Craniofacial characteristics of children with mild hypodontia.

INTRODUCTION: The aim of our study was to evaluate the craniofacial characteristics of children with mild hypodontia using conventional and principal component (PC) analysis. METHODS: We used radiographic images of 124 children (8-12 years old) with up to 4 missing teeth (55 boys, 69 girls) and of 676 reference children (365 boys, 311 girls) from the Rotterdam Generation R Study and the Nijmegen Growth Study in The Netherlands. Fifteen cephalometric measurements of children with hypodontia were compared with those of the reference children. Moreover, cephalometric parameters were combined into standardized PC scores using PC analysis, and the components were compared between the 2 groups. RESULTS: PC analysis showed common dental characteristics for all types of hypodontia: a significant increase of the interincisal angle, and decreases of the maxillary and mandibular incisor angles. Other findings were consistent when both methods were applied: (1) anterior hypodontia was significantly associated with the high-angle (hyperdivergent) craniofacial pattern, (2) the tendency toward a Class III malocclusion was identified in maxillary hypodontia, and (3) we observed a significant reduction of lower posterior facial height in children with posterior and mandibular hypodontia. CONCLUSIONS: Our findings suggest that children with mild hypodontia have distinctive skeletal and dental features.

New neonatal classification of unilateral cleft lip and palate part 2: to predict permanent lateral incisor agenesis and maxillary growth.

Objectives : To bring a neonatal classification system of unilateral cleft lip and palate and to correlate this classification with the distribution of the permanent lateral incisor and maxillary growth. Design : Retrospective with longitudinal follow-up. Setting : Tertiary. Patients : A total of 112 individuals with treated unilateral cleft lip and palate and 30 controls. Main Outcome Measures : Unilateral cleft lip and palate neonatal casts were classified anatomically in four categories, in which Class 1 corresponds to a maxillary arch with a narrow alveolar cleft; Class 2 corresponds to a balanced form; Class 3 corresponds to a wide cleft and short maxilla; and Class 4 corresponds to a wide cleft and long maxilla. The classification was correlated with the distribution of the permanent lateral incisor. Maxillary growth was evaluated using a cephalometric analysis after the age of 10 years. Results : Clinical classification of unilateral cleft lip and palate found 10 cases of Class 1 (8.9%), 34 cases of Class 2 (30.4%), 46 cases of Class 3 (41.1%), and 22 cases of Class 4 (19.6%). The permanent lateral incisor was most often present in narrower clefts (Classes 1 and 2); whereas, large clefts (Classes 3 and 4) were relatively more frequently associated with an agenesis of the permanent lateral incisor (P = .019). Maxillary growth impairment was most severe in Class 3, with a mean sella-nasion-A point angle at 71.9° ± 4.6° (P < .001). Conclusions : Using the cleft width, arch form, and shape of the nasal septum, unilateral cleft lip and palate can be classified into four different classes at birth, which can all give information about permanent lateral incisor agenesis and maxillary growth.

Prevalence and patterns of permanent tooth agenesis in patients with nonsyndromic Pierre Robin sequence.

INTRODUCTION: Individuals with Pierre Robin sequence (PRS) frequently have tooth agenesis, especially in the mandible. The aims of this study were to characterize permanent tooth agenesis patterns and to determine their prevalence in patients with nonsyndromic PRS. METHODS: Radiographs and clinic charts of 146 children with nonsyndromic PRS were examined for permanent tooth agenesis, excluding third molars, and the tooth agenesis patterns were identified with the tooth agenesis code. RESULTS: The overall prevalence of permanent tooth agenesis was 32.9% (48 of 146 patients), with about two thirds having bilateral tooth agenesis. No sex or racial predilection was found for tooth agenesis. The most common tooth agenesis pattern was the absence of both mandibular second premolars. Among the children with tooth agenesis, almost half had agenesis patterns involving both mandibular second premolars. Other common patterns of permanent tooth agenesis involved the maxillary lateral incisors and the maxillary premolars. CONCLUSIONS: Symmetric agenesis of individual tooth types occurs much more frequently in the mandible than in the maxilla in patients with nonsyndromic PRS. Bilateral absence of the mandibular second premolars is the predominant pattern of dental agenesis.

[Some aspects of terminology, classification and incidence of hypodontia].

The paper presents the data of literature review on epidemiology, patterns and prevalence of hypodontia depending on race, nationality and gender of the patients. Correlation between congenital absence of the temporary and permanent teeth are discussed as well as the matters of the terminology and classification depending on the severity of this abnormality.

Patterns of tooth agenesis in patients with orofacial clefts.

Orofacial clefts are a common oral disorder associated with tooth agenesis. As information on the simultaneous absence of teeth can be an aid in treatment planning, a large sample of orofacial cleft patients was examined. The sample consisted of 910 patients with cleft lip and palate. Tooth agenesis was assessed on the basis of at least two panoramic radiographs and patient records. Third-molar agenesis was determined in 474 patients. Patterns of tooth agenesis were analysed using Tooth Agenesis Code (TAC) values, according to VAN WIJK & TAN. Per quadrant, at least 90% of patients could be described according to three different patterns. In the maxilla, 85% of patients with tooth agenesis had a TAC-value of 2, 16, or 18 on either the left side, right side or bilaterally. In the mandible, 90% of patients with tooth agenesis had a TAC-value of 16, 1 or 2 on either the left side, right side or bilaterally. In patients with tooth agenesis, patterns were symmetrical in the maxilla in 18.8% and in the mandible in 51%. More extended cleft types were associated with a higher prevalence of tooth agenesis. Third-molar agenesis (prevalence = 22.4%) was significantly related to the prevalence of other absent teeth. These results show which patterns of tooth agenesis can be expected to occur in most orofacial cleft patients.

The impact of tooth agenesis on oral health-related quality of life in children.

OBJECTIVE: The purpose of this cross-sectional survey was to evaluate the psychosocial impact of tooth agenesis in children and to investigate the potential influence of gender, socioeconomic status, severity of tooth absence, and the number of retained primary teeth on their quality of life. MATERIALS AND METHODS: A total of 86 children (36 male, 50 female) with tooth agenesis, aged 11-14 years were recruited from the Birmingham Dental Hospital, United Kingdom. Thirty subjects with a complete dentition and having a low treatment need acted as controls. Children completed the validated Child Perceptions Questionnaire (CPQ) and their parents completed the Parental-Caregiver Perceptions Questionnaire (P-CPQ). RESULTS: The median number of missing teeth in the sample population was 6. There were significant differences in the oral symptoms, functional limitations and the social and emotional well-being reported between the agenesis and control groups. The overall CPQ scores were significantly higher in children with tooth agenesis (P<0·001). No significant correlation was detected between the number of missing teeth and the quality of life score. There was no influence found on the CPQ score from gender, socioeconomic status, the site of agenesis or the presence of retained primary teeth. There was moderate correlation between parental and child reported quality of life. CONCLUSIONS: Tooth agenesis can have a significant impact on the quality of life of children, resulting in oral symptoms, functional limitation and also affecting emotional and social well-being. This does not appear to be related to the number of missing teeth. This study has implications for our understanding of the effect of tooth absence on the quality of life of children and their parents and addressing these reported impacts may help to improve patient satisfaction.

A comparison of skeletal maturation in patients with tooth agenesis and unaffected controls assessed by the cervical vertebral maturation (CVM) index.

OBJECTIVE: The aims of this study were to (1) investigate if there is a difference in skeletal maturation between tooth agenesis and control patients and (2) whether skeletal maturation is affected by the severity of tooth agenesis. The cervical vertebral maturation (CVM) index can be used to assess skeletal maturation. DESIGN: A retrospective cross-sectional study. SETTING: Eastman Dental Hospital, London, UK. METHODS AND MATERIALS: A total of 360 cephalograms of patients aged 9-17 years (164 males and 196 females) allocated to four subgroups (mild, moderate and severe tooth agenesis patients, and controls) were assessed retrospectively. There were 90 patients in each of the four subgroups. The skeletal maturation of each subject was assessed both quantitatively and qualitatively using the CVM index. All patients in the study were either currently receiving treatment or had been discharged from the hospital. RESULTS: There was no statistically significant relationship between skeletal maturation and the presence of tooth agenesis. Furthermore, there was no statistically significant relationship between the skeletal maturity of patients and different severities of tooth agenesis. CONCLUSIONS: The data obtained from this group of patients and using this measurement tool alone does not supply sufficient reason to reject the null hypothesis. However, it suggests that it is possible that no difference exists between the groups.

Radiographic study of delayed tooth development in patients with dental agenesis.

INTRODUCTION: The aims of this study were to compare the radiographic development of permanent teeth in a group of children affected by dental agenesis with an unaffected control group and to determine the effects of confounding factors including the severity of the dental agenesis, age, sex, ethnicity, and the number of stages used to estimate dental age. METHODS: A single-center retrospective cross-sectional study of dental panoramic tomographs was undertaken between July 2007 and April 2008 in a postgraduate teaching school. A total of 139 patients (aged 9-18 years) were recruited from the orthodontic clinic on the basis of predetermined inclusion and exclusion criteria to either a dental agenesis group or a control group. Dental panoramic tomograms were assessed, and the stages of development of the permanent teeth in the left maxillary and left mandibular regions were scored by using the 12 stages of Haavikko and the 8 stages of Demirjian and Goldstein. For each tooth scored, the mean dental age and standard error were determined by using the dental age assessment method, and an estimated dental age for each subject was derived by using the weighted average method. RESULTS: A statistically significant delay in dental age was found in the patients with dental agenesis compared with the control group. The dental age assessment method of Haavikko showed a delay of 1.20 years (SD, 1.74), and the method of Demirjian and Goldstein showed a delay of 1.64 years (SD, 1.75). It was also observed that older patients with dental agenesis had greater delays in tooth formation (P <0.001). With the Haavikko method, for every year of chronologic age, the delay in dental age increased by 0.53 year; with the Demirjian and Goldstein method, the delay increased by 0.48 year. A significant association was seen between the severity of dental agenesis and the delay in dental age (P <0.01). With both methods, for each additional developmentally absent tooth, the dental age was delayed by 0.13 year (lower confidence interval, -0.22; upper confidence interval, 0.35). There was no evidence that sex or ethnicity has an effect on the delay in dental age in patients with dental agenesis. CONCLUSIONS: The development of permanent teeth in children with dental agenesis is delayed when compared with a matched control group. The severity of dental agenesis affected the magnitude of the delay (P <0.01). This delay has implications in orthodontic treatment planning and in the estimation of age for legal, immigration, archaeological, and forensic purposes.

Prevalence and intra-oral distribution of agenesis of permanent teeth among Eastern Turkish children.

AIM: The aim of this study was to describe agenesis of permanent teeth, excluding the third molars, in a sample of children in Eastern Turkey. MATERIALS AND METHODS: This retrospective study assessed 1,291 digital orthopantomograms (OPT) (678 males and 613 females), taken at the Faculty of Dentistry, Ataturk University, Erzurum. The chi-square test was used to compare maxillary and mandibular hypodontia in males and females. RESULTS: Eighty children were found to have at least one tooth absent from their permanent set of teeth. The prevalence of tooth agenesis was 6.2%. A total of 135 permanent teeth were missing as a result of the congenital condition. Tooth agenesis was found more frequently in females than in males. Although there was no significant difference between genders in the prevalence of hypodontia among the children (p>0.05), the difference between genders in children who had congenitally missing teeth (CMT) reached a statistically significant level (p<0.05). CONCLUSION: When hypodontia in a Turkish paediatric population was compared to other populations, the characteristics were found to be similar to the Western population. However, the population in Eastern Turkey differs from the population in Asia, where there is less incisor tooth agenesis and more second molar tooth agenesis.

Application of the dental aesthetic index in the prioritisation of orthodontic service needs.

OBJECTIVE: The provision of orthodontic treatment to patients in government funded training institutions is a major challenge due to constrained budget and resource allocation. The Dental Aesthetic Index (DAI) has been used to estimate orthodontic treatment need and as a screening tool to determine treatment priority. The DAI focuses on aesthetics and therefore omits other malocclusion traits that might require orthodontic treatment. The aim of the study was to compare the application of the DAI with the influence other malocclusion traits not included in the DAI might have on the determination of the prioritisation of orthodontic service need. METHODS: Hundred-and-twenty pretreatment study models of orthodontic patients in the permanent dentition stage were selected from the archived records of the Department of Orthodontics, University of Limpopo, using a systematic sampling method. The study casts were assessed using the DAI. Other malocclusion traits not included in the DAI were also recorded. Descriptive statistics, the Pearson correlation coefficient, Chi-square values and t-tests were employed to analyse the data. P values less than or equal to 0,05 were considered statistically significant. RESULTS: The mean DAI score was 35.2. Normal or minor malocclusion was found in 19.1% of the sample, whilst 17.5% had definitive malocclusion, 21.7% severe malocclusion, and 41.7% showed handicapping malocclusion. Other malocclusion traits not included in the DAI were identified and these traits accounted for 21.6% of all traits recorded in the study (DAI malocclusion traits accounted for 78.4%). Two thirds of other malocclusion traits were accounted for in categories which the DAI had already prioritised for treatment. CONCLUSIONS: The study showed that the DAI can be used to prioritise orthodontic service needs and could be applied in government funded institutions.

Dental agenesis patterns of permanent teeth in Apert syndrome.

Dental agenesis may either occur as an isolated trait (non-syndromic) or as a component in a congenital syndrome. The aim of the present study was to identify the prevalence of dental agenesis for each type of tooth and to look for dental agenesis patterns in persons with Apert syndrome. Serial panoramic radiographs of 23 individuals (five male patients and 18 female patients) were examined. Third molars were excluded. The prevalence of agenesis for at least one tooth was 34.8%. Up to two missing teeth were found for individuals with Apert syndrome. Maxillary lateral incisors and mandibular second premolars were the most frequently missing teeth. Four different dental agenesis patterns of the entire dentition were identified by using the tooth agenesis code (TAC). Two patterns occurred more frequently, both of which were symmetrical. One involved the simultaneous absence of teeth 12 and 22, and the other showed agenesis of teeth 35 and 45. In conclusion, patients with Apert syndrome were found to exhibit a high prevalence of dental agenesis. All dental agenesis patterns in which more than one tooth was missing were symmetrical.

Severe hypodontia: identifying patterns of human tooth agenesis.

Tooth agenesis is the most common dental anomaly. The aim of this retrospective study was to identify common patterns of tooth agenesis in a sample of 92 patients (55 females and 37 males; mean age 27.7 years) with non-syndromic severe hypodontia. The Tooth Agenesis Code (TAC) procedure was used for that purpose. The patients in this study were missing between 6 and 22 permanent teeth (mean 11.6; median 10.0; SD 4.35). In the maxilla, 47.9 (left side) and 50.0 (right side) per cent can be described using only five different patterns. The most common patterns involved agenesis of the maxillary lateral incisor and both premolars. In the mandible, 35.8 (lower left) or 43.5 (lower right) per cent can be described by five patterns, the most common of which was agenesis of all mandibular premolars. When comparing patients with and without symmetric agenesis patterns (symmetry in the upper or lower arch versus no symmetry), a Student's t-test revealed no difference in the total number of missing teeth. Common patterns of tooth agenesis were successfully identified in patients with non-syndromic severe hypodontia. The present findings may be used to develop interdisciplinary treatment protocols for the most common patterns to increase the quality of interdisciplinary treatment for patients with severe hypodontia.

Dentofacial characteristics of patients with hypodontia.

This study aims to identify distinctive dentofacial characteristics of hypodontia patients. For this purpose, 189 young hypodontia patients (cases) were divided into subgroups, based on criteria from literature. Normalised differences between cases and controls were calculated for various parameters of dentofacial form. Subsequently, cluster analysis was applied to disclose subsets of hypodontia patients with distinctive dentofacial features. The ANB angle, interincisal angle and lower anterior face height were consistently significantly different amongst the subsets. Four clusters of patients with an increasing number of missing teeth and distinctive dentofacial characteristics could be identified. Patients in cluster 1 display a high-angle facial pattern. Patients in clusters 2 and 3 exhibit markable dentoalveolar characteristics (a relatively small and a large interincisal angle, respectively). Patients in cluster 4 exhibited notable sagittal-skeletal discriminative features predominantly because of a retrognathic maxilla. The smallest nasolabial angle and lower anterior face height were seen in this cluster. It is concluded that the anterior-posterior relationship between the jaws, the interincisal angle and the lower anterior face height are discriminative parameters of dentofacial form in hypodontia patients. Patients with hypodontia can be clustered in four groups, each with distinctive vertical-skeletal, dentoalveolar and sagittal-skeletal characteristics. This categorisation of patients with hypodontia into meaningful groups may be useful for treatment planning, interdisciplinary communication and as a means of identifying groups of patients that qualify for reimbursement of costs. Other dental factors should be appreciated as well during restorative clinical decision making in patients with hypodontia.

Three-dimensional assessment of the eruption path of the canine in individuals with bone-grafted alveolar clefts using cone beam computed tomography.

OBJECTIVE: To evaluate the eruption path of the permanent maxillary canine during a 1-year period after secondary alveolar bone grafting and to (1) compare the canine eruption path on the cleft and noncleft side, (2) examine the number of congenially missing lateral incisors and the rate of canine impaction, and (3) examine the relationship between the eruption status of the canine and timing of alveolar bone grafting relative to age and canine root development using cone beam computed tomography (CBCT). METHODS: Cone beam computed tomography scans for 17 nonsyndromic unilateral cleft lip and palate (UCLP), and four bilateral cleft lip and palate (BCLP) consecutive cases of alveolar bone grafting surgery were obtained after orthodontic expansion and before alveolar bone grafting and at least 1 year postsurgery on the Hitachi MercuRay CBCT machine. The DICOM files were imported into Dolphin 3D Imaging 10.5 and reoriented for consistency. The X, Y, and Z coordinates were determined for the canine cusp tip and root tip on both the cleft and noncleft sides. The direction of movement of the canine in 1 year was determined. RESULTS: Most canines on both the cleft and noncleft sides moved incisally, facially, and mesially. Twelve percent of the canines on the cleft side appeared to require surgical exposure. Eighty percent of the canines had less than half root development at the time of bone grafting. The amount of root development did not affect the outcome in terms of eruption amount or direction. CONCLUSIONS: Most canines on both the cleft and noncleft side moved incisally, facially, and mesially.

Oral health-related quality of life of children with oligodontia.

OBJECTIVES: To assess the functional and psychosocial impact of oligodontia in children aged 11-14 years. METHODS: Children aged 11-14 years with oligodontia were recruited from orthodontic clinics when they presented for orthodontic evaluation. All completed a copy of the Child Perceptions Questionnaire for 11- to 14-year olds, a measure of the functional and psychosocial impact of oral disorders. Information on the number and pattern of missing teeth for each child were obtained from charts and radiographs. RESULTS: Thirty-six children were included in the study. The number of missing teeth ranged from one to 14 (mean = 6.8). Just over three-quarters of the subjects reported experiencing one or more functional and psychosocial impacts 'Often' or 'Everyday/almost everyday'. Correlations between scale and sub-scale scores and the number of missing teeth were weak and nonsignificant. CONCLUSIONS: Children with oligodontia experience substantial functional and psychosocial impacts from the condition. When compared with other clinical groups, children with oligodontia appear to have worse oral health-related quality of life than children with dental decay and malocclusion, but better oral health-related quality of life than children with oro-facial conditions.

Patterns of tooth agenesis in patients with Down syndrome in relation to hypothyroidism and congenital heart disease: an aid for treatment planning.

INTRODUCTION: The purposes of this study were to investigate the patterns of tooth agenesis (oligodontia and nonoligodontia), maxillary canine impaction, and tooth transposition in subjects with Down syndrome and to determine whether congenital heart disease and hypothyroidism are parameters in tooth agenesis. METHODS: The study included 114 patients with Down syndrome. The data were quantified by using standardized records, clinical examinations, panoramic radiographs, and solo roentgenograms. The subjects were differentiated into oligodontia (6 or more teeth missing) and nonoligodontia (5 or fewer teeth missing). RESULTS: In these patients with Down syndrome, 59.6% had missing teeth. Those in the nonoligodontia group showed a tendency toward a negative correlation between congenital heart disease and agenesis (P = 0.093; odds ratio = 0.49) but a slight positive correlation between hypothyroidism and agenesis (P = 0.060; odds ratio = 3.71). In the oligodontia group, there was a quantitatively and qualitatively different pattern, indicating another phenotype. When both mandibular central incisors were missing, there was a remarkable chance for oligodontia (P = 0.001; odds ratio = 38.8). In the mandible, symmetrical agenesis of the canines and lateral incisors was more frequent in the nonoligodontia group. CONCLUSIONS: The oligodontia (with a different phenotype) and nonoligodontia groups had different patterns of agenesis. Maxillary canine impaction was not related to absence of the lateral incisors. Absence of both mandibular central incisors was a high predictor for oligodontia. Congenital heart disease and hypothyroidism are parameters involved in tooth agenesis.

Taurodontism in children with hypodontia and supernumerary teeth: a case control study.

PURPOSE: The aim of the present investigation was to compare the prevalence of taurodontism in the permanent mandibular first molars of nonsyndromic children with hypodontia and supernumerary teeth with age- and gender-matched controls. METHODS: The crown-body root ratios of the permanent first molars were determined from orthopantomograms of 83 children with hypodontia (> or =1 missing teeth) and 37 children with supernumerary teeth (> or =1 extra teeth) compared with normal case controls. RESULTS: In children with hypodontia, only girls showed a significantly higher tendency for taurodontism compared to case controls (P=.003), while boys with hypodontia showed a similar prevalence of taurodontism as controls (P=.83). Children with multiple missing teeth were significantly more susceptible to taurodontism than children with a single missing tooth (P=.004). By contrast, the prevalence of taurodontism in children with supernumerary teeth was not significantly different from that of controls. CONCLUSIONS: Compared to normal case controls, children with nonsyndromic hypodontia are more likely to show taurodontism of the permanent first molar teeth whereas children with nonsyndromic supernumerary teeth are not.

Dental agenesis: genetic and clinical perspectives.

Dental agenesis is the most common developmental anomaly in humans and is frequently associated with several other oral abnormalities. Whereas the incidence of missing teeth may vary considerably depending on dentition, gender, and demographic or geographic profiles, distinct patterns of agenesis have been detected in the permanent dentition. These frequently involve the last teeth of a class to develop (I2, P2, M3) suggesting a possible link with evolutionary trends. Hypodontia can either occur as an isolated condition (non-syndromic hypodontia) involving one (80% of cases), a few (less than 10%) or many teeth (less than 1%), or can be associated with a systemic condition or syndrome (syndromic hypodontia), essentially reflecting the genetically and phenotypically heterogeneity of the condition. Based on our present knowledge of genes and transcription factors that are involved in tooth development, it is assumed that different phenotypic forms are caused by different genes involving different interacting molecular pathways, providing an explanation not only for the wide variety in agenesis patterns but also for associations of dental agenesis with other oral anomalies. At present, the list of genes involved in human non-syndromic hypodontia includes not only those encoding a signaling molecule (TGFA) and transcription factors (MSX1 and PAX9) that play critical roles during early craniofacial development, but also genes coding for a protein involved in canonical Wnt signaling (AXIN2), and a transmembrane receptor of fibroblast growth factors (FGFR1). Our objective was to review the current literature on the molecular mechanisms that are responsible for selective dental agenesis in humans and to present a detailed overview of syndromes with hypodontia and their causative genes. These new perspectives and future challenges in the field of identification of possible candidate genes involved in dental agenesis are discussed.

Agenesis of permanent teeth in 8138 Danish schoolchildren: prevalence and intra-oral distribution according to gender.

OBJECTIVE: The purpose of this study was to describe agenesis of permanent teeth in children with respect to prevalence and intra-oral distribution according to gender. METHODS AND SUBJECTS: The study was population based and included all children in one district of the municipality of Aarhus, Denmark, in 1974-1979 (1657 girls and 1668 boys) and 1992-2002 (2409 girls and 2404 boys). The children underwent systematical clinical and radiographic examination. RESULTS: The period prevalence rates were almost identical for the two time periods (1972-1979: 7.8%; 1992-2002: 7.1%). Girls were affected more frequently than boys, and affected girls had more congenitally missing teeth than affected boys. Unilateral agenesis of the second premolars was more frequent than bilateral agenesis. In children with only one congenitally missing tooth, agenesis of the upper lateral incisors was asymmetrical in girls, but not in boys, whereas the opposite was true for the lower second premolars in boys. CONCLUSION: The prevalence of agenesis of permanent teeth in Danish schoolchildren seems to be constant over time, and similar to that found in other large, population-based studies. Intra-oral distributions of congenitally missing teeth indicate gender-specific patterns.

Dental and occlusal features in patients with palatally displaced maxillary canines.

The aim of the present study was to determine the dental and occlusal features that could contribute to the aetiology of palatally displaced canines (PDCs). The material consisted of pre-treatment dental casts of 50 patients (36 females and 14 males) with unilateral and bilateral PDCs aged 14-16 years (mean 15.6 +/- 1.6 years). These were compared with a control group of 50 treated subjects (25 males and 25 females) of the same age with normally erupted maxillary canines. The following parameters were measured on the dental casts: the mesiodistal (MD) and buccolingual (BL) width of each maxillary tooth, the maxillary interpremolar and intermolar widths, overjet and overbite, dentoalveolar arch relationship (based on incisor classification), and missing or anomalous teeth. The differences between the PDC group and controls were determined using a Student's t-test. P values less than 0.05 were considered significant. PDCs occurred most frequently in subjects with a Class I occlusion. Sixteen per cent of the PDC subjects had congenital absence or peg-shaped lateral incisors or congenital absence of the second premolar, demonstrating a clear association between palatal impaction of the maxillary canine and anomalous or congenital tooth absence. The overjet was significantly smaller in the PDC female subjects, especially in those with unilateral impaction (P < 0.05). Overbite was significantly greater in PDC male subjects compared with the controls, especially in bilateral impaction cases. There was no statistically significant difference between the groups with regard to the maxillary transverse dimensions, maxillary MD widths, or palatal height for either gender.