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A Rational Approach to High Esthetic Demand Using Minimal Invasive Dentistry A Case Report

April 1, 2007
by Gregory. P. M. Brambilla, DDS


You will never get a second chance to give someone a first impression of yourself!”

In today’s society, presentation is critical. The media dictates our lifestyles: workout, hairstyles and fashion. When these alone are not enough, we look to plastic surgery to enhance and modify what nature has given us.

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In the last few years, the field of esthetic dentistry has grown providing patients with a wide range of procedures. Dentistry has evolved to the point where patients do not merely accept function anymore as was the ’70s and ’80s. Esthetics is now the motivation for many treatments.

Many patients visit a dentist not concerned with the health problems they may have but with “that little yellow spot that you can see near the gingiva of that lateral! Doctor: don’t you see it? It’s so huge!”

On a daily basis, dentists propose to their patients options to enhance their smile ranging from tooth whitening, composite bonding, porcelain veneers and advanced multi disciplinary procedures.

This article focuses on esthetic solutions using “minimal invasive dentistry”. That is that the less that is done, the better it is.

CASE PRESENTATION

A 24-year-old girl (Figs. 1 & 2) presented due to a trauma she received at age 12 that caused a class A fracture, according to Spinas and Altana’s classification,1 to teeth #11 and #21. The right central incisor displayed discoloration although it pulp tested vital.

The initial desire of the patient was only to have tooth #21 whiter, however this tooth did not respond to a previous attempt to external bleaching.

The options I considered were:

1. porcelain veneer to change the colour,

2. jacket crown,

3. all-ceramic crown,

4. porcelain fused to metal crown.

Following the “minimal invasive” principle, I believed that endodontics was the most aggressive treatment for this case and we opted only for a porcelain veneer. However, considering the total esthetic situation of our patient, I did not believe this to be a complete solution. Looking at the patient’s face and smile, I believed that other aspects could be corrected to enhance her beauty.

After further discussion with then patient, she described other aspects of her smile that bothered her. She found her two centrals to be too large and inclined and desired that the diastemas between her teeth be closed.

When we analysed her desires, we realise that by making tooth #21 brighter and by closing the diastemas, we will make the teeth appear larger. However, she already feels that her teeth are too large. One option could be to fabricate two veneers, reshaping the centrals in order to close the diastemas and changing the length to width ratio and have them appear smaller. This can be easily done by grinding the distal part of the teeth and moving the distal line angle mesially. As the patient did not like the divergence of the central incisors, the two proposed veneers could easily change their inclination.

Closing the diastemas presented a more complicated problem as by placing two veneers on #11 and #21 we could close the diastemas but be left with centrals that would be too large. Our patient would never accept this.

SOLUTION AND SMILE DESIGN

The only way to resolve all of her esthetic problems is to treatment plan the teeth from lateral to lateral in order to create a better esthetic ratio. Before beginning treatment, we first perform a direct composite mock-up (Figs. 3 & 4) to have the possibility of visualizing the tooth esthetics with the patient’s smile and face.

As a result of the diagnostic mock-up, our final treatment plan was determined to be four feldspathic porcelain (Creation Dental Porcelain, Klema) veneers on the anterior teeth.2

To give our ceramist a template for our desired final result, an alginate impression of the direct mock-up was taken. Using this as a guide, the ceramist can create a wax-up and silicone preparation guides.

We first perform 1.5mm of incisal reduction with a but margin (Fig. 5).4,5

The but-margin gives us the possibility to create a preparation that goes deep in the interproximal areas allowing a horizontal axis of insertion without undercuts.

We next prepare the tooth facially using depth cuts of 0.6mm as our reference to not go beyond enamel (Fig. 6). We reduce the depth of preparation at the cervical to 0.3 mm which allows us to keep the preparation in the enamel.3-6

This technique was first shown by Dr. Pascal Magne, using a cylindrical burr. His aim was to obtain a preparation guide in order to give his ceramist enough space for the porcelain veneer. This procedure minimizes cutting sound tooth structure and allows us to be much more conservative as opposed to freehand preparation or even by using calibrated burs.7

I prefer using a round bur because I can better manage the depth because I use more points and my prep burr does not jump over my depth marks. With cylindrical depth marks, we risk having the preparation bur jump from mark to mark leaving an uneven surface preparation.

Depth-burs do not give us the possibility of controlling the depth at each point. Furthermore, there is a much higher risk to expose dentin, from a 50.1% of dentin exposed with depth-burs to a 77.5% with a dimple technique.7

It is essential that enamel be conserved as much as possible, and the literature states that there is a higher risk of detachments and micro-infiltration if the enamel-ceramic criteria is not followed.8

I prefer to perform the initial buccal reduction without using retraction cord (Fig. 6). This allows me to visualize how the tissue will be displaced by the cord, and I can judge how deep to prep into the sulcus, especially if there is a need to slightly modify the gingival parabula with the emergence profile of the veneer.

After the first non-imbibed retraction cord (Ultrapak, Ultradent) is in place, the preparation is then refined (Fig. 7). This initial cord is not imbibed with astringents so as to not alter the marginal tissue.

A second cord imbibed with aluminium chloride-6-hydrate 21.3% (Hemodent, Premier), is then inserted into the sulcus and left in place for 4 mins. The impression is now taken.

For the additional micro veneers, I use only one cord. As there is no preparation, there is really no need to have the sulcus wide open (Fig. 8).

Using the silicon template that has been created from the initial wax-up. A provisional restoration is made using acrylic resin and luted with a spot-etch bonding technique.

At the insertion appointment, the provisionals are removed, the preparations cleaned with a non-fluoride paste, and the single full veneer is tried. It is difficult and risky to attempt to try the additional veneers because of the ultra-thin thickness of the ceramic (Fig. 9).

After the rubber dam is in place, the teeth are cleaned and washed with Chlorhexidine 0.2%. The ceramics have been pre-treated with hydrofluoric acid 9.7% for 90 seconds, rinsed, put in a ultrasonic bath with alcohol for five minutes and silanized. After the single veneer has been tried in,it is re-etched for 60 seconds with phosphoric acid 37%, rinsed with tap water and resilanited. Using this method, the bond strength of the ceramic increases approximately 50% over simple silanation.9

The hydrofluoric acid eliminates the superficial micro-fractures and enhances the mechanical properties of the ceramic as it allows a deeper penetration for the bonding agent.

The teeth are treated with 37% phosphoric acid (30 seconds on enamel),10-11 thouroughly rinsed with water for 30 seconds12 and bonding agent (Optibond Solo Plus, Kerr) is then layered both on tooth and the ceramic with a Microbrush rubbing for 30 seconds while thinning of the adhesive with lightly blowing oil-free air.

Luteing cement is then placed on the ceramic and the veneers placed on the teeth delicately pressed to allow the excess resin to flow out. After cleaning the excess, we light c
ure for 60 seconds on each side simultaneously in order to prevent undesired thickness of the adhesive layer.13 Further polymerization is done under glycerine to eliminate oxygen from the surface (oxygen inhibits the polymerization of resins).

The final restoration is then polished with rubbers (Brown and Green, Shofu) and then with brushes (Occlubrush, Have Neos) (Fig. 10).

The veneers were cemented one at a time. I find this the easiest way to control the entire procedure, as I don’t risk splinting the teeth together with composite or displacing the veneers. Once the cement is set, it is extremely difficult to remove the excess

After the veneers had been cemented and polished, the rubber dam is removed and the occlusion checked. The veneers act just like teeth, so they must play an active role in incisal guidance (the occlusal scheme is normal and correct).

DISCUSSION

It has been demonstrated that if the removed enamel layer is reconstructed with feldspatic porcelain veneers, the tooth entirely regains the structural flexibility of a natural tooth.14 In fact, the tooth is further reinforced with a variable resistance of 100% to 120%. When veneering with composite resin, the resistance to stress is consideralbly lower values (?80-90%).15

Tissue response to the presence of feldspatic porcelain veneers is optimal:16-17 as the presence of bacterial colonisation on a polished porcelain surface is minimal compared to that of a composite resin surface.

Porcelain bio-compatibility is confirmed by the absence of cytotoxicity in vitro, and cases reporting bio-compatibility problems linked to porcelain are very rare. There are no reports of known toxic effects of breakdown products of dental porcelain.18

The use of bond techniques with porcelain gives an excellent fracture resistance, when compared to that of porcelain fused to metal crowns.11-19 The translucency of the porcelain gives a natural effect the restoration and the clinician can regain form and colour of the tooth that were esthetically compromised.20

The only disadvantage in this technique is that it is operator-sensitive and requires a skilled dental technician. Following an exacting protocole can have a significant influence on the final restoration.21,22,23

It is very important that the technician’s attention during layering work, in particular, during porcelain preparation, leaves few surface gaps on the internal and external aspects of the porcelain.2 The advantage of the technique I have explained is the long-term esthetics and optimal restoration bio-compatibility.25,26,27

The long-term success rate of porcelain veneering has been reported in the literature to be: 98.8% at 6 years (83 veneers at 21 pz),28 89% at 5 years for undergraduate students (62 veneers on 29 patients).23

Conclusion

As the population of all ages has greater esthetic demands in order to prevent the high incidents of dental fractures, the clinician must have a clear understanding of treatment materials and options.

The goal of modern esthetic dentistry is to achieve the best possible results with minimal loss of tooth structure giving a patient a good looking, long-lasting result without damaging the integrity of their teeth.

Each time, we grind the tooth, we leave permanent damage. The use of ultra-thin veneers, (whenever possible), gives our patients the possibility of enhancing esthetics without seriously damaging their teeth. Furthermore, if something happens to the porcelain addition (ie. fractures or etc.) or if the patient doesn’t like the final esthetics, there is the possibility to remove the veneer and leave the teeth as they were before the treatment.

The final result of this case appears in harmony with her smile and face (Figs. 11, 12 & 13). It illustrates that when a smile has to be redesigned, the clinician must have the ability to evaluate the entire composition of the face.

Dr. Gregory P.M. Brambilla maintains a private practice in Milan, Italy. He is an international member of the Canadian Academy for Esthetic Dentistry. www.CAED.ca

Oral Health welcomes this original article.

REFERENCES

1.A Reis, et al. Reattachment of Fractured Teeth: A Review of Literature Regarding Techniques and Materials. Op Dent, 2004; 29(2): 226-233

2.P Magne, et al. Wear of enamel and veneering ceramics after laboratory and chairside finishing procedures. J Prosthet Dent, 1999; 82 (6): 669-79

3.SS Atsu, et al. Age-related changes in tooth enamel as measured by electron microscopy: implications for porcelain laminate veneers. J Prosthet Dent. 2005 Oct;94(4):336-41.

4.P Magne, et al. Design optimization and evolution of bonded ceramics for the anterior dentition: a finite-element analysis. Quintessence Int. 1999 Oct;30(10):661-72.

5.J Castelnuovo, et al. Fracture load and mode of failure of ceramic veneers with different preparations.

6.J Prosthet Dent. 2000 Feb;83(2):171-80.

7.M Ferrari, et al. Measurement of enamel thickness in relation to reduction for etched laminate veneers. Int. J. Period. Rest. Dent., 1992; 12 (5): 407-413

8.GP Cherukara, et al. Dentin exposure in tooth preparations for porcelain veneers: a pilot study. J Prosthet Dent. 2005 Nov;94(5):414-20.

9.AH Tjan , et al. Microleakage patterns of porcelain and castable ceramic laminate veneers. J Prosthet Dent. 1989 Mar;61(3):276-82.

10.YE Aboush. Removing saliva contamination from porcelain veneers before bonding. J Prosthet Dent 1998; 80(6):649-53

11.M Hashimoto, et al. Over-etching effects on micro-tensile bond strength and failure patterns for two dentin bonding agents. J Dent, 2002; 30: 99-105

12.AM Diaz-Arnold, et al. Current status of luting agents for fixed prosthodontics. J Prosthet Dent 1999; 81 (2): 135-41

13.EC Sung, et al. Effect of irrigating solutions on dentin bonding agents and restorative shear bond strength. J Prosthet Dent, 2002; 87 (6): 628-632

14.FA Rueggeberg, et al. Effect of light intensity and exposure duration on cure resin composite. Op Dent, 1994; 19(1): 26-32

15.P Magne, WH Douglas. Cumulative effects of successive restorative procedures on anterior crown flexure: intact versus veneered incisors. Quintessence Int 2000 Jan; 31:5-18

16.ES Reeh, GK Ross. Tooth stiffness with composite veneers: a strain gauge and finite element evaluation. Dent Mater, 1994;10 (4):247-252

17.G Rapelli et al. Restoration of antelior teeth with indirect composite partial coverage crowns: A clinical report. J Prosthet Dent, 2004; 92 (6): 519-922.

18.K. Malament. “EAED Closed meeting in Capri, 2003”

19.G Sjogren, et al. Cytotoxicity of dental alloys, metals, and ceramic assessed by Millipore filter, agar overlay, and MTT test. J Prost Dent, 2000; 84 (2): 229-236.

20.E Kao, WM Johnston. Fracture incidence on debonding of orthodontic brackets from porcelain veneer laminates. J Prosthet Dent 1999;66:631-7.

21.R Permann et al. Bonded porcelain laminates – an alternative to anterior porcelain crowns. Stomatol, 1989; 86 (4): 197-206

22.HY Chen, et al. Effects of surface finish and fatigue testing on the fracture strength of CAD-CAM and pressed ceramic crowns. J Prosthet Dent 1999;82:468-75

23.JR Kelly. Clinically relevant approach to failure testing of all-ceramic restorations. J Prosthet Dent 1999;81:652-61.

24.E Murphy et al. Retrospective study on the performance fo porcelain laminate veneers delivered by undergraduate dental students. Eur J Prosthodont Restor Dent. 2005; 13(1): 38-43

25.W Oh, et al. Factors affecting enamel and ceramic wear: a literature review. J Prosthet Dent, 2002; 87 (4): 451-459

26.M Peumans et al. Porcelain veneers: a review of the literature. J Dent 2000 Mar; 28 (3): 163-77

27.L Anglis. To place provisional or not – that is the question. Gen Dent 1999 Mar-Apr; 47 (2):192-4

28.A Attia, M Kern. Fracture strengh of all-ceramic crowns luted using two bonding methods.J Pro
sthet Dent, 2004; 91 (3): 247-252

29.M Fradeani. Six-year follow-up with Empress veneers. Int J Periodont Rest Dent, 1998; 18 (3): 217-225


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