Worn dentition; The Full mock up concept

27 Jul 2016 - 68553

The Mock-up is not always a tool with an aesthetic purpose, it is an excellent predictor of the functional result and an excellent guide for minimal invasive preparations while giving perfect space.

The purpose of this article is to suggest a precise and consistent method that simplifies the treatment of worn dentition. A wax-up and a mock-up are mostly used for designing esthetic outcome, and then used as a preparation guide. As described by the authors, it can as well be used on the posterior occlusal surfaces of the teeth. This not only provides the exact new vertical dimension of occlusion but lets the dentist use it as a guide for precise control of occlusal preparation.

Fig. 1

Worn dentition is a triple challenge for the dentist:
1. Aesthetically, teeth are too short
2. Biologically, we need the tooth structure to be healthy and as intact as possible
3. Functionally, new occlusion arrangement is mandatory in order to lengthen the anterior teeth.

Which kind of treatment planning can we propose to fulfill the previous requirements? Also when a dentist faces these flat smile lines because of the wear process, it is important to have a preview of the case, in order to understand the “white” modification (dental) to let the new smile line appear. This can be predicted digitally with pictures or with a device as ditramax to mark with extreme precision on the model with the facial references .

Fig. 2

On the lateral view we can see how the smile line is inverted and the length of the anterior teeth give an unaesthetic display, with lack of continuity between central, lateral and canine.

Fig. 3

The intraoral view shows wear process, most probably due to abrasion phenomena (parafunctional activity) and erosion (soft drink consumption, GERD). Some dysplasia can be noted in various dental elements, and the patient was not willing to undergo orthodontic treatment, which would have been ideal to align tooth 31.

Fig. 4

Tooth 23 is locked in static position and also not functioning during lateral movement. This observation among many others, confirm the need of increasing VDO in centric position to allow the new incisal edge and canine shape to participate in the natural occlusion movements.

Fig. 5

A silicone index was prepared from the wax up and was cut horizontally in order to evaluate, from the very beginning, the amount of tooth structure that could be removed to ensure a minimum of 0,5 mm thickness for the laminates. In many cases we are 100% additive, although this does not means no prep because of the great challenges that this difficult “no-prep” technique holds (especially for the laboratory and for the cementation procedures).

Fig. 6

Then a full mock-up is performed to visualize the esthetic and functional project for the future situation (luxatemp star DMG).

Fig. 7

Once the new occlusal anatomy is placed, it is crucial to check the occlusion, until simultaneous contacts are found. Generally the fitting is perfect. This functional mock-up, or functional pre-visualized temporaries (FTP) related to APT (aesthetic pre-visualized temporaries) according to Galip Gurel – will be used as a precise guide for minimally invasive posterior prep.

Fig. 8

Mock-up must be evaluated in the aesthetic area as well, to guide the veneer preparation in the buccal area.

Fig. 9

The new smile line has to be checked, specially the harmony between the new curve and the lower lip. Look how the asymmetry of the patient has to match the situation we projected.

Fig. 10

The FPT (functional previsualized temporary) is used as a GPS for preparation guidance. Three main grooves will be performed to control the homogeneity of the occlusal reduction to remain in the 0,5 mm thickness for these occlusal veneers.

Fig. 11

Same protocol is applied simultaneously in the anterior area.

Fig. 12

Once the mock up is removed, we can see that, many times, there will be no mark on natural teeth.

Fig. 13

The prep-less approach is indicated to let the technician visualize the margin and as well let the dentist control the fit the day of the cementation.

Fig. 14

Once the depth cuts were done for the guided preparation, we can finalize the preparation design. This has to be simple and is defined as follows:

– cover the cusps if they are already too thin
– get to the edge of the vestibular cusp if needed aesthetically (lengthen the cusp for the smile line )
– preserve the marginal ridge (1 mm on the inside) or cover the top of the ridge if worn.
– a smooth and flat design should be created between the cusps

Fig. 15

The occlusal surfaces are made by disilicate press technique (emax press HT) and stained. Also thanks to the press technique we can wax a very thin layer (0,5 minimum thickness).

Why 0,5 mm instead of the 1,5 mm of a traditional overlay? Because when considering the sole occlusal surface, the loadings are axial: thus, restorations will only be loaded in compression, on a vertical axis, while overlays are loaded both in compression and tension. The natural marginal ridge will keep on doing its job instead of the material.

Fig. 16

For the premolars sometimes is possible to use the sandwich concept proposed by Dr. Vailati (2008) to preserve as much as possible the healthy teeth structure by bonding two pieces in a retentive tooth. If the defect is bigger and not retentive, it is possible to go for one piece only.

Fig. 17

Note the preservation of the natural marginal ridge and the optical integration of the restoration.

Fig. 18

Laminate veneers were bonded one by one (10 min per restoration) with an individual dam.

Fig. 19

New arch, new occlusion, minimum invasiveness.

Fig. 20

The new smile line creates a good look of the new silhouette.

Fig. 21

A night guard placed in the lower arch is recommended for all the parafunctional cases to protect restorations during the night.

Fig. 22

Thanks to Gerald Ubassy and Florence Ozil for the lab work of these beautiful restorations, the power of teamwork.

Fig. 23

On the before and after pictures, the enhancement of the smile can be noted.

 

Conclusions

Worn dentition is a challenge for the dentist. Contemporary concepts must be used to fit with the minimally invasive philosophy. Clinical protocol must fit as well with the reality (feasible, teachable and repeatable). That is why a prep less method instead of no prep is more useful for every day practice.

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