INTRODUCTION:

Impacted wisdom teeth (also known as impacted third molars) is the failure of the wisdom teeth to erupt fully into the mouth because of blockage from another tooth and affects up to 72% of the population¹. Wisdom teeth likely become impacted because of a mismatch between the size of the teeth and the size of the jaw. Impacted wisdom teeth are classified by their direction of the impaction, depth compared to the biting surface of adjacent teeth and the amount of the tooth crown that extends through bone or mucosa. Wisdom teeth have been described in the ancient texts of Plato and Hippocrates, the works of Darwin and in the earliest manuals of operative dentistry. It was the meeting of sterile technique, radiology and anaesthesia in the late 19th and early 20th centuries that allowed the more routine management of impacted wisdom teeth². Wisdom teeth that are fully erupted and in normal function need no special attention and should be treated just like any other tooth. It is more challenging, however to make treatment decisions with asymptomatic, disease-free wisdom teeth, i.e. wisdom teeth that have no communication to the mouth and no evidence of clinical or radiographic disease.

Classification:

All teeth are classified as either developing, erupted (into the mouth), embedded (failure to erupt without blockage from another tooth) or impacted (failure to erupt due to blockage from another tooth). Wisdom teeth develop between the ages of 14 and 25, with 50% of root formation completed by age 16 and 95% of all teeth erupted by the age of 25. However, tooth movement can continue beyond the age of 253. Impacted wisdom teeth are classified by the direction and depth of impaction, the amount of available space for tooth eruption and the amount soft tissue or bone that covers them. The classification structure allows clinicians to estimate the probabilities of impaction, infections and complications associated with wisdom teeth removal. Wisdom teeth are also classified by the presence (or absence) of symptoms and disease.

Causes of impaction:

Wisdom teeth become impacted when there is not enough room in the jaws to allow for all of the teeth to erupt into the mouth. Because the wisdom teeth are the last to erupt, due to insufficient room in the jaws to accommodate more teeth, the wisdom teeth become stuck in the jaws, i.e., impacted. There is a genetic predisposition to tooth impaction. Genetics plays an important, albeit unpredictable role in dictating jaw and tooth size and tooth eruption potential of the teeth. Some also believe that there is a evolutionary decrease in jaw size due to softer modern diets. The formation of wisdom teeth differs by population, ranging from practically zero in Tasmanian Aborigines to nearly 100% in indigenous Mexicans. The difference is related to the PAX9 gene4.

Signs of impaction:

Impacted wisdom teeth without a communication to the mouth, that have no pathology associated with the tooth and have not caused tooth resorption on the blocking tooth rarely have any symptoms. When wisdom teeth communicate with the mouth, the most common symptom is localized pain, swelling and bleeding of the tissue overlying the tooth. This tissue is called the operculum and the disorder called pericoronitis which means inflammation around the crown of the tooth5. Low grade chronic periodontitis commonly occurs on either the wisdom tooth or the second molar, causing less obvious symptoms such as bad breath and bleeding from the gums. The teeth can also remain asymptomatic (pain free), even with disease. As the teeth near the mouth during normal development, people sometimes report mild pressure of other symptoms similar to teething. The term asymptomatic means that the person has no symptoms. The term asymptomatic should not be equated with absence of disease. Most diseases have no symptoms early in the disease process. A pain free or asymptomatic tooth can still be infected for many years before pain symptoms develop6.

Diagnosis:

The diagnosis of impaction can be made clinically if enough of the wisdom tooth is visible to determine its angulation, depth, and if the patient is old enough that further eruption or uprighting is unlikely. Wisdom teeth continue to move into adulthood (20–30 years old) due to eruption and then continue some later movement owing to periodontal disease. If the tooth cannot be assessed with clinical exam alone, the diagnosis is made using either a panoramic radiograph or cone-beam CT7. Where unerupted wisdom teeth still have eruption potential several predictors are used to determine the chance of the teeth becoming impacted. The ratio of space between the tooth crown length and the amount of space available, the angle of the teeth compared to the other teeth are the two most commonly used predictors, with the space ratio being the most accurate. Despite the capacity for movement into early adulthood, the likelihood that the tooth will become impacted can be predicted when the ratio of space available to the length of the crown of the tooth is under 1.8

Theories of impaction9:

Theories of impaction by Durbeck

1) Orthodontic theory:

Jaws develop in downward and forward direction. Growth of the jaw and movement of teeth occurs in forward direction, so any thing that interfere with such moment will cause an impaction (small jaw-decreased space). A dense bone decreases the movement of the teeth in forward direction.

2) Phylogenic theory:

Nature tries to eliminate the disused organs i.e., use makes the organ develop better, disuse causes slow regression of organ. More-functional masticatory force – better the development of the jaw Due to changing nutritional habits of our civilization, use of large powerful jaws have been practically eliminated. Thus, over centuries the mandible and maxilla decreased in size leaving insufficient room for third molars.

3) Mendeliantheory:

Heredity is most common cause. The hereditary transmission of small jaws and large teeth from parents to siblings. This may be important etiological factor in the occurrence of impaction.

4) Pathological theory:

Chronic infections affecting an individual may bring the condensation of osseous tissue further preventing the growth and development of the jaws.

5) Endocrinal theory:

Increase or decrease in growth hormone secretion may affect the size of the jaws

Complications of impaction:

If the wisdom teeth establish a communication to the mouth, pain can develop with the onset of inflammation or infection or damage to the adjacent teeth. Impacted wisdom teeth which have developed a communication to the mouth are also classified by the presence or absence of symptoms and disease. A treatment controversy exists about the necessity and timing of the removal of asymptomatic, disease-free impacted wisdom teeth. Proponents of early extraction cite the cumulative risk for extraction over time and costs of monitoring to retained wisdom teeth. Advocates for retaining wisdom teeth cite the risk and costs of unnecessary operations. Screening for the presence of the teeth is completed when signs and symptoms develop using clinical exam and radiographs. Screening typically begins in late adolescence when the probability of the partially developed tooth becoming impacted can be reliably assessed or when symptoms develop. Infection resulting from impacted wisdom teeth can be initially treated with antibiotics, local debridement or soft tissue surgery of the gingiva overlying the tooth. These treatments tend to fail over time and patients develop recurrent symptoms. The most common treatment is wisdom teeth removal, with the risks of removal being roughly proportional to the difficulty of the extraction. Sometimes, when there is a high risk to the inferior alveolar nerve, only the crown of the tooth will be removed in a procedure called a coronectomy. The long-term risk of coronectomy is that chronic infection can persist from the tooth remnants. The prognosis for the second molar is good following the wisdom teeth removal with the likelihood of post-operative bone loss increased when the extractions are completed in those 25 year of age or older.1011

Local treatment:

Where there is an operculum of gingiva overlying the tooth that has become infected it can be treated with local cleaning, an antiseptic rinse of the area and antibiotics if severe. Definitive treatment can be excision of the tissue, however, recurrence of these infections is high. Pericoronitis, while a small area of tissue should be viewed with caution, because it lies near the anatomic planes of the neck and can develop to life-threatening neck infections.

Wisdom teeth removal:

Wisdom teeth extraction is the most common treatment for impacted wisdom teeth. The absolute indications for removal are either the presence of disease or symptoms around the tooth. The procedure, depending on the depth of the impaction and angle of the tooth, is to create an incision in the mucosa of the mouth, remove bone of the mandible adjacent the tooth, section the tooth and extract it in pieces. This can be completed under local anaesthetic, sedation or general anaesthetic12.

Recovery, risks and complications:

Most patients will experience pain and swelling (worst on the first post-operative day) then return to work after 2 to 3 days with the rate of discomfort decreased to about 25% by post-operative day 7 unless affected by dry socket a disorder of wound healing that prolongs post-operative pain. It can be 4 to 6 weeks before patients are fully recovered with a full range of jaw movements. Long-term complications can include periodontal complications such as bone loss on the second molar following wisdom teeth removal. Bone loss as a complication after wisdom teeth removal is uncommon in the young but present in 43% of those of 25 years of age or older. Initiation or worsening of temporomandibular joint problems is uncommon and unpredictable. Injury to the inferior alveolar nerve resulting in numbness or partial numbness of the lower lip and chin. Other complications that are uncommon have been reported including persistent sinus communication, damage to adjacent teeth, lingual nerve injury, displaced teeth, osteomyelitis and jaw fracture13.

Coronectomy:

Coronectomy is a procedure used when the surgeon believes that there is a high risk of inferior alveolar nerve injury. After making the incision in the mucosa and removing bone adjacent the tooth, the crown is cut and removed with no attempt at removing the roots. It is indicated when there is no disease of the dental pulp or infection around the crown of the tooth and there is a high risk of inferior alveolar nerve injury. Coronectomy, while lessening the immediate risk to the inferior alveolar nerve function has its own complication rates and can result in repeated surgeries12.

Types of impaction:

Dentists use a number of terms, in combination, to describe the positioning of impacted wisdom teeth. They are mesial, distal, horizontal, vertical, soft-tissue and bony14,15.

a) Mesial, vertical, horizontal and distal:

These terms are used to refer to the general angulation (positioning) of the impacted tooth. The term "mesial" means that the tooth is angled forward, toward the front of the mouth. This is the most common type of wisdom tooth impaction. The other types of impactions, in order of frequency of occurrence, are the vertical, horizontal, and distal types. A distal impaction has an angulation that is generally directed towards the rear of the mouth. Horizontal impactions have an alignment where the tooth is lying on its side. Vertical impactions have a relatively normal orientation.

b) Soft-tissue and bony wisdom tooth impactions:

In combination with the classifications above, wisdom teeth are also categorized as soft tissue or bony impactions. A "soft tissue" impaction is one where the upper portion of a wisdom tooth (the tooth's crown) has penetrated through the bone but has not yet fully erupted through the gum tissue. The term "bony" or "hard tissue" impaction indicates that the wisdom tooth still lies primarily within the jawbone. A full-bony impaction is entirely encased by bone tissue, whereas a partial-bony one has erupted through it somewhat. Within this group, soft-tissue extractions are typically the easiest and full-bony the most difficult to perform. Related to this, the cost of a wisdom tooth extraction is typically based on its classification: soft-tissue, parietal-bony or bony.

CONCLUSION:

Wisdom teeth are the third and final set of molars that most people get in their late teens or early twenties. Partial eruption of the wisdom teeth allows an opening for bacteria to enter around the tooth and cause an infection, which results in pain, swelling, jaw stiffness, and general illness. Partially erupted teeth are also more prone to tooth decay and gum diseases because their hard-to-reach location and awkward positioning makes brushing and flossing difficult.

REFERENCES:

1. A Björk, E Jensen, M Palling - ActaOdontologica, 1956 - informahealthcare.com

2. ME Richardson - The Angle Orthodontist, 1977 - angle.org

3. American Journal of Orthodontics and Dentofacial Orthopedics, Volume 123, Issue 2, February 2003, Pages 138–145

4. International Journal of Oral and Maxillofacial Surgery, Volume 32, Issue 5, 2003, Pages 548–552

5. RG Kaplan - The Angle orthodontist, 1975 - angle.org

6. JCapelliJr - The Angle orthodontist, 1991 - angle.org

7. R Olive, K Basford - American journal of orthodontics, 1981 – Elsevier

8. Richard J. Olive and Kaye E. Basford (1981) Transverse Dento-Skeletal Relationships and Third Molar Impaction. The Angle Orthodontist: January 1981, Vol. 51, No. 1, pp. 41-47.

9. Oral Surgery, Oral Medicine, Oral Pathology, Oral Radiology, and Endodontology, Volume 79, Issue 1, January 1995, Pages 24–29

10. MY Saysel, GD Meral, İ Kocadereli, F Tasar - The Angle Orthodontist, 2005 - angle.org

11. "Wisdom tooth". Oxford English Dictionary. Oxford: Oxford University Press. 1989. ISBN 0-19-861186-2.

12. Proceedings of the National Academy of Sciences 103 (15): 5676–81. Bibcode:2006PNAS..103.5676P

13. J Oral Maxillofac Res 4 (2): e1. doi:10.5037/jomr.2013.4201

14. I Ventä - Oral surgery, oral medicine, oral pathology, 1993 – Elsevier

15. JW Glosser, JH Campbell - British journal of oral and maxillofacial surgery, 1999 – Elsevier

Received on 16.10.2014 Modified on 22.10.2014

Research J. Pharm. and Tech. 7(12): Dec. 2014; Page 1498-1500