Introduction
Delayed tooth eruption is often seen in patients with palatally displaced canines (PDC), but there is controversy over whether tooth formation is also delayed. This study attempts to elucidate the answer by addressing methodological shortcomings in previous studies.
Methods
Archived records were searched, and 100 patients (aged 8-16 years) with unilateral PDC were identified. Records of 50 women and 50 men were matched for age and sex with unaffected controls. The exclusion criteria included hypodontia. Dental age (DA) was calculated using the population-specific Maltese database and subtracted from the chronological age (CA). Nonparametric tests were used to compare CA−DA in patients with PDC and controls to determine the DA of end-of-series teeth.
Results
No statistically significant difference with CA−DA between patients with PDC and controls was found. In addition, there were no particular teeth significantly delayed in development.
Conclusions
Unilateral PDC does not affect dental developmental age, and the end-of-series teeth investigated show no delay in development.
Highlights
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Records of patients with unilateral palatally displaced canines were compared with controls.
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The presence of unilateral palatally displaced canines did not affect dental age.
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No tooth types showed delayed development.
Delay in tooth eruption is a feature of patients with palatally displaced canine (PDC), but there is controversy over whether tooth formation is also delayed. A significant difference in dental age estimation (DAE) would affect treatment planning, forensic analysis and may indicate a systemic etiology for PDC. Newcomb first commented that children with PDC often exhibit delayed dental development , and other studies have supported this impression. A delay in tooth development could significantly affect forensic and legal examinations and treatment planning, as children and young adults with PDC would have a lower dental age (DA) than the rest of the population. Therefore, they may be assigned to the wrong age group. There is evidence that the DA of children with PDC may be different from the average. Examination of a potential connection between PDC and delay in the development of the teeth concluded that children with PDC do exhibit a delay. In another study on patients with unilateral PDC, the impacted side displayed later development than the nonimpacted side. The relation between PDC, buccally displaced canine (BDC), and DA was examined using the methods of Nolla and Demirjian et al. The results showed that late development of the dentition was related to patients with PDC only. Another comparison of unilateral PDC with BDC showed that less than half of subjects with PDC or BDC displayed late development of the dentition. The overall maturity of the cohort’s teeth was slightly advanced; however, this was clinically insignificant. In a study comparing PDC with BDC and controls, half the subjects in the PDC group were found to have late-developing dentitions. On the basis of the differences seen when subtracting chronological age (CA) from DA in their sample, the authors proposed that 2 types of PDC exist, with different etiologies for both. However, another group found that development of the dentition was delayed in subjects with both PDC and BDC. DA was significantly lower in patients with either anomaly compared with healthy controls.
Therefore, the literature reveals controversy regarding the association between PDC and delayed development of dentition. Although some studies conclude that patients with PDC show a significant delay in the development of the dentition, others hold that there is no difference in the effects on development. There are differences in methodology, which could account for the disparity in results. PDC is associated with tooth agenesis, and the latter is, in turn, strongly associated with a delay in DA. The maturation of teeth is later in men, and so when making comparisons, age and sex are confounders. This may be dealt with by matching the groups accordingly. Exclusion of hypodontia and age and sex matching was only performed in the study by Royzlo-Kalinowska et al. Neither Becker and Chaushu nor Naser et al give any information about whether the canines were erupted or impacted and what criteria were used for inclusion in the PDC or BDC groups. The 2 sexes differ significantly in the age at which the stages of tooth mineralization appear and the length of the interstage intervals. Bilateral PDC is considered to be more penetrant than unilateral PDC because it has a greater association with hypodontia, and therefore, bilateral PDC without hypodontia is relatively rare compared with unilateral PDC. The differing types of impaction and dissimilar ratios of unilateral to bilateral canines may account for differences between groups. Ideally, samples would only have 1 type of impaction. As gathering the required number of bilateral PDC subjects may prove difficult, a sample of patients with more common unilateral PDC would provide a homogenous group of impactions suitable for comparison with future studies. Accuracy in DAE is relevant even if a control group is used as the conversion of individual scores to DA may not be entirely consistent. A small standard deviation and a bias not significantly different from zero indicates accuracy. The use of a population-specific dataset enables highly accurate individual DAE, and the Maltese database scores well in this regard.
A study that addresses the main deficiencies of previous studies is proposed (ie, the exclusion of hypodontia subjects, age and sex-matched control group, a homogenous PDC sample, and the use of a population-specific reference dataset. In this patient, a validated reference dataset-specific for Maltese already exists. , In patients with hypodontia, the absent tooth is the most distal tooth of any series, and it is this tooth that contributes to the delay in development seen in patients with hypodontia. If a developmental delay exists in patients with PDC, this would be most evident in the end-of-series teeth. Therefore, this study aimed to see whether the DA of Maltese children with unilateral PDC varies from the norm and whether the end-of-series teeth exhibit delayed development. The null hypothesis is that there is no difference in dental development between children with unilateral PDC and children with normal dental development.
Method and materials
Ethical approval was granted by the University of Malta Research Ethics Committee and the Faculty Research Ethics Committee, Ref no. UREC-DP 1801006 DSG-2017-18-001.
Intraexaminer and interexaminer reliability tests were carried out on 15 dental panoramic tomograms (DPT), which did not form part of the dataset, with a 2-week interval between the first and second examination for both interexaminer and intraexaminer analyses.
The inclusion criteria for patients with PDC were as follows: (1) full Maltese identification card number; (2) unilateral PDC, confirmed by radiographic or clinical means; (3) no history of any disorder likely to affect tooth development; (4) aged 8-16 years; and (5) radiographs of good diagnostic quality.
The exclusion criterion was hypodontia, apart from third molar agenesis. As it is not possible to reliably identify peg-shaped lateral incisors on a DPT, this criterion was not included. In patients with >1 DPT, the earlier DPT was chosen to facilitate DAE and keep a purely cross-sectional sample.
The inclusion and exclusion criteria were similar for the control groups, with the difference that any history of PDC was considered an exclusion criterion for this group.
Fifty males and 50 females with unilateral PDC were identified from the radiographic archives at Mater Dei Hospital. PDC was defined as when the canine was found to be palatal to the line of the arch and unerupted. The canine position was assessed from radiographic and surgical records. Controls were matched for sex and within a 3-month age range from the same archive. The records were retrieved, and the medical history was confirmed as clear. As earlier stages of tooth development are more reliable for DAE, when >1 DPT existed for a PDC subject, the earlier one was preferred. All radiographs were assessed by the same author (F.H.) on the same monitor, blinded to the age or date of birth of the subject when assessing stages. Images were viewed using the Centricity Universal Viewer (GE Healthcare, Chicago, Ill). Digital magnification allowed for more accurate analysis. No more than 10 radiographs were analyzed by the examiner at any one session to reduce measurement errors to minimise examiner fatigue. The individual DPTs were anonymized by conversion of personal details to a code and recorded on an Access Database (Microsoft Corp, Redmond, Wash) specifically set up by the Dental Age Research London Information Group for DAE, using the method established by this research group (ie, employing the 8 stage Demirjian method together with population-specific data). In this study, the DA was estimated using Quicksheet (Draft, Derek, personal communication) an Excel-based program (Microsoft Corp) designed to automatically convert Demirjian stages to DA. Quicksheet was primed with data specific to the Maltese population. CA was determined by subtracting the subject’s date of birth from the date of exposure. The number of days was divided by 365.25 to give a decimal figure. DA was subtracted from CA in all 4 groups to detect any variation in DA between the groups, a positive figure indicative of a delay in dental development and vice versa. The Demirjian tooth development stages of most distal teeth of the premolar and molar series (ie, second premolar and the third molar) were converted to Arabic numerals ( Table I ), and patients with PDC were compared with controls to see if there was any tooth that exhibited any particular delay. Only left-sided teeth were assessed, apart from the third molars, in which both left and right sides were assessed. When there was a difference in the stage between sides, the average was taken.
| Key | Demirjian stage | Arabic numeral |
|---|---|---|
| A | 1 | |
| B | 2 | |
| C | 3 | |
| D | 4 | |
| E | 5 | |
| F | 6 | |
| G | 7 | |
| H | 8 | |
| Missing | J | 9 |
| Unreadable | K | 10 |
The interexaminer and intraexaminer tests were carried out using Cohen’s kappa test (Stata software, version 26; StataCorp, College Station, Tex). In addition, the Microsoft Excel 5.11 plugin, Analyse-it (Analyse-it Software Ltd, Leeds, United Kingdom), was used to compute summary statistics, normality test (Shapiro-Wilk), and paired tests (Wilcoxon signed rank test). The significance level was set at P <0.05.
Results
The kappa statistic for the intraexaminer agreement was 0.99, whereas the interexaminer agreement was 0.65.
The age distribution of the sample is illustrated in Table II . The summary statistics for the 4 groups are presented in Table III . Two patients, 1 in the male unilateral and 1 in the female unilateral group, were found to have all teeth in stage H and were therefore excluded from the analysis, together with their paired individual. This left 49 patients in each of the PDC and control groups.
| Age band | Frequency male unilateral | Frequency male control | Frequency female unilateral | Frequency female controls |
|---|---|---|---|---|
| ≥8 to <8.25 | 0 | 0 | 0 | 0 |
| ≥8.25 to <8.5 | 0 | 0 | 0 | 0 |
| ≥8.5 to <8.75 | 0 | 0 | 0 | 0 |
| ≥8.75 to <9 | 1 | 0 | 0 | 0 |
| ≥9 to <9.25 | 0 | 1 | 0 | 0 |
| ≥9.25 to <9.5 | 1 | 1 | 0 | 0 |
| ≥9.5 to <9.75 | 0 | 0 | 0 | 0 |
| ≥9.75 to <10 | 0 | 0 | 0 | 0 |
| ≥10 to <10.25 | 1 | 1 | 0 | 0 |
| ≥10.25 to <10.5 | 0 | 1 | 0 | 0 |
| ≥10.5 to <10.75 | 1 | 0 | 0 | 0 |
| ≥10.75 to <11 | 1 | 1 | 1 | 1 |
| ≥11 to <11.25 | 0 | 0 | 1 | 1 |
| ≥11.25 to <11.5 | 1 | 0 | 1 | 0 |
| ≥11.5 to <11.75 | 0 | 1 | 1 | 2 |
| ≥11.75 to <12 | 0 | 0 | 0 | 1 |
| ≥12 to <12.25 | 3 | 2 | 4 | 3 |
| ≥12.25 to <12.5 | 2 | 3 | 7 | 2 |
| ≥12.5 to <12.75 | 4 | 6 | 1 | 6 |
| ≥12.75 to <13 | 4 | 2 | 3 | 3 |
| ≥13 to <13.25 | 3 | 3 | 5 | 5 |
| ≥13.25 to <13.5 | 2 | 1 | 6 | 4 |
| ≥13.5 to <13.75 | 4 | 5 | 2 | 4 |
| ≥13.75 to <14 | 1 | 1 | 5 | 5 |
| ≥14 to <14.25 | 3 | 3 | 3 | 2 |
| ≥14.25 to <14.5 | 2 | 4 | 0 | 2 |
| ≥14.5 to <14.75 | 7 | 3 | 2 | 1 |
| ≥14.75 to <15 | 4 | 5 | 1 | 1 |
| ≥15 to <15.25 | 2 | 3 | 3 | 1 |
| ≥15.25 to <15.5 | 1 | 1 | 3 | 3 |
| ≥15.5 to <15.75 | 2 | 2 | 1 | 3 |
| ≥15.75 to <16 | 0 | 0 | 0 | 0 |
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