Orthodontic Retainers and Removable Appliances
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Orthodontic Retainers and Removable Appliances

Principles of Design and Use

Friedy Luther, Zararna Nelson-Moon

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eBook - ePub

Orthodontic Retainers and Removable Appliances

Principles of Design and Use

Friedy Luther, Zararna Nelson-Moon

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This book is a practical guide for both dental students and practitioners to designing, fitting and adjusting removable orthodontic appliances and retainers. The book offers step by step instructions with clear illustrations on the key areas of clinical practice. In each case, information is provided on indications for use, principles of design, fitting, activation and trouble shooting. Further chapters coach students to deal effectively with their patients and to manage the treatment plan in question.

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Assumptions: What You Should Know and Understand Before You Use this Book
As a reader of this book, it is only fair that you know what you are getting as the remit is certainly not to teach orthodontics! It concentrates on discussing the practical aspects of only two, relatively discreet, but important aspects of orthodontics:
  • Interceptive treatment deals with the developing, childhood dentition at a time when decisions can strongly influence long-term outcomes. Identifying and explaining the principles of interception are among the learning outcomes identified by the General Dental Council.
  • Retention is an increasingly important part of orthodontic treatment for many patients. More and more, patients may wish to maintain (for as long as feasible) their treatment result following what may often have been lengthy and complex treatment. It is thus likely that general dental practitioners will need to take over the care and responsi­bility for their patients’ retainer requirements. Incidentally, however, it should be noted that whilst upper removable appliances (URAs) are appropriate for childhood interceptive treatment, they are not often useful for adults. In contrast, retainers may be worn by children or adults.
This book will also give pertinent advice on:
  • What makes a good referral letter (again in line with the General Dental Council outcomes), e.g. when a patient requires referral to a specialist for definitive orthodontic treatment.
  • What is required when and the reasons for taking over the care and responsibility of a patient’s retainer requirements.
In addition, discussion of lower removable appliances (LRAs) is included where appropriate, as well as specific chapters for the specialist trainee.
The authors acknowledge that the practical advice given in this book will sometimes not exactly match that given by every clinician, but subtle differences in approach are evident between clinicians in all specialties. The approach adopted here is one that we have found works for us. Furthermore, as this is essentially a practical guide based on clinical experience, it is not written nor intended as a fully-referenced academic text.
So, this book assumes a basic level of orthodontic knowledge of the sort you would hopefully receive from an undergraduate dental training. This means that it does not explain terms such as overjet, overbite, the different skeletal, incisor or molar classifications, etc. – it will assume you know these already. It will also not explain how to undertake an orthodontic diagnosis, only pointing out aspects of diagnosis that are relevant to the particular problem under discussion.
Also this book will not explain how to undertake all orthodontic treatment. That is a specialist area. However, what this book will do is give guidance on situations where interceptive treatment could potentially be considered and how. Yet, this can never be comprehensive since no two patients are ever entirely identical. Many aspects of diagnosis can influence a decision as to whether a treatment is reasonable, possible or even feasible.
In addition, this book does not discuss issues of consent, risks of orthodontic treatment and balancing the risk/benefit ratio. These are all vital issues, but again we assume a level of knowledge that basic undergraduate dental training should cover.
Lastly and obviously, this book provides no direct practical experience whatsoever!
Upper Removable Appliances: Indications and Principles of Design
Upper removable appliances (URAs) are ‘removable braces’ that fit on the upper arch only. In the past, URAs were used for many malocclusions, including severe Class II division 1 cases. However, this is no longer seen as appropriate because removable appliances can only achieve very simple movements, i.e. simple tipping of teeth, and the vast majority of malocclusions that warrant treatment require far more complex movements (using fixed appliances) to achieve an adequate outcome. Fixed appliances can also tip teeth, but in complete contrast to removable appliances, they can also achieve bodily movement (including rotations, intrusion and extrusion) as well as torque. Therefore, regarding active treatment, this book will mostly confine itself to interceptive treatment where the types of malocclusion to be intercepted are very limited; if tooth movement is required, it is confined to tipping movements. The exceptions are covered in Chapters 10 and 11.
Learning Outcomes
After reading this chapter you should know:
  • The indications for the use of URAs
  • The importance of anchorage
  • The advantages and disadvantages of removable appliances
  • What the components of URAs are
  • What the components of URAs look like
  • The design principles and steps to consider when designing URAs
  • The importance of the timing of appointments

Prerequisites for Orthodontic Treatment

It must be understood that for any patient seeking any form of orthodontic treatment, dental health (including dietary control) and oral hygiene must be excellent prior to treatment. Therefore, before any referral is made, the referring dentist must ensure that their patient is dentally fit, i.e. no active caries, gingivitis or periodontal disease, and that they have a standard of oral hygiene that is excellent – this is the level required to support appliance therapy. A number of recent audits in the UK have indicated that 30% of patients have undiagnosed/untreated caries on referral to an orthodontist. This wastes a great deal of everyone’s time as, obviously, the orthodontist cannot accept a patient for treatment if the patient is not dentally fit and/or has poor oral hygiene/diet control. This is because significant damage, e.g. caries, will be caused to the teeth and supporting structures by any appliance used under the wrong conditions. Damage will also occur far more quickly and severely than under normal conditons. Furthermore, restoration of teeth is more difficult once appliances are in place.
If, as the referring clinician, your patient cannot meet these conditions, but wants orthodontic treatment, you will need to explain to the patient/carers why referral is inappropriate and what the consequences of poor dental health are for their orthodontic treatment prospects. Treatment may be harder or more complicated if treatment has to be delayed until growth is (nearly) completed. Indeed, treatment may not be feasible unless dental health improves.
Oral hygiene that is less than optimal may lead to demineralisation of the enamel surface around or under any appliance, including the attachments of a fixed appliance. Such demineralisation can actually occur within a few weeks of an appliance being placed and, if severe, can lead to cavitation. The benefit of orthodontic treatment in providing a good occlusion and smile aesthetics is thus undone by the marking on the labial surfaces of the teeth in the case of fixed appliances (see Figure 5.20). However, around URAs damage may be hidden palatally from the patient and unwary clinician.
Moving teeth through bone in the presence of gingival inflammation and/or active periodontal disease will lead to very rapid destruction of the alveolar bone. Therefore, tooth movement should never be undertaken until the disease has been successfully treated; there is no bleeding from the gingival margins or the base of the periodontal pockets, and the patient has demonstrated that they are able to maintain the necessary level of oral hygiene.
It should be emphasised that before any appliance is fitted, a full orthodontic assessment (including appropriate radiographs) and diagnosis must have been performed. A problem list derived from the case assessment will then form the basis of a proper treatment plan. It is assumed that readers are able to undertake these tasks appropriately and the details of these steps are not covered here. To refresh your memory on any aspects of assessment, diagnosis or treatment planning, readers are referred to other textbooks.


Before discussing how to design URAs, we need to briefly remind ourselves about one very important aspect of orthodontic treatment – anchorage. Unless anchorage is given appropriate consideration, orthodontic treatment cannot only easily fail, but the original malocclusion can be made much worse.

What Is Anchorage?

Anchorage is most easily defined as the resistance to unwanted tooth movement. In other words, it is what stops the wrong teeth from moving. Newton’s Third Law of Motion states that: ‘To every action there is an equal and opposite reaction’.
In orthodontics, because of Newton’s Third Law, we can all too easily find that unwanted tooth movement takes place. In order to minimise such movement, it is generally accepted that during URA treatment, only one or two teeth should be moved at a time. This means that the movement of a few teeth (or a tooth) is being pitted against the movement of many or the majority of teeth. This works because generally, the larger number of ‘anchoring’ teeth will have a larger root surface area than the smaller number of teeth to be moved (see Figure 2.1 for examples). Whilst the equal and opposite reaction will be ‘experienced’ by all the teeth in contact with the appliance, this force will be distributed according to root surface area. Thus, large rooted teeth will ‘experience’ a large...