Dental Vto Mbt

394 JCO/JULY 1999

Most cephalometric analyses measure maxil-lary and mandibular skeletal relationships

in the vertical and horizontal planes, along withthe position and angulation of the incisors. Feworthodontic analyses, however, provide informa-tion about the direction and amount of dentalmovements required during treatment within themaxillary and mandibular arches.

The Steiner analysis, for example, includesthe initial positions and desired movements ofthe first molars, canines, and dental midlines, butis ambiguous about Class II correction and toothmovements after extractions. Without this infor-mation, the orthodontist can lose sight of theanchorage requirements of a case and thus under-estimate the amount of patient cooperation andanchorage needed to reach treatment objectives.

The dental analysis presented in this arti-cle—in effect, a dental Visualized TreatmentObjective—was designed to provide organizedand simplified information to help in diagnosis,treatment planning, and the extraction/nonex-traction decision. It should be used as an adjunctto, but not a substitute for, conventional cephalo-metric analyses. It takes little time to completeand occupies only a small part of the treatmentcard. Progress can be checked by referring to thedental VTO at the patient’s regular adjustmentappointments.

Method

The dental VTO consists of three charts:Chart 1 records the initial midline and first

molar positions with the mandible in centric rela-tion.

Chart 2 measures the lower arch discrepan-cy, similarly to the Steiner analysis.1 The fourprimary factors in each case are:1. Space required for relief of crowding, mea-sured from canine to midline and from firstmolar to midline on each side.

2. Space required for the desired correction ofprotrusion or retrusion of the mandibularincisors.3. Space required for leveling the curve of Spee,measured as the deepest point on a line extend-ing from the distal cusps of the second molars tothe incisal edges of the central incisors on eachside; this point is normally found in the premolarregion (Fig. 1).4. Space required for midline correction.

Four secondary factors that can sometimesprovide additional space are listed, if applicable,below the primary chart:1. Additional space from interproximal enamelreduction.2. Additional space from uprighting or distalmovement of mandibular first molars.3. Additional space from buccal uprighting ofmandibular canines and posterior teeth.4. Additional leeway or “E” space.

According to Moorrees, the leeway space,or the difference in size between the deciduouscanines, first molars, and second molars and thepermanent canines, first premolars, and secondpremolars, is an average of 1.5mm per side in themandibular arch and .9mm per side in the maxil-lary arch.2 “E” space, or the difference in sizebetween the primary second molar and the per-manent second premolar, is an average of 2.5mm

© 1999 JCO, Inc.

The Dental VTO: An Analysis ofOrthodontic Tooth MovementRICHARD P. McLAUGHLIN, DDSJOHN C. BENNETT, LDS, DOrth

Fig. 1 Curve of Spee measured as deepest pointalong line extending from distal cusps of secondmolars to incisal edges of central incisors on eachside.

VOLUME XXXIII NUMBER 7 395

Dr. McLaughlin is a Contributing Editor of the Journal of ClinicalOrthodontics and in the private practice of orthodontics at 1831Sunset Cliffs Blvd., San Diego, CA 92107. Dr. Bennett is in the privatepractice of orthodontics at 53 Portland Place, London W1N 3AH,England.

Dr. McLaughlin Dr. Bennett

Right

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Chart 1 with explanatory text Chart 1 as it is used

MIDLINE-MOLAR POSITION

LOWER ARCH DISCREPANCY


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Anticipated Treatment Change 1 1 .52.5

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ANTICIPATED TREATMENT CHANGE

per side in the mandibular arch and 2.3mm perside in the maxillary arch (Fig. 2).

The primary and secondary factors areadded together at the bottom of the chart to deter-mine the total lower arch discrepancy fromcanine to midline and from first molar to midlineon each side.

Chart 3 records the anticipated treatmentchange in terms of dental movements of the firstmolars, canines, and midline.

Two cases are presented to show how thedental VTO can be applied.

Case 1

A 12-year-old male presented with a ClassII skeletal pattern (Fig. 3). Vertically, he had aslightly high angle and a slightly long lowerfacial height. There were no crossbites, and thedentition was symmetrical in the transversedimension.

The patient’s dental relationships wererecorded in centric relation (Chart 1). His molar

relationships were 4mm Class II on the right sideand 3.5mm Class II on the left. The lower dentalmidline was deviated 1mm to the right.

The mandibular arch showed 3mm ofcrowding on the right side, all mesial to the rightcanine. Therefore, the amount of crowding fromfirst molar to midline was the same as theamount from canine to midline (Chart 2). On the

left side, there was only 1mm of crowding, alsobetween the canine and the midline.

The curve of Spee was about 2mm at itsdeepest point. Steiner suggested that leveling a2mm curve of Spee would advance the incisors1mm, thus requiring 1mm of space per side forthe leveling process. We have found this rule ofthumb to be clinically accurate.

The Dental VTO: An Analysis of Orthodontic Tooth Movement

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Fig. 2 Average “E” space: 2.5mm per side in man-dibular arch and 2.3mm per side in maxillary arch.

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Chart 1


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McLaughlin and Bennett

Fig. 3 Case 1. 12-year-old male with Class II skeletal pattern before treatment.

Because the lower midline was deviated1mm to the right, the midline correction wouldrequire 1mm of space on the left side and provide1mm of space on the right.

The mandibular incisors were inclined for-ward (97° to the mandibular plane) and were6mm in front of the APo line. Without extrac-tions, the incisors would either remain in thisposition or, more likely, be advanced farther.With extractions, the incisors could be retracted.Therefore, the decision was made to extract thefour first premolars and retract the mandibularincisors 2mm.

The space-gaining procedures of interprox-imal reduction, molar uprighting, and buccaluprighting of posterior teeth were not needed inthis case and were therefore not recorded inChart 2. There was no leeway or “E” space avail-able, since no primary teeth were present.

Anticipated treatment changes were record-ed in Chart 3 using the following process:

1. Extraction of the four first premolars pro-duced 7mm of space in each quadrant, sincethere was no crowding between the canines andfirst molars in either arch. This was indicated bywriting “(7)” in each quadrant.2. Because the total lower arch discrepancyfrom canine to midline was 5mm per side, themandibular canines needed to be retracted 5mminto the extraction sites. This was recorded on thebottom of the chart, with arrows showing thedirection of movement.3. The mandibular molars could therefore only

be moved 2mm to close the remainder of the7mm extraction spaces—also indicated witharrows on the bottom of the chart. This demon-strated a need for moderate anchorage control inthe mandibular arch. A mandibular lingual arch,for example, could be considered during the first3mm of canine retraction.4. The mandibular midline needed to be moved1mm to the right, as shown by the arrow on thebottom of the chart.5. There are four possible methods of Class IImolar correction in the growing patient:

a. Mesial movement of the mandibular firstmolars (in this case, 2mm per side).

b. Distal movement of the maxillary firstmolars. This is difficult in the presence of devel-oping maxillary second and third molars, but itcan be achieved. Superimposition of beginningheadfilms with progress or final headfilms willinevitably show downward and forward move-ment of the maxillary first molars, due to thegrowth of the entire facial complex. Althoughthis rotation may lead some clinicians to contendthat no distalization has occurred, it does notmean there has been no dentoalveolar or skeletalchange in the maxillary molar positions.

c. Limiting forward maxillary skeletal devel-opment, or retracting the maxilla. Because suchchanges are difficult to isolate, it is debatablehow much is skeletal (above the palatal plane)and how much is dentoalveolar (below thepalatal plane). Nasion normally grows forwardabout 1mm a year relative to sella, while A pointmay be maintained or retracted relative to itsoriginal position.

d. Forward mandibular rotation. This canoccur in two ways:

1) Mandibular growth. The direction ofoverall facial growth is critical to the “expres-sion” of mandibular growth. With more verticalpatterns, there is less forward expression ofmandibular growth and hence less interarch den-tal change. With less vertical facial growth,mandibular growth is expressed in a more for-ward direction, resulting in greater interarch den-tal change.

2) Limiting vertical maxillary develop-

The Dental VTO: An Analysis of Orthodontic Tooth Movement

JCO/JULY 1999398

1 5 252

1.58.59 0(7) (7)

(7) (7)

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Chart 3


ment. Although sizable claims have been madefor this method, it is difficult to significantlyinfluence the normal vertical development of thefacial complex. As with forward maxillary devel-opment, vertical development is hard to measurein isolation and therefore hard to categorize asskeletal or dentoalveolar. Nevertheless, even asmall limitation can greatly enhance a Class IIcorrection.6. In the present case, the molar relationship onthe right side was 4mm Class II, and since 2mmcould be corrected by mesial movement of themandibular molar, an additional 2mm of correc-tion was required. On the left side, an additional1.5mm of correction was needed. These amountswere recorded on the top of Chart 3 with distalarrows.

A palatal bar and a combination high-pulland cervical-pull headgear were used to preservemaxillary anchorage in this case. If favorablemandibular growth occurred in any of the wayslisted above, maxillary anchorage control couldbe reduced or eliminated, allowing the maxillarymolars to move more mesially. This could notbe predicted before treatment, however, and sothe numbers in Chart 3 represent the worst-casescenario.

A functional appliance could also havebeen considered before fixed appliance therapy.A good response to the functional appliancemight have reduced the amount of maxillaryanchorage support needed later. Extractionswould still have been required after the function-al phase, assuming incisor retraction was still atreatment objective.7. Taking into account the 2mm distal move-ment of the maxillary right molar and the 1.5mmdistal movement of the maxillary left molar, thecanines would have to be moved 9mm on theright and 8.5mm on the left to close the 7mmextraction spaces. This emphasizes the potentialbenefits of favorable growth and a favorablefunctional appliance response.

Leveling and alignment were carried outwith an .022" edgewise appliance, beginningwith light twisted wires, and proceeding to roundwires and finally to .019" × .025" rectangular

wires. Extraction sites were then closed with therectangular archwires, using pull-coil springsfrom the first molars to archwire hooks betweenthe lateral incisors and cuspids. Class II elasticswere used as little as possible, in conjunctionwith the headgear, to correct the anteroposteriorrelationship. Detailing and finishing were carriedout with .019" × .025" rectangular archwires.

With only average cooperation, total treat-ment time was 35 months (Fig. 4). The patientwore a tooth positioner full-time for six weeks; amaxillary Hawley retainer was then worn full-time for six months and at night only thereafter,while a fixed mandibular retainer was bonded.

Despite greater-than-average verticaldevelopment during treatment, the results werewithin normal limits. The occlusion was correct-ed from a Class II, division 1 to a Class I. Themaxillary incisors were retracted from 13mm infront of NA to 4mm in front of NA, and theirangulation to NA was reduced from 38° to 22°.

Case 2

A female patient age 8 years and 4 monthspresented with a Class II skeletal pattern (Fig. 5).Vertically, she was a low-angle patient with anormal lower facial height. There were no cross-bites, and the transverse dimension was symmet-rical.

The patient’s molar relationship was4.5mm Class II on the right side and 2.5mmClass II on the left (Chart 1). The dental midlines

were properly aligned.The mandibular arch showed 2.5mm of


4.5 2.5LR

Chart 1



JCO/JULY 1999400

Fig. 4 Case 1. A. After four bicuspid extractions and 35 months of treatment. B. Superimposition on SN at S.C. Superimposition on palatal plane and palatal curvature. D. Superimposition on mandibular symphysis andmandibular plane.

A

B C D

Fig. 5 Case 2. 8-year-old female with Class II skeletal pattern before treatment.



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Fig. 6 Case 2. A. After two phases of nonextraction treatment. B. Superimposition on SN at S.C. Superimposition on palatal plane and palatal curvature. D. Superimposition on mandibular symphysis andmandibular plane.

A

B C D

crowding from the canines to the midline on eachside (Chart 2). The leeway space in the mandibu-

lar arch, due to the presence of the primarycanines and the first and second molars, was1.5mm per side. The loss of these teeth wouldleave a total of only 1mm of crowding per side inthe mandibular arch.

Because the mandibular incisors were 4mmbehind the APo line and at 87° to the mandibularplane, the decision was made to advance them4mm, providing 4mm of space per side. Thecurve of Spee was about 1mm deep bilaterally,requiring .5mm of space per side for leveling. Nomidline correction was needed.

Adding all these factors together, there wasa total lower arch discrepancy of +1mm per sidefrom canine to midline and +2.5mm per sidefrom first molar to midline. With this spaceavailable, the mandibular canines could beadvanced 1mm per side, and the molars could beadvanced 2.5mm per side (Chart 3).

Thus, 2.5mm of the 4.5mm Class II correc-tion on the right side could be achieved by mesialmovement of the mandibular first molar. Theremaining 2mm would have to be produced bythe methods described under Case 1. On the left

side, the entire 2.5mm Class II correction couldby achieved by moving the mandibular firstmolar forward.

This patient underwent an eight-month firstphase of treatment with maxillary and mandibu-lar 2 × 4 appliances, nighttime headgear, anddaytime Class II elastics. The second phase,begun at age 12, involved mainly tooth align-ment for final correction, using full fixed appli-ances in conjunction with headgear and elastics.This phase was completed in 20 months (Fig. 6).

Retainers were a maxillary removablewraparound appliance and a mandibular fixed 4× 4 appliance.

Conclusion

We have used the dental VTO in clinicalpractice for several years, and we have found thissimple analysis to be most helpful as a diagnos-tic and treatment-planning aid and as a referencethroughout treatment. It is also useful in makingthe extraction/nonextraction decision.

There have been few cases in which theanalysis did not work. It has even been applied insome mutilated-dentition cases, and in patientswhere second molars were substituted for firstmolars, or premolars for canines.

REFERENCES

1. Steiner, C.C.: Cephalometrics for you and me, Am. J. Orthod.39:729-755, 1953.

2. Moorrees, C.F.A.: The Dentition of the Growing Child: ALongitudinal Study of Dental Development Between 3 and 18Years of Age, Harvard University Press, Boston, 1959.



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Chart 3


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Dental Vto Mbt