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Current Products and Practice

The Bigger The Better: can magnification aid orthodontic clinical practice?

K. J. Juggins

The John Radcliffe Hospital, Oxford, UK and the Eastman Dental Institute, London, UK

Address for correspondence: K. J. Juggins, Department of Orthodontics, Level 2, The John Radcliffe Hospital, Headley Way, Oxford OX3 9DU, UK. Email: kjjuggins{at}hotmail.com

	Abstract

Top Abstract Introduction Getting to grips with... What is available and... What to look for... Advantages of magnification Disadvantages of magnification Conclusions References

 
The use of magnification in dentistry appears to be of increasing interest. This is also reflected in our own specialty, with a number of optical companies exhibiting their products at orthodontic conferences and meetings. This article reviews the principles of magnification, briefly discusses the magnification loupes that are available on the market at the present time, and highlights the advantages and disadvantages of using magnification for orthodontic treatment.

Key words: Orthodontics, magnification, loupes

	Introduction

Top Abstract Introduction Getting to grips with... What is available and... What to look for... Advantages of magnification Disadvantages of magnification Conclusions References

 
The use of magnification in dentistry is not a new concept. The suggested benefits brought by enhanced vision and improved working posture are well publicized.^1–5 Although there have been many anecdotal reports describing the benefits of magnification,^2–4 there have been very few clinical studies that systematically assess this.^6,7

Dentistry is a visually demanding profession. Indeed, visual enhancement is becoming far more acceptable and many dental schools now allow their students to use loupes on a discretionary basis. In the USA, training with dental magnification is mandatory for specialists in endodontics.⁵

New techniques, tooth-coloured materials and finer instruments all aim to provide the best standard of patient care. This suggests that visual enhancement has a place in our clinical practice. Perhaps not surprisingly, there is very little to be found in the literature regarding the benefits of magnification eyewear in orthodontics. However, attention to fine detail is paramount for our work. Smaller bracket systems, lingual appliances, self-ligating systems and ceramics continue to evolve.

Could we improve our standard of patient care with magnification? Moreover, would magnification benefit our own musculoskeletal health?

This article aims to discuss the basic principles of magnification, highlights what is available on the market at the present time, and discusses the perceived advantages and disadvantages.

	Getting to grips with magnification

Top Abstract Introduction Getting to grips with... What is available and... What to look for... Advantages of magnification Disadvantages of magnification Conclusions References

 
Visual acuity is limited by the accuracy with which the image is focused on the retina. To see clearly objects closer than 6 m, the thickness of the ocular lens needs to be altered. This is accommodation, and is facilitated by contraction or relaxation of the ciliary muscles.

In the UK, visual acuity is checked with a Snellen chart at 6 m. The numbers next to the letters indicate the distance that a person with no refractive error can read that line. Visual acuity of 6/6 is the accepted normal (i.e. that which a person with normal vision can read at 6 m). A person with 6/3 vision could read at 6 m what a standard person could only read at 3 m and a person with 6/60 vision could read only at 6 m what a standard person could read at 60 m.

Visual acuity is likely to affect working posture. The working distance (i.e. the distance between the operator’s eye and the patient’s tooth) varies between 25 and 36 cm. If the operator requires a larger image they have 2 choices. Either they move closer to the object, compromising their posture or they need to use magnification.

Presbyopia, an inability to focus sharply on close objects, also has an effect on working distance. This condition is a normal consequence of ageing, affecting everybody at some stage. Older orthodontists may find that this has significant implications on their clinical practice and the use of magnification may in some cases increase performance and clinical outcome, and improve working posture.

	What is available and what do you really need?

Top Abstract Introduction Getting to grips with... What is available and... What to look for... Advantages of magnification Disadvantages of magnification Conclusions References

 
There are 3 magnification systems in dentistry. Single lens loupes, Galilean loupes and prismatic loupes. The Galilean and prismatic loupes can be either a flip-up or through-the-lens design (see Figures 1 and 2).

View larger version (61K): [in this window] [in a new window]   Figure 1 Flip-up telescope. This is the Supervu telescope with Hoggie frame manufactured by Keeler

View larger version (27K): [in this window] [in a new window]   Figure 2 Through-the-lens/fixed telescope. This is an expanded field dental telescope manufactured by Designs For Vision

Galilean loupes
Galilean loupes or 2 power compound loupes are usually a Galilean design. They use 2 or more lenses, which offer higher magnification, improved working distance and depth of field. They can be tailor-made to the individual and have the benefit that illumination can be added. However, they are considerably more expensive than single lens loupes, and the increased magnification occasionally incurs problems with the weight and size of the loupes.

Prismatic loupes
These are 3 or 4 power compound loupes and often of Keplerian design. Similar to binoculars, they use around 5 lenses and 2 prisms to give higher levels of magnification and greater optical clarity. Again these systems can be tailor-made for the individual. However, the increased number of lenses does make them very expensive and heavier, and the higher power results in a smaller field of view.

	What to look for when buying loupes

Top Abstract Introduction Getting to grips with... What is available and... What to look for... Advantages of magnification Disadvantages of magnification Conclusions References

 
Superior visualization is governed by the following factors, in order of importance: resolution, field width and field depth.

Resolution
Resolution is the capability to visualize small structures. It is set by the quality of the optical design and the use of precision lenses.

Field width
Field width is the size of the operating area when viewed through the loupes. It is linked to the diameter of the telescope, the optical design, the distance from the lens to the eye and the magnifying power—the higher the power the smaller the field.

Field depth
This is the range of focus delivered by the loupe. Longer field depths allow more of the operating area to be viewed.

Flip-up or Through-the-lens?
The main advantage of the flip-up system (see Figure 1) is that it can be flipped up for an unmagnified assessment of the field of view. However, there is increased likelihood of contamination (during adjustment), and they are often bulkier and heavier than fixed systems. In addition, repeated movement can cause the telescopes to go out of adjustment. Through-the-lens (fixed system) telescopes (see Figure 2), customized to the individual, allow the operator to view the field, whilst adopting the correct posture. They are often lightweight as they do not have a suspension mechanism. However, change of the operator eye prescription usually necessitates return of the telescopes to the manufacturer.

What magnification?
The majority of loupes marketed for general dentistry are x 2.5 magnification. For endodontics and crown and bridgework, magnification in the range of x 3.5 to x 4.5 appears to be more appropriate. No specific magnification is recommended for orthodontics, although between x 2.5 and x 3.0 seems reasonable.

It is important to re-emphasize that a bigger image does not necessarily mean better visualization. The best loupes combine resolution, field width and field depth. Identifying the correct loupes for an individual should always be done in consultation with an experienced sales representative.

Loupe manufacturers
Table 1 indicates the main manufacturers of dental loupes. It shows the products currently available and highlights the individual features of each.

	Advantages of magnification

Top Abstract Introduction Getting to grips with... What is available and... What to look for... Advantages of magnification Disadvantages of magnification Conclusions References

Improved posture
Achieving improved visual acuity by moving closer to the patient compromises the operator’s working position. This posture, achieved by adopting a curved spine, can lead to muscle strain and cause back and neck problems. Rather alarmingly, studies have shown that 70% of dental professionals have experienced back pain.^8,9

By establishing the correct working distance, correct working posture is automatically achieved. This effectively reduces the muscle strain in the shoulders, back, and neck and provides enhanced musculoskeletal health.

	Disadvantages of magnification

Top Abstract Introduction Getting to grips with... What is available and... What to look for... Advantages of magnification Disadvantages of magnification Conclusions References

 
Significant cost
The cost of magnification systems varies widely and can range from £25 to thousands of pounds. Generally, for a standard, Galilean, through-the-lens system with a magnification of x 2.5 you can expect to pay around £1000. The larger manufacturing companies offer professional advice and help with purchasing magnification systems and it is advisable to discuss your individual requirements prior to buying.

Cross-infection
Assessment of the overall occlusion, in addition to closeup detail work, is essential during orthodontic treatment. Infection control, when using magnifying loupes, can therefore be difficult. Fixed loupes offer the safest method of infection control. As the telescopes are light enough and easy to see around if necessary, they do not need to be touched during the procedure. Flip-up designs on the other hand, may be flipped up and down during the procedure. Cross-contamination occurs as soon as the telescopes are touched and is particularly dangerous if the telescopes are not disinfected between patients. It is recommended that all types of telescope are disinfected with alcohol (isopropyl alcohol 70%), and that you should re-glove each time you raise or lower a flip-up telescope. To maintain good cross-infection control some manufacturers have sealed oculars, which allow washing.

Peculiarity to patients, particularly children
The appearance of magnifying loupes can at first seem somewhat bizarre to many children and occasionally frightening. However, with the benefit of a reassuring explanation, most children are more amenable and accepting of gadgets than many adults!

Visual acuity
It is sensible to discuss the use of magnification with your optometrist and essential to allow the manufacturing company to tailor make the loupes to your prescription. To prevent eyestrain and its associated consequences, it is imperative that the interpupillary distance is set accurately and that the angle of convergence between the 2 eye pieces is equal.

	Conclusions

Top Abstract Introduction Getting to grips with... What is available and... What to look for... Advantages of magnification Disadvantages of magnification Conclusions References

 
As orthodontic technology advances, we must consider what kind of visual acuity we need to perform high quality orthodontics. It is important that the benefits of magnification are recognized, and that consideration is given to its use in order that orthodontic clinical practice and patient care continues to improve.

Useful websites
www.eagleoptical.com: A useful website which lists factors to consider when buying loupes and gives information on their range of products.

www.orascoptic.com: Provides informative guide to purchasing dental loupes. They recommend Orascoptic loupes (x 2.5 magnification) and the new HiRes for orthodontists.

www.designsforvision.com: Provides basic details of dental telescopes and offers a 45 day free trial.

www.videns.co.uk: In detail account of their loupe systems and outlines principles of magnification loupes.

www.surgitel.com: Provides in detail accounts of products available and explanation of technical and magnification terminology.

www.keeler.co.uk: Details of wide range of dental loupes.

	Notes

 
Refereed paper

	References

Top Abstract Introduction Getting to grips with... What is available and... What to look for... Advantages of magnification Disadvantages of magnification Conclusions References

 
1 Friedman MJ. Magnification in a restorative dental practice: from loupes to microscopes. Compend Contin Educ Dent 2004; 25: 53–5.

2 Christensen GJ. Magnification in dentistry: useful tool or another gimmick? J Am Dent Assoc 2003; 134: 1647–50.[Free Full Text]

3 Forgie AH. Magnification: what is available, and will it aid your clinical practice? Dent Update 2001; 28: 125–8.[Medline]

4 Millar BJ. Focus on loupes. Br Dent J 1998; 185: 504–8.[Medline]

5 Friedman M, Mora AF, Schmidt R. Microscope-assisted precision dentistry. Compend Contin Educ Dent 1999; 20: 723–8.

6 Lussi A, Kronenberg O, Megert B. The effect of magnification on the iatrogenic damage to adjacent tooth surfaces during class II preparation. J Dent 2003; 31: 291–6.[Medline]

7 Forgie AH, Pine CM, Pitts NB. Restoration removal with and without the aid of magnification. J Oral Rehabil 2001; 28 : 309–13.[Medline]

8 Al Wazzan KA, Almas K, Al Shethri SE, Al-Qahtani MQ. Back and neck problems among dentists and dental auxiliaries. J Contemp Dent Pract 2001; 2:17–30.[Medline]

9 Rising DW, Bennett BC, Hursh K, Plesh O. Reports of body pain in a dental student population. J Am Dent Assoc 2005; 136: 81–6.[Abstract/Free Full Text]

This article has been cited by other articles:

				M. Meraner and J. B. Nase Magnification in Dental Practice and Education: Experience and Attitudes of a Dental School Faculty J Dent Educ., June 1, 2008; 72(6): 698 - 706. [Abstract] [Full Text] [PDF]

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