INDIAN DENTAL ACADEMY Leader in continuing dental education
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CEPHALOMETRIC DIAGNOSIS FOR FUNCTIONAL APPLIANCE THERAPY www.indiandentalacademy.c om
INTRODUCTION Most orthodontic therapies, regardless of the appliance used, benefit significantly from the use of cephalometric analysis in the treatment planning and routine management of treatment sessions. Each age group has its own special demands for information and needs specific criteria to obtain that information. www.indiandentalacademy.com
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Cephalometrics enables the localization of the apparent anomaly and provides a differentiation between skeletal and dentoalveolar malocclusions.
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GROWTH ď ˇ Direction
horizontal vertical
ď ˇ Amount
low average high
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ď ˇ MALOCCLUSION skeletal dentoalveolar skeletal and dentoalveolar
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THERAPEUTIC POSSIBILITIES Skeletal - channel the growth pattern and achieve morphological and functional changes. Dentoalveolar – eliminate abnormal environmental factors.
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ď ˇ If not possible to correct skeletal type of malocclusion by growth - compensatory form of therapy is needed. extractions specific anchorage control orthognathic surgery
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Comprehensive cephalometric analysis is needed for treatment planning. Removable or fixed Functional or non functional
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Natural head position ď ˇ Careful positioning of the patient in the cephalostat allows one to relate head and neck position to horizontal and vertical lines. ď ˇ Determination of the natural head posture in relation to the true vertical is a starting point in the aesthetic examination of the facial profile. www.indiandentalacademy.com
Upright position Ask the patient to look straight in to the mirror[to look at his eyes] which is placed 150 cm from the ear rods.FH plane in parallel to the floor True vertical is registered as a plumb line suspended over the cassette holder in the occipital region. Some recent cephalostats incorporate a light beam that can be oriented correctly to the FH Simple fluid level device can be used [1987 A O] www.indiandentalacademy.com
ď ˇ Broadbent [1948]and Brodie[1940,1941.1946] Face grows downwards and forwards from the base of the skull along the Y axis or facial axis structures in the anterior cranial base were selected for superimposition of serial cephalometric tracings to demonstrate the growth changes. www.indiandentalacademy.com
ď ˇ Coben [ 1955 ] superimposition of the tracings on anterior cranial base has the major disadvantage of ignoring growth at the primary growth site in the base of the skull,the speno occipital synchondrosis,which has a fundamental influence on facial growth. www.indiandentalacademy.com
Coben [1955] Growth and angulation of cranial base affects structure of the face. Growth of the head is observed more accurately by superimposition at basion. The wedge of the face opens by growth upwards and forwards along the cranial base and downwards and forwards along the mandibular plane. www.indiandentalacademy.com
Coben[1955] ď ˇ The opening of the facial wedge increases facial height to accommodate growth in the height of the nasal sinuses and to accommodate the successional teeth ,deciduous to permanent teeth.
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ď ˇ Frankel and Frankel ,Clark followed Cobens concept .they used Basion as the fulcrum point for analysis of growth changes in the facial rectangle with the FH.
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Ricketts analysis The Ricketts triangle defines the face in profile as a wedge shaped triangle attached to the undersurface of the cranial base. The base of the triangle extends from Basion to Nasion which defines the cranial base plane Facial plane extends from the Nasion tangent to the chin at the Pog to define the angulation of the face in the anterior plane. The mandibular plane is the third side of the triangle defining the angulation of the face in the anterior plane. www.indiandentalacademy.com
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ď ˇ The Ricketts triangle is bisected by the facial axis extending from Pterygoid to Gnathion to define the direction of the growth of the chin.
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The facial rectangle The facial rectangle is formed to frame the face. The formation of the facial rectangle helps to define the relative position and angulation of cranial ,maxillary,mandibular and dentoalveolar structures. The rectangular frame work makes it easier to identify areas where growth departs from normal in the facial pattern Facial rectangle is constructed to define the upper,lower,anterior,posterior limits of the face. www.indiandentalacademy.com
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FH plane Nasion horizontal Menton horizontal Nasion vertical Basion vertical Pterygoid vertical www.indiandentalacademy.com
ď ˇ To achieve ideal facial proportions the integral parts of the facial structures must be well related in size ,shape and position. ď ˇ In well balanced face the FH and maxillary planes approximately parallel to the upper maxillary plane and optic plane[Bimler 1957],and relate closely to the true horizontal in the natural head position. www.indiandentalacademy.com
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Ricketts [ 1960] ď ˇ Parallel development of facial axis condylar axis upper incisor
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Definition of skeletal planes
Cranial base - nasion[N] to basion[B] Mandibular base plane-menton[Me] to gonion[Go] Facial plane-nasion[N] to pogonion[Po] Facial axis-pterygoid point[Pt] to gnathion[Gn] Condyle axis-center of the condyle to Xi point Maxillary plane-anterior nasal spine[ANS] to posterior nasal spine[PNS] A to Po – A point to pogonion[P] www.indiandentalacademy.com
Dental planes- functional occlusal plane; distal the intersection of the first molars to the intersection of the first premolars. Long axis of the upper incisor Long of axis of the lower incisor
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Soft tissue planes ď ˇ Nasal plane- outline of the nose from the root to the tip ď ˇ Aesthetic plane-the tangent to the nose and chin
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Craniofacial angular analysis Cranial base angle- cranial base to horizontal registration line Mandibular plane angle- angle of the mandibular plane to horizontal[ 27deg+ or_ 3 deg] Craniomandibular angle-angle of the cranial base to the mandibular base plane [54deg+/-5 deg] Facial plane angle angulation of facial plane to nasion vertical [-3 deg dev 3] www.indiandentalacademy.com
ď ˇ Facial axis angle facial axis to pterygoid vertical norm 27 deg dev 3deg[determine the direction of the growth of the chin]
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Condyle axis angle –condyle axis to pterygoid vertical[27 deg 4 dev] Mandibular arch- angulation of condyle axis to the body of the mandible[Xi to Pm] 26 deg,4 deg dev at age 8 yrs Increases 0.5 per yr high angle->deep bite,square mandible,prognathic low angle>openbite,retrognathic www.indiandentalacademy.com
ď ˇ Craniomaxillary angle- cranial base plane to the maxillary plane [norm 27 deg 3 dev] ď ˇ Maxillary deflection-angulation of the maxillary plane to the horizontal [0 deg dev 3]
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Dental analysis Upper and lower incisors are related to the anterior vertical Upper incisor angle-upper incisor to anterior vertical[25 deg7dev ] Lower incisor angle-lower incisor to anterior vertical[25 deg4 deg dev] Interincial angle-angle between upper and lower incisor[ 128deg6dev] www.indiandentalacademy.com
Position of dentition ď ˇ Position of upper dentition-distal of upper molar to pterygoid vertical[pts age +/-3mm] ď ˇ Position of lower incisors-lower incisor to APo line[1mm dev 2 mm]an important indicator of stability of the lower incisor position. www.indiandentalacademy.com
Soft tissue analysis ď ˇ Nasal angle- angulation of the nose to the anterior vertical ď ˇ Lower lip to E plane- distance of the lower lip to the line tangent to the nose and chin[2mm at age 8decreases by 0.2m per yr]
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Assessment of functional balance ď ˇ Functional guidance of upper and lower incisors is determined by the relationship of the tips of the incisors and the hinge axis of the mandible and can be measured relative to the horizontal axis ď ˇ The interincisor guidance angle indicates anterior or posterior occlusal interferences www.indiandentalacademy.com
ď ˇ Maxillary incisal guidance angle; maxillary incisor/hinge axis;angle to the horizontal.line from the tip of the upper incisor to hinge axis[27deg3dev] ď ˇ Mandibular incisal guidance angle; mandibular inciosr/hinge axis;angle to the horizontal,line from the tip of the lower incisor to hinge axis[27 deg dev3] www.indiandentalacademy.com
ď ˇ Interincisor angle- angle between upper and lower incisal guidance axes. - measures freedom of the mandibular movement in the protrusive function - Increased possitive angle indicates incisal interference - Increased negative angle indicates posterior interference www.indiandentalacademy.com
ď ˇ Occlusomaxillary plane angle-functional occlusal plane to the mandibular plane[12deg dev3] ď ˇ Occlusomandibular plane angle-[14 deg dev3dg] affects the prognosis for opening or closing the bite High angle is favorable for opening the bite, lower angle is favorable for closing the bite
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Craniofacial linear analysis ď ˇ Cranial ,maxillary,mandibular length are compared by measurement from the basion,which represents the fulcrum of craniofacial growth ď ˇ Cranial length and the mandibular length should close to a 1/1 ratio and maxillary length should be less than 10mm to the ideal proportions . www.indiandentalacademy.com
Cranial length- basion to nasion [105.7mm at age 8dev 4.5mm increase by 1.3mm per yr] Maxillary length-basion to point A [94.5mm at age 8 dev 4.5increased by 1.25mm per year] Mandibular length-basion to pogonion m[103.5dev5.5 increased by 2.3mm per year] www.indiandentalacademy.com
Anterior cranial base length ; sella to nasion [74mm at age 8dev 3.3 increased by 0.75] Mandibular corpus length ;gonion to pogonion[70.8mm at 8yrs age increased by 1.65mm per year] Maxillary position;A point to nasion vertical Mandibular position ; pogonion to nasion vertical [-10mm at age 8 yrs,decreases by 0.75mm per year] www.indiandentalacademy.com
ď ˇ Convexity; A point to facial plane; mean 2.5mm at age 8,decreases by 0.1mm per year increased convexity in class II cases decreased convexity in class III cases www.indiandentalacademy.com
ď ˇ Mesognathic Prognathic retrognathic ď ˇ Mesofacial Brachyfacial Dolichofacial [Ricketts 1960] www.indiandentalacademy.com
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ď ˇ The various measurements used in cephalometric criteria can be divided into 3 groups. analysis of facial skeleton analysis of jaw bases analysis of dentoalveolar relationship
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ANALYSIS OF FACIAL SKELETON ď ˇ 3 angular saddle angle N S Ar articular angle S Ar Go gonial angle Ar Go Me ď ˇ 4 linear anterior facial height posterior facial height anterior cranial base length posterior cranial baselength www.indiandentalacademy.com
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SADDLE ANGLE N S Ar Helps in assement of the relationship between anterior and posterolateral cranial bases. Large angle – posterior condylar position/mandible is placed posteriorly with respect to the cranial base and the maxilla [unless the deviation in the fossa is compensated for by angular measurement[articular angle] and linear relationship[length of the ramus]. www.indiandentalacademy.com
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ď ˇ A non compensated posterior positioning of the mandible caused by large saddle angle is very difficult to influence with the functional appliance therapy.
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ARTICULAR ANGLE S Ar Go Constructed angle that lies between the upper and lower parts of the posterior contours of the facial skeleton. large angle retrognathic mandible small angle prognathic mandible This Can be influenced by the orthopaedic therapy.
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ARTICULAR ANGLE ď ˇ Decreases with the anterior positioning of the mandible with closing the bite or with mesial migration of the posterior segment of the teeth. ď ˇ Increases with the posterior relocation of the mandible with opening the bite or with the distal driving of the molar teeth. www.indiandentalacademy.com
GONIAL ANGLE Ar Go Me This is the angle formed by the tangent to the body of the mandible and posterior border of the ramus It expresses not only the form of the mandible but also information on its growth direction. www.indiandentalacademy.com
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GONIAL ANGLE Small or acute - horizontal growth pattern - favourable condition for the anterior positioning of the mandible with activator. Large angle – activator treatment is contraindicated or the appliance must be constructed by taking into account the growth pattern. www.indiandentalacademy.com
FACIAL HEIGHT Linear millimetric measurement Posterior facial height S Go anterior facial height N Me Posterior facial height in the longitudinal study group of 9 yr old children with a horizontal growth pattern[69.5mm] is longer than that of the vertical grower[64.1mm] www.indiandentalacademy.com
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JARABACK RATIO
POSTERIOR FACIAL HEIGHT X 100/ANTRIOR FACIAL HEIGHT. Less than 62% vertical growth pattern More than 65% horizontal growth pattern www.indiandentalacademy.com
ď ˇ Assesment of the growth direction is very important in functional appliance therapy to determine wether fuctional appliance can be indicated or not for construction details for type of construction bite.
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Cranial base lengths
Anterior cranial base length
Se N
posterior cranial base length
S Ar
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Anterior cranial base length ď ˇ Measurement is made using the centre of the superior entrance to the sella turcica as a reference point. ď ˇ The correlation of this criterion to the length of the jaw bases enables an assesment of the proportional averages of the bases. ď ˇ Longitudinal study 9 yr old 68.8 in horizontal grower 63.8 in vertical grower. www.indiandentalacademy.com
Posterior cranial base length Lateral cranial base length S Ar The magnitude of this dimension is dependent upon the posterior facial height and the position of the fossa Short posterior cranial base – vertical growth pattern- poor prognosis for functional appliance therapy. www.indiandentalacademy.com
Posterior cranial base length ď ˇ In a 9 yr old children with horizontal growth pattern ,the average length was 32.3 mm with a groth increment of 9.16mm in the following 6 yrs as apposed to 30mm and an increment change of 4.47mm in vertical growth pattern.
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Analysis of the jaw bases Angles between the vertical reference lines – show sagittal relationship - S N A,S N B Angles between horizontal reference linesassists in vertical relationship of parts Base plane angle Inclination angle Linear mesurements- maxillary base mandibular base length of the ascending ramus www.indiandentalacademy.com
S N A angle ď ˇ This angle expresses the sagittal relationship of the anterior limit of the maxillary apical base [point A] as related to the anterior cranial base large – prognathic maxilla small- retrognathic mandible 9yrs age average 79.5 degree horizontal 79.73degree vertical 79degree. 15yrs age average 81.28 degree horizontal 81.57 degree www.indiandentalacademy.com vertical 80.57 degree
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S N B angle ď ˇ Expresses the sagittal relationship of the anterior apical base of the mandibular arch and the anterior cranial base. small angle retrognathic mandible large angle prognathic mandible ď ˇ Small S N B with retrognathic mandible – indicates functional appliance therapy. www.indiandentalacademy.com
ď ˇ A posteriorly located mandible can be large or small ď ˇ If it is small prognosis for anterior positioning in mixed dentition is good.since a larger growth increment can ususally be expected.
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S N B angle ď ˇ The average angle and growth increment in the horizontal facial type is much larger than in the vertical growth pattern ď ˇ 9 yrs age- 77.2degree horizontal facial type 15 yrs age 80.5degree ď ˇ 9yrs age 74.3 degree vertical facial type 15 yrs age 75.9 degree www.indiandentalacademy.com
Basal plane angle The basal plane angle expresses the angle between the maxillary and the mandibular jaw bases and is also used to determine the inclination of the madibular plane itself. Horizontal growth pattern- small angle 9 yrs age-13.4 degree,15 yrs age- 20.5degree vertical growth pattern – large angle 9 yrs age- 32.9 degree,15 yrs age-30.9degree www.indiandentalacademy.com
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Inclination angle ď ˇ Inclination angle gives an assesment of the inclination of the maxillary base . ď ˇ It is angle formed by the Pn line[a perpendicular from soft tissue nasion]and the palatal plane. large angle- expresses upward and forward inclintaion small angle- downward and backward rotation of the anterior end of the palatal plane or maxillary base. www.indiandentalacademy.com
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Linear measurement of the jaw bases ď ˇ When determining the indications of the functional appliance therapy ,the length as well as the position of the jaw bases should be assesed. ď ˇ The length of the maxillary and the mandibular jaw bases and of the ascending ramus are measured relative to the length of the Se N is calculated using the following formula N –Se: mandibular base 20: 21 ascending ramus:mandibular base 5:7 maxillary base:mandibular base 2:3 www.indiandentalacademy.com
Rotation of the jaw bases ď ˇ Basal plane angle inclination angle evaluate the rotation of the upper and lower jaw bases. ď ˇ They help in - indication - construction details of the functional appliance therapy
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Rotation of jaw bases ď ˇ Mandibular rotation occurs due to direction and mutual relationship of growth increments in posterior [condylar] and anterior[sutural or alveolar] growth in the facial skeleton. condylar growth
sutural or alveolar growth increments
con > sutural - H growth pattern` if equal increments – parallel growth down the y axis can be observed.www.indiandentalacademy.com
Remodelling of the mandible Occurs in the
gonial area symphyseal area
INTERMATRIX ROTATION Apposition in gonial area > resorption in symphyseal area - horizontal rotation Resorption in gonial area >apposition in symphyseal area - vertical rotation www.indiandentalacademy.com
ď ˇ Intermatrix rotation is due to function of periosteal matrix MOSS
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Matrix rotation
Rotation of the mandible in its neuromuscular envelope in toto in vertical or horizontal direction
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ď ˇ Rotation of the mandible is growth dependent functional dependent ď ˇ Inclination of the maxilla [can be observed by inclination angle] stable non growth dependent environmental factors can influence www.indiandentalacademy.com
Environmental influences Neuromuscular dysfunction Occlusal forces Gravity Nasorespiratory malfunction can be responsible for the rotations in the maxilla.
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ď ˇ Inclination of the maxillary base also influences the occlusal relationship. ď ˇ Combination of these two factors results in dentoalveolar malocclusion.
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Implant studies of jaw rotation 1960 Bjork and co workers Internal rotation rotation that occurs in the core External rotation remodelling of jaw by surface changes Overall change in the orientation of each jaw ,as judged by the palatal plane and mandibular plane,results from combination of internal and external rotation. www.indiandentalacademy.com
It is easier to visualize the internal and external rotation of the jaws by considering the mandible first. The core of the mandible is the bone that surrounds the inferior alveolar nerve. Functional processes - alveolar process muscular process condylar process Place implants in stable bone away from the functional processes. www.indiandentalacademy.com
BJORK and SKIELLER Matrix rotation - rotation around the condyle Intramatrix rotation- rotation around the core of the mandible Forward rotation – more growth posteriorly _ negative sign Backward rotation_ more growth anteriorly _ possitive sign www.indiandentalacademy.com
Total rotation BJORk rotation of mandibular core relative to cranial base implants PROFFIT rotation of the mandibular plane relative to the cranial base
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ď ˇ True rotation - SOLOW and HOUSTON -rotation of the mandibular core relative to the cranial base implants.
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Mutual relationship between the rotation of jaw bases ď ˇ Rotation of the mandible can be decisive in determining the vertical proportions of the facial skeleton. horizontal rotation ant face height is short vertical rotation
ant face height is long
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Rotation of the maxilla It is less easy to divide the maxilla into core and functional processes because there are no muscle attachments analogous to that of the mandible. Implants placed above the maxillary alveolar process can show the rotation of the maxilla.this internal rotation is analogous to intramatrix rotation of the mandible.[forward or backward] At the same time of internal rotation of maxilla ,there will be resorption of bone near the nasal side and apposition of bone on palatal side ,in the anterior and posterior parts of palate.[external www.indiandentalacademy.com rotation]
Maxillary rotation External rotation of the maxilla is equal in magnitude and opposite in direction to the internal rotation,so that the two rotations cancel and net change in the palatal plane is zero. www.indiandentalacademy.c om
Short face type Short anterior lower facial height Excessive forward rotation of the mandible during growth resulting from increased internal rotation and decreased external rotation Square jaw,horizontal palatal plane,square gonial angle,deep bite ,crowded incisors,low mandibular plane angle. www.indiandentalacademy.com
Long face type Excessive lower anterior facial height Palatal plane rotates down posteriorly Mandible shows downward and backward rotation with increased mandibular plane angle. Openbite malocclusion,mandibular deficiency www.indiandentalacademy.com
Interaction between tooth eruption and jaw rotation ď ˇ The path of eruption of the maxillary teeth is downward and forward.In normal growth the maxilla usually rotates a few degrees forwards but frequently rotates slightly backwards. ď ˇ The eruption pattern in the mandible is upward and forward. The normal internal rotation carries the jaw upward and forward www.indiandentalacademy.com
Because the internal jaw rotation of the mandible tends to upright the incisors ,the molars migrate mesially further than the incisors resulting in arch length deficiency
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Linear measurements of jaw bases ď ˇ When determining the functional appliance therapy the length as well as the position of the jaw bases should be assesed. ď ˇ lengths of the maxillary base mandibular base ascending ramus are measured relative to the length of the Se-N. www.indiandentalacademy.com
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ď ˇ The ideal dimension relative to the length of Se-N is calculated using the following formula. N-Se : mandibular base
20:21
ascending ramus:mandibular base 5:7 maxillary base:mandibular base 2:3 www.indiandentalacademy.com
Extent of mandibular base ď ˇ This is determined by measuring the distance GoPg [projected perpendicular to the mandibular plane] ď ˇ Ideal value
Se-N + 3 till 12 yrs Se-N +3.5 after 12 yrs
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Extent of mandibular base H grower - growth increments will be more - average length will be more v grower - growth increments will be less - average length will be less when compared with h grower www.indiandentalacademy.com
Extent of maxillary base This is determined by measuring the distance between the posterior nasal spine and point A projected perpendicularly to the palatal plane. Can be evaluated by N-Se distance length of the mandible Maxillary growth increment < mandibular growth increment www.indiandentalacademy.com
ď ˇ Since the growth potential of mandibular base is greater than that of maxillary base ,the SNB angle increases and the ANB angle decreases. ď ˇ The growth advantage with the mandible outgrowing the maxilla by upto 5mm helps in the treatment planning of functional appliance therapy.
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Length of the ascending ramus ď ˇ The distance between Go and Cd ď ˇ FH plane is constructed and is intersected by a tangent to the ramus .point of intersection represents constructed Cd.
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Construction of ideal FH. ď ˇ The distance between the soft tissue nasion and the palatal plane is bisected along the Pn line .from the point thus created ,a straight line [h line] is drawn parallel to the Se N plane.this become the ideal FH plane.
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ď ˇ Length of the ramus is important for determining the posterior facial height and subsequent relationship to the anterior facial height. ď ˇ Ramus tends to be longer in H growers when compared to that of V growers. www.indiandentalacademy.com
Evaluation of the length of the jaw bases ď ˇ If the length of the mandibular base corresponds to the distance N Se[mandibular base=N Se + 3mm].this expresses the age related normal mandibular length,we can expect average growth increment. ď ˇ If the base is shorter the growth increment will be higher. www.indiandentalacademy.com
Retrognathic mandible ď ˇ Mandibular jaw base - short long ď ˇ Short long
growth deficiency functionally retruded position temporal fossa itself is superior and posterior www.indiandentalacademy.com
Functionally retruded position This can be due to
overclosure occlusal guidance
Treatment eliminate the forced guidance ,upward and backward path of closure in either the mixed or permanent dentition. Prognosis is good for functional appliance therapy www.indiandentalacademy.com
Temporal fossa Temporal fossa itself can be positioned posteriorly and superiorly. Hence posterior positioning of the mandible Discrepancy is not compensated even by the long madibular base Prognosis poor for the functional appliance therapy www.indiandentalacademy.com
The maxillary base ď ˇ There are two ideal values for the evaluation of the length of the maxillary base related to distance from N Se related to the length of the mandibular base. www.indiandentalacademy.com
Ascending ramus ď ˇ The evaluation of the ramus length is performed in a similar way to that of the maxillary base. ď ˇ If the ramus length is too short in relation to the other proportions ,a large amount of growth can be expected under the supposition that the mandible is growing normally.
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ď ˇ Maxillary base
Mandibular base
facial skeleton is proportionate
Ramus length www.indiandentalacademy.com
Morphology of the Mandible ď ˇ To enhance the differential diagnosis ,the morphological chracterstics of the mandible have to be taken into consideration.. ď ˇ Various facial types reflect to some extent the morphology of the mandible.
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Orthognathic facial type Ramus and body – fully developed Width of the ascending ramus is equal to height of the body of the mandible ,including the alveolar process with the incisors Condylar and coronoid processes are in same plane Symphysis is well developed. www.indiandentalacademy.com
Retrognathic facial type Corpus is narrow particularly in the molar region . The symphysis is narrow and long The ramus is narrow and short The coronoid process is shorter than the condylar process Gonial angle is obtuse or large www.indiandentalacademy.com
Prognathic facial type Corpus is well developed and wider in the molar area The symphysis is wider in sagittal plane The ramus is wide and long Gonial angle is acute or small. www.indiandentalacademy.com
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ď ˇ The prognathic type of mandible grows horizontally.even if there is an average or slightly vertical growth direction in the mixed dentition ,a shift of the mandible to a horizontal growth direction can be expected in the following years.
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In a retrognathic type of mandible , a shift of the growth pattern in the opposite direction is less likely to be expected.
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The dentoalveolar analysis Assessment of the inclination and position of the incisors with respect to the anterior cranial base,to their apical bases and to each other plays an important part in indication construction and management of functional appliance www.indiandentalacademy.c om
Axial inclinations of the incisors The upper incisors – the long axis of the maxillary incisors as viewed on the lateral cephalogram is extended to intersect the SN cranial base line,and the posterior angle is measured. Upto 7 th yr of life - 94 deg to 100 deg after 1 to 2 yrs of post eruption angle increases to 102 degree. www.indiandentalacademy.com
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ď ˇ Increased angle between SN and upper inciosr indicates incisor procumbency. ď ˇ Incisor protrusion requires lingual tipping which can be corrected by the removable appliances if there is adequate space.
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Lower incisors Posterior angle between long axis of the lower incisors and the mandibular plane is the classic method of assessing the axial inclination of the lower incisors. The average value is 90 degrees The smaller angle indicates lingual tipping of the incisors – advantageous for functional appliance therapy [activator] If the lower incisors are proclined already anterior repositioning with simultaneous correction of incisor inclination has to be done. www.indiandentalacademy.com
Position of incisors Linear measurements help to assess the position of the incisors with respect to the profile Most common method used is to measure the distance of the incisal edges to the N Pog line. [facial plane] Upper incisors – 2 to 4 mm anterior to this line Lower incisors- 2mm anterior or 2mm posterior to this line. www.indiandentalacademy.com
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To correct axial inclination alone – removable appliance[if enough spcaing is present] To achieve bodily movement fixed appliance therapy Incisors behind the line can be moved forward,since space is available Incisors that are anterior to the line need to be moved posteriorly need space. www.indiandentalacademy.com
Along with sagittal discrepancy ,dental discrepancy have to be considered[crowding] During the mixed dentition period the mandibular growth increment is more which results in drifting of the lower terminus of the reference line in forward direction Hence amount and direction of the growth spurt should be considered in mixed dentition when planning the ideal position of the incisor at the end of the treatment www.indiandentalacademy.com
Cephalometric evaluation of treatment progress ď ˇ One of the most important tasks of cephalometrics is to objectively assess the changes induced by therapy ,combined with growth and development ,as treatment progresses.
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ď ˇ There are 7 linear measurements that expresses the growth increments.It is possible to compare the measured growth increments with the average values ,differentiated according to the morphogenetic pattern.
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The seven linear measurements S-N S-Gn S-Go N-Me Mandibular base Maxillary base Ramus www.indiandentalacademy.com
They assist in determining wether the growth increments and direction at that point in treatment are high or low and favorable or unfavorable in the skeletal areas of greatest concern.
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Evaluation of tongue posture To make important decisions such as glossectomy Assessment is made on lateral cephalogram taken in the postural rest position and habitual occlusion.exposure is adjusted to visualize the soft tissue.. Size of the tongue can be measured in the occlusal film. www.indiandentalacademy.com
Drawing the baseline Should satisfy following criteria greatest possible area of the tongue should lie above the reference line The baseline should be independent of variations in skeletal structures Its relation to the tongue should not change with changes in position of the mandible www.indiandentalacademy.com
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Drawing the baseline It should remain constant in relation to changes in tongue position. It should relate to the anatomical and functional properties of the tongue The measurement should be an easy one to make and replicate. www.indiandentalacademy.com
I the incisal margin of the lower incisor V the most caudal point on the shadow of the soft palate or its projection on to the reference line M the tip of the distobuccal cusp of the lower first molar I and M are connected by a straight line ,which is extended to V to form a reference line .it has following advantages: www.indiandentalacademy.com
ď ˇ A relatively large part of the tongue as seen on the cephalogram normally lies superior to the line. ď ˇ The line does not depend on skeletal relationships. ď ˇ Changes in the tongue position do not effect the reference line.
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After construction of reference line ,the line is bisected between I and V.This point is called O . A line perpendicular to the palatal contour is constructed from point O. A transparent template has been developed in such a way that the base line of the template coincides with the constructed reference line ,where as the vertical reference line at O. From O,at which the three lines meet four more lines are constructed.[7 lines with 30 degree angle to each] www.indiandentalacademy.com
ď ˇ Assessment of the tongue size from the occlusal cephalogram requires measuring the distance between the superior tongue surface and the roof of the mouth.this is done along the seven constructed lines . ď ˇ The results of the measurements made from tongue template may be expressed by graphs.palatal vault may be represented by a horizontal line ,and the seven single measurements may be shown by the curve. www.indiandentalacademy.com
ď ˇ The distances between the reference line and 7 points on the constructed curve graphs the relationship of the superior surface of the tongue with the palatal vault and soft palate to the tip of the uvula. ď ˇ The posture of the tongue can be evaluated by measurements taken from the postural rest lateral cephalogram.The occlusal position is taken as zero ,with changes in rest position given as positive or negative figures.[possitive- if the tongue is higher in rest position when compared to that of the position at occlusion] www.indiandentalacademy.com
ď ˇ Tip of the tongue is more retruded in class II malocclusion. ď ˇ Tip of the tongue is placed more forward in class III malocclusion
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Evaluation of lips Lips must be examined as carefully as tongue.the external balancing factors are as important as those working from inside. Configuration of the lips should be studied in relaxed position to assess the competency. Competent , incompetent, potential incompetent Some cases lower lips can be hypertonic,everted ,redundant and has excessive amount of tissue. www.indiandentalacademy.com
Schwarz analysis 3 reference lines are constructed on lateral cephalogram H line- corresponds to Frankfort horizontal. PN line – perpendicular to the H line at soft tissue Na. PO line- perpendicular from orbitale to the H line. www.indiandentalacademy.com
Schwarz analysis Between the two constructed perpendicular lines is what Schwarz terms the GPF or Gnathic profile field. In normal proportions the upper lips touches the PO line ,where as the lower lip lies one third the width of the GPF posterior to it. The oblique tangential line T is constructed by joining the subnasale [Sn] ,at the junction of the upper lip and the nose,to soft tissue Pog,the most anterior point on the profile curvature of the symphysis. www.indiandentalacademy.com
Schwarz analysis
ď ˇ In ideal case the T line bisects the vermillion border of the upper lip and touches the anterior vermillion curvature of the lower lip.
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Ricketts lip analysis ď ˇ The reference line used by Ricketts is similar tot hat of schwarz T line but is drwan from the tip of the nose to the soft tissue Pog. ď ˇ In a normal relationship ,the upper lip is 2mm to 3mm behind the line and the lower lips is 1 mm to 2 mm behind it. www.indiandentalacademy.com
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Steiners lip analysis The upper reference point for the steiner analysis is at the center of the S shaped curve between the tip of the nose and Sn. Soft tissue Pog is the lower terminus If the lips lie behind this reference line ,they are too flat,and the lips lying infront this line are too prominent. www.indiandentalacademy.com
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Holdaway lip analysis ď ˇ It is a quantitative assessment of the lip configuration. ď ˇ Holdaway measures the angle between the tangent to the upper lip from soft tissue Pog and the NB line.the angle between these two lines is called H angle.
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Holdaway lip analysis With an ANB angle of 1 degree to 3 degrees,the H angle should be 7 degrees to 8 degrees. Changes in the ANB angle mean change in the ideal H angle. Holdaway defines the ideal profile as follows : www.indiandentalacademy.com
The ANB angle should be 2 degrees,and the H line angle should be 7 degrees to 8 degrees. The lower lip should touch the soft tissue line that connects Pog and the upper lip and extends to Sn .the relative positions of the nose and the upper lip should be balanced [ the soft tissue line bisects the Sn s shaped curve ] The tip of the nose should be 9mm anterior to the soft tissue line[normal at age 13 yrs] There should be no lip tension on closure www.indiandentalacademy.com
ď ˇ The upper lip is tensed if the difference between the thickness of the upper lip is greater than plus or minus 1 mm _ Holdaway ď ˇ Following the elimination of lip tension ,each 3mm retraction of the upper inciosrs will result in 1 mm retraction of the upper lip. www.indiandentalacademy.com
Conclusion Orthodontic and dentofacial orthopaedic techniques have the potential to produce dramatic changes in the facial appearance that may be beneficial or detrimental according to the quality of treatment planning .successful treatment depends upon the accurate analysis of the facial growth pattern before treatment ,and prediction of future growth trend to select the appropriate technique to produce the best long term functional and aesthetic result within the growth potential of the individual patient www.indiandentalacademy.com
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