CAD/CAM Magazine

I 09 case report _ occlusal force management I CAD/CAM 2_2011 The occlusal force and time-sequence data are relayed to a PC through a high- definition recording sensor that measures contact-varying rela- tive force sequential- ly as differing tooth contacts interact at the occlusal surfaces (Figs. 8a & b). Dur- ing a turbo-mode re- cording, the sensor is scanned 3,000 times per second, resulting in a dynamic movie of changing occlusal forces that can be incrementally viewed in a slow-motion playback. This dynamic playback separates all the force variances into their contact order, while simul- taneously grading their relative occlusal force, so thatacliniciancanobservethemfordiagnosisand possibletreatment.Intwoorthreedimensions,the contact timing sequence can be played forwards or backwards continuously or in 0.003-second increments, to reveal an occlusal “movie” that describes the occlusal condition.19 In the 3-D play- back view, the force columns change both their height and colour designation. In the 2-D contour view, the colour-coded force concentration zones alter size, shape and colour as the occlusal forces change (Fig. 7). Warmer colours indicate forceful contacts, while darker colours indicate lower force contacts (Fig. 9). _Limitations of articulating paper markings Clinicians routinely employ articulating paper tovisualisethepresenceofocclusalcontacts,their force and their time simultaneity. They determine whether contacts are forceful by subjective judge- ment of the paper markings for their supposed force content. In dental medicine, it is strongly advocated and stronglybelievedbymanycliniciansthatthechar- acteristics of the paper markings indicate occlusal forces.10,12–16 The appearance characteristics of the paper markings are based upon: a) the size of the mark: large marks supposedly indicate higher forces; small, light markings in- dicate lesser forces; b) the relative colour depth and intensity of the ink mark: the darker the mark and/or its colour in- tensity, the higher the force content; the lighter the mark, the less force content present; c) the presence of doughnut and halo shape(s): these shapes indicate that the contact is force- fulbecausethesecontactsdonothaveinkinthe middle (Fig. 10). Despite the persistence of the “clinical beliefs” listed above, there is no published scientific evi- dence that supports that these appearance char- acteristics actually indicate the relative force of occlusal contact.7–11 Studies on articulating paper markings demonstrate consistently that occlusal forces cannot be reliably determined based upon their size or colour. Additionally, paper markings have never been shown in any study to be able to describe contact-timing sequences.7–11 Figure 11a clearly illustrates the limitations of the articulating paper in describing force and that Fig. 11a_Upper first molar with three large paper marks and upper second molar with mesial scratchy paper markings. Fig. 11b_Opposing lower molars with large black paper marks on first molar and small, light marks on the second molar. Fig. 12_T-Scan III data of upper right first and second molar occlusal forces. Fig. 13_Pre-op fractured veneers. Fig. 14_Replacement of broken veneers completed with six new veneers. Fig. 14Fig. 13 Fig. 12Fig. 11bFig. 11a