Chapter 15 Direct Veneers
Direct composite bonding has been around since the 1970s. It has had an enormously beneficial impact, making it possible to improve a patient’s appearance via a very simple, straightforward technique without impression and a laboratory to make porcelain veneers. With composite, a better smile can be created for the patient very quickly and efficiently using a noninvasive technique. Dentists are able to dramatically change a patient’s appearance and thus improve self-image and boost confidence.
Essentially, the procedure is done in a single sitting by the dentist. Patients come in and within a matter of hours leave with their new look. It is a fairly predictable procedure because the esthetic dentist is in full control of the procedure. It also allows for modifications in the future, as it is possible to add to the composite for further improvement. Patients have the opportunity to influence the outcome as well. Their involvement in the treatment process makes them more likely to be satisfied with the final result.
The procedure for direct composite bonding has undergone an incredible evolution, along with an upgrade in materials that help create proper esthetic anatomy, characterization, hue, value, chroma, position, form, function, direction, and texture. It is now possible to improve a patient’s look predictably.
In the late 1970s macrofill composites were not very polishable, so dentists could not achieve as much of a shine as is possible today. These resins gave way to two classes of materials in the middle 1980s: the microfills, hybrid microfills and nanofills. The microfills are extremely polishable but stain over time. The nanofills did not evolve into successful products until after the 1990s.
In the 1990s, hybrids came into a fairly common use. These combine larger and smaller particles to fill the spaces between the resin filler material. With less resin material, there is less stainability. The hybrids are harder resulting from longer lasting surfaces.
Around the turn of the century, the nanohybrids were introduced. Extremely tiny particles fill in even smaller spaces and eliminate much of the resinous material. This makes the material stronger, more polishable, and less likely to stain. Today bonding is done with nanohybrids, sometimes including a very thin surface layer of microfills for even greater polishability.
In the 1980s patients were happy with rectangular white teeth. Today’s patients are much more educated, discerning, and demanding. They want their teeth to look very natural and want replacement teeth that cannot be differentiated from natural healthy teeth.
In the 1980s, only porcelain veneers could produce an acceptable result. Today, dentists can replicate the look of porcelain with composite, although its durability and polishability are not as good. Composite is not as natural in appearance as porcelain, but it has evolved to create a better immediate result. Composite normally requires some maintenance at least every 1 to 3 years to polish the surface or correct any chips that may have occurred.
The typical reason a patient requires the placement of direct composites in the anterior include normal wear and tear, occlusal disturbances, aggressive tooth brushing, or eating too much crunchy food. To create the proper look cosmetically, it must first be determined what has made such treatment necessary. It is important to evaluate the patient’s habits and normal function. This will reveal occlusal problems, perhaps abrasion, nutritional problems, erosion, or bruxism. The wear is evaluated to identify its cause, and then treatment possibilities and precautions are planned (Box 15-1). The goal is to avoid such wear in the future or at least minimize the threat of repetition. This involves evaluating what has happened to the individual’s teeth, and to the opposing dentition (e.g., the lower arch) to ensure that a better profile, shape, and position can be created for those teeth. Various modalities such as Invisalign (Align Technology, Inc., San Jose, California), bonding, or enameloplasty may be employed.
Box 15.1 Relating Function and esthetics
If the esthetic evaluation indicates that it is desirable to extend the patient’s central incisors by 2 mm in length incisally, it must be assessed whether this is possible. The outcome depends on functional, protrusive excursive, and lateral excursive movements. It may also be necessary to extend the coverage of the composite onto the tooth more to the lingual surface to create a stronger restoration, a night guard, and to evaluate the condition of the posterior teeth to rearrange the vertical dimension so it is possible to build up the anterior segment by 2 mm. This generally involves opening the bite in the posterior region by less than 2 mm.
To summarize, first evaluate the functional situation for both previous and current problems and then keep those situations in mind when planning treatment. Functional treatment planning is an essential part of the esthetic program. If esthetics and function are not addressed together, the case will fail.
If a patient has chipped, discolored, stained, underdeveloped, fractured, or worn teeth, it is possible to bond and repair specific areas to improve the condition. When addressing a chipped tooth, the chip restoration and veneering can be done at the same time. Discolored or stained teeth generally require a masking layer, an opaquer, placed first and then a buildup of the desired colors in layers.
Underdeveloped teeth, such as a peg lateral, are usually not color compromised. Generally, existing tooth structure and composite are used to build out a functional, larger, more true-to-life tooth in the space available. With orthodontically compromised teeth, orthodontic therapy can be done first or a buildup to create a thicker tooth to compensate for the malposition. Fractured and chipped teeth are treated similarly. Worn teeth are the result of parafunction, faulty occlusion, or loss of vertical dimension. It is essential to pay careful attention to how function and the desired esthetics relate, evaluate the condition on a mounted model using a face-bow.
Contraindications include limitations. One must be very aware of the limitations that prevent the opening of the bite for one reason or another. The best way to evaluate whether it is possible is to add some composite incrementally to the posterior dentition. A night guard also open a patient’s bite. Then the patient can determine if he or she is comfortable in that raised vertical position.
Contraindications to using direct composite bonding include gross loss of tooth structure where composite would not be strong enough. In these cases a porcelain, crown, or veneer may be more suitable. A grossly decayed, or brittle teeth or poor oral hygiene are also negative indicators. With poor hygiene it is difficult to maintain the margins, and decay will reoccur.
It is the author’s recommendation to use a 37% phosphoric acid−etch with a light-cured adhesive (fifth generation), specifically, OptiBond Solo (Kerr Corporation, Orange, California). Composite materials used for veneering include hybrid Point 4 (Kerr Corporation) available in various shades, including opaques. As a final layer, Herculite (Kerr Corporation) Enamel Light or Extra Light is placed. Obviously the material of choice depends on whether the adjacent and other teeth are light enough to match. The color is built up in a microhybrid used below a microfill. The actual color of the dentin is placed over that. At times translucency is required. Vitalescence (Ultradent Products, South Jordan, Utah) and Trans Smoke or Iridescent Blue shade are excellent.
The advantages of composite versus porcelain direct veneers include that they are the more conservative option, are noninvasive, give immediate results, involve no lab expense, and are more predictable because they are done chairside. They are less expensive for the patient than porcelain veneers. They are indicated over ceramic while the candidate is still developing, up to age 22 or 23 years. Composite veneers are reversible because the tooth structure does not need to be prepared.
All required maintenance is a disadvantage. Composites can stain, chip, and lose luster. They are also very technique sensitive; the dentist must be adept and very detail oriented to achieve a successful result. It is necessary to polish composites to establish a superficial layer that replicates the glaze of natural tooth structure. Polishing is also important to avoid future staining. Stain can accumulate in days or weeks from normal food intake. Patients are advised to not drink or eat anything that may stain the composite for about 2 days after treatment because the composite is slightly porous. However, microfill is not as porous as a hybrid. In addition, if one polishes well enough, it will diminish the chance of staining and dulling.
Patients who smoke, drink dark beverages (red wine and dark coffee), or eat highly staining foods are at greater risk for staining their direct composite veneers. Such habits must be evaluated, and patients advised to avoid and limit them as much possible. Patients should be made aware that the composites may need regular polishing or resurfacing.
Young adults are better candidates for direct composite bonding than they are for porcelain veneers because their teeth are still developing. The gingival margins can show once the teeth fully develop. Later, composites can be upgraded to porcelain veneers. Patients should be given the choice of a porcelain veneer or a composite direct veneer bonding and the rationale behind each choice, the advantages of each, and the cost.
When patients have had bonding in place for over 5 or 10 years, they may be ready for the porcelain upgrade, or they may choose resurfacing, the removal and reapplication of the composite in its entirety or partially.
Some of the other considerations are the natural look of porcelain, the invasiveness of the procedure, and finances. Porcelain best emulates enamel because it can recreate natural-appearing translucency more predictably than composite.
Porcelain veneers are a more invasive option because a certain space is necessary. Veneers usually require reduction, although ultimately it depends on the position of the teeth. In most cases, preparation is necessary to create retention or to break the contact between the interproximal teeth.
When looking at the financial considerations, there is a lab expense involved with porcelain and the price reflects that fee. The price of composite veneers is about 50% to 75% of the cost of porcelain veneers. In addition, porcelain veneers often last 15 to 20 years compared with only 8 to 10 years for composite bonding. Generally the gingival line recedes away from the gingival margins of the restoration, and as the gum recedes, the margins may stain, or black triangles can be created at the gingival embrasures.
Increased bond strengths are the major element that has made composites successful and predictable. These materials are also more polishable and are available in a wide range of shades. This is important considering patient desires to make teeth look as white as possible. Ten to 15 years ago, people were not as aware cosmetically and did not expect the esthetic results that can be achieved now. Today media hype and celebrities drive patients’ desire to get teeth super white. Shade, increased bond strength, and increased polishability are scientific elements that have advanced.
Research leads to a continuing upgrade in materials. With this dynamic evolution, there is always something new at conventions with regard to the sixth- and seventh-generation adhesives and better composites. Every decade has brought a quantum leap in technology, so composites are now easier to place, more convenient, stronger, and more esthetic.
Typically 34% to 37% phosphoric acid is used as an etchant. It is available from many manufacturers. Once the enamel and dentin have been prepared with phosphoric acid, dental bonding agents and restorative composite materials complete the process.
There are two major categories of composites and adhesive materials in dentistry. One is BIS-GMA, and the other is polyurethane. Fortunately for the dental profession, these materials interact seamlessly. Without knowing the chemistry of individual bonding agents and veneer composites, the dentist can feel secure in using any bonding agent with any composite. Manufacturers prefer that the dentist use the bonding agent and composite within the same system, but from a dentist’s perspective, if an adhesive from one manufacturer and a composite from another manufacturer seem to be more suitable, this is not a problem in terms of chemistry, longevity, or adhesion.
It is necessary to evaluate the impact of bonding on the face, not just on the actual appearance of the teeth. The entire face must be considered. This includes analyzing the shape of the lips and cheeks.
In analyzing the look of the face, it can be measured or visualized. For example, a patient may have a round or oval face. The treatment choice depends on what the patient wants. If the teeth look too flat and make the face look too round, the dentist can solve the problem by making the teeth appear a bit longer. If the patient’s face is too oval, the dentist can shorten the length of the teeth. If it appears that there is too much negative space at the buccal corridor in the posterior, the dentist can refurbish the smile by adding more tooth structure, thus plumping out the arch and creating a fuller, more youthful appearance.
The golden proportion relates to the anterior teeth as they progress toward the posterior. It is a specific ratio, 1.618 : 1. The two central incisors are larger than the corresponding laterals. The visual proportion of the centrals to the laterals is 1.618 : 1. The visual proportion of the laterals to the cuspids (viewed from the front) is 1.618 : 1. The visual proportion of the premolars and molars follows a similar ratio.
This proportion appears repeatedly in nature, and seems to have a very pleasing effect on the human eye, although it is not clearly understood why this is so. The effect occurs consistently, in dentistry and in other areas of esthetic harmony.
The hue is the actual color portrayed. The chroma is the saturation and richness of that specific color. The value is the degree of gray versus white. Usually the dentin imparts the hue and chroma, and the enamel layer imparts the value. If one has a high value, the teeth are white; if the value is low, the teeth are grayish or dark. Of the three, value is the one that is the most important, the one feature that the eye picks up most readily.
Tooth structure is also translucent, a quality that must be matched in the restoration. Normally enamel is not completely transparent but translucent to a degree. To recreate that look requires various staining composites. Translucency is usually more pronounced in the incisal thirds of teeth.
To create translucency, the violet, blue, and red are added as appropriate. For female patients a blue hue is used; for male patients a more violet color is chosen. The enamel layer (or microfill) is placed over the translucent characterization.
Opacity originates in the dentin. It is seen throughout the entire tooth structure, mostly at the gingival third and mid-third, but is less apparent interproximally. As one approaches the incisal segment, the teeth are translucent rather than opaque. In building up a chipped tooth, the internal dimension requires a more opaque layer.
Fluorescence is defined as the look of the teeth under a “black” or ultraviolet light. Natural teeth sparkle white, unnaturally so, under a black light. The dentist must use composites that have fluorescence built in to recreate this. Otherwise, anterior veneers built up with a nonfluorescent composite disappear under black light conditions. It seems that the individual’s teeth are missing, which is not esthetically pleasing. Natural fluorescence also has components that benefit the appearance under natural and sunlit conditions, creating a certain “glint” that is defined as natural looking. Natural fluorescence is an important addition to composites used in direct composite bonding.
The options for treatment are presented to the patient so that, along with the dentist, a mutual decision can be made regarding what will be done. The orthodontic condition of the teeth must first be assessed. It may be wise to first reposition the teeth with either traditional orthodontic care or with Invisalign. Once completed, one can alter the position, shape, and color of the teeth with either porcelain or composite veneers. Another method is to temporarily alter the appearance with a “Snap-on Smile” technique in which an impression is taken and sent to the laboratory; the shade is chosen to create the desired look and color of the teeth.
It is best to pre-evaluate what can be done on the teeth with orthodontic wax applied on the tooth structures. This is the traditional initial wax mock-up. Alternatively, composite can be used, a digital imaging software system may be used as well. These smile design programs can be used to create an esthetic look. The images are printed out and given to the patient to consider. Photographs and impressions are also taken. A wax mock-up can be constructed on a model in a laboratory, or in the office. A three-dimensional model is made to show the patient the desired look.
Assuming the patient has accepted the treatment, an appointment is scheduled. Anesthetic can be used or not. There is no need to numb the patient unless the procedure is more invasive. The dentist and patient commit to the procedure and determine whether it is necessary to reduce a tooth. Then the actual bonding process is undertaken, followed by polishing. A follow-up visit checks on the integrity of the bonding, to make sure the contacts are proper, to ensure that the margins of the composite do not impinge on healthy gingiva, and to protect the veneers with a night guard to prevent chippings from parafunctional activity.
The impression for the night guard is taken after the composite have been applied. If the patient is happy with the look, an impression can be taken then, and a night guard fabricated in the office. The type of night guard depends on the parafunctional activity. There are different types of designs, laboratory, and in-house. The NTI Tension Suppression System, made by Trident Dental Laboraties (Hawthorne, California), an anterior incline, covering either the entire arch or half of the arch from canine to canine. These soft splints have a soft interior and a hard exterior.
Treatment depends on the position and shape of the teeth and whether they are chipped, discolored, and so on. Generally the dentist tries to prepare as little as possible. The goal is to be on the enamel and not in the dentin because enamel achieves a better bond. If the tooth exhibits sharp ridges or sharp edges, it is not necessary to reduce it. It may be possible to add the composite to it without reduction. The author’s practice is to bevel the enamel to create a flare so the finish appears flush with the superficial tooth structure. Beveling increases the surface area for maximum durability and esthetics.
The extent of the esthetic problem dictates how much of the tooth structure is involved. It may be advisable to extend it all the way down to the gum line, or to stop midway through the tooth with a bevel.
On the lingual, the margin is positioned where there is enough space to retain the beveled surface without sharp edges. When the patient occludes, the occlusion should not be at the margin, where composite meets the enamel. Occlusion should occur either on the composite or on natural tooth structure, not at the actual margin.
For the bonding procedure the goal is to have as much enamel present as possible. The enamel is completely etched and rinsed but not completely desiccated. Adhesive is then applied. The site is isolated from the adjacent tooth with a clear Mylar strip.
After application, air drying, and light curing of the bonding agent, the initial layer of composite is adapted to the tooth, starting at the interior of the preparation and building out. A base layer is applied to control color over the whole tooth. This is cured, and then subsequent layers are placed, curing between each layer of composite.
To recreate the ideal three-dimensional incisal anatomy of the anterior teeth, the composite is applied to the inner dentin first. The lingual portion of the incisal is placed against a matrix of silicone or rubber template to recreate the lingual. There are usually three layers applied up to the incisal area, depending on the degree of transition needed. The goal is to impart a natural look of translucency and to include any necessary stain.
Finishing diamonds are used from coarse to medium to fine. Then polishing carbides create a smoother finish followed by a white stone. Finally disks Super Snap Shofu, from coarse to fine. Dental Corp. (San Marcos, California) followed by diamond polish paste called Diaglaze by Antraco Inc. (Livingston, New Jersey) to produce a polished texture.
Composite bonding should be checked yearly, at least, and touchups may be required. It is possible to resurface the composite using the above technique. It is also possible to revitalize composite. At times they may absorb some pigment and stain from consumed substances. Polishing the dull surfaces improve their appearance immediately. Patients are also advised to avoid or minimize eating things that are too hard or crunchy. Examples include ribs and pistachio nuts. Patients must be meticulous in their homecare. This includes oral hygiene.
A female patient had short and narrow upper anterior teeth with space present interproximally. She was unhappy with her appearance (Figure 15-1, A and B). A treatment plan was established to include bonding the maxillary anteriors, canine to canine, while the rest of her upper dentition involved crown and bridgework. The end result portrays teeth that met her esthetic and functional expectations, and made her look attractive, and complemented her appealing facial features (Figure 15-1, C and D). The procedure took about 4 hours to complete and was done in a single sitting. She returned for a follow-up about 2 weeks later to make sure her gingiva were healthy, the bonding intact, and the esthetics up to her expectations.
Section B Transitional Bonding
Transitional bonding allows practitioners to make major or minor changes in occlusion and esthetics with little or no reduction of tooth structure (Figure 15-2). With this approach it is possible to address cases with various esthetic problems, and, perhaps more important, health issues can often be treated. Examples include wear from bruxing; loss of occlusal tooth structure from erosion, decay, or fractures; and numerous teeth missing. Such situations may cause a decrease in vertical dimension leading to esthetic and functional problems. Restoring teeth that have worn down or are developmentally small so that the teeth are long enough or large enough to look more attractive without opening the bite could create a very deep overbite or other negative change. By increasing the vertical dimension one can often compensate for that.
FIGURE 15-2 Transitional bonding completed on the eight upper teeth, the cusps of the lower premolars, and the first molars to restore wear for esthetics and function. Vertical dimension of occlusion (VDO) was increased slightly. Pre-treatment (A, C, and E) and post-treatment (B, D, and F) photos.
Increasing the vertical dimension of occlusion (VDO) allows more space or clearance for restoring wear and lengthening the teeth. Most people will experience some loss of VDO with age. Many adults by the age of 50 could benefit from treatment that lengthens teeth for esthetic and/or functional improvements.
The ability to adhere restorative materials to enamel and dentin is a critical development. Clinical dentists are now able to bond composite to tooth structure with a strength comparable to the bond of enamel to dentin. This adhesive bond is very long lasting and, under normal occlusal forces, will provide retention of a restoration for years.
Current composites are not routinely more fracture resistant than early versions, but by having particle sizes that allow them to be more polishable, the current materials are more esthetic. These materials’ wear resistance is similar to that of enamel as well. The microhybrid and nanofill composites that have been developed in the last 20 to 25 years are critical for the success of transitional bonding. Handling properties that allow for placement, sculpting, curing on demand, contouring, and polishing allow these restorations to mimic natural tooth structure.
In the last few years the advantages of increasing VDO for patients who have lost some vertical dimension or who never had a fully developed VDO have become more accepted. This procedure can be predictably successful when the occlusion is handled properly.
Often the dentist is faced with conflicting demands between function and esthetics. The first step in preparing for any major change is an esthetic evaluation of the patient, using photography, study models, and a clinical examination. For a patient with obvious esthetic shortcomings, an “improved smile” should not be the goal—that is too easy. The goal should be to determine what changes would provide the “best smile possible” for a patient. A systematic approach to smile analysis, using smile design principles, promotes this goal. This would include principles such as the height-to-width ratio of the esthetic zone, width-to-length ratio of the upper central incisors, arch and tooth widths and proportions, and smile line, as well as numerous others.
Once the esthetic treatment plan has been determined, then the tooth size, shape, and position are evaluated in terms of whether they permit the ideal functional outcome. At this point the dentist determines whether the centrals have been lengthened sufficiently and whether that would create a deep bite that might compromise occlusal function. Determination of whether, and how, to adjust the occlusion to obtain ideal function would be the next important step. That might include increasing vertical dimension or, rarely, decreasing it. After occlusal principles have been used to confirm whether this esthetic change will work functionally, then the proposed treatment plan for the patient can be presented.
There will be some cases in which the esthetic and functional treatment plans cannot be rectified. For instance, increasing upper anterior tooth length results in greater overbite unless the VDO is increased. If the patient is an occlusal Class II, increasing VDO to compensate for this will result in an increased overjet if the mandible is in centric relation. So a compromise may be required to either the esthetic or the functional plan.
Each case is evaluated considering the dental and periodontal condition, but occlusion is a major factor. Generally, the goal is to end up with teeth of normal size and length, having a normal amount of overbite and overjet, with anterior guidance in protrusive and canine guidance in right and left lateral excursions. Ideally the guidance provides posterior disclusion. In successful cases these esthetic and functional goals will have been achieved.
A common situation is severe wear caused by bruxism, in which the patient has a reduced vertical dimension. Such teeth can be restored to their original condition or better. In less common cases there may be a skeletal growth problem that produces a mismatch in the size of the maxilla and mandible, and a Class II or III occlusion. In a Class III patient whose maxilla is underdeveloped and tooth display is less than desired, upper teeth can be lengthened and bulked out facially for better esthetics including increased tooth display and lip support. By opening the vertical dimension in such cases, it may be possible to alter these cases enough that a Class I occlusion results, because when the mandible is in centric relation and VDO is increased, overjet also increases.
Extensive decay is a less common indication. Decay may be severe enough that loss of tooth structure has allowed some collapse of VDO as with tooth loss. Restoration of the teeth including increasing VDO creates better esthetics and function.
Another indication is a bulimic patient who has sufficient erosion of the upper lingual surfaces that anterior teeth have supererupted. Such patients may not have experienced an actual loss of vertical dimension if the posterior teeth are intact, but opening the bite can create enough occlusal clearance to restore these eroded surfaces without having to prepare them as for a traditional restoration—probably a crown—resulting in more loss of tooth structure.
The prior examples all include increasing VDO. However, the majority of restorative cases will not require that. A more common indication would be a patient who has worn the anterior teeth enough that anterior guidance is deficient, with resulting posterior interferences. Restoring anterior guidance can be accomplished without opening the bite. Building more guidance than the patient originally had may also be possible—in patients with developmentally small teeth, for example.
Ideally, incisal and canine guidance should be built so that the posterior teeth disclude in all excursions. This posterior disclusion protects the posterior teeth. If the anterior teeth continue to wear, then rebuilding them as posterior interferences recur is a valid option, as opposed to equilibrating away enamel on posterior cusps.
Another indication would be a patient who has a slide from centric relation (CR) to maximum intercuspal position (MIP). Rather than equilibrate (removing enamel) to correct this, consider positioning the mandible at the first point of contact (typically second molars touching on one side) and augmenting other cusp tips to create new occlusal stops to stabilize this mandibular position, which now becomes the MIP. The slide can be eliminated without any enamel loss. Anterior centric stops can be built by adding to the lower incisal edges, but more commonly the author achieves this by adding to the lingual of the upper anterior teeth; often in combination with lengthening the upper anteriors.
This type of approach provides the patient with a more ideal occlusion (CR now coincides with MIP, and anterior guidance provides posterior disclusion) and results in a more esthetically pleasing smile (restoring worn upper anterior teeth for more tooth display); and conserves tooth structure (little or no prepping, nor an equilibration, is required). Numerous other advantages are achieved as well, but these alone make this option very desirable.
Periodontal disease and tooth mobility with anterior flaring could also be a reason for decreased VDO and a collapsed bite. One contraindication to lengthening teeth is periodontally involved, unstable, mobile teeth.
Another significant contraindication is the dentist who does not feel confident of his or her clinical skills related to technique. Transitional bonding is a somewhat technique-sensitive procedure, and without the training and experience to achieve predictable results, many dentists should hesitate to attempt it.
Glass ionomers and resin ionomers are not appropriate material choices because of handling and mechanical properties. The material should be sculptable and fairly viscous, providing enough working time to adapt the material and then cure on demand. These materials do not hold up well in the occlusal situations with incisal edges and built up cusp tips. The compressive and shear forces during normal mastication—and certainly during bruxing—would likely cause fracture and wear on surfaces subjected to mastication. Esthetically these materials are lacking, as well.
Amalgam is not appropriate because of its un-esthetic properties and the difficulty in building up an incisal edge. Certain posterior situations might allow amalgam to be one choice—for instance, if old fillings or carious lesions also need restoration.
Ceramics may be appropriate but only for a definitive restoration—not a transitional restoration. Cost is a significant disadvantage as well. There are situations in which it is appropriate to restore some teeth in porcelain, whereas other areas of the mouth are treated with transitional bonding.
Composite is the ideal material for this procedure. It is the most versatile of all restorative materials and offers many advantages including the ability to adhere to tooth structure even in the most non-retentive situations. Handling and mechanical properties allow these restorations to be built intra-orally and to survive for an extended time.
A significant advantage of using composite and the transitional bonding procedure is that it is possible to be extremely conservative in maintaining tooth structure. The great majority of cases require little or no preparation. If preparation is needed, it is more conservative than with any other option.
Another advantage is that these restorations are very easy to adjust as the dentist is refining occlusion or completing esthetic contouring. The composite can be reduced quite quickly or can be added to without much difficulty, if necessary.
The technique is a direct technique, so it does not require laboratory involvement other than for a diagnostic wax-up. A wax-up on mounted models is recommended so as to create a template (e.g., putty index) to aid in the intra-oral procedure. An excellent alternative to obtaining a lab wax-up is for the dentist to use composite on the mounted models and mock up the case. This provides valuable practice in handling composite, sculpting, and contouring—all skills that enhance the intra-oral result.
Composite can be very esthetic. Although the transitional bonding technique does not maximize the esthetic results—because there is no layering of materials for effects such as incisal translucency or shade blending—a major esthetic improvement can still be expected. The author estimates that 70% to 90% of the esthetic improvement can be accomplished with transitional bonding as compared to “ultimate esthetics” composite restorations or porcelain restorations.
Another advantage is the option to upgrade the treated teeth to definitive ceramic restorations at some point (either all at once or phased in a few teeth at a time), using any remaining composite—after preparation—as a core buildup. Another option is to improve the esthetics with composite by prepping away a portion of the transitional bonding and then layering composites of varying shades and/or translucencies for a more ideal, esthetic result.
In addition, the compatibility of composite with natural tooth structure in terms of wear is ideal. Having a material that wears slightly faster than enamel is desirable because it is preferable to have restorations wear rather than opposing natural teeth, as may occur with porcelain restorations.
Fracture resistance is another advantage. The fracture toughness values are so similar between composite and feldspathic porcelain that there is no significant statistical difference. In normal situations when the restorations are built properly, there should be no greater incidence of fracture than with porcelain restorations, similar to the incidence with natural teeth, as well.
Marginal integrity is an advantage, as well. With composite it is possible to develop margins that are extremely smooth and sealed—especially supragingival margins ending in a feathered finish over a bevel on enamel. On the other hand, consider the margin of a class II posterior composite with a deep proximal box: there is little or no enamel to bond to, more distance from the curing light, potential moisture control problems—all routine challenges for achieving sealed, smooth margins in class II composites. Most of the margins built in transitional bonding are supragingival, so the situation at the margin is very different; there is enamel, and a beveled margin means minimal bulk of composite, making polymerization shrinkage less critical—all factors that lead to margins that are very resistant to microleakage.
Finally, fees should be lower than for definitive restorations. If only anterior teeth are being treated, the savings may not be as dramatic as when many posterior teeth are included. The time to complete anterior teeth should be less than performing definitive restorations, but there is a much greater differential when building up buccal cusps of posterior teeth. So when more teeth are included in the treatment plan, generally the savings grow exponentially. This is a critical advantage for many patients.
Longevity is still not as good as one might like. The restorations will not last as long, in most instances, as porcelain restorations. The dentist should appreciate that longevity is not every patient’s highest priority. The advantages described earlier may be more valuable to many patients than longevity.
Technique sensitivity of any adhesive restoration is still a challenge. Moisture control in the wet environment of the mouth is often less successful than desirable—but this equally affects all materials to be bonded, not just composite.