ABSTRACT
Objectives: To study the pattern and management of hypodontia in the permanent dentition,
excluding the third molars, in a sample of Jordanian orthodontic patients.
Methods: A total of 1200 orthodontic patients (600 females and
600 males) was examined for evidence of hypodontia at Prince Rashid
Ben Al-
Hassan Hospital
during the period between July 2008 and September 2010. Intraoral examination,
pre treatment records, and orthopantomographic study were used for the
diagnosis of tooth agenesis. Our study group comprised 116 non-syndromic
hypodontic patients (74 females and 42 males), with an age range of 10-25 years
(mean age 17 years 8 months).
Results: A hypodontia prevalence of 9.7% was found
for the total study group (6.2% for females and 3.5% for males) with a
statistically significant difference between both gender (P<0.05). The
most frequently missing teeth were the maxillary lateral incisors (41.1%),
followed by the mandibular second premolars (28.5%). Hypodontia was found more
often in the maxilla (62%) and symmetrical hypodontia was predominant.
Most patients (82.8%) had hypodontia of one or two teeth, whereas oligodontia
was found in 3.5%.
Conclusions: Accurate diagnosis of hypodontia is the key to
orthodontic treatment planning and eventual treatment itself. Furthermore,
additional knowledge of dental development will contribute valuable insights
for novel therapeutic regiments in the future so that we can move from a mode
of diagnosis and treatment to one of prediction and prevention.
Key words: Hypodontia,
Oligodontia, Orthopantomographic study, Pretreatment records
JRMS September 2013; 20(2): 51-55 / DOI: 10.12816/0001041
Introduction
Tooth agenesis or hypodontia, is the most common human malformation with
widely varying frequencies from (2.6% to 11.3%), excluding third molars. The
prevalence of hypodontia among different ethnic participants in the same population
was estimated to be 4.8%, with a higher incidence in females than in males.(1)
Hypodontia is often used as a collective term for congenital absence of
primary or secondary teeth, although specifically it describes the absence of
one to six teeth excluding third molars. Oligodontia refers to the absence of
more than six teeth, excluding third molars, while anodontia represents the
loss of all teeth.(2) Although it is not a serious public
health problem, hypodontia may cause masticatory and speech dysfunctions and
create esthetic problems with orthodontic and prosthetic implications.(3) Hypodontia has a multifactorial aetiology involving
genetic, epigenetic and environmental factors. Recent advances in genetic
research have focused on transcription factors, particularly MSX1, PAX9, and
AXIN2 in families with multiple dental agenesis. The condition may appear as
syndromic, in which tooth agenesis is a regular feature in conjunction with
other congenital anomalies, or nonsyndromic, encountered in healthy, apparently
normal people as a primary condition.(3,4) Hypodontia is
frequently associated with other dental anomalies,(1,4-6) and recently, a statistical
association between hypodontia and epithelial ovarian cancer was observed, that
warrants further investigation.(7)
Methods
The subjects of
the present study were 116 non-syndromic hypodontic patients, 74 females and 42
males (ages 10-25 years, the mean age was 17 years 8 months), were diagnosed
from a total sample of 1200
orthodontic patients (600 females and 600 males), at Prince Rashid ben Al- Hassan hospital during the
period between July 2008 and September 2010. The study protocol for our study
was approved by the Human Research Ethics Committee at the Royal Medical
Services. Detailed medical history, intraoral examination, panoramic
radiographs and pretreatment records were used for identification and recording
permanent tooth agenesis (excluding third molars). Exclusion criteria included:
previous orthodontic treatment, head or neck trauma, head or neck surgery,
history of craniofacial disorder, and previous loss of teeth due to accidents,
extraction or other contributing causes.
Chi- square test was used to investigate the difference in the
prevalence and distribution of hypodontia between genders. The data were
analyzed using SPSS software version 17 for statistical analysis (Statistical
Package for Social Sciences, SPSS Inc., Chicago,
Illinois, USA),
the level of significance tested was (P < 0.05).
Results
Of 1200 examined orthodontic patients, 116 (74 females and 42 males) demonstrated an agenesis of one or more teeth. The
116 hypodontic patients comprised 74 (63.8%) females and 42 (36.2%) males. The
prevalence of hypodontia was 9.7% (6.2% for females and 3.5% for males) for
this sample of Jordanian orthodontic patients, with a statistically significant
difference in gender (P = 0.0018). The distribution of patients by gender is
shown in Table I.
Table II, shows a total of 253 permanent teeth were
missing. Agenesis of maxillary lateral incisors was observed in 104 patients
(41.1%), 55 on the left side (52.9%) and 49 on the right side (47.1%), 68
females (58.62%) and 36 males (31%). Unilateral
and bilateral location was almost equally represented. Agenesis of second
premolars was observed in 95 patients (37.5%), of which 23 (24.2%) were missing
from the maxilla and 72 (75.8%) from the mandible. Agenesis of all four second
premolars was observed in eight patients (9.89 %). In addition, 18 upper
canines, 15 lower central incisors, six upper first premolars, four lower
lateral incisors and two lower second molars were identified as missing. Most
missing teeth (62%) were in the maxilla.
The majority of patients (82.8%) were missing one or two teeth
while oligodontia was found in
3.5% (Table III). In total, 130 (51.38%) teeth were absent on the left side and 123
(48.62%) on the right
side. Table IV, shows the
relationship between Angle’s classification of malocclusion and the number of
missing teeth. Patients with more severe hypodontia showed a tendency to a
Class III relationship. The space was orthodontically closed in 84.5% of the patients, while in the other 15.5% the space was maintained (Table V).
Discussion
Hypodontia of permanent teeth was found in 116 patients (74 females and 42 males) from a total sample of 1200
orthodontic patients. The present study revealed a hypodontia prevalence of 6.2%
for females, 3.5% for males, and 9.7% for both genders combined, excluding third molars.
A hypodontia present in 9.7% for orthodontic patients is higher than the 4.8% reported
by Küchler et al. for
a normal population with a wide ethnic variation,(1) and corresponds to the values 6.5%, 7.54%,
8.5%, 9.11%, 11.3% reported for orthodontic patients in Spain, Turkey, Japan, Iran,
Slovenia, respectively.(8-12) Extraordinarily, a hypodontia present in 9.4% in permanent teeth of Japanese pediatric patients (not orthodontic sample) was reported by Goyaet al. which confirms that hypodontia is common in Japanese.(13) Several authors report a little but not significant predominance of hypodontia in females.(1,8,10,12) Sisman et al. reported a higher female hypodontia prevalence with statistically significant differences in gender for the tooth number ≠ “14”, “12” and “11” (≠ Federation Dentaire International Notation).(9) However, our study revealed the prevalence of hypodontia was higher in females (6.2 %) than in males (3.5 %) defining the ratio male: female at 1 : 1.76 with a statistically significant difference in gender (P < 0.05). In our study most (82.75%) people with hypodontia were missing just 1 or 2 teeth (51.7% for females, 31% for males). The average number of missing teeth per subject was 2.2. These findings coincided with previous studies.(1,9,10,12)
Table I: Distribution of the
study participants by gender
|
Total n(% )
|
Patients without hypodontia n(% )
|
Patients with hypodontia n( % )
|
Gender
|
|
600 (50)
|
558
(46.5)
|
42 (3.5)
|
Male
|
|
600 (50)
|
526
(43.8)
|
74 (6.2)
|
Female
|
|
1200 (100)
|
1084
(90.3)
|
116
(9.7)
|
Total
|
Table II: Distribution of
hypodontia by tooth number ≠
|
Total n (%)
|
Female n (%)
|
Male n (%)
|
Tooth number ≠
|
|
2 (0.79)
|
2 (0.79)
|
0
|
11
|
|
49 (19.37)
|
32
(12.64)
|
17
(6.72)
|
12
|
|
9 (3.56)
|
8 (3.16)
|
1 (0.39)
|
13
|
|
3 (1.18)
|
1 (0.39)
|
2 (0.79)
|
14
|
|
11 (4.35)
|
8 (3.16)
|
3 (1.18)
|
15
|
|
1 (0.39)
|
0
|
1 (0.39)
|
16
|
|
1 (0.39)
|
1 (0.39)
|
0
|
17
|
|
1 (0.39)
|
1 (0.39)
|
0
|
21
|
|
55 (21.74)
|
36
(14.23)
|
19
(7.50)
|
22
|
|
9 (3.56)
|
7 (2.77)
|
2 (0.79)
|
23
|
|
3 (1.18)
|
1 (0.39)
|
2 (0.79)
|
24
|
|
12 (4.74)
|
9 (3.56)
|
3 (1.18)
|
25
|
|
1 (0.39)
|
1 (0.39)
|
0
|
27
|
|
7 (2.77)
|
4 (1.58)
|
3 (1.18)
|
31
|
|
2 (0.79)
|
2 (0.79)
|
0
|
32
|
|
1 (0.39)
|
1 (0.39)
|
0
|
33
|
|
38 (15.02)
|
24
(9.48)
|
14
(5.53)
|
35
|
|
1 (0.39)
|
1 (0.39)
|
0
|
37
|
|
8 (3.16)
|
5 (1.98)
|
3 (1.18)
|
41
|
|
2 (0.79)
|
0
|
2 (0.79)
|
42
|
|
2 (0.79)
|
1 (0.39)
|
1 (0.39)
|
43
|
|
34 (13.44)
|
22 (8.7)
|
12
(4.74)
|
45
|
|
1 (0.39)
|
1 (0.39)
|
0
|
47
|
|
253 (100)
|
168 (66.4)
|
85 (33.6)
|
Total
|
≠ Federation
Dentaire International Notation
Table III: Distribution of the
patients by gender and number of missing teeth
|
Total
n (%)
|
More than four teeth
n (%)
|
Four teeth
n (%)
|
Three teeth
n (%)
|
Two teeth
n (%)
|
One tooth
n (%)
|
|
|
42 (36.20)
|
1 (0.86)
|
3 (2.59)
|
2 (1.72)
|
19
(16.37)
|
17
(14.65)
|
Male
|
|
74 (63.79)
|
3 (2.59)
|
6 (5.17)
|
5 (4.31)
|
38
(32.75)
|
22
(18.96)
|
Female
|
|
116 (100)
|
4 (3.49)
|
9 (7.76)
|
7 (6.03)
|
57
(49.14)
|
39
(33.62)
|
Total
|
Table IV: Relationship
between the number of missing teeth and Angle’s classification
|
Total
n (%)
|
More than four teeth
n (%)
|
Four teeth
n (%)
|
Three teeth
n (%)
|
Two teeth
n (%)
|
One tooth
n (%)
|
Angle’s classification
|
|
73 (63.79)
|
1 (0.86)
|
4 (3.49)
|
4 (3.49)
|
35
(30.17)
|
29 (25)
|
Cl I
|
|
22 (18.96)
|
0
|
3 (2.59)
|
1 (0.86)
|
12
(10.34)
|
6 (5.17)
|
Cl II
|
|
21 (18.10)
|
3 (2.59)
|
2 (1.78)
|
2 (1.78)
|
10
(8.62)
|
4 (3.49)
|
Cl III
|
Table V: Distribution of
orthodontic treatment option
|
Total n (%)
|
Space closure n (%)
|
Space opening n (%)
|
|
|
42 (36.21)
|
30
(25.86)
|
12
(10.34)
|
Male
|
|
74 (63.79)
|
68
(58.62)
|
6 (5.17)
|
Female
|
|
116 (100)
|
98
(84.48)
|
18
(15.52)
|
Total
|
The distribution of hypodontia by tooth number indicates a significantly
higher incidence of missing maxillary lateral incisors. In our study, the most
frequently missing tooth was the maxillary lateral incisor that accorded with
the findings of previous studies,(9,11,12,14) followed by the mandibular second premolars (28.5%). Hypodontia of the maxillary lateral incisors
was observed in (41.1%) of the total sample, however, this incidence
is significantly higher than that reported in previous studies. In contrast
with our findings, the most commonly missing teeth were the lower second
premolars, reported in many previous studies (excluding third molars).(1,8,10,15) The two basic orthodontic options
for treating patients with congenitally absent maxillary lateral incisors were
space opening to replace the missing tooth or space closure and substitute the
canine for the missing lateral incisor. The need to maintain space until the
end of growth for a permanent restoration is undesirable. Space closure is
definitely a more attractive solution in adolescent patients because of the
permanence of the finished result.
However, treatment decisions should depend on the basic orthodontic
diagnosis. Arch-length deficiency, facial profile, the existing malocclusion,
and the size and esthetics of the canine must all be evaluated. Agenesis of
second premolars would have a risk of anchorage loss, as it might alter the
treatment planning and modify the mechanotherapy as well. Often this anomaly is
associated with retained and infraoccluded primary molars and with clinical
sequelae, such as reduced alveolar height, supraeruption of opposing teeth,
tipping of first molars with space loss, and, in some cases, impaction of the
first premolar. Treatment considerations for congenitally absent mandibular
second premolars depend on the patient’s age, the stage of development of the
adjacent teeth, and the condition of the deciduous predecessors with regard to
root resorption and infraocclusion. Some early decisions that the orthodontist
makes for a patient whose mandibular second premolars are congenitally missing will affect his / her dental health for a
lifetime. Therefore, the correct decision must be made at the appropriate time.
In our study, hypodontia was found more often in the maxilla (62%), in
agreement with previous studies,(9,11,12) with a remarkable similarity
in the distribution of missing teeth between the left and right sides (51.38
and 48.62 %) respectively.(9,10) Most individuals with oligodontia (75%) demonstrated
a tendency to Angle’s Class III malocclusion and Class III skeletal
relationship, consistent with the results of previous studies.(11,12,16) Elimination of the
arch length imbalance caused by congenitally missing teeth necessitates
formation of a comprehensive treatment plan which considers the possibility of
orthodontic space closure and/or a prosthetic restoration. In the present
study, in order to improve the scheme of the occlusion and to avoid any
detrimental alterations to the occlusion and the facial profile, the space was
orthodontically closed in (84.5%) of the patients, while in the other (15.5%)
the space was maintained for an eventual restoration. The keys during
orthodontic treatment are to create the correct amount of space and to leave
the alveolar ridge in an ideal condition for a future restoration. There are
other treatment options, like, osseointegrated implant or autotransplantation
of a tooth. In a growing child, osseointegrated implants cannot adapt to growth
and developmental changes in the oral region.(17) Autotransplantation of
premolars has been reported to be a useful treatment modality in cases of
agenesis or traumatic loss of teeth. (18) Hypodontic patients
presented a higher risk of having various dental abnormalities.(4,5,6) The possible explanation is
that a certain genetic mutation might cause a series of different phenotypic
expressions. Uslenghi et al. reported that there was on average a
1.51-year delay in dental development for children with hypodontia and the
severity of hypodontia was directly linked with the extent of delayed dental
development.(5) Therefore,
hypodontia will delay the onset and modify the orthodontic treatment planning.
In addition, skeletal features may differ significantly among patients with and
without multiple missing teeth. As a consequence, restorative treatment can be
comprehensive, requiring an interdisciplinary approach.(19,20)
Conclusion
In the present study, the overall presence of hypodontia, as well as the
characteristics of the most frequently missing teeth, were in accordance with
the findings of most studies conducted in other countries. Accurate diagnosis
of hypodontia is the key to orthodontic treatment planning and eventual
treatment itself. Furthermore, additional knowledge of dental development will
contribute valuable insights for novel therapeutic regiments in the future so
that we can move from a mode of diagnosis and treatment to one of prediction
and prevention.
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