Tooth impaction
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Jaspinder Kaur, MBBS[2]
Synonyms and keywords:
Overview
Impacted and embedded teeth are the two main types of unerupted teeth found in the mouth, and can sometimes be confused with each other. In both cases, the teeth remain below the surface of the gum, rather than erupting into an exposed position within the mouth, but the reason for the failure to erupt differs. Impacted teeth result from a situation in which an unerupted tooth is wedged against another tooth or teeth or otherwise located so that it cannot erupt normally. In contrast, an embedded tooth is an unerupted tooth that is covered, usually completely, with bone. That is to say, something that is physically blocking the pathway of eruption (such as another tooth) is the case for an impacted tooth, whereas the lack of eruptive force results in an embedded tooth.
Mandibular third molars are the most commonly found unerupted teeth, while maxillary third molars are second most common.
Tooth impactions are prevalent in clinical practice. The order of frequency of tooth impaction includes mandibular and maxillary third molars, maxillary canines, mandibular premolars, mandibular canines, maxillary premolars, maxillary central incisors, maxillary lateral incisors, and mandibular second molars. In most cases, a diagnosis of supernumerary or impacted teeth is based on clinical symptoms and radiographic examination; the most common diagnoses are made by panoramic, occlusal, and periapical radiographs. Hence, diagnosis is based on clinical examination coupled with imaging, especially cone beam CT (CBCT) scans. Treatment of impacted teeth should be based on clinical symptoms, location of the teeth, and a comprehensive examination of the impact of these teeth on neighboring teeth. Good Orthodontic mechanics, surgical planning, and patient education is essential to success. Surgical considerations include local anatomic concerns, anesthesia method, flap design, bone removal/coronal exposure, surgical instrumentation, bonding material characteristics, tooth ankylosis, and minimization of surgical complications.
Historical Perspective
Classification
- Traditionally, both the Winter’s and Pell & Gregory’s systems propose to classify the inclinations and positions of the third molars based on the relation among the dental longitudinal axis, occlusal plane and ascending mandibular ramus. Radiologically, individual anatomy, demographic aspects and operative factors are considered important variables to the determination of surgical difficulties and postoperative complication risks.
- Tooth impaction is classified based on various factors which are elaborated in following tables:
Table 1: Winter’s and Pell & Gregory’s criteria
| Classification | Clinical description | Type |
|---|---|---|
| Pell and Gregory classification | Impaction depth: the relation of the cementoenamel junction (CEJ) of the third molar with the bone level is graded |
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| Pell and Gregory classification | Ramus relationship: the position of the distal surface of the third molar crown in relation to the anterior border of the ascending ramus is categorized |
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| Winter’s classification | Impaction angulation: the angle between the longitudinal axis of the second and third molars (which was measured by an orthodontic protractor) is categorized |
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| Nature of overlying tissue | This system is used by most dental insurance companies and one by which surgeon charges for his services. |
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Pathophysiology
- Impacted teeth can be classified as entirely or partially unerupted teeth. The most common impacted teeth are the third molars since they are the last to erupt and usually remain impacted due to the lack of space in the dental arch. Partially erupted impacted third molars (ITM) have been associated with odontogenic infections, such as caries, periodontal diseases, and pericoronitis. Due to difficulties in reaching partially erupted teeth during oral hygiene, dental caries and endodontic illnesses are more frequently observed in comparison to entirely unerupted teeth. On the other hand, non-inflammatory conditions such as the dentigerous cysts (DC), odontogenic keratocysts (OKC), and ameloblastomas are mostly related to entirely unerupted ITM.
- This situation is pathological and can lead to various clinical conditions, including pericoronitis, adjacent root resorption, cystic lesions, or neoplasm.
- Process of tooth eruption involves complex interaction between osteoblasts, osteoclasts and dental follicular cell lines associated with the tooth germ which result in coordinated alveolar bone resorption and emergence of tooth within the oral cavity. Teeth may fail to erupt either as a result of mechanical obstruction, be it idiopathic or pathological in origin or because of disruption to the eruptive mechanism itself. The terms ‘impaction’ and ‘retention’ are often used synonymously for eruption failure but actually they are separate pathologies with different etiology and treatment approaches.
Etiology
- The term impaction originates from a Latin word impactus. It is defined as a cessation of eruption of a tooth caused by a clinically or radiographically detectable physical barrier in the eruption path or by an ectopic position of the tooth. Common causes contributing to impaction are lack of space or crowding of dental arches, premature loss of the primary teeth with subsequent partial closure of the area, rotation of tooth buds, supernumerary teeth, odontoma or cyst in the path of eruption.
Differentiating Tooth Impaction from other Diseases
Table 2: Enlist the differential diagnosis for tooth impaction
| System involved | Characteristic features |
|---|---|
| Cleidocranial dysostosis | Short tapered fingers and broad thumbs; flat feet; knock knees; short shoulder blades (scapulae); scoliosis; short skull (brachycephaly); a prominent forehead; wide-set eyes (hypertelorism); a flat nose; small upper jaw; impacted and crowded teeth. |
| Gardners syndrome | Multiple impacted and supernumerary teeth, multiple jaw osteomas, multiple odontomas, congenital hypertrophy of the retinal pigment epithelium (CHRPE), and multiple adenomatous colonic polyps. |
| Gorlin–Sedano syndrome | Short hands, short foot bones, short and straight collar bone, and multiple impacted teeth. |
| Yunis–Varon Syndrome | Agenesis or hypoplasia of clavicle, severe micrognathia, digital anomalies, hypodontia, spinal defects, and impacted teeth. |
| Osteogenesis Imperfecta | Blue sclera, abnormal and impacted teeth, hearing problems, osteoporosis, wormian bones, joint laxity, and short stature. |
Epidemiology and Demographics
- It has been detected more often in the unilateral form than the bilateral and is more common in the mandible than in the maxilla.
Risk Factors
Screening
Natural history, Complications, and Prognosis
- In the United States, approximately 3 billion dollars are spent yearly on the extraction of third molars. Whether it be for prophylactic, orthodontic and prosthetic reasons or for the diagnosis of several associated pathologies, the surgical removal of these teeth is one the most performed dentoalveolar procedures in oral and maxillofacial surgery. Reasons for extracting ITM include the risk of developing dental caries, pericoronitis, periodontal defects, crowding, and occurrence of different odontogenic cysts and tumors. However, there is a lack of substantial evidence supporting the extraction of asymptomatic ITM, especially considering the morbidity and the costs of the procedure. Thus, further investigations on this topic are necessary to aid surgeons in the decision-making process. The presence of odontogenic cysts and tumors in the third molar region can cause severe consequences, such as pathological mandibular fracture and facial asymmetry. Nonetheless, surgical removal of ITM might present complications, which might occur in up to 15% of cases, such as nerve injuries, post-operative infections, and iatrogenic mandibular fractures. Therefore, the clinical conduct regarding asymptomatic ITM should weigh the risks of removal and benefits of tooth preservation.
Diagnosis
Staging | History & Symptoms | Physical Examination | Laboratory Tests | Chest X Ray | CT | MRI | Echocardiography or Ultrasound | Other Imaging Findings | Other Diagnostic Studies
Treatment
Medical Therapy | Surgery | Primary Prevention | Secondary Prevention | Cost-Effectiveness of Therapy | Future or Investigational Therapies
- Treatment can be instituted on the basis of etiology.
- In case of impaction, early removal of physical barrier increases the chances of spontaneous eruption followed by orthodontic uprighting if required.
- In case of primary retention, involved teeth tend to ankylose if orthodontic force is applied. Unerupted tooth can be surgically repositioned following segment alveolar osteotomy. Prosthetic replacement of missing (unerupted) tooth is the last resort.
- In case of secondary retention, luxation of exposed tooth sometimes promotes eruption. If secondary retention develops prior to growth spurt, immediate removal of affected molar followed by orthodontic alignment of neighboring teeth can be done. Autotrasplantation of third molar into the space created by missing teeth can be done.
References