Comparison of rate of canine retraction with conventional molar ...

ORIGINAL ARTICLE 

Comparison of rate of canine retraction with 

conventional molar anchorage and titanium 

implant anchorage 

Badri Thiruvenkatachari, a Pavithranand Ammayappan, b and Rajasigamani Kandaswamy c 

Manchester, United Kingdom, and Tamil Nadu, India 

Introduction: Various anchorage techniques have been designed for canine retraction. Intraoral techniques 

have not always been successful, and now implants are widely used for this purpose. A new type of titanium 

microimplant, with a small diameter and a button-like head, was shown to be an effective source of 

anchorage for distal movement of the canines. The purposes of this study were to measure and compare the 

rates of canine retraction with titanium microimplant anchorage and conventional molar anchorage. 

Methods: The sample comprised 12 patients (8 female, 4 male; mean age, 19.7 years; range, 16-22 years) 

who were scheduled for extraction of all first premolars. After leveling and aligning, titanium microimplants 

1.2 mm in diameter and 9 mm in length were placed between the roots of the second premolar and the first 

molars. The implants were placed in the maxillary and mandibular arches on the same side in 10 patients and 

in the maxilla only in 2 patients. A brass wire guide and a periapical radiograph were used to determine the 

implant position. After 15 days, the implants and the molars were loaded with closed coil springs with a force 

of 100 g for canine retraction. Preretraction and postretraction lateral cephalograms were taken and 

superimposed for measuring the amount of retraction. The amount of canine retraction was measured from 

pterygoid vertical in the maxilla and SN perpendicular in the mandible. Results: Mean canine retraction 

amounts were 4.29 mm in the maxilla and 4.10 mm in the mandible on the implant-anchorage side, and 3.79 

mm in the maxilla and 3.75 mm in the mandible on the molar-anchorage side. The rates of canine retraction 

were 0.93 mm per month in the maxilla and 0.83 mm per month in the mandible on the implant-anchored 

side, and 0.81 mm per month in the maxilla and 0.76 mm per month in the mandible on the molar-anchored 

side. Conclusions: Canine retraction proceeds at a faster rate when titanium microimplants are used for 

anchorage. (Am J Orthod Dentofacial Orthop 2008;134:30-5) 

Anchorage in orthodontics is the most important 

factor that determines the treatment and result. 

Salzmann 1 stated that “regardless of the skill 

one may possess in the mechanics of space closure 

following the extraction of the teeth, the teeth in the 

posterior buccal segment will be displaced mesially to 

some extent.” To use the entire extraction space for 

retraction of the canines, various anchorage techniques 

have been designed. Intraoral anchorage techniques 

have not always been successful. Although headgear 

has proved to be the best source of anchorage, the 

a Clinical researcher, Department of Orthodontics, School of Dentistry, University 

of Manchester, Manchester, United Kingdom. 

b Lecturer, Department of Orthodontics, Rajah Muthiah Dental College and 

Hospital, Annamalai University, Tamil Nadu, India. 

c Professor and head, Department of Orthodontics, Rajah Muthiah Dental 

College and Hospital, Annamalai University, Tamil Nadu, India. 

Reprint requests to: Badri Thiruvenkatachari, Orthodontic Research Unit, 3rd 

Floor, Coupland 3 Building, School of Dentistry, University of Manchester, 

Higher Cambridge St, Manchester M15 6FH, United Kingdom; e-mail, 

Badri_chari@yahoo.com. 

Submitted, February 2006; revised and accepted, May 2006. 

0889-5406/$34.00 

Copyright © 2008 by the American Association of Orthodontists. 

doi:10.1016/j.ajodo.2006.05.044 

30 

problems related to patient compliance, 2 undesirable 

side effects on the maxillary complex, and the risk of 

injuries 3-5 have jeopardized success. Because any dental 

anchorage would to a certain degree result in unwanted 

movement of the anchor teeth, devices have been developed 

that do not use teeth as the anchorage unit. 

After the introduction of the implant, its use as a 

source of orthodontic anchorage was widely reported in 

orthodontic literature. Specifically designed orthodontic 

implants have been placed in various locations such as the 

alveolar bone, 6 the retromolar region, 7 the midpalatal 

region, 8 and the lingual 9 and buccal 10 cortical plates. 

A new type of titanium microimplant—an alternative 

to molar anchorage—was developed. The smaller 

diameter of the implant, which was specifically designed 

for orthodontic use, has a button-like head with 

a hole that accepts ligatures and elastomers. A study of 

these implants proved that they are effective anchorage 

for distal movement of the canines. 11 The study proved 

that they can minimize the molar anchorage loss by 1.6 

mm in the maxilla and 1.7 mm in the mandible when 

used as anchorage for the retraction of the canines.

American Journal of Orthodontics and Dentofacial Orthopedics 

Volume 134, Number 1 

Fig 1. Implants in position: A, implant anchorage; B, molar anchorage. 

The purposes of this study were to measure the 

amount of canine retraction and to compare and measure 

the rates of canine retraction with implant anchorage 

and conventional molar anchorage. 

MATERIAL AND METHODS 

In this study, we chose subjects from the patients at 

the Department of Orthodontics, Annamalai University, in 

Tamil Nadu, India, for orthodontic treatment. Twelve 

patients were selected (mean age, 19.7 years; range, 16-22 

years; 8 female, 4 male). This study was reviewed and 

approved by the Institutional Review Board. 

The patients were chosen according to the following 

criteria: (1) comprehensive medical and dental history 

ruling out systemic illness, (2) therapeutic extraction of 

the first premolars required, (3) leveling and aligning 

completed, and (4) maximum anchorage needed, with 

75% to100% of space closure used for retraction of the 

anterior segment. 12 All subjects had an arch length-basal 

bone discrepancy of more than 5 mm. Patients with Angle 

Class I malocclusion and an ANB angle between 2° and 

4° were selected for implant placement in both the maxilla 

and the mandible; for patients with Angle Class II malocclusion 

and an ANB angle above 5°, implant placement 

was restricted to the maxilla, as a part of camouflage 

treatment. No anchorage preservation methods were used 

until the end of the study for any patient. 

After initial leveling and aligning, a 0.016 0.022-in 

stainless steel archwire was placed. Informed consent was 

obtained for all patients before placement of the implants. 

Routine blood studies ruled out any blood 

dyscrasias. The titanium microimplants of 1.2 mm in 

diameter and 9 mm in length were positioned at the 

maximum thickness of interdental bone between the roots 

of the second premolar and the first molar on the selected 

quadrant 13 (Fig 1). Orthodontic forces were applied 15 

days after implant placement. Nickel-titanium closed-coil 

springs with a force of 100 g (measured with the Dontix 

gauge; American Orthodontics, Sheboygan, Wis) were 

stretched between the implant and the canine on the 

Thiruvenkatachari, Ammayappan, and Kandaswamy 31 

Fig 2. Schematic diagram showing the L-shaped wire 

in the buccal tube for differentiating the molars on 

lateral cephalograms. 

implant-anchored side and between the molar and the 

canine on the molar-anchored side. The period of the 

study was 4 to 6 months. 

Two sets of records were taken; the first was before 

implant placement, and other when canine retraction 

was complete in accordance with the patient’s treatment 

plan. These included study models, cephalometric 

radiographs, orthopantomograms, and photographs. 

To differentiate the right and left sides on the lateral 

cephalogram, a 0.0175 0.025-in stainless steel wire 

in an L-shape with 0.5 cm of vertical length and 1 cm 

of horizontal length was placed in the buccal tube of 

molars 11 (Fig 2). The right and left canines were 

identified by tracing them along the archwire from the

32 Thiruvenkatachari, Ammayappan, and Kandaswamy 

respective molars to the archwire-bracket junction in 

the canine bracket. 

The amount of canine retraction was measured by 

using a stable landmark in the cranium as a reference. 

In the maxilla, the preretraction and postretraction 

lateral cephalometric tracings were superimposed by 

McNamara’s method. 14 The horizontal distance from 

the pterygoid vertical to the tip of the canine hook on 

both sides was calculated. 14 

In the mandible, the cephalograms were superimposed 

according to Bjork’s method. 15 The horizontal 

distance was calculated from sella vertical to the tip of 

the canine hook on both sides. 16 

The rate of canine retraction was calculated by 

dividing the amount of canine retraction by time taken 

for retraction. 

The data obtained were subjected to statistical analysis. 

Means, standard errors, and standard deviations were 

tabulated, with the Student t test used to determine the 

level of significance and correlation of the rate of canine 

retraction between implant anchorage and conventional 

molar anchorage in the maxilla and the mandible. 

RESULTS 

The canines were successfully retracted in all subjects 

(Figs 3-6). Canine retraction was considered 


July 2008 

Fig 3. Canine retraction using closed-coil springs on implant anchored side: A, before retraction; 

B, after retraction. 

Fig 4. Canine retraction using closed-coil springs on molar anchored side: A, before retraction; 

B, after retraction. 

complete when the extraction space was closed on the 

molar-anchored side. The duration of the study was 4 to 

6 months (Tables I and II). 

The amounts of distal movement of canines with 

implants as anchorage were 4.29 mm in the maxilla and 

4.10 mm in the mandible (Table III). The distal 

movements of the canines with conventional molar 

anchorage were 3.79 mm in the maxilla and 3.75 mm in 

mandible (Table III). The average differences were 0.6 

mm in the maxilla and 0.35 mm in the mandible. These 

values were statistically significant (P 0.01). 

The rates of canine retraction were 0.93 mm per 

month in the maxilla and 0.83 mm per month in the 

mandible on the implant-anchored side, and 0.81 mm 

per month in the maxilla and 0.76 mm per month in the 

mandible on the molar-anchored side (Table IV). The 

mean differences in the rate of canine retraction were 

0.12 mm per month in the maxilla and 0.07 mm per 

month in the mandible. These values were statistically 

significant (P 0.01). 

DISCUSSION 

Canine retraction is a common treatment procedure 

in orthodontics. Various appliances are used for retraction 

of the canines to close extraction spaces. The 

retraction of canines depends on various factors: the



Fig 5. Lateral cephalometric tracing before canine 

retraction. 

appliance used, the force applied, the technique used, 

and the periodontal ligament area. 

Although various studies deal with the relationship 

between optimum force magnitude and rate of canine 

retraction, few human studies have been reported. The 

first such study for comparing this relationship was by 

Story and Smith, 17 who reported an optimum force of 

150 to 200 g for retraction of the mandibular canines. 

Iwasaki et al 18 reported that forces as low as 18 g could 

cause effective tooth movement and recommended that 

optimum pressure should be less than 100 g. Ricketts 19 

advocated 75 g, and Lee 20 recommended 150 to 200 g 

as the optimum pressure value for canine retraction. 

Boester and Johnston 21 reported 140 to 300 g, and 

Paulsen et al 22 used 50 to 75 g for canine retraction. 

Huffman and Way 23 advocated 200 g as the optimum 

force. Hixon et al 24 reported that higher forces produce 

more effective tooth movement. In an experimental study 

on mini-implants, Buchter et al 25 showed that immediate 

loading of implants with a force of 100 cN had a high 

success rate. It is generally thought that light forces are 

more biologic and less painful. Because reports have 

shown effective tooth movement with light forces, a force 

of 100 g was applied with nickel-titanium closed-coil 

springs in this study for retraction of the canines into the 

premolar extraction spaces. 18,19,22 

Studies have dealt with canine retraction with 

various techniques and appliances. The reported rates 

of canine retraction have varied from 0.35 to 1.55 mm 

per month. Paulsen et al 22 showed an average canine 


Fig 6. Lateral cephalometric tracing after canine 

retraction. 

retraction rate of 1 mm per month. That value is 

comparable with our study. In the study of Sonis et al, 26 

the rates of canine retraction were 0.99 to 1.51 mm in 

3 weeks. The differences in their retraction rates and 

ours were probably due to the high force levels used in 

their study. In a randomized clinical trial by Dixon 

et al, 27 the mean rate of canine retraction with nickeltitanium 

coil springs was 0.81 mm per month. Darendelier 

et al 28 compared pull coil springs and drum 

springs in adults and reported an average rate of canine 

retraction of 0.87 mm per month with pull coil springs. 

Those results were similar to ours. Boester and 

Johnston 21 showed canine retraction rates of 3.24 and 

2.05 mm in 2 months in the maxilla and the mandible, 

respectively. Their results were higher than in our study 

and can be attributed to the difference in force levels 

used. Sleichter 29 showed a canine retraction rate of 

1 mm per month; this is close to the value we obtained. 

Hixon et al 24 obtained a rate of canine retraction of 0.17 

mm per week for a force of 100 g, a similar result to 

this study. 

Not many human studies report the rate of canine 

retraction, and no study reports the rate of canine 

retraction against a stable anchorage unit. In this study, 

the movement of the canine against the stable anchorage 

unit, the titanium microimplant, was analyzed. 

Canines were retracted faster with implant anchors, and 

the differences in average amount of canine retraction 

were 0.6 mm in the maxilla and 0.35 mm in the 

mandible. The difference in the rates of retraction

34 Thiruvenkatachari, Ammayappan, and Kandaswamy 

Table I. Amount, rate, and period of canine retraction in the maxilla 

Subject Age/sex 

Amount of canine retraction 

(mm) 

Rate of canine retraction 

(mm/mo) 

Implant side Molar side Period of study (mo) Implant side Molar side 

1 21/F 4.5 4.0 5 0.9 0.8 

2 18/M 3.5 3.5 4 0.875 0.875 

3 18/F 4.5 3.5 5 0.9 0.7 

4 21/F 4 3.5 5 0.8 0.7 

5 19/F 4.5 4.5 4.5 1 1 

6 20/M 5 4 4.5 1.11 0.88 

7 21/F 4 3.5 5 0.9 0.7 

8 21/F 5 4.5 4 1.25 1.125 

9 20/F 4 4 4.5 0.88 0.88 

10 19/M 4.5 4 5.5 0.81 0.727 

11 21/F 4 3.5 5 0.8 0.7 

12 19/M 4 3 4.5 0.88 0.66 

F, Female; M, male. 

Table II. Amount, rate, and period of canine retraction in the mandible 

Subject Age/sex 

Amount of canine retraction 

(mm) 

Rate of canine retraction 

(mm/mo) 

Implant side Molar side Period of study (mo) Implant side Molar side 

1 21/F 4 4 5 0.8 0.8 

2 18/M 3.5 3.5 4 0.875 0.875 

3 18/F 4.5 4 5 0.9 0.8 

4 21/F 4 3.5 6 0.666 0.58 

5 19/F 4.5 4 4.5 1 0.88 

6 20/M 4.5 4 5 0.9 0.8 

7 21/F 3.5 3.5 5 0.636 0.636 

8 21/F 4.5 4 5.5 0.818 0.727 

9 21/F 4 3.5 5 0.8 0.7 

10 19/M 4 3.5 4.5 0.88 0.77 

F, Female; M, male. 

Table III. Comparison of amounts of canine retraction between sides in the maxilla and the mandible 

Implant-anchored side Molar-anchored side 

Mean (mm) SD Mean (mm) SD 

Canine retraction, maxilla (n 12) 4.2917 0.45017 3.7917 0.45017 * 

Canine retraction, mandible (n 10) 4.1000 0.39441 3.7500 0.26352 * 

*P 0.01. 

Table IV. Comparison of rates of canine retraction between sides in the maxilla and the mandible 

Implant-anchored side Molar-anchored side 

Mean (mm/mo) SD Mean (mm/mo) SD 

Canine retraction, maxilla (n 12) 0.9254 0.13429 0.8128 0.14314 * 

Canine retraction, mandible (n 10) 0.8275 0.11037 0.7568 0.09712 * 

*P 0.01. 


July 2008 

P 

P



between the molar and the implant anchorage might be 

because of the anchorage loss on the molar-anchorage 

side, and thus forces are reduced as the canines are 

retracted. The results prove that implants are efficient 

anchors and produce faster canine retraction. 

At the end of the study, the asymmetric molaranchorage 

loss was managed by allowing mesial movement 

of the molars on the implant-anchored side. 

The main reason for this study was to validate the 

rate of canine retraction with titanium implant anchors. 

This method evolved from the desire to achieve the best 

result for an important and necessary stage for many 

orthodontic patients, with minimal undesirable tooth 

changes. Implants produce effective canine retraction 

by using the entire extraction space. 13 With increasing 

demands on orthodontists to treat more patients in 

shorter times, attention to quality of treatment is essential. 

Titanium microimplants can bring about more 

effective canine retraction in a shorter time. 

CONCLUSIONS 

Implant anchorage produced more canine retraction 

than conventional molar anchorage. The rate of canine 

retraction was faster with implant anchorage than with 

molar anchorage. The use of implants as anchorage for 

the retraction of canines is a viable alternative to 

conventional molar anchorage. 

We thank Prof Kevin O’Brien for his valuable 

insights in preparing this manuscript and Dr Hee Moon 

Kyung for providing the implants. 

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