Worn dentition; The Full mock up concept

27 Jul 2016 - 67921

Mock-up is not always a tool for aesthetic outcome, 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

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 the dentist face these flat smile lines because of the wear process, is important to have a preview of the case, this means 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

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

Fig 3.- The intraoral view shows wear process, most probably due to abrasion phenomena (parafunctionals habits) and erosion (soft drink consumption, Gastroesophagic reflux ). Some dysplasia can be noted in various dental elements, and the patient was not willing to undergo an orthodontic treatment, which would have been ideal to align element 3.1.

Fig. 4

Fig 4.- Tooth 2.3 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

Fig 5.- A silicon 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

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

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 previsualized temporaries (FTP) related to APT (aesthetic pre-visualised temporaries) according to Galip Gurel – will be used as a precise guide for minimally invasive posterior prep.

Fig. 8

Fig 8.- Mock-up must be evaluated in the aesthetic area as well, to guide the veneer preparation in the buccal area.

Fig. 9

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

Fig 10.- The FPT (functional previsualised 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

Fig 11.- Same protocol is applied simultaneously in the anterior area

Fig. 12

Fig 12.- Once the mock up is removed, we can see that, many times, there will be no mark on natural teeth.

Fig. 13

Fig 13.- 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

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 (lenghten 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

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

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

Fig 17.- Note the preservation of the natural marginal ridge and the optical integration of the restoration.

Fig. 18

Fig 18.- Laminate veneers were bonded one by one (10 min per restoration) with an individual dam.

Fig. 19

Fig 19.- New arch, new occlusion, minimum invasiveness.

Fig. 20

Fig 20.- The new smile line creates a good look of the new silhouette.

Fig. 21

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

Fig 22.- Thanks to Gerald Ubassy and Florence Ozil for he lab work of these beautiful restorations, the power of teamwork.

Fig. 23

Fig 23.- On the before and after pictures, the enhancement of the smile can be noted.