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Longitudinal study of relative growth ratesof the maxilla and the mandible accordingto quantitative cervical vertebral maturation

Lili Chen, Jiarong Liu, Tianmin Xu, and Jiuxiang Lin

Wuhan and Beijing, China

Introduction: The purpose of this study was to in-vestigate the relative growth rates (RGR) of the maxillaand the mandible according to quantitative cervical ver-tebral maturation (QCVM) of adolescents with normalocclusion.

Methods: Mixed longitudinal data were used. Thesample included 87 adolescents (32 boys, 55 girls)from 8 to 18 years of age with normal occlusion,selected from 901 candidates. Sequential lateral cephalo-grams and hand-wrist films were taken once a year for 6consecutive years. The growth magnitude (GM) andRGR of the maxilla and the mandible were measuredand analyzed.

Results: GM and RGR were not always consistent,because subjects had different periods of time betweenthe QCVM stages. GM was not as reliable as RGR.RGR had no significant sex differences in the maxillaand the mandible, in spite of different deceleratingcurves. However, statistically significant sex differenceswere found in the GM of mandibular measurements.The greatest growth potentials were not synchronizedbetween the maxilla and the mandible. For both sexes,the greatest RGR of maxillary length and height wasin QCVM stage I; then, deceleration occurred. Thegreatest RGR of mandibular length and height was inQCVM stage II, and the next largest was in QCVMstage I.

Conclusions: Understanding the RGR can providereferences for orthodontic treatment and orthognathicsurgery.

Read the full text online at: www.ajodo.org,pages 736.e1-736.e8.

Am J Orthod Dentofacial Orthop 2010;137:736-7

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Copyright � 2010 by the American Association of Orthodontists.

doi:10.1016/j.ajodo.2010.02.015

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EDITOR’S COMMENT

During adolescence, growth rates accelerate untilreaching a peak velocity, and then they decelerate untiladulthood. Practitioners are aware of the marked indi-vidual variations in the start, duration, rate, and amountof this growth. Predicting craniofacial growth is a majorconcern to many orthodontists. To evaluate the rates ofmaxillary and mandibular growth in the differentgrowth stages, a system of quantitative cervical verte-bral maturation (QCVM) was proposed by Chen et al(Quantitative cervical vertebral maturation assessmentin adolescents with normal occlusion: a mixed longitu-dinal study. Am J Orthod Dentofacial Orthop2008;134:720.e1-7). Their methodology involvesidentifying specific maturational stages during theadolescent growth period. With that earlier work asa background, the purpose of this study was to providean accurate index of acceleration and deceleration of themaxillary and mandibular growth rates, comparingthem with the growth magnitude.

These researchers tracked growth of the maxilla andthe mandible over a 6-year period, correlating the rela-tive growth rates with the CVM indicators of Fishman(modified). Growth changes over varying periods oftime were converted to annual rates. Interestingly,growth magnitude and relative growth rates were not al-ways consistent. But of greatest interest to clinicians isthe finding that the periods of greatest growth were notsynchronized between the maxilla and the mandible.The greatest relative growth rate of maxillary lengthand height was in QCVM stage I, whereas, in the man-dible, the greatest rate was in QCVM stage II. There-fore, the authors concluded that maxillary protractionto treat maxillary deficiency would be more effectivewhen started at an early skeletal developmental phaseor in QCVM stage I.

Despite the publication of new articles reporting thevalue of skeletal age assessment by CVM, the factremains that vertebral shape is strongly correlated toskeletal age by assigning patients to broad categories in-stead of providing precise time estimates. Because thiswas a mixed longitudinal study that included the whole

Fig 5. RGR of Ar-Gn according to QCVM.

Fig 6. RGR of ANS-PNS t SN’ and Ar-Gn.

Fig 4. RGR of ANS-PNS t SN’ according to QCVM.

American Journal of Orthodontics and Dentofacial Orthopedics Chen et al 737Volume 137, Number 6

period of growth and development and looked retro-spectively at growth with headfilms taken yearly, moreinformation was gathered than would ever be possiblewith only 1 set of diagnostic records. Research findingsare beginning to show that, without long-term records,predicting a patient’s peak growth rate from 1 headfilmis not much better than simply asking the patient’s age.

Q & ATurpin: What motivated you initially to tackle thisproject?

Lin: Skeletal growth prediction in orthodontics,particularly in orthopedic treatment, is critical. Butinvestigations in this field are limited because ofthe problems of longitudinal radiographic record-ings. We had the precious mixed longitudinal dataof normal occlusion in China including the wholeperiod of growth and development; therefore, itwas feasible to provide some useful references fororthodontic treatment and orthognathic surgery.

Turpin: Do you plan additional studies related to theeffectiveness of skeletal growth prediction?

Lin: We would like to have skeletal growth predic-tion as our major research interest. We have approx-imately 10 articles in this regard published or in pressin various journals so far. Dr Lili Chen received

a grant from the National Natural Science Founda-tion of China in this field. More studies should beconducted.

Turpin: Do you think newer forms of 3-dimensionalimaging will be of any value in this regard?

Lin: In my opinion, the newer forms of 3-dimen-sional imaging are valuable in many fields. However,how and to what extent 3-dimensional imaging andskeletal growth prediction can be combined stillneeds to be carefully thought out.