Minimally Invasive Dentistry: A Conservative Approach to Smile Makeover

When taking conservative approaches to smile makeovers, clinicians are employing newer materials and techniques that are aimed at improving the appearance of tooth color and shape while minimizing or eliminating tooth preparation.¹ While some have called this approach “modern restorative dentistry” or “minimally invasive dentistry,”² the concept is based on preserving tooth structure, especially the most protective layer of tooth structure—enamel.³

Perhaps the most conservative esthetic procedure to improve a smile is tooth whitening, a treatment that continues to significantly impact the practice of dentistry.^4,5 Public interest in having whiter, brighter teeth is clearly evident in advertisements from toothpaste manufacturers touting the “whitening” formulations in their products and by the number of individuals seeking whitening procedures from their dentists.⁶ Combining tooth whitening with other cosmetic dental procedures with a focus on the overall smile can transform a patient’s appearance.

As people have become increasingly cognizant of the impact optimal cosmetic dentistry can have on one’s self-image, self-esteem, and self-confidence, patients are tending to elect to have more cosmetic dental procedures to complement their newly whitened smiles.⁴ Patients garner a new awareness of or begin to place a greater “value” on their smile and, as a result, may become self-conscious about other discolorations on their teeth such as stark-white or darkened brown spots. Additionally, spaces between anterior teeth become more noticeable as the dentition is whitened due to the increased contrast of the brighter teeth adjacent to the darkness of the back of the mouth.

Just as manufacturers have developed new whitening products to answer consumer demand for brighter smiles, so, too, more products have been developed aimed at conservative treatment of early decay and/or discolorations with remineralizing pastes. Such pastes can be combined with tooth whitening for an ultraconservative approach to treating a discolored smile.⁷

Several disciplines are available to conservatively correct deficiencies in the smile, including orthodontics, restorative dentistry, and tooth whitening. When a patient presents with multiple discolorations on numerous teeth and various diastemas, the clinician is faced with several restorative options.⁸ Indirect approaches may include full coverage of the tooth through crown or partial-crown preparations, conservative preparation, or no preparation of the tooth for ceramic veneer restorations. Direct approaches may include conservative tooth preparation or no tooth preparation with application of composite resin veneers. Also, prefabricated veneers have recently seen a revitalization (eg, Edelweiss™ Composite Veneer System, Ultradent Products, Inc., ultradent.com; Componeer®, Coltene, coltene.com; Cerinate® One-hour™, DenMat, denmat.com) with ceramic or resin veneers being adapted onto existing unprepared or prepared tooth structures, and then bonded into place.⁹ All these techniques have various degrees of technical-operator demands, offer a range of longevities, and entail different costs.

A conservative method to treat discolored teeth that have diastemas is a freehand additive technique with composite resin. However, selecting the correct shade of resin in the whitened dentition can be challenging.⁵ Fortunately, dental manufacturers are creating newer composite resin formulations with optical properties that enable the material to effectively blend into the dentition and become undetectable.

The following case presentation depicts use of these conservative approaches and materials to not only treat discolored teeth and the spaces between them, but to restore harmony and balance to the patient’s smile.

A 24-year-old man presented to the author’s office for treatment of a displeasing smile. The patient’s dental history included 3 years of traditional fixed orthodontics that resulted in multiple maverick shades of white and brown, indicative of early enamel demineralization and hypomineralization. A radiographic analysis confirmed no cavitational changes were present. In addition, some relapse had occurred, resulting in a noticeable maxillary midline diastema and a diastema between the left central and lateral incisors (Figure 1 and Figure 2). The right lateral incisor displayed a peg-like appearance that contributed to an unbalanced look (Figure 3).

Treatment options reviewed with the patient included tooth whitening combined with tooth preparation for ceramic veneers or remineralization therapy combined with tooth whitening and direct resin.¹⁰ It was mutually agreed that the latter treatment would be more conservative and appropriate for the patient at this relatively young stage of his life.

Remineralization of lesions that have not cavitated and still have an intact enamel surface uses fluoride to make the enamel more acid resistant and inhibit bacterial intracellular enzymes.¹¹ More recently, nanoparticle hydroxyapatite and casein phosphopeptide-amorphous calcium phosphate (CCP-ACP) have made calcium and phosphate ions bioavailable to aid in remineralization. For this case, the clinician opted to use MI Paste™ (GC America, gcamerica.com), a CCP-ACP–based product.

Dental photographs were used to establish a baseline for remineralization and whitening treatment. Study and working casts were taken for the production of treatment trays to be used at home as part of the remineralization and whitening process. Lastly, the goals for the smile design were discussed.

The elements of a pleasing smile include normal tooth position and proportion, a normal (perpendicular to horizontal) midline, normal tooth contacts, and a bright value of the dentition.¹² The photographs and study cast were analyzed to develop these elements for the resin application.

Several techniques have been published on the use of composite resin to restore anterior teeth.^13-15 A freehand technique was planned. A uniquely formulated composite resin with the same refractive index as enamel (ENA Hri, Micerium S.p.A., micerium.com) was chosen to restore this case, because it was anticipated that the process would be completely additive and this resin features beautiful optical properties similar to enamel. Its nano zirconium-oxide composition has ideal physical properties that lend to no-preparation cases such as this one.

Treatment began with a thorough prophylaxis and oral hygiene instructions. After the prophylaxis, the upper and lower teeth anterior to the molars were isolated with a lip and cheek retractor (OptraGate®, Ivoclar Vivadent, ivoclarvivadent.com). A “light microabrasion” technique was initially directed at the hypomineralized defects. Enamel microabrasion refers to the use of a low-concentration acid combined with an abrasive agent that is applied to the enamel. Commercial formulations for microabrasion pastes comprise a low-concentration hydrochloric acid (6.6%) with a silicon-carbide abrasive and silica gel as a binding agent. The paste used in this case (Opalustre®, Ultradent Products, Inc.) etches the enamel surface more aggressively than the phosphoric acid typically employed in adhesive restorative dentistry.

A right-angle, latch-type, slow-speed handpiece running at 1000 rpm and a webbed rubber cup were used to apply the microabrasion mix in three separate 30-second applications. Between applications, the microabrasion paste was rinsed from the tooth surfaces and the surfaces dried. The abraded enamel surfaces were then remineralized via a 5-minute application of the aforementioned CCP-ACP paste (MI Paste) (Figure 4). The process took 30 minutes of chairtime and was repeated for three visits, which does not include the visit for prophylaxis. Between visits, the patient was instructed to apply the MI Paste by tray for 5 minutes, twice a day. A progress photograph was taken at each visit (Figure 5).

After three microabrasion visits, the patient returned for post-remineralization color evaluation with most of the brown and white discolorations gone. A decision was made to extend the teeth whitening process using the clinician’s office daytime whitening protocol. The patient was given DayWhite ACP (Philips, usa.philips.com) to use in the home trays. This 9.5% hydrogen-peroxide whitening formulation contains ACP, potassium nitrate, and fluoride to help reduce sensitivity and to continue to rebuild the enamel. The daytime whitening protocol comprises three successive 10-minute applications daily, changing the gel between applications, for 2 weeks. The final whitening results were a pleasing, bright dentition (Figure 6).

The application of the composite resin began with shade selection. The first step in shade selection when using ENA Hri is to determine the enamel value: UE1 = average, UE2 = medium bright, and UE3 = very bright. Shade selection also takes into account the age of the patient and the enamel thickness to be replaced (0.4 mm or 1 mm). The resin numerical value increases as the thickness of the resin increases. The enamel shade is also balanced against the dentin chroma. While this shade selection process may differ from that of other resin systems, in the author’s experience it is actually quite simple and accurate and offers lifelike results.

The high-value “very bright” shade, UE3, was selected because it is used for bleached dentitions. A small, “hot-dog” form of resin was applied to the anterior diastema and then cured to confirm the match. The author used three instruments to apply the resin: an IPC carver (Hu-Friedy, hu-friedy.com), a No. 6 explorer (Hu-Friedy), and a No. 3 composite brush (Cosmedent, cosmedent.com) (Figure 7).

A digital caliper was then used to determine the mesial-distal diameters of the central and lateral incisors. Because tooth No. 7 had a Bolton tooth-size discrepancy,¹⁶ the distal of tooth No. 8 was sliced with a diamond mesh disc (Visionflex™ 220, Brasseler USA, brasselerusadental.com) and then recontoured and polished with blue, yellow, and pink dental polishing discs (FlexiDiscs®, Cosmedent) to create even spacing for adding resin to the mesial of the lateral and central incisors.

The teeth were cleaned with coarse pumice, then each surface that was to receive resin additions was etched with phosphoric acid for 15 seconds and rinsed with water for 30 seconds before an adhesive resin (Clearfil™ Photo Bond, Kuraray, kuraraydental.com) was applied to the enamel surface for 20 seconds and then light-cured for 20 seconds. This process was repeated for each surface to be restored rather than all at once.

High-quality, clean gloves are essential for freehand resin application to minimize foreign particles. The composite resin was rolled into a convenient hot-dog shape and applied with the IPC instrument to the mesial-facial surface of the right central incisor. The resin was feathered into place with the IPC instrument, then contoured just under the free gingival margin and at the incisal embrasure using the No. 6 explorer. Lastly, the No. 3 brush was used to create a smooth surface texture. The resin was then cured for 30 seconds.

The lingual surface was approached in the same manner. To effectively close a diastema, the clinician can wrap the lingual resin application onto the labial, use the explorer to remove the excess, brush the resin into the facial resin, and then make sure the addition is straight incisal gingivally (avoid canting).¹⁷ The lingual addition is then cured.

As the diastemas are closed, the lingual wrapping of resin becomes more challenging. A Mylar strip can be placed to pull the resin through to the labial in one quick motion from lingual to facial. The excess is then brushed out as previously described.

After each addition was completed, only minimal finishing was required. Interproximal adjustments were polished with the yellow and pink FlexiDiscs and FlexiStrips® (Cosmedent). A piece of dental floss that was drawn through lip balm was then passed over the finished proximal surface. This allowed direct additions of resin to resin with contacts easily separated with a gentle torqueing of a plastic instrument (Premier No. 11, Premier Dental, premusa.com) placed at the gingival embrasure.

The final facial and lingual surfaces were polished to a high shine with the ENA Shiny Finishing System (Micerium S.p.A.). This three-step system uses a rubber point impregnated with diamond polishing pastes of two different grits, and then an aluminum-oxide paste applied with a felt brush. The results were bright, shiny, and evenly proportioned teeth (Figure 8).

Final adjustments—critical to making a smile fit the patient—were done with a medium sandpaper disc with the patient chair elevated to eye level with the clinician. The clinician focused on the incisal edges following the lower lip line and altered the incisal embrasures to create natural appearances that matched the age and gender of the patient. A goat-hair brush was used to polish the final corrections. The result was a smile unique to the patient (Figure 9 and Figure 10).

Dramatic improvements in a patient’s smile and overall appearance can be achieved in a conservative manner through treatment of the dentition with remineralizing pastes, tooth whitening, and composite resin. Dentists who have the training and skills to meet the increasing demand for esthetic procedures by patients seeking to restore a more attractive appearance may find an expanded role within their practices for this type of treatment. By incorporating the art and science of cosmetic dentistry into their enhancement therapy, dentists can create excellent results—ie, pleasing, enhanced smiles—on a consistent basis.

Jeffrey M. Rosenberg, DDS

Private Practice, Philadelphia, Pennsylvania

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