PREVALENCE AND PATTERN OF THIRD MOLAR IMPACTION IN PATIENTS THAT VISITED UNIVERSITY OF

GHANA DENTAL SCHOOL’S CLINIC IN 2008.

By Dr. Gabriel Doe Ketemepi Supervised by: Prof G Parkins, Dr J Sackeyfio, Dr E Abdulai, Rev T Ndanu

• This study is a retrospective radiographic study of the prevalence of impacted third molars, the jaw and sex predilections and the types of impaction in patients between the ages of 15 and 60 years that reported at the University of Ghana Dental School’s clinic from January 2008 to December 2008.

Third molars

• Third molar teeth are the last teeth in the dental arch and usually appear between the ages of 16 and 25.

• They are called wisdom teeth because they come in when a person is old enough to have supposedly gained some wisdom.

• They vary very widely morphologically.

IMPACTION

• In 1926, George B Winter defined impaction to be failure of a tooth to fully erupt after root formation is completed.

• The third molar teeth are last to erupt and have a relatively high chance of becoming impacted.

• Several classifications of third molar impaction exist but in this study, a modified Winter’s classification was adopted. (shown below)

Orthopantomogram (OPG): Since its introduction in the 1960s, it has remained a valuable adjunct to conventional diagnostic procedures in dentistry.

• Third molar teeth are impacted more than other teeth of the human dentition. Their impaction is of concern due to several reasons. – Partially impacted teeth, particularly mandibular

third molars, may communicate with the oral cavity via inconspicuous periodontal pockets on the distal aspect of adjacent second molar, thus predisposing the impacted tooth to pericoronal infection and dental caries.

– Common complications of impacted third molars include root resorption of adjacent normal teeth, infection and its associated pain, and dentigerous cyst formation.

Aim and objecives

• The aim of this study was to determine the prevalence and pattern of third molar impaction in a Ghanaian population.

Method • Five hundred orthopantomogram records of Ghanaian

patients between the ages of 15 and 60years that reported in 2008 at UGDS were sampled through a number of sampling stages. All folders of patients treated in 2008 within the specified age group were collected. Then a systematic random sampling was done in which every 5th folder containing an OPG was selected.

• Personal details including age, sex, type of impaction and the jaw with the impaction of these patients were recorded. These parameters were gathered and fed into a Microsoft access program and analysed using SPSS16

Results

21.20

78.20

Prevalence of third molar impaction

Impaction PresentImpaction Absent

Male Female0

50

100

150

200

250

Third molar Impaction in the different sexes

Impaction AbsentImpaction Present

Sex

Num

ber o

f Pati

ents

Pattern Of ImpactionMAXILLA MANDIBLE

Left maxilla Right maxilla

Left mandible

Right mandible

Total

Mesioangular

1 0 52 46 99 (53.80%)

Distoangular 12 15 1 2 30 (16.30%)

Vertical 13 14 6 5 38 (20.65%)

Horizontal 0 1 9 7 17 (9.24%)

Total 26 31 68 60

184 (100%)56(30.43%) 128(69.57%)

Mesioangular Distoangular Vertical Horizontal 0

10

20

30

40

50

60

70

80

90

100

Patterns of Impaction

Right mandibleLeft mandibleRight maxillaLeft maxilla

Type of impaction

Perc

enta

ge o

f Im

pact

ed

DISCUSSION• The prevalence of third molar impaction was 21.2%

among the patients studied in UGDS clinic (106 out of 500). This compares favourably with a prevalence of 22.8% in an urban Nigerian population as reported by Olasaji and Odusanya.

• This prevalence is less than that of American males aged 17 - 26 years, in which 65% have 1 to 4 impacted third molars but higher than 9.2% among rural Nigerians (Morris

and Jerman, 1971; Odusanya, 1986).

• The prevalence of impacted third molar therefore seems to increase with increasing modernisation.

• The study revealed that the mean age of those with impaction was significantly lower than (30.29years) that of those without impaction (35.74years).

• Third molar impaction can therefore be said to be a problem of the youth.

• Odusanyi alluded to this fact. He studied the incidence and pattern of presentation of impacted third molar of Nigerian youths (aged 16 - 25) and older Nigerians (age 35 years and above) and discovered that impacted third molar were four and half times more common among Nigerian youths.

• This can be attributed to the fact that the younger generation tends to have smaller jaws due to changes in their diets which has become softer.

• Darwin, had previously noted that, the posterior dental portion of the jaw was always shortened in the more civilized races of man. He attributed this to “Civilized man’s habitually feeding on soft cooked food.”( Darwin, 1881)

• There are diverse opinions concerning the effect of masticatory function on the growth of the jaw bones. Brash and Brodie suggested that the size of the jawbone was determined by inherent genetic factors and that environmental condition were of little influence. (Brash, 1929 and Brodie, 1948)

• Roger and Stillman however maintained that functional stimulus is an important consideration and that without this stimulus jawbones were not likely to develop to their fullest extent providing space for the third molar to erupt.

• The dental arch length of Ghanaians may be undergoing an unnoticed transition process of disuse atrophy. With the continuous modernization of Ghana and copying of western life styles by the youth coupled with the attendant development of the urban areas, a number of significant alterations in the diet of Ghanaians occurred.

• As a result of these changes, the diet became much softer in its consistency.

• Bergman emphasized this view when he stated that, “our ancestors had larger jaws, so there was room in the human mouth for 32 permanent teeth, including third molars. But now our jaws are smaller.

• The result is that there is no longer room in most of our mouths to house 32 teeth. So the last teeth we develop often become impacted”. (Bergman J, 1998)

• The feminine dominance of this study may be due to the perception that women generally care more about their teeth and esthetic than male and report more often to treatment centres.

• The study however showed that there was no significant difference between the number of men (55) and women (51) that had third molar impaction.

• The most frequent angulation of impacted third molar teeth in the mandible was the mesioangular position. This pattern has been observed in most studies done by Odusanya in Nigeria, Kramer and Williams in Harlem and Guthua et al in Kenya. (Odusanya, 1984; Kramer et al, 1970; Guthua et al, 1992)

• The higher frequency of the mesioangular impaction in the mandible could be due the fact that when lower third molar teeth are developing, they have a mesial tilt. And until they are in full occlusion they do not get erect.

• Inability of the teeth to erupt into normal occlusion leaves it mesioangularly impacted against the second molar.

• Vertical impaction was the second overall highest pattern. The vertical pattern together with the distoangular pattern of impaction is the most frequent pattern of third molar impaction in the maxilla.

• The higher frequency of vertical and distoangular impactions in the maxilla may be due to the fact that the maxillary third molar develops in the maxillary tuberosity and generally erupt vertically as the maxillary bone enlarges, impaction against the second upper molar may therefore occur where maxillary growth is inadequate.

• The third molar therefore remains vertically below the second molar or gets displaced distally.

• The high prevalence of third molar impaction in the mandible is probably due to the short mandibular arch length and the fact that the mandible curves upward (forming the angle) around the region of the third molars making impaction more likely.

Conclusion• The prevalence of third molar impaction in the

population studied was 21.2% and the affected population was significantly younger than the unaffected.

• Compared with other studies, prevalence of impaction increases with increasing modernisation with the mandible having more impaction than the maxilla.

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