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phase that coincides with the peak in mandibulargrowth in the majority of subjects.

2. No need for additional x-ray exposure.3. Ease in recording.4. Consistency in the interpretation of the data. The inter-

examiner error in the appraisal of the dened stages orphases should be as low as possible.

5. Usefulness for the anticipation of the occurrence of thepeak. Themethod shouldpresent with a denable stageor phase that occurs before the peak in mandibulargrowth in the majority of subjects.

The main features of the Cervical Vertebral Maturation(CVM) method as described previously by Franchi and co-workers18 included:

1. In nearly 95% of North American subjects, a growthinterval in CVM coincides with the pubertal peak inboth mandibular growth and body height.

2. Thecervical vertebraeareavailable on thelateral cepha-logram that is used routinely for orthodontic diagnosisand treatment planning.

3. The appraisal of the shape of the cervical vertebrae isstraightforward.

4. The reproducibility of classifying CVM stages is high( 98% by trained examiners).

5. The method is useful for the anticipation of the puber-tal peak in mandibular growth.

A subsequent study by our group 19 provided a few im-provements of theoriginal CVM analysis to make themethodeasier and applicable to the vast majority of patients:

1. A more limited number of vertebral bodies was used toperform the staging (as suggested by Hassel andFarman20). In particular, the method included onlythose cervical vertebrae (C2, C3, and C4) that can bevisualized when a protective radiation collar is worn bythe patient.

2. Denitions of stages were not based on a comparativeassessment of between-stage changes, so that stages canbe identied easily on a single cephalogram.

A series of investigations performed in different parts of theworld have conrmed the validity of the CVM method,mostly by comparing it with the hand and wrist method.Pancherz and Szyska found that the cervical vertebral matu-ration method has level of reliability comparable to the handand wrist method. 21 By replacing the hand-wrist methodwith the CVM method, an additional radiograph can beavoided, thus reducing the patients total radiation dose.Grave and Townsend also have conrmed the validity of theCVM method in Australian aborigines. 22

The aim of the present article is to present a further mod-ied and rened version of the CVM method and its validityfor the appraisal of mandibular skeletal maturity in the indi-vidual patient in light of the ndings of recent studies inwhich the CVM method has been used to assess optimal

timing for the treatment of malocclusions in the transverse,sagittal, and vertical planes of space.

Subjects and MethodsThe total sample (n 706) that comprises the cephalometricles of theUniversity of Michigan Elementary andSecondarySchool Growth Study was evaluated. 23 Due to the longitudi-nal nature and aim of the present investigation, subjects withless than six consecutive annual cephalometric observations(n 492) were excluded from the study. Total mandibularlength (Co-Gn) was measured on the longitudinal sets of lateral cephalograms for each of the 214 remaining subjectsat yearly intervals. The lateral cephalograms were analyzedby means of a digitizing tablet (Numonics, Lansdale, PA) anddigitizing software (Viewbox, version 3.0, D. Halazonetis,

Athens, Greece). The maximum increase in Co-Gn betweentwo consecutive annual cephalograms was used to dene thepeak in mandibular growth at puberty in the individual sub-

jects. Two consecutive cephalograms comprising the intervalof maximum mandibular growth, together with two earlierconsecutive cephalograms and two later consecutive cepha-

lograms, had to be available for each subject and were in-cluded in the study. This limited the investigation to 30 sub-

jects (18 males, 12 females).The morphology of the bodies of the second (C2 odon-

toid process), third (C3), and fourth (C4) cervical vertebraewere analyzed in the six consecutive annual observations (T 1through T 6). The analysis consisted of both visual and ceph-alometric appraisals of morphological characteristics of thecervical vertebrae.

Visual analysis. The morphology of the three cervical verte-brae (C2, C3, C4) on the six consecutive cephalograms (T 1through T 6) was evaluated by visual inspection. Two investi-gators (LF and TB) performed the appraisal independently.The percentage of interexaminer agreement was 96.7%. Twosets of variables were analyzed:

1. Presence or absence of a concavity at the lower borderof the body of C2, C3, and C4; and

2. Shape of the body of C3and C4. Four basic shapeswereconsidered:

trapezoid (the superior border is tapered from posterior toanterior);

rectangular horizontal (the heights of the posterior andanterior borders areequal; thesuperior and inferior bor-ders are longer than the anterior and posterior borders);

squared (the posterior, superior, anterior, and inferior bor-ders are equal); and

rectangular vertical (the posterior and anterior borders arelonger than the superior and inferior borders).

Cephalometric analysis. On the lateral cephalograms, thefollowing points for the description of the morphologic char-acteristics of the cervical vertebral bodies were traced anddigitized (Fig 1):

C2p, C2 m, C2a: the most posterior, the deepest, and the

most anterior points on the lower border of the body of C2.

120 T. Baccetti, L. Franchi, and J.A. McNamara


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C3up, C3ua: the most superior points of the posterior andanterior borders of the body of C3.

C3lp, C3 m, C3la: the most posterior, the deepest, and themost anterior points on the lower border of the body of C3.

C4up, C4ua: the most superior points of the posterior andanterior borders of the body of C4.

C4lp, C4 m, C4la: the most posterior, the deepest, and themost anterior points on the lower border of the body of C4.

For the location of landmarks, the indications described byHellsing were adopted partially. 24 With the aid of these land-marks, the following measurements were performed:

C2Conc: a measure of the concavity depth at the lowerborder of C2 (distance from the line connecting C2pand C2a to the deepest point on the lower border of the

vertebra, C2 m).C3Conc: a measure of the concavity depth at the lower

border of C3 (distance from the line connecting C3lpand C3la to the deepest point on the lower border of thevertebra, C3 m).

C4Conc: a measure of the concavity depth at the lowerborder of C4 (distance from the line connecting C4lpand C4la to the deepest point on the lower border of thevertebra, C4 m).

C3BAR: ratio between the length of the base (distanceC3lp-C3la) and the anterior height (distance C3ua-C3la) of the body of C3.

C3PAR: ratio between the posterior (distance C3up-C3lp)andanterior (distanceC3ua-C3la) heights of thebody of C3.

C4BAR: ratio between the length of the base (distanceC4lp-C4la) and the anterior height (distance C4ua-C4la) of the body of C4.

C4PAR: ratio between the posterior (distance C4up-C4lp)andanterior (distanceC4ua-C4la) heights of thebody of C4.

Statistical analysis. The signicance of the prevalence ratesfor the morphologic characteristics of the cervical vertebraewas evaluated at each observation time by means of the chi-squared test with Yates correction ( P 0.05). Descriptivestatistics were obtained for total mandibular length and forvertebral cephalometric measures at each of the six consecu-tive observations (T 1 through T 6). The differences betweenthe mean values for all the computed variables at the sixconsecutive stages were tested for signicance by means of

ANOVA for repeated measurements with post hoc Scheffstest (P 0.05).

The cephalometric measurements of the bodies of the cer-vical vertebrae at each interval between consecutive cephalo-grams were analyzed by means of a multivariate statisticalapproach, discriminant analysis, to identify those vertebralmorphologic variables mostly accounting for the differencesbetween two consecutive observations. A stepwise variableselection (forward selection procedure) was performed withthe goal of obtaining a model with the smallest set of signif-icant cephalometric variables ( F to enter and to remove 4).Finally, the classifying power of selected cephalometric vari-ables was tested. All statistical computations were performedby means of computer software (SPSS for Windows, version10.0.0, SPSS, Inc., Chicago, IL).

ResultsThe ndings of the visual analysis of the morphologic char-acteristics of cervical vertebrae (C2, C3, C4) are reported inTable 1 . The features of the examined vertebrae at the sixconsecutive observations can be summarized as follows:

T1. The lower border of C2 is at in the vast majority of subjects at this stage; a concavity is evident at the lowerborder of C2 in only 7% of the individuals examined, a per-centage that is not signicant. The concavity is absent at the

lower borders of both C3and C4in100% of the subjects. Thebodies of both C3 and C4 are trapezoid in shape.

Figure 1 Cephalometric landmarks for the quantitative analysis of the morphologic characteristics of the vertebral bodies of C2, C3,and C4.

The CVM method and treatment timing 121


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T 2. A concavity is present at the lower border of C2 in 80%of the subjects. The observation at T 2 is characterized also bythe absence of a concavity at the lower borders of C3 (withthenonsignicant exceptionof 7% of thesubjects) andof C4.Both C3 and C4 still are trapezoid in shape, with the nonsig-nicant exceptions of 3% and 13% of the subjects showingrectangular horizontal bodies for C3 and C4, respectively.

T 3. A concavity is present at the lower border of C2(100% of the subjects) and of C3 (with the nonsignicant exception of 7% of the subjects). No concavity is present at the lowerborderof C4 (with thenonsignicant exception of 10% of thecases). The shape of both C3 and C4 may be either trapezoidor rectangular horizontal.

T4. This observation is characterized by the presence of aconcavity at the lower borders of C2, C3 (with the nonsignif-icant exception of 7% of the cases), and C4 (with the nonsig-nicant exception of 13% of the cases). The bodies of both C3and C4 now are rectangular horizontal in shape (100% of thesubjects).

T5. A concavity is present at the lower borders of C2, C3(with the nonsignicant exception of 3% of the cases), andC4 (with the nonsignicant exception of 3% of the cases).The body of C3 is rectangular horizontal in 40% of the casesand squared in the remaining subjects. The body of C4 isrectangular horizontal in 47% of the cases and squared in theremaining subjects.

T6. A concavity is present at the lower borders of all the threeexamined cervical vertebrae. The body of C3 is squared in50% of the cases and rectangular vertical in the remaining50% of the cases. The body of C4 is squared in 53% of thecases and rectangular vertical in the remaining subjects.

Descriptive statistics for the cephalometric measurementsof vertebral morphologic characteristics are reported in Table2, together with the statistical comparisons between consec-utive observations. No signicant differences for any of themeasurements were assessed between T 1 and T 2 with theexception of a signicant increase in the depth of the concav-ity at the lower border of the second cervical vertebra(C2Conc). The depth of the concavities at the lower bordersof both thesecond(C2Conc) andthe third (C3Conc) cervicalvertebra is signicantly greater at T 3 when compared with T 2.In the transition from T 2 to T3, the height of the anteriorborder of both C3 and C4 increases signicantly, thus lead-ing to signicant decrements in the ratio between the heightsof the posterior and anterior borders of the vertebral bodies(C3PAR and C4PAR).

At T4, the depth of the concavity at the lower border of C4(C4Conc) becomes signicantly greater than at T 3. In thetransition from T 3 to T4, the height of the anterior borders of both C3 and C4 increases signicantly again, thus leading tosignicant decreases both in the ratio between the heights of the posterior and anterior borders of the vertebral bodies(C3PAR and C4PAR) and in the ratio between the length of

the base and the anterior height of the vertebral bodies(C3BAR and C4BAR). On average, C3PAR and C4PAR now T a b l e

1

R e s u l t s o f

Q u a

l i t a t i v e

A n a

l y s i s o f

C e r v i c a

l V e r t e b r a l

C h a r a c t e r i s t i c s a t

t h e

S i x C o n s e c u t i v e

O b s e r v a t i o n s

T 1

T 2

T 3

T 4

T 5

T 6

Y e s

N o

Y e s

N o

Y e s

N o

Y e s

N o

Y e s

N o

Y e s

N o

C o n c a v i t y a t t h e

l o w e r

b o r

d e r o f

C 2

2 ( 6

. 7 % ) 2 8 ( 9 3

. 3 % ) 2 4 ( 8 0 % )

6 ( 2 0 % )

3 0 ( 1 0 0 % )

0 ( 0 % )

3 0 ( 1 0 0 % )

0 ( 0 % )

3 0 ( 1 0 0 % )

0 ( 0 % )

3 0 ( 1 0 0 % )

0 ( 0 % )


l o w e r

b o r

d e r o f

C 3

0 ( 0 % )

3 0 ( 1 0 0 % ) 2 ( 6

. 7 % )

2 8 ( 9 3 . 3 % ) 2 8 ( 9 3 . 3 % )

2 ( 6

. 7 % )

2 8 ( 9 3 . 3 % )

2 ( 6 . 7 % )

2 9 ( 9 6 . 7 % )

1 ( 3

. 3 % )

3 0 ( 1 0 0 % )

0 ( 0 % )


l o w e r

b o r

d e r o f

C 4

0 ( 0 % )

3 0 ( 1 0 0 % ) 0 ( 0 % )

3 0 ( 1 0 0 % )

3 ( 1 0 % )

2 7 ( 9 0 % )

2 6 ( 8 6 . 7 % )

4 ( 1 3

. 3 % ) 2 9 ( 9 6 . 7 % )

1 ( 3

. 3 % )

3 0 ( 1 0 0 % )

0 ( 0 % )

C 3 s h a p e : t r a p e z o i

d

3 0 ( 1 0 0 % )

0 ( 0 % )

2 9 ( 9 6 . 7 % )

1 ( 3

. 3 % )

2 3 ( 7 6 . 7 % )

7 ( 2 3 . 3 % )

0 ( 0 % )

3 0 ( 1 0 0 % )

0 ( 0 % )

3 0 ( 1 0 0 % )

0 ( 0 % )

3 0 ( 1 0 0 % )

C 4 s h a p e : t r a p e z o i

d

3 0 ( 1 0 0 % )

0 ( 0 % )

2 6 ( 8 6 . 7 % )

4 ( 1 3 . 3 % ) 1 5 ( 5 0 % )

1 5 ( 5 0 % )

0 ( 0 % )

3 0 ( 1 0 0 % )

0 ( 0 % )

3 0 ( 1 0 0 % )

0 ( 0 % )

3 0 ( 1 0 0 % )

C 3 s h a p e : r e c t a n g u

l a r

h o r i z

.

0 ( 0 % )

3 0 ( 1 0 0 % ) 1 ( 3

. 3 % )

2 9 ( 9 6 . 7 % )

7 ( 2 3 . 3 % ) 2 3 ( 7 6 . 7 % ) 3 0 ( 1 0 0 % )

0 ( 0 % )

1 2 ( 4 0 % )

1 8 ( 6 0 % )

0 ( 0 % )

3 0 ( 1 0 0 % )


l a r

h o r i z

.

0 ( 0 % )

3 0 ( 1 0 0 % ) 4 ( 1 3 . 3 % ) 2 6 ( 8 6 . 7 % ) 1 5 ( 5 0 % )

1 5 ( 5 0 % )

3 0 ( 1 0 0 % )

0 ( 0 % )

1 4 ( 4 6 . 7 % ) 1 6 ( 5 3 . 3 % ) 0 ( 0 % )

3 0 ( 1 0 0 % )

C 3 s h a p e : s q u a r e

d

0 ( 0 % )

3 0 ( 1 0 0 % ) 0 ( 0 % )

3 0 ( 1 0 0 % )

0 ( 0 % )

3 0 ( 1 0 0 % )

0 ( 0 % )

3 0 ( 1 0 0 % ) 1 8 ( 6 0 % )

1 2 ( 4 0 % )

1 5 ( 5 0 % )

1 5 ( 5 0 % )

C 4 s h a p e : s q u a r e

d

0 ( 0 % )

3 0 ( 1 0 0 % ) 0 ( 0 % )

3 0 ( 1 0 0 % )

0 ( 0 % )

3 0 ( 1 0 0 % )

0 ( 0 % )

3 0 ( 1 0 0 % ) 1 6 ( 5 3 . 3 % ) 1 4 ( 4 6 . 7 % ) 1 6 ( 5 3 . 3 % ) 1 4 ( 4 6 . 7 % )


l a r

v e r t .

0 ( 0 % )

3 0 ( 1 0 0 % ) 0 ( 0 % )

3 0 ( 1 0 0 % )

0 ( 0 % )

3 0 ( 1 0 0 % )

0 ( 0 % )

3 0 ( 1 0 0 % )

0 ( 0 % )

3 0 ( 1 0 0 % ) 1 5 ( 5 0 % )

1 5 ( 5 0 % )


l a r

V e r t .

0 ( 0 % )

3 0 ( 1 0 0 % ) 0 ( 0 % )

3 0 ( 1 0 0 % )

0 ( 0 % )

3 0 ( 1 0 0 % )

0 ( 0 % )

3 0 ( 1 0 0 % )

0 ( 0 % )

3 0 ( 1 0 0 % ) 1 4 ( 4 6 . 7 % ) 1 6 ( 5 3 . 3 % )



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have a ratio of approximately 1:1, an indication that both C3and C4 vertebral bodies are rectangular horizontal in shape.

T5 and T 6 are characterized by decrements of the ratiobetween the length of the base and the anterior height of thevertebral bodies (C3BAR and C4BAR). The mean values forthese measurements indicate that the vertebral bodies be-come progressively more squared in shape.At T 6, one third of the cases show a rectangular vertical shape of one or both C3and C4 vertebral bodies.

Discriminant analysis revealed that the forming concavityat the lower border of C2 can account for 80% of the differ-ences between T 1 and T 2. The depth of C3Conc becomes thediscriminant variable between T 2 and T 3 with a classifyingpower of 75%. The difference in the posteroanterior ratio of C3 (C3PAR) together with the depth of the concavity at thelower border of C4 (C4Conc) are the discriminant factorsbetween T 3 and T 4 (classifying power equal to 85%). C3PAR in association with both the ratio between the length of thebase and the anterior height of C3 (C3BAR) and C4Conc are

able to discriminate between T 4 and T 5 in 88% of the cases.The ratios for C3 (C3BAR and C3PAR) together with thedepth of the concavity at the lower border of C2 (C2Conc)are the discriminant variables between T 5 and T 6 in 80% of the cases.

DiscussionThe modications in the size and shape of the cervical verte-brae in growing subjects have gained increasing interest dur-ing thepast fewdecades as a biological indicator of individualskeletal maturity. One of the main reasons for the increasingpopularity of the method is that the analysis of cervical ver-tebral maturation is performed on the lateral cephalogram, atype of lm used routinely in orthodontic diagnosis. Theobjective of the present investigation was to provide a rene-ment of the method through the denition of six stages (cer-vical stages 1 to 6) for a more practical application in dento-facial orthopedics, and more specically:

a direct appraisal of the skeletal maturity of the mandiblein relation to the morphological features of the cervicalvertebrae;

an evaluation of the morphological features of the cervicalvertebralbodies restricted to those that arevisible on the

lateral cephalogram even when a protective collar isworn, as originally proposed by Hassel and Farman 20;a denition of the cervical vertebral morphology at each

developmental stage that allows the clinician to applytheCVM methodon thebasisof theinformation derivedfrom a single cephalogram. The assessment of individ-ual stages in cervical vertebral maturation through thecomparative analysis of between-stage changes shouldbe avoided.

The anatomical features of the second (odontoid process),third, and fourth cervical vertebrae were evaluated here asvisualized on lateral cephalograms in a time interval ranging

on average from 2 years before to 2 years after the peak inmandibular growth. The description of the consecutive T a b l e

2

R e s u l t s o f

Q u a n t i t a t i v e

A n a

l y s i s :

D e s c r i p t i v e

S t a t i s t i c s a n

d S t a t i s t i c a l

C o m p a r i s o n s

( A N O V A f o r

R e p e a t e d

M e a s u r e m e n t s w i t h P o s t H o c

S c h e f

f e s t e s t

) o n t h e

M e a s u r e m e n t s a t t h e

S i x C o n s e c u t i v e

C e p

h a l o m e t r i c

O b s e r v a t i o n s .

T 1

T 2

T 3

T 4

T 5

T 6

M e a n

S D

S E

M e a n

S D

S E

M e a n

S D

S E

M e a n

S D

S E

M e a n

S D

S E

M e a n

S D

S E

A g e

( m o n t h s )

1 0 4 . 6 7

1 5 . 1

2

2 . 7 6

1 1 6 . 4 0

1 4 . 8

4

2 . 7 1

1 2 8 . 7 3

1 4 . 9

9

2 . 7 4

1 4 1 . 1 7

1 4 . 4

2

2 . 6 3

1 5 3 . 3 0

1 4 . 4

1

2 . 6 3

1 6 6 . 0

0

1 3 . 8

3

2 . 5 3

C o - G n

( m m

)

1 0 7 . 8 5

5 . 3 3

0 . 9 7

1 1 0 . 3 2

5 . 6 8

1 . 0 4

1 1 2 . 6 3

5 . 7 8

1 . 0 6

1 1 8 . 0 5 *

5 . 8 3

1 . 0 6

1 1 9 . 6 3

5 . 9 1

1 . 0 8

1 2 1 . 7

7

5 . 9 3

1 . 0 8

C 2 C

o n c

( m m

)

0 . 4 4

0 . 4 6

0 . 0 8

0 . 7 6 *

0 . 4 9

0 . 0 9

1 . 1 5 *

0 . 4 4

0 . 0 8

1 . 5 8 *

0 . 3 7

0 . 0 7

1 . 9 1

0 . 4 0

0 . 0 7

2 . 2

3

0 . 4 8

0 . 0 9

C 3 C

o n c

( m m

)

0 . 0 1

0 . 4 1

0 . 0 7

0 . 3 6

0 . 4 9

0 . 0 9

0 . 9 5 *

0 . 5 3

0 . 1 0

1 . 3 6

0 . 6 4

0 . 1 2

1 . 8 5

0 . 6 0

0 . 1 1

2 . 4

0 *

0 . 6 8

0 . 1 2

C 4 C

o n c

( m m

)

0 . 0 3

0 . 3 1

0 . 0 6

0 . 1 2

0 . 2 9

0 . 0 5

0 . 3 1

0 . 3 9

0 . 0 7

1 . 0 7 *

0 . 5 3

0 . 1 0

1 . 7 7 *

0 . 6 0

0 . 1 1

2 . 2

8 *

0 . 6 3

0 . 1 1

C 3 P A R ( r a t i o )

1 . 3 5

0 . 1 5

0 . 0 3

1 . 2 6

0 . 1 6

0 . 0 3

1 . 1 6 *

0 . 1 2

0 . 0 2

0 . 9 8 *

0 . 0 8

0 . 0 1

0 . 9 8

0 . 0 6

0 . 0 1

0 . 9

9

0 . 0 6

0 . 0 1

C 3 B

A R ( r a t i o )

1 . 8 5

0 . 2 4

0 . 0 4

1 . 7 7

0 . 2 3

0 . 0 4

1 . 6 1 *

0 . 1 5

0 . 0 3

1 . 3 9 *

0 . 1 4

0 . 0 2

1 . 2 0 *

0 . 1 5

0 . 0 3

1 . 0

3 *

0 . 1 3

0 . 0 2

C 4 P A R ( r a t i o )

1 . 3 4

0 . 1 3

0 . 0 2

1 . 2 5

0 . 1 4

0 . 0 3

1 . 1 5 *

0 . 1 7

0 . 0 3

1 . 0 1 *

0 . 0 6

0 . 0 1

1 . 0 0

0 . 0 7

0 . 0 1

0 . 9

7

0 . 0 5

0 . 0 1

C 4 B

A R ( r a t i o )

1 . 8 3

0 . 2 5

0 . 0 5

0 . 7 1

0 . 2 2

0 . 0 4

1 . 5 9

0 . 2 1

0 . 0 4

1 . 3 6 *

0 . 1 2

0 . 0 2

1 . 1 9 *

0 . 1 8

0 . 0 3

1 . 0

4

0 . 1 2

0 . 0 2

* I n d i c a t e s s t a t i s t i c a

l s i g n i c a n c e w i t h r e s p e c t t o t h e p r e c e d i n g o b s e r v a t i o n .



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stages in vertebral development consisted of a noncompara-

tive denition of morphological characteristics at each obser-vation.The ndings of both the visual (qualitative) and cephalo-

metric (quantitative) analyses revealed that a statistically sig-nicant discrimination can be made between the initial twostages in cervical vertebral maturation only according to thedifference in depth of the concavity at the lower border of thesecond cervical vertebra. A denite concavity at the lowerborder of C2 is present in 80% of the subjects at cervicalstage 2.

Theappearance of a visible concavityat the lower borderof the third cervical vertebra is the anatomic characteristic thatmostly accounts for the identication of the stage immedi-ately preceding the peak in mandibular growth (cervicalstage 3). The distinction among Cvs 4, Cvs 5, and Cvs 6 asdened in the former CVM method is possible only by usingthe shape of the bodies of C3 and/or C4 as a discriminantfactor.18

Stages of Cervical Vertebral MaturationThe stages of cervical vertebral maturation in the modiedversion of themethod presentedhere are illustrated diagram-matically in Fig 2. The six stages are dened as follows:

Cervical stage 1 (CS1, Fig 3 ). The lower borders of all the

three vertebrae (C2-C4) are at. The bodies of both C3 andC4 are trapezoid in shape (the superior border of the verte-bral body is tapered from posterior to anterior). The peak inmandibular growth will occur on average 2 years after thisstage.

Cervical stage 2 (CS2, Fig 4 ). A concavity is present at thelower border of C2 (in four of ve cases, with the remainingsubjects still showing a cervical stage 1). The bodies of bothC3 and C4 are still trapezoid in shape. The peak in mandib-ular growth will occur on average 1 year after this stage.

Cervical stage 3 (CS3, Fig 5 ). Concavities at the lower bor-

ders of both C2 and C3 are present. The bodies of C3 and C4may be either trapezoid or rectangular horizontal in shape.

The peak in mandibular growth will occur during the year

after this stage.Cervical stage 4 (CS4, Fig 6 ). Concavities at the lower bor-ders of C2, C3, and C4 now are present. The bodies of bothC3 and C4 are rectangular horizontal in shape. The peak inmandibular growth has occurred within 1 or 2 years beforethis stage.

Cervical stage 5 (CS5, Fig 7 ). The concavities at the lowerborders of C2, C3, and C4 still are present. At least one of thebodies of C3 and C4 is squared in shape. If not squared, thebody of the other cervical vertebra still is rectangular hori-zontal. The peak in mandibular growth has ended at least 1year before this stage.

Figure 2 Schematic representation of the stages of cervical vertebrae according to the newly modied method.

Figure 3 Cervical stage 1 (CS1): two clinical examples.



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Cervical stage 6 (CS6, Fig 8 ). The concavities at the lowerborders of C2, C3, and C4 still are evident. At least one of thebodies of C3 and C4 is rectangular vertical in shape. If notrectangular vertical, the body of the other cervical vertebra issquared. The peak in mandibular growth has ended at least 2years before this stage.

Application to Dentofacial OrthopedicsThe clinical application of the method to dentofacial ortho-pedics becomes relevant for those treatment protocols thatbenet from the inclusion of the period of accelerated man-dibular growth. CVMmethod can be useful as a maturationalindex to detect the optimal time to start treatment of man-dibular deciencies by means of functional jaw orthope-dics.25,26 It has been demonstrated that the effectiveness of functional treatment of Class II skeletal disharmony depends

strongly on thebiological responsiveness of the condylar car-tilage, which in turn is related to the growth rate of the man-dible.27







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When CS1 or CS2 are diagnosed in the individual patientwith mandibular deciency, thecliniciancanwait at least oneadditional year for a radiographic reevaluation aimed to starttreatment with a functional appliance. The appearance of adenite concavity at the lower border of C2 indicates that thegrowth spurt is approaching, that is, that the year of the peakwill start approximately 1 year after this stage.CS3representsthe ideal stage to begin functional jaw orthopedics, as the

peak in mandibular growth will occur within the year afterthis observation. In the sample examined here, total mandib-ular length exhibited an average increase of 5.4 mm in theyear following CS3, a signicantly greater increment whencompared with the growth interval from CS1 to CS2 (about2.5 mm), from CS2 to CS3 (again about 2.5 mm), and to thepostpeak between-stage intervals (1.6 mm and 2.1 mm forthe intervals from CS4 to CS5 and from CS5 to CS6, respec-tively).

Treatment Timing for Class II Malocclusion An emerging fundamental concept underlying Class II cor-rection is that this type of intervention should be undertakenwhen the likelihood for a maximum growth response is high,that is, during the circumpubertal growth period. A series of short-term studies has demonstrated statistically and clini-cally signicant correction of the Class II dentoskeletal rela-tionships when either functional appliances or xed appli-ances in combination with Class II elastics are used duringthe circumpubertal period ( Table 3 ). When Class II maloc-clusion is treated too early (therapy starting at CS1 and com-pleted before the interval of peak velocity in mandibulargrowth, ie, before CS3), the net difference in supplementarygrowth of the mandible (expressed cephalometrically by themeasurement Co-Pg or Co-Gn) in the treated samples versus

untreated controls ranges between 0.4 mm and 1.8 mm ( Ta-ble 3). On the contrary, when intervention in a Class II pa-


T a

b l e

3

A n a

l y s i s o f t h e

L i t e r a t u r e

R e g a r

d i n g

T r e a t m e n t T i m i n g

f o r

C l a s s

I I M a l o c c

l u s i o n

*

T h e E f f e c t o f T r e a t m e n t T i m i n g o n S u p p l e m e n t a r y E l o n g a t i o n o f t h e M a n d i b l e i n C l a s s I I T r e a t m e n t

P r e - P u b e r t a l C l a s s I I T r e a t m e n t ( t r e a t m e n t e n d s b e f o r e t h e p u b e r t a l

p e a k i n m a n d i b u l a r g r o w t h )

P u b e r t a l C l a s s I I T r e a t m e n t ( t r e a t m e n t i n c l u d e s t h e p u b e r t a l p e a k i n

m a n d i b u l a r g r o w t h )

S t u d y

A p

p l i a n c e

N e t i n c r e a s e i n

m a n d i b u l a r l e n g t h

o v e r u n t r e a t e d

c o n t r o l s

S t u d y

A p p l i a n c e

N e t i n c r e a s e i n

m a n d i b u l a r l e n g t h

o v e r u n t r e a t e d

c o n t r o l s

M c N a m a r a e t a l . ,

1 9 8 5 2 8

F R - 2

1 . 2 m m

M c N a m a r a e t a l . ,

1 9 8 5 2 8

F R - 2

3 . 6 m m

P e t r o v i c e t a l . ,

1 9 9 4 2 9

C l a s s

I I e l a s t i c s

1 . 0 m m

P e t r o v i c e t a l . ,

1 9 9 4 2 9

C l a s s

I I e l a s t i c s

3 . 0 m m

T u l l o c

h e t a l . ,

1 9 9 7 3 0

B i o n a t o r

1 . 4 m m

L u n d a n

d S a n

d l e r ,

1 9 9 8 3 6

T w i n - b

l o c k

2 . 4 m m

K e e l i n g e t a l . ,

1 9 9 8 3 1

B i o n a t o r

0 . 4 m m

F r a n c h i e t a l . ,

1 9 9 9 3 7

A c r y l i c H e r

b s t

2 . 7 m m

B a c c e t t i e t a l . ,

2 0 0 0 2 5

T w i n - b

l o c k

1 . 8 m m

B a c c e t t i e t a l . ,

2 0 0 0 2 5

T w i n - b

l o c k

4 . 7 m m

B a c c e t t i a n

d F r a n c h i , 2 0 0 1 2 6

F R - 2

1 . 0 m m

B a c c e t t i a n

d F r a n c h i , 2 0 0 1 2 6

F R - 2

3 . 9 m m

D e A l m e i

d a e t a l . ,

2 0 0 2 3 2

F R - 2

0 . 9 m m

F a l t i n e t a l . ,

2 0 0 3 3 5

B i o n a t o r

4 . 3 m m

J a n s o n e t a l . ,

2 0 0 3 3 3

F R - 2

0 . 5 m m

O B r i e n e t a l . ,

2 0 0 3 3 4

T w i n - b

l o c k

1 . 6 m m

F a l t i n e t a l . ,

2 0 0 3 3 5

B i o n a t o r

0 . 8 m m

* T h e

a p p r a i s a

l o f t r e a t m e n t t i m i n g i n i n d i v i

d u a l s t u d i e s w a s

b a s e

d u p o n c h r o n o

l o g i c a g e ,

h a n d a n

d w r i s t ,

o r C V M m e t

h o d . A l l d a t a a r e s h o r t - t e r m a n

d r e

f e r t o c o n t r o

l l e d s t u d i e s .



9/11

tient includes the CS3-CS4 interval (growth spurt), the netsupplementary growth of the mandible in treated samplesversus untreated controls ranges from 2.4 mm to 4.7 mm(Table 3 ). The data reported in Table 3 suggest also that inClass II patients, the timing of therapeutic intervention has agreater impact on supplementary elongation of the mandiblethan does the type of appliance used.

The only long-term study that deals with the evaluation of the role of treatment timing in Class II correction 35 revealedthat the use of a Bionator followed by xed appliances incontrast with untreated Class II controls is able to induce asupplementary elongation of the mandible of less than 2 mmwhen the functional appliance is used before the peak inmandibular growth, and of about 5 mm when the growthspurt is included in the treatment interval. These results pos-sess signicance not only at the statistical level, but also at theclinical level, as the correction of a full cusp Class II molarrelationship to Class I represents a 5 to 6 mm sagittal correc-tion at the level of the occlusal plane.

Treatment Timing for Class III MalocclusionsEarly treatment of Class III disharmony has been advocatedfor a long time. 38 The clinical understanding that Class IIImalocclusion is established early in life and that it is not aself-correcting disharmony has led to the recommendation of intervention as early as in the deciduous dentition. Cephalo-metric and morphometric investigations using Class III un-treated controls have demonstratedthat treatment of Class IIImalocclusion by means of efcient protocols (eg, maxillaryexpansion and protraction) is more effective in the early thanin the late mixed dentition. 39-41

Until recently, however, information about the possiblerole of treatment timing on long-term changes after activetherapy for Class III malocclusion was not available in theliterature.42 At a postpubertal observation (CS5 or CS6),when active growth of the craniofacial skeleton is completedfor the most part, Class III subjects treated with a rapid max-illaryexpander anda facialmask well before thegrowthspurt(CS1) present with different long-term changes with respectto Class III subjects treated at a later stage, that is, at the peakin mandibular growth (CS3). Prepubertal orthopedic treat-ment of Class III malocclusion is effective both in the maxilla(which shows a supplementary growth of about 2 mm over

Class III untreated controls) and in the mandible (restrictionin growth of about 3.5mm over controls), whereas treatmentof Class III malocclusion at puberty is effective at the man-dibular level only (restriction in growthof about 4.5mm overcontrols). 42

Thendings in themaxilla have a biological explanation inthe physiology of the circummaxillary sutures, which aremore amenable to orthopedic intervention during the earlystages, whereas they become more heavily interdigitatedaround puberty. 43 On the other hand, the possibility of re-stricting mandibular growth both before and during pubertygives the clinician the chance of resuming facemask therapy

at a later time when correction of Class III relationships isonly partial after the prepubertal intervention.

Treatment Timing for Transverse Maxillary DeciencyThe issue of treatment timing for maxillary expansion aimedto correct transverse maxillary deciency has been addressedin the past by Melsen 44 and by Wertz and Dreskin. 45 Melsenused autopsy material to examine histologically the matura-tion of the midpalatal suture at different developmentalstages.44 In the infantile stage (up to 10 years of age), thesuture was broad and smooth, whereas in the juvenile stage(from 10 to 13 years) it had developed in a more typicalsquamous suture with overlapping sections. Finally, duringthe adolescent stage (13 and 14 years of age) the suture waswavier with increased interdigitation. From thesehistologicaldata, the inference is that patients who show an advancedstage of skeletal maturation at themidpalatal suturemay havedifculty in undergoing orthopedic maxillary expansion.Clinical support for the histologic ndings by Melsen 44 isderived from the results of a study by Wertz and Dreskin 45who noted greater and more stable orthopedic changes inyoung patients (under the age of 12 years). Either group of researchers, however, did not use any biological indicator of skeletal maturity to dene early versus late treatment.

The use of the CVM method has been applied recently totheestimate of the effects of different treatment timing on thecorrection of transverse maxillary deciency. 46 A sample of 42 patients was compared with a control sample of 20 sub-

jects. Posteroanterior cephalogramswere analyzed for each of the treated subjects at T 1 (pretreatment), T 2 (immediate pos-texpansion), and T 3 (long-term observation); lms wereavailable at T1 and at T 3 for the controls. The mean age at T 1was 11 years and 10 months for both the treated and thecontrol groups. The mean ages at T 3 also were comparable(20 years 6 months for the treated group, and 17 years 8months for the control group). Following rapid maxillaryexpansion and retention (2 months on average), xed stan-dard edgewise appliances were placed. The study includedtransverse measurements on dentoalveolar structures, max-illary and mandibular bases, and other craniofacial regions(nasal, zygomatic, orbital, and cranial).

Treated and control samples were divided into two groupsaccording to individual skeletal maturation as evaluated bythe CVM method. The early treated and early control groupsconsisted of subjects who had not reached the pubertal peakin skeletal growth velocity at T 1 (CS1 through CS3), whereas

the late-treated and late control groups were comprised of subjects during or slightly after the peak at T 1 (CS4 throughCS6). The group treated before the pubertal peak showedsignicantly greater short-term increases in the width of thenasal cavities. In the long-term, increments in maxillary skel-etal width, maxillary intermolar width, lateronasal width,and latero-orbitale width were signicantly greater in theearly-treated group when compared with the correspondingcontrol group. The late-treated group exhibited signicantincreases in lateronasal width and in maxillary and mandib-ular intermolar widths. The use of the CVM method demon-strated that rapid maxillary expansion before the peak in

skeletal growth velocity is able to induce more pronouncedtransverse craniofacial changes at the skeletal level. Treat-



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ment changes are more dentoalveolar in nature when expan-sion is performed during or after the peak.

Treatment Timing for Increased Vertical DimensionThe CVM method also has been applied to the appraisal of ideal treatment timing for a specic therapeutic protocol forthe correction of vertical excess of the face by means of a

bonded rapid maxillary expander in association with a verti-cal-pull chincup. One of the goals of orthopedic treatment insubjects with increased vertical dimension is the control of the vertical growth of the mandibular ramus (expressedcephalometrically by the measure Co-Go). Available short-term data from our research group show that a signicantlymore favorable effect can be obtained when treatment is per-formed at CS3, that is, at the peak in mandibular growth,when compared with treatment performed at an earlier mat-urational stage (CS1). No signicant increase in ramal heightis observed in hyperdivergent subjects treated at CS1,whereas a signicant increase of about 2 mm more than inuntreated controls is recorded in hyperdivergent subjectswho receive orthopedic treatment at CS3.

Final RemarksThe CVM method is comprised of six maturational stages(cervical stage 1 through cervical stage 6, CS1-CS6), with thepeak in mandibular growthoccurring between CS3and CS4.The pubertal peak has not been reached without the attain-ment of bothCS1 and CS2. In particular, the detection of CS2indicates that the growth spurt is approaching, and it willstart at CS3, which is approximately 1 year after CS2. Activegrowth is virtually completed when the CS6 is attained.

The method is particularly useful when skeletal maturityhas to be appraised on a single cephalogram and only thecervical vertebrae from the second one through the fourthone are visible. The CVM method has the further advantageto be assessed on the lateral cephalogram, which is the radio-graphic record used routinely for orthodontic diagnosis andtreatment planning.

The use of a reliable biological indicator of skeletal matu-rity such as the CVM method is highly recommended for awide variety of research and clinical applications. In bothprospectiveand retrospective controlled studies, CVM stagesenable the researcher to categorize treated/untreated subjects

for a biologically appropriate matching between experimen-tal and control samples. Further, the appraisal of the CVMstage in the individual subject allows for a more precise def-inition of early and late samples in studies aimed to deter-mine the role of treatment timing in the effectiveness of dif-ferent treatment protocols for the correction of malocclusions. To date, the application of the method ininvestigations on treatment timing in orthodontics anddentofacial orthopedics has revealed that:

1. Class II treatment is most effective when it includes thepeak in mandibular growth;

2. Class III treatment with maxillary expansion and pro-

traction is effective in the maxilla only when it is per-formed before the peak (CS1 or CS2), whereas it is

effective in the mandible during both prepubertal andpubertal stages;

3. skeletal effects of rapid maxillary expansion for thecor-rection of transverse maxillary deciency are greater atprepubertal stages, while pubertal or postpubertal useof the rapid maxillary expander entails more dentoal-veolar effects; and

4. deciency of mandibular ramus height can be en-hanced signicantly in subjects with increased verticalfacial dimension when orthopedic treatment is per-formed at the peak in mandibular growth (CS3).

To summarize, effects of therapies aimed to enhance/re-strictmandibular growthappearto be of greater magnitudeatthe circumpubertal period during which the growth spurtoccurs in comparison to earlier intervention, while effects of therapies aimed to alter themaxilla orthopedically (maxillaryprotraction/maxillary expansion) are greater at prepubertalstages.

The CVM method can be helpful for the assessment of completion of active growth in studies dealing with the long-term effects of orthodontic/orthopedic treatment strategies.Similarly, the method can be used to identify clinically theadequate time for intervention in subjects who need surgeryfor the late correction of facial disharmonies.

Due to its practical applications, the CVM method appearsto be a powerful diagnostic tool. The implementation of themethod in orthodontic decision making allows for an im-provement of treatment outcomes by combining effectiveand efcient protocols with optimal treatment timing.

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