Korean J Orthod.  2014 Mar;44(2):88-95. 10.4041/kjod.2014.44.2.88.

Effectiveness of en-masse retraction using midpalatal miniscrews and a modified transpalatal arch: Treatment duration and dentoskeletal changes

• Lee J
• Miyazawa K
• Tabuchi M
• Sato T
• Kawaguchi
• Goto S

• KMID: 2273431
• DOI: http://doi.org/10.4041/kjod.2014.44.2.88

Abstract

OBJECTIVE
The purpose of this study was to compare the treatment duration and dentoskeletal changes between two different anchorage systems used to treat maxillary dentoalveolar protrusion and to examine the effectiveness of en-masse retraction using two miniscrews placed in the midpalatal suture.
METHODS
Fifty-seven patients (9 men, 48 women), who had undergone level anchorage system treatment at Aichi-Gakuin University Dental Hospital (Nagoya, Japan) were divided into two groups according to the method of maxillary posterior anchorage reinforcement: midpalatal miniscrews (25 patients, mean age 22 years) and conventional anchorage (32 patients, mean age 19 years). The en-masse retraction period, overall treatment duration, pre-treatment effective ANB angle, and change in the effective ANB angle were compared with an independent-samples t-test.
RESULTS
Compared to the headgear group, the duration of en-masse retraction was longer by approximately 4 months in the miniscrew group (p < 0.001). However, we found no significant difference in the total treatment duration between the groups. Moreover, a greater change in the effective ANB angle was observed in patients treated with miniscrews than in those treated with the conventional method (p < 0.05).
CONCLUSIONS
The level anchorage system treatment using miniscrews placed in the midpalatal area will allow orthodontists more time to control the anterior teeth during en-masse retraction, without increasing the total treatment duration. Furthermore, it achieves better dentoskeletal control than does the conventional anchorage method, thereby improving the quality of the treatment results.

Keyword

Orthodontic mini-implant; Appliances; Diagnosis and treatment planning; Orthodontic treatment

MeSH Terms

Humans
Male
Sutures
Tooth

Figure

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  Figure 1 The anchorage reinforcing appliances in the headgear group. A, The maxillary first molars were stabilized with a conventional transpalatal arch. B, High-pull headgear.

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  Figure 2 The anchorage reinforcing appliances in the miniscrew group. A, Two miniscrews were placed about 5-8 mm apart in the midpalatal suture area and fixed with a stainless steel ligature wire. B, The maxillary first molars were held with a modified transpalatal arch, and were assisted with skeletal anchorage during en-masse retraction.

• 

  Figure 3 The maxillary en-masse retraction in the headgear group. A, The mandibular arch was stabilized for the use of Class II elastics. B and C, The maxillary first premolar extraction space closure with Class II elastics. D, Post-treatment photograph.

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  Figure 4 The maxillary en-masse retraction in the miniscrew group. A, The mandibular arch was not yet stabilized. B and C, The maxillary first premolar extraction space closure without Class II elastics. D, Posttreatment photograph.

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  Figure 5 The maxillary en-masse retraction. A, Headgear group. Extraction space is closed partially by maxillary molar loss. Class II elastics are used to correct the anteroposterior relationship of the dentition. B, Miniscrew group. The combination of two midpalatal miniscrews and a modified transpalatal arch serve as a skeletal anchorage. This miniscrew anchorage system allows the maxillary anterior teeth to be retracted effectively without undesirable side-effects such as anchorage loss. There is no need to wear Class II elastics to retract the maxillary incisors and to maintain the molar relationship.

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