Impacted teeth

Impacted Wisdom Teeth
Dr. Hesham Marei MSc, PhD, MFDS (Eng)
Assistant Professor of oral and Maxillofacial Surgery
King Faisal University

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

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.

Theories of Impaction
Smaller jaws/fast growth
Diet changes
Mechanical obstacles
Vestigial theory

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

Classification Systems
 Angulations
 Vertical
 Distoangular
 Mesioangular
 Horizontal
 Buccal/Lingual
 Relationship to anterior border of ramus
 Depth of impaction
 Nature of overlying tissue

VERTICAL HORIZONTAL
MESIOANGULAR DISTOANGULAR
According to the long axis of the neighbouring mesial tooth

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

Relationship to Anterior Border of
Ramus
(Pell and Gregory)
 Class I - adequate room to erupt
 Class II - one half covered
 Class III- completely embedded

Pell and Gregory Classification (relation to the ramus)

Imaging, Evaluation and
Assessment

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

Other Important Factors
 Size of Follicular Sac
 Density of Surrounding Bone
 Contact with Mandibular Second Molar
 Relationship to Inferior Alveolar Nerve

8
Relation to IACRelation to IAC

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.

Indications & Contraindications

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

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.

Problem #3 – 3rd
Molar Caries

Problem #4 – 2nd
Molar Caries

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

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

Pericoronitis
The most
common cause
of therapeutic
3rd
molar
removal.

Pericoronitis
 Inflammation of
the tissues around
the crown of any
partially erupted/
impacted tooth.
 It is either acute
or chronic

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.

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

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

Problem #8 - Cysts
Dentigerous
Cyst

Dentigerous Cyst
Supernumerary
4th
Molar

Types of Cysts
 Follicular cyst (Dentigerous Cyst)
 OKC (Odontogenic Keratocyst)
 Ameloblastoma (several varieties)
 Not all radiolucencies are cysts!
- Lymphoma
- Myeloma
- Metastatic carcinoma

Without the
radiolucency, would
you have
recommended
removal?
Is the removal of
this better or worse
with the
radiolucency?

When would you
recommend removal
of this 3rd
molar?

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.

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.

Problem #9 - Tumors
 Benign vs. malignant
 Odontogenic vs. non-odontogenic
 Each of these factors has important
treatment implications.

Problem #10 – Risk of Fracture

Problem #12 - Orthodontics
 Prevent loss of post-
retention stability
 Allow distalization of
2nd
molars
 These are
controversial
indications

Possible Contraindications to Removal
of Impacted Teeth
• Extremes of age
• Compromised medical
status
• Probable excessive
damage to adjacent
structures
• Asymptomatic teeth

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

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

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

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.

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

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.

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

 ≈ 7.8mm at the
3rd molar
 ≈ 10mm
Between the
first and second
molar

Course of the Inferior Alveolar
canal

Results
 Buccal cortex mean
thickness = 2.3mm at the
first molar
 Buccal cortex mean
thickness = 1.7mm at the
third molar

At the 3rd
molar site
 Linear distance from the IA
canal to the lingual surface of
the buccal cortex = 1.7mm

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

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

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)

Results
10% of LN were superior to the lingual crest
25% of LN were in contact with the lingual cortex

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

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

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

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

Partial Odentectomy
 Indicated if intimate
relationship with IAN
 Root should be 3mm
below bone level
 Contraindicated if there
is root pathology or
loose tooth

Management of
Impacted Maxillary
Third Molar

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

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

Prophylactic
Antibiotics for Third
Molar Surgery

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

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

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

Variations
 Preoperative use
 Postoperative use
1. Systemic
Oral, parenteral
2. Topical
Socket site

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

“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

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

Membrane
Phospholipids
Arachidonic Acid
PhospholipaseSTEROIDS
Cyclooxygenase
PROSTAGLANDINS
NSAIDs
Lipoxygenase
LEUKOTRIE
THROMBOXANE

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

Ibuprofen
(aka Advil ®)
Class : Analgesic, Anti-pyretic, Anti-inflammatory
MOA : Inhibition of cyclooxgenase (both isoforms)
MOE : Metabolized and excreted in kidney
Half time: 120 mins
Supplied: 200 mg
PO 800 mg q 8 - 10º
Max = 3.2 g/day
Major Side effects : GI Bleeding

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

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

Codeine
Class : Opioid
MOA : binds to
opioid receptors
MOE : urine
Half time: 3 -4 hrs
Supplied: 15, 30, 60 mg
Max = 360 mg/day

• Sedation
• respiratory
depression
• constipation
• nausea Opioid
triad: stupor,
pupillary
constriction &
respiratory
depression
SIDE EFFECTS &
COMPLICATIONS

Hydrocodone
Class : Opioid analgesic
MOA : opioid receptors
MOE : urine
Half time: 3 - 4 hrs
Supplied: 5 mg
Adult Dosage: 5 - 10 mg q 4º
Major Side effects :
Dizziness, sedation, nausea,
vomiting, respiratory depression

Oxycodone
MOA : opioid receptor
MOE : urine
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

Propoxyphene
analgesic efficacy questionable
MOA : opioid receptors
MOE : urine
Peak plasma levels: 2 - 3 hrs
Half life: 12 hrs
Supplied: 100 mg

Common Combination
Analgesic Drugs

Common Combination Analgesic
Drugs

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

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

Results
- Only Ibuprofen 400 mg + oxycodone 10
mg provided better analgesia than
Ibuprofen alone
- Increasing doses of oxycodone α side
effects

Flexible AnalgesicFlexible Analgesic
StrategiesStrategies

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

Pre-emptive Analgesia:Pre-emptive Analgesia:
he pre-operative administration of
analgesics

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

Use of Corticosteroids
with Third Molar
Removal

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

 Significant decrease in edema, trismus
and pain in the methylprednisolone group
 Normal HPA axis before and after
 Plasma cortisol nonsignificant decrease
in both groups

 No clinically apparent infection or
disturbance of wound healing
 90 % preferred the post operative course
associated with steroid administration

What We Don’t Know
What are the
risks/complications/morbidities
when impacted third molars
are not removed?

What we do know
 Cost in both time and risk exists with third
molar removal in the older adult

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

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

observe
asymptomatic
rem ove
symptomatic
<25
observe
asymptomatic
rem ove
symptomatic
>25
Patient with Third M olars

remove
symptomatic
remove
pathology
observe
no observable pathology
asymptomatic
Patient with Third Molars
[>25 yrs]

Obligations to observe
 Frequency of imaging evaluation
 every two years?
 every five years?
 Frequency of clinical evaluation
 regular basis?
 only when symptomatic?

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

Conclusions
 Modeling with computer enhanced “virtual
reality” may allow study of predictability
 More study is needed as the debate
continues

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

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.

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.

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

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.

 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).

 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.

f) Extra-oral oblique or true lateral:

g) Panoramic films:
To determine relation to maxillary sinus.

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

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.

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

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.

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).

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).

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).

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.

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).

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.

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.

Impacted teeth

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