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Dental Tribune Middle East & Africa Edition | 3/2016 22 restorative consideredtobeinthe0mmto3mm range dependent on age. To achieve the correct position the edges of the loweranteriorteethneedtobeshort- enedorlengthenedbyeitherremov- ing stone or adding wax. For exam- ple,ifcrownlengtheningisindicated on teeth that were previously ideally proportioned,theincisaledgelength can be reduced. Establishing the cor- rectamountoflowertoothexposure dependent upon the age of the pa- tient at rest should be the goal. Once the final lower incisal edge position is determined, the lower occlusal planeisevaluated. Step4:CurveofSpee For this the PMS method is used to establish the anatomically average curvesofSpeeandMonson,ofthera- dius of a 4” circle. This is done using a Boyles plane analyser (Figure 14). Forthisthreereferencepointsarere- quired. One has already been estab- lished and that is the position of the lower incisal edge position as per the aestheticrequirementsofthepatient dependent upon age. The amount of wax added to the lower incisors or amount of stone removed from the lowerincisorsonthemountedstudy casts is established by using the lip as the reference plane and calculat- ing where the lower incisal edges are and where they should be. This new level is transferred to the technician sothathisstartingpointforthewax- up is the two lower incisors. The two posterior reference points are the retro-molar pads (Figure 15), which have been shown not to change dur- ing life/tooth loss etc. There is a cer- tain amount of flexibility when es- tablishingthesetworeferencepoints as being half-way and two-thirds of thewayuptheretro-molarpads. The lower occlusal plane is estab- lished by the Boyles plane analyser resting on the waxed-up or adjusted lower incisors and the two posterior reference points on the retro-molar pads. Any over-erupted teeth are ground down and any teeth not touching are waxed-up to the ana- lyser. This creates the ideal lower oc- clusalplane(Figures16-18).Thelower incisal plane should be leveled to the chosen horizontal reference plane (the inter-commissural line, inter- pupillary line etc), and evaluated from the frontal perspective while the patient is smiling. The next step istoevaluatetheocclusalplanefrom asagittalviewofthepatient’ssmile. Step5:Upperincisaledgepo- sition Next, the upper incisal edge position shouldbeestablished.Thisisdoneby aesthetics and phonetics, especially the ‘F’ and ‘V’ sounds to establish the labio-lingual position. Aesthetically, the incisal edge position is evalu- ated in relationship to the upper lip at rest. Age is again used as a guide and it is common that the range of incisal edge show may be between 1mm and 5mm. The horizontal an- teriorplanes,inter-pupillarylineand inter-commissural lines are again used to establish the correct posi- tions. The midline position of the upper incisors can be taken from several anatomical landmarks such as the facial midline, nasal midline, lip midline etc. Studies suggest the closest anatomical landmark is the most important – i.e. the midline of the upper lip. Technicians and clini- cians should also realise the extent to which they can change midlines without reverting to root canal ther- apy – approximately 1.5mm to 2mm dependinguponthesizeoftheteeth. However, special tooth preparation techniques (beveling the interproxi- mal margin one side) are required to allow for this change. Even then soft tissue problems may occur as the gingivalzenithswillmove. Step 6: Establishing anterior guidance Any space between the lower incisal edges and the palatal aspects of the upper anterior teeth is now closed by waxing the palatal aspects of the upperpalatalaspectdowntocontact the lower incisal edges to gain an in- cisal and canine stop in the intercus- pal positions (Figure 19). Adequate anterior guidance is a complex func- tion directly related to the form of the teeth, and thus to the vertical and horizontal overlap of the inci- sors and canines. Anterior guidance is influenced by the proprioception of those teeth, which provides feed- back to the masticatory muscles and influences the entire masticatory system. Unlike the posterior deter- minants, such as the slope of the articular eminence, the vertical and horizontal overlap of the anterior teethare–tovariabledegrees–ame- nable to modification. However, any modifications of the anterior teeth must satisfy not only the aesthetics and phonetics, but also the overall function.Ifthedisclusiveangleistoo steep, temporomandibular joint or musculardiscomfortmayresult. Step7:Maxillaryocclusalsur- faces Once the mandibular teeth are ideal in shape and form, wax is added to the maxillary posterior occlusal sur- faces to occlude against the mandib- ular occlusal surfaces in the correct relationship. Correct occlusal shape and form and ridge and groove di- rection,depthoffossaeandheightof cusps are now established at the set vertical dimension dependent upon the choice of articulator, facebow and articulator setting devise; check bite, cadrax, pantograph (Figures 20- 22). Step8:Refinetheocclusion The occlusal surfaces can be cor- rected to perfect the occlusal rela- tionship and to idealise the aesthetic ◊Page18 Figure13:Lipsat rest Figure14:Boylesplaneanalyser Figure17:Front Figure20:Wax-upcompleted–right handside Figure22:Left handside Figure24:Finalsmilecloseup Figure26:Pre-restorativesmile–closeupof thesmile Figure 16: Lower arch waxed up to correct curve of Spee and Monsonusing theboylesplaneanalyser-right handside Figure19:Wax-upofuppermodelshowingcon- tourandshapeofpalatalaspects Figure15:Lowerstudycast showingretromolarpads Figure18:Left handside Figure21:Front Figure23:Finalfacialview Figure25:Pre-restorativesmile ÿPage24