Case Report

Management of mandibular molar ectopic eruptionusing primary molar hemisection: case reportSupaporn Auychai, DDS, MS Robert J Feigal, DDS, PhD Paul O. Walker, DDS, MS

E ctopic eruption is the abnormal eruption of a per-manent tooth that often causes root resorption ofan adjacent primary tooth. Two types of perma-

nent first molar ectopic eruption can be distinguished.1

In the reversible type, the molar, after resorbing the dis-tal root surface of the second primary molar, becomesfree and erupts into its normal position in the dentalarch. In the irreversible type, the erupting first perma-nent molar becomes blocked by the second primarymolar, and the permanent molar remains in this lockedposition until treatment is provided or premature ex-foliation of the primary molar occurs.

The prevalence of ectopic eruption is reported to bebetween 2 and 6%,1-3 most often associated with thepermanent maxillary first molar and the mandibularlateral incisor.

Several etiologic factors have been suggested forectopic eruption of first permanent molars, includinginadequate arch length, lack of growth in the posteriorregion of the jaw, mesially inclined eruption path offirst permanent molars, and abnormally large first per-manent molars.2, ~6 The literature also suggests thatectopic eruption is an indicator of developing inad-equate arch circumference and, therefore, is likely toresult in a crowded permanent dentition. Kennedy andTurley7 suggested that patients presenting with ectopiceruption of molars require careful management.

Ectopic eruption can be diagnosed clinically onthe basis of partial or total failure to emerge.8 Patho-logic resorption of primary teeth often is noted dur-ing routine dental radiographic evaluation. 9 Themesial eruption of the permanent first molar maybe a local eruption problem or may indicate develop-mental arch circumference deficiency requiring fur-ther consideration.

A 3- to 6-month observation period is indicated af-ter early diagnosis because the molar may spontane-ously self-correct and erupt into a normal position,s Ifthe molar is prevented from erupting at the end of theobservation period, therapeutic intervention is neces-

sary. Bjerklin and KuroP stated in 1981 that if the firstpermanent molar has not fully emerged by age 7, it isunlikely that natural correction will take place. Onegoal of treatment is to move the ectopically eruptingtooth away from the tooth it is resorbing to allow thetooth to erupt into its normal position, maintaining anormal arch circumference. A secondary goal, if opti-mal position is not attained, is to allow molar eruptionin the best available vertical position with the least lossof arch circumference. Although much has been writ-ten about ectopic eruption of the maxillary first perma-nent molar, few reports mention ectopic mandibularfirst molars. YoungI reported that only three of 78 ec-topic eruptions diagnosed among 1619 schoolchildrenwere mandibular first molars, and Groper reportedmanagement of an unusual case involving a single,mandibular first permanent molar2°

This case report involves bilateral ectopic eruptionof mandibular first permanent molars treated with pri-mary molar hemisection.

Case reportA 7-year-old Caucasian female presented to the pe-

diatric dental clinic for consultation. Her medical his-tory was noncontributory and the extraoral findingswere within normal limits. Parental concern was "over-crowding, needs extraction".

A clinical oral examination showed unerupted man-dibular first permanent molars. Upon radiographicexamination, it was found that both mandibular firstpermanent molars were erupting ectopically. Extensiveresorption of the distal roots of mandibular secondprimary molars had occurred bilaterally (Figs I and 2).However, both unerupted maxillary first permanentmolars were positioned normally.

Full orthodontic records were obtained. Cephalom-etric analysis revealed the patient had a skeletal classII tendency. Arch circumference deficiency was notedin both upper and lower arches, and severe crowdingwas anticipated in the transitional dentition.

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Fig 1. Panoramic radiograph of patient at age 7 years showing the severeectopic eruption of both mandibular permanent molars.

removed distal crown segments,the distal roots having been re-sorbed previously. Due to the factthat no periapical pathology wasobserved clinically or radiographi-cally and that the crowns of thepremolar teeth appeared to be fullycalcified, we felt that there waslitt le risk of damage to anyunerupted permanent teeth in thearea involved. Primary molarbands were cemented with glassionomer cement on the remainingmesial portions of the primary sec-ond molars to guide the eruption ofthe first permanent molars.

Due to the unconventional treat-ment in this case, the patient wasfollowed on a regular, periodic ba-sis to closely observe the clinical

health of the remaining mesialhalf of each mandibular sec-ond primary molar and to ob-serve eruption of the first per-manent molars. Bite-wingradiographs were deemednecessary and were exposedat each visit. We felt that if atany time this approach wasunsuccessful, extraction andarch circumference mainte-

Fig 2. Bite-wing radiographs at age 7 years. Note the distal root nance could be institutedresorption of both mandibular second primary molars. without incurring any addi-

The treatment plan for this patient consisted of tional risk to the patient.hemisection of both mandibular second primary mo- Four months after treatment, the mandibular firstlars to allow vertical eruption of mandibular first per- permanent molars emerged. Since the mesial half ofmanent molars without furtherloss of arch circumference. Mainte-nance of arch circumference wouldbe afforded by the remaining halfof each mandibular second pri-mary molar.

At treatment, using regional in-filtration local anesthesia, bothmandibular second molars werecut halfway through the crownwith a fissure bur and then splitwith a straight elevator. Regionalinfiltration of local anesthetic wasemployed because we felt that bothmolars were nonvital and that a re-gional injection might provide he-mostasis in an area of chronic in-flammation. The distal portionsthen were removed. No patientdiscomfort was noted. Minimalbleeding occurred. Normal soft tis-sue was seen under the area of the

Fig 3. Photograph of mandibular arch 10 months post treatment showinghemisected primary molars with bands and showing successful eruption of firstpermanent molars.

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each mandibular second pri-mary molar was still intact andfree of pathology, a lingualholding arch was consideredunnecessary. Fig 3 shows thepatient at 10 months post treat-ment. No soft tissue or periapi-cal pathology was observed atthis examination. Orthodonticbands and glass ionomer ce-ment remained intact allowingfor a eruption guide plane forthe permanent molars. Fig 4shows radiographs of the areasof interest 2 years post treatment.Permanent molar position was fa-vorable and eruption of premolarswas normal. Fig 5 is a full arch pho-tograph 3 years after treatment.While the left second premolarerupted out of the ideal sequence,there continued to be no sign of pa-thology. Arch circumference wasstill inadequate for all permanentteeth, yet the patient had not lost ad-ditional arch circumference sincetreatment. Permanent molars werein a favorable vertical position.

DiscussionIn this case report, irreversible

ectopic eruption of mandibular firstpermanent molars is presented.Ectopic eruption of molars usuallyis associated with resorption of an adjacent primarytooth, frequently leads to molar impaction, andusually is associated with crowding. The patient de-scribed in this case report had all these associated clini-cal findings.

Duncan and Ashrafi1 1 reported a case of anectopically erupted mandibular first permanent molar,which was corrected by reducing the distal surface ofthe second primary molar thereby providing a clearpathway for eruption. In our case, the degree of ectopiceruption was more severe since nearly half of the man-dibular first molars were impacted and the distal rootsof the second primary molars were resorbed. We justi-fied selecting hemisection of the second primary mo-lars because orthodontic records led us to anticipate se-vere crowding and the need for further treatment.Extracting the entire second primary molar would havecaused first permanent molar migration and mesial tip-ping, leading to more space loss and unfavorable me-sial molar angulation.

Our primary goal was to allow for eruption of themandibular first permanent molars by sectioning thedistal part of the adjacent second primary molars.Bands placed on the second primary molars served as

Fig 4. Bite-wing radiographs 2 years post treatment. Note the favorable position offirst permanent molars.

Fig 5. Photograph of mandibular arch 3 years post treatment.

guides for eruption of the ectopic molars. This strategyallowed a later decision on arch circumference reduc-tion or maintenance.

The hemisection procedure performed in this casereport is similar to that described by Sanders,12 whorecommended sectioning the crown of the primarymolar, thus allowing for individual root removal whenthere is a need for modifications of routine extractiontechnique to avoid complications. For example, a he-misection is indicated when there is a close relationshipbetween the partially formed permanent premolarcrown and the roots of a mandibular first molar.

Based on clinical experience, primary molars withseverely resorbed roots often contain pulpal soft tissue,which does not react pathologically to manipulation.Due to the clinical observation of normal-appearingsoft tissue under the distal crown segment, we chosenot to perform pulp therapy. Although a pulpotomycould have been performed as a preventive measure,we felt that the additional reduction of tooth structuremight further compromise the integrity of the teeth andresult in extraction of one or both teeth. If extraction ofone or both teeth had become necessary, arch circum-ference maintenance would have been required. Due

Pediatric Dentistry - 18:5, 1996 American Academy of Pediatric Dentistry 401

to the incomplete eruption of the mandibular perma-nent first molars, one or more distal shoe appliances,followed by placement of a passive lingual holdingarch would be required. The procedures performed inthis case were done to avoid these additional treat-ments and their expense.

This report presents one treatment option for ectopicmolars. However, cases should be selected carefullysince this treatment results in arch length loss equal toabout half the width of the primary second molar. Theimportance of preventing additional arch circumfer-ence loss in some patients is highlighted by this case.If the full width of the second primary molars was lost,the patient’s arch circumference inadequacy could nothave been treated by a single premolar extraction ineach quadrant. When the relative simplicity of suchtreatment is weighed against the severity of the conse-quences of untreated cases of ectopic eruption, it canbe argued that early intervention is important to assurea normal eruption pathway while minimizing detri-mental effects on the developing occlusion.

Dr. Auychai is an instructor, department of pediatric dentistry,faculty of dentistry, Chulalongkorn University, Bangkok, Thai-land. Dr. Feigal is a professor and head of pediatric dentistry, de-partment of orthodontics and pediatric dentistry, University ofMichigan, Ann Arbor. Dr. Walker is the associate dean for clini-cal affairs and professor of pediatric dentistry, Baylor College ofDentistry, Dallas, Texas.

1. Young DH: Ectopic eruption of the first permanent molar.J Den Children 24:153-62, 1957.

2. Pulver F: The etiology and prevalence of ectopic eruptionof the maxillary first permanent molar. J Dent Child 35:138-46, 1968.

3. Bjerklin K, Kurol J: Prevalence of ectopic eruption of themaxillary first permanent molar. Swed Dent J 5:29-34,1981.

4. Bjerklin K, Kurol J: Ectopic eruption of the maxillary firstpermanent molar: etiologic factors. Am J Orthod DentofacialOrthop 84:147-55, 1983.

5. Christensen JR, Fields HW: Treatment planning and treat-ment of orthodontic problems. In: Pediatric Dentistry: In-fancy through Adolescence, JR Pinkham, Ed. Philadelphia:WB Saunders Co, 1994, pp 505-37.

6. Raghoebar GM, Boering G, Vissink A, Stegenga B: Eruptiondisturbances of permanent molars: a review. J Oral PatholMed 20:159~6, 1991.

7. Kennedy DB, Turley PK: The clinical management ofectopically erupting first permanent molars. Am J OrthodDentofacial Orthop 92:336-45, 1987.

8. van der Linden FPGM: Problems and procedures indentofacial orthopedics. London: Quintessence, 1990, pp297-300.

9. Ngan P, Wei SHY: Management of space in the primary andmixed dentitions. In: Pediatric Dentistry: Total Child Care,SHY Wei, Ed. Philadelphia: Lea & Febiger, 1988, pp 454-70.

10.Groper JN: Ectopic eruption of a mandibular first perma-nent molar: report of an unusual case. ASDC J Dent Child59:228-30, 1992.

11.Duncan WK, Ashrafi MH: Ectopic eruption of the mandibu-lar first permanent molar. J Am Dent Assoc 102:651-54,1981.

12.Sanders B: Oral and maxillofacial surgery. In: Pediatric Den-tistry, RE Stuart, TK Barber, KC Troutman, SHY Wei, Eds.St Louis: CV Mosby Co, 1981, pp 973-90.

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