The Evolution of Primary to Permanent Dentition: A Comprehensive Analysis

1. Truly Invisible Braces: The Story of Serial Disking Dr Jabbarifar Associate Professor IsfahanUniversity School of Dentistry 2009

2. objective part 1 Discuss the transition of the primery dentition to the permanent dentition. part 2 Review a simplified Mixed Dention Analysis procedure. part 3 Discuss indications and procedures for Serial disking .

3. Part 1 - Transition From Primaryto Permanent Teeth • Transition of molar relationships • Transition of Incisors • Transition of Buccal Segment • Leeway Space • Late Mesial Shift

4. Flush Terminal Plane Distal Mesial

5. Mesial Step Distal Mesial

6. Disto Step Distal Mesial

7. Mesio Step Mesial Distal

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 incisors • Intercanine arch width growth • Labial positioning of the permanent incisors • Favorable size ratio between the primary and permanent incisors

10. Arch Length Prediction fromAlignment of Primary Teeth

11. Good Spacing

12. No Primary Spacing

13. Fair Spacing

14. Leeway Space • Sum of (c-d-e) > (3-4-5) • This allows more space for 3-4-5 • This "leeway space" averages 1.7 mm. in the mandibular buccal segment; 0.9 in the maxillary buccal segment

15. “E” Space

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 occlusion • Bad news - the above reduces arch length

17. Late Mesial Shift (cont.) FTP Molar moves into this space... Class I

18. Late Mesial Shift (cont.)

19. Part 2 Mixed Dentition Analysis • Purpose: predict amount of crowding after permanent teeth come in • Timing: mixed dentition • Materials: Boley gauge • Where: 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, B2 • Predict size of C, B1, B2 • Compare size vs. space for C, B1, B2 to determine amount of crowding

21. Step 1 MDA Methodology • Measure mesial-distal diameter of the mandibular incisors, sum and divide by two

23. Step 1 Example

24. Step 2 MDA Methodology • Select a midline point • Expand the Boley gauge to the amount determined in Step 1 • Mark the point on each primary cuspid from the midline point • This represents the space required for well aligned incisors

25. 11.7 mm 11.7 mm

26. Step 3 MDA Methodology • Measure from the point on each cuspid (derived in Step 2) to the mesial of the first permanent molar • This represents the space available for the permanent cuspid and bicuspids (C, B1, B2)

27. 22.4 mm 22.7 mm

28. Step 3 Example

29. Step 4 MDA Methodology • To the number derived in Step 1, add 10.5 mm for the mandibular teeth • This represents the size of the permanent cuspid and bicuspids in each quadrant • Subtract 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 Methodology • If the space available is less than the amount of tooth mass, a negative number will result • This number is the predicted amount of crowding

31. Step 4 Example

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 for 3-4-5. • Figure 1.7 mm. per side with ETE relationship.

33. MDA Procedure Maxillary Arch • Mentally align the maxillary incisors as was done in the mandibular arch • Measure the space left over for the maxillary C, B1, B2 • Add 11.0 mm. to 1/2 the sum of the MANDIBULAR INCISORS to predict the size of the maxillary C, B1, B2 • Subtract the predicted size from the space available

34. Part 3 Serial Disking • Result without treatment • Description of Ideal Patient • Description of Technique • Steps in Serial Disking

35. What Happens With No Intervention?

36. Cuspid Labial EruptionNo anterior alignment

37. 1st Premolar EruptionDistal cuspid movement?

38. 2nd Premolar EruptionLate mesial shift of 1st molar

39. 2nd Premolar EruptionLate mesial shift of 1st molar Spaces close from posterior!!!

40. Result Without Disking • Same anterior crowding • Blocked out cuspids • Less arch length to work with

41. Ideal Patient for Serial Disking • Class I molars and cuspids (Not FTP) • Normal overbite and overjet • 3 mm or less of anterior crowding

43. Serial Disking Technique • 699, 169 carbide bur or tapered diamond • Anesthetic considerations • local • electronic • none • Prepare mesial surface as stainless steel crown prep • No ledges!…. Feather edge margin

44. Serial Disking Steps:Mandibular Arch • Lateral incisor eruption - disk mesial of primary cuspids • Permanent cuspid eruption - disk mesial of either 1st or 2nd primary molar

45. Mild Anterior CrowdingDisk Primary Cuspids

46. Mild Anterior CrowdingDisk Primary Cuspids