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ePaper created 2015-03-06, 14:42:46 | version 1.33.01
_Introduction Traditionally, the practice of dentistry has been a reparative model. We have waited for disease to expressitself,andthenrepairedit.Whatifwecould predict who would express a disease and prevent it from happening in the first place? How would this approach affect the long-term oral and overall health of the dental patient? Many of our patients tell us, “If it’s not broken, don’t fix it.” Patients are often unaware of the conditions in their mouths because there isn’t an associated disability, and they won’t accept a solu- tion to a problem they don’t have. Thus teeth at risk mayremainuntreateduntilaqualityoflifeissuehas occurred, such as pain, infection or a fractured tooth. According to Geurtsen, Schwarze, & Gunay (2003), root fractures are the third leading cause of tooth loss. Toothlossisaqualityoflifeissue.Lossofatooth ideally requires replacement, which necessitates further expenditures and procedures. Failure to replace the tooth has consequences, whichmayleadtofurthercostandneedfortreatment or loss of additional teeth. The consequence of the reactive approach to dental care is, at best, a lesser prognosisforthetoothand,atworst,lossofthetooth. This may be avoidable with a paradigm shift to a wellness model of practice. A wellness model is proactive and preventative. If we can identify a dental condition that increases risk to the tooth and patient, and treat the condition prior to its consequence, we’re effectively reducing risk. Theeffectisanimprovedprognosis.Subsequently, health-care costs will be reduced and quality of life improved. We can do better. _Biomechanical principles Tidmarsh said in 1979 that teeth are like pre- stressed laminates. They flex but can return to their natural state. However, under prolonged loading, teeth can permanently deform. Grimaldi said in 1979 that there is a relationship between how much tooth structure has been lost and deformation. Cavity preparation or endodontic access de- stroys the pre-stress state. Teeth can then deform greater and are more susceptible to fracture. Too much flexing makes them crack. Larson, Douglas and Geistfield (1981) showed that a restoration that takes up just one-third of the intercuspal distance is less than one-half of the strength of an unrestored tooth. The load required I CE article _ biomechanical principles Fig. 1a_Pre-operative photo: Diagnosis of structurally compromised teeth. Fig. 1b_Pre-op: Measuring intercuspal distance of filling #3. Fig. 1c_Pre-op: Measuring intercuspal distance of filling #4. (Photos/Provided by Michael L. Young, DDS) 12 I CAD/CAM 1_2015 Aminimallyinvasiveapproach according to biomechanical principles of teeth Author_Dr Michael L. Young, USA This article qualifies for CE credit.To take the CE quiz,log on to www.dtstudyclub.com. Click on‘CE articles’ and search for this edition of the magazine.If you are not registered with the site, you will be asked to do so before taking the quiz. _ce credit CAD/CAM Fig. 1a Fig. 1b Fig. 1c CAD0115_12-21_Young 02.03.15 12:37 Seite 1 CAD0115_12-21_Young 02.03.1512:37 Seite 1