Dental Tribune United Kingdom Edition

the devitalisation of at least two teeth. After discussing again with her the possible options, which also included the ones she had already been given, we decided that we could attempt to gain as much of an improvement as possible with short term or- thodontics possibly followed by more conservative restorative treatment if orthodontic treat- ment alone could not provide a satisfactory outcome. We opted for a fixed appli- ance and CR was fitted with this in July 2010. She attended monthly there- after for a period of six months during which time minimal in- terproximal reduction was car- ried out and arch wires changed accordingly. At the end of this period we arrived at a posi- tion where the patient decided she was happy enough with the appearance and wished to conclude treatment. It was sug- gested that there was still room for further improvement if the appliance was left in place for around two more months; how- ever this was not possible due to the impending wedding. Once the appliance was re- moved we carried out a chair- side tooth whitening procedure followed by composite bonding to even out some differential tooth wear. The patient did not feel the need for any further cosmetic treatment and was happy to finish treatment at this stage. Discussion The most obvious question when looking at cases such as these is how space is cre- ated in what appears to be a moderately severely crowded arch without the removal of any teeth. Knowing the an- swer still does not cease to amaze. Looking back at this case, and other such cases that we’ve since completed, calcu- lating how much space is re- quired, predicting how much space is available and how to gain this space is one of the keys to understanding short- term orthodontics. In short term orthodontics space is gained in mainly two ways: • Interproximal reduction • The arch rounding out (Upper arch expansion can also be used but brings with it additional complexities and considerations which for the purposes of this overview I will not be discussing.) Interproximal reduction Interproximal reduction, also known as interdental stripping, reproximation and tooth slen- derising is the careful removal of a defined amount of enamel from the proximal surface of a tooth. Studies show that enamel reduction does not appear to expose the enamel to patholog- ical changes that could lead to caries and interdental stripping can be considered a reasonable therapeutic technique, espe- cially if care is taken to avoid abrasion in more gingivally lo- cated enamel The maximum space gained in this way in a complete den- tition between the mesial sur- face of the first premolar to the mesial surface of the adjacent first premolar, is around 4mm. In the vast majority of crowded cases we treat, the amount of space that can be gained by IPR alone is more than adequate to give a consid- erable improvement in aesthet- ics. However in conjunction with the arch rounding out we often do not have to remove the full 4mm of enamel. Rounding out the arch As arches round out we can gain a significant amount of space. To understand this more fully we need to go back to our geometry lessons. Let’s think of our arch as an arc or part of the circumference of a circle. The relationship between the diameter and circumference of a circle can be defined as pi or 3.14. Hence if we have a circle that has a diameter of 1cm its circumference is 3.14cm. Or put more simply - the circum- ference of a circle is roughly three times that of its diameter. Hence for every one unit in- crease in diameter we get three times the increase in circum- ference. Now going back to the case in question. When we look again at the upper arch we can see on diagram below, the black line shows simplistically how “flat” the anterior inci- sors are. The blue curve indi- cates the likely end position of the teeth where the arch-wire of the fixed appliance natu- rally wants to take them. It is this “rounding out”, in effect increasing the diameter of the arc or circle that gives us quite a significant amount of space circumferentially. This principle is usually very dramatic in class 2 div 2 situations as the case below demonstrates. On first glance this appears to be a very crowded case. However, after just one month of treatment and no IPR it be- comes a very spaced case: This can now be quite sim- ply treated as the finished re- sult below shows. This total time taken to treat this case was around four months. Space calculation There are three main ways to calculate how much space is required in the crowded denti- tion 1Guesstimate based on clin- ical examination, models and pictures 2Measurement using Ver- nier Gauge 3Ask the laboratory to assist By far the most common way used is option one and with experience is very reli- able. However the most ac- curate method is by meas- uring the mesial to distal width of each individual tooth from canine to canine, giving us the required space, and then to measure the length of span of the teeth in the final posi- tion – the available space. Sub- traction of one from the other determines how much space is required using IPR. However it is possible that no IPR at all is required, the above class 2 div 2 case being a good example of this. Discussion Although the vast majority of cases that are treated this way tend to be of minor crowding, minor spacing or misalign- ments, the above case of patient CR does demonstrate that with the proper understanding we can also treat more dramatic situations that would otherwise necessitate significant destruc- tion of healthy tooth tissue, or even require extractions. In summary short term orthodon- tics has roles to play in the fol- lowing situations: • Rounding out arches • Levelling and aligning the an- terior teeth • Correcting simple to moder- ate crowding • Correcting simple to moder- ate spacing • Rotations • Aligning gingival margins and improving emergence profiles • Up righting teeth that are flared or tipped • Pre-restorative treatment alignment • Avoiding elective endodontics Looking at the above list gives us an idea of how valua- ble a tool short term orthodon- tics can be in the provision of cosmetic dentistry. The occlusion In each case we need to also understand that we do not in- tend to change the posterior occlusion permanently or at the very least detrimentally. Invari- ably changes in occlusion will occur during treatment as quite often the bite will be propped open on the anterior teeth lead- ing to mainly Dahl type move- ments posteriorly. However, going back to our definition of short term orthodontics, the appliances are rarely worn for over six months and any move- ment posteriorly will either completely settle or not pose any long term problems, as re- ported by N J Poyser et al; The Dahl Concept: past, present and future. British Dental Journal 198, 669 - 676 (2005), “The de- March 26-April 1, 201222 United Kingdom EditionClinical page 21DTß ‘In the vast majority of crowded cases we treat, the amount of space that can be gained by IPR alone is more than adequate to give a considerable improve- ment in aesthetics’ Fig 2 - CR002 Fig 3 - CR003 Fig 4 - CR004 Fig 5 - CR005 Fig 6 - CR006 Fig 7 - CR007