Clinical follow-up study of third molar eruption from ages 20 to 26 years Irja Vent& DDS,a Heikki Murtomaa, DDS, PhD, MPH,b Lauri Turtola, DDS, PhD,C Jukka Meurman, DDS, MD, PhD,d and Pekka Ylipaavalniemi, DDS, PhD,e Helsinki, Finland UNIVERSITY
OF HELSINKI
AND FINNISH STUDENT HEALTH SERVICE
The development of 4 12 upper and lower third molars was clinically followed up for 6 years in 120 students, starting at the age of 20 years. Clinical and radiographic examinations carried out at baseline and 6 years later showed that during the follow-up period almost half the third molars originally recorded partially erupted had erupted. When the lower third molars were initially invisible, only 9% of them had erupted by age 26 years whereas 29% remained invisible. When third molars had been already erupted baseline, only a few were extracted during the g-year follow-up period. It was concluded that a certain proportion of third molars erupt relatively late, and therefore the need for surgical interventions may decrease with age during early adulthood. (ORALSURG ORAL MEDORAL PATHOL 1991;72:150-3)
0
ne of the most common surgical interventions in young adults is the removal of the third molars (wisdom tooth). The peak age for surgery is soon after 20 years, because many of the possible problems arise together with eruption or impaction. The literature currently offers only a few longitudinal studies on the development of third molars among young adults. Several studiesle4 have discussed radiographically detected changes in development of third molars during childhood and adolescence. A clinical 4-year follow-up study of students aged 20 to 24 years was carried out by von Wowern and Nielsen5 who concluded that third molars continue to erupt after the age of 20 years and therefore the treatment of choice seems to be observation rather than prophylactic removal. However, Garcia and Chauncey,6 in their lo-year study of men more than 25 years old, reported few erupting and subsequently functioning third molars.
aInstructor, Department of Oral and Maxillofacial Surgery, versity of Helsinki. bAssociate Professor, Department of Dental Public Health, versity of Helsinki. CChief Dental Officer, Finnish Student Health Service. dAssistant Professor, Department of Cariology, University of sinki. CAssistant Professor, Department of Oral and Maxillofacial gery, University of Helsinki. 7/12/23832 150
UniUniHelSur-
as at
I. Distribution of third molars at age 26 years when bicuspid or another molar was missing in same quarter of dental arch (n = 22)
Table
18
4
IO
0
0
0
1
0
1
1 1
1 (3) 3 (8) 1 (3) 3 (8) 18 (46) 13m (100)
Total No. of teeth Third molar status (No. of teeth)
7
Invisible Partially erupted Erupted Occlusal surface Partial crown Complete crown Missing
0
1
0
0
0 4 2
I 10 6
0 2 1
2 2 4
39
The aim of the present study was to follow the course of clinical development of third molars, particularly after the mean age (i.e., 19.5 to 20.5 years’) of eruption. The main purpose was to investigate how many of the invisible or partially erupted third molars diagnosed at the age of 20 years erupt by the age of 26 years. MATERIAL AND METHODS
The study was carried out at the Finnish Student Health Service in Helsinki. All first-year students at
Follow-up
Volume 72 Number 2
of third molar eruption
151
50%1
‘NV’S’BLE
PARTIALLY ERUPTED
ERUPTED
REMOVED
‘NV’S’BLE
PARTIALLY ERUPTED
ERUPTED
REMOVED
20% 30% 40% -
MANDiBLE
I
50% ’
2. Status of initially partially erupted third molars (16 in maxilla, 45 in mandible) 6 years after baseline.
Fig.
1. Status of initially invisible third molars (74 teeth in maxilla, 90 in mandible) 6 years after baseline examination.
Fig.
Table
II. Cross-sectional data of distribution
of third molars studied at ages 20 and 26 years (n = 98)
Maxilla
Mandible
20 yr
Total Third
No. of teeth molar status
Invisible Partially erupted Erupted Occlusal surface Partial crown Complete crown Missing/removed Total
26 yr
Total
20 yr
26 yr
20 yr
26 yr
M
F
64
132
64
132
64
132
64
132
392
392
33 9
41 8
8 5
6 6
31 26
52 21
8 9
16 10
42 15
10 8
3 19 25 11 100
4 8 23 16 100
0 3 50 34 100
2 4 31 51 100
2 5 19 17 100
3 5 5
2 8 26 47 100
3 5 17 49 100
3 8 17 15 100
2 5 28 47 100
M
F
M
F
M
F
(%)
the University of Helsinki during the 1981-1982 school year who were born in Helsinki in 196 1 or 1962 and also living in Helsinki were invited to a free dental examination. Those students who participated at baseline were then reinvited 6 years later. A total of 123 students (39 men, 84 women) participated in both
14 100
the first and the second examinations; response rates were 73% and 68%, respectively. Findings at baseline were published previously as a cross-sectional study.* The final number of participants was 120 (38 men, 82 women); three of the subjects were omitted in the
Ventii et al.
152
ORAL. SCIRG OR,U
MED ORAL PATH~L August 199 I
as histograms. The differences between quantities were tested by use of the chi-square test.
100%
MAXILLA
RESULTS
INVISIBLE
PARTIALLY ERUPTED
ERUPTED
REMOVED
3. Status of initially erupted third molars (76 in maxilla, 33 in mandible) 6 years after baseline.
Fig.
analysis because their initial radiographs were unavailable. The average (+- SD) age of the students was 20.3 ? 0.58 years at the baseline and 26.7 + 0.57 after 6 years. Clinical recordings of the third molars were made at the ages of 20 and 26 years, but panoramic tomograms were taken only at 20 years. At 26 years of age such x-ray films were taken only when necessary (30 cases), that is, when the eruption status of a third molar could not be determined otherwise. Restrictions on x-rays were based on ethical considerations. The clinical status of third molars was recorded according to the following criteria: invisible, if a tooth had not yet perforated the oral mucosa; partially erupted, if the occlusal surface was partially visible; erupted, if (1) the occlusal surface was completely visible, (2) the crown was partially visible, or (3) the crown was completely visible. Missing third molars were verified from the x-ray films. Notes concerning missing premolars and other molars were included in the records. The clinical examinations were carried out by three of the authors (H.M., L.T., J.M.). The radiographs were examined for missing teeth by the first author. The results of this descriptive study are presented
At the age of 26 years, 22 subjects (6 men, 16 women) had one or more bicuspids, first molars, or second molars missing (Table I). The particular tooth missing alleviated the eruption of a third molar in the same quarter of the dental arch. In this subgroup 57% of the third molars had erupted, whereas in the rest of the main group, only 35% had erupted (p < 0.01). To eliminate this effect of incomplete dentition on the rest of the results, these 22 subjects were analyzed separately from the main group. The main group consisted of 98 students (32 men, 66 women). Initially they had 334 third molars in their dental arches. The cross-sectional data in Table II show that at baseline partially erupted third molars were encountered more often in the mandible than in the maxilla @ < 0.005 for women). At both baseline and 6 years later, upper third molars were more often erupted than lower ones (at baseline, p < 0.001 for women). The main difference in results between men and women was that at baseline lower third molars were invisible more often in women than in men (52% vs 31%, p < 0.01). The follow-up results showed that those third molars which were initially totally invisible erupted more often in the maxilla than in the mandible (p < 0.001) (Fig. 1). During the follow-up period almost half the originally partially erupted third molars erupted (Fig. 2). Of the initially invisible or only partly erupted third molars, the total number of erupted third molars during the follow-up period was 57 teeth (29 in the maxilla, 28 in the mandible). Fig. 3 shows that of those teeth which had been totally erupted at baseline, only a few were extracted during the 6-year follow-up. DISCUSSION
Because of the scarcity of longitudinal epidemiologic data, clinical decisions concerning third molar surgery have been based on case reports, clinical experience, and cross-sectional studies. From the crosssectional data in Table II, one is tempted to deduce that the difference between the total quantity of erupted teeth at ages 20 and 26 years was only 7% (27 teeth). However, the corresponding longitudinal data showed that the number of erupting teeth during the follow-up was more than twice that much (57 teeth). At an individual level, information obtained from longitudinal studies thus seems more accurate and offers a wider basis for clinical decisions. In addition, during the study one third of all third molars were removed. Because some teeth were
Follow-up of third molar eruption
Volume 72 Number 2
extracted after eruption, the total number of erupting third molars during the 6 years was in fact larger than that shown in Figs. 1 and 2. During the follow-up the number of erupting third molars was 17% of the total number of third molars, which conforms well with the 19% reported by von Wowern and Nielsen.’ The number of initially missing third molars (15%) in the present study was about the same as reported earlier; namely 13%7 and 1 1%.9 The present study agrees with previous studies’+ lo, 1’ that the prevalence of third molar impaction is reduced if a premolar, first molar, or second molar is missing. According to the cross-sectional analysis in the present study, the percentage of erupted third molars (28% at age 20 years and 35% at 26 years) was somewhat lower than that in previous studies; namely 46%’ and 42% at age 20 years, and 68%9 at age 30 years. This difference may be affected by the fact that the sample of Bjijrk et al.’ consisted only of men and that patients with incomplete dentition were not excluded in the study of Hugoson and Kugelberg.9 In adults conventional extraction of erupted third molars by forceps usually requires less time and produces less morbidity than a surgical removal.12 On the other hand, surgical removal of a fully developed impacted tooth from an adult patient may result in more morbidity than the removal of a partially developed impacted tooth from a younger patient. The results of our study suggest that a certain proportion of impacted and partially erupted third molars erupt relatively late and that the need for surgical interventions may therefore decrease with age during early adulthood. It seems justified to postpone the decision on third molar removal until information on the development of the particular tooth is clearer,
153
provided that the patient is asymptomatic, that no signs of pathology are present or probable, and that no overriding oral health indications are present. REFERENCES
1. Bjijrk A, Jensen E, Palling M. Mandibular growth and third molar impaction. Acta Odontol Stand 1956;14:23 l-72. 2. Richardson M. The development of third molar impaction. Br J Orthod 1975;2:231-4. 3. Shiller W. Positional changes in mesio-angular impacted mandibular third molars during a year. J Am Dent Assoc 1979;99:460-4. 4. Richardson E, Malhotra S, Semenya K. Longitudinal study of three views of mandibular third molar eruption in males. Am J Orthod 1984;86: 119-29. 5. von Wowern N, Nielsen H. The fate of impacted lower third molars after the age of 20. Int J Oral Maxillofac Surg 1989;18:277-80. 6. Garcia R, Chauncey H. The eruption of third molars in adults: a IO-year longitudinal study. ORAL SURG ORAL MED ORAL PATHOL 1989;68:9-13. 7. Rantanen A. The age of eruption of the third molar teeth. Acta Odontol Stand 1967;25(suppI 48):1-86. 8. Murtomaa H, Turtola L, Ylipaavalniemi P, Rytomaa I. Status of the third molars in the 20- to 21-year-old Finnish university population. J Am Co11 Health 1985;34: 127-9. 9. Hugoson A, Kugelberg C. The prevalence of third molars in a Swedish population: an epidemiological study. Community Dent Health 1988;5:121-38. 10. Richardson M. The etiology and prediction of mandibular third molar impaction. Angle Orthod 1977;47: 165-72. 11. Haavikko K, Altonen M, Mattila K. Predicting angulational development and eruption of the lower third molar. Angle Orthod 1978;48:39-48. 12. Van Gool A, Ten Bosh J, Boering G. Clinical consequences of complaints and complications after removal of the mandibular third molar. Int J Oral Surg 1977;6:29-37. Reprint
requests:
Irja Venta, DDS Department of Oral and Maxillofacial University of Helsinki Mannerheimintie 172 00280 Helsinki, Finland
Surgery
OF HELSINKI
AND FINNISH STUDENT HEALTH SERVICE
The development of 4 12 upper and lower third molars was clinically followed up for 6 years in 120 students, starting at the age of 20 years. Clinical and radiographic examinations carried out at baseline and 6 years later showed that during the follow-up period almost half the third molars originally recorded partially erupted had erupted. When the lower third molars were initially invisible, only 9% of them had erupted by age 26 years whereas 29% remained invisible. When third molars had been already erupted baseline, only a few were extracted during the g-year follow-up period. It was concluded that a certain proportion of third molars erupt relatively late, and therefore the need for surgical interventions may decrease with age during early adulthood. (ORALSURG ORAL MEDORAL PATHOL 1991;72:150-3)
0
ne of the most common surgical interventions in young adults is the removal of the third molars (wisdom tooth). The peak age for surgery is soon after 20 years, because many of the possible problems arise together with eruption or impaction. The literature currently offers only a few longitudinal studies on the development of third molars among young adults. Several studiesle4 have discussed radiographically detected changes in development of third molars during childhood and adolescence. A clinical 4-year follow-up study of students aged 20 to 24 years was carried out by von Wowern and Nielsen5 who concluded that third molars continue to erupt after the age of 20 years and therefore the treatment of choice seems to be observation rather than prophylactic removal. However, Garcia and Chauncey,6 in their lo-year study of men more than 25 years old, reported few erupting and subsequently functioning third molars.
aInstructor, Department of Oral and Maxillofacial Surgery, versity of Helsinki. bAssociate Professor, Department of Dental Public Health, versity of Helsinki. CChief Dental Officer, Finnish Student Health Service. dAssistant Professor, Department of Cariology, University of sinki. CAssistant Professor, Department of Oral and Maxillofacial gery, University of Helsinki. 7/12/23832 150
UniUniHelSur-
as at
I. Distribution of third molars at age 26 years when bicuspid or another molar was missing in same quarter of dental arch (n = 22)
Table
18
4
IO
0
0
0
1
0
1
1 1
1 (3) 3 (8) 1 (3) 3 (8) 18 (46) 13m (100)
Total No. of teeth Third molar status (No. of teeth)
7
Invisible Partially erupted Erupted Occlusal surface Partial crown Complete crown Missing
0
1
0
0
0 4 2
I 10 6
0 2 1
2 2 4
39
The aim of the present study was to follow the course of clinical development of third molars, particularly after the mean age (i.e., 19.5 to 20.5 years’) of eruption. The main purpose was to investigate how many of the invisible or partially erupted third molars diagnosed at the age of 20 years erupt by the age of 26 years. MATERIAL AND METHODS
The study was carried out at the Finnish Student Health Service in Helsinki. All first-year students at
Follow-up
Volume 72 Number 2
of third molar eruption
151
50%1
‘NV’S’BLE
PARTIALLY ERUPTED
ERUPTED
REMOVED
‘NV’S’BLE
PARTIALLY ERUPTED
ERUPTED
REMOVED
20% 30% 40% -
MANDiBLE
I
50% ’
2. Status of initially partially erupted third molars (16 in maxilla, 45 in mandible) 6 years after baseline.
Fig.
1. Status of initially invisible third molars (74 teeth in maxilla, 90 in mandible) 6 years after baseline examination.
Fig.
Table
II. Cross-sectional data of distribution
of third molars studied at ages 20 and 26 years (n = 98)
Maxilla
Mandible
20 yr
Total Third
No. of teeth molar status
Invisible Partially erupted Erupted Occlusal surface Partial crown Complete crown Missing/removed Total
26 yr
Total
20 yr
26 yr
20 yr
26 yr
M
F
64
132
64
132
64
132
64
132
392
392
33 9
41 8
8 5
6 6
31 26
52 21
8 9
16 10
42 15
10 8
3 19 25 11 100
4 8 23 16 100
0 3 50 34 100
2 4 31 51 100
2 5 19 17 100
3 5 5
2 8 26 47 100
3 5 17 49 100
3 8 17 15 100
2 5 28 47 100
M
F
M
F
M
F
(%)
the University of Helsinki during the 1981-1982 school year who were born in Helsinki in 196 1 or 1962 and also living in Helsinki were invited to a free dental examination. Those students who participated at baseline were then reinvited 6 years later. A total of 123 students (39 men, 84 women) participated in both
14 100
the first and the second examinations; response rates were 73% and 68%, respectively. Findings at baseline were published previously as a cross-sectional study.* The final number of participants was 120 (38 men, 82 women); three of the subjects were omitted in the
Ventii et al.
152
ORAL. SCIRG OR,U
MED ORAL PATH~L August 199 I
as histograms. The differences between quantities were tested by use of the chi-square test.
100%
MAXILLA
RESULTS
INVISIBLE
PARTIALLY ERUPTED
ERUPTED
REMOVED
3. Status of initially erupted third molars (76 in maxilla, 33 in mandible) 6 years after baseline.
Fig.
analysis because their initial radiographs were unavailable. The average (+- SD) age of the students was 20.3 ? 0.58 years at the baseline and 26.7 + 0.57 after 6 years. Clinical recordings of the third molars were made at the ages of 20 and 26 years, but panoramic tomograms were taken only at 20 years. At 26 years of age such x-ray films were taken only when necessary (30 cases), that is, when the eruption status of a third molar could not be determined otherwise. Restrictions on x-rays were based on ethical considerations. The clinical status of third molars was recorded according to the following criteria: invisible, if a tooth had not yet perforated the oral mucosa; partially erupted, if the occlusal surface was partially visible; erupted, if (1) the occlusal surface was completely visible, (2) the crown was partially visible, or (3) the crown was completely visible. Missing third molars were verified from the x-ray films. Notes concerning missing premolars and other molars were included in the records. The clinical examinations were carried out by three of the authors (H.M., L.T., J.M.). The radiographs were examined for missing teeth by the first author. The results of this descriptive study are presented
At the age of 26 years, 22 subjects (6 men, 16 women) had one or more bicuspids, first molars, or second molars missing (Table I). The particular tooth missing alleviated the eruption of a third molar in the same quarter of the dental arch. In this subgroup 57% of the third molars had erupted, whereas in the rest of the main group, only 35% had erupted (p < 0.01). To eliminate this effect of incomplete dentition on the rest of the results, these 22 subjects were analyzed separately from the main group. The main group consisted of 98 students (32 men, 66 women). Initially they had 334 third molars in their dental arches. The cross-sectional data in Table II show that at baseline partially erupted third molars were encountered more often in the mandible than in the maxilla @ < 0.005 for women). At both baseline and 6 years later, upper third molars were more often erupted than lower ones (at baseline, p < 0.001 for women). The main difference in results between men and women was that at baseline lower third molars were invisible more often in women than in men (52% vs 31%, p < 0.01). The follow-up results showed that those third molars which were initially totally invisible erupted more often in the maxilla than in the mandible (p < 0.001) (Fig. 1). During the follow-up period almost half the originally partially erupted third molars erupted (Fig. 2). Of the initially invisible or only partly erupted third molars, the total number of erupted third molars during the follow-up period was 57 teeth (29 in the maxilla, 28 in the mandible). Fig. 3 shows that of those teeth which had been totally erupted at baseline, only a few were extracted during the 6-year follow-up. DISCUSSION
Because of the scarcity of longitudinal epidemiologic data, clinical decisions concerning third molar surgery have been based on case reports, clinical experience, and cross-sectional studies. From the crosssectional data in Table II, one is tempted to deduce that the difference between the total quantity of erupted teeth at ages 20 and 26 years was only 7% (27 teeth). However, the corresponding longitudinal data showed that the number of erupting teeth during the follow-up was more than twice that much (57 teeth). At an individual level, information obtained from longitudinal studies thus seems more accurate and offers a wider basis for clinical decisions. In addition, during the study one third of all third molars were removed. Because some teeth were
Follow-up of third molar eruption
Volume 72 Number 2
extracted after eruption, the total number of erupting third molars during the 6 years was in fact larger than that shown in Figs. 1 and 2. During the follow-up the number of erupting third molars was 17% of the total number of third molars, which conforms well with the 19% reported by von Wowern and Nielsen.’ The number of initially missing third molars (15%) in the present study was about the same as reported earlier; namely 13%7 and 1 1%.9 The present study agrees with previous studies’+ lo, 1’ that the prevalence of third molar impaction is reduced if a premolar, first molar, or second molar is missing. According to the cross-sectional analysis in the present study, the percentage of erupted third molars (28% at age 20 years and 35% at 26 years) was somewhat lower than that in previous studies; namely 46%’ and 42% at age 20 years, and 68%9 at age 30 years. This difference may be affected by the fact that the sample of Bjijrk et al.’ consisted only of men and that patients with incomplete dentition were not excluded in the study of Hugoson and Kugelberg.9 In adults conventional extraction of erupted third molars by forceps usually requires less time and produces less morbidity than a surgical removal.12 On the other hand, surgical removal of a fully developed impacted tooth from an adult patient may result in more morbidity than the removal of a partially developed impacted tooth from a younger patient. The results of our study suggest that a certain proportion of impacted and partially erupted third molars erupt relatively late and that the need for surgical interventions may therefore decrease with age during early adulthood. It seems justified to postpone the decision on third molar removal until information on the development of the particular tooth is clearer,
153
provided that the patient is asymptomatic, that no signs of pathology are present or probable, and that no overriding oral health indications are present. REFERENCES
1. Bjijrk A, Jensen E, Palling M. Mandibular growth and third molar impaction. Acta Odontol Stand 1956;14:23 l-72. 2. Richardson M. The development of third molar impaction. Br J Orthod 1975;2:231-4. 3. Shiller W. Positional changes in mesio-angular impacted mandibular third molars during a year. J Am Dent Assoc 1979;99:460-4. 4. Richardson E, Malhotra S, Semenya K. Longitudinal study of three views of mandibular third molar eruption in males. Am J Orthod 1984;86: 119-29. 5. von Wowern N, Nielsen H. The fate of impacted lower third molars after the age of 20. Int J Oral Maxillofac Surg 1989;18:277-80. 6. Garcia R, Chauncey H. The eruption of third molars in adults: a IO-year longitudinal study. ORAL SURG ORAL MED ORAL PATHOL 1989;68:9-13. 7. Rantanen A. The age of eruption of the third molar teeth. Acta Odontol Stand 1967;25(suppI 48):1-86. 8. Murtomaa H, Turtola L, Ylipaavalniemi P, Rytomaa I. Status of the third molars in the 20- to 21-year-old Finnish university population. J Am Co11 Health 1985;34: 127-9. 9. Hugoson A, Kugelberg C. The prevalence of third molars in a Swedish population: an epidemiological study. Community Dent Health 1988;5:121-38. 10. Richardson M. The etiology and prediction of mandibular third molar impaction. Angle Orthod 1977;47: 165-72. 11. Haavikko K, Altonen M, Mattila K. Predicting angulational development and eruption of the lower third molar. Angle Orthod 1978;48:39-48. 12. Van Gool A, Ten Bosh J, Boering G. Clinical consequences of complaints and complications after removal of the mandibular third molar. Int J Oral Surg 1977;6:29-37. Reprint
requests:
Irja Venta, DDS Department of Oral and Maxillofacial University of Helsinki Mannerheimintie 172 00280 Helsinki, Finland
Surgery
