Reducing unwanted movement of teeth during treatment with orthodontic braces, comparing surgically placed implants as stabilisers (anchors) with other conventional methods

Review question

This review, produced by the Cochrane Oral Health Group, seeks to assess the effects of using implants surgically placed in bone in the mouth in order to stabilise (anchor) teeth during treatment with orthodontic braces and compares implants with the use of conventional methods. It also assesses the effects of different surgical anchorage techniques.


Orthodontic treatment is used to correct crooked or sticking out teeth by moving the affected teeth into the correct position. The teeth are straightened by using a brace. Sometimes unwanted movement of other teeth is caused by the use of a brace and this is controlled by what is known as anchorage, or methods for stabilising these teeth. Conventionally anchorage sites are inside the mouth (intraoral) using teeth for example, or alternatively from outside the mouth (extraoral) using headgear devices attached to the head or neck. Sometimes when devices such as headgear are used there are issues with patients being reluctant to wear them, or they have been reported to cause injuries.

As an alternative to these conventional methods, surgical techniques have been developed to put mini-screws or other types of implants into bone in the mouth to provide a firm structure for anchorage (stabilisation) to prevent the unwanted movement of teeth during orthodontic treatments.

These types of devices have become increasingly popular, however their effects have not been fully evaluated.

Study characteristics

The evidence on which this review is based was correct as of 28 October 2013. This is an update to an existing review, which included one study. Fifteen studies were included in this review involving data from 561 participants. The studies were conducted in Europe, India, China, South Korea and the USA. Most took place in university settings or training hospitals and one in a specialist orthodontic practice. Most studies contained a similar number of males and females, however there were more females than males in five studies and only females in two. The age range varied from adolescents and young adults to adults up to the age of 54 years. All participants in the studies needed a course of orthodontic treatment with additional anchorage control. None of the studies reported adverse effects.

Key results

When surgically implanted anchorage devices were compared to conventional anchorage devices, they were better in providing stabilisation for preventing unwanted movement in teeth during orthodontic treatment. There was limited information on patient-reported outcomes such as pain and how acceptable the devices were found to be. No information was reported on adverse events.

Quality of the evidence

The quality of the evidence for the important outcomes in this review ranged from moderate to low quality. The main shortcomings of all of the studies were related to issues with their design and the way they were carried out, with insufficient and low quality reporting of the study methods and outcomes.

Authors' conclusions: 

There is moderate quality evidence that reinforcement of anchorage is more effective with surgical anchorage than conventional anchorage, and that results from mini-screw implants are particularly promising. While surgical anchorage is not associated with the inherent risks and compliance issues related to extraoral headgear, none of the included studies reported on harms of surgical or conventional anchorage.

Read the full abstract...

The term anchorage in orthodontic treatment refers to methods of controlling unwanted tooth movement. This is provided either by anchor sites within the mouth, such as the teeth and the palate, or from outside the mouth (headgear). Recently, new methods of providing anchorage have been developed using orthodontic implants which are surgically inserted into the bone in the mouth. This is termed surgical anchorage. This is an update of a Cochrane review first published in 2007.


To assess the effects of surgical anchorage techniques compared to conventional anchorage in the prevention of unwanted tooth movement in patients undergoing orthodontic treatment by evaluating the mesiodistal movement of upper first molar teeth. A secondary objective was to compare the effects of one type of surgical anchorage with another.

Search strategy: 

We searched the Cochrane Oral Health Group's Trials Register (to 28 October 2013), the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2013, Issue 9), MEDLINE via OVID (1946 to 28 October 2013) and EMBASE via OVID (1980 to 28 October 2013). We handsearched key international orthodontic and dental journals, and searched the trial database and the World Health Organization (WHO) International Clinical Trials Registry Platform for ongoing and unpublished studies.

Selection criteria: 

Randomised controlled trials comparing surgical anchorage with conventional anchorage in orthodontic patients. Trials comparing two types of surgical anchorage were also included.

Data collection and analysis: 

At least two review authors independently and in duplicate extracted data and carried out risk of bias assessments. We contacted study authors to clarify aspects of study design and conduct, and to obtain unreported data.

Main results: 

Fourteen new studies were added in this update resulting in a total of 15 studies reporting data from 561 randomised patients. The studies were conducted in Europe, India, China, South Korea and the USA. The age range of patients was commonly restricted to adolescents or young adults, however the participants of two studies were from a much wider age range (12 to 54 years). The distribution of males and females was similar in eight of the studies, with a predominance of female patients in seven studies.

Eight studies were assessed to be at high overall risk of bias; six studies at unclear risk of bias; one study at low risk of bias.

Ten studies with 407 randomised and 390 analysed patients compared surgical anchorage with conventional anchorage for the primary outcome of mesiodistal movement of upper first molars. We carried out a random-effects model meta-analysis for the seven studies that fully reported this outcome. There was strong evidence of an effect of surgical anchorage on this outcome. Compared with conventional anchorage, surgical anchorage was more effective in the reinforcement of anchorage by 1.68 mm (95% confidence interval (CI) -2.27 mm to -1.09 mm; seven studies, 308 participants analysed) with moderate quality of evidence (one study at high overall risk of bias, five studies at unclear risk of bias, one study at low risk of bias). This result should be interpreted with some caution, however, as there was a substantial degree of heterogeneity for this comparison. There was no evidence of a difference in overall duration of treatment between surgical and conventional anchorage (-0.15 years; 95% CI -0.37 years to 0.07 years; three studies, 111 analysed patients) with low quality of evidence (one study at high overall risk of bias and two studies at unclear risk of bias). Information on patient-reported outcomes such as pain and acceptability was limited and inconclusive.

When direct comparisons were made between two types of surgical anchorage, there was a lack of evidence to suggest that any one technique was better than another.

No included studies reported adverse effects.