Mini/micro screw implantation for orthodontic anchorage (interventional procedures consultation)

NATIONAL INSTITUTE FOR HEALTH AND CLINICAL EXCELLENCE

Interventional Procedure Consultation Document

Mini/micro screw implantation for orthodontic anchorage

Patients may require orthodontic treatment to realign teeth. Small screws can be inserted into the jaw bone to create points of anchorage against which a variety of connecting prostheses used to realign teeth can be applied.

The National Institute for Health and Clinical Excellence is examining mini/micro screw implantation for orthodontic anchorage and will publish guidance on its safety and efficacy to the NHS in England, Wales, Scotland and Northern Ireland. The Institute's Interventional Procedures Advisory Committee has considered the available evidence and the views of Specialist Advisers, who are consultants with knowledge of the procedure. The Advisory Committee has made provisional recommendations about mini/micro screw implantation for orthodontic anchorage.

This document summarises the procedure and sets out the provisional recommendations made by the Advisory Committee. It has been prepared for public consultation. The Advisory Committee particularly welcomes:

comments on the preliminary recommendations
the identification of factual inaccuracies
additional relevant evidence.

Note that this document is not the Institute's formal guidance on this procedure. The recommendations are provisional and may change after consultation.

The process that the Institute will follow after the consultation period ends is as follows.

The Advisory Committee will meet again to consider the original evidence and its provisional recommendations in the light of the comments received during consultation.
The Advisory Committee will then prepare draft guidance which will be the basis for the Institute's guidance on the use of the procedure in the NHS in England, Wales, Scotland and Northern Ireland.

For further details, see the Interventional Procedures Programme manual, which is available from the Institute's website (www.nice.org.uk/ipprogrammemanual).

Closing date for comments: 24 July 2007
Target date for publication of guidance: November 2007

Note that this document is not the Institute's guidance on this procedure. The recommendations are provisional and may change after consultation.

1	Provisional recommendations

1.1	There is limited evidence that mini/micro screw implantation provides adequate orthodontic anchorage and there are no major safety concerns. Therefore, clinicians wishing to use this procedure may do so with normal arrangements for clinical governance.
1.2	During the consent process clinicians should ensure that patients understand that there is a failure rate associated with the use of mini/micro screws and that the success of dental alignment cannot be guaranteed. They should provide patients with clear, written information. In addition, use of the Institute's information for patients ('Understanding NICE guidance') is recommended (available from www.nice.org.uk/IPGXXXpublicinfo). [[details to be completed at publication]]
1.3	Evidence about optimal screw size and location of implantation (upper/lower jaw or left/right side of the jaw) is limited. Therefore, further audit and research to clarify these issues would be useful (see section 3.1).

The procedure

2.1

Indications

2.1.1

Some orthodontic procedures require a fixed anchorage point to which a force can be applied in order to move teeth that are malpositioned, misaligned or impacted. The teeth requiring realignment may be located in the upper or lower jaw. Treatment may require force to be applied in any direction, and over a range of time periods.

2.1.2

Several methods can provide anchorage points for orthodontic treatment. The choice of method depends on the required site of anchorage and the direction and degree of its force. Usually, anchorage is achieved using the support of other teeth, but the forces of orthodontic treatment may cause unintended, iatrogenic movement in these teeth. External head gear can be employed to provide anchorage, although this may not be aesthetically acceptable to some patients. Surgically inserted osseointegrated dental implants can also be used to provide anchorage points, although a healing period is required before orthodontic force can be applied.

2.2

Outline of the procedure

2.2.1

Orthodontic mini/micro screw systems can be used when sufficient anchorage cannot be achieved from existing teeth. The screws are small (typically 1-2 mm in diameter and 8-15 mm in length), self-tapping, titanium and consist of a body that connects to the bone, a neck that protrudes through the gum mucosa and a head suitable for connection to orthodontic loading systems. Various dimensions and types of screws are used and there is no universal agreement about how these are classified.

2.2.2

Under local anaesthesia a pilot hole is drilled into the maxilla or mandible and the screw is inserted into the alveolar bone. For some screws a mucoperiostal flap needs to be created in the gum to aid insertion. More than one screw can be inserted if necessary. Orthodontic loading can be achieved immediately after insertion, although it is often undertaken at a subsequent visit.

2.2.3

Following completion of the orthodontic treatment the screw(s) can be extracted (often without anaesthesia) and the incision site(s) is normally expected to heal spontaneously.

2.3

Efficacy

2.3.1

Across four case series of 44, 29, 58, and 87 patients, screw implantation was reported to be successful (usually defined as stable anchorage for 1 year or until completion of orthodontic treatment) in 0-85%, 85%, 81-89%, and 92% (208/227) of screws (absolute figures presented where available). Success rates varied with the type of screw used. The case series of 87 patients fitted with 227 screws reported that there was no statistically significant difference in success rates for four different screw types at 15 months' follow-up (p = 0.154; success rates varied from 80% to 94%). This series reported that the success rate was significantly higher for screws inserted into the maxilla (96%; 119/124) compared with the mandible (86%; 89/103) (p = 0.01). Another case series of 98 patients reported that the overall success rate (defined as anchorage stability with no morbidity) was 84% (118/140).

2.3.2

A further case series of 85 patients fitted with 239 screws reported that the average rate of anchorage loss decreased significantly, from 23% (31/133) in the first patients treated to 5% (5/106) in subsequent patients, once parameters for selection of screw size and location of insertion had been refined (p < 0.001). For more details, refer to the sources of evidence (see appendix).

2.3.3

Two Specialist Advisers considered the procedure to be novel and of uncertain safety and efficacy; one considered it to be an established procedure. They noted that only data from case series are currently available to support the procedure's efficacy, but that two randomised controlled trials are under way in the UK.

2.4

Safety

2.4.1

In seven case series, the rate of screw failure (breakage) ranged from 3% (2/59) to 4% (8/227).

2.4.2

A case series of 85 patients (239 screws inserted) reported that no patients suffered haemorrhage, abscess formation or tooth injury (follow-up period unclear).

2.4.3

Two case series reported that there were no instances of contact with tooth roots during the procedure in 175 screw insertions relating to 87 patients.

2.4.4

In one case series, half of the 40 patients fitted with one type of screw did not require pain medication at any time after surgery. For more details, refer to the sources of evidence (see appendix).

2.4.5

The Specialist Advisers considered adverse events to be discomfort on screw placement and screw failure or loosening. Other theoretical complications were pain, infection, nerve damage and damage to adjacent teeth.

3	*Further information*
3.1	This guidance requires that clinicians undertaking the procedure make special arrangements for audit. The Institute has identified relevant audit criteria and is developing an audit tool (which is for use at local discretion), which will be available when the guidance is published.

Bruce Campbell
Chairman, Interventional Procedures Advisory Committee
June 2007

Appendix:

Sources of evidence

The following document, which summarises the evidence, was considered by the Interventional Procedures Advisory Committee when making its provisional recommendations.

'Interventional procedure overview of mini/micro screw implantation for orthodontic anchorage', March 2007

Available from: www.nice.org.uk/ip389overview.

This page was last updated: 30 March 2010