Impacted teeth

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Oral & Maxillofacial Surgery
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Impacted teeth

  1. 1. Impacted Wisdom Teeth Dr. Hesham Marei MSc, PhD, MFDS (Eng) Assistant Professor of oral and Maxillofacial Surgery King Faisal University
  2. 2. Outline •Definitions •Incidence •Classification of impaction •Imaging, evaluation and assessment •Indications/ contraindications for removal •Benefits Vs risks of prophylactic removal of impacted 3rd molars •Complications •Conclusion
  3. 3. Definition An impacted tooth is one that has failed to fully erupt into the oral cavity within its expected developmental time period and can no longer be expected to do so.
  4. 4. Theories of Impaction Smaller jaws/fast growth Diet changes Mechanical obstacles Vestigial theory
  5. 5. Commonest affected teeth • mandibular third molars • maxillary canines • mandibular premolars/canines • maxillary incisors • maxillary third molars • 95% of all teeth that will erupt are erupted by age 24. • 75% of mandibular third molars are impacted
  6. 6. Classification Systems  Angulations  Vertical  Distoangular  Mesioangular  Horizontal  Buccal/Lingual  Relationship to anterior border of ramus  Depth of impaction  Nature of overlying tissue
  7. 7. VERTICAL HORIZONTAL MESIOANGULAR DISTOANGULAR According to the long axis of the neighbouring mesial tooth
  8. 8. Angulations of embedded 3rd molars Maxilla % Mandible% Vertical 68.3 38.7 Mesio-angular 13.3 44.0 Desto-angular 17 8.5 Meso-horizantal 0.19 7.7 Desto-horizantal 0.66 0 Bucco-lingual 0.37 0.92 Inverted 0.04 0.02
  9. 9. Relationship to Anterior Border of Ramus (Pell and Gregory)  Class I - adequate room to erupt  Class II - one half covered  Class III- completely embedded
  10. 10. Pell and Gregory Classification (relation to the ramus)
  11. 11. Imaging, Evaluation and Assessment
  12. 12. Radiographic Assessment • Minimum of an OPG • Visualize all the teeth and adjacent structures including bone, morphology and number of roots, hypercementosis • Depth of bone around tooth • Follicular pathology
  13. 13. Other Important Factors  Size of Follicular Sac  Density of Surrounding Bone  Contact with Mandibular Second Molar  Relationship to Inferior Alveolar Nerve
  14. 14. Other Important Factors
  15. 15. 8 Relation to IACRelation to IAC
  16. 16. Darkening of the root.Darkening of the root. Deflection of the root.Deflection of the root. Narrowing of the root.Narrowing of the root. Dark and bifid root apex.Dark and bifid root apex. Interruption of the whiteInterruption of the white line of the canal.line of the canal. Diversion of the canal.Diversion of the canal. Narrowing of the canal.Narrowing of the canal.
  17. 17. Indications & Contraindications
  18. 18. Problem #1 – Soft Tissue  Even with adequate arch length and full eruption, 3rd molars are often surrounded by thin, unkeratinized, highly distensible lining mucosa of the buccal vestibule.  Encourages pathogenic bacteria retention  Poorly withstands hygiene measures
  19. 19. Problem #2 – Periodontal Compromise  Bone loss distal to the 2rd molar after removal of the 3rd molar is controversial, at best. Even with some loss of bone, the result is stable and cleansable – the goal of periodontal therapy.
  20. 20. Measuring Bone Height
  21. 21. Problem #3 – 3rd Molar Caries
  22. 22. Problem #3 – 3rd Molar Caries
  23. 23. Problem #4 – 2nd Molar Caries
  24. 24. Problem #5 - Infection  Can turn an elective procedure into an urgent or emergent situation  Unscheduled loss of work  Increased pain and healing time  Compromise of adjacent teeth  Compromise of patient’s systemic health
  25. 25. Types of Infection 1. Simple dental caries and periodontal disease 2. Pericoronitis 3. Abscess 4. Cellulitis 5. Abscess extension into adjacent fascial spaces 5. Abscess spread to distant sites 6. Recurrent infections 7. Infections resistant to initial local and systemic treatment measures
  26. 26. Infection
  27. 27. Pericoronitis The most common cause of therapeutic 3rd molar removal.
  28. 28. Pericoronitis  Inflammation of the tissues around the crown of any partially erupted/ impacted tooth.  It is either acute or chronic
  29. 29. Pericoronitis  A failure of preventive measures  A failure of early recognition, or a failure to seek proper treatment  A step along the pathway of infection  Pericoronitis should be a warning sign that initiates immediate and aggressive treatment with careful observation.
  30. 30. Pericoronitis  Features of pericoronitis  Trismus, pain, dysphagia, malaise, bad taste  Signs of inflammation of the pericoronal tissues, with frank pus from under the operculum  Cheek biting and cuspal indentations on the operculum  Halitosis, food packing  Can progress with systemic symptoms and spread to adjacent tissue spaces
  31. 31. Pericoronitis • Treatment for pericoronitis • Local measures  Irrigation, oral hygiene measures  Remove trauma, i.e. Extract upper 8, consider lower 8 later • General measures  Soft diet, analgesics, antibiotics, admission in some cases
  32. 32. Problem #6 - Resorption
  33. 33. Problem #7 - Supereruption
  34. 34. Problem #8 - Cysts Dentigerous Cyst
  35. 35. Dentigerous Cyst
  36. 36. Dentigerous Cyst Supernumerary 4th Molar
  37. 37. Types of Cysts  Follicular cyst (Dentigerous Cyst)  OKC (Odontogenic Keratocyst)  Ameloblastoma (several varieties)  Not all radiolucencies are cysts! - Lymphoma - Myeloma - Metastatic carcinoma
  38. 38. Without the radiolucency, would you have recommended removal? Is the removal of this better or worse with the radiolucency?
  39. 39. When would you recommend removal of this 3rd molar?
  40. 40. Cysts – A Few Facts  May be prevented by early removal – when normal dental follicle is still evident.  The pericoronal pocket, or residual follicle, is responsible for most cystic pathology.  All cystic tissues should be removed and biopsied.
  41. 41. Cysts  Cysts themselves are not catastrophic – the problem is that we don’t know exactly what they are until they are histopathologically examined – which necessitates removal.  All cysts result in bone loss.  Some cysts recur more than others.
  42. 42. Problem #9 - Tumors  Benign vs. malignant  Odontogenic vs. non-odontogenic  Each of these factors has important treatment implications.
  43. 43. Tumors
  44. 44. Problem #10 – Risk of Fracture
  45. 45. Immediate Pre-extraction
  46. 46. Immediate Post-extraction
  47. 47. 3 Days Post-extraction
  48. 48. 8 Days Post-extraction
  49. 49. Problem #11 - Fracture
  50. 50. Problem #12 - Orthodontics  Prevent loss of post- retention stability  Allow distalization of 2nd molars  These are controversial indications
  51. 51. Possible Contraindications to Removal of Impacted Teeth • Extremes of age • Compromised medical status • Probable excessive damage to adjacent structures • Asymptomatic teeth
  52. 52. Factors that Contribute to Risk Assessment for Patients  Age  Location of IAN  Body mass index  Drug history  Systemic conditions  Surgical access space  Tongue size  Anesthesia history  Maxillary sinus location  Root contour  Third molar position  Interincisal opening  Health of second molar  Bone mass and density
  53. 53. Factors that makes surgery Less difficult  Mesio-angular position  Class I ramus  Position A depth  Roots ½ to 2/3 formed  Fused conical roots  Wide periodontal ligament  Large follicle  Elastic bone  Separated from 2nd molar  Separated from inferior alveolar nerve More difficult  Disto-angular position  Class III ramus  Position C depth  Long, thin roots  Divergent curved roots  Narrow periodontal ligament  Thin follicle  Dense, inelastic bone  Contact with 2nd molar  Close to inferior alveolar nerve  Complete bone impaction
  54. 54. Presurgical Patient Counseling • Decision on method of anaesthesia [LA,+/- IV sedation, GA] • Preoperative warnings of pain, swelling, bruising, possible hypoesthesia of lip/ tongue ,trismus, diet advice, • Verbal and written warnings (information sheet), enter into notes, nursing staff as witness • Warn patient of post operative complications with a greater than 5% incidence and permanent complications even if less than 1% • If patient declines treatment need to be informed of likely long term problems
  55. 55. conclusion • Emerge between 18-24 yrs in 95% of the population. • Fail to develop in 1:4 adults • 72% mandibular molars impacted • Decision to remove based on balance of risks/benefits of retention observation against risks/benefits of removal.
  56. 56. conclusion • Adequate patient assessment ensuring good case selection • More conservative approach • Essential to give explanation of procedure with its associated potential complications and alternatives reinforced with information leaflet • Details noted for medicolegal reasons
  57. 57. conclusion The third molar controversy is still going-on. As with all surgical procedures, the surgeon wants to do surgery, it is his or her profession! From a patient point of view, non-surgical treatment should be the first option in an asymptomatic environment.
  58. 58. Management of impacted third molars RemovalRemoval Risks •Crowding of dentition. • Resorption of adjacent tooth and periodontal status. • Development of infection, cyst and tumor RetentionRetention Benefits •Preservation of functional teeth. •Preservation of residual ridge Risks Minor Complications: •Alveolitis •Paresthesia •Trismus •Fractures •Hemorrhage Major Complications: Dysesthesia Bacteremia Benefits •Decreased morbidity in younger patients •Therapeutic control
  59. 59. The Procedure
  60. 60. Anatomy
  61. 61.  ≈ 7.8mm at the 3rd molar  ≈ 10mm Between the first and second molar
  62. 62. Canal diameter ≈ 2 mm
  63. 63. Course of the Inferior Alveolar canal
  64. 64. Results  Buccal cortex mean thickness = 2.3mm at the first molar  Buccal cortex mean thickness = 1.7mm at the third molar
  65. 65. At the 3rd molar site  Linear distance from the IA canal to the lingual surface of the buccal cortex = 1.7mm
  66. 66. Assessment of the lingual nerve in the third molar region using MRI Miloro, JOMS 55:134-37, 1997 Purpose: Determine the precise insitu location of the lingual nerve in the third molar region using high-resolution magnetic resonance imaging
  67. 67. Methods  Ten healthy volunteers (20 sites) with mandibular third molars underwent axial and coronal high-resolution MRI of the posterior mandible and floor of mouth  Three individuals measure the horizontal and vertical position of the LN
  68. 68. Diagram: Fig 1 and Fig 2
  69. 69. Results  The mean vertical 2.75± 0.97 (range 1.52-4.61mm)  The mean horizontal 2.53± 0.67 (range 0.00-4.35mm)
  70. 70. Results 10% of LN were superior to the lingual crest 25% of LN were in contact with the lingual cortex
  71. 71. Lack of Root Development
  72. 72. Complications Factors that may influence the occurrence of complications  Age  Gender “F”  Medical condition  Presence of pericoronitis  Poor oral hygiene  Type of impaction  Relationship to inferior alveolar nerve  Surgical time and technique  Surgeon experience  Use of perioperative antibiotics  Use of topical antiseptics  Anesthetic technique
  73. 73. Complications •Alveolar Osteitis (dray Socket) •Infection •Bleeding •Damage TO adjacent teeth •Mandibular fracture •Maxillary tuberosity fracture •Displacement of third Molars •Aspiration •Oro-antral communication/fistula •IAN/lingual nerve damage
  74. 74. Complications  Intraoperative: • Haemorrhage • Fractured root apex • damage to adjacent teeth/restoration/ soft tissues • Fracture mandible • Tooth ingestion or aspiration  Postoperative: • Dry socket [1-5%] or infection with purulent discharge • Sensory deficit-IAN=5% temp, lingual temp=10%, perm=<1% • Pain, swelling, bruising & trismus • Fracture mandible
  75. 75. Definition of Sensory Disturbances Paresthesia: an abnormal sensation, such as burning, pricking, tickling or tingling Dysesthesia: condition in which a disagreeable sensation is produced by ordinary stimuli Anesthesia; state characterized by loss of sensation, the result of pharmacologic depression of nerve function or of neurological disease
  76. 76. Partial Odentectomy  Indicated if intimate relationship with IAN  Root should be 3mm below bone level  Contraindicated if there is root pathology or loose tooth
  77. 77. Management of Impacted Maxillary Third Molar
  78. 78. AAOMS Workshop on the Management of Patients With Third Molar Teeth 1993  Little evidence that antibiotics decreases pain, edema, alveolar osteitis or infection  Lavage of the surgical site reduces risk of complications
  79. 79. AAOMS Workshop on the Management of Patients With Third Molar Teeth 1993  Tight primary closure increases frequency and severity of postoperative pain and swelling  Pericoronitis is a risk factor for alveolar osteitis and postoperative infection
  80. 80. Prophylactic Antibiotics for Third Molar Surgery
  81. 81. Five Possible Reasons  An infection is present and must be treated  The patient is medically compromised and requires antibiotic prophylaxis against metastatic infection  Patient or patient’s family demands antibiotics  The standard of care in the oral surgery community is to use antibiotics  The risk of postoperative infection is high
  82. 82. Risk/Benefit Assessment  Incidence of serious infections is low (estimated risk of 1-5%)  Cost of antibiotic therapy is low  Risk of development of resistant strains of bacteria is undetectable for individual practitioner  Risk of allergic reaction is higher than risk of infection
  83. 83. JOMS 53:53-60 1995  Piecuch JF et al- A Supportive Opinion  January 1994 survey of Connecticut Society of Oral and Maxillofacial Surgeons  N=104 (of 122)  58% routinely used antibiotics for surgical removal of fully submerged (impacted) mandibular third molars in patients who are not medically compromised  Dose regimens and method of application varied widely
  84. 84. Variations  Preoperative use  Postoperative use 1. Systemic Oral, parenteral 2. Topical Socket site
  85. 85. JOMS 53:53-60 1995  Zeitler D, A Dissenting Opinion  The low complication rate associated with the procedure does not support the routine use of antibiotic prophylaxis  The use of antibiotics to decrease the incidence of other adverse outcomes (alveolar osteitis, or dry socket) has not been determined to be successful
  86. 86. “Antibiotic Therapy in Impacted Third Molar Surgery” Monaco G, et al, Eur J Oral Sci 107 (6): 437-41, Dec 1999  N = 141 patients  66 patients with 2 gm amoxicillin daily for 5 days  75 patient without antibiotic therapy  No significant difference between groups  Association between smoking, habitual drinking and increase post op pain and fever
  87. 87. Analgesic Strategies
  88. 88. Acetylsalicylic Acid (aka aspirin) Class : Analgesic, Anti-pyretic (Gr. puretos fever) & Anti- inflammatory MOA : irreversible inhibition of cyclooxgenase clinical correlation: stop ASA 7d p surgery (exception) MOE : Excreted in urine Supplied: 325-650 mg Adult Dosage: PO 600 - 1000 mg q 4 - 6º Major Side effects : Bleeding & GI disturbances Interactions: anti-coagulants, alcohol
  89. 89. Membrane Phospholipids Arachidonic Acid PhospholipaseSTEROIDS Cyclooxygenase PROSTAGLANDINS NSAIDs Lipoxygenase LEUKOTRIE THROMBOXANE
  90. 90. Acetaminophen (aka Tylenol®) Class : Analgesic, Anti-pyretic, not anti-inflammatory MOA : Possible weak inhibition of cyclooxygenase MOE : Metabolized in liver, excreted in urine Peak plasma levels: 30 - 60 mins t1/2: 2 hrs Supplied: 325-650 mg Adult Dosage: PO 325-650 mg q 4 - 6º Max = 4g/day Major Side effects : Liver toxicity
  91. 91. Ibuprofen (aka Advil ®) Class : Analgesic, Anti-pyretic, Anti-inflammatory MOA : Inhibition of cyclooxgenase (both isoforms) MOE : Metabolized and excreted in kidney Peak plasma levels: 60 - 120 mins Half time: 120 mins Supplied: 200 mg Adult Dosage: PO 400 - 600 mg q 4 - 6º PO 800 mg q 8 - 10º Max = 3.2 g/day Major Side effects : GI Bleeding
  92. 92. Selective COX-2 inhibitors
  93. 93. Celecoxib (Celebrex ®) Class : Analgesic, Anti-pyretic, Anti- inflammatory MOA : Inhibition of cyclooxgenase 2 MOE : Metabolized in liver and excreted in kidney Peak plasma levels: 3 hours Half time: 11 hours Supplied: 100, 200 mg Adult Dosage: 100-200 mg PO BID Major Side effects : renal dysfunction, GI ulcerations, contraindication with pts with sulfa,NSAID allergies
  94. 94. Supplied in 12.5mg & 25mg tablets Contraindications: - allergies to sulfa, NSAIDs - GI bleeding, ulcerations - liver and kidney diseases - pregnancy Rx: 25-50mg PO daily prn pain Supplied in 10mg & 20mg table Rx: 10-20mg PO daily prn pain
  95. 95. Opioids µ κ δ
  96. 96. Codeine Class : Opioid MOA : binds to opioid receptors MOE : urine Peak plasma levels: 30 - 60 mins Half time: 3 -4 hrs Supplied: 15, 30, 60 mg Adult Dosage: PO 15 - 60 mg q 4 - 6º Max = 360 mg/day
  97. 97. • Sedation • respiratory depression • constipation • nausea Opioid triad: stupor, pupillary constriction & respiratory depression SIDE EFFECTS & COMPLICATIONS
  98. 98. Hydrocodone Class : Opioid analgesic MOA : opioid receptors MOE : urine Peak plasma levels: 30 - 60 mins Half time: 3 - 4 hrs Supplied: 5 mg Adult Dosage: 5 - 10 mg q 4º Major Side effects : Dizziness, sedation, nausea, vomiting, respiratory depression
  99. 99. Oxycodone Class : Opioid analgesic MOA : opioid receptor MOE : urine Peak plasma levels: 30 - 60 mins Half time: 3 -4 hrs Supplied: 5 mg Adult Dosage: PO 5 mg q 4 - 6º Major Side effects : Dizziness, sedation, N / V, respiratory depression
  100. 100. Propoxyphene Class : Opioid analgesic analgesic efficacy questionable MOA : opioid receptors MOE : urine Peak plasma levels: 2 - 3 hrs Half life: 12 hrs Supplied: 100 mg
  101. 101. Common Combination Analgesic Drugs
  102. 102. Common Combination Analgesic Drugs
  103. 103. POST-SURGICAL PAIN
  104. 104. Dionne RA. 1999. JOMS. 57: 673-678.  Sample size: 118 subjects  Surgical removal of 2 or 4 impacted third molars with sedation and local anesthetic  Subjects were questioned 15, 30, and 45 min. after loss of anesthesia about their pain
  105. 105. Methods  treatment groups:  Ibuprofen 400 mg  Ibuprofen 400 mg + Oxycodone 2.5 mg  Ibuprofen 400 mg + Oxycodone 5 mg  Ibuprofen 400 mg + Oxycodone 10 mg
  106. 106. Results - Only Ibuprofen 400 mg + oxycodone 10 mg provided better analgesia than Ibuprofen alone - Increasing doses of oxycodone α side effects
  107. 107. Flexible AnalgesicFlexible Analgesic StrategiesStrategies
  108. 108. Mild Pain Moderate Pain Severe Pain 400 -600 mg Ibuprofen or 650 mg ASA 650 - 1000 mg Acetaminophen Continue as needed Adequate analgesia Inadequate pain relief 600 - 800 mg Ibuprofen + Codeine 650 - 1000 mg Acetaminophen + Codeine Continue as needed Adequate analgesia Inadequate pain relief 600 - 800 mg Ibuprofen + Hydrocodone oroxycodone 650 - 1000 mg Acetaminophen + Hydrocodone or oxycodone Continue as needed Adequate analgesia
  109. 109. Pre-emptive Analgesia:Pre-emptive Analgesia: he pre-operative administration of analgesics
  110. 110. Analgesic Strategies  Use of long acting local anesthetic does display a synergistic effect with NSAIDs  Pre-emptive analgesia/anesthesia still being researched-recent data does not support presurgical administration for pain control
  111. 111. Use of Corticosteroids with Third Molar Removal
  112. 112. Esen E, et al, “Determination of the anti-inflammatory effects of methylprednisolone on the sequelae of third molar surgery”, J Oral Maxillofac Surg 57(10):1201-6, Oct 1999  N =20  Double blind crossover study  125 mg methylprednisolone vs. placebo  Pain and trismus evaluated
  113. 113. Esen E, et al, “Determination of the anti-inflammatory effects of methylprednisolone on the sequelae of third molar surgery”, J Oral Maxillofac Surg 57(10):1201-6, Oct 1999  Significant decrease in edema, trismus and pain in the methylprednisolone group  Normal HPA axis before and after  Plasma cortisol nonsignificant decrease in both groups
  114. 114. Esen E, et al, “Determination of the anti-inflammatory effects of methylprednisolone on the sequelae of third molar surgery”, J Oral Maxillofac Surg 57(10):1201-6, Oct 1999  No clinically apparent infection or disturbance of wound healing  90 % preferred the post operative course associated with steroid administration
  115. 115. What We Don’t Know What are the risks/complications/morbidities when impacted third molars are not removed?
  116. 116. What we do know  Cost in both time and risk exists with third molar removal in the older adult
  117. 117. Increased Costs Associated with Third Molar Removal in the Older Adult  Increased number of symptomatic post operative days requiring convalesence  Increased overhead costs due to increase in surgical complexity
  118. 118. Increased Costs Associated with Third Molar Removal in the Older Adult  Increase in complication management requiring an increase in the number of office visits  Increase in litigation costs
  119. 119. observe asymptomatic rem ove symptomatic <25 observe asymptomatic rem ove symptomatic >25 Patient with Third M olars
  120. 120. remove symptomatic remove pathology observe no observable pathology asymptomatic Patient with Third Molars [>25 yrs]
  121. 121. Obligations to observe  Frequency of imaging evaluation  every two years?  every five years?  Frequency of clinical evaluation  regular basis?  only when symptomatic?
  122. 122. Conclusions  Elective removal of symptomatic third molars in older adults is more costly and engenders greater risk than with prophylactic removal of third molars  Risks can be reduced with proper surgical technique
  123. 123. Conclusions  Modeling with computer enhanced “virtual reality” may allow study of predictability  More study is needed as the debate continues
  124. 124. IMPACTED MAXILLARY CANINE  The surgical removal of a deeply seated maxillary canine in relation to the maxillary sinus and the nasal cavity is one of the most difficult oral surgical procedures Frequency :  Maxillary canine is 20 times more than mandibular canine  More frequent in females than males  Palatal impaction is 3 times more than buccal impaction
  125. 125. Classification of impacted maxillary canine: ARCHER,S CLASSIFICATION Class I Palatally Impacted canine a) Horizontal b) Vertical c) semivertical Class II Buccally impacted canine a) Horizontal b) Vertical c) Semivertical Class III Impacted canine located in both the palatal and labial surfaces. Class IV Impacted canine located in the alveolar process. Class V Impacted canine located in an edentulous maxilla.
  126. 126. Contra-indications for the removal of an impacted maxillary canine: When it can be brought into normal position either by surgical repositioning or a combination of surgery and orthodontic treatment.. Factors complicating the removal of the impacted canine: Close relationship to the roots of the neighboring teeth. Intimate relation to the maxillary sinus. Curvature or hypercementosis of the root. Difficulty in localization most important factor.
  127. 127. SURGICAL REMOVAL OF IMPACTED MAXILLARY CANINE Planning the operative procedure X-ray examination Classify the impaction Extent of the flap Sectioning of the tooth is needed or not
  128. 128. Localization of impacted maxillary canine:  clinical examination  Radiographic examination Clinical examination:  By palpation:  Presence of distinct bulge  Deflection of crowns: mostly of lateral incisors pr premolars. Radiological examination:  a) Intra-oral periapical films  b) Occlusal radiographs ( topographical & cross sectional ): Canine will appear as a round radioapaque structure.
  129. 129.  c) Shift sketch technique: In This technique, the films are in the same position while the cone is shifted, if the canine moves with same direction of the cone , it indicates that it is located far (palatally), while if the canine moves opposite to the direction of the cone , it indicates that it is near (buccally).
  130. 130.  e) Tomograms: Sections are taken, if the canine is impacted buccally , it's tip will appear first , while if impacted palatally, the apex will appear first.
  131. 131. f) Extra-oral oblique or true lateral:
  132. 132. g) Panoramic films: To determine relation to maxillary sinus.
  133. 133. Object Localization A periapical film will identify the location of an object vertically and in a horizontal (mesiodistal) direction. However, we cannot tell where the object is located buccolingually, since the periapical film is two-dimensional. Therefore we need another method for locating objects in a buccolingual direction. The two primary methods of determining the buccolingual location of objects are: Right-Angle Technique (Occlusal projection) Primarily identifies buccolingual location, but may also confirm mesiodistal location seen on periapical Tube-shift Technique (SLOB rule, Clark’s rule) Utilizes two films with different horizontal or vertical angulations
  134. 134. Right Angle (Occlusal) technique Right Angle Technique Once you have identified an object on the periapical film, you can take an occlusal film with the beam at a right angle (perpendicular) to the direction of the beam for the periapical. The beam may also be perpendicular to the film, especially in the mandible. The occlusal film below shows that the impacted canine is lingually positioned.
  135. 135. The SLOB rule is used to identify the buccal or lingual location of objects (impacted teeth, root canals, etc.) in relation to a reference object (usually a tooth). If the image of an object moves mesially when the tubehead is moved mesially (same direction), the object is located on the lingual. If the image of the object moves distally when the tubehead moves mesially (opposite direction), the object is located on the buccal. Tube-Shift Localization (Clark) SLOB Rule Same Lingual Opposite Buccal
  136. 136. For the SLOB rule to work, there must be a change in the horizontal or vertical angulation of the x-ray beam as the tubehead is moved. This change in angulation will alter the relationship between the object of interest and the reference object, allowing you to determine the buccal or lingual location. The closer the object to be localized is to the reference object, the less the amount of movement of the image of the object in relation to the reference object.
  137. 137. In the diagram at right, the tubehead is moved, but there is no change in direction of the x-ray beam, which results in no change in location of the object of interest in relation to reference object (see below). Moving the tubehead without changing the beam direction would often result in a cone cut , depending on how far the tubehead is moved (see below right).
  138. 138. premolar molar For the films above, we know that the tubehead was moved distally from the premolar to the molar film. The zygomatic process (red arrows) is located at the distal aspect of the 2nd molar on the premolar film and it is located over the distal aspect of the 1st molar on the molar film. This indicates that it moved mesially as the tubehead moved distally. We know that the zygomatic process is buccal to the teeth and, using the SLOB rule, it follows that the x-ray beam was directed more mesially on the molar film (Buccal object moved opposite to tubehead movement).
  139. 139. premolar molar Another way of determining the change in the direction of the beam is to look at the angulation of the teeth. In the premolar film, the roots of the teeth are angled distally, indicating that the beam was directed distally (from the mesial). In the molar film, the roots are more upright or angled slightly mesially, indicating the beam was directed more mesially (from the distal). Therefore, the tubehead shifted distally and the beam was angled in the opposite direction, allowing the use of the SLOB rule (These films were taken from Slide 3 in the review films to follow).
  140. 140. Is the composite restoration on tooth # 8 (arrows) located on the buccal or lingual? canine film incisor film 1The restoration is located on the buccal. The tubehead moves mesially from the canine film to the incisor film (x-ray beam projected more distally) and the composite moves distally, which is the opposite direction.
  141. 141. canine film premolar film The arrow in the canine film is pointing to the gutta percha in which canal of the maxillary first premolar? 2 The arrow identifies the lingual canal. The tubehead moves mesially from the premolar film to the canine film (beam directed more distally) and the gutta percha indicated by the arrow also moves mesially. (See following slide).
  142. 142. PID PID lingual buccal When the tubehead is moved mesially, with the beam directed distally, the two canals, which are initially superimposed (premolar periapical above) will separate. The lingual canal (red arrow) will follow the tubehead movement and the buccal canal (blue arrow) will move in the opposite direction, as seen on the canine film.
  143. 143. Is the maxillary second premolar (arrows) displaced to the buccal or the lingual? premolar film molar film premolar bitewing 3 The tubehead moves distally from the premolar film to the molar film. The second premolar also moves distally, overlapping the first molar more in the molar film. In moving from the premolar periapical to the bitewing, the tubehead moves down and the premolar also moves down. The displacement is to the lingual.

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