Perfectly Prepped: 7 Reasons to Open Interproximal Contacts in Preparation for Porcelain Veneers

Maximize tooth preservation with a minimally invasive approach to open interproximal contacts in preparation for porcelain veneers. Keep reading to learn when to open interproximal contacts to create long-lasting veneers while maintaining tooth structure and maximum functionality.

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(Read time 5-7 minutes)

Interproximal contact - to break, or not break thru the contact, that is the question.

Whether it is nobler to maintain the proximal contact to minimize tooth removal, or to barrel thru the contacts can be a difficult decision for the restorative dentist when prepping teeth for porcelain veneers. Ideally, to maximize tooth preservation, our preparation techniques will maintain as much tooth structure as possible, while creating space for ideally contoured porcelain restorations. 

When Should You Choose to Open Interproximal Contacts?

Figure 1
This photographic image (fig 1) is indicative of minimally invasive veneer preparations of the patient’s maxillary anterior teeth. Because there was existing wear on the incisal edges, very little, to no tooth structure was removed at the incisal edge. 0.3 mm to 0.5 mm of enamel was removed over the facial surfaces of the teeth to provide adequate space for the restorative ceramic material.

 Note that the preparation margins are supragingival (above the gum line) and the proximal contacts of the natural teeth have been preserved by placing the margins facial to those contacts. While potentially more technically demanding for both clinician and laboratory technician, the desire to maintain tooth structure for the long-term health of the teeth is satisfied.

 Also, and potentially equally important and relevant, the preparation is 100% in enamel, providing the best opportunity for optimal adhesion. Provided that the patient’s occlusion and parafunctional habits are managed appropriately, we would expect the porcelain veneers bonded exclusively to enamel, would maintain for many, many years, perhaps even decades.

There are times however, when for esthetic or functional reasons, the clinician needs to be more aggressive in their preparation design.

One of the most important considerations in porcelain veneer preparation design is whether to leave the proximal contacts intact, or to prepare thru the contacts. There are multiple reasons, in my opinion, why the dentist should choose to open proximal contacts of the teeth and bring the restorative margin to the lingual, or palatal surfaces. The reasons listed below are what I believe constitute the most common rationale for opening interproximal contacts:
  • Closing diastemas
  • Heavy stain on natural teeth
  • Rotated teeth
  • Reduced enamel for bonding
  • Canted or angled midline 
  • Laboratory dictates
  • Dark Teeth
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1. Closing Diastemas

The challenge when closing diastema’s is if we leave the proximal margin facial to, or at the contact point to the adjacent tooth or veneer, the new contact point will need to be facial to its normal position. Figure 2 below shows the proximal margin at the interproximal contact position. The yellow veneer illustration demonstrates how the proximal contact then is pushed facial of the normal contact point.

Figure 3 shows that if the preparation margin extends to the lingual, more ideal contours of the veneer can be realized.
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Two negative consequences occur from the proximal contact facial to normal; 1) the line angles will be pushed outward making the tooth look wider, and more ‘boxy’ than normal tooth shape, and 2) Invariably, a food trap develops palatal to the contact because the laboratory is unable to create proper tooth contour.

Essentially, the veneer material is cantilevered into the contact zone, and without the palatal support, the technician is not able to create proper tooth contour. If the veneer preparation margin extends to the lingual, more ideal contours of the veneer can be realized, providing for improved esthetics, and cleanliness of the veneer, as appropriate proximal contact contours and position can be created by the ceramist.
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2. Overlapped & Rotated teeth

Figure 4, Figure 5, and Figure 6
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Orthodontic camouflaging with cosmetic dentistry can be especially challenging. When veneering teeth, especially with porcelain, I have found that the ceramist is able to create much more esthetic restorations when proximal contacts are opened with crowded dentitions and overlapped teeth. The photographs above (figure 4-6) demonstrate a case of mild overlapping for the maxillary anteriors that was cosmetically improved with the porcelain veneers.
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This second clinical case demonstrates more significant crowding of the lower anteriors. Note the aggressive interproximal reduction of the rotated lower incisor to allow the ceramist to create ‘straight’ appearing teeth in this cosmetic reconstruction (figure 7-10).
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3. Canted or Angled Midline

Midline cants, or angled midlines are fairly common in the esthetic cases that we treat. The midline contact must be opened, and the proximal margins placed to the palatal, on cases with canted, or angled midlines. It is also important that all other angled or canted contacts be opened on teeth that are treated, or adjacent to the teeth being restored.

Opening the contacts allows the ceramist to 1) upright the contacts and make the contacts parallel to the face, and 2) create appropriate tooth proportions and symmetry between the teeth. The following illustrations (figure 11-17) and the image slides above demonstrate the restorative outcome with palatal margin placement.

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4. Dark Teeth

It’s absolutely critical to hide all margins when veneering dark teeth. Visible exposed margins can easily turn a successful case into a complete failure if the patient is able to see any dark tooth structure beyond the veneer finish line. Adequate tooth reduction is critical as well in order to provide the ceramist with space for creating the veneers (figure 18 and 19).
Sub-opaquing of the tooth preparations prior to impression taking can be helpful for the ceramist when creating the veneers (figure 20-25). The final margins of the preparations must be maintained in tooth structure however for optimal bond strength, so it is critical that the preparation margins be hidden sub-gingival, and beyond the interproximal contacts, and finished on natural tooth structure.

For more on opaquing to bond dark teeth, check out our blog post, Blocking Out the Dark Tooth, or our complete course on DOT, Masking the Dark Tooth with Direct Resin Bonding.
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5. Patients That Have Heavy Stains

In my experience, patients that have excessive extrinsic staining on their natural teeth are likely to get staining on their restorative margin, regardless of the polish that our laboratory technicians are able to create on the ceramic restorations.

The stain on porcelain is generally easily removed, however, when the staining occurs at the margin between the porcelain and tooth interface, those stains can be difficult, if not impossible, to completely remove.
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6. Reduced Enamel

As discussed earlier in this blog, it is well documented that bonding to enamel provides the best long-term success for restorative survival. It is understood that while we are able to create a strong bond to dentin, the bond strength of our restorative materials is inferior to the bond strength to enamel, and the bond strength to dentin degrades over a relatively short period of time.

In cases where I am still attempting to be conservative in my preparation design, I might choose to do a facial “wrap” of the tooth to provide more retentive form to the veneer.

 I like to tell the patients that in cases like these, the veneer will ‘hug’ the sides of the teeth. The interproximal wrap helps maintain the bonded restoration by increasing the amount of bonded tooth surface and by introducing retentive form in the restoration. The following clinical photographs demonstrate the ‘wrap veneer’ (Figure 26-28).
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7. Laboratory Preference

Your ceramist may note potential challenges related to the tooth positioning or tooth size that you may not fully appreciate. Opening the interproximal contacts could improve the esthetic outcome when teeth are rotated or the positioning of a tooth or teeth are not ideal. Opening the contacts gives the ceramist more flexibility with tooth shape and proportions when creating the porcelain restorations.

Porcelain veneer restorations are an important tool in the cosmetic and restorative dentist’s tool box. Preparation designs however are exacting and precise to minimize tooth structure removal and provide biologically compatible, esthetic and functional restorations.

With conservative preparations, we are able to maintain as much enamel as possible, thereby providing the maximum long-term adhesion as possible for the porcelain veneers.

I feel strongly that positive collaboration between the dentist and the laboratory technician is critical for ultimate esthetics, and function, with all cosmetic cases, but most importantly with porcelain veneer cases due to the complexity of tooth preparation design.
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Thanks for Reading!

If you would like more information on porcelain veneer preparation design, check out our courses at dothandson.com.

Yours for better dentistry,

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Dennis Hartlieb, DDS, AAACD

DOT Founder

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