4. RESULTADOS
4.2 C ARACTERIZACIÓN ULTRAESTRUCTURAL DEL LINAJE OLIGODENDROGLIAL Y DE LA POBLACIÓN
Impacted teeth seen in the following order of frequency:
1. Mandibular third molars 2. Maxillary third molars 3. Maxillary canine 4. Mandibular premolar 5. Maxillary premolar 6. Mandibular canine 7. Maxillary central incisors 8. Maxillary lateral incisors.
Causes of Impaction of Teeth
Inadequate Space in the Dental Arch for Eruption The phylogenic theory Due to evolution, the human jaw size is becoming smaller and since the third molar tooth is last to erupt, there may not be room for it to emerge in the oral cavity.
Mendelian theory Here genetic variations play a major role. If the individual genetically receives a small jaw from one of the parents and/or large teeth from the other parent, then impacted teeth can be seen, because of ‘lack of space’.
Causes of impaction of a tooth can be divided into local and systemic causes (Table 10.1).
Indications for Removal of Impacted Teeth
• Recurrent pericoronitis/pain/infection/caries—
pericoronitis is the inflammation of the gingiva surrounding a crown of a partially erupted tooth
• Deep periodontal pocket associated with partially erupted tooth
• Prior to orthodontic treatment—to control the tooth crowding in the mandible
• Prevention of root resorption and caries—caries of the impacted tooth crown and the adjacent tooth can be seen due to an inability to access and clean the area. Root resorption of the distal root of the adjacent second molar is seen in the 21 to 30 years of age group. Root resorption of lateral incisor may be seen associated with an impacted maxillary or mandibular canine
• Management of cysts and tumours, abscess of odontogenic origin (Associated lesions).
• Prevention of pathological fractures
• Preparation of orthognathic surgery—prior to sagittal split osteotomy of ramus in order to avoid bad split—inadvertent fracture of the mandible, lower third molars are extracted. Maxillary third molars are removed during Le Fort I osteotomy procedure
• Management of preprosthetic concerns—before the fabrication of the prosthesis, impacted teeth should be removed
• Impacted teeth in the line of fracture
• Prophylactic removal.
Table 10.1. Local and systemic causes of impaction of tooth
Local causes Systemic causes
• Obstruction for eruption • Prenatal causes—heredity
— irregularity in position and presence of an adjacent tooth.
— density of the overlying and surrounding bone
• Lack of space in the dental arch—crowding, supernumerary • Postnatal—ricketts, anaemia, tuberculosis, congenital syphilis,
teeth. malnutrition
• Ankylosis of primary or permanent teeth • Endocrinal disorders of thyroid, parathyroid, pituitary glands like hypothyroidism, achondroplasia, etc. Here the primary retention of teeth is seen due to lack of osteoclastic activity, which does not provide resorption of the bone overlying the developing tooth
• Nonabsorbing, over-retained deciduous teeth • Hereditary-linked disorders—Down syndrome, Hurler’s syndrome, osteopetrosis. Cleidocranial dysostosis, cleft palate, etc.
Here failure of the overlying bone to resorb and develop an eruption pathway is absent
• Nonabsorbing alveolar bone
• Ectopic position of tooth bud
• Dilaceration of roots (trauma)
• Associated soft tissue or bony lesions
• Habits involving tongue, finger, thumb, cheek, pencil, etc.
(Secondary retention—ankylosis of teeth. Infra-occlusion of the tooth is seen due to arrested eruption, after initial emergence without any obvious barrier such as a tooth, tissue or habit to block eruption)
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Risk of Nonintervention
• Crowding of dentition based on growth prediction
• Resorption of adjacent tooth and periodontal status
• Development of pathological conditions such as infection, cyst, tumour.
Risk of Intervention
Minor transient Sensory nerve alteration, alveolitis, trismus and infection. Haemorrhage, dentoalveolar fracture and displacement of tooth.
Minor permanent Periodontal injury, Adjacent tooth injury, Temporomandibular joint injury.
Major Altered sensation, Vital organ infection, Fracture of the mandible, maxillary tuberosity. Injury and litigation.
Benefits of Nonintervention
• Avoidance of risk.
• Preservation of functional teeth.
• Preservation of residual ridge.
Benefits of Intervention
• In relation to age—in young patients, less morbidity.
• In relation to different therapeutic measures. Local measures against alveolitis, pain, swelling and trismus, etc.
Classification of Impacted Teeth
Maxillary and mandibular third molars are classified radiographically by angulation, depth and arch length or relationship to the anterior aspect of the ascending mandibular ramus.
Classification is helpful for the
following-• Describes the general position of the impacted third molar.
• Aids in estimating the difficulty in removing the tooth.
Difficulty Index
• Very difficult : 7 to 10
• Moderately difficult : 5 to 7
• Minimally difficult : 3 to 4
From Table 10.2 difficulty index can be arrived at as follows:
Distoangular impaction 4
Level B 2
Class II 2
Eight is the total difficulty score. Very difficult extraction.
Winter’s Classification (Fig. 10.2A)
Angulation According to the position of the impacted third molar to the long axis of the second molar. The Winter’s classification is suggested:
1. Mesioangular These may occur 2. Horizontal/transverse/ simultaneously in:
inverted i. buccal version 3. Vertical ii. lingual version 4. Distoangular iii. Torsoversion 5. Buccoangular
6. Linguoangular
• Mesioangular impaction is the most common finding.
• Forty-three per cent of mandibular impacted third molars are mesioangular
• Sixty-three per cent of maxillary impacted third molars are mesioangular.
Depth (Fig.10.2B) As per the relationship to the occlusal surface of the adjoining second molar of the impacted maxillary or mandibular third molar, the depth can be judged.
1. Position A: The highest position of the tooth is on a level with or above the occlusal line.
2. Position B: Highest position is below the occlusal plane, but above the cervical level of the second molar.
3. Position C: Highest position of the tooth is below the cervical level of the second molar.
The deeper the impacted tooth, the more overlying bone is present and the more the angulation of impaction deviates from parallel to the long axis of the adjacent tooth, the more difficult it is to remove the impacted tooth.
Table 10.2. Difficulty index for removal of impacted lower third molars
Classification Difficulty index value
Angulation
Mesioangular 1 easiest to remove
Horizontal/transverse 2
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Pell and Gregory’s Classification (Fig. 10.2C)
Relationship of the impacted lower third molar to the ramus of the mandible and the second molar (Based on the space available distal to the second molar).
• Class I: Sufficient space available between the anterior border of the ascending ramus and the distal side of the second molar for the eruption of the third molar.
• Class II: The space available between the anterior border of the ramus and the distal side of the second molar is less than the mesiodistal width of the crown
of the third molar. It denotes that the distal portion of the third molar crown is covered by the bone from the ascending ramus
• Class III: The third molar is totally embedded in the bone from the ascending ramus because of absolute lack of space.
Maxillary Third Molars’ Classification (Fig. 10.2D) 1. Angulation and Depth classification is same as
mandibular third molars.
2. Classification of the maxillary third molar in relation to the floor of maxillary sinus.
a. Sinus approximation (SA)—no bone or a thin bony partition present between impacted maxillary third molar and the floor of the maxillary sinus.
b. No sinus approximation (NSA)—2 mm or more bone is present between the sinus floor and the impacted maxillary third molar.
Classification of Impacted Maxillary Canines (Fig. 10.2E)
• Labial or palatal placement of impacted maxillary canine
• Intermediate position
a. Crown between the lateral incisors and premolar.
b. Crown above the root tip with labial/palatal orientation of the lateral incisor or premolar.
Fig. 10.2A: Winter’s classification of impacted mandibular third molars: (a) mesioangular (b) distoangular, (c) vertical, (d) horizontal, (e) buccoangular, (f) linguoangular, (g) inverted
Fig. 10.2B: Classification of impacted mandibular third molars according to the depth of impaction
Fig. 10.2C: Pell and Gregory’s classification
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• Aberrant position
Impacted maxillary canines lie in the maxillary sinus or nasal cavity.
• Class I: Palatally placed maxillary canine a. Horizontal
b. Vertical c. Semivertical
• Class II: Labially or buccally placed maxillary canine a. Horizontal
b. Vertical c. Semivertical
• Class III: Involving both buccal and palatal bone, e.g.
crown is placed on the palatal aspect and the root is toward the buccal alveolar process
• Class IV: Impacted in the alveolar process between the incisors and first premolar.
• Class V: Impacted in the edentulous maxilla.
Classification for Impacted Mandibular Canine (Table 10.3)
Table 10.3. Classification for impacted mandibular canine
Labial Aberrant
• Vertical • At inferior border
• Oblique • On the opposite side
• Horizontal
Fig. 10.2D: Classification of impacted maxillary third molars: (1) Mesioangular, (2) Distoangular, (3) Vertical, (4) Horizontal, (5) Buccoversion, (6) Linguoversion, (7) Inverted
Fig. 10.2E: Impacted maxillary canine position; (1) Palatally placed, (2) Labially placed, (3) Partly on the labial side and partly on palatal side, (4) Canine locked between the roots of adjacent teeth, (5) Canine in the edentulous maxilla
Factors Responsible for Increasing the Difficulty Score for Removal of Impacted Teeth
• As per the angulation
• As per the depth
• As per the space available for the eruption
• Crown size—large bulbous crown increases the difficulty
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• Configuration of the roots of the impacted tooth—
the point of application of the elevator and the path of delivery of the impacted tooth depends mainly on the configuration of the roots.
a. Length of the roots—longer the roots—more difficult the extraction.
b. Root development—if the root development is (less than one-third) insufficient, then the tooth is more difficult to remove. It moves like a ball in the socket and difficult to elevate.
c. Curvature of the roots—dilacerated, curved, diver-gent roots are difficult to remove. Fused conical roots are easy.
d. Root size— thin, slender roots are difficult to remove. Stout, bulbous, hypercementosed roots also increase the difficulty.
• Bone texture and density—depends on the age, sex and systemic problems. Younger patients have spongy, elastic pliable bone, while older group of patients may exhibit sclerosed bone.
• Size of the follicular sac—presence of large follicular sac makes the extraction easier, as the amount of bone removal is less. Nonexistent or narrow follicular sac around the crown will require bone cutting around the crown – Difficult extraction.
• Space or contact in relation to mandibular second molar—If the impacted tooth is locked against the crown of the second molar and there is no space for elevation, then sectioning of the tooth should be planned.
• Relationship to the inferior alveolar neurovascular bundle—proximity of the roots to the neurovascular bundle increases the possibility of the damage/
injury to the nerve during extraction. Temporary altered sensation of the lower lip can be experienced by the patient (paraesthesia/anaesthesia) which can last for few days/few months. Radiological assessment is important. Dentascan can show exact location of the nerve.
• Nature of covering tissue:
a. Soft tissue impaction
b. Partial bony impaction—covered by soft tissue, as well as partially by the bone.
c. Fully bony impaction
• Access to the operative field, inability to open the mouth wide, a large uncontrollable tongue, small orbicularis oris muscle (oral sphincter).
Radiological Examination Intraoral X-ray
• Intraoral X-rays are possible, if tooth is in the alveolus and not in the ramus
• Possible if oral opening is adequate
• If there is no gagging
• Useful to study the relation with adjoining tooth
• Useful to study the configuration of the roots and status of the crown (caries, size, etc.)
• Useful to record the relationship with inferior alveolar canal
• For bucco or linguoversion ‘tube shift’ method should be used or occlusal film is taken.
The position and depth of the tooth can be assessed by taking intraoral X-ray or even lateral extraoral X-ray and tracing can be done, which was originally advocated by George Winter.
Three imaginary lines are drawn which are known as Winter’s lines (Fig. 10.2F).
• White line—corresponds to the occlusal plane. The line is drawn touching the occlusal surfaces of first and second molar and is extended posteriorly over the third molar region. It indicates the difference in occlusal level of second and third molars.
• Amber line—represents the bone level. The line is drawn from the crest of the interdental septum bet-ween the molars and extended posteriorly distal to third molar or to the ascending ramus. This line denotes the alveolar bone covering the impacted tooth and the portion of tooth not covered by the bone.
• Red line—is drawn perpendicular from the amber line to an imaginary point of application of the elevator. It indicates the amount of bone that will have to be removed before elevation, i.e. the depth of the tooth in bone and the difficulty encountered in removing the tooth.
If the length of the red line is more than 5 mm then the extraction is difficult. Every additional mm renders the removal of the impacted tooth three times more Fig. 10.2F: Winter’s lines: W-White line, A-Amber line, R-Red line
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difficult (more than 9 mm—below the level of the apices of the second molar).
Extraoral X-rays (Figs 10.2G 1, 2, 3)
For mandibular teeth For maxillary teeth
• OPG • OPG
• Lateral oblique view • PA view Water’s position mandible
Indicated in
• Patients with restricted oral opening/trismus/
excessive gagging
• Impacted tooth in an aberrant position
• For ruling out associated pathology
• To study the relationship of the tooth to inferior alveolar nerve (Fig. 10.2H) and (Figs 10.2-I: 1, 2, 3)/
inferior border. For maxillary teeth—relationship to the maxillary sinus.