A m andibular third m olar moved into the low er border during a period of several years. W hen the patient exp erien ced discom fort, an incisional biopsy and m arsupialization w e re perform ed. Eight m onths later, adequate bone had regenerated and the m olar and rem aining cyst structure w ere rem oved. Full-m outh and pan o ram ic radiographs w ould have allow ed the dentist to locate the missing m olar before surgery was necessary.

The case of the disappearing third molar

Lawrence J. Warner, DDS, Encino, Calif Seymour C. Morrow, DDS, Reseda, Calif I

The object of this paper is to encourage the careful scrutiny of bitewing radiographs and the utiliza­ tion of other radiographic means to visualize the entire mouth. In 1964, a patient was referred for extraction of all four impacted third molars. The mandibular and maxillary left third molars were extracted. The patient was given another appointment for the removal of the right third molars, but he failed to return. He was later seen by his general dentist and routine bitewings were taken. Radiographs taken between 1968 and 1970 showed that the mandibular right third molar “ disappeared” dur­ ing that time (Fig 1). The devious movement of the third molar was overlooked until the day the patient arrived with pain in the right zygomatic region. He had been involved in a fight resulting in a black eye. A panoramic radiograph clearly re­ vealed excursion of the mandibular right third molar. The patient was then referred for oral surgery.

Report of case The patient, a 38-year-old man, first appeared in the office in April 1975 complaining of pain and 88 ■ JADA, Vol. 96, January 1978

swelling of the right side of the mandible. The referring dentist called previously to say that he had reviewed the bitewings made during the past seven years. It was apparent that the mandibular right third molar had gradually moved toward the lower border during a period of several years. The patient had been injured in the right side of his jaw and his neck in a fight in November 1974. No other significant medical history was elicited. Oral examination showed expansion of the buccal plate in the mandibular right second and third molar areas. Radiographs showed a 10x7cm radiolucent area in the angle and ramus of the right side of the mandible (Fig 2). The radiolucent area involved 75% of the ramus and extended to the lower border and obliterated it in one area. At the lower border, near the angle, a third molar was observed. Because of the extreme destruction of the man­ dible and the presence of the tooth at the thin lower border, the treatment chosen was incisional biopsy and marsupialization. The cyst was to be completely removed after some of the bone had regenerated. With the patient under very light general anes­ thesia plus local anesthesia, the mucoperiosteum

Fig 1 ■ Radiographs taken between 1968 and 1970 show m andibular righ t third m olar “ disappearing."

on the buccal side of the right side of the mandible was incised and reflected. A window was made in the bone, a specimen of soft tissue was removed, fluid was evacuated, and the area was carefully explored. The neurovascu­ lar bundle was observed to be pushed to one side and the tooth was seen at the lower border. A previously prepared plastic button with a hole in the center was wired in place to keep the cystic area open and draining. The patient was given a syringe to irrigate the area throughout the open­ ing; the cyst would decompress, and bone would fill in at the periphery. Eight months later, the radiograph showed adequate bone had regenerated to make the man­ dible strong enough to allow removal of the molar and remaining cyst structure (Fig 3). In January 1976, the mandibular right second and third molars and the remaining cystic tissue were removed. The healing was uncomplicat­ ed. Subsequent radiographs showed the bone to be filling the cavity in a normal manner (Fig 4).

In a recent article, Friedman1 stated that the Task Force on Quality of the California Dental Association recommends that full-mouth radio­ graphs be taken every three to five years. The fact that most third party programs accept this fre­ quency (personal communication, M. J. Brom­ berg, DDS, chairman, program evaluation, Cali­ fornia Dental Association’s Council on Dental Care) should make it mandatory for dentists to use more comprehensive radiographs regularly. The ADA Council on Dental Materials and Devices, however, does not support a routine requirement of postoperative radiographs to show proof of services rendered. The Council has stated: “ The dentist’s professional judgment should determine the frequency and extent of each radiographic examination.” 2 In patients for whom extraction of third molars is indicated, it would be advantageous, in our opinion, to have all four third molars removed at

THE AUTHORS

D is c u s s io n Routine bitewings, without a complete full-mouth series, do not show the position of the third mo­ lars, to say nothing of any other bony abnor­ malities. With hindsight, it is easy to state that the disappearance of a tooth from a subsequent bitewing should have been noted. Furthermore, a radiolucent area existed distal to the second mo­ lar. Clearly, these two areas were missed. When bitewings are examined, the eye is drawn to the teeth to look for caries, overhangs, open contacts, and so forth. When the examiner is viewing a full-mouth radiographic series or a panoramic radiograph, he will see bony abnormalities in ad­ dition to restorative areas.

WARNER

Dr. W arner is in private practice and is clinical assistant professor, restorative departm ent, University of Southern C alifornia School of Den­ tistry. Dr. M orrow also is in private practice. A d­ dress requests fo r reprints to Dr. Warner, 16542 Ventura Blvd, Enclno, Calif 91436.

Warner— M orrow : DISAPPEARING THIRD MOLAR ■ 89

F ig 2 ■ R adiolucentarea 1 0x7-cm isdetected in a n g le a n d ramus of righ t side ot mandible. R adiograph was taken in 1975.

Fig 5 ■ A nother instance of third m olar starting its jo u r­ ney. Radiographs were taken d u ring an 18-month period.

Fig 3 ■ Eight m onths later adequate bone regenerated to make m andible strong enough to allow removal of m olar and rem aining cyst structure.

cient to overcome the eruptive force and a tooth may be moved apically.3 Careful examination of radiographs should result in early detection of aberrant eruption patterns for prompt treatment. If a full-mouth radiographic series with a panoramic radiograph had been taken for this pa­ tient at regular intervals, the extensive surgery and the potential for a pathologic fracture might have been avoided. Fig 5 shows a recent example of a third molar starting its journey. These radiographs were taken during an 18-month period. S u m m ary

Fig 4 ■ In January 1976 m andibular righ t second and third molars and rem aining cyst tissue were removed. Healing was norm al. Subsequent radiographs showed bone to be fillin g cavity in norm al manner.

the same appointment. Patients are reluctant to undergo surgery twice and should be encouraged to “ get it over with at one time.” The pressure of a tumor or cyst is often suffi90 ■ JADA, Vol. 96, January 1978

Full-mouth and panoramic radiographs taken at predetermined regular intervals will allow the dentist to view the entire oral bony area and make the correct diagnosis; treatment can be performed before more serious sequelae can develop. 1. Friedman, J.W. Role of radiography in dental qu ality assur­ ance. Gen Dent 24:40 June 1976. 2. Recom m endations in radiographic practices, January 1975. Council on Dental Materials and Devices, Am erican Dental Associa­ tion. JADA 90:171 Jan 1975. 3. Stafne, E.C. Oral roentgenographic diagnosis. Philadelphia. W. B. Saunders Co., 1958, p 44.

The case of the disappearing third molar.

A m andibular third m olar moved into the low er border during a period of several years. W hen the patient exp erien ced discom fort, an incisional b...
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