Presentation on theme: "Truly Invisible Braces: The Story of Serial Disking"— Presentation transcript:
1 Truly Invisible Braces: The Story of Serial Disking Dr JabbarifarAssociate ProfessorIsfahanUniversity School of Dentistry 2009
2 objectivepart 1Discuss the transition of the primery dentition to the permanent dentition.part 2Review a simplified Mixed DentionAnalysis procedure.part 3Discuss indications and procedures forSerial disking .
3 Part 1 - Transition From Primary to Permanent Teeth Transition of molar relationshipsTransition of IncisorsTransition of Buccal SegmentLeeway SpaceLate Mesial Shift
8 Incisor Liability Permanent incisors are larger than primary incisors This difference in size is termed "incisor liability“How does the body create enough room for the larger, permanent incisors?
9 Overcoming Incisor Liability Interdental spacing of primary incisorsIntercanine arch width growthLabial positioning of the permanent incisorsFavorable size ratio between the primary and permanent incisors
10 Arch Length Prediction from Alignment of Primary Teeth
16 Late Mesial Shift Refers to mandibular permanent molar moving mesially Good news - if permanent molars are ETE, late mesial shift allows mandibular molar to move into a Class I occlusionBad news - the above reduces arch length
17 Late Mesial Shift (cont.) FTPMolar moves intothis space...Class I
19 Part 2 Mixed Dentition Analysis Purpose: predict amount of crowding after permanent teeth come inTiming: mixed dentitionMaterials: Boley gaugeWhere: At the chair
20 4 Step Simplified MDA Basic Steps Mentally align incisors In other words…. “how far over onto the primary cuspid will it take to make the incisors straight?”Measure space left over for C, B1, B2Predict size of C, B1, B2Compare size vs. space for C, B1, B2 to determine amount of crowding
21 Step 1 MDA MethodologyMeasure mesial-distal diameter of the mandibular incisors, sum and divide by two
24 Step 2 MDA Methodology Select a midline point Expand the Boley gauge to the amount determined in Step 1Mark the point on each primary cuspid from the midline pointThis represents the space required for well aligned incisors
26 Step 3 MDA MethodologyMeasure from the point on each cuspid (derived in Step 2) to the mesial of the first permanent molarThis represents the space available for the permanent cuspid and bicuspids (C, B1, B2)
29 Step 4 MDA MethodologyTo the number derived in Step 1, add 10.5 mm for the mandibular teethThis represents the size of the permanent cuspid and bicuspids in each quadrantSubtract the number determined in Step 4 (the predicted size of C, B1, B2) from the number determined in Step 3 (the amount of space for C, B1, B2) for both sides of the arch
30 MDA MethodologyIf the space available is less than the amount of tooth mass, a negative number will resultThis number is the predicted amount of crowding
32 Allowance for Late Mesial Shift If permanent molars are end to end, mandibular molar should move mesially to obtain Class I interdigitation.This will decrease the arch length available forFigure 1.7 mm. per side with ETE relationship.
33 MDA Procedure Maxillary Arch Mentally align the maxillary incisors as was done in the mandibular archMeasure the space left over for the maxillary C, B1, B2Add 11.0 mm. to 1/2 the sum of the MANDIBULAR INCISORS to predict the size of the maxillary C, B1, B2Subtract the predicted size from the space available
34 Part 3 Serial Disking Result without treatment Description of Ideal PatientDescription of TechniqueSteps in Serial Disking
70 If You Can’t Disk Enough… and <5 mm. Crowding... Extract mandibular primary cuspidsSupport with bilateral holding archMandibular incisors will generally alignJust because 5 mm. of crowding is predicted does not mean it is an extraction case! Why?NEXT SLIDE
71 Other Factors to Consider Tooth size prediction is at approximately 75 percentiletherefore….. Tendency is to overestimate crowdingMDA does not take into account:angulation of incisorsarch formCurve of Spee