible 1. Mandibular augmentation procedures. 2. Bone graft that connect a residual condyle with the larger mandibular fragment.
  21. 21. Class 5 Anterior bone graft &surgical reconstruction
  22. 22. TISSUE RESECTED - anterior portion of the mandible - large bilateral portions of mylohyoid, geniohyoid genioglossus and anterior digastric muscles - bilateral lingual and inferior alv nerves - bilateral submaxillary and sublingual salivary glands - mucosa of lower lip - anterior floor of mouth - ventral surface of tongue The mucosa retained in the labial and buccal regions is sutured to the residual stump of the tongue and a krischner wire is often positioned to maintain the mandibular fragments .
  23. 23. Class 6 It is similar to a class V patient, but the continuity of the mandible has not been restored surgically. Because each lateral fragment moves independently, the prognosis for a removable prosthesis is poor and fabrication is not recommended
  24. 24. Complicatio ns
  25. 25. With only one half or two thirds of the mandible remaining, stability, support and retention of the mandibular denture are compromised. Due to radiation therapy either prior to or after surgery, the oral mucosa is atrophic and fragile, predisposing to soft tissue irritation and ulceration. The reduction in saliva output, and the thick mucinous nature of the saliva that remains after therapeutic levels radiation, impairs retention and
  26. 26. The angular pathway of mandibular closure induces lateral forces upon the dentures, which dislodge them. The deviation of the mandible creates abnormal jaw relationships. The abnormal profile and position of the mandible in relation to the maxilla may prevent ideal placement of the denture teeth over their supporting structures. The impairment of motor and/or sensory control of the tongue, lip, and cheek impairs the ability of the
  27. 27. Factors affecting treatment of mandibulectomy patients
  28. 28. Location & Extent of Mandibular Defect Marginal alveolectomy -Least debilitating -Main problems – loss of vertical ridge height and vestibular depth -Vertical discrepancy is most important when prosthesis supported by dental implants is considered.
  29. 29. Marginal defects have better prognosis than discontinuity defects. The farther anterior the defect, the more disfiguring and functionally debilitating it is likely to be. Reason: Loss of key muscle attachments(genioglossus and geniohyoid) located in anterior mandible that control tongue function and mobility.
  30. 30. • Defects of the symphyseal region are most debilitating and difficult to treat. • Greatest facial disfigurement. • Surgical reconstruction necessary or at least segmental stabilization before prosthodontic treatment can be initiated.
  31. 31. Mandibulectomy defects in the molar region -well suited for surgical reconstruction compared to anterior defects. -If muscle attachments are intact – Good prognosis -Near normal appearance and function is achievable.
  32. 32. 2. Presence of remaining natural teeth/pre-existing implants Patients after mandibulectomy present with few or no remaining natural teeth. -Pts with greatest risk of sq cell carcinoma are heavy users of tobacco and alcohol and lack good oral hygiene. -Strong relationship between tobacco & periodontal disease -Teeth are usually extracted prior to radiotherapy to prevent complications such as osteoradionecrosis. Greater the number of teeth ,better the prognosis.
  33. 33. Remaining natural teeth in linear relationship are unlikely to provide adequate abutments for prosthesis than teeth arranged in two dimensions
  34. 34. A maxillary complete denture will function well for a mandibulectomy patient against a reconstructed mandibular dentitionExceptions Collapse of residual proximal mandibular stump against the posterior maxillary alveolus prohibiting adequate denture flange extension. When a guide flange prosthesis is planned for treatment of mandibular deviation . Pressure from Guide flange can dislodge the
  35. 35. 3.Degree of post mandibulectomy rotation and deviation Mandible deviates towards the defect and rotation of mandibular occlusal plane inferiorly.
  36. 36. • During mandibular closure, mandible rotates around occlusal contacts on un-resected side, and remaining teeth on resected side drop further out of occlusion. This movement is called FRONTAL PLANE ROTATION.
  37. 37. • Deviation: Due to • Primarily due to loss of tissue involved in surgical resection. Rotation: Due to - Pull of the suprahyoid muscles on the residual fragment causing inferior displacement and rotation around the fulcrum of the remaining condyle. - Gravity. Loss of anchorage of elevator muscles. Sequelae • Facial disfigurement • Loss of occlusal contact
  38. 38. • Prosthodontic prognosis in such patients can be improved by early post resection physical therapy to reposition the mandibular fragment to a more normal position and to minimize scar formation that will make deviation more severe. • Should be carried out as early as possible. • After 6-8 weeks post operatively it will not be as beneficial. • Can be in the form of 1.Physical therapy carried out by the patient himself
  39. 39. 5.Available mouth opening Trismus –due to surgical trauma Physical therapy should be started immediately. Scar tissue formation will further reduce mouth opening. Simple test to check mouth opening: Insert a stock mandibular impression tray in the mouth.If this cannot
  40. 40. 6.Functional limitation of tongue - Frequently the surgical wound is closed by suturing the remaining tissues of the floor of the mouth or tongue to the remaining buccal tissues.
  41. 41. This compromises: - Speech - Swallowing - Mastication - Control of food bolus - Ability to control removable prosthesis - Lingual vestibuloplasty and skin or mucosal grafting can be used to improve tongue mobility Evaluation of tongue mobility - In patients whom anterior resection has been done, ability to lick the lips when the artificial prosthesis
  42. 42. In such cases consideration is given to lowering the anterior occlusal plane or arranging the teeth slightly lingually. • Speech therapy • Loss of innervation will compromise tongue function and prognosis of prosthodontic rehabilitation. If lingual nerve is sacrificed during resection, the tongue on the defect side will permanently remain without any feeling. Loss of sensory capability:- Affects speech Mastication Prosthesis control Loss of sensory innervation of the buccal mucosa(long
  43. 43. 7.Compromise of vestibular extensions  Vestibular depth is critical for stability and peripheral seal It is also critical when mandibular continuity is restored with bone grafting and implants are considered.
  44. 44. 8.Skin grafting • Skin grafts are used for surgical reconstruction either as lining for the surface of resected soft tissue or as part of skin and connective tissue grafts such as pedicle flaps, free flaps etc. Advantages 1. Effective load bearing tissue. 2. Can withstand pressure and chafing from prosthesis. 3. Protects underlying bone and connective tissue well due to rapid turnover of keratin producing cells. Disadvantages 1. No sensory innervations.
  45. 45. 9.Radiation therapy • Careful treatment planning is required for patients with radiation therapy • Irradiated tissue is fragile ,sensitive to manipulation, dessicated,slow to heal, prone to infection and at risk of osteoradionecrosis
  46. 46. 10. Altered anatomic relationships following restoration of mandibular continuity  Reconstruction of anterior defects Most difficult situation for grafting and frequently results in a graft that is deficient anteriorly. - Results in a severe Class 2 like situation. The prosthodontic difficulties seen in rehabilitating such a patient are:- - Inability to provide proper lip support. - Speech problems associated with mandibular dentition placed too far lingually. - Inability to control food bolus due to lack of motor
  47. 47. - Excessive display of mandibular teeth due to patients inability to maintain normal lip posture. - Difficulty gaining adequate space for prosthesis placement without encroaching on function of tongue. - Misalignment of remaining un resected mandibular fragments and resultant relationship between maxillary and mandibular teeth.  Reconstruction of posterior defects - More predictable from prosthodontic point of view as compared to anterior defects. - The mediolateral positon of the graft is frequently seen
  48. 48. 11. Previous experience with removable prosthesis Indicator of how successful rehabilitation will be, particularly edentulous patients
  49. 49. Relating surgical considerations to prosthodontic treatment Marginal mandibulectomy Soft tissues are mainly used to reconstruct marginal mandibulectomies They may be: - Skin graft - Local flap - Pedicle flap - Micro vascular free flaps (MVFF) Skin grafts are ideal for prosthetic reconstruction. However when soft tissue bulk is required or recipient bed is previously irradiated micro vascular free flaps are
  50. 50. Discontinuity defects Previously soft tissue local flaps(mainly the residual tongue sutured to the border of the defect) and pedicle flaps (pectoralis muscle) were used. MVFF have revolutionized the treatment of discontinuity defects. Micro vascularized bone is mainly obtained from: 1.Fibula- most common 2.Iliac crest Soft tissue MVFF are obtained from 1.Forearm 2.Rectus muscle
  51. 51. Mandibular mal position after bony reconstructionMay be due to: 1. Minimal proximal mandible on the surgical side to attach the bone graft. 2. Mandibular segments are not stabilized and maintained in their pre-operative relation to each other during grafting procedures. 3. Delayed reconstruction may not be able to overcome scar tissue formation completely. 4. The bone grafts used i.e the fibula and the iliac crest graft have some inherent problem. (Lacks height compared to the residual mandible)
  53. 53. All basic principles of complete denture construction must be considered and modified because of the unusual anatomic and functional situation.
  54. 54. TREATMENT PLAN  Exercise regimen  Reconstruction  Definitive Guidance Prosthesis.
  55. 55. Treatment options • Conventional complete denture • Cast partial denture /sectional denture prosthesis. • Implant retained and supported overlay denture
  56. 56. Impressions Maximum extension and tissue coverage should be recorded with the preliminary impression Irreversible hydrocolloid is used with an altered/sectional stock tray. Conventional border molding and Master impression is used to achieve better peripheral seal.
  57. 57. Primary impression
  58. 58. Shifman and Lepley(1982) Neutral zone or denture space concept for marginal mandibulectomy patients. They supported this by quoting Fish(1933) and Brill(1965)
  59. 59. Secondary impression with border molding
  60. 60. Processed bases • Necessary due to loss of supporting bone ,unusual intra-oral contours, gross mal position of occlusal contacts. • Allow the determination of the relationship of the final prosthesis periphery and the buccal or lingual tooth position. • Recording maxillo-mandibular relationship with processed bases allow the clinician to evaluate retention and stability proir to adding wax rims or dentition.
  61. 61. • Significant loss of alveolar bone as well as rotation and deviation of the mandible postoperatively make it necessary for the record bases to be as stable as possible during maxillo mandibular records. • Extension beyond the periphery of the prosthesis may be required to support the lip. To add stability to the prosthesis, occlusal contact may need to be significantly buccal or lingual to normal anatomic landmarks that usually denote the occlusal table. • Pts who have implant retained prosthesis should have retentive elements incorporated in the processed
  62. 62. Jaw relation • Centric relation does not exist in partially mandibulectomy patients with discontinuity defects because there is only one condyle to guide the mandible. • Interestingly they do have proprioception for a repeatable area but not a repeatable point contact when asked to open wide and close the
  63. 63. Record bases are constructed in the usual way with the following exceptions: In the maxilla, the wax rim used to record the centric occlusion registration record is widened on the un resected side towards the palatal side in order to account for deviation of the mandible.
  64. 64. • Vertical dimension of occlusion is difficult to determine due to mandibular deviation and impaired motor and sensory function. Traditional methods are contraindicated hence VDO is recorded with mandible closing as much as possible. VDO determination should rely on lip competence, facial appearance
  65. 65. Centric occlusion registration is done with wax, plaster or any other recording media. The patient is instructed to move the mandible as far as possible toward the untreated side. Then patient was asked to close with his own muscular force when the mandible was manually guided. This records a functional maxillo mandibular relationship which the patient can attain.
  66. 66. Teeth selection and arrangement• Artificial denture teeth of zero degree cuspal angulations are selected and arranged to achieve monoplane occlusion and to allow for lateral freedom of mandibular movements. • With the lingual inclination of the residual mandible, and with elevation of the buccal shelf, placement of posterior teeth to the buccal of the residual alveolar ridge centers the forces of occlusion more favorably
  67. 67. • After all the mandibular teeth and the maxillary teeth have been arranged, ramps are developed for the maxillary prosthesis in base plate wax. These ramps usually 5-10mm wide and should provide 2-4mm horizontal overlap with the mandibular posterior teeth. • Depending upon severity of deviation, the ramp on the nonsurgical side usually extends palatal to the maxillary alveolar ridge, and the ramp on the surgical side extends
  68. 68. Palatal Augmentation Prosthesis • These patients have difficulty in valving the tongue against the palate for appropriate speech sounds and to manipulate food bolus in mastication and swallowing. • This is due to loss of tissue bulk and motor movement of the tongue.
  69. 69. • This prostheses involves shaping the contours of a palatal base plate, either retained by maxillary dentition or maxillary complete denture. • In normal tongue-palate relationship, the palate CUPS around the tongue at rest and in function.
  70. 70. • Hence contours of palatal augmentation prostheses should also CUP around the residual/deviated tongue. • Repeated movements of tongue will allow the clinician to add wax to the base plate to establish occlusal contact. • Thickness is increased until the tongue contacts the palate in swallowing.
  71. 71. Cast partial denture • Indicated for patients with marginal mandibulectomies • Ideal prosthesis bearing surface is split thickness graft ; it is thin, firmly attached to the mandible and will not move with movement of tongue , floor of mouth or cheek
  72. 72. Pick up impression or functional reline is needed Removable framework should follow routine parameters of design related to support, stability and retention.
  73. 73. Marginal mandibulectomy patient resurfaced with skin graft
  74. 74. Fabrication of framework
  75. 75. Sectional Denture • Two part denture designed to engage and utilize opposing proximal undercuts on mesial and distal abutment teeth, which will result in positive retention in both vertical and lateral direction often without incorporating a conventional clasp. • Each part of the denture will therefore have its individual path of insertion and once in position the part will be maintained in position by means of a locking bolt to form a whole unit. • The technical construction of such an
  76. 76. Management of mandibular
  77. 77. Methods to minimize deviation • Use of skin grafts and flaps for wound closure • Inter maxillary fixation at time of surgery • Intense physiotherapy to minimize deviation
  78. 78. IMF • Aramany and Myers advocated the use of inter maxillary fixation with arch bars and elastics for 5-7 weeks immediately after surgery. • This type of fixation maintains the residual mandible in the proper maxillo mandibular position and permits healing of the defect and the associated scar formation with the teeth in occlusion.
  79. 79. • If Inter maxillary fixation is used in immediate post- operative period, very little muscle retraining may be needed. • The degree of deviation seems to be inversely proportional to the length of time the
  80. 80. Gunning splints can be used for IMF in edentulous patients.
  81. 81. VACCUM FORMED PVC SPLINTS • Following the removal of inter maxillary fixation, early progression to a more definitive appliance can be facilitated by using an intermediate Vacuum formed PVC appliance. • Upper & Lower splints are fused together in maximum inter cuspation by interposing a further layer of the heated polymer.
  82. 82. • Jaw movements are thus gently restrained and guided by the soft plastic splint making it comfortable for the patient to wear. • The appliance may also be worn at night-time • This appliance has a relatively short shelf life and needs to be replaced by a more definitive acrylic or metal appliance once the patient adapts to
  83. 83. On closure of jaws the lower teeth and mandible are readily and easily guided into the lower half of the splint by its flanges and indentations into the correct
  84. 84. MANDIBULAR GUIDANCE PROSTHESIS In discontinuity defects mandibular guidance therapy can be instituted to retrain the patient’s neuromuscular system to provide an acceptable maxillo-mandibular relationship of the residual portion of the mandible which permits occlusion of the remaining natural teeth
  85. 85. Classification 1) Palatal based guidance prosthesis • Maxillary inclined plane prosthesis. • Positioning prosthesis with palatal flange • Widened maxillary occlusal table 2) Mandibular based guidance prosthesis
  86. 86. Maxillary inclined plane prosthesis.• The prosthesis is retained using inter proximal ball clasps or adam’s clasps. • Mandibular closure results in the progressive sliding of the remaining mandibular teeth up the incline in a superior and lateral direction until the occlusal contact is reached.
  87. 87. Positioning prosthesis with palatal flange • Patients who are able to use their pre surgical inter cuspal position after mandibular resection often complain of inability to prevent the mandible from deviating towards the defect side during sleep. • On awakening they have difficulty reestablishing normal occlusal contact.
  88. 88. • Flage extending from palate inferiorly into the lingual vestibule between lateral border of tongue & lingual surface of the mandible can be formed in the mouth with auto polymerizing acrylic resin. • Prevent medial deviation of un resected mandible even when the mouth is open. • The flange should contact only the lingual surfaces of mandibular teeth and it should not impinge on the lingual mucosa of the mandible throughout the opening and closing
  89. 89. Widened maxillary occlusal table • Patients who cannot attain the ideal medio lateral position of the remaining segment and an acceptable occlusal contact of the teeth, in spite of the use of various guidance prostheses, a palatal ramp or a widened maxillary occlusal table using double row of teeth may be used. • Provide a surface against which the
  90. 90. Palatal Ramp to widen maxillary occlusal table
  91. 91. Twin occlusion to widen maxillary occlusal table
  92. 92. Mandibular lateral guide flange prosthesis • Used in patients who can achieve proper medio lateral position of the mandible but cannot hold that position for adequate mastication.
  93. 93. • The guide flange is attached to a cast mandibular removable partial denture. • It can be either molded in wax at the try-in stage and processed in clear acrylic resin or a heavy wire loop may be used. • The guide flange is extended into maxillary muco-buccal fold superiorly & diagonally on non defect side without
  94. 94. Implant supported prosthesis
  95. 95. Advantages of reconstruction using osseo integrated implants • They provide stability and retention for the prosthesis. • They allow the use of a fixed or removable prosthesis. • It avoids the preparation of remaining teeth as abutments. • It avoids the problems of the tissue borne prosthesis.
  96. 96. • For many resection patients, usually 2 -3 properly positioned implants are needed. • Implants should not be placed close to the border of the resected mandible because the bone in this region may be necrotic or poorly vascularized, secondary to the previous surgical procedure.
  97. 97. Implants placed in the fibular graft 6 months after reconstruction
  98. 98. Unilateral partial denture retained by ball attachments on the implants and one clasp on the remaining dentition
  99. 99. Final prosthesis
  100. 100. Conclusion
  101. 101. • Prosthodontic success in the mandibular resection patient is closely allied with the surgical reconstruction. • MVFFs has revolutionized reconstruction of the mandible and contiguous oral structures.
  102. 102. • Prosthodontic modifications to routine prosthodontic procedures are necessary to compensate for deficits that are not correctable with surgical reconstruction • The maintenance of facial form, prevention of tethering of intraoral tissues have greatly enhanced the results obtained by prosthodontic
  103. 103. References• Ackerman AJ The prosthodontic management of oral and facial defects J Prosthet Dent,1955;5:413-432 • Scannel JB Practical considerations in dental treatment of patients with head and neck cancer J Prosthet Dent,1965;15:764-778 • Kelly EK Partial denture design applicable to the maxillofacial patient J Prosthet Dent,1965;15:168-173 • Swoope CC Prosthetic management of resected edentulous mandibles J Prosthet Dent,1969;21:197-201 • Cantor R and Curtis TA Prosthetic management of edentulous mandibulectomy patients Part 1 J Prosthet Dent,1971;25:447- 455, Part 2 J Prosthet Dent,1971;25:547-555, Part 3 J Prosthet Dent,1971;25:671-78.
  104. 104. • Armany MA and Meyers EN Intermaxillary fixation following mandibular resection J Prosthet Dent,1977;37:437-443 • Desjardins RP Occlusal considerations in partial mandibulectomy patients J Prosthet Dent,1979;41:308-311 • Shifman A and Lepley JB Prosthodontic management of postsurgical soft tissue deformities associated with marginal mandibulectomies J Prosthet Dent,1982;48:178-183 • Clinical maxillofacial prosthetics, Thomas D Taylor;1st edition • Maxillofacial prosthetics, Varoujan A Chalian • Maxillofacial prosthetics, postgraduate dental hand book series,Vol 4 William R Laney • Removable partial prosthodontics,Alan B Carr;11th edition • Clinical removable partial prosthodontics,Kenneth L Stewart;2nd