Interview

Supragingival Dentistry: Easier and Healthier Restorative Care

Dentistry Today March 1, 201016 Mins read3k Views

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Figure 1. Inflammation and unsightly margins typically observed with subgingival margins on existing maxillary PFM crowns.

Figure 2. Preoperative view before veneer preparation. The young male patient was unhappy with aesthetics of his teeth.

Figure 3. Immediately after conservative equagingival tooth preparation, discolored tooth No. 9 was prepared 0.5 mm subgingival for aesthetic purposes.

Figure 4. Cemented VenusCeram (Heraeus) veneers with indistinguishable margins.

Figure 5. The patient was very happy with final results, especially with the minimally invasive nature of restorations.

Figure 6. Same tooth No. 29 postoperative view of the restoration. Observe the excellent blending and unaffected gingival health as compared to traditional PFM crown on the molar.

Figure 7. Male patient with deep caries on distal margin of tooth No. 29, before margin elevation.

Figure 8. Final preparation after margin elevation using a bonded composite.

Figure 9. Observe a 6-year postoperative x-ray on the same male patient (as Figures 6 to 8), showing the excellent result on both first maxillary and mandibular bicuspids, after margin elevation.

In this interview with our editor-in-chief, Dr. Damon Adams, Dr. Ruiz explains the importance of understanding and using new materials correctly. He will share important clinical tips, explaining the benefits of what he likes to call “supragingival dentistry,” specifically for indirect restorations like veneers, onlays, and all-ceramic crowns.

Dr. Ruiz is the founder and director of the Los Angeles Institute of Aesthetic Dentistry, where he teaches workshops on adhesive and aesthetic dentistry, and occlusion. He is past director of the University of Southern California’s Aesthetic Dentistry Continuum (from 2004 to 2009) and associate instructor at Dr. Gordon J. Christensen’s PCC in Utah. He has had a full-time private practice in the Studio District of Los Angeles for more than 18 years.

INTRODUCTION
Advances in dental materials have truly changed the way we practice dentistry. New dental adhesives, restorative composites, cements, impression materials, porcelain systems, as well as digital impression and CAD/CAM technology are helping make amazing changes in the way that we practice. Some new materials may present certain challenges and require learning new techniques. Sometimes the changes can seem radical and a bit scary, especially if these new materials are used incorrectly and negative results occur. However, when used properly, most of these new materials and techniques are revolutionizing dentistry, resulting in many benefits to the patient and doctor alike.

Dr. Adams: You have previously stated that using nonmetal indirect restorations with supragingival techniques is easier and more predictable than doing traditional restorations such as PFMs with subgingival margins. Is that correct?
Dr. Ruiz: I am convinced that nonmetal supragingival dentistry is easier, more predictable, and healthier for our patients than traditional dentistry. Knowing that the statement is controversial, let’s look at the evidence. Dental laboratories report that gold onlays are rarely used; the reason is that they exhibit unnatural aesthetics and therefore patients refuse them. Let’s also think about the most used indirect restoration in dentistry, the PFM crown, which requires subgingival margins when traditionally designed. Every dental school and textbook teaches that a crucial step in the technique of these restorations is the placement of the restorative margins subgingivally. This is necessary to hide an unaesthetic margin. The increase in difficulty, potential complications, and unpredictability this routine procedure brings to the table is significant. It starts with a difficult preparation, with the need to place a preparation margin subgingivally, yet in an atraumatic style.

Dr. Adams: How does the concept of supragingival dentistry relate to the clinical realities around tissue control issues and the proper use of impression materials?
Dr. Ruiz: When done correctly, traditional subgingival preparations require that we first prepare an initial equagingival preparation margin. Then retraction cord is placed in order to expose subgingival tooth structure, and the margin is placed subgingivally. After this difficult procedure, a second, smaller cord must be placed in order to take a proper impression of the subgingival margin. This procedure, along with taking an excellent impression, is technically very challenging; in fact, it is one of the most difficult and unsuccessful procedures in dentistry, as dental technicians around the country can attest to. In his lectures, Dr. Christensen found that interviewed dental laboratory owners report that as many as 90% of the impressions received have less-than-adequate margin registration/definition.

Of course, because impressions are so frustrating, dental manufacturers continue to improve impression materials. For example, the highly hydrophilic Aquasil Extra (DENTSPLY Caulk) presents just one material that has demonstrated an important improvement in the vinyl polysiloxane (VPS) category, allowing good impressions even in wet margins. Other VPS materials like Panasil (Kettenbach) or FlexiTime (Heraeus Kulzer) have also made significant improvements in this area. Other manufacturers are now providing other solutions to help make taking impressions easier, more predictable, and accurate: digital impression systems like the iTero (Cadent) and Lava C.O.S. (3M ESPE) are a couple of current examples.

Nevertheless, even with all of these advancements, subgingival margins are still difficult to prepare and predictably reproduce outside of the mouth.

Dr. Adams: So that brings us back to the supragingival alternative, doesn’t it?
Dr. Ruiz: Yes, in my opinion, the best solution is to implement the use of supragingival dentistry techniques whenever possible. Supragingival dentistry is a style of dentistry which uses modern materials and techniques such as enamel preservation and margin elevation. It also involves the proper use of the contact lens effect which employs an important characteristic of many ceramic systems (nonmetal restorations)─translucency. This allows us to intentionally keep restorative margins supragingival while still achieving excellent aesthetic results. This in turn helps to make dentistry truly easier, more predictable, aesthetic, and healthier for the patient.

Dr. Adams: Can you address the issue of translucency found in all-ceramics versus traditional metal-ceramics in a bit more detail?
Dr. Ruiz: Sure! Translucency allows for an easier blend of the restoration to the tooth because it allows some light to go through into the tooth and root. Teeth are like fiber-optic rods, in that when light hits the crown it goes down the root. We also know that some ceramic systems’ (nonmetal) restorative materials are more translucent than others by their very nature, based on the materials from which they are made and how they are manufactured.

Traditional metal-ceramic restorations are completely opaque, thus obstructing light from entering into the crown. This makes the tooth and root dark, creating a grey margin appearance, forcing clinicians to submerge the margins (Figure 1). This in turn can cause darkness in the gingival tissue zone adjacent to the margin, especially when the patient has thinner, more “translucent” tissue. Nonmetal restorations permit light to go through into the tooth and root, thus the shadowing effect of the metal coping is eliminated or diminished and marginal blending is improved, thus allowing for the more coronal placement of the margin. Just imagine, by using nonmetal restorations correctly, we can leave margins either supragingival in the nonaesthetic zone, or equagingival in the aesthetic zone. This makes taking impressions much more simple and predictable!

Dr. Adams: You also said that modern ceramic restorative materials are available in various translucencies. Clinically speaking, how do you decide which material should be used in a particular case?
Dr. Ruiz: This a great question! As previously discussed, one of the most important characteristics of all nonmetal restorations is translucency. Translucency allows for an easier blend of the restoration margin to the tooth, because it allows some light to go through into the tooth. Translucency does vary dramatically depending on the porcelain system. Feldspathic porcelains, and pressed/ layered porcelains, tend to be very translucent. Layered and pressed feldspathic porcelain can be one of the most aesthetic options available, and for that reason it is an ideal material choice for porcelain veneers. Also, these materials have some great advantages when used for nonmetal onlays or inlay/onlays. Crowns using alumina and zirconia copings are always more opaque, yet can be made to be translucent using layering porcelains…just to a lower degree of translucency. And then you have lithium disilicate, a very promising material that has historically lain kind of in the middle. Recently, it has been further developed to include several different levels of translucency/ opacity. For example, it is now available in a high translucency (HT) version (e.max HT [Ivoclar Vivadent]), which can be used for very thin 0.3 mm veneers. It can also be used as a monolithic restoration, giving it strength and acceptable aesthetics. It is available as a pressable ingot option, or as block, for the E4D (D4D) and E4D LabWorks CAD/CAM system, which is the version I am currently using. It is also available for the CEREC (Sirona) CAD/CAM in-office and CEREC InLab systems. Lithium disilicate is a very promising material. We need to keep in mind that usually, the more translucent the material, the weaker it is, and vice versa; this is very important when choosing a cementation material and technique.

The great marginal blend or contact lens effect that can be achieved with feldspathic porcelain allows for maximum aesthetics, minimal preparation, and a more coronal placement of the margin. Manufacturers have made great progress on feldspathic porcelains, pressed and layered. First of all, compared to the materials in this category that were manufactured years ago, these current materials are kinder to the opposing tooth structure because they are made out of very small particles and are baked at low fusing temperatures, making them softer and gentler. Also a wide range of translucency and opacities have been introduced and improved, making them incredibly aesthetic. Most of my veneers and onlays are made out of the VenusCeram pressed and layered system (Heraeus), but I have had great results with other excellent materials, like Creation (Jensen Industries), Finesse (DENTSPLY Ceramco), and others.

Properly made, layered and when there is enough space, pressed cut back and then layered porcelain, can have different shades and opacities throughout the restoration, making it polychromatic and allowing it to naturally mimic a tooth really well.

Keep in mind though, if we use this restorative material with subgingival margins, we will really miss all the benefits of supragingival dentistry. In addition, we will make impression and cementation much more difficult than it has to be. In the highly aesthetic anterior zone, through the first bicuspids, it is desirable to leave the preparation margins of feldspathic porcelain veneers and porcelain jacket crowns from approximately 0.25 mm above the gingiva crest to equal to the gingival crest. Excellent results can be achieved with tooth preserving veneer preparations, and slightly supra-gingival or equigingival margins, as long as proper translucency and good margin blend is achieved, even if the restoration margin is visible as seen on Figures 2 to 5.

In order to achieve a good blend, one must make sure that the color of the tooth and the color of the restoration is not dramatically different. For this reason, it is best to complete the bleaching of the teeth before beginning any aesthetic restorative work. Professional home whitening with custom trays using a product such as Opalescence (Ultradent Products) is very effective. Although Opalescence is a personal preference of mine, there are many other excellent whitening materials and techniques available. I use translucent pressed ceramics for porcelain onlays because the cavo-margin may be placed on the middle of the tooth. Margin blending in the middle of the tooth is difficult, but it is crucial. In these situations, it is indispensable to use the restorative material correctly to achieve good marginal blend. I like to use a “hybrid onlay” made from a very translucent pressed ingot, such as VenusCeram, and then layered porcelain to achieve good marginal blend and aesthetics. Excellent marginal blend can be achived using this technique as seen in Figure 6.

New, super-strong nonmetal coping and framework materials have become available and they have been very well received by the profession. Personally, I have had excellent success with zirconia crowns, such as Lava [3M ESPE], Cercon [DENSTPLY Caulk], and Aadva [GC America]), etc. This material’s strength allows an experienced dental technician to design a very thin coping in the aesthetic areas for maximized translucency and aesthetics. It also allows the technician to design a thicker coping in the stress-bearing areas for strength. When the copings are properly designed, and a nonopacious veneering porcelain is used, one can realize natural translucency. In addition, one can safely place the margin 0.5 mm supragingivally in nonaesthetic areas and at gingival level in the aesthetic zone. The ability to build in translucency will avoid the traditional grey appearance of the margins as seen with many PFM crowns. This permits us to do supragingival dentistry while still being able to achieve acceptable aesthetic results.

Failures with zirconia have been associated with the chipping and breaking of the layering porcelain layer. This is often caused by poor coping design that does not include proper support for the overlying porcelain. As previously stated, new materials require that we learn how to use them correctly. There is a learning curve for both the dentists and the dental laboratory technicians.

Dr. Adams: Knowing how critical that proper adhesion is to success with these nonmetal materials, please tell us how you decide which bonding system to use, and what’s new in regards to dental adhesives?
Dr. Ruiz: There is no doubt that predictable clinical success with bonding systems is indispensable for the overall success of nonmetal restorations. There is a tremendous amount of controversy and passion about this subject. Many academics and educators have stated that the fourth generation, total-etch bonding systems like OptiBond FL (Kerr) and Scotchbond Multi-Purpose (3M ESPE) are state-of-the-art, due to their long track records, very high bond strengths, and excellent marginal sealing abilities. All of the above are very important characteristics, and undoubtedly these bonding systems are excellent, when used by experienced clinicians who are good at using them. The problem is that sometimes these advocates of total-etch techniques forget the very real problem of postoperative sensitivity and technique complexity, which can be a problem with these bonding systems. There is no more frustrating problem in dentistry than when we perform a beautiful direct or indirect tooth color bonded restoration, and weeks later, the patient continues to complain of postoperative sensitivity. Clinical experience has shown that although total-etch bonding systems can be predictable, if used meticulously, they are more technique-sensitive than the self-etch systems.

With total-etch bonding systems, a minor variation in moisture will result in decreased bond strength to dentin and postoperative sensitivity. More than 4,000 dentists surveyed by CLINICIANS REPORT cited a 4-fold increase in severe postoperative sensitivity when using total-etch bonding systems, compared to those using self-etch bonding systems. The results underscore the clinical reality; achieving that perfect moisture control and perfect dentin tubule seal can be difficult. It is very important to point out that the literature shows that operator skill and choice of material is very important for success.

Dr. Adams: Everyone seems so concerned about bond strengths; however, there is more to adhesive success than just that, right?
Dr. Ruiz: Yes, many clinicians incorrectly look at bond strength as the primary quality of a bonding system. However, from a clinician’s perspective, a good bonding system must have 4 important characteristics: (1) it must provide excellent adhesion and seal, (2) it must be durable, (3) it must be associated with low postoperative sensitivity, and (4) it must be easy to use. Some self-etch bonding systems fulfill all of these requirements, especially the 2-bottle sixth-generation types like Clearfil SE Bond, Clearfil SE Protect (both from Kuraray). All-in-one bottle self-etch seventh-generation systems are rapidly improving; Futurabond (VOCO) is a great example. Self-etch bonding systems have proven themselves to be an excellent choice. There is plenty of literature evidence showing that bond strength to dentin is equally as high with self-etch, and there is also evidence that the bond durability to dentin may even be better for self-etch versus total etch.

In addition, self-etch bonding systems are considered user friendly because they are not as moisture sensitive. This also decreases the chances of postoperative sensitivity.

The primary drawback of self-etch systems is their inability to properly etch enamel, especially uncut enamel, leading to less-than-adequate seal at the margins and staining. This problem can easily be eliminated by a short selective etching of the enamel using phosphoric acid for 10 seconds and then applying the self-etch system as manufacturers recommend. For many years I have been using self-etch bonding systems for all my restoration needs–even porcelain veneers—but I will always etch the enamel with phosphoric acid. This gives me the best of both worlds: excellent dentin bond with minimum postoperative sensitivity and excellent enamel bond with the help of the phosphoric acid etch. It works!

Dr. Adams: Jose-Luis, could you remind us what the advantages are in keeping restoration margins supragingival as related to cementation, and what is your take on newer cement materials and techniques?
Dr. Ruiz: Yes, Damon, it is a good idea to remember that the cementation protocol varies widely from one material to the other. It depends on the strength of the restorative material, the location of the gingival cavo-margin and the aesthetic needs. Feldspathic porcelain, layered and pressed, must be cemented with resin cement because this material is intrinsically weak.

Resin cements have no tolerance for contamination, and for this reason we should avoid them as much as possible when placing our margins subgingivally. This is because it is very difficult to perfectly achieve isolation from fluids during cementation, thus leading to contamination of the cement/bond, early failure of our restoration, and/or chronic tooth sensitivity. The routine placement of subgingival margins for porcelain veneers or onlays is an excellent example of how we carry unnecessary old habits from old materials and techniques, which lead to self-complication and frustration with new materials.

In the area of resin cements, some important advancements have been made. Highly filled cements with even smaller particle size that use nanotechnology are now on the market. These have better handling characteristics with improved thixotropic properties. I prefer to use light-cured, translucent cements for veneers, because of color stability and better aesthetic blending. Calibra (DENSTPLY Caulk) and RelyX Veneer (3M ESPE) are my usual choices, but there are other excellent choices like Variolink Veneer (Ivoclar Vivadent) or NX3 Nexus Third Generation (Kerr).

I like to use dual-cured cements for onlays because I am still concerned that the light may not penetrate deep under 2 or 3 mm of porcelain, as the literature attests. My usual preference here is Clearfil Aesthetic Cement and DC bond (Kuraray) because of it has a nice working viscosity, excellent translucency, and it is a dual-cured self-etch bonding system with low postoperative sensitivity. I have also had excellent results using dual-cured NX3 with OptiBond All-In-One bond (Kerr) and MultiLink (Ivoclar Vivadent), both also self-etch systems. Self-adhesive resin cements like RelyX Unicem (3M ESPE), Maxcem Elite (Kerr), G-Cem (GC America), BisCem (BISCO), SpeedCEM (Ivoclar Vivadent), MonoCem (Shofu), and Breeze (Pentron Clinical Technologies), to name a few, are becoming very popular because clinicians find them easy to use with very few postoperative sensitivity problems. At this time, I only use them for onlays with mechanical retention or as a second choice for supragingival zirconia crowns with unretentive preparations (to improve retention), or occasionally for post cementation. Although they are easy to use, simplicity has its price: they have lower bond strength, poorer color stability, and, because they are resin cement, they require perfect isolation with no contamination, or failures will occur.

Although resin cements continue to improve and become more popular, resin-modified glass ionomers (RMGI) cements, like FujiCem (GC America) or RelyX Luting Plus (3M ESPE) are incredibly useful and are my first choice when using zirconia all-ceramic crowns. In some cases with thick lithium disilicate crowns, I use these cements as well. Unlike resin cements, RMGIs are more forgiving to moisture and contamination, making them an ideal choice when the crown margins are subgingival, such as the case with many PFMs.

Finally, supragingival dentistry makes cleaning cement much easier because you can see and access the margins, thus eliminating the common problem of leaving small amounts of cement subgingivally.

Dr. Adams: You have made the point that keeping the margins supragingival is advantageous, but sometimes caries/fractures/ old restorations extend subgingivally. How do you suggest that these situations be handled?
Dr. Ruiz: You are totally right. Sometimes we have to deal with subgingival margins, and to me there are 2 ways to handle them. One, if the margin is subgingival all around, either because the subgingival caries are almost all around the tooth, which is rare, or when replacing a PFM crown with already subgingival margins; then I will choose to place an all-ceramic crown, most likely a zirconia. This will allow me to cement the crown with an RMGI cement like FujiCem, which is much more forgiving with moisture or contamination, as previously explained. The most common situation that I face clinically is a mesial or distal margin which is below the gingiva due to caries, an old amalgam, or other restoration. In these situations, using a toffelmire matrix band, I will elevate the margin to be 1.0 mm above the gingiva with either RMGI restorative materials like Fiji Filling LC (GC America) or Ketac Nano (3M ESPE); or I will elevate the margin similar to doing a Class II composite using a bonding system like Futurabond (VOCO), then a small layer of the highly-filled (80%) Grandio Flow (VOCO) and then a layer of Grandio (VOCO). After elevating the margin, I will refine and finish my onlay preparation which will now have all supragingival margins. Of course, impression and cementation of this restoration will be a cinch (Figures 6 to 9). There is strong evidence in the literature pointing out that subgingival margins perform better with RMGI restorative material due to the release of fluoride, thereby decreasing the chance of secondary caries.

Dr. Adams: Can you please comment briefly with regard to the life expectancy and failures with nonmetal restorations?
Dr. Ruiz: That sure is an important question. For the past 10 years, I have been doing nonmetal indirect restorations almost exclusively. In addition with regard to direct restorations, I haven’t done an amalgam in more than 15 years, including in second molars. These days, I rarely prepare a full crown of any type, and quite honestly, I can count with my fingers how many people have requested gold restorations of any type. So, what is the longevity of these restorations in my practice? My personal experience has been as a clinician practicing in the same place for almost 18 years. This has allowed me to witness my own successes and failures over quite some time. When I compare the problems and failures I had with traditional mechanically retained, subgingival dentistry, to the past 10 years with nonmetal supragingival dentistry, my life is easier with less complications and fewer failures. And although I have published a retrospective review of my cases with the assistance of Dr. Gordon Christensen and other clinicians, showing overwhelming success, it is of greater importance to look at what the literature shows. In the anterior area of the mouth, the profession is quite comfortable with all-ceramic restorations, and the literature is replete with success with these restorations. In the posterior area of the mouth, the results are less positive and conflicting; nevertheless, there is ample literature showing excellent long-term success with porcelain onlays at 8-plus years, when done correctly. How long do PFM crowns last? Some people have PFM crowns that have lasted 20 years or more, but looking at things from the realistic standpoint, PFM crowns in the United Span have an average lifespan of about 8 years, based on some insurance surveys. All-ceramic indirect restorations in the posterior area of the mouth should last as long, or longer, than PFM crowns, when we take in to consideration that they are also more repairable.

It is important to remember that the main reason porcelain restorations fail and break, especially in the posterior, is occlusion. Therefore, a good understanding of the 3 golden rules of occlusion is vital to success: equal contact, posterior disclusion, and an unobstructed envelope of function. In addition, proper occlusal adjustment techniques are imperative. Your readers may request a step-by-step short video on my occlusal adjustment technique via e-mail.

One final thing to remember is that one of the main advantages of nonmetal restorations, when done correctly, is that they can be designed to be more tooth conserving and supragingival, which means the periodontal health will be unaffected by the restorations. This is an important consideration when thinking about longevity. I always tell my patients that, in my experience, these restorations will likely last as long as a PFM crown, but because of the restoration’s noninvasive nature, their teeth will be better off, and will likely last longer than they would with more destructive traditional treatment options.

Dr. Adams: Jose-Luis, I want to sincerely thank you for taking the time to share your opinions, experiences, and knowledge with our readers. Your dedication to, and leadership within, the dental profession is commendable.

Dr. Ruiz graduated from Universidad National Autonoma de Mexico in 1997. Dr. Ruiz is the founder and director of the Los Angeles Institute of Aesthetic Dentistry, where he teaches workshops on adhesive and aesthetic dentistry, and occlusion. He is past director of the University of Southern California’s Aesthetic Dentistry Continuum (from 2004 to 2009), associate instructor at Dr. Gordon Christensen’s PCC in Utah. He has had a full-time private practice in the Studio District of Los Angeles for more than 18 years. Dr. Ruiz has published several research studies in the area of adhesive dentistry, many clinical articles, and lectures internationally. He has made numerous television appearances highlighting his aesthetic dental makeovers, including NBC’s Channel 4 News, ABC’s Vista LA, and Univision and Telemundo. He can be reached at drruizonline.com or via e-mail at ruiz@drruiz.com.

Disclosure: Dr. Ruiz reports no conflicts of interest.