A Scientific essay in Medical Sciences DOCTORAL THESIS To obtain the degree of doctor from the University of Nijmegen on the authority of Rector Prof.dr. C.W.P.M. Blom according to the decision of the Council of Deans to be defended in public on Monday 24th May, 2004 at 1.30 a.m. By: Emeria Abella Mugonzibwa Born in Bukoba (Tanzania) on April 21th, 1958

Chapter 1 [contents]

Chapter 1 provides a short introduction to the thesis by giving an overview of the background and rationale for the study.

Chapter 2 [contents]

The aim of the study described in Chapter 2 was to investigate the emergence of permanent teeth among Tanzanian children. A total of 869 Tanzanian children were recruited from 16 schools in age groups 3½-5, 6½-8, 9½-11, and 15-16 years old of whom 428 (49%) were boys and 441 (51%) were girls. The effects of age and gender on the emergence stages of the dentition were determined for the four age groups. Girls but not boys had some permanent maxillary canines, second premolars and mandibular and maxillary second molars as early as at the age of 6½-8 years. Permanent teeth of both the first and the second transitional periods were already emerging at the age of 3½-5 years and 6½-8 years, respectively. At 3½-5 years, 9% of the permanent teeth belonging to the first transitional period were already in occlusion. Emergence of incisors and first molars was more advanced in girls than in boys in age groups 3½-5 and 6½-8 years. Parallel to earlier reports on different ethnic groups, the results of this study indicate that the permanent teeth of Tanzanian children erupt earlier in girls than in boys, and the mandibular teeth erupt earlier than the corresponding maxillary teeth. The difference between boys and girls was found in both the first and second transitional period. Permanent teeth in Tanzanian children emerge clearly earlier than in Caucasian children.

Chapter 3 and 4 [contents]

Occlusal and space characteristics and anomalies were studied in Chapters 3 and 4 among 869 Tanzanian Bantu representing Africans and 706 Finnish children representing Caucasians during different emergence stages of the dentition. Significant differences between Africans and Caucasians were found in malocclusion, neutral, mesial and distal molar occlusions, deep bite and anterior open bite. The most prevalent anomaly among African children was anterior open bite followed by distal molar occlusion and large overjet. For the Caucasian children, distal molar occlusion was the most prevalent followed by large overjet and lateral cross bite. Anterior cross bite and scissors bite were rare and almost equally distributed between the two ethnic groups. A significant gender difference was found for overjet in both groups and overbite among Caucasians, boys having larger mean value than girls reflecting sexual dimorphism. Various developmental changes in occlusion were observed leading to variation in occlusal characteristics and anomalies according to emergence stages of the permanent dentition. Crowding was more common in the maxilla and in both arches together while in Caucasian children crowding increased with emergence stage. Crowding among Africans tapered off in the late mixed dentition. While planning resources for orthodontic treatment for different population groups and individuals, ethnic background and emergence stage of the dentition need to be considered.

Chapter 5 [contents]

In Chapter 5 the assessment of the opinions of Tanzanian children on dental attractiveness and their perceptions of orthodontic treatment need in relation to their own dental attractiveness as measured by the aesthetic component (AC) of the Index of Orthodontic Treatment Need (IOTN) is presented. In a random sample of 386 school children (48% boys, 52% girls), aged 9 to 18 years, the subjective need was assessed by using a prestructured questionnaire, and attractiveness was scored by using 18 intra-oral frontal photographs. Orthodontic treatment need was measured with the IOTN, and 11% of the children definitely needed orthodontic treatment (grades 8-10 of the AC with 4-5 of the DHC). The AC indicated that 11% of the children needed orthodontic treatment, whereas the DHC indicated 22%. Although 38% of the children said they needed treatment, 17% and 23% were unhappy with the arrangement and the appearance of their teeth, respectively. Most children (85%) recognised well-aligned teeth as important for overall facial appearance. Photographs showing severe deviations including crowding were regarded as the most unattractive, with older children tending to dislike them the most (p<0.0005). This suggests that, from the children’s point of view, grades 8-10 of the AC and 4-5 of the DHC could be given the first priority when considering an orthodontic treatment policy in Tanzania.

Chapter 6 [contents]

The objective of the study described in Chapter 6 was to investigate the opinion of Tanzanian parents on dental attractiveness and to compare their opinion with that of their children. A prestructured questionnaire with 18 intra-oral frontal photographs was given to 286 parents and their children aged 9-18 years. The photographs represented various types of occlusal traits, with the first ten intra-oral photographs representing grade 1-10 of the Aesthetic Component (AC) of the Index of Orthodontic Treatment Need, and the remaining eight photographs were added to represent malocclusions that are often seen in Tanzania. Photographs showing severe deviations were perceived by both children and parents as the most unattractive. The opinion was significantly correlated with children’s age (P=0.02) and sex (P<0.0005) with older girls tending to dislike photographs showing severe deviations the most. The mean of the opinion for the photographs showing some spacing with overbite <2 mm or open bite, and spacing with overbite >2 mm fell in the middle of the scale with a tendency towards unattractiveness. Photographs matching 8-10 of the AC scale were perceived as the most unattractive indicating what could be lay person’s priority when considering an orthodontic treatment policy in Tanzania.

Chapter 7 [contents]

In Chapter 7 the need for orthodontic treatment among Tanzanian Bantu children has been investigated. Dental casts of 643 Tanzanian subjects in age groups 3-5, 6-8, 9-11, and 15-16 years, were assessed using the Index of Orthodontic Treatment Need (IOTN). Aesthetic treatment need (AC grades 8-10) and dental health component (DHC grades 4-5) occurred in 5-15% and 16-36% of the studied children, respectively. The need measured by DHC increased significantly between the two oldest age groups. An absolute need measured by combining AC grades 8-10 and DHC grades 4-5 was found in 3-12% of the subjects and it increased significantly with age (p<0.03). The most prevalent severe occlusal feature placing the children in the great need category was cross bite. While about 3-19% of the children had distal occlusion (Angle’s Class II), mesial molar occlusion (Angle’s Class III) was rare, occurring in 1-3% of the children. The study showed that need for orthodontic treatment among Tanzanian children is comparable to other populations elsewhere. It provides baseline data that may be useful for the public oral health service to determine priority for orthodontic treatment as part of comprehensive child oral health care in Tanzania.

Chapter 8 [contents]

In Chapter 8, a case control study involving 852 Tanzanian Bantu children aged 9-18 years attending Muhimbili National Hospital (MNH) paedodontic clinic in the city of Dar es Salaam is presented. The aim of this study was to investigate the demand for orthodontic treatment among children seeking dental care in Dar es Salaam, Tanzania. Most of the children (85%) in the case group attended the dental clinic because of crowding. Aesthetic impairment (AC grades 8-10) and severe malocclusions (DHC grades 4-5) were higher in cases than in controls being 47% and 5%; and 67% and 18%, respectively (p<0.0001). Absolute need (combined AC grade 8-10 and DHC 4-5) was found in 29% of the cases and 5% of the controls (p<0.0001). A relative probability for a child with absolute need to seek orthodontic treatment was 7.9 higher [95% CI for OR= (5,13)] compared to a child without an absolute need for orthodontic treatment. The most prevalent severe occlusal feature placing cases in the highest need category was crowding (74%). For the cases, it was mainly a mother (45%) who first recognised the problem, and tooth extraction (62%) was the most common expected mode of treatment. Most parents (96%) were prepared to pay for their children’s orthodontic treatment.

Chapter 9 [contents]

Finally in Chapter 9, the findings of the previous chapters are discussed in relation to each other. In order to provide an affordable orthodontic care to every Tanzanian child in need of orthodontic services the following is recommended: the implementation of preventive, simple interceptive orthodontics in the Tanzanian oral health care system; curricula review to empower the oral health cadres in Tanzania to provide appropriate orthodontic care to both urban and rural populations; focus on children aged 6-14 during development of the permanent dentition as a target group; carrying out research on the Tanzanian dental practitioners’ orthodontic diagnostic skills and their opinion towards malocclusions and orthodontic treatment; and developing a simple instrument (orthodontic instruction) that could be used by dentists, ADO’s and DT’s in the observation of development of malocclusions in order to perform the right interceptive measures at the right time.