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42 Dental Tribune Middle East & Africa Edition | January-February 2016 general dentistry Tooth wear, the Dahl principle, the Inman Aligner and a real option for interceptive dentistry > Page 43 Figure 1. Patient A before treatment showing inter-canine collapse and crowding. Figure 4. Patient B before treatment. Figure 7. Patient in occlusion with Dahl com- posite added to lower anterior teeth. Note poste- riors in contact at 3 months. Figure 2. Immediately after alignment and whitening. Figure 5. Following alignment and increase of inter-canine width. Figure 8. Occlusal view before. Figure 3. Six years with retention post-treat- ment. Figure 6. Patient C in occlusion with deep bite. Note the posterior contacts. Dr. Tif Qureshi discusses a different way of looking at preventative occlusal treatment through alignment and bonding reliable and useful when there is anterior tooth wear. For large posterior tooth wear cases, the patient required the whole ver- tical to be opened and all teeth treated, but for patients who are starting to develop wear in the anterior region (which can lead to posterior wear), it is a very in- terestinginterceptivetreatment and the question has to be why this is not offered a lot more. The following case highlights its potential use. In the next article, we will address a case with the loss of inter-canine width. Case report A 43-year-old female (Patient C) presented complaining of “crooked front teeth”. Her main concern was her lower teeth. She asked for them to be “straighter”. She also com- plained of jaw joint pain and a “clicky” jaw. On examination, it was clear that there was mild to moderate crowding of the lower anteri- ors. Space calculation showed 3.5mm of crowding, which meant that 3.5mm of space needed to be created to allow the teeth to align. Space calcu- lations can be carried out by Hanchers technique,5 manually or using a digital space calcula- tor, such as Spacewize. These space calculators are an excel- lent way for clinicians to visual- ize how much actual crowding there is and exactly where the teeth need to go as this becomes a perfect prescription for the lab setup. The width of only one tooth needs to be measured as the program will use this for cali- bration. The dentist simply then draws lines on the teeth done by a single click that measures the mesial-distal width of each tooth being moved (known as the required space, or ‘the teeth’)andthentheprogramme allows a curve to be intuitively set up that follows the line of the ideal curve (known as the available space or ‘the curve’). The curve needs to be set through the landmark teeth By Dr .Tif Qureshi, UK I n my opinion, simple ante- rior orthodontics has been overlooked for many years as potentially one of the most important and useful areas in dentistry. This can be high- lighted by the suggestion that many dentists simply do not identify or recognize that the increased crowding in the an- terior region over time can lead to, or is linked to, a collapse of lower inter-canine width that can then lead to loss of canine guidance and the development of group function with the potential issues that that can sometimes cause. This loss of guidance can hap- pen in a relatively short period of time as the canines lose their protective function once they tip inwards. It is likely a combi- nation of factors lead to this but there seems to be very little data collected, however this is a phe- nomena that is clearly visible when examining many patients every single day. If we think forward when look- ing at a case such as that fea- tured in Figure 1, several prob- lems could start to potentially develop over time. Firstly, the crowding could worsen, leading to increased risk of periodontal disease. The likelihood of differential tooth wear is also increased as the teeth crowd further. Areas al- ready worn down to dentine are likely to wear faster because of the softer nature of the sub- strate. Exposed dentine is also likely to stain more as open tubules are likely to allow ingress of par- ticles that over time, commonly cause intrinsic staining. If the canines continue to tip in- wards, there will be a loss of ca- nine guidance that might well cause the transition to group function which could become traumatic if not monitored (and possibly treated). Many patients left untreated eventually need large amounts of work, up to and including full mouth den- tistry. So if patients are in a situ- ation where lower crowding is starting or has started, surely it makes sense to align the lower teeth, upright the canines and then apply retention to ensure this is less likely to relapse (Fig- ures 2- 3). Figures 4 and 5 show another case before and after alignment with an a resulting increase of inter-canine width. If the edges are already worn, it is also possible to restore the tips to seal the exposed dentine and improve aesthetics. In cas- es with more extensive wear, this can be combined with the Dahl principle where space can be reclaimed by opening the anterior bite, disengaging the posterior teeth and allowing the posteriors to over erupt and the anteriors to intrude a little.1 The Dahl principle Modified Lucia jigs have been used as deprogrammers to help the mandible find centric rela- tion (CR). Direct composites can also be used as an anterior deprogrammer. Resin compos- ites - because of their resilience and ease of manipulation even in small thicknesses - represent an ideal material to restore the palatal surface2 and the worn lower anterior incisal and ca- nine edges too. Dahl (1975) suggested creating space to treat localised anterior tooth wear by separating the posterior teeth using an ante- rior bite plane for 4-6 months.3 A combination of passive erup- tion of the posterior teeth and intrusion of the anterior teeth allowed the re-establishment of posterior occlusion while hold- ing the anterior space.4 Dahl actually used a metal appliance to separate the posterior teeth, but we can now achieve the same result with adhesive ante- rior direct composites. By identifying the difference between maximum intercuspal position and CR, using pressure to gently guide the mandible, the position of the direct com- posite can be set slightly pos- terior to maximum intercuspal position. This will create ante- rior contact on the incisal edge build-ups and possibly create premature contacts on the pos- terior teeth. These premature contacts can be equilibrated to improve the amount of con- tact, but the residual space will eventually close through pas- siveeruptionoverafewmonths. I have used this principle for over 15 years on over 500 pa- tients with continued success. The important part of the Dahl principle is not to use it on ag- gressively worn full mouth cases. During the “cosmetic boom” years, virtually every single veneer case I placed on the upper teeth had composite tip build-ups on six to eight lower anterior teeth to treat any wear and re-establish guidance be- fore fitting the upper ceramics. I used up to 2.5mm of compos- ite anteriorly and this seemed to cause a combination of extru- sion of the posteriors and possi- bly intrusion anteriorly. I rarely ever placed ceramic directly on lower teeth because I could im- prove aesthetics and function with non-invasive composites instead. Yes, they can wear but the usual life span for these was about five to eight years and most patients were totally satis- fied with this when compared against tooth preparation and the cost of veneers. Itisimportanttoemphasizethat the Dahl principle is really only - meaning teeth that are well- placed occlusally and aestheti- cally. This will prevent the teeth from being flared out and ensure correct occusal control. The program then does the sums and subtracts the re- quired space from the available space. Thisfigureis theamount of crowding present and hence the amount of space that might need to be created with inter- proximal reduction (IPR), ex- pansion or domino effect. In this case, there was clearly also a deep bite emerging and reducing anterior and canine guidance. On discussion with the patient, close anterior photos were ex- amined. It was pointed out that the anterior teeth were all at different lengths. Often before alignment, patients do not see this. Their eyes are focused on the crowding and they do not realize that the irregular outline is equally due to dif- ferential wear. This discus- sion is very important because patients must be aware of the extra treatment that may be needed after alignment. In my experience, most adults have some degree of differen- tial wear. After alignment, I rarely grind teeth to level them off as this is clearly destructive and will only lead to reducing guidance and increasing poste- rior interferences over time. In- stead, I nearly always build and open the bite anteriorly with composite and induce the Dahl effect. Those treating adults with orthodontics must be able to re-build the tooth structure or co-plan with a restorative dentist so the patient’s guidance is protected. The patient wanted an Inman Aligner as she wanted her teeth to align quickly and also to be able to remove the appliance for periods at work. We also quoted for eight composite tips to im- prove the aesthetics, treat the deep bite and induce the Dahl effect to establish better ante- Figure 9. Spacewize calculation shows 3.8mm crowding.