Am J Orthod Dentofacial Orthop 2007;132:722-30889-5406/$32.00Copyright © 2007 by the American Association of Orthodontists.doi:10.1016/j.ajodo.2007.10.022

REFERENCES

1. Chung KR, Kim YS, Linton JL, Lee YJ. The miniplate with tubefor skeletal anchorage. J Clin Orthod 2002;36:407-12.

2. Chung KR, Cho JH, Kim SH, Kook YA, Cozzani M. Unusualextraction treatment in Class II Division 1 malocclusion. AngleOrthod 2007;77:155-66.

3. Chung KR, Kim SH, Mo SS, Kook YA, Kang SG. Severe ClassII Division 1 malocclusion treated by orthodontic miniplate withtube. Prog Orthod 2005;6:172-86.

4. Chung KR, Kim SH, Kook YA. C-orthodontic mini-implant. In:Cope JB, editor. OrthoTADs book: clinical guideline and atlas.Dallas, Tex: Texas Under Dog Media; 2007. p. 248.

5. Kim SH, Hwang YS, Ferreira A, Chung KR. Analysis of tempo-rary anchorage devices used for en masse retraction: a preliminarystudy. Am J Orthod Dentofacial Orthop 2007 (in press).

En-masse retractionWe compliment Chung et al for successfully treating

bidentoalveolar protrusion by en-masse retraction of 6 max-illary anterior teeth with microimplants (C-implants) (ChungKR, Nelson G, Kim SH, Kook YA. Severe bidentoalveolarprotrusion treated with orthodontic microimplant-dependenten-mass retraction. Am J Orthod Dentofacial Orthop 2007;132:105-15). Because posterior attachments are minimizedwith this technique, it favors orthodontic treatment planningfor adults, particularly those with periodontal problems.

Microimplants definitely enhance the anchorage poten-tial, as depicted in this report and elsewhere.1 In the article byChung, however, certain areas need to be further analyzedand clarified. The authors stated that they sandblasted andacid-etched the implants (except the upper 2 mm) for optimalosseointegration. However, they did not mention how longthe implants were left in the mouth before loading. Theoret-ically, 2 to 3 months are required for osseointegration to takeplace between the titanium surface and the bone tissue.2

Waiting for 8 to 12 weeks would lengthen the treatment timeby that much. Clinically, there is no difference in the failurerates between immediate loading and delayed loading, if wekeep the applied force less than 300 g.2

In fact, the magnitude of force applied by the authors was4.5 oz, which is approximately 135 g. In our opinion, waitingfor osseointegration in such a situation is perhaps unneces-sary. Also, for stability of the mini-implant, light continuousforces as generated by the nickel-titanium coil springs arepreferred over elastomerics, which often generate an exces-sive initial force.2 Even for efficient tooth movement, similarlight continuous forces are recommended; these are notpossible with elastomerics because they become permanentlydeformed after absorbing water and saliva when exposed tothe oral environment for extended periods. This actuallyresults in loss of force because of stress relaxation of theelastomerics.3

Furthermore, the authors used .016 � .022-in stainlesssteel wire for en-masse retraction in a .022-in slot; this wouldlead to uncontrolled tipping. This is evident in their casebecause bodily retraction was not achieved, and it took 8months to achieve space closure. Later in the treatment, theyused .017 � .025-in stainless steel wire with gable bends tocontrol torque and finish retraction. It is intriguing how theywere able to achieve torque expression with an undersizedwire (.017 � .025-in wire in a .022-in slot), which would bea critical factor in completion of the case. Also, for torquecontrol, 2-point contact is required in the posterior segment(buccal tube); this was missing in this case, since the authorspassed the wire through the implant hole.

Thus, their results, although interesting, leave severalgaps in our understanding of the mechanics involved inachieving the desired effect.

Priyanka Sethi,Ruchi Saxena,

and Kanhoba Mahableshwar KeluskarBelgaum, Karnataka, India

Am J Orthod Dentofacial Orthop 2007;132:7230889-5406/$32.00Copyright © 2007 by the American Association of Orthodontists.doi:10.1016/j.ajodo.2007.10.008

REFERENCES

1. Cope JB. Temporary anchorage devices in orthodontics: a para-digm shift. Semin Orthod 2005;11:3-9.

2. Kyung HM, Park HS, Bae SM. Handbook for the Absoanchororthodontic microimplant. 3rd ed. 2004. Taegu, Korea: p. 20–1.Available at: www.dentos.co.kr/data/new_handbook_3rd_040603.pdf.

3. Baty LD, Storie JD, Fraunhofer AJ. Synthetic elastromeric chains.A literature review. Am J Orthod Dentofacial Orthop1994;105:536-42.

Authors’ responseWe thank Dr Priyanka Sethi et al for their interest in our

case report.In treating this patient, we placed 4 C-implants (1.8 mm

in diameter and 8.5 mm in length) bilaterally in the buccalsegments for orthodontic anchorage. They were loaded aftera 4-week healing period. A recent article about wound healingaround prosthetic implants suggested that the critical periodof greatest risk for implant failure in osseointegration wasafter the placement of an endosseous implant1 and suggestedthat a minimum healing period of 4 weeks was needed.Treatment time is not extended by the healing period, becauseit allows time for extraction, restorative treatment, periodon-tal treatment, and bonding or banding procedures.2,3

The osseointegration potential of the surface-treatedmini-implant offers the advantage of stability and resistanceto dynamic forces and moments during en-masse retrac-tion.4,5

As Dr Sethi et al commented, any traction materials canbe used for anterior retraction. A nickel-titanium closed-coilspring is especially efficient for constant retraction. Never-

American Journal of Orthodontics and Dentofacial OrthopedicsVolume 132, Number 6

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