Posterior PartialCoverage Restorations: Inlays and Onlays
4
Petra C. Guess, dds, dr med dent, phd
Over the last decades, a shift toward the use of metal-free restorations for the restoration of posterior teeth has been observed. To meet the increased demands of patients and dentists for highly esthetic, biocompatible, and long-lasting restorations, several types of all-ceramic systems have been developed.1 Dental ceramics can be divided into two main groups: (1) silicate glassceramics and (2) high-strength oxide ceramics.2 Because of their favorable optical properties, silicate glass-ceramics are used as veneers for metal or all-ceramic cores to optimize form and esthetics. In monolithic application, small restorations, such as inlays, onlays, laminate veneers, and crowns, can also be fabricated. High-strength ceramics such as aluminum and zirconium oxide ceramics were developed as a core material for crowns and fixed dental prostheses to extend the indications to high-load–bearing areas.3 However, these all-ceramic systems are only rarely used for the fabrication of posterior partial-coverage restorations.4 Because of advances in computer-aided design/computer-assisted manufacture (CAD/CAM) technologies and their ease of application, machinable all-ceramic systems are increasingly used for posterior partial-coverage restorations. The variety of these all-ceramic systems is constantly evolving, and ongoing developments have led to the combination of several fabrication techniques and core-and-veneering systems.5 This chapter discusses the use of high-strength ceramics for posterior partial-coverage restorations in terms of: • Materials selection based on current materials science • Clinical (including in-office milling systems) and laboratory procedures • Clinical outcomes, including complications Evidence-based literature is reviewed to support the concepts discussed.
47
4
Posterior Partial-Coverage Restorations: Inlays and Onlays
Ceramic Materials For any type of restorative procedure, including partial- or complete-coverage restorations, laminates, and tooth- or implant-supported prostheses, it is imperative for the clinician to have an understanding of the characteristics of the chosen material. Because of the importance of that subject, this chapter introduces a classification scheme for dental ceramics and discusses the physicochemical properties of the materials. The classification presented in this chapter divides dental ceramics into three groups: (1) silica-based ceramics, (2) oxide ceramics, and (3) composite-based ceramics.
Silica-based ceramics Feldspathic veneering ceramics Veneering ceramics have been developed on the basis of the classic silicon dioxide–aluminum oxide–potassium oxide (SiO2-Al2O3-K2O) system, which is also used to produce household ceramics and porcelains. Because of this historical type of application, dental ceramics are often still called dental porcelains. Traditional feldspathic veneering ceramics contain 52 to 62 wt% SiO2, 11 to 16 wt% Al2O3, 9 to 11 wt% K2O, and 5 to 7 wt% sodium oxide (Na2O) along with various additional components, such as lithium oxide (Li2O) or boron trioxide (B2O3).6 They are often classified as highfusing (1,300°C to 1,400°C) or low-fusing (850°C to 1,100°C) materials, depending on their indication and core material. In contrast to glass-ceramics, the crystal phase in feldspathic veneering ceramics is not formed by controlled nucleation and crystallization. Phase transformation takes place in a fast, uncontrolled crystallization process.2 To avoid thermally induced stresses that may lead to failure, the coefficient of thermal expansion (CTE) of a ceramic veneering material matches or complements the CTE of the metal alloy or high-strength ceramic core material. Feldspar-derived glass exhibits a low CTE (8.6 × 10–6 K–1m/m). The mechanical properties of feldspathic veneering ceramics are the poorest among dental ceramic materials (flexural strength ~60 MPa) and are dominated by the high amount of glassy phase.7–9
Leucite-based veneering ceramics Filler particles are added to the base glass composition to improve mechanical properties and to control optical effects such as opalescence, color, and opacity. These fillers
48
are usually crystalline but can also be particles of a glass with a higher melting point. Particles of a crystalline mineral called leucite were the first fillers used in dental ceramics. Leucite crystals exhibit a polygonal shape with an overall diameter between 1 and 5 µm. The glass-ceramic component forms the crystals of a leucite type (K[AlSi2O6]) through controlled surface crystallization. Controlled heat treatment in the temperature-time functions of the crystals causes crystals to form at the surface of the glass grains from the SiO2-Al2O3-K2O base system with additions of Na2O, calcium oxide (CaO), B2O3, and other oxides.10 The tetragonal modification of leucite crystals results in a high CTE (~ 20 × 10–6 K–1m/m).11 By varying the proportion of leucite to feldspar glass the manufacturer can precisely adjust the CTE. Leucite-based veneering ceramics exhibit flexural strength values in the range of 80 to 140 MPa.12,13 To enhance optical properties, leucite crystals were precipitated by the mechanism of surface crystallization, and needlelike fluorapatite crystals (Ca5[PO4]3F) were formed through bulk crystallization in a glass in the composition range of 49 to 58 wt% SiO2, 11 to 21 wt% Al2O3, 9 to 23 wt% K2O, 1 to 10 wt% Na2O, 2 to 12 wt% CaO, 0.5 to 6 wt% phosphorus pentoxide (P2O5), and 0.2 to 2 wt% fluoride (F).14 Controlled nucleation preceded these crystallization processes. Nanoscale apatite crystals cause light scattering that resembles the scattering observed in natural tooth enamel. The CTE of apatite glass veneering ceramic is 9.7 × 10–6 K–1m/m.14 Veneering ceramics for dental restorations are classically sintered under vacuum to reduce the porosity of the final product. However, voids, cracks, and inclusions cannot be fully avoided.15 Recently, silicate ceramics that are pressed onto the core structure have been developed.2 As a result of the homogenous heat distribution and the viscous flow process, a dense veneering material is joined to the underlying core structure. Many manufacturers claim that these materials have simplified application techniques and that the results are more reliable because of the increased mechanical strength of the pressable veneering ceramics (110 to 140 MPa).16 Some veneering ceramics are also recommended for fabrication of small, monolithic restorations such as inlays and onlays or for characterization of bilayer inlay and onlay restorations.
Leucite-reinforced glass-ceramics Moderate strength increases can be achieved if appropriate fillers are added and uniformly dispersed throughout the
Ceramic Materials glass, a technique termed dispersion strengthening. Leucite is also used as a reinforcing crystalline phase at a concentration of 35 to 45 vol%.17 In the early 1990s, the lost wax press technique for allceramic restorations was introduced to dentistry as an innovative processing method. IPS Empress (Ivoclar Vivadent) is one of the most popular representative materials among leucite-reinforced glass-ceramic pressable ceramics. The molding procedure is conducted at 1,080°C in a special, automatically controlled furnace. Leucite crystals are formed through a controlled surface crystallization process in the SiO2-Al2O3-K2O glass system. Tangential compressive stresses develop around the crystals on cooling, as a result of the difference in CTE between leucite crystals and the glassy matrix. These stresses contribute to crack deflection and improved mechanical performance.18 IPS Empress exhibits a flexural strength of 120 to 180 MPa and a CTE of 15.0 to 18.5 × 10–6 K–1m/m).19 The material is suitable for fabrication of inlays, onlays, veneers, and crowns. Leucite glass-ceramics can also be machined with various CAD/CAM systems. Multicolored blocks were recently developed to reproduce color transitions and shading as well as different levels of translucency to simulate natural teeth.2
Lithium disilicate glass-ceramics Significantly higher strength, 350 MPa, was achieved with a glass-ceramic of the silicon dioxide–lithium oxide– potassium oxide–zinc oxide–phosphorus pentoxide– aluminum oxide–lanthanum oxide (SiO2-Li2O-K2O-ZnOP2O5-Al2O3-La2O3) system by precipitating lithium disilicate (Li2Si2O5) crystals. The crystal content of up to 70 vol% is considerably higher than that of leucite materials.18 Hightemperature x-ray diffraction studies revealed that both lithium metasilicate (Li2SiO3) and crystobalite form during the crystallization process, prior to the growth of lithium disilicate (Li2Si2O5) crystals.20 The final microstructure consists of highly interlocked lithium disilicate crystals, 5.0 µm in length and 0.8 µm in diameter. Mismatch between the thermal expansions of the lithium disilicate crystals and the glassy matrix results in tangential compressive stresses around the crystals, potentially responsible for crack deflection and strength increase. Crystal alignment after heat pressing of the lithium disilicate glass-ceramic leads to multiple crack deflections. Lithium disilicate ceramic, introduced as IPS Empress 2 (Ivoclar Vivadent) in 1998, is as moldable as leucite glass-ceramics but at a lower temperature of 920°C. The CTE is 10.5 × 10–6 K–1m/m.21 The consecutive pressable lithium disilicate glass-ceramic (IPS e.max Press, Ivoclar Vivadent) with improved physical
properties (flexural strength 440 MPa) and translucency achieved through different firing processes has been developed in the silicon dioxide–lithium oxide–potassium oxide–zinc oxide–phosphorus pentoxide–aluminum oxide– zirconium dioxide (SiO2-Li2O-K2O-ZnO-P2O5-Al2O3-ZrO2) system. Both pressable lithium disilicate ceramics can be used in monolithic application for inlays, onlays, and posterior crowns or as a core material for crowns and three-unit fixed dental prostheses in the anterior region. Apatite glassceramics are recommended for veneering. More recently a lithium disilicate glass-ceramic (IPS e.max CAD, Ivoclar Vivadent) has been designed for CAD/CAM. The milled lithium disilicate block is fabricated using a twostage crystallization process. Lithium metasilicate crystals are precipitated during the first stage. The resulting glassceramic has a crystal size of 0.2 to 1.0 µm with approximately 40 vol% lithium metasilicate crystals. At this precrystallized state, the CAD/CAM block has a flexural strength of 130 to 150 MPa and allows easier and more rapid machining. The final crystallization process occurs after milling of the restoration at 850°C in vacuum. The metasilicate crystal phase is dissolved completely, and the lithium disilicate crystallizes. This process also converts the blue shade of the precrystallized block to the selected tooth shade and results in a glass-ceramic with a fine-grained size of approximately 1.5 μm and a 70% crystal volume incorporated in a glass matrix.2 CAD/CAM–processed lithium disilicate glassceramic demonstrates a flexural strength of 360 MPa.22 Because of its favorable translucency and variety of shades, the material can be used for fully anatomical (monolithic) restorations with subsequent staining characterization or as a core material for subsequent coating with veneering ceramics. The manufacturer recommends its use for anterior or posterior crowns, implant crowns, inlays, onlays, and veneers.
Oxide ceramics Aluminum and zirconium oxide high-strength ceramics are only rarely used for the fabrication of posterior partial coverage restorations due to the inability of etching these ceramics. Therefore, scant literature can be found on these all-ceramic systems for minimally invasive indications.
Composite-based ceramics Composite-based ceramics (resin nanoceramic, Lava ultimate, 3M, and hybrid ceramic, Vita Enamic, Vident) have a flexural strength of 200 MPa and have recently been introduced as an alternative indirect restorative material because they have a greater ability to absorb impacts than do ceramics.23,24 However, use of composite resin for cuspal coverage 49
4
Posterior Partial-Coverage Restorations: Inlays and Onlays
a
c
is clinically questionable because composite resins exhibit greater wear and staining and weaker adhesion to teeth than do glass-ceramics.25,26 Clinical long-term data concerning the survivability and wear characteristics of indirect composite-based ceramic restorative materials are not yet available.
Indications for Inlays, Onlays, and Extended Partial-Coverage Restorations Because of improved awareness of oral hygiene and better prevention, including the sealing of erupted posterior teeth and application of fluoride, the incidence of caries is declining in developed countries. However, a strong increase in the prevalence of noncaries lesions has been observed within recent years.27,28 Excessive abrasion (attrition) and erosion of tooth structure are the most prevalent forms. Tooth integrity can be severely affected by bruxism and parafunctional activities.29 The prevalence of bruxism is reported to be 20% among the adult population.29 The most 50
b
Fig 4-1  Defect-oriented press-fabricated onlay and fullveneer restorations for management of extensive erosions in the maxilla (a) and mandible (b) and a reduced vertical dimension of occlusion (c). Extensive dentin exposure is visible. The patient’s chief complaints are hypersensitivity, esthetic limitations, lack of stable occlusion, and reduced vertical dimension of occlusion.
frequent causes of erosion are high consumption of acidic food and drinks. In addition, excessive intrinsic production of acid can result from disorders such as bulimia nervosa, gastroesophageal reflux disease, and hiatal hernia. Moreover, impaired salivary flow rate or buffer capacity and altered salivary composition, resulting from various diseases, medications, and aging, are described as etiologic cofactors of erosion.30,31 A large number of patients with these kind of tooth structure defects present combined etiologies. Therefore, these patients require a multifactorial preventive and restorative treatment approach. Because of the loss of enamel and resultant exposure of dentin, the affected teeth may lack occlusal, facial, and/or lingual tooth anatomy, which impairs function and esthetics. The vertical dimension of occlusion, occlusal contacts, and anterior guidance during dynamic mandibular movements may be compromised. In addition, discoloration of the exposed dentinal surfaces, tooth sensitivity, pulpal complications, and increased risk of caries are frequent dental consequences .32–34 Modern treatment approaches aim to prevent progression of tooth structure loss and to avoid or postpone the necessity for complete-coverage prosthodontic rehabilitation, which would result in the removal of additional large
Indications for Inlays, Onlays, and Extended Partial-Coverage Restorations
d
e
f
g
h
i Fig 4-1  (cont) (d to f ) Study casts. (g to i) Wax-up of defects. Esthetics will be restored by reconstruction of the vertical dimension of occlusion in the anterior and posterior dentition.
amounts of tooth substance.23 In patients with minimal enamel and dentin loss, occlusal stops can be built up with direct composite resin restorations. For all forms of moderate to intermediate enamel and dentin loss and destruction and small to medium restorations, the occlusal morphol ogy can be reestablished with a hybrid composite resin
used with a direct technique. For the reconstruction of severe tissue loss and a loss of vertical dimension of more than 2 mm, indirect tooth-colored restorations (onlay and extended partial-coverage restorations) are recommended35 (Fig 4-1).
51
4
Posterior Partial-Coverage Restorations: Inlays and Onlays
j
l
k
m
n
o
p Fig 4-1  (cont) (j and k) Preparation design includes anterior complete-coverage crowns and posterior onlay and full veneers. (l and m) Preparation designs are limited to smoothing of the occlusal surface and a buccal veneer preparation; proximal contact points remain in natural tooth structure. (n) Ultrathin onlay and full-veneer restorations (IPS e.max Press, staining technique with a thickness of 0.5 mm occlusally and 0.4 mm buccally). (o to q) Final result after adhesive cementation (Variolink II, Ivoclar Vivadent) of the all-ceramic restorations.
q
52
Clinical Procedures
a
b
c
Fig 4-2  Minimally invasive all-ceramic preparation designs. (a) Unprepared teeth. (b) For occlusal onlays, preparation is limited to the occlusal surface. (c) For full veneers, preparation includes the occusal and buccal surfaces.
Clinical Procedures The clinical success of dental ceramics depends on an array of factors, including initial physical properties of the material itself, fabrication techniques and clinical procedures that may damage these brittle materials, and the oral environment.
Preparation designs Cavity and preparation designs are controversial and crucial factors in the clinical success of posterior partial-coverage restorations. Prior to the advancements in adhesive technologies and ceramic materials, mechanical preparation to achieve retention and resistance was essential for the longevity of the restoration. Esthetic factors to minimize the appearance of margins and metal display determined
the preparation design for metal-based restorations. The biologic consequences of achieving these goals often were compromised health and structural integrity of the tooth and periodontal tissue. Subgingival margins and removal of excessive tooth structure to obtain required material thicknesses were necessary to obtain acceptable esthetic outcomes. The evolution of reliable adhesive cementation techniques and ceramic materials led to a major change in treatment philosophy. A significant paradigm shift in modern restorative dentistry has been observed over the last few years. Whereas restoration of the tooth structure was the primary emphasis in the past, reinforcement and preservation of the remaining dental tissues represent the major treatment aims in contemporary dentistry. Tooth preparation represents a balance between conserving tooth structure and preserving pulpal health while achieving an esthetic and fracture-resistant restoration (Fig 4-2). 53
4
Posterior Partial-Coverage Restorations: Inlays and Onlays
a
b
c Fig 4-3 Defect-oriented press-fabricated inlay and onlay restorations in mandibular molars. (a) Insufficient amalgam restorations. (b) Defect size after excavation of caries. (c) Composite restoration and defect-oriented inlay and onlay preparation design. (d) Press-fabricated inlay and onlay restorations (IPS e.max Press, surface staining technique). (e) Adhesively cemented (Variolink II) inlay and onlay restorations.
d
e
Inlay preparation design Various aspects of preparation design and its impact on the clinical success of ceramic inlays have been investigated extensively in the dental literature.36 The longevity of teeth restored with inlays is influenced by the following main factors within the preparation design: cavity depth, cavity isthmus width, preparation taper, and the morphology of internal line angles. Initially, preparation designs for posterior ceramic restorations evolved from recommendations made by G. V. Black (1836–1915) for cast metal and amalgam restorations, resulting in removal of considerable tooth structure. Today, cavity geometry and dimensions are dictated by the existing cavity (Figs 4-3 and 4-4), the properties of the restorative material, their applied fabrication technology, and the inherent shape of the caries lesion. The literature is conclusive with respect to the effects of extensive tooth preparation; it weakens the remaining tooth structure and increases the risk of fracture.37 Cavity depth has been reported as
54
the most crucial factors in the weakening of cusps, whereas the width of the isthmus alone is the least important factor.38,39 Based on the current literature, a depth of 1.5 mm to 2.0 mm is recommended to minimize removal of tooth structure and to provide a sufficient thickness of the restoration material to ensure adequate longevity.40 Several in vitro studies have showed that the fracture resistance of teeth can be related to the amount of tooth structure removed, and inlay-restored teeth showed a significantly higher fracture resistance than did teeth with onlay restorations.41,42 Adhesive cementation of inlays to teeth increases the fracture resistance of the tooth-restoration complex. However, extensive mesio-occlusodistal preparations can severely undermine cusps, which cannot be restored by adhesive cementation.43 Therefore minimizing the depth and overall width of inlay tooth preparations must be a primary concern. A narrow occlusal cavity with a width of one-third of the cusp-to-cusp distance and an occlusal minimum isthmus width of 2.5 mm to provide acceptable strength of the restorative material is most com-
Clinical Procedures
a
b
c
d
e
Fig 4-4 Defect-oriented CAD/CAM–fabricated inlay and onlay restorations in molars. (a) Insufficient amalgam restorations. (b) Composite resin restoration and defectoriented inlay preparation design. (c) Stereolithographicfabricated model based on digital scanning data (Cerec AC/Infinident, Sirona). (d) CAD/CAM–fabricated inlay restorations (Vita Mark II, Vident). (e) Adhesively cemented (Variolink II) inlay restorations.
monly suggested in the dental literature.44 If the minimal material thickness is not reached in the region of the isthmus, the treatment plan should be reconsidered, and a direct composite resin restoration might be the restoration of choice. Therefore, the preparation of the occlusal cavity and any proximal boxes should generally be defectoriented and as minimally invasive as possible.45 When teeth are compromised by larger structural defects, use of adhesively bonded core buildups is advisable. In this way, the unnecessary removal of overhangs can be avoided, and the subsequent preparation design can be performed to provide the optimum uniform thickness of the ceramic in all dimensions. Moreover, contamination is prevented because dentin sealing is achieved from the first session onward, which should lead to a long-term adhesive bond between dentin and the adhesive core material as well as reduced postinsertion sensitivity. To facilitate the try-in procedure and to minimize the risk of fracture of ceramic restorations, cavity wall preparation with an overall divergence of 6 degrees toward the occlusal
aspect is recommended.46 If the divergence between axial walls is smaller than 6 degrees, greater stress is imparted to the inlay and the likelihood for fracture is increased. The diamond instruments that are used for the preparation should have a correspondingly tapered design.45 Oscillating preparation instruments (for example, Sonic prep Ceram, Kavo) are a minimally invasive alternative to conventional inlay diamond burs. A complete separation is necessary to avoid damage to the contacts of the adjacent teeth. This extension is indispensable for both conventional and optical impression taking and adhesive cementation. Beveled margins should be avoided for all-ceramic restorations, because they will be prone to fracture failure. Therefore feather-edge margins, known from the traditional preparation design for cast restorations, are contraindicated for all-ceramic materials, particularly in the proximal area.47 In the replacement of amalgam restorations, defects are often extended beyond enamel into dentin. However, when rubber dam can be applied to prevent contamination dur55
4
Posterior Partial-Coverage Restorations: Inlays and Onlays ing adhesive cementation, indirect ceramic restorations with proximal margins in dentin are equally successful.48 It has been recommended that all internal line angles be rounded and prepared cusp tips be oriented perpendicular to the occlusal load in order to reduce stress within the tooth and all-ceramic restoration.49 Development of semispherical cavity floor segments and rounded cavity shapes50 and avoidance of edges and sharp transitions are suggested.51 Rounded diamond burs should be used to obtain rounded transitions from the occlusal cavity floor to the axial walls.45
Onlay and overlay preparation design Guidelines for the amount of tooth reduction for different types of partial-coverage restorations have evolved largely as a result of experience rather than scientific evidence. If the extent of the defect results in a cuspal wall thickness of 1.5 to 2.0 mm, a reduction of the respective cusp or respective cavity wall is recommended. Hence the mesioocclusodistal inlay cavity should be extended to an onlay partial-coverage restoration.52 Moreover the load applied to the remaining tooth structure during mastication with (abrasion) and without food (attrition) has to be considered. Dynamic occlusal contact on a preparation with compromised tooth structure should be avoided. Preparation of occlusal boxes is often claimed to achieve sufficient macroretention to facilitate provisional restoration and to ensure definite positioning of the definitive restoration.45 However, parallel-walled isthmus preparation is not required to improve retention, because it results in undesirable loss of tooth structure and impedes insertion that is free of mechanical stress. Preparation of butt-joint margins are commonly suggested in the dental literature, whereas a shoulder preparation on remaining cusps cannot be recommended.42 A significantly increased failure rate was observed with a shoulder preparation design.53 Cusps should be shortened when occlusal contacts in dynamic occlusion might cause flexural loading of the remaining tooth structure. If cusps are included in the preparation design it is essential to keep the occlusal surface rounded. Occlusal reduction should generally follow the occlusal anatomy. Minimal ceramic thicknesses ranging from 1.5 to 2.0 mm are recommended by most manufacturers.45,54 However these general material thickness requirements are mostly based on laboratory tests with questionable clinical relevance and limited scientific evidence.45 Augmented ceramic thicknesses with excessive tooth structure removal are recommended to prevent restoration failure caused by fracture.55 However, when extensive amounts of tooth 56
structure have already been compromised by caries, attrition, or erosion, preservation of the remaining tooth structure is most crucial.35 Direct correlation of strength degradation with increased tooth structure removal has been well documented in the literature.37 Moreover, cuspal stiffness is significantly impaired by cavity preparation.24,56 As a consequence, traditional restorative treatment concepts for posterior teeth often aimed to strengthen the tooth-restoration complex by extending preparation designs from inlay and partialcoverage onlay to complete-coverage onlay or crown restorations at the expense of the remaining tooth structure.57,58 Because of the weakness of extensively prepared teeth, fracture failures of these restorations are most commonly reported as catastrophic, involving the restoration and underlying tooth structure.59,60 Moreover tooth vitality may be jeopardized by these extensive complete-coverage crown preparation designs.61 Palatal onlay restorations with a reduced ceramic thickness of 1.0 and 0.5 mm exhibited significantly higher failure loads because the supporting tooth structure was predominately enamel, resulting in a high modulus of elasticity relative to dentin.62,63 In contrast, the palatal onlay preparation with standard thickness exposes predominately dentin, providing a support with a lower modulus of elasticity. This allows increased flexural tensile stresses to develop at the intaglio cementation surface during loading, putting the ceramic at higher risk of fracture.64 Minimally invasive occlusal onlay restorations showed a similar trend. This is in agreement with other studies, reporting that the fracture resistance of ceramic restorations bonded with resin to enamel was higher than that of ceramic restorations bonded to dentin.65,66 Cuspal coverage with partial- or complete-crown preparation is commonly recommended to protect the weakened tooth structure.58 However, in vitro studies have not revealed increased failure loads when the preparation geometry is extended from a palatal onlay to complete– occlusal onlay restorations.41,42,67–69 These findings were also confirmed by clinical investigations.53,70 The benefit of the onlay preparation design can be explained by the amount of the remaining tooth structure,71 which results in favorable distribution of stresses in teeth and thereby reduces the risk of fracture.72 When the abutment teeth have minimal or no preparation design, retention of the restoration predominately relies on adhesive technology with minimal mechanical assistance. Conservation of tooth structure—and thus reduction of the pulpal and periodontal consequences of extensive preparations—is the major advantage of this treatment concept.
CAD/CAM Procedures for All-Ceramic Partial-Coverage Restorations
Full-veneer preparation design Quantitative analyses of various preparation designs showed that the amount of tooth structure removed during onlay and partial-crown preparation configurations in posterior teeth could be reduced by more than 40% compared to complete-coverage crown preparation.71 Therefore, further preparation design modifications in the form of posterior full-veneer restorations with buccal surface coverage and chamfer margin have evolved.55 Extending the tooth preparation to include a buccal veneer component can be a viable clinical treatment option to provide excellent esthetics, color, and contour, especially when Class V lesions are present in posterior teeth. The amount of tooth structure removed ranges from 1.5 to 2.0 mm from the occlusal part and from 0.6 to 0.8 mm from the buccal aspect.73 However, recent publications have recommended a more conservative preparation design with a reduced thickness of 0.5 and 1.0 mm in the occlusal part23,63 (see Figs 4-1m to 4-1p). Thus, all-ceramic full-veneer restorations can be considered as an esthetic and minimally invasive alternative to conventional complete-coverage crowns.74
CAD/CAM Procedures for All-Ceramic Partial-Coverage Restorations The first computerized restoration system, Cerec (originally Siemens, now Sirona), was introduced almost 30 years ago. Several companies have developed and enhanced this con cept since then. Numerous systems are now available for use in both the dental office (chairside) and the dental laboratory5 and are discussed in detail in chapter 13. However, some comments regarding CAD for partial-coverage restorations are relevant to this chapter. The current computerbased techniques are capable of delivering a wide range of restorations, from inlays and veneers to multiunit fixed partial dentures, implant abutments, and implant-supported restorations. With either compact milling units for use in a dental office or industrial units in dedicated milling centers, each type of ceramic material can now be formed into restorations for almost all indications in restorative dentistry. With their Cerec line of products, Sirona provides both in-office and laboratory-based systems. With the earlier version Cerec 1 and Cerec 2, the clinician took an intraoral optical scan of the prepared tooth with a charge-coupled device camera. Based on these data, the system automatically generated a three-dimensional (3D) digital image on
the monitor. Subsequently the restoration was designed and milled. With the subsequent Cerec 3D system, multiple images could be recorded within seconds, enabling operators to prepare multiple teeth in the same quadrant and create a virtual cast for the entire quadrant. The restorations were then designed on the virtual model. Subsequently, the data were electronically transmitted to a remote milling unit for fabrication. With the introduction of the Cerec AC scanning unit and the Cerec Connect platform, the clinician can purchase a digital impression system without purchasing a milling unit. The Cerec AC uses blue light–emitting diode technology to scan the dentition. The system facilitates scanning procedures and does not require image captures from different angles, but the application of titanium dioxide scanning powder is mandatory. Most recently, the Cerec Omnicam camera was released. Video streaming is used to digitize the structures of the jaw in full color without the need for powder coating. The Cerec Omnicam is particularly indicated for more extensive treatments involving multiple restorations. With the laboratory-based Cerec InLab system, working dies are laser scanned, and a digital image of the virtual model is displayed on a computer screen. After designing the restoration, the laboratory technician inserts the appropriate block into the Cerec InLab machine for milling. Today, a wide range of ceramic blocks are available for the system, ranging from silicate ceramics to high-strength oxide ceramics. In vitro data showed that in-office fabricated all-ceramic restorations (Cerec 3D) were comparable with press-fabricated (IPS Empress) restorations with respect to their occlusal precision and time required for occlusal adjustments.75 CAD/CAM–fabricated all-ceramic partial-coverage restorations of earlier software versions (Cerec 3/InLab) resulted in limitations in the anatomical form when compared to press-fabricated restorations,76 but advancements in software development will most likely overcome this issue. The recently released Biogeneric software (Sirona) is able to create CAD/CAM partial-coverage restorations with natural occlusal morphology in a design process that is significantly faster than that of the earlier Cerec 3D software.77 The E4D (Evolution for Dentistry, E4D Technologies) is an in-office CAD/CAM system that was launched in 2003. With use of its high-speed intraoral digitizer (intraoral laser scanner) digital 3D impressions of the tooth preparation can be obtained without the use of reflective agents. The morphology of the intraoral situation is re-created by the software on the design station based on a collection of data points from multiple scans at various angles performed by the operator. The design center and milling unit allow the den57
4
Posterior Partial-Coverage Restorations: Inlays and Onlays tist to create inlays, onlays, veneers, and crowns in one appointment. With advancements in CAD software, multiple units can now be designed and fabricated with the Cerec and E4D systems. Moreover pre-prepared and diagnostic wax-up casts can be scanned and used as a template for the definitive restoration. Both in-office systems also allow the digital data set to be converted into a stereolithographic model for the creation of a master cast (Infinident, Sirona) so that any restoration can be manufactured with any fabrication technique and material.
Cementation of PartialCoverage Restorations The topic of cementation of high-strength ceramics is addressed in detail in chapter 9, but there are special considerations for this procedure with regard to partial-coverage restorations. A maximum thickness of 3 mm for the occlusal surface of the ceramic restoration and a maximum proximal vertical dimension of 6 mm are recommended as a reference in solely light-initiated polymerization of the adhesive and/ or luting composite resin. In this context the opacity of the applied ceramic is an important factor. The extent to which the filler content of luting composite resin influences the longevity of all-ceramic partial-coverage restorations is still a topic of controversy.78,79 The application of dual-cured high-viscosity luting cements is commonly recommended.80,81 Similarly, the clinical long-term effect of the polymerization mode of the luting composite has not yet been fully investigated. Studies indicate that decreases in the peripheral enamel seal and the enamel bonding surface have deleterious effects of the bonding interface between the restoration and the tooth over time.82 If the bonding interfaces have deteriorated, the ability of the bond to transfer stresses from the restoration to the tooth will be lessened. As a result of the ingress of water, a reduction of the bond durability can be expected.53 The bonding mechanism to dentin is more complicated than it is to enamel because of the complex histology and variable composition of dentin. Previous studies showed that the bond strength of the restoration to deep (peritubular) dentin substrates was significantly less than the bond to superficial (intertubular) dentin.83 However, in clinical studies, all-ceramic restorations in which parts of the
58
cervical margins were located in dentin showed a very low incidence of secondary caries in long-term observation periods of more than 15 years.53 In the early years of adhesively bonded ceramics, abrasion or erosion of the luting agent in the oral environment was considered as a high risk for failure over time. The resulting “marginal ditching” was observed in the majority of restorations during the first few years, especially at the occlusal margins. The luting composite resin at the margin of the restoration is exposed to wear by mastication. However, ditching at the margins has been reported to be selflimiting; it did not increase during the following years and did not result in any clinical problems.53,84,85 Although marginal deterioration and discoloration have been described as common phenomena in several clinical trials, they have not been considered critical for the clinical performance of all-ceramic restorations.53,63,70,81,86–96
Clinical Outcomes of All-Ceramic Partial-Coverage Restorations Clinical results of early all-ceramic inlay systems were not satisfactory. In response, the dental industry developed new ceramic materials (leucite- and lithium disilicate–reinforced glass-ceramics) and innovative fabrication techniques (pressable ceramics) as well as different CAD/CAM methods for the subtractive processing of industrially prefabricated dental ceramics. Presently, prospective clinical long-term studies are available for the treatment of posterior teeth with the leucite- reinforced glass-ceramic IPS Empress. The long-term success of this material in combination with adhesive cementation has been reported in observation periods of up to 15 years.53,70,97,98 High survival rates have also been described for chairside- fabricated inlays and onlays that were observed for 8,99 17,89 and 18 years.100 Therefore, there is scientific evidence to support the use of all-ceramic inlays generally and as restorations for the posterior region. Available long-term clinical data on all-ceramic partialcoverage restorations have revealed that ceramic bulk fracture is still the most common complication, despite the fact that ceramic thicknesses of at least 1.5 mm have been provided.55,92,101,102 However, low-strength all-ceramic materials, such as feldspathic or leucite-reinforced glass-ceramics, have been investigated in most of these studies.55,65,101,103 In addition, most of these ceramic fractures are easy to repair
References without destruction of healthy tooth structure, which adds further support for the conservative approach of the adhesive all-ceramic treatment technique.53 Whereas tooth fracture has been reported as the main reason for failure of treatment with amalgam restorations,104,105 this failure pattern is rare with adhesively cemented allceramic restorations.53 Advanced ceramic systems such as lithium disilicate glass-ceramics used for the fabrication of partial-coverage restorations have demonstrated increased fracture resistance.66 While short- to medium-term clinical data on lithium-disilicate restorations are very promising, longterm data are presently still sparse.76,106,107 A low frequency of secondary caries has been observed in adhesively cemented all-ceramic restorations in several studies.53,70 Only very limited information can be found in the dental literature on the treatment outcomes of restorations for patients with severely worn dentition.53,91 In the majority of clinical trials evaluating all-ceramic restorations, patients with parafunctional habits are excluded, which might favor the overall performance of indirect all-ceramic restorations. Parafunctional habits were identified as a significant predictor for failures of all-ceramic partial-coverage restorations.53,108 However, in a recent long-term clinical study, bruxers who were compliant with wearing an acrylic resin occlusal guard did not show an increased risk of failure of their cemented all-ceramic inlay and onlay restorations.91 The longevity of all-ceramic restorations with cuspal coverage in extended defects has been described in very few studies.53 The number of failures reported was low, and this modality has to be weighed against the risk involved in performing endodontic treatment and preparation for complete-coverage crown therapy to obtain adequate resistance and retention. In addition, the traditional treatment approach frequently calls for placement of a post and core in many of the cases to provide adequate macromechanical retention. The adhesive treatment approach allows for excellent esthetic outcomes and a higher frequency of supragingivally placed cervical margins with good adaptation and favorable periodontal tissue response.53 A higher failure rate for endodontically treated teeth compared to vital teeth has been well demonstrated in the literature for all-ceramic inlay, onlay, and full-veneer restorations.53,81,91 Endodontically treated teeth generally have more compromised retention than do vital teeth. Moreover, a higher probability of bond failures has been described for nonvital endodontically treated teeth after a long intraoral period.108
Conclusion Esthetic demands and restorative needs in anterior and posterior teeth have changed dramatically within recent decades. All-ceramic materials and CAD/CAM technologies are increasingly used in prosthetic dentistry. The paradigm shift in fixed prosthodontics from traditional approaches to minimally invasive treatments is evidenced by the clinical long-term success of bonded glass-ceramic restorations. Modern all-ceramic materials deliver superior esthetics and reliability, as shown by contemporary material science. Advancements in all-ceramic systems and adhesive technologies enable the development of innovative defect-oriented treatment concepts for restoring the compromised dentition. The geometries of modified onlay and full-veneer preparations have evolved and form a reliable alternative for conventional full-coverage crowns. Nowadays, non retentive preparation designs used in combination with reduced ceramic thicknesses allow for a minimally invasive treatment approach.
References 1. Denry I, Holloway JA. Ceramics for dental applications: A review. Materials 2010;3:351–68. 2. Höland W, Schweiger M, Watzke R, Peschke A, Kappert H. Ceramics as biomaterials for dental restoration. Expert Rev Med Devices 2008;5:729–745. 3. Della Bona A, Kelly JR. The clinical success of all-ceramic restorations. J Am Dent Assoc 2008;139(suppl):8S–13S. 4. Denissen H, Dozic A, van der Zel J, van Waas M. Marginal fit and short-term clinical performance of porcelain-veneered CICERO, CEREC, and Procera onlays. J Prosthet Dent 2000;84:506–513. 5. Miyazaki T, Hotta Y, Kunii J, Kuriyama S, Tamaki Y. A review of dental CAD/CAM: Current status and future perspectives from 20 years of experience. Dent Mater J 2009;28:44–56. 6. O’Brien WJ. Dental porcelains: An outline of dental materials and their chemistry. In: O’Brian WJ, Ryge GWB (eds). An Outline of Dental Materials and Their Selection. Philadelphia: Saunders, 1978. 7. Bottino MA, Salazar-Marocho SM, Leite FP, Vásquez VC, Valandro LF. Flexural strength of glass-infiltrated zirconia/alumina-based ceramics and feldspathic veneering porcelains. J Prosthodont 2009; 18:417–420. 8. Giordano RA 2nd, Pelletier L, Campbell S, Pober R. Flexural strength of an infused ceramic, glass ceramic, and feldspathic porcelain. J Prosthet Dent 1995;73:411–418. 9. Seghi RR, Daher T, Caputo A. Relative flexural strength of dental restorative ceramics. Dent Mater 1990;6:181–184. 10. Höland W, Frank M, Rheinberger V. Surface crystallization of leucite in glasses. J Non-Cryst Sol 1995;180:292–307. 11. Taylor D, Henderson C. Thermal expansion of the leucite group of minerals. Am Min 1968;53:1476–1489. 12. Cattell MJ, Clarke RL, Lynch EJ. The biaxial flexural strength and reliability of four dental ceramics. 2. J Dent 1997;25:409–414. 13. Fischer J, Stawarczyk B, Hämmerle CH. Flexural strength of veneering ceramics for zirconia. J Dent 2008;36:316–321. 14. Szabo I, Barnab S, Völksch G, Höland W. Crystallization and color of apatite-leucite glass-ceramic. Glastech Ber Glass Sci Technol 2000; 73(C1):354–357.
59
4
Posterior Partial-Coverage Restorations: Inlays and Onlays 15. Cesar PF, Soki FN, Yoshimura HN, Gonzaga CC, Styopkin V. Influence of leucite content on slow crack growth of dental porcelains. Dent Mater 2008;24:1114–1122. 16. Aboushelib MN, Kleverlaan CJ, Feilzer AJ. Microtensile bond strength of different components of core veneered all-ceramic restorations. 2. Zirconia veneering ceramics. Dent Mater 2006;22:857– 863. 17. Denry I, Rosenstiel SF. Phase transformation in feldspathic dental porcelains. In: Fischman G, Clare A, Hench L (eds). Bioceramics: Materials and Applications. Westerville, OH: The American Ceramic Society, 1995:149–156. 18. Albakry M, Guazzato M, Swain MV. Influence of hot pressing on the microstructure and fracture toughness of two pressable dental glass-ceramics. J Biomed Mater Res B Appl Biomater 2004;71:99– 107. 19. Dong JK, Luthy H, Wohlwend A, Schärer P. Heat-pressed ceramics: Technology and strength. Int J Prosthodont 1992;5:9–16. 20. Höland W, Apel E, van’t Hoen C, Rheinberger V. Studies of crystal phase formation in the early stage crystallization of lithium disilicate glass-ceramics. J Non-Cryst Solids 2006;352:4041–4050. 21. Höland W, Schweiger M, Frank M, Rheinberger V. A comparison of the microstructure and properties of the IPS Empress 2 and the IPS Empress glass-ceramics. J Biomed Mater Res 2000;53:297–303. 22. Wiedhahn K. From blue to white: New high-strength material for Cerec—IPS e.max CAD LT. Int J Comput Dent 2007;10:79–91. 23. Schlichting LH, Maia HP, Baratieri LN, Magne P. Novel-design ultrathin CAD/CAM composite resin and ceramic occlusal veneers for the treatment of severe dental erosion. J Prosthet Dent 2011; 105:217–226. 24. Magne P, Belser UC. Porcelain versus composite inlays/onlays: Effects of mechanical loads on stress distribution, adhesion, and crown flexure. Int J Periodontics Restorative Dent 2003;23: 543–555. 25. Ragauska A, Apse P, Kasjanovs V, Berzina-Cimdina L. Influence of ceramic inlays and composite fillings on fracture resistance of premolars in vitro. Stomatologija 2008;10:121–126. 26. Vanoorbeek S, Vandamme K, Lijnen I, Naert I. Computer-aided designed/computer-assisted manufactured composite resin versus ceramic single-tooth restorations: A 3-year clinical study. Int J Prosthodont 2010;23:223–230. 27. Van’t Spijker A, Rodriguez JM, Kreulen CM, et al. Prevalence of tooth wear in adults. Int J Prosthodont 2009;22:35–42. 28. Lussi A, Jaeggi T. Erosion—Diagnosis and risk factors. Clin Oral Investig 2008;12(suppl 1):S5–S13. 29. Lavigne GJ, Khoury S, Abe S, Yamaguchi T, Raphael K. Bruxism physiology and pathology: An overview for clinicians. J Oral Rehabil 2008;35:476–494. 30. Lussi A, Hellwig E, Zero D, Jaeggi T. Erosive tooth wear diagnosis, risk factors and prevention. Am J Dent 2006;19:319–325. 31. Wang X, Lussi A. Assessment and management of dental erosion. Dent Clin North Am 2010;54:565–578. 32. Vailati F, Belser UC. Full-mouth adhesive rehabilitation of a severely eroded dentition: The three-step technique. 3. Eur J Esthet Dent 2008;3:236–257. 33. Vailati F, Belser UC. Full-mouth adhesive rehabilitation of a severely eroded dentition: The three-step technique. 2. Eur J Esthet Dent 2008;3:128–146. 34. Vailati F, Belser UC. Full-mouth adhesive rehabilitation of a severely eroded dentition: The three-step technique. 1. Eur J Esthet Dent 2008;3:30–44. 35. Jaeggi T, Grüninger A, Lussi A. Restorative therapy of erosion. Monogr Oral Sci 2006;20:200–214. 36. Milleding P, Ortengren U, Karlsson S. Ceramic inlay systems: Some clinical aspects. J Oral Rehabil 1995;22:571–580. 37. St-Georges AJ, Sturdevant JR, Swift EJ Jr, Thompson JY. Fracture resistance of prepared teeth restored with bonded inlay restorations. J Prosthet Dent 2003;89:551–557. 38. Khera SC, Goel VK, Chen RC, Gurusami SA. Parameters of MOD cavity preparations: A 3-D FEM study. 2. Oper Dent 1991;16:42–54.
60
39. Lin CL, Chang CH, Ko CC. Multifactorial analysis of an MOD restored human premolar using auto-mesh finite element approach. J Oral Rehabil 2001;28:576–585. 40. Thompson MC, Thompson KM, Swain M. The all-ceramic, inlay supported fixed partial denture. 1. Ceramic inlay preparation design: A literature review. Aust Dent J 2010;55:120–127. 41. Habekost Lde V, Camacho GB, Pinto MB, Demarco FF. Fracture resistance of premolars restored with partial ceramic restorations and submitted to two different loading stresses. Oper Dent 2006; 31:204–211. 42. Stappert CF, Guess PC, Gerds T, Strub JR. All-ceramic partial coverage premolar restorations. Cavity preparation design, reliability and fracture resistance after fatigue. Am J Dent 2005;18:275–280. 43. Ban S, Anusavice KJ. Influence of test method on failure stress of brittle dental materials. J Dent Res 1990;69:1791–1799. 44. Jackson RD, Ferguson RW. An esthetic, bonded inlay/onlay technique for posterior teeth. Quintessence Int 1990;21:7–12. 45. Ahlers MO, Mörig G, Blunck U, et al. Guidelines for the preparation of CAD/CAM ceramic inlays and partial crowns. Int J Comput Dent 2009;12:309–325. 46. Esquivel-Upshaw JF, Anusavice KJ, Yang MC, Lee RB. Fracture resistance of all-ceramic and metal-ceramic inlays. Int J Prosthodont 2001;14:109–114. 47. Fradeani M, Barducci G. Versatility of IPS Empress restorations. 2. Veneers, inlays, and onlays. J Esthet Dent 1996;8:170–176. 48. Krämer N, Frankenberger R. Clinical performance of bonded leucitereinforced glass ceramic inlays and onlays after eight years. Dent Mater 2005;21:262–271. 49. Couegnat G, Fok SL, Cooper JE, Qualtrough AJ. Structural optimization of dental restorations using the principle of adaptive growth. Dent Mater 2006;22:3–12. 50. Arnetzl GV, Arnetzl G. Biomechanical examination of inlay geometries—Is there a basic biomechanical principle? Int J Comput Dent 2009;12:119–130. 51. McDonald A. Preparation guidelines for full and partial coverage ceramic restorations. Dent Update 2001;28:84–90. 52. Mehl A, Kunzelmann KH, Folwaczny M, Hickel R. Stabilization effects of CAD/CAM ceramic restorations in extended MOD cavities. J Adhes Dent 2004;6:239–245. 53. van Dijken JW, Hasselrot L. A prospective 15-year evaluation of extensive dentin-enamel-bonded pressed ceramic coverages. Dent Mater 2010;26:929–939. 54. Tsitrou EA, van Noort R. Minimal preparation designs for single posterior indirect prostheses with the use of the Cerec system. Int J Comput Dent 2008;11:227–240. 55. Murgueitio R, Bernal G. Three-year clinical follow-up of posterior teeth restored with leucite-reinforced IPS empress onlays and partial veneer crowns. J Prosthodont 2012;21:340–345. 56. Magne P, Knezevic A. Influence of overlay restorative materials and load cusps on the fatigue resistance of endodontically treated molars. Quintessence Int 2009;40:729–737. 57. Dejak B, Mlotkowski A, Romanowicz M. Strength estimation of different designs of ceramic inlays and onlays in molars based on the Tsai-Wu failure criterion. J Prosthet Dent 2007;98:89–100. 58. Kuijs RH, Fennis WM, Kreulen CM, et al. A comparison of fatigue resistance of three materials for cusp-replacing adhesive restorations. J Dent 2006;34:19–25. 59. Beier US, Kapferer I, Dumfahrt H. Clinical long-term evaluation and failure characteristics of 1,335 all-ceramic restorations. Int J Prosthodont 2012;25:70–78. 60. Stokes AN, Hood JA. Impact fracture characteristics of intact and crowned human central incisors. J Oral Rehabil 1993;20:89–95. 61. Valderhaug J, Jokstad A, Ambjørnsen E, Norheim PW. Assessment of the periapical and clinical status of crowned teeth over 25 years. J Dent 1997;25:97–105. 62. Habelitz S, Marshall SJ, Marshall GW Jr, Balooch M. Mechanical properties of human dental enamel on the nanometre scale. Arch Oral Biol 2001;46:173–183. 63. Craig RG, Peyton FA. Elastic and mechanical properties of human dentin. J Dent Res 1958;37:710–718.
References 64. Piemjai M, Arksornnukit M. Compressive fracture resistance of porcelain laminates bonded to enamel or dentin with four adhesive systems. J Prosthodont 2007;16:457–464. 65. Clausen JO, Abou Tara M, Kern M. Dynamic fatigue and fracture resistance of non-retentive all-ceramic full-coverage molar restorations. Influence of ceramic material and preparation design. Dent Mater 2010;26:533–538. 66. Soares CJ, Martins LR, Fonseca RB, Correr-Sobrinho L, Fernandes Neto AJ. Influence of cavity preparation design on fracture resistance of posterior Leucite-reinforced ceramic restorations. J Prosthet Dent 2006;95:421–429. 67. Morimoto S, Vieira GF, Agra CM, Sesma N, Gil C. Fracture strength of teeth restored with ceramic inlays and overlays. Braz Dent J 2009;20:143–148. 68. Cubas GB, Habekost L, Camacho GB, Pereira-Cenci T. Fracture resistance of premolars restored with inlay and onlay ceramic restorations and luted with two different agents. J Prosthodont Res 2011;55:53–59. 69. Frankenberger R, Taschner M, Garcia-Godoy F, Petschelt A, Krämer N. Leucite-reinforced glass ceramic inlays and onlays after 12 years. J Adhes Dent 2008;10:393–398. 70. Edelhoff D, Sorensen JA. Tooth structure removal associated with various preparation designs for posterior teeth. Int J Periodontics Restorative Dent 2002;22:241–249. 71. Mondelli J, Steagall L, Ishikiriama A, de Lima Navarro MF, Soares FB. Fracture strength of human teeth with cavity preparations. J Prosthet Dent 1980;43:419–422. 72. Blair FM, Wassell RW, Steele JG. Crowns and other extra-coronal restorations: Preparations for full veneer crowns. Br Dent J 2002; 192:561–564, 567–571. 73. Christensen GJ. Considering tooth-colored inlays and onlays versus crowns. J Am Dent Assoc 2008;139:617–620. 74. Reich S, Brungsberg B, Teschner H, Frankenberger R. The occlusal precision of laboratory versus CAD/CAM processed all-ceramic crowns. Am J Dent 2010;23:53–56. 75. Guess PC, Selz CF, Steinhart YN, Stampf S, Strub JR. Prospective clinical split-mouth study of pressed and CAD/CAM all-ceramic partial-coverage restorations: 7-years results. Int J Prosthodont 2013;26:21–25. 76. Ender A, Mörmann WH, Mehl A. Efficiency of a mathematical model in generating CAD/CAM-partial crowns with natural tooth morphology. Clin Oral Investig 2011;15:283–289. 77. Frankenberger R, Petschelt A, Krämer N. Leucite-reinforced glass ceramic inlays and onlays after six years: Clinical behavior. Oper Dent 2000;25:459–465. 78. Hahn P, Attin T, Gröfke M, Hellwig E. Influence of resin cement viscosity on microleakage of ceramic inlays. Dent Mater 2001;17:191– 196. 79. Santos MJ, Mondelli RF, Francischone CE, Lauris JR, de Lima NM. Clinical evaluation of ceramic inlays and onlays made with two systems: A one-year follow-up. J Adhes Dent 2004;6:333–338. 80. Stoll R, Cappel I, Jablonski-Momeni A, Pieper K, Stachniss V. Survival of inlays and partial crowns made of IPS Empress after a 10year observation period and in relation to various treatment parameters. Oper Dent 2007;32:556–563. 81. Abdalla AI, Feilzer AJ. Four-year water degradation of a total-etch and two self-etching adhesives bonded to dentin. J Dent 2008;36: 611–617. 82. Marques de Melo R, Galhano G, Barbosa SH, et al. Effect of adhesive system type and tooth region on the bond strength to dentin. J Adhes Dent 2008;10:127–133. 83. van Dijken JW, Höglund-Aberg C, Olofsson AL. Fired ceramic inlays: A 6-year follow up. J Dent 1998;26:219–225. 84. van Dijken JW, Hasselrot L, Ormin A, Olofsson AL. Restorations with extensive dentin/enamel-bonded ceramic coverage. A 5-year followup. Eur J Oral Sci 2001;109:222–229. 85. Molin MK, Karlsson SL. A randomized 5-year clinical evaluation of 3 ceramic inlay systems. Int J Prosthodont 2000;13:194–200.
86. Thordrup M, Isidor F, Hörsted-Bindslev P. A prospective clinical study of indirect and direct composite inlays: Ten-year results. Quintessence Int 2006;37:139–144. 87. Santos MJ, Mondelli RF, Navarro MF, Francischone CE, Rubo JH, Santos GC Jr. Clinical evaluation of ceramic inlays and onlays fabricated with two systems: Five-year follow-up. Oper Dent 2013;38:3– 11. 88. Otto T, Schneider D. Long-term clinical results of chairside Cerec CAD/CAM inlays and onlays: A case series. Int J Prosthodont 2008;21:53–59. 89. Roggendorf MJ, Kunzi B, Ebert J, Roggendorf HC, Frankenberger R, Reich SM. Seven-year clinical performance of CEREC-2 all-ceramic CAD/CAM restorations placed within deeply destroyed teeth. Clin Oral Investig 2012;16:1413–1424. 90. Beier US, Kapferer I, Burtscher D, Giesinger JM, Dumfahrt H. Clinical performance of all-ceramic inlay and onlay restorations in posterior teeth. Int J Prosthodont 2012;25:395–402. 91. Naeselius K, Arnelund CF, Molin MK. Clinical evaluation of allceramic onlays: A 4-year retrospective study. Int J Prosthodont 2008;21:40–44. 92. Galiatsatos AA, Bergou D. Six-year clinical evaluation of ceramic inlays and onlays. Quintessence Int 2008;39:407–412. 93. Felden A, Schmalz G, Hiller KA. Retrospective clinical study and survival analysis on partial ceramic crowns: Results up to 7 years. Clin Oral Investig 2000;4:199–205. 94. Murgueitio R, Bernal G. Three-year follow-up of posterior teeth restored with leucite-reinforced IPS Empress onlays and partial veneer crowns. J Prosthodont 2012;21:340–345. 95. Federlin M, Hiller KA, Schmalz G. Controlled, prospective clinical split-mouth study of cast gold vs. ceramic partial crowns: 5.5 year results. Am J Dent 2010;23:161–167. 96. Krämer N, Frankenberger R. Leucite-reinforced glass ceramic inlays after six years: Wear of luting composites. Oper Dent 2000;25:466– 472. 97. El-Mowafy O, Brochu JF. Longevity and clinical performance of IPSEmpress ceramic restorations—A literature review. J Can Dent Assoc 2002;68:233–237. 98. Pallesen U, van Dijken JW. An 8-year evaluation of sintered ceramic and glass ceramic inlays processed by the Cerec CAD/CAM system. Eur J Oral Sci 2000;108:239–246. 99. Reiss B. Clinical results of Cerec inlays in a dental practice over a period of 18 years. Int J Comput Dent 2006;9:11–22. 100. Felden A, Schmalz G, Federlin M, Hiller KA. Retrospective clinical investigation and survival analysis on ceramic inlays and partial ceramic crowns: Results up to 7 years. Clin Oral Investig 1998;2:161– 167. 101. Arnelund CF, Johansson A, Ericson M, Häger P, Fyrberg KA. Fiveyear evaluation of two resin-retained ceramic systems: A retrospective study in a general practice setting. Int J Prosthodont 2004; 17:302–306. 102. Smales RJ, Etemadi S. Survival of ceramic onlays placed with and without metal reinforcement. J Prosthet Dent 2004;91:548–553. 103. Plasmans PJ, Creugers NH, Mulder J. Long-term survival of extensive amalgam restorations. J Dent Res 1998;77:453–460. 104. Opdam NJ, Bronkhorst EM, Roeters JM, Loomans BA. A retrospective clinical study on longevity of posterior composite and amalgam restorations. Dent Mater 2007;23:2–8. 105. Guess PC, Strub JR, Steinhart N, Wolkewitz M, Stappert CF. Allceramic partial coverage restorations—Midterm results of a 5-year prospective clinical split mouth study. J Dent 2009;37:627–637. 106. Tagtekin DA, Ozyöney G, Yanikoglu F. Two-year clinical evaluation of IPS Empress II ceramic onlays/inlays. Oper Dent 2009;34:369–378. 107. Aberg CH, van Dijken JW, Olofsson AL. Three-year comparison of fired ceramic inlays cemented with composite resin or glass ionomer cement. Acta Odontol Scand 1994;52:140–149. 108. Van Nieuwenhuysen JP, D’Hoore W, Carvalho J, Qvist V. Long-term evaluation of extensive restorations in permanent teeth. J Dent 2003;31:395–405.
61