GROWTH PREDICTIONS
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Holdaway’s soft-tissue VTO • Purpose is to establish a balanced profile and pleasing facial esthetics and to evaluate the orthodontic correction necessary to achieve this goal • Holdaway VTO emphasizes soft tissue profile balance
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• Growth of the cranio-facial skeleton is predicted for the estimated treatment time, and the soft tissue profile between the nose and the chin arranged to create an “ideal” facial profile for the individual patient • Maxillary and mandibular incisors are repositioned to eliminate lip strain • Allowance is made for probable post treatment “incisor rebound” • Maxillary teeth are positioned first, and then lower incisors are repositioned to be in harmony with the upper incisors www.indiandentalacademy.com
• Following the repositioning of the mandibular incisors, the resultant arch length discrepancy may be calculated to determine whether or not teeth should be extracted
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• The VTO is thus a dynamic cephalometric analysis which takes into account both growth and biomechanics, thus achieving its aim of being a Visualized Treatment Objective • It outlines a goal from the inception of treatment and may be usefully employed in monitoring growth and treatment progress
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• In sum, therefore the VTO accomplishes : Predicts growth over an estimated treatment time, based on the individual morphogenetic pattern Analyzes the soft tissue facial profile Graphically plans the best soft tissue facial profile for the particular patient Determines favorable incisor repositioning, based on an “ideal” projected soft tissue facial profile
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Assists in determining total arch length discrepancy when taking into account “cephalometric correction� Aids in determining between extraction and nonextraction treatment Aids in deciding which teeth to extract Assists in planning treatment mechanics Surgery vs. non-surgery It provides a visual goal or objective for which to strive during treatment www.indiandentalacademy.com
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OJECTIVE : To draw frontonasal area, line BaN and line NA
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OBJECTIVE : To express growth in the frontonasal area over a two-year period Super impose on line BaN and move the VTO until there is 1.5 mm growth in the fronto nasal area Holding the VTO tracing in the position copy the www.indiandentalacademy.com Ricketts facial axis
OBJECTIVE : To express growth in a vertical direction in the mandible, and to draw the anterior portion of the mandible, soft tissue chin and the mandibular plane of Downs Superimpose the VTO facial axis along the original facial axis. Move the VTO tracing upwards so that the VTO BaN line is above the original BaN line, the distance between these lines should be three times the amount of growth expressed in the www.indiandentalacademy.com frontonasal area
OBJECTIVE : To express growth in a horizontal direction in the mandible and draw the posterior border of the mandible Move the VTO forward until the original and VTO foramen rotundae are vertically aligned
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OBJECTIVE : To locate and draw the maxilla, and lower half of the nose Super impose the VTO NA line on the original NA line and move the VTO up until the vertical growth is expressed above the BaN line and below the mandibular plane is in the ratio of 40:60 www.indiandentalacademy.com
OBJECTIVE : To locate and draw the occlusal plane With the VTO superimposed on line NA, move the VTO tracing so that the vertical growth between the maxilla and the mandible is expressed as being 50% above the maxilla and 50% below the mandible www.indiandentalacademy.com
OBJECTIVE : TO determine the soft tissue lip contour using the Holdaway line
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OBJECTIVE : to reposition lower incisor and calculate resultant arch length change judge the position of the lower incisor To calculate lower arch length change, superimpose tracing on mandibular plane and register on symphysis. Measure the distance between old and new incisor position and double this measurement to determine total arch length discrepancy www.indiandentalacademy.com
OBJECTIVE : To reposition lower first molar, use the plaster casts to determine arch length discrepancy due to crowding and/or rotation.
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OBJECTIVE : To reposition maxillary first molar Using the occlusal plane and lower first molar as a guide draw the maxillary first molar in good Class I occlusion with the lower first molar
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OBJECTIVE : To complete art work ANS to upper incisor Anterior portion of hard palate Lower alveolus lingually and labially
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A statistical evaluation of the Ricketts and Johnston growthforecasting methods
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• Four methods of growth forecasting were compared – Johnston forecast grid – Ave. increments from sella-nasion – Ricketts short-range prediction – Computer forecast • Objective was to predict the final position of the points A, Pogonion, end of the nose, lower molar and point Xi with respect to cranial reference lines
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• The Johnston forecast grid
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• Errors were squared, summed, and divided by the number in the sample to get the meansquare error. Square root was taken for the rotmean-squared error • 70% of the predictions will be within ±1 rms error • 95 % will be within ±2 rms error
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• Ave. increments from sella-nasion To study points not included in Johnston forecast grid, as well as grid’s applicability to a 10year growth period Average increments for each of the points under consideration were calculated from SN with S as the origin, and these increments were then used in a prediction as follows: Using sella-nasion as a horizontal axis with sella as its center, ave. increments per year were added
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• Girls - 15 years • Boys - 19 years
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• The Ricketts shortrange prediction
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• Computer forecast Individual growth curves are used for the mandible, maxilla, and cranial base rather than using the same increments for every age group Abnormal growth with RMDS data bank
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Patients who grow abnormally large mandibles with less growth in the cranial base – abnormal Class III patterns
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Unusually strong patterns which rotate forward
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Abnormally weak facial patterns – they rotate distally
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Results Johnston grid Least accurate It was accurate as any for predicting the nose 64 percent accurate for Point A 70 percent accurate on Pogonion
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S-N average increments Improvement over the Johnston grid at both Pogonion and point A
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Ricketts short-range prediction method Less rms error than Johnston grid or SN average increments Some of the smaller over-all error was due to the fact that point CC, the origin of this growth prediction, is closer to Pogonion than to Sella 10 to 20 percent improvement of this method over average increments
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RMDS computer program Based on theories of Ricketts Individualized further by using growth rates variable for the patient’s age and by recognising unusual facial patterns Most accurate of the four methods
21% more accurate than Ricketts 56% more accurate than Johnston grid
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Prediction of abnormal growth in Class III malocclusions If the actual growth was far different from the predicted growth, the records were often returned to the laboratory so that a file of “abnormal growth “ could be compiled A consistent type emerged – one which grew more in the mandible and less in the cranial base than predicted
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• The three most consistent measurements which deviated from the normal in these patients were ramus position, porion location and cranial deflection • Predictor measurements • Hokkaido University Orthodontic Department
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• For cranial deflection, porion location and ramus position the greater the value, the more likely the patient is hypothesized to have a Class III growth pattern • With molar relation, the lesser the value, the more likely the patient is to have a Class III malocclusion
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Clinical norm (CN) Cranial deflection 28 Ramus position 75.5 Porion location 37 Molar relation -3.0
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Standard Deviation 3.0 2.8 2.5 2.6
Amount of abnormality, or deviation is calculated by : V-CN SD
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Evaluation of Ricketts’ long-range growth prediction in Turkish children • Cephalometric analysis was conducted at baseline and 7 years for 40 children (20 girls, 20 boys) who received no orthodontic treatment. Ricketts’ long-range prediction was performed from baseline cephalograms and compared with actual growth 7 years later. Twenty-one cephalometric (12 angular and 9 linear) parameters were measured on actual and predicted tracings. The Pearson correlation coefficient was used to evaluate relationships between the “predicted” and “actual” measurements. • There was a higher level of correlation for growth prediction in girls www.indiandentalacademy.com
• The baseline average age was 9.2 ± 0.82 years for girls and 9.3 ± 0.92 years for boys • Linear measurements: 1, Convexity; 2, Condylion-Point A; 3, Condylion-Gnathion; 4, Lower lip to E plane; 5, Upper lip length; 6, Cranial length (anterior) (CC-Na); 7, Ramus height (CF-Go); 8, Porion to PTV; 9, Corpus length (Xi-Pm). • Angular measurements: 1, Lower face height; 2, Nasolabial angle; 3, Facial depth; 4, Facial axis; 5, Maxillary depth; 6, Maxillary height; 7, Palatal plane-FH plane; 8, Mandibular plane-FH plane; 9, BNA angle; 10, Cranial deflection; 11, Ramus-Xi position; 12, Mandibular arc angle. www.indiandentalacademy.com
Ricketts’ long-range growth prediction applied to Turkish children showed statistically significantly higher correlations between predicted and actual measurements in: • Convexity, lower face height, condylion, point A, upper lip length, facial depth, facial axis, palatal plane-FH plane angle, mandibular plane-FH plane angle, ramus height, and mandibular arc angle in girls • Lower face height, nasolabial angle, porion to PTV, ramus-Xi position, cranial deflection, condylion-point A, lower lip-E plane, facial axis, BNA angle, and mandibular arc angle in boys. www.indiandentalacademy.com
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