To match natural dentition there is no substitute for a good quality photograph with a known value shade tab in the picture. The shade tab should be in the same focal plane and be identifiable, a picture of a mystery tab is of little value.
By including a series of photographs taken from slightly different angles, all areas of the tooth may be observed without interference from flash reflection.
Be sure to include a shade tab in photo. The preps in these photos would require a high degree of opacity to block out, thus reducing the natural vitality of the restorations. Grey gingival, white opaque incisal, and intense orange-brown dentine are problems. Direct bonding with opacified composite would allow a more translucent and natural ceramic to be used. Deeper preparation in these areas would also decrease the negative effects.
The combination of high chroma and an incisal position of the preparation close to the surface of the final restorations produces a undesirable effect on #8 and #9. The greater the difference in color or opacity between preparation and final desired restorations, the more critical preparation shape and position become. More tooth reduction allows a thicker layer of ceramic material and greater filtering of underlying color. Increases in the opacity level of the ceramic can also hide underlying dentine but may produce a less life like final result. If practical, the placement of opacified composite resins directly into the prepared tooth will result in the most desirable result.
Removal of more tooth structure in the incisal one third of the preparation allowed the use of a ceramic with enough translucency to appear natural, while eliminating the undesirable show-thru of the underlying dentine.
The stick bite is our primary horizontal plane reference tool. It is important to photograph the stick in place with the patient standing up to insure accuracy. Be sure the bite registration material captures the lingual incisal of the mandibular incisors so it will seat in a stable positive manner on the lower model.
Face bows are notoriously inaccurate at recording horizontal plane information. With permission from my clients I will use the stick-bite to correct the horizontal plane of the face bow. This overcomes the difficult optical illusion of working on a case that is mounted so that the midline appears to be diagonal to the vertical axis.
Careful evaluation of this photograph allows the ceramist to look at the stone model of the provisional and either replicate the position of the incisal edge or improve upon it when the final restorations are completed.
The chin to eyebrow shows vertical midline between centrals. The 1:2 photograph shows lip architecture and tooth shape. #12 is too far facial in the 1:2. (These are 2 different patients.)
The stone model of the provisional restorations is a three dimensional representation of what we see in the photographs of the provisionalized patient. It is the cornerstone of communication between the ceramist and clinician. It provides a reference point from which changes may be made or a template for replication. Clinical photographs described in this sequence are mandatory for this process to work.
If provisional restorations are refined to final desired shape and final restorations are made utilizing all of the communication techniques presented here to ensure that the shape and position of the provisionals is reproduced accurately, clinical success is insured.
Matthew R Roberts - Providing services in Advanced Dental Education and CMR Laboratory (lab) Training.
Idaho Falls dental lab education
© copyright 2000 - 2008, Team Aesthetic Seminars - Matthew R Roberts, , all rights reserved