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Microimplant characterisation
Microimplant characterisation
Microimplant characterisation
Microimplant characterisation
Microimplant characterisation
Microimplant characterisation
Microimplant characterisation
Microimplant characterisation
Microimplant characterisation
Microimplant characterisation
Microimplant characterisation
Microimplant characterisation
Microimplant characterisation
Microimplant characterisation
Microimplant characterisation
Microimplant characterisation
Microimplant characterisation
Microimplant characterisation
Microimplant characterisation
Microimplant characterisation
Microimplant characterisation
Microimplant characterisation
Microimplant characterisation
Microimplant characterisation
Microimplant characterisation
Microimplant characterisation
Microimplant characterisation
Microimplant characterisation
Microimplant characterisation
Microimplant characterisation
Microimplant characterisation
Microimplant characterisation
Microimplant characterisation
Microimplant characterisation
Microimplant characterisation
Microimplant characterisation
Microimplant characterisation
Microimplant characterisation
Microimplant characterisation
Microimplant characterisation
Microimplant characterisation
Microimplant characterisation
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Microimplant characterisation

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A study to elucidate the pull out characteristics of microimplants .

A study to elucidate the pull out characteristics of microimplants .

Published in: Health & Medicine
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    • 1. Computed Tomographic Characterization ofMini-Implant Insertion Pattern and Maximum Anchorage Force in Human Cadavers Dr Jean-Marc Retrouvey Genevieve Lemieux
    • 2. • For more complete information, please read the article on the same topic in the AJO-DO
    • 3. History Anchorage Devices Osseointegrated Non Osteointegrated Implants Implants Mechanical Retention Palatal Onplant Dental Implant Surgical Fixation Screws Retromolar Implant Fixation Screws / Mini Implants plates Kanomi, 1997 (Sugawara)Wehrbein, H. and Merz, B.R. 1998 Roberts, W.E. et als, 1990 Cope, J.B., Seminar Orthodontics 2005
    • 4. Facts on Mini-Implants1. Mini-implants are the most widely used temporary orthodontic anchorage devices.2. Principal indications: Melsen, B., Journal of Clinical Orthodontics, 2005 Insufficient teeth for the application of conventional anchorage Cases where forces on the reactive unit would generate adverse side effects Need for asymmetrical tooth movements in all planes of spaces As an alternative to orthognathic surgery
    • 5. 3.1. Length: Varies approximately between 6 to 16 mm The length chosen will depend on the bone characteristics in the insertion location Jiang, L et al (2009): “The longest length in the safety range is recommended” Jiang, L et al, Advances in Engineering Software, 2009
    • 6. 3.2. Diameter: Varies between 1 to 2 mm Smaller diameter 1.4 mm to 1.6 mm is preferred •pros: fewer anatomical risks, hence more sites available for ease of insertion between roots •cons: potential for neck fracture upon retrieval for smaller diameters For intrusion, Park (AJO, 2003) advocated 2mm implants Park et al. (AJO 2006) reported that the smaller implants were actually more successful than the bigger ones Melsen, B., Journal of Clinical Orthodontics, 2005
    • 7. 3.2. Diameter:Anatomical limitations- Interradicular distance maynot allow the use of 2mm mini-implants .- Poggio, P.M. et al studiedinterradicular width » Several areas do not have enough space for large 2mm screws…. Poggio, P.M. et al, Angle Orthodontist, 2006
    • 8. 4. Failure rate Schätzle et al, 2009, Systematic Review. •Compared 17 studies accessing mini-implant failure rates •Estimated an average failure rate of 16.4% by meta-analysis Schätzle et al, Clinical Oral Implants Research, 2009
    • 9. 5. Factors affecting stability- One important factor is immediate loading Immediate loading is suggested and may improve screw stability •Huja AJO 2005 Pull out forces are much higher than orthodontic forces •Salmoria, AJO 2008. Jacobson, AJO 2006 There does not seem to be a benefit in waiting for loading mini implants
    • 10. 6. Anatomical damage Posterior area of the maxilla and mandible are most suitable sites for micro implants insertion •Hyo-Sun Park KJO 2002 Interradicular distance has to be carefully monitored before placement •Poggio, Angle 2008 Angulating the implants is recommended by Park et al to lower root damage •Park AJO 2006
    • 11. Purpose of this investigation• Despite the rapidly growing use of mini- implants – There is a lack of comprehensive and well controlled studies examining all the potential factors affecting initial stability simultaneously – Few studies have examined primary stability in human bone
    • 12. Goals of this investigation •to characterize the insertion1 pattern of mini-implants using CT imaging •to determine and quantify the factors affecting mini-implant 2 primary stability
    • 13. Materials & MethodsA) Cadavers - 5 unembalmed human cadavers - Average age: 87 years old (SD of ± 5 years); 2 male, 3 femaleB) Mini-implants placement - 3M Imtec mini-implants used - total of 12 mini-implants inserted per cadaver - location of insertion: - maxillary & mandibular buccal alveolar bone
    • 14. Materials & Methods 3M Imtec 1.8 mm diameter mini-implant (schematic representation)
    • 15. Materials & Methods B) Mini-implants placementLocation of insertion into alveolar bone on facial surface of maxilla and mandible
    • 16. Materials & MethodsB) Mini-implants placement Distribution of 60 mini-implants across 5 cadavers
    • 17. Materials & MethodsC) Imaging – High-resolution CT imaging (0.625mm slices) – Imaging done before and after mini-implants placement to assess bone characteristics at the site of insertion
    • 18. Materials & MethodsC) Imaging - Data measured: Bone Bone type Density thickness surrounding the tip and parallel sections of each mini-implants
    • 19. Materials & MethodsC) Imaging - assessment of position and bone characteristicsExample of measurements of bone thickness and density at site of insertion
    • 20. Materials & MethodsC) Imaging - assessment of anatomical damage a) b) c) Mini-implant insertion into: (a) adjacent root structure (b) lingual cortical bone (c) maxillary sinus
    • 21. Materials & MethodsD) Tensile strength apparatus Slowly increasing tensile force applied to each mini- implant until point of failure (10N/s) •Point of failure: force at which the mini-implant pulled out of the bone Direction of the force applied •Parallel to the occlusal plane
    • 22. Materials & MethodsD) Tensile strength apparatus
    • 23. ResultsPart A) Analysis of the insertion pattern Location of mini-implants as it relates to bone architecture Assessment of damage to neighboring structure
    • 24. ResultsPart B) Maximum anchorage force (MAF) Determination of: •Initial maximum anchorage force •Relation to implant length, insertion depth, bone density
    • 25. Results Part A) Analysis of the insertion patternCT analysis of mini-implantinsertion into:- soft tissue (A)- buccal cortical bone (B)- cancellous bone (C)- lingual cortical bone (D)
    • 26. ResultsPart A) Analysis of the insertion patternThe degree of implantpenetration strongly dependson implant length1. 15% of 6mm mini-implants failed to anchor their parallel sections into cortical bone2. 95% of 10mm mini-implant parallel sections penetrated beyond the buccal cortical bone3. All 20 tips of 6mm mini- implants reached cancellous bone4. 75% of 10mm penetrated both corticals reaching the lingual cortical bone
    • 27. Part A) Analysis of the insertion pattern- Assessment of damage to neighboring structure 6 mm 8 mm 10 mm Implant Implant Implant (n = 20) (n = 20) (n = 20)Average distance to adjacent root structure 528 um 441 um 414 umIncidence of penetration into root structure 5 (25%) 6 (30%) 3 (15%) Incidence of bicortical insertion 0 (0%) 6 (30%) 15 (75%) Incidence of sinus perforation 0 (0%) 2 (10%) 3 (15%) Liou, AJO, 2004: 2mm minimum distance to prevent root damage
    • 28. ResultsPart B) Maximum anchorage force (MAF) MAF is defined as: •Static tensile force at which each mini-implant failed Confounding factors: • 7 mini-implant heads were damaged or broken • 13 cord slippage encountered • Therefore, 40 mini-implants were used in the statistical model
    • 29. Part B) Maximum anchorage force (MAF)-Median forces:128 N – 6mm160 N – 8mm211 N – 10mm-Significant differencebetween:MAF of 6mm and 10 mm mini-implants(p<0.05)
    • 30. Results Part B) Maximum anchorage force (MAF) Correlation between maximum anchorage force and various combinations of: - insertion depth (ID) - bone density (ρ) - implant length (L) Parallel Tapered Correlation (0-1) P-Value Section Section Limplant x x 0.45 0.004 ρcortical n/a n/a 0.42 0.007 ρcancellous n/a n/a 0.36 0.02 IDcortical x 0.26 0.11 IDcancellous x 0.24 0.13IDcortical + IDcancellous x 0.27 0.08 IDcortical x x 0.23 0.16 IDcancellous x x 0.21 0.18
    • 31. Results Part B) Maximum anchorage force (MAF) Correlation between maximum anchorage force and various combinations of: - insertion depth (ID) - bone density (ρ) - implant length (L) Parallel Parallel Tapered Tapered Correlation (0-1) Correlation (0-1) P-Value P-Value Section Section Section Section IDcortical + IDcancellous x x 0.29 0.06 Limplant x x 0.45 0.004 (IDcortical • ρcortical) x 0.49 0.002 ρcortical n/a n/a 0.42 0.007 (IDcancellous • ρcancellous n/a x n/a 0.36 0.38 0.02 0.02 ρcancellous) ID x 0.26 0.11 (IDcortical •cortical ) + ρcortical IDcancellous x x 0.55 0.24 <0.001 0.13(IDcancellous • ρcancellous) (IDcortical+• IDcancellous IDcortical ρcortical) x x x 0.27 0.41 0.08 0.008 ID • ρ(IDcancellous cortical x x 0.23 0.16 cancellous) x x 0.44 0.004 ID • ρ (IDcortical cancellous ) + x x 0.21 0.18 cortical x x 0.65 <0.001(IDcancellous • ρcancellous)
    • 32. DiscussionLonger implants for more stability? Pros Cons
    • 33. DiscussionRoot Damage• In this study, the average distance of the mini- implants, regardless of their length, was less that 1 mm away from root structure• Liou et al recommend of at least 2mm between the roots and the surface of the implant Liou EJW et al, AJODO, 2004
    • 34. Discussion• Maximum Anchorage Force- Factors studied Knowledge of the bone quality (density and thickness) provides a stronger prediction for maximum anchorage force than implant length Clinically, the knowledge of bone thickness and density may provide the strongest predictor of initial implant stability for any given site.
    • 35. Discussion • Intra-Inter cadaver variabilityConsiderablevariation wasfound withinandbetweencadavers•Example: averagecortical bone density ofthe 5 maxillas is 1084HU . SD= 213 HU and232 HU
    • 36. Limitations of the study– Recently unembalmed human cadavers were used (realistic model) Use of cadavers involves some important restrictions when compared to the placement of mini-implants in living bone: • There is no bone remodeling • The age of available cadavers is usually advanced (average age in this study was 87 years) where bone composition and other anatomical changes may be important.
    • 37. Conclusions1) Shorter mini-implants (6 mm) tended to have incomplete penetration of the buccal cortical bone.2) Longer mini-implants tended to penetrate further into the bone (offering more mechanical anchorage) but were also associated with a greater incidence of sinus and bicortical perforations.
    • 38. Conclusions3) The most important factors determining maximum mechanical anchorage were found to be (in decreasing order): bone density and insertion depth combined, mini-implant length, bone density, insertion depth.
    • 39. Conclusions4) Mechanical resistance to pull out force is much higher than applied orthodontic force5) Failure rate of mini-implants may not be related to initial loading.6) Large variability in bone density and quantity between the sites
    • 40. Conclusions4) Mechanical resistance to pull out force is much higher than applied orthodontic force5) Failure rate of mini-implants may not be related to initial loading.6) Large variability in bone density and quantity between the sites (intra and inter cadaver variability)
    • 41. Future Work• Use of different brands of micro implants• Dynamic pull out system to measure potential bone fatigue – Forces from mastication may be more important than we currently think (large and intermittent)• Animal studies to study inflammation in relation to pull out force
    • 42. AcknowledgementMcGill University• Dr C. Cheretakis• Adam Hart• Professor Marc MckeeEastern Virginia Medical School• Dr C. Goodmurphy• Stephanie Trexler• Christopher McGary

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