Minimally Invasive Ceramic Restorations: A Step-by-Step Clinical Approach

Minimally invasive approaches are generally considered highly desirable strategies in all dentistry fields, including restorative dentistry. A primary challenge of restorative treatment is obtaining excellent esthetic results while maximizing preservation of intact hard-tissue structure, ie, enamel and dentin.¹ Increasing the preservation of dental tissues has a profound impact on the lifespan of teeth.²

The growing demand for increasingly conservative and esthetic dentistry has greatly impacted the development of adhesive materials and ceramics such that they are enabling successful adhesion to tooth structures.³ Also, mechanical and optical properties have improved, following the principles of biomimetics.^4,5

Evidence of treatment options for indirect ceramic restorations that need no or minimal tooth reduction does exist.⁶ Some laboratory⁷ and clinical data⁶ indicate good levels of success after a short, medium, and long term.⁸ However, despite the increased popularity in this area, clinical protocol guidelines for diagnosis, treatment planning, and execution of minimally invasive ceramic veneer restorations have been scarce in recent years.

The aim of this report is to show a step-by-step clinical protocol for diagnosis, treatment planning, and execution of minimally invasive ceramic restorations.

A 30-year-old woman was referred to the post-graduate clinical services at Araçatuba Dental School. The patient's chief complaint was the esthetics of her maxillary teeth, mainly regarding the multiple diastemas and tooth shape and color.

A sequence of extra- and intraoral photographs was taken. Frontal and lateral profile extraoral photographs of the patient's face were taken at different moments, including images while her lips were sealed and slightly opened, and a discreet smile and a wide smile (Figure 1). Closer views of the patient's mouth, including sealed lips, opened lips, and a wide smile, are shown in Figure 2. Figure 3 shows intraoral images of the maxillary arch and the dentition inmaximum intercuspation.

Preliminary full impressionsof the maxillary and mandibular arches were taken with polyvinyl siloxane (PVS) (Virtual, Ivoclar Vivadent, ivoclarvivadent.com). Based on the photographs and casts, a diagnostic wax-up was built to alter the patient's smile. Three important factors to evaluate in this step are the insertion pathway of the veneer, tooth substrate color, and the final color of the restoration.

With the information gathered, laminate veneers were waxed from canine to canine. To avoid excessive dental reduction, silicone guides were generated based on the diagnostic wax-up. The silicone guides allowed a controlled dental reduction through visualization of the space necessary to build the ceramic veneer (Figure 4).

Furthermore, using a silicone index and bis-acrylic resin, a copy of the wax-up was transferred to the patient's mouth, which allowed final restoration shape, approximated color, and new dental alignment to be perceived (Figure 5). This preview of the result is called a "mock-up,"⁹ or reverse planning. Any modification that the patient may desire or the clinician may detect is then analyzed and the adjustment made; after patient approval, all information is collected via the mock-up using photography and full-arch impressioning. When no preparation or minimal preparation is desired, there is no need for provisionalization, and thus the mock-up can be removed from the mouth.¹⁰

When minimally invasive ceramic restorations are planned, teeth color has a strong impact on the final color of restorations because of the translucency of thin ceramic. After clinical examination, dental office bleaching with hydrogen peroxide 37% (BM4,bm4.com.br) in four sessions was indicated.

As mentioned above, dental reductions were based on the diagnostic was-up and were driven by silicone guides (Figure 6). In Figure 6 the buccal (upper left) and incisal (upper right) relationships between the existing and planned ceramic veneer (the volume of final restoration) are shown. Based on the space between the existing teeth and volume of the final restoration, the amount of tooth reduction was projected. Minimal tooth reduction was made on the black painted areas (Figure 6, lower left and lower right), mainly evidencing sharp angles or faces that require insertion axis correction.

The patient's unprepared teeth (Figure 7, upper left) had some sharp angles; such angles need to be avoided when using thin veneers, as prosthetic preparations for thin ceramic restorations should have rounded corners and a smooth surface. The lower left image in Figure 7 shows the final teeth preparations.

A simultaneous impression technique was carried out by using double gingival retraction cords and PVS material (Virtual, Ivoclar Vivadent) (Figure 8). Looking at the final stone cast (prepared teeth) one can determine whether there is enough space to build the ceramic restoration of, on average, 0.3 mm (Figure 9). Digital photographs were used for tooth shade selection. All data, including dental photographs, casts, and the diagnostic wax-up were sent to prosthetic technicians to create the veneers.

Pressed lithium-disilicate ceramic was used to build all laminate veneers. A layering technique was used to finalize the ceramic restoration (Figure 10). Based on a diagnostic wax-up, a pressed lithium-disilicate coping was obtained with low translucency ceramic (LT IPS e.max, Ivoclar Vivadent). For better customization of shade, the laboratory technician then applied the layering technique for enamel using a high translucency fluorapatite-based ceramic (IPS e.max Ceram, Ivoclar Vivadent).

All laminate was placed and checked to ensure proper marginal fit (Figure 11, top). Because the ceramic veneers were very thin there was high translucency, which greatly influenced the tooth substrate hue on the final color of the cemented veneer restorations. The try-in cementation step optimized the final appearance of the translucent restorations because it allowed the dentist to choose cements with high or low value (Figure 11, middle). High-value cements potentially enhance the brightening effect of the restoration, while low-value cements bring a warming effect. In the present clinical case the resin cement with high value was selected (Figure 11, bottom) (HV+3, Variolink Veneer, Ivoclar Vivadent).

Before cementation, to ensure correct insertion of each laminate veneer, each one was tested and the insertion pathway was defined from the buccal aspect until the complete veneer settlement. The sequence of cementation was defined from midline to canines, always in pairs (central incisors, followed by lateral incisors and canines). This method of cementation ensured that midline alignment would be followed.

The ceramic surfaces were prepared as follows: First, they were immersed in isopropyl alcohol, water-rinsed, and air-dried. Then, hydrofluoric acid-etching 5% (IPS Ceramic Etching Gel, Ivoclar Vivadent) was done for 10 seconds, followed by water rinsing and air drying. The next step was silane application (Monobond S, Ivoclar Vivadent) for 2 minutes. Finally, the intaglio surface of each veneer was coated with hydrophobic bonding agent (Heliobond, Ivoclar Vivadent) and thinned by a gentle blow of air, and then light-cured for 10 seconds. The teeth were prepared in pairs, as follows: First, prophylaxis was performed with pumice and water. Then phosphoric acid-etching 35% was done for 30 seconds for enamel, followed by adhesive application (Heliobond) and light-curing. Adhesive cementation was completed by using a light-curing resin cement (HV+3, Variolink Veneer). Each veneer was light-cured for 40 seconds on each face, using a properly calibrated light-cure device.

Immediate results of the final restoration showed facial harmony and good esthetics with good function (Figure 12). Moreover, it was evident by the patient's smile that the outcome rejuvenated her self-confidence (Figure 13). Figure 14 shows the patient's smile at 18 months' follow-up. After 2.5 years the patient remains very satisfied, and all veneers are still in excellent condition, presenting satisfactory esthetics and periodontal health.

The philosophy of minimal intervention for the placement of restorations is in evidence.¹¹ In the past, healthy tooth structure has been sacrificed for cosmetic reasons. However, as patients realize they can improve their appearance without having parts of their teeth removed, there has been an increased demand for minimal preparation or no-preparation restorative design.¹²

Basically, minimally invasive ceramic restorations are usually made with hydrofluoric-etchable ceramics, such as glass-ceramics (feldspathic), using the refractory dye technique, fluorapatite-based glass ceramics, and lithium-disilicate ceramic. These materials are used because of the excellent optical properties and reliable mechanical properties they achieve after adhesive cementation.¹³ Glass-ceramics made with the refractory dye technique, however, have a low fracture resistance prior to bonding to tooth structure, and from a clinician's standpoint, handling can be difficult, from checking the final result with the try-in paste to bonding procedures.¹⁰ Therefore, lithium-disilicate ceramic has been used extensively recently because its excellent mechanical properties even before adhesive cementation enable a safe proof and try-in.^12,13

Advantages of using conservative ceramic restorations are minimal tooth tissue removal, the preparation surface being preserved on enamel, and the absence of a provisionalization step, thereby increasing the success and quality of this modality of treatment.¹² Because this modality of treatment requires only minimal tooth structure removal on the preparation, it can be especially indicated for young patients who need tooth shape and/or color modifications. The preservation of sound tooth tissue is important in the long term, mainly because of the average lifespan related to all-ceramic restorations.¹⁴ The survival rates and success of veneer restorations are variable.^15,16 Beier et al showed up to 93.5% and 82.9% of success for laminate veneers after 10 and 20 years, respectively.¹⁷ Another study showed up to 98.8% of success for this kind of restoration at 6-year follow-up.¹⁶ Because of the cycle of restorative dentistry, minimal preparations are desirable, as the restoration will likely be replaced one day.¹⁸

With minimal or no tooth preparation, the tooth surface remains mostly in enamel. Because of the absence of dentin exposure and minimal tooth modification, the provisionalization step is optional.¹⁰ With no provisonalization the soft tissue remains stable, which helps enhance the results of impressioning and adhesive cementation.¹⁰

Many authors showed that ceramic restorations placed on enamel substrate have higher survival rates than those placed on dentin substrate.^19,20 This occurs because adhesive cement bond strength is higher on enamel than on dentin.²¹ Also, microleakage and margin discoloration related to ceramic restorations placed on enamel is lower than with those placed on dentin substrate, increasing the longevity of veneers.^3,22 Furthermore, some authors showed that remaining enamel thickness is very important mechanically for the longevity of ultra-thin veneers,²³ as it may prevent catastrophic failure.

The use of minimally invasive ceramic restorations is an excellent option for conservative restorative treatment. When the diagnosis and indication allows, this approach ensures minimal tooth reduction, enabling exceptional esthetic results and, in turn, increased patient self-esteem. General practitioners and specialists can follow the simple protocol outlined herein. For the selected clinical case, the 2.5-year follow-up suggests good clinical results with this type of treatment.

Carlos Marcelo Archangelo, DDS, MS, PhD
Associate Professor
Institute Federal of Parana-IFPR
Curitiba, Brazil

José Carlos Romanini, TPD
Dental Prosthetic Technician
Laboratório de Prótese Dentária Romanini
Londrina, Brazil

Karen Cristina Archangelo, DDS, MS, PhD
Assistant Professor
Institute Federal of Parana-IFPR
Curitiba, Brazil

Isis Almela Endo Hoshino, DDS
Universidade Estadual Paulista-UNESP "Júlio de Mesquita Filho," Araçatuba Dental School
Department of Restorative Dentistry
Araçatuba, Brazil

Rodolfo Bruniera Anchieta, DDS, MS, PhD
Assistant Professor
Centro Universitário do Norte Paulista-UNORP
Sao Jose do Rio Preto,Brazil
Universidade Estadual Paulista-UNESP "Júlio de Mesquita Filho"
Araçatuba Dental School
Department of Restorative Dentistry
Araçatuba,Brazil