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- 1. 1 Dr. Mohammed Alruby Growth prediction Prepared by: Dr Mohammed Alruby
- 2. 2 Dr. Mohammed Alruby Definition: this is the forecasting of the final form and size of dento-facial structure. It is very important since most of pt. seeking to orthodontic treatment are still growing Types of growth prediction: 1- Magnitude of growth: annual increment of growth varies in each direction and between varies point and parts of the face. 2- Direction of growth: whether downward and forward or downward and backward (horizontal or vertical). 3- Timing of pubertal growth spurt: predicting the highest amount of growth per-unite time (pubertal growth spurt by: 1- hand- wrist radiograph. 2- Menarche. 3-hight spurt 4-Cervical vertebrae Source of error in growth prediction: 1- Variable growth rate in regional growth centers: the maxilla grows at a different rate than the mandible between 8—14 years of age : the mean annual rate of increase in maxillary base approximately 0.8mm compared to 1.9mm in mandible SN : M base 1 : 1.3—1.6mm S---Ar : Ar---Go 1 : 1.3 2- Growth pattern not fully taken into account: general speaking, horizontal growth changes are more easily predictable than the vertical changes. 3- Relationship between form and function: not take into account e.g in case of Class II division 2 the retroclined upper incisors will interfere with the mandibular growth, although remaining growth is present. 4- Age related factor. Significant of growth prediction: (A)- along the short range (2—3 years) 1- treatment planning: as in Class II division 1 we can determine the type of treatment: == maxillary retraction with headgear. == stopping of maxillary growth and slowing mandibular growth. == distalizing the maxillary teeth. == protraction of mandibular teeth. == combination. The line of treatment is dependent upon the amount of forward mandibular growth and direction of growth. 2- anchorage design: anchorage preparation in vertical type of growth or anchorage preservation in horizontal type of growth in the lower arch. (B)- along the long range: 1- future esthetics: if the pt has a class II malocclusion with horizontal growth pattern retraction of maxilla will not be needed or else flattering of the profile will occur. 2- stability: growth prediction will give an idea about the effect of growth on the abnormality whether to improve, maintain, or aggravate as: in Class III pt will horizontal growth pattern, retention should continue until growth ceases 3-space available for third molars: prediction of the space available for wisdom is calculate as distance between XI point and distal surface of the lower 2nd molar------- Ricketts.
- 3. 3 Dr. Mohammed Alruby *** prediction of growth direction: 1- Sum of posterior angles: Bjork Saddle angle + articular angle + gonial angle N S Ar S Ar Go Ar Go Me 123+_5 143_+6 130_+7 = 396_+6 If sum is less than 390: counter clock wise rotation of the jaws or horizontal type of growth with deep-bite. If sum is more than 402: clock wise rotation or vertical type of growth with open bite and short ramus. 2- Ratio of posterior facial height to anterior facial height: Jarabak. Posterior facial height SGn / anterior facial height N Me: = 62% - 65%. = if the ratio is more than 65% : counter clock wise rotation = if the ratio is less than 62% : clock wise rotation 3- Mandibular plane angle: Downs MP/FH is normally decreased by age from 28 degree to 23 degree. = if increased above the average ----- vertical growth pattern. = if increased below the average ----- horizontal growth pattern. 4- Y axis angle: Downs FH / SGn is normally 59.4_+6.5 = if the angle becomes less than 53 degrees; ---- horizontal growth pattern. = if the angle more than 66 degrees: ---- vertical growth pattern. 5- Facial axis angle: Ricketts. FH / NGn: 90_+3 = if angle decreased ---- horizontal growth pattern. = if angle increased ----- vertical growth pattern. 6- Gonial angle: Ar Go Mn : 128_+7 =If angle decreased -----horizontal growth pattern =if angle increased ----- vertical growth pattern. 7- Upper and lower gonial angle: Jarabak. Upper gonial angle: N Go Ar Lower gonila angle: N Go Me Decreased lower gonial angle: --- horizontal growth pattern. Increased lower gonial angle: -----vertical growth pattern. 8- Bjork method: Bjork stated that prediction of growth individual patient is very important consideration in orthodontic to decide when extrusive or intrusive mechanics should be used.
- 4. 4 Dr. Mohammed Alruby Bjork introduced a simple method for growth prediction from single cephalogram and he determined some criteria developed as a result of bone remolding in particular type as: Criteria forward backward 1-inclinatio of condylar head slop forward straight or slop backward 2-curvature of mandibular canal curved straight 3-shape of lower border curved downward notched at gonion 4-inclination of symphysis slop forward=strong chin slop backward weak chin 5-inter incisal angle obtuse acute 6-inter molar angle obtuse acute 7-interpremolar angle obtuse acute 8-lower anterior facial height decreased increased *** Prediction of growth amount: 1- Tweed method: = is a part of treatment planning, he used two lateral cephalogram taken between 12 to 18 months’ interval, superimposed on Sn and registered at S point, four angles are measured (FMA, FMIA, IMPA, ANB). = he stated that face grow in three ways: 1-25%: type A: both maxilla and mandible grow in downward and forward direction to the same extent, so no change in ANB. 2-15%: type B: although the entire face may be growing downward and forward, the maxilla grows faster than mandible there is an increase in ANB angle. 3-60%: type C: the mandible grows in downward and forward direction faster than the maxilla, there is decrease in ANB angle. 2- Jonston printed forecast grid method: 1968—1975 = he introduced a method for predicting growth changes using printed grids, he studied the growth changes of 42 variables longitudinally for 5 years (8 to 13), the serial grids were superimposed, oriented at SN line and use S point as a reference point. = he found that the vertical height increase by 10mm for A point to pogonion and there was 10mm increase in horizontal position of pogonion but at B point only 7mm. = this method provides a general line forecasting but should be exercised when applying in individual pt. = Schaly and Bagha study the accuracy of this method and found that its accuracy was 64% for point A and 70% for pogonion. 3- Harvold method: = Harvold indicate that the growth of maxilla is poorly correlated with growth of the mandible. The length of maxilla and mandible varies at 6 years and this variation increase at 12 years of age. = separate scatter gram for ages 6—9 years and at 9 to 12 years old leads to these conclusion: a- A reliable to predict anything about what will be happening between 9 to 12 years of age on the basis of what has taken place between 6 to 9 years of age.
- 5. 5 Dr. Mohammed Alruby b- The size of the mandible at age 9 years gives no definite clue as to how much what mandible will grow in three years. c- The size of the mandible at 12 years of age is dependent largely on the growth between 6 to 12 years not on the size of the mandible at 6 years. = Harvold concluded: that the prediction based on single X-ray film is not workable. And prefer to use more than one x-ray image and superimposed on natural reference structure. 4- Walker method: =Walker used a mathematical model and computer to predict the growth standardized simulate treatment. = bones of skull are individually mapped and a series of 177 coordinate points are used to represent the profile, then the information is transferred to computer. = by using computer programs, the large files are assembled according to age, sex. Race that can be grouped to produce standard. = 70% accuracy in prediction with one film of patient, the probability increase above 90% when using another cephalometric film with six months a part. = Walker define normal and abnormal growth for a person but not his true growth pattern, he pointed that, we can recognize a change in individual from the usual pattern within few months. 5- Enlow and Moyers method: They developed their method of equivalent for counterpart analysis which is helpful in form analysis and growth analysis. They study the anatomic fit between horizontal and vertical lines to know the cause of dysplasia. Two films are traced and superimposed and compare between them to predict whether the growth: == maintain the case, == improve it, == aggravate it. 6- Holdway’s method: = this method is termed visualized treatment objective (V.T.O), because it serves as a guide and for treatment planning. = this method is based on accurate construction related to reference points and permits individual peculiarities to be taken into account: =rate of growth, ==direction of growth. == treatment principles Advantages: flexibility == 70% reliability == does not lay down treatment procedures thus leaving the orthodontist free to make his own decisions Phases of Holdaway analysis: 1- The fronto-nasal area, SN and NA lines are traced Growth prediction is based on changes in SN SNA probably changes 1degree in 5 years, so far short term prediction, it is considered to be constant. 2- Superimposing on SN line, the SN – Gn is opened by 1 -2 degree so: - If there was distalization: ---- y axis was opened 1 –2 degree. - With activator therapy: ---- left in its original position - With extraction therapy: ---- slightly closed. 3- Superimposing the VTO y axis on the original y axis and using it as growth parameter, and the mandible is related downward and forward to SN, this determine: anterior facial height
- 6. 6 Dr. Mohammed Alruby Anterior position of the mandible. = the two Y axis are superimposed and the VTO is moved upward 3 times the amount of growth expressed in SN. The anterior portion of the mandible including, the symphysis and border: MP Go Gn. 4- Horizontal growth of the mandible is outlined by moving forward along the Go Gn-- MP line. The posterior position of the mandible and ascending ramus are drawn when the two Sella line in the same vertical plane. 5- Based on the assumption that: = facial growth may be divided into 3 section between nasion and menton. = the section between nasion and maxilla represent Y3 of the total facial height. To determine the vertical position of maxilla: the two NA line are superimposed, 40% of total growth will be above the SN line, 60% below Go- Gn. The maxilla is drawn in, then point A is estimated, depending on the treatment mechanics and the nose, taking into account 1mm of growth 6- Superimpose with the two NA lines superimposed and the growth increase distributed so that: 50% is above the maxilla. 50% is below the mandible. Then the occlusal plane is drawn 3mm below the lip base. 7- Determination of the extent of repositioning of the upper incisors, this serves as a guide to draw the soft tissue profile between nose and chin soft tissue thickness between point A and lip profile: remain unchanged, and its position is determined only by new position of A. The structure along the maxillary base are superimposed, - the soft tissue thickness taken from the original is drawn in anterior to the new point A -the upper point for constructing the H line lies 3mm anterior to the new lip profile in the region of subnasal ** the H line is drawn from this point to the most anterior soft tissue point on the chin. 8- Relocate the upper incisors – depending on treatment principles to allow upper lip to rest exactly on the H line, to create the desired esthetic effect. == the profile of the mouth is drawn with the upper lip on the H line and the lower lip 0.5mm anterior to the H line. 9- Superimposing the symphysis and Go Gn on both tracing the lower incisors are drawn in relation to the upper incisors. 10-The lower molars are drawn, taking into account, extraction and available space. 11-The upper molars are drawn in neutral relationship. 12-The construction is completed in the region of the point A, palate, and symphysis. Follow up studies show that VTO, growth is more easily predictable in the horizontal direction whilst vertical relationship and dento- alveolar movement were less well demonstrated. 7- Rickettes method: short method It is superior to Johnston method by 20% in that it is individualized, and it is useful for 2-3 years’ prediction. Superimposition on N Ba and registed at CC will give an idea about type of growth. Ricketts concluded that: SN increase 1mm/ year and A point increase1imm / year so SNA constant.
- 7. 7 Dr. Mohammed Alruby Y axis increase 3mm / year and NB moves faster. Long term prediction method: Rickets used this method to determine the archial pattern of growth of the mandible, he considered that normal human mandible grows by superior anterior (vertical) apposition at the ramus on a curve or an arc which is segment formed from a circle. He tried to identify the central core of the mandible cephalometrically at center of ramus (XI point) Location of XI point: XI is keyed geometrically to FH and pterygoid vertical PTv by the following steps: a- Construction of planes perpendicular to FH and PTv---- guide lines b- These guide lines are: Line tangent to sigmoid notch and perpendicular to Ptv ---–R1 Line tangent to anterior border of ramus and pass parallel to Ptv.----R3 Line tangent to posterior border of ramus and pass perpendicular through line pass through sigmoid notch----R2 Line tangent to lower border of mandible and parallel to line through sigmoid notch.---- R4 c- These constructed lines form a rectangle enclosing the ramus. d- XI point is located in the center of the rectangle at the intersection of the diagonal XI point: center of the ramus. PM: protuberance Menti: point on symphysis between concave and convex area: more stable landmark DC: point of line from XI point bisect condyle and intersect the Ba-Na line. XI-PM: line represent corpus axis. DC—XI: line represent the condylar axis. CF: intersection of FH and Ptv. Pt: junction of pterygopalatine fossa and foramen rotundum. CC: intersection of Ba- N plane and facial axis. ==Rickets concluded that there are three curves of archial growth of mandible.: Curve A: passing through (DC –XI-PM) but it did not produce enough bending and the result of mandible with obtuse angle. Curve B: passing from tip of coronoid process, touch the anterior border of the ramus through same PM, constitute segment of circle with small radius in which mandible bent excessively. Curve C: that is true arc which must be passing from point between condyloid and coronoid process and between XI point and anterior border of ramus. = he constructed a new point (eva) on the lateral surface of the ramus of the mandible, that represent the median point of stress. EVA construction: a- New line passing through XI point and parallel to R3 which R3| b- New line passing through XI point and parallel to R1 which R1| c- Eva point is located at the center of the new rectangle The curve c passing through Eva point and PM point has radius equal Eva- PM (true radius) (TR).
- 8. 8 Dr. Mohammed Alruby Rickets study: Rickets selected 50 cases of untreated Class I, malocclusion and followed cephalometrically for 30 months. And another sample of 50 cases of untreated Class II, with average age for both groups at start 8 years of age. He concluded that: 1- The distance from Sella turcica to nasion increased 1mm/ year during 8 -11 period. 2- Girls after age 12 showed little or no forward growth at nasion. 3- Boys mature later than girls, and at puberty, boys were seen to advance nasion point up to 2.5mm/ year. = in both Class II and I; Point A moves forward as same amount as N point so no changes at SNA angle. Facial plane (N-Pog) moves forward slightly faster at Pog than at N point. Use Y axis as growth axis and increased by about 3mm/ year. With my best wishes----- thanks