A new system for assessment of growth using mandibular canine calcification stages and its correlation with modified MP3 stages.

OBJECTIVE: Orthodontic diagnosis and treatment planning for growing children must involve growth prediction, especially in the treatment of skeletal problems. Studies have shown that a strong association exists between skeletal maturity and dental calcification stages. The present study was therefore taken up to provide a simple and practical method for assessing skeletal maturity using a dental periapical film and standard dental X-ray machine, to compare the developmental stages of the mandibular canine with that of developmental stages of modified MP3 and to find out if any correlation exists, to determine if the developmental stages of the mandibular canine alone can be used as a reliable indicator for assessment of skeletal maturity.
MATERIALS AND METHODS: A total of 160 periapical radiographs, of the mandibular right canine and the MP3 region was taken and assessed according to the Dermirjian's stages of dental calcification and the modified MP3 stages. RESULTS AND DISCUSSION: The correlation coefficient between MP3 stages and developmental stages of mandibular canine was found to be significant in both male and female groups. When the canine calcification stages were compared with the MP3 stages it was found that with the exception of the D stage of canine calcification the remaining stages showed a very high correlation with the modified MP3 stages.
CONCLUSION: The correlation between the mandibular canine calcification stages, and the MP3 stages was found to be significant. The canine calcification could be used as a sole indicator for assessment of skeletal maturity.

In orthodontic diagnosis and treatment planning, assessment of the skeletal age and pubertal growth spurt are of prime importance.[123] It is required to know not only the exact chronological, dental or skeletal age of the patient, but also if the patient will grow during the treatment period and what percentage of growth can be expected during that time.[4] The disadvantages of the routine methods[2] of skeletal maturity were that, they required elaborate equipments, were expensive and the radiation exposure time and dose were high. Krailassiri et al.[5] have reported that tooth calcification stages from panoramic radiographs might be clinically useful as a maturity indicator of the pubertal growth period. Studies by Chertkow and Fatti,[6] on Caucasoid population and Cutinho et al.[7] on American population have shown that relationships between the stages of tooth mineralization of the mandibular canine appear to correlate better with ossification stages than the other teeth. Abdel-Kader assessed the reliability of dental X-ray film in the assessment of the developmental stages of MP3 in the pubertal growth spurt.[2]

This study was, therefore taken up to provide a simple and practical method for assessing skeletal maturity using a dental periapical radiographic film and a standard dental X-ray machine, to compare the developmental stages of the mandibular canine with that of known methods like skeletal developmental stages of MP3[28] and to find out if the developmental stages of the mandibular canine alone can be used as a reliable indicator for assessment of skeletal maturity.

Materials and Methods

Periapical radiographs of 160 subjects (80 males and 80 females) between 8 and 16 years of age were selected.

Criteria for selection

Selection of the subjects was based on the following criteria

The subjects were all South Indians, well-nourished and free of any known serious illness

The subjects had undergone neither previous orthodontic treatment nor extraction of any permanent teeth

The subjects had normal dental conditions, for example, no impaction or transposition of teeth

The subjects had no previous history of trauma or injury to the face and the hand and wrist regions

The patients and parental consent was taken before taking radiographs.

A total of 160 periapical radiographs of the mandibular canines were taken using bisecting angle technique with a standard size (31 mm × 41 mm Kodak) periapical dental X-ray film.

From several investigations, the tooth calcification of homologous teeth was found to be symmetrical; therefore, only right mandibular canine was examined. In the case of any missing right mandibular tooth the corresponding left mandibular tooth was substituted.

A total of 160 periapical radiographs of the MP3 region were taken using the following procedure:

The subject was instructed to place the right hand with the palm downward on a flat table

The middle finger was centered on a 31 mm × 41 mm periapical dental X-ray film, parallel with the long axis of the film

The cone of the dental X-ray machine (70 kVp and 8 mA) was positioned in slight contact with the middle phalanx, perpendicular to the film. Exposure time was 0.4 s.

All radiographs were processed with standardized processing technique and numbered for identification. Radiographs of high clarity and good contrast were used and any patients who presented congenital or acquired abnormalities of the phalanges were eliminated and interpretation of all radiographs were undertaken without referring to clinical data of age of patient.

Subject grouping [Table 1]

Radiographic interpretation of this study was made as per the system developed to interpret skeletal and dental maturation.

The development of the MP3 stages of the hand were evaluated using R. Rajagopal's observational scheme [Chart 1][8]

Chart 1

Modified MP3 stages

The development of mandibular canine was assessed according to Demirjian's stages of dental calcification [Chart 2].[9]

Chart 2

Dental formation stages D.H of mandibular canine

Results

Table 2 gives the frequency distribution of mandibular canine calcification stages with MP3 stages – males. [*MP3 (F + FG + G + H + HI + I)].

Table 2

The frequency distribution of mandibular canine calcification stages with MP3 stages-males

Table 3 gives the frequency distribution of mandibular canine calcification stages with MP3 stages – females.

Table 3

The frequency distribution of mandibular canine calcification stages with MP3 stages-females

Discussion

Skeletal maturity assessment and growth prediction is an important tool in the interceptive orthodontic diagnosis and treatment planning.[10111213] It is also a well-documented fact that, growth modification treatment procedures that control the growth of bones were most effective when started 2 or 3 years prior to the peak in the pubertal growth spurt.[14]

Stages of maturation can be identified by chronological age, sexual maturation characteristics, body height and weight, skeletal development, and dental development age.[1315161718]

It has long been recognized that chronological age has little or no place in the assessment of the maturational status of the child, and it is not a critical factor in the evaluation of the growth potential.[1315161719] Growth prediction based on the appearance of secondary sexual characteristics requires a long observation period and frequent physical examination.[8]

Chapman was the first to use periapical X-ray film to evaluate ossification of the ulnar sesamoid bone as a skeletal maturity marker. Abdel-Kader applied this idea for recording MP3 stages,[2] and studies by R. Rajagopal confirmed that, assessment of remaining pubertal growth can be reliably performed throughout treatment using the modified MP3 stages by taking simple periapical X-rays.[8]

Relationship between skeletal maturation and dental maturation is very poor according to Garn and Lewis,[20] but Sierra,[21] Chertkow[22] and Fatti and Chertkow,[6] have shown strong correlation among dental development and onset of pubertal growth spurt and also said that there were racial variations.

Nolla[23] and Demirjian, Buschang, Tanguay and Patterson,[17] stated that tooth mineralization stages are preferable to ages of tooth eruption in the assessment of dental maturity because mineralization is affected much less by local environmental influences and is measurable over a much longer period of time.

Since, the maturity indicators of brief duration are more informative than those of long duration; it may be advantageous to introduce new intermediate stages.

The purpose of this study was to determine whether the stages of calcification of the mandibular canine could be correlated with the six modified MP3 stages. It was also needed to know if this proposed method of using the developmental stages of the mandibular canine using an intraoral periapical (IOPA) film and standard X-ray machine[19] alone could be used as a single reliable factor in assessing the skeletal maturity.

The age group (8-16 years) selected in this study was based on other maturation studies[24] and as orthodontic treatment is frequently performed at this age group, skeletal age assessment becomes most critical.

The radiographs of 160 healthy children reporting to the Department of Orthodontics and Dentofacial Orthopedics were taken to assess the MP3 stage and development of mandibular right canine in the dental (IOPA) X-ray film.

In this study, radiographic assessment of stages of calcification based on Demirjian's classification[9] was used, which has five different stages from (D - H). It is the most precise and simple method of assessment. Radiographic interpretation of the MP3 region was done using Rajagopal and Kansal,[8] modified MP3 stages.

On comparing the mean age of the male and female subjects in different groups, it was observed that they are not significant (P > 0.05) from each other. Insignificant differences in mean variation indicate that the sample used in this study is homogenous.

The results of this study revealed that the maturation of the middle phalanx of third finger and the mandibular canine progress with advancing age. The skeletal and dental maturation are progressing during the growth period, but at a different rate. Studies by Nanda[25] and Hunter[26] have also reported similar findings.

It was found that at the same chronological age, there was highly significant difference (P < 0.01) in each group. In all groups, MP3 stages were more advanced in females than in males. Similar types of sexual dimorphism regarding the maturational parameters have been earlier reported by Hunter.[26]

On comparing the developmental stages of mandibular right canine in male and female groups, it showed that there was a very highly significant difference in all the groups except in the group (10-12 years) where it was not significant. This indicates an inconsistent sexual dimorphism. Studies byGarn, Lewis and Kerewsky,[20] Carlos and Gittelsohn,[27] Nolla,[23] and Chertkow,[22] also support these results.

The correlation coefficient was studied between MP3 stages and developmental stages of mandibular right canine using Karl Pearson's test. In males, the correlation was not significant (P > 0.05) in the group (8-10 years), in the group (10-12 years) it was significant (P < 0.05) and in the group (12-14 years) and (14-16 years) it was very highly significant (P < 0.001).

In females, the correlation coefficient was highly significant (P < 0.01) in the group (8-10 years) and (10-12 years) and it was very highly significant (P < 0.001) in the groups (12-14 years) and (14-16 years).

The correlation coefficient was studied between MP3 stages and chronological age using Karl Pearson's test. In males, the correlation was found to be not significant (P > 0.05) in the group (8-10 years) and (10-12 years), it was highly significant (P < 0.01) and in the group (12-14 years) it was significant (P < 0.05).

In females, the correlation was found to be significant (P < 0.05) in the group (8-10 years), it was not significant (P < 0.05) in the group (10-12 years) and (14-16 years), whereas in the group (12-14 years) it was highly significant (P < 0.01).

On comparing the developmental stages of mandibular right canine and the chronological age in males and females using Karl Pearson's test, in males the correlation was found to be not significant (P > 0.05) in the group (8-10 years) and (10-12 years), it was highly significant (P < 0.01) in the group (12-14 years) and significant in the group (14-16 years).

In females, correlation was found to be very highly significant (P < 0.001) in the group (8-10 years) and (12-14 years), it was not significant in the group (10-12 years) and (14-16 years).

This indicates that there is an inconsistent correlation between chronological age and dental maturation. Similar findings were reported by Demirjian, Buschang, Tanguay and Patterson.[17]

The association between mandibular canine development and MP3 stages also allows the clinician to more easily identify the early stages of the pubertal growth spurt. By using United States reference data for comparison,[11] the initiation of the spurt is indicated by canine stage F. Stage G, which coincides with the eruption of the canine into the oral cavity, occurs approximately 1 year before the PHV in boys, but occurs 5 months before the PHV in girls. This may reflect hormonal changes which accompany puberty.

The relationship between calcification of the mandibular canine and MP3 stages were quite high when analyzed statistically.

For males [Table 2], the D stage of canine calcification had no subjects from the samples, the E and F stages showed the maximum correlation with the MP3-F stage, while in the G stage a high correlation was seen with the MP3-G stage. In the H stage of mandibular canine calcification, the MP3-I stage was observed to have a high correlation.

For females [Table 3], the correlations were closely tallying as those of the males. Here again, the D stage of mandibular canine calcification had no subjects from the samples, the E and F stages showed maximum correlation with the MP3-F stage. The G stage seemed to show a high correlation with the MP3-G stage and the H stage closely related with the MP3-I stage.

These indicate that in both males and females, the D stage of canine calcification had no subjects in the MP3 stages, while the remaining stages of canine calcification showed high correlations with the MP3 stages in both genders.

Conclusion

From this study, the following conclusions can be drawn:

The correlation between canine calcification stages and MP3 stages was found to be of high statistical significance.

The developmental stages of the mandibular canine could be used very reliably as a sole indicator in assessing the skeletal maturity.

The stage E and stage F of mandibular canine calcification coincided with the MP3-F stage indicating 80-100% of pubertal growth remaining

The stage G of mandibular canine calcification coincided with the MP3-G stage indicating 25-65% of pubertal growth remaining

The stage H of mandibular canine calcification coincided with the MP3-I stage indicating completion of pubertal growth spurt

The proposed method of assessing the skeletal maturity using a standard sized IOPA film and a standard dental X-ray machine was found to be simple and practical.

Table 1

Subject grouping