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Malocclusion indices


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Malocclusion indices

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  3. 3. Introduction An Index is an objective mathematical description of a disease or condition based on carefully determined criteria under specified circumstances.
  4. 4. •indices have been developed to –identify patients with treatment need –prioritize their treatment needs –be useful tools in epidemiological studies.
  5. 5. • Early methods of recording malocclusions were qualitative &used for epidemiological studies. • The more recognized qualitative methods were developed by angle, stallard, mccall &many others.these methods identified only the presence or absence of a malocclusion criterion. • In early 1960's attempts were made to develop quantitative methods to measure the severity of malocclusion to rank the need for orthodontic treatment. • These included the mal-alignment index by vankirk &pennel,drakers handicapping labio-lingual deviation index,graingers malocclusion severity estimate,summers occlusal index&many more. • Indices measuring the aesthetic factor as representative of social sufficiency have emerged as important instruments for determining ttt priorities.
  6. 6. Indices measuring occlusal variation were divided into five types by grainger in 1961.these were further divided into three categories by moyers &summers. 1)Epidemiologic: • a)Syndromic type indices of incidence & prevalence of specific symptoms or groups of symptoms for use in epidemiologic studies. • b)Indices of incipient or potential malocclusion are necessary for the conduct of preventive dental health programs. 2)Clinically diagnostic: • a)indices used as an aid to clinical diagnosis
  7. 7. • 3)Treatment: – a)indices of confirmed dental anomalies used to select the cases with the highest ttt priority from a population purely on the basis of the severity of the deformity or handicap. – b)indices pointing out the degree to which ttt requirements are being met in population. Two more types under the last category are: ( Isaacson&associates-1975) – c)indices which assess the relationship between occlusal morphology & the need for ttt based on the physiological considerations. – d)indices which assess the relationship between morphology & the need for ttt based on psychological considerations.
  8. 8. Malocclusion is ‘any deviation from normal occlusion of teeth.the teeth are in abnormal position in relationship to the basal bone of the alveolar process,to the adjacent teeth&/or to the opposing teeth.according to angle occlusion is`the normal relation of the occlusal inclined planes of the teeth when the jaws are closed’.
  9. 9. We need an index to: • Document the prevalence & severity of malocclusion, • For provision of orthodontic treatment in a community • For training of orthodontic specialists.
  10. 10. Requirements of an index: • Status of the group is expressed by a single number which corresponds to a relative position on a finite scale with definite upper &lower limits; running by progressive gradation from zero, i.e., Absence of disease to the ultimate point ,i.e.,disease in its terminal stage. • Should be equally sensitive throughout the scale. • Should correspond closely with the clinical importance of the disease stage it represents. • Should be amendable to statistical analysis. • Reproducible.
  11. 11. - Requisite equipment &instruments should be practicable in actual field situation. - Examination procedure should require a minimum of judgment. - Should be facile enough to permit the study of a large population without undue cost in time or energy. - Permit the prompt detection of a shift in group conditions,for better or for worst. - Should be valid during time.
  12. 12. METHODS OF RECORDING MALOCCLUSION The methods of recording &measuring malocclusion can be classified into two types: - Qualitative - Quantitative Qualitative methods were devised mainly for epidemiological studies. A summary of some important qualitative methods is presented in the table
  13. 13. Summary of the qualitative methods of recording malocclusion: ANGLE(1899): Classification of molar relationship devised as a prescription for ttt. STALLARD(1932): The general dental status,including some malocclusion symptoms,was recorded. No definition of various symptoms was
  14. 14. MCCALL(1944): Malocclusion symptoms recorded include:molar relationship, posterior crossbite , anterior crowding,rotated incisors,excessive overbite, openbite, labial or lingual version,tooth displacement,constriction of arches. No definition of these symptoms were specified. Symptoms were recorded in all or none manner.
  15. 15. Specific malocclusion symptoms were recorded,which included -Angle's classification of molar relation, -Arch constriction with/without incisor crowding, -Superior protrusion with incisor crowding, -Superior constriction without incisor crowding,etc.
  16. 16. BJORK,KREBS&SOLOW(1964): •Objective registration of malocclusion symptoms based on detailed descriptions. •Three parts: 1-Anomalies in Dentition : Tooth anomalies, 2-Abnormal eruption. 3- Occlusal anomalies.
  17. 17. PROFITT & ACKERMAN(1973): 5-step procedure for assessing Malocclusion: 1 - Alignment 2 - Profile 3 - Crossbite 4 - Angle classification 5 - Bite depth
  18. 18. WHO/FDI(1979): Five major groups of items were recorded: 1 - Gross anomalies 2 - Dentition 3 - Space dentitions 4 - Occlusion 5 - Orthodontic ttt need judged subjectively.
  19. 19. KINAAN & BRUKE(1981): FIVE FEATURES OF OCCLUSION MEASURED: 1 – Overjet(mm) 2 - Overbite(mm) 3 - Posterior crossbite(no of teeth in crossbite, unilateral or bilateral) 4 - Buccal segment crowding or spacing(mm) 5 - Incisal segment alignment(classified as acceptable,crowded,spaced,displaced,or rotated,following defined criteria).
  20. 20. Some methods are described below: 1)ANGLE'S METHOD OF CLASSIFYING MALOCCLUSION(1899) has been widely accepted and used since it was first published in 1899. According to him, the malocclusion is based on antero-posterior relationship of the teeth. He employed numerals I, II & III to designate the three main classes. He employed arabic numerals1,2 to denote the division of classification. Unilateral deviations were termed as sub-division. He considered maxillary first molar to be the key to occlusion
  21. 21. CLASS-I: Mesio-buccal cusp of the upper first permanent molar occludes with mesio-buccal groove of the lower first permanent molar.this class also includes cases of irregularity of individual teeth & does not include malrelation of the dental arches
  22. 22. • CLASS-II The disto-buccal cusp of the upper first permanent molar occludes with the mesio-buccal groove of the lower first permanent molar. – DIVISION-1- All the upper incisors are proclined. – DIVISION-2- All upper central incisors show retroclination &the lateral incisors overlap the central incisors. – CLASS-II SUBDIVISION Class II molar relation on one side only &class I on other side.
  23. 23. Class II Division 1 Class II Division 2
  24. 24. • CLASS III Lower first permanent molar lies mesial to upper first permanent molar by a premolar width or a cuspal width. • CLASS III SUBDIVISION Unilateral class III molar relationship &class I on other side
  25. 25. 2)PROFITT&ACKERMAN (1973): – It is based on venn diagrams. – It has 9 groups. – 5 step procedure to access malocclusion.(no definite criteria for assessment was given) i) Alignment- ideal,crowding,spacing,mutilated. ii) Profile - mandibular prominence,mandibular recession,lip profile relative to nose &chin(convex,concave,straight). iii) Cross bite-relationship of the dental arches in the transverse plane as indicated by buccolingual relationship of posterior teeth.
  26. 26. iv)Angle's classification - relationship of the dental arches in sagittal plane. v)Bite depth -relationship of the dental arches in the vertical plane,as indicated by the presence or absence of anterior open bite,anterior deep bite,posterior deep bite&posterior collapse bite.
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  28. 28. 3)WHO/FDI (1979) On the basis of the principles developed for defining &recording individual traits of malocclusion by bjork et al a simplified method was developed during the years 1969-72 working group 2 (wg2)of fdi commission on classification & statistics for oral conditions. During 1973-76, the method was field tested & modified & published in 1979.The primary objective of the assessment method was to determine the prevalence of malocclusion & dental irregularities & to estimate the treatment needs of the population as a basis for the planning of orthodontic services.
  29. 29. Summary Of Quantitative Methods Of Recording Malocclusion: MASSLER & FRANKEL(1951): Count the no of teeth displaced or rotated. (all or none assessment) MALALIGNMENT INDEX (VANKIRK & PENNEL-1959) Tooth displacement & rotation were measured (defined quantitatively)
  30. 30. HANDICAPPING LABIO-LINGUAL DEVIATION INDEX (DRAKER-1960) Measurements include cleft palate,traumatic deviations, overjet, overbite, mandibular protusion, anterior openbite, labio-lingual spread. OCCLUSAL FEATURE INDEX (POULTON & AARONSON-1961): -Measurements include lower anterior crowding, cuspal interdigitation, overbite & overjet. -Occlusion features were measured & scored according to defined criteria.
  31. 31. MALOCCLUSION SEVERITY ESTIMATE (GRAINGER-1960-61): Seven weighted & defined measurements: - overjet - overbite - anterior openbite - congenitally missing maxillary incisors - first permanent molar relationship - posterior crossbite - tooth displacement
  32. 32. Six malocclusion syndromes were defined: - Positive overjet & anterior openbite. - Positive overjet& overbite, distal molar relationship & posterior crossbite with maxillary teeth buccal to mandibular teeth. - Negative overjet, mesial molar relationship, posterior crossbite with maxillary teeth lingual to mandibular teeth. - Congenitally missing maxillary molars. - Tooth displacement. - Potential tooth displacement.
  33. 33. OCCLUSAL INDEX (SUMMERS-1966): Nine weighted & defined measurements: - molar relation - overbite - overjet - posterior openbite - posterior crossbite - tooth displacement - midline relation - maxillary median diastema - congenitally missing maxillary incisors
  34. 34. Seven malocclusion syndromes defined: - Overjet & overbite - Distal molar relation,overjet,overbite,post.crossbite, midline diastema,midline deviation. - Congenitally missing maxillary incisors. - Tooth displacement. - Posterior openbite. - Mesial molar relation, overjet, overbite, post.crossbite, midline diastema, midline deviation. - Mesial molar relation,mixed dentition analysis & tooth displacement. - Different scoring schemes & forms for different stages of devolopment- decidous, mixed & permanent.
  35. 35. TREATMENT PRIORITY INDEX (GRAINGER-1967): Eleven weighted & defined measurements: - upper anterior segment overjet - lower anterior segment overjet - overbite of upper anterior over lower anterior - anterior openbite - congenitally absence of incisors - distal molar relation - mesial molar relation - post.crossbite(maxillary teeth buccal to normal) - post.crossbite(maxillary teeth lingual to normal) - tooth displacement - gross anomalies
  36. 36. Seven malocclusion syndromes were defined: - maxillary expansion syndrome - overbite - retrognathism - openbite - prognathism - maxillary collapse syndrome - congenitally missing incisor
  37. 37. Handicapping Malocclusion Assessment Record (Salzmann-1968): Weighted measurements consist of two parts: - Intra-arch deviation-missing teeth, crowding, rotation, spacing. - Inter-arch deviation-overjet, overbite, crossbite, openbite, mesio-distal deviation.
  38. 38. Six handicapping dento-facial deformities: - facial & oral clefts - lower lip palatal to maxillary incisors - occlusal interference - functional jaw limitation - facial assymetry - speech impairment this part can only be assessed on life patients.
  39. 39. Some indices are described below: 1)Malocclusion Severity Estimate (mse-1960-61): Grainger developed the mse in the burlington research center. It can be used either on the models or on the patients. It was found to be highly reproducible. It was later revised & was called as treatment priority index.
  40. 40. 2)OCCLUSAL INDEX (SUMMERS-1966) • Based on malocclusion severity estimate with attempts to remedy its shortcomings. • The first shortcoming was remedied in part by defining normality over time, in particular equating the mixed dentition analysis with actual tooth displacement & in part by giving different weights to certain items in different dental age groups. If these items would have their norms changing as dental development proceeded. • A scoring scheme for each stage of dental development i.e; deciduous, mixed & permanent) was therefore developed & different scoring forms were used for subjects in each stage.
  41. 41. - The second shortcoming was remedied by considering the scores of all syndromes in arriving at the final score. - The third shortcoming was remedied by adjusting for normality,so that the absence of any occlusal disorder would be scored as zero.
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  52. 52. 3)TREATMENT PRIORITY INDEX(TPI-1967) Grainger modified the mse to develop the tpi. He described the index as a method of assessing the severity of the most common types of malocclusion & hence provided a means of ranking patients according to the severity of the malocclusion, degrees of handicap or their priority of treatment.
  53. 53. The pre requisites for determining the handicap was defined by grainger as: • unacceptable aesthetics • significant reduction in masticatory function • traumatic condition predisposing to tissue destruction • speech impairment • unstable occlusion • gross or traumatic defects • a few manifestations of malocclusion, such as midline diastema & slight asymmetry were rejected & also the mixed dentition analysis
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  56. 56. 4)HANDICAPPING MALOCCLUSION ASSESSMENT RECORD (HMAR-1968-SALZMANN) Handicapping malocclusion & handicapping dento-facial deformity were defined as conditions that constitute the hazard to maintenance of oral health and interfere with the well-being of the patient by adversely affecting dento-facial aesthetics, mandibular function,or speech. a cut off point was set at a score so that those patients whose scores were above the cut off point would be treated by professional personnel.
  57. 57. Treatment priority index: (urgency of ttt need): • 1) Cosmetic & functionally handicapping anomalies. • All facial congenital abnormalities,e.g;cleft lip & palate. • Extreme pre- & post-normal & vertical skeletal discrepancies. • Unerupted incisor teeth. • Extensive anterior tooth aplasia.
  58. 58. 2 - Post-normal occlusion with lip trapping (e.g;overjet greater than 10mm) -Prenormal occlusion with mandibular displacement. -Increased overbite with gingival trauma/irritation. -Severe anterior openbite involving premolar units. -Severe posterior crossbite with mandibular displacement. -Severe anterior crowding or spacing. -Impacted maxillary canines. -Aesthetically or functionally disturbing rotations.
  59. 59. 3)Deviations in space condition. -Increased overbite. -Infra-occlusion of permanent posterior teeth. -Anterior openbite involving the canine region. -Severe crowding of posterior teeth. -Spacing of posterior teeth including posterior tooth aplasia. -Aesthetic or functionally disturbing rotations.
  60. 60. 4 ) Mild deviations from normal occlusion. -Prenormal occlusion with little negative overjet or mandibular displacement. -Post-normal occlusion without other anomalies. -Increased overbite,i.e;the upper incisors extend no further gingivally than the third middle third of the lower incisors. -Minimal anterior openbite affecting the incisors only.
  61. 61. -Minimal transverse crossbite with minimal or no displacement. -Mild crowding or spacing. -Mild rotations of little aesthetic or functional significance. 5) No ttt required.
  62. 62. VARIOUS OTHER INDICES ARE DESCRIBED IN BRIEF: 1)THE MALALIGNMENT INDEX: (MASSLER & FRANKEL - 1951) This index is based on the individual tooth as the unit of occlusion.each tooth is examined by turn to determine whether it is in correct occlusion or malocclusion.the total no of maloccluded teeth in an individual is the index score for the individual.
  63. 63. A maloccluded tooth is the one which falls in one of the categories: a)buccal or lingual displacement. b)mesial or distal displacement. c)rotated. d)infraoccluded or supraoccluded.
  64. 64. The position of each tooth is assessed by judging it in relation to the adjacent teeth & contact line. Though a tooth may be maloccluded in more than one plane it is always assigned a value of one i.e;a tooth is either maloccluded or not. The total index score per person may range from zero for a dentition with no maloccluded teeth to 28 if all the teeth are maloccluded (third molars were not included in the original study). Missing teeth,extracted teeth & devolopmental anomalies of teeth are recorded separately.
  65. 65. 2)THE MALALIGNMENT INDEX (VAN KIRK & PENNELL-1959) • The index was to serve as an Epidemiological tool & provide data useful for group & comparative studies. • The index scores were meant not only to indicate severity of malocclusion but also to rank the build of problems in population groups. • Measurements are taken with the help of a specially designed plastic instrument. • The arches are divided into three segments:anterior & right & left posterior segments. • Each tooth is examined & given a score of 0,1 or 2. The individual tooth scores in each segment are summated to get the segment score & the final index score is the total sum of the six segment scores.
  66. 66. The method of scoring is as follows: • 0 - ideal alignment- the tooth does not show any apparent deviation or displacement from the ideal arch line as projected through the contact areas.
  67. 67. •1 - minor malalignment - which may be of two types- i)rotation the angle formed between the line projected through the contact areas of the observed tooth & the ideal arch line is less than 45degrees. ii)displacement i.e;both the contact areas are removed in the same direction from their position in ideal alignment but the displacement is less than 1.5mm.
  68. 68. • 2 - major malalignment which may again be again be of two types: i)rotation equal to or greater than 45degrees. ii)displacement equal to or greater than 1.5mm.
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  70. 70. 3)THE OCCLUSAL FEATURE INDEX (POULTON & AARONSON -1961): This index is meant for epidemiological surveys & is based on four characteristics of occlusion: a)lower anterior arch crowding in the canine to canine area. – 0 - no crowding – 1 - crowding of lower anterior teeth equivalent to one half the width of the lower right central incisor – 2 - crowding the width of one central incisor – 3 - crowding exceeding the width of one central incisor
  71. 71. b)cuspal interdigitation, observed in occlusion looking at the right premolar-to molar area from the buccal aspect. – 0 - cusp to groove relationship – 1 - between cusp & groove – 2 - cusp to cusp
  72. 72. c)vertical overbite,measured by that portion of the lower incisors covered by the upper central incisors in occlusion. • 0 - incisal third of lower incisors • 1 - middle third of lower incisors • 2 - gingival third of lower incisors
  73. 73. d)horizontal overjet, measured in occlusion with a small ruler from the labial surface of the upper incisors to the labial surface of lower incisors. – 0 - 0-1.5mm – 1 - 1.5-3.0mm – 2 - 3.0mm & over The values assigned to an individual correspond to the number of the grade & the total sum of the four categories gives the o.f.i.score for that individual.
  74. 74. 4)HANDICAPPING LABIO-LINGUAL DEVIATION INDEX:(DRAKER-1960): This index was meant for use in public health programs.draker defined handicap as "an extreme deviation from an accepted norm which may or may not actually exist.the index incorporates seven features or traits:
  75. 75. • Condition 1 - cleft palate 2 - traumatic deviations 3 - overjet 4 - overbite 5 - mandibular protusion 6 - open bite 7 - labio lingual spread The sum total of all the traits gives the h.l.d.score. A score of 13 & over will constitute a physical handicap.
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  77. 77. More recently many indices have been developed. Of these new indices, a few are described below: 1)Dental aesthetic index (cons et al-1986) 2)The IOTN index(brook&shaw-1989) 3)PAR index(richmond-1990) 4)Index of complexity, outcome& need(icon) 5)HLD (calmod)&hld(md)
  78. 78. 1)DENTAL AESTHETIC INDEX (1986 - JENNY & KOHOUT ) It has a clinical component & an esthetic component. The DAI links the components mathematically to produce a single score that combines the physical & esthetic aspects of occlusion. Though it was developed for use in the permanent dentition,it can easily be adapted for use in the mixed dentition stage. Instead of counting the number of missing incisors,canines &premolars,as required in the DAI regression equation, the following modification is used. When scoring a case in the mixed dentition,the space from the recently exfoliated deciduous tooth should not be scored as missing, if it appears that the permanent replacement would soon erupt.
  79. 79. The DAI has decision points along the DAI scale defining case severity levels that approximate the judgment of the orthodontists. The DAI scores of 25 & below represent normal or minor malocclusions with no or slight treatment need. The DAI scores of 26 through 30 represent definite malocclusions with treatment elective. The DAI scores 30 through 35 represent severe malocclusions with treatment highly desirable. The DAI scores 36 & higher represent very severe or handicapping malocclusion with treatment considered mandatory. The hypothetical case with a score of 39 would be considered handicapping & would be found eligible for receipt of orthodontic care in publicly funded programs in the United states.
  80. 80. 2)INDEX OF ORTHODONTIC TREATMENT NEED(IOTN-1989)(BROOK&SHAW) First described in 1989 by brook & shaw as index of orthodontic treatment priority &later renamed IOTN. The IOTN has two components,a clinical component called the dental health component& a separate esthetic component. The clinical component of IOTN is a modification of the index used by the Swedish dental board. It has five grades.(table shows them). a grade is allocated according to the severity of the worst single trait.the grade of this trait describes the priority of
  81. 81. • The esthetic component of the IOTN consists of a visual 10-point scale, which represents a wide range of dental attractiveness, illustrated by a series of 10 front view photographs arranged from no- 1(most attractive)to no-10(least attractive)as shown in the figure.
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  84. 84. 3)PEER ASSESSMENT RATING (PAR)INDEX(RICHMOND-1990) Developed at the Manchester university. It was developed to quantify how much orthodontic treatment reduces the severity of malocclusion. Scores are assigned to various occlusal traits that make up a malocclusion. The individual scores are summed & the total represents the degree to which a case deviates from normal alignment &occlusion. Improvement in the PAR index can be assessed with either the point reduction in the weighted PAR score or percentage reduction. The PAR index includes the scores of 5 individual traits: upper& lower segments,right& left buccal segments, overjet & overbite & centerline. The scoring of each component is shown in the table The raw PAR score is calculated by adding the individual components of the PAR score. Weighting is attained to various components to get the weighted PARscore.
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  87. 87. 4)Index of Complexity, Outcome and Need (ICON): This index was created so that a single index for assessing treatment inputs & outcomes is obtained. A panel of 97 orthodontists gave subjective judgments on the treatment need, ttt complexity,ttt improvement&acceptability. The occlusal traits were scored according to a defined numerical protocol. Five highly predictive occlusal traits were identified (IOTN-esthetic component,cross bite,upper arch crowding / spacing, buccal segment antero-posterior relationships,& anterior vertical relationship).
  88. 88. This new index is comprised of an assessment of dental esthetics &other relationships as described above. The scoring protocols are described in the table(used in study models). All the treatment score values greater than 43, would be considered in need of ttt. Post ttt scores of less than 31 signify acceptable end occlusion. These cut-off values were chosen to optimize the specificity&sensitivity of the index.
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  90. 90. 5)HLD(CALMOD) & HLD(MD): Maryland & California are among the states that have adopted the handicapping labio-lingual deviation (HLD) index to determine eligibility for public funding of orthodontic ttt. as a result of several lawsuits against the state,California has developed & employed. A modification of that index,used by several states rely on morphological deviations from an idealised norm to determine ttt need.
  91. 91. a)HLD(MD): Maryland uses HLD index to evaluate orthodontic need of patients who would require state funding. It has raised the cut-off from 13 to15 points & modified drakers original scoring by subtracting 2mm from overjet &3mm from overbite measurements.
  92. 92. b)HLD(CalMod) HLD index was modified in California to identify the most severe malocclusions. These were declared handicapping & their ttt medically necessary. Two qualifying exceptions that cause tissue damage were added - deep impinging bites&cross bites of individual anterior teeth with tissue destruction. Later overjets greater than 9mm & reverse overjets of 3.5mm were added as additional qualifying exceptions & unilateral posterior crossbite was added as a weighted factor. The HLD(CalMod)index uses a cutoff score of 26 points.
  93. 93. SHORTCOMINGS OF VARIOUS INDICES: 1)ANGLES: There have been many critiques of angles classification of malocclusion. His method disregarded the relationship of the teeth to the face & although malocclusion was a three dimensional problem,angles system had only taken into account antero-posterior deviations in the sagittal plane. When reliability was tested,between examiner errors as well as within examiner errors in categorizing angle class II,div2 malocclusion were relatively high.also there was difficulty associated with asymmetry between left&right sides,or those where tooth movements had occurred because of factors such as crowding&premature loss of deciduous teeth.
  94. 94. 2)WHO/FDI: • did not define the malocclusion symptoms to be recorded,thus malocclusion symptoms were recorded in all or none manner. • only a few malocclusion symptoms were selected arbitrarily as the items to be recorded. 3)MSE INDEX: • it was derived from data of 12 year old patients & therefore might not be valid for earlier stages of dental development in the deciduous or permanent dentitions. • it didn't reflect all measurements that were accumulated& • the absence of any occlusal disorder was not scored as zero.
  95. 95. 4)OCCLUSAL INDEX: - very close & careful examination is needed as subjective decisions were required in deciding whether the molar relationship is distal or mesial by half a cusp or more than half a cusp on each side. - certain degree of subjective judgment was also involved in determining displacement by 1.5 to 2mm or more than 2mm. - requires more calculations & clerical time & a bit complicated.
  96. 96. 5)TPI: • a few manifestations were rejected such as midline diastemas & slight asymmetry. • mixed dentition analysis was deleted which measures the potential tooth displacement. • inadequate for assessing the occlusion of the deciduous or mixed dentition. • inspection of TPI form reveals that distal & mesial molar relations are considered equal. • TPI values recorded in the transitional dentition do not predict the future severity of the malocclusion in the permanent dentition.
  97. 97. 6)HMAR: - the dento-facial deformities can only be assessed on life patients & not on any study models. -not precise.
  98. 98. 7)IOTN: • poor reproducibility in school settings of dental health component. • self evaluation of dental esthetics by children found only slight agreement with examiners esthetic judgment. • tendency for children to overrate their level of attractiveness compared with professional assessment. • poor agreement for esthetic component scored by calibrated examiners from photographs when compared with scores recorded clinically or from models.
  99. 99. 8)PAR: • it has been developed & validated to assess ttt entry & exits as separate phenomenon,when they are clearly part of the same clinical process. • this index have been validated against UK dental opinion & thus may not be representative in other countries. • this index has been criticized for undue leniency of residual extraction spacing,unfavorable incisor inclinations & rotations.others have found it unduly harsh on ttt with limited aims. • it does not take into account the periodontal destruction,decalcification,root resorption, dynamic occlusion & facial
  100. 100. RELIABILITY & VALIDITY OF INDICES: • The precision of an index is an ability to produce the same score or measurement when one or more examiners measure the same case at the same or different time. • The validity of an index can be defined as its ability to accurately measure what it purports to measure. • Bias,or systemic error,of an index or measurement is the magnitude & direction of its tendency to measure something other than what was intended. The score of an unbiased index should accurately reflect the intended characteristics. An index could be precise but such a case,the score will be reproducible but not an accurate potrayal of the occlusion.
  101. 101. EVALUATION OF MALOCCLUSION INDICES: Of all the indices described so far ,the OI by summers was evaluated to have the least amount of bias,is best correlated with clinical standards & has the highest validity during time.this was evaluated by many authors thro the years comparing with other indices such as HMAR,TPI,HLD,etc. Newer indices have been evaluated & correlated with other indices for their precision.
  102. 102. CONCLUSION Malocclusion is not just an invariable disease state,but a continuous spectrum of occlusal variation,occurring as a myriad of combinations & permutations of a no of heterogeneous traits or symptoms,each with its own wide range of severity & implications in creating a particular manifestation of occlusion.
  103. 103. A good method of recording or measuring malocclusion is important for documentation of the prevalence & severity of malocclusion in the population groups.this kind of data is important not only for the epidemiologist but also for the training of orthodontic professionals.
  104. 104. There seems to be no universally accepted index for measuring malocclusion,yet.Although the OI had been shown to have the least amount of bias,it still has shortcomings. Further research would therefore be needed to develop better indices or to refine the present indices so that they can be more universally accepted.many of the current indices of ttt standards show low intra & inter examiner variability when compared with those used for diagnostic or epidemiological purposes.
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