Diagnostic assessment of skeletal maturity through dental maturation in Hispanic growing individuals

INTRODUCTION

The assessment of skeletal maturation is a relevant factor in treatment planning for several orthodontic and orthopedic intervention modalities.^[1,2] Despite it has been proven that chronological age has a high correlation with skeletal maturity when measured on the average patient, this indicator is not accurate for the whole population since body mass index, ethnic and metabolic factors may predispose an early or late skeletal development. Hence, it is necessary to manage other indicators for a precise determination of the growth spurt.^[3-7]

One of the most common ways of determining the skeletal maturation is the hand and wrist ossification method.^[1] A drawback of this technique is that patients need to be exposed to additional radiation,^[8,9] so to avoid this exposure, some authors have proposed to assess skeletal maturation using dental and osseous structures, such as the cervical vertebrae, which are available on routine orthodontic radiographs.^[10-12]

Another method for skeletal maturation determination is through the study of dental maturation. Demirjian et al. method, first described in 1973, has been widely used for this purpose given its simplicity and ease of use.^[13-15] As well, different authors have modified it to increase its clinical efficiency, obtaining equivalent results regarding its ability to determine skeletal maturation.^[16-20] On the other hand, cervical vertebral maturation assessment has become an accepted alternative diagnostic method to hand–wrist analysis for the determination of skeletal maturation, allowing a reduction of radiation exposure since this method is applied using lateral cephalometric radiographs.^[10,21-23] Skeletal and dental maturation indices have been found to be correlated. One of the strongest correlations between dental and cervical maturation has been found with the left mandibular second molar as assessed on the panoramic X-ray.^[24-28] Besides, If an orthodontic/orthopedic population of growing children is to be evaluated, the observation of this tooth seems appropriate due to its long formation time span and calcification chronology.

One key aspect of establishing a diagnostic test based on panoramic films is that this radiographic examination is broadly ordered by general practitioners during their routine patient examination. This means that general practitioners would have the opportunity to assess skeletal maturation based on panoramic radiographs without asking for an additional X-ray and, consequently, allowing them timely referral of their patients to the orthodontist if deemed necessary.

Although high levels of correlation have been reported between dental and skeletal maturation,^{[12,16,17,29]} this relationship has not been systematically analyzed in Hispano-Americans, an ethnically different population from those previously reported. This becomes a relevant issue, as dental development follows a differential timing among different ethnic groups.^[29] Therefore, diagnostic performance data are missing regarding the relationship between dental and skeletal maturation in South American Hispanic population.

The present study aimed at exploring dental maturation assessed at the lower left second molar as a diagnostic test for skeletal maturation in a sample of growing individuals in Chile.

MATERIALS AND METHODS

RESULTS

Intraobserver agreement was calculated using the kappa statistic. For dental maturation, kappa value was 1.00, whereas for cervical vertebral maturation, kappa value was 0.94.

Six hundred and fifty-seven patients were included in the sample. Three hundred and twenty-six patients (49.62%) were female and 331 (50.38%) were male. 81.58% presented a prepubertal maturational stage (CVS 1–3). Descriptive data regarding the cervical maturational status of the sample are presented in Table 3.

Spearman’s correlation (r) shows a statistically significant correlation for dental and cervical maturation for both genders, which is stronger in females (r = 0.7334, P < 0.001) than in males (r = 0.6, P < 0.001).

The area under the ROC curves, representing in this study the probability of correctly classifying a pair of individuals in pre- and post-pubertal stages of development, were assessed using stages CVS 1, 2, and 3 as pregrowth spurt and stages CVS 4, 5, and 6 as postgrowth spurt. Our results indicated an area under the ROC curve of 0.896 for females and 0.914 for males.

The analyses of cutoffs for sensitivity and specificity for each gender are seen in Figure 1. This test has a sensitivity of 87.21% and a specificity of 82.92% for women and a sensitivity of 97.1% and specificity of 72.3% for men. According to this values of specificity and sensitivity, the presence of dental Stage F represents, for both genders, the best cutoff point for assessing when the postpubertal growth spurt phase starts.

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Figure 1

Receiver operating characteristic curves showing probability cutoffs for females and males

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Using the dental Stage F as the cutoff point, the PPV was found to be 94.8% for females and 99.5% for males. The assessment of this diagnostic test for each gender is summarized in Table 4. Positive likelihood ratios for females and males were 5 and 4, respectively, whereas negative likelihood ratios for females and males were 0.15 and 0.04, respectively.

DISCUSSION

In this study, dental maturation assessment was analyzed as a diagnostic test of skeletal maturation. For that, the correlation between dental and cervical maturity was initially assessed. As expected, a significant positive correlation was obtained for both genders, which is consistent with correlations found in several other publications.^{[16,17,24,26,27,31-33]}

The relevance of skeletal maturity in dentofacial orthopedic treatment planning is widely recognized. For example, it is clinically beneficial to identify if a Class II individual seeking orthodontic treatment is in a pregrowth spurt phase.^[34] This is why the cutoff point was set favoring a good sensitivity over specificity, where the patients who are diagnosed as postgrowth spurt, are so indeed. This offers relevant information if dentofacial orthopedic procedures are to be carried out. The reported areas under the ROC curve indicate that this test is accurate for both females and males.^[35]

In the present study, the best dental maturity indicator for the beginning of a postgrowth spurt phase was found to be Demirjian’s dental Stage F for both genders, as identified at the left second mandibular molar. This means that between dental Stages A and E, an individual would be in a pregrowth spurt phase and during Stages F through H, in a postgrowth spurt phase. In practice, once the left mandibular second molar has developed its furcation enough to show the radicular shape and the root length is equal or greater than the crown height, the patient has probably already surpassed the peak of pubertal growth speed.

According to our data [Table 4] regarding the assessment of this diagnostic test, the prevalence represents the probability of finding an individual aged 5–15 years old that already has gone through his or her growth spurt, being 11% and 26% for females and males, respectively. Sensitivity, which is here the ability to identify an individual in a postpubertal growth spurt stage when having a dental Stage F, G, or H is 87% for females and 97.1% for males. Specificity, the ability to identify that has not gone through pubertal growth spurt yet when having a dental Stage A–E, is 82.9% for females and 72.3% for males.

PPV is defined as the probability of being healthy when the diagnostic test gave a negative result.^[36] In this study, it means that the chances of a patient not being in a postgrowth spurt yet while having a dental Stage A to E is high. This is relevant because knowing accurately when the patient has not gone through his or her growth spurt, improves dentofacial orthopedic treatment planning and performance.

Others studies about skeletal spurt assessment have stated that for positive likelihood ratios, a threshold equal to or >10 must be reached to establish that a diagnostic test is reliable.^[29,37] Following this principle, our test would not be diagnostically reliable. Other authors,^[38] however, propose that this is an arbitrary threshold and we should not ignore lower than ten likelihood ratios, especially when considering that the test we are studying is a screening tool proposed for helping general practitioners on their way for a timely referral to the orthodontist.

Although the use of dental maturity assessment-based Demirjian’s method for skeletal assessment has been questioned beyond the prepubertal phase,^[29] our results suggest that this method is useful for identifying whether a patient has not gone through the growth spurt yet. This can enable the use of treatment strategies that benefit from the inclusion of this accelerated skeletal growth, as Class II dentofacial orthopedic interventions.^[30] The evaluation of dental maturity stages in panoramic X-rays could expand the role of the dental practitioner in the context of the treatment of growing individuals, favoring the timely referral to the orthodontic specialist.

Although the present study shows that dental maturation evaluation is highly correlated with CVM, displaying good performance as a diagnostic test, these results may be cautiously interpreted as they were obtained from a cross-sectional sample of consecutively radiographed individuals. Certainly, the use of longitudinal records may improve the study model to allow a better understanding of dental maturation analysis relative to other skeletal maturation indicators.

CONCLUSIONS

Both the CVM and the Demirjian’s method for dental maturation may be applicable in practice. There is a strong correlation between dental and cervical maturation. Dental Stage F, measured in left mandibular second molar, can be used as a developmental indicator of the beginning of a postpubertal growth spurt phase which shows a good sensitivity and specificity. Dental maturation can be useful to determine whether the patient has started a postpubertal peak growth stage.