Dental and Skeletal Age in Patients with Palatally Displaced Canines.

Objective: To determine potential associations between dental and skeletal maturation and palatally displaced canines (PDC) considering gender and chronological age. Material and methods: This study included pretreatment panoramic and lateral cephalometric radiographs of 43 subjects with PDCs and 203 randomly selected orthodontic subjects with normally erupted canines. Both groups were non syndromic patients. Chronological age of subjects was rounded and noted in years with decimal points and compared with chronological age according to Demirjian's dental age assessment. Skeletal maturation was determined by cervical vertebrae changes on cephalometric radiographs.
Results: Female subjects with PDC were more affected by left side canine displacement than males (p=0.027) with five times higher odds ratio (OR = 4.9; 95% CIL=1.2-19.7). A comparison of chronologic and skeletal age indicated that PDC subjects were skeletally younger than unaffected groups with statistically significant differences at the age of 10, 12 and 13. (p=0.05).
Conclusion: Young subjects with PDCs showed skeletal maturation delay compared to control group, indicating that skeletal maturation assessment could be one of unexplored predicting factors of a PDC, especially at the age between 10 and 13 years in both genders. Subjects with PDC showed intensive growth spurt after the age of 12 years in females, and after the age of 13 in males. Dental maturation delay showed no statistical significance in PDC prediction.

Introduction

Maturational changes in the morphology of cervical vertebrae in normally growing children are proved to be biological indicators of skeletal maturity. Several authors have assessed modifications in dimension of the cervical vertebrae on lateral radiographs, routinely made in the diagnostic procedure of orthodontic anomalies. Nowadays, this method is the most popular one, since there is no need for taking hand-wrist radiographs (, ). Cervical Vertebral Maturation (CVM) method has proven to be effective in determination of the adolescent growth spurt, hence represents a diagnostic tool mandatory for accurate treatment planning (, ). Demirjian’s method for children’s dental age estimation is based on evaluation of the calcification stage of left mandibular teeth (except third molar). Teeth are given a mark from A to H, indicating the stage of development. (, )

The reported prevalence of palatally displaced canines (PDC) varies from 0.27 to 2.4%, depending on the population (), with the most common crown position placed near the palatal surface of lateral or central incisor (). Furthermore, PDC occurs twice as frequently in females than in males, while bilateral occurrence has been reported to be in the range of 19% to 45% (). Zilberman et al. () have investigated possible correlations between PDC and development delays of the dentition combined with changes in the shape of the lateral incisors, which are known to be four times more frequent in patients with PDC than in the general population.

Although many comparative research of skeletal maturity and dental age have been made (-), the assessment of dental and skeletal age among patients with PDC compared to control groups has not yet been researched. Therefore, the aim of this study was to determine potential associations between dental and skeletal maturation and palatally displaced canines (PDC) considering gender and chronological age.

Material and methods

This research was designed as a case-control study, comprising 246 subjects of both genders, aged 10-16 years (13.1±1.9).

The study group comprised the clinical files, pretreatment dental casts, panoramic and lateral cephalometric radiographs of 43 subjects (15 males and 28 females). It included non-syndromic orthodontic patients diagnosed with PDC (unilateral or bilateral) who were treated at the University Hospital Center Zagreb, Croatia in period from 2016 to 2021.

A control reference sample, randomly selected from orthodontic patients at the same University Clinic, comprised 203 (78 males and 125 females) panoramic and cephalometric radiographs of subjects with normally positioned canines, bilaterally erupted canines as diagnosed from their pretreatment plaster casts. The gender and age of the control group were matched with the sample of the study group. All the investigated subjects (both PDC and controls) were Caucasians.

The chronological age (CA) of the subjects was registered according to the date of the patient's birth until the day the panoramic radiograph was recorded. The taken values were rounded and noted in years and decimal points.

Demirjian’s method for dental age (DA) estimation has been the most commonly used method in scientific research, as well as in clinical practice (). Hence, a comparison of the chronological age and dental age of all subjects was made with the standard charts of Demirjian.

An eight-grade scale from A to H was used and each tooth was assigned with the value that represented its developmental stage. Standard tables, different for each gender, were used to assign the right numeric value to each evaluated stage. The sum was made for all given values, and the result indicated the dental age, derived from standard tables. To minimize the error regarding DA assessment, each panoramic radiograph was analyzed twice by the same investigator (L.L.)

Cervical vertebral maturation was determined on lateral cephalometric radiographs using cervical vertebrae maturation stages (CVS) method (, , ). The study was approved by the Ethics Committee of the University of Zagreb School Of Dental Medicine.

Statistical analysis

A statistical analysis was performed with Statistical Package for Social Sciences (SPSS Inc., Chicago, Illinois, USA) and Statistica 7.1 (StatSoft Inc., Tulsa OK, USA). P values less than 0.05 were considered significant.

To study the differences between the examined groups, the Mann-Whitney and Fisher's exact tests were used. The Spearman rank correlation coefficient (R) was used to assess the association between the CSV (cervical stage), dental calcification stages in both study and control group, regarding gender.

By applying Fisher's r-to-z transformation the z score was used to evaluate the differences between correlation coefficients between subjects and control group regarding gender.

Results

The number and percentage of subjects with PDC regarding gender are presented in Table 1. Fisher's test revealed a statistically significant occurrence in displacement of left maxillary canine in females compared to males (p=0.027), with five times more odds ratio (OR = 4.9; 95% CIL = 1.2 – 19.7).

Table 1

Number and percentage of patients with PDC regarding gender

			Gender
			M	F	Total	Sig.*	OR (95% CIL)
Canine 13	Not Displaced	N	2	10	12
		%	13.3%	35.7%	27.9%
	Displaced	N	13	18	31
		%	86.7%	64.3%	72.1%	0.164	0.3 (0.1-1.5)
Canine 23	Not Displaced	N	11	10	21
		%	73.3%	35.7%	48.8%
	Displaced	N	4	18	22
		%	26.7%	64.3%	51.2%	0.027	4.9 (1.2-19.7)
Single canine		N	13	20	33
		%	86.7%	71.4%	76.7%
Both canines		N	2	8	10
		%	13.3%	28.6%	23.3%	0.451	2.6 (0.5-14.2)
	Total	N	15	28	43
		%	100.0%	100.0%	100.0%

* Fisher's exact test

Scatter plots confirmed that the subjects with PDC were skeletally younger in early ages than the controls in both genders and there was a tendency that the PDC group was growing intensively mature compared to controls (Figure 1).

Figure 1

The relationship between chronological age (CA) and cervical stage (CS) in PDC and control group regarding gender

Although, analysis of the differences between dental and chronological age showed dentally more mature subjects in the control group when compared to subjects in the PDC group (0.5±1.5 years; p=0.016, η2=0.023), these results are not statistically significant (Figure 2). Furthermore, there is a tendency that with growing this difference diminishes.

Figure 2

The relationship between chronological age (CA) and dental age (DA) in PDC and control group regarding gender

Correlations of chronological age with dental and skeletal age, by Spearman correlation, were significant, linear and positive. There is a tendency that the correlation in PDC group was higher between chronological age and skeletal age in males, while in controls between chronological and skeletal age it was similar in both genders. Low levels of correlation coefficient revealed greater variability (Figure 3, Figure 4).

Figure 3

Comparison of dental age and chronological age regarding case and control group

Figure 4

Comparison of cerebral vertebra age and chronological age regarding case and control group

A significantly stronger correlation was present between chronological age and cervical stage in PDC group in males (rho = 0.911) then in controls (rho = 0.516; p = 0.003), which has confirmed the fact that there was a higher biological variability in the control group (Table 2).

Table 2

Correlations of chronological with dental and skeletal age regarding gender in PDC and controls (Spearman rank correlation coefficient)

		Palatally displaced canine		Control
		Chronological age male	Chronological age female	Chronological age male	Chronological age female
Dental age	rho	0.775	0.651	0.744	0.744
	p	0.001	<0.001	<0.001	<0.001
	N	15	28	78	125
Cerebral vertebra	rho	0.911	0.735	0.516	0.584
	p	<0.001	<0.001	<0.001	<0.001
	N	15	28	78	125

In some age groups there was only one subject or few subjects, thus the analysis of the differences regarding gender was not performed. Instead, the scatter plot was done.

Discussion

Early diagnosis of PDC saves the treatment time, surgical procedure, patient discomfort and money. There is much evidence to support a genetic etiology for the palatally displaced canine (PDC) (-) but, apart from agenesis status, there has been no strong predictive factors (, ).

The prevalence of females exhibiting PDC, as a proof of an unequal distribution between genders, is characteristic and well documented in the literature (, ). This research showed no significant differences between males and females in all chronological groups. Female subjects were more affected by left canine displacement than male subjects and the difference was statistically significant (P=0.027) with even five times higher risk (OR = 4.9; 95% CIL = 1, 2- 19.7). Chung and al. () also reported a greater percentage of palatal canine displacement in female subjects with left-side dominance.

Patients with palatally displaced canines didn’t show statistically significant differences in dental development rate when compared to the control group. Różyło-Kalinowska et al. () have found that there was no difference in the dental development rate among patients with palatally displaced canines compared to the patients with buccally displacement canines. The delay in dental development was found in less than half of patients in both groups. Newcomb () also reported a significantly delayed dental development in patients with palatally displaced canines. Becker and Chaushu () reported an abnormal dental development in Caucasian groups of patients with palatal canine displacement. They found a tendency for delayed development with high statistical significance (p=0.001). They have concluded that approximately 50% of patients had delays in the dentition development by a mean of 1.5 years. Sajnani and King () reported that 42.2% of the patients with buccally displaced canines and only 30% of those with a palatally displaced canine showed either a delay in dental development or development coinciding with their chronological age. Most of their patients exhibited accelerated dental development. A possible explanation for different results in the literature, and the one from this study, could be ethnic differences among subjects.

Skeletal age differences were significant in the female group at the age of 10 and 12 and in male group at the age of 12 and 13. Subjects with palatally displaced canines were skeletally younger than those in the control group, with no difference in skeletal maturation in the largest group at the age of 15. Considering the fact that PDC group mature intensively with growing and that skeletal differences diminish with years, skeletal maturation delay in early chronological age can be considered as a predicting factor for palatally displaced canines.

There are many authors who have researched the efficacy of primary canine extraction as a treatment of choice for successful eruption of PDC in young individuals (-). Even though chronological age, suggested for this prevention procedure, coincides with the results of skeletal maturation delay in this research, Benson et al. found no certain evidence that this procedure will help the eruption of PDC without surgical approach ().

A diagnosis of palatally displaced canine is usually determined at age of 13 or higher. Taking into consideration the fact that the case sample consisted of patients aged 10-16, this research included old panoramic and cephalometric radiographs that had been taken for another reason years before palatally displaced canines occurred. Insufficient anamnestic and radiographic history of young children explains a relatively small number of patients that were included in this study. Due to the lack of similar research, these results are not fully comparable, and in the future they need to be extended to a larger sample size. However, they should be taken into consideration when treating patients with PDC since they have shown greater skeletal maturation delays. In terms of that, orthodontists should consider choosing removable orthodontic appliances, quadhelix, transplant arch () and headgear () prior to fixed orthodontic appliances and thus be more effective in achieving positive skeletal growth of the dental arch and, consequently, good treatment results.

Conclusions

PDC subjects are skeletally less mature at younger chronological age, but there is a tendency that they mature more rapidly than non-affected subjects. Skeletal maturation delay in early chronological age should alert clinicians that there is a higher likelihood of experiencing developmental delays and growth deficits such as palatally displaced canines later in life.