Clinical performance of CEREC ceramic inlays: a systematic review

Interdisciplinary Delphi study by PROSEC North America: Recommendations on single indirect restorations made from ceramic and nonmetallic biomaterials for posterior teeth

OBJECTIVE

This article puts forward consensus recommendations from PROSEC North America regarding single indirect restorations made from ceramic and nonmetallic biomaterials in posterior teeth.

OVERVIEW

The consensus process involved a multidisciplinary panel and three consensus workshops. A systematic literature review was conducted across five databases to gather evidence. The recommendations, informed by findings from systematic reviews and formulated based on a two-phase e-Delphi survey, emphasize a comprehensive treatment strategy that includes noninvasive measures alongside restorative interventions for managing dental caries and tooth wear. The recommendations advocate for selecting between direct and indirect restorations on a case-by-case basis, favoring inlays and onlays over crowns to align with minimally invasive dentistry principles. The recommendations highlight the critical role of selecting restorative biomaterials based on clinical performance, esthetic properties, and adherence to manufacturer guidelines. They emphasize the importance of precision in restorative procedures, including tooth preparation, impression taking, contamination control, and luting. Regular follow-up and maintenance tailored to individual patient needs are crucial for the longevity of ceramic and nonmetallic restorations.

CONCLUSIONS

These PROSEC recommendations provide a framework for dental practitioners to deliver high-quality restorative care, advocating for personalized treatment planning and minimally invasive approaches to optimize oral health outcomes.

CLINICAL SIGNIFICANCE

The PROSEC North America recommendations highlight the importance of minimally invasive techniques in posterior tooth restorations using ceramic and non-metallic biomaterials. These principles prioritize tooth structure conservation and personalized treatment planning, essential for enhancing clinical outcomes and long-term oral health.

Appropriate Immediate Dentin Sealing to Improve the Bonding of CAD/CAM Ceramic Crown Restorations

This study aimed to use quantitative and qualitative evaluations based on micro-tensile bond strength (μTBS) to clarify the appropriate immediate dentin sealing (IDS) approach for improving the bonding of CAD/CAM ceramic crown restorations. Forty-eight extracted human molars were prepared to obtain standardized abutment specimens and divided into three groups: no IDS (group C: control), IDS performed by a single application of an all-in-one adhesive system (group A), and IDS performed by the combined application of an adhesive system and a flowable resin composite (group F). All specimens were restored with a ceramic crown fabricated by a chair-side CAD/CAM system and were divided into no-stress and stressed groups. After cyclic loading (78.5 N; total, 3 × 105 cycles; 90 cycles/min) on the specimens in the stressed group, all specimens were sectioned. The μTBS values for the occlusal and mesioaxial walls were measured (n = 16) and analyzed statistically. The quantitative bonding performance of groups A and F were superior to that of group C, regardless of the cyclic loading and abutment wall conditions. Group F showed the maximum bond strength and the highest bond durability in the qualitative bonding performance even under the cyclic loading condition simulating clinical mastication.

Influence of different base materials and thicknesses on the fracture resistance of endocrown: A three-dimensional finite element analysis

INTRODUCTION

To analyze the stress distribution of the all-ceramic endocrown with different base materials and thicknesses using three-dimensional finite element analysis.

METHODS

A endodontically treated maxillary premolar was scanned by micro-CT, a three-dimensional finite element model of the endocrown with fluid resin as the base material was divided into control (0 mm), 1 mm, 2 mm, and 3 mm groups according to base thickness. Three kinds of conventional base materials were used and divided into glass ion group (A), fluid resin group (B), and nanocomposite resin group (C), and a three-dimensional finite element model of the endocrown with 1.0 mm thickness of base was established. A static loading with axial and 45° direction was applied to each model, the stress distribution of each part of the endocrown was analyzed under different base materials and thicknesses.

RESULTS

The different thickness of the base layer has an influence on the components of the restoration and the tooth. The stress in the control group was the largest. The stress was the lowest when the thickness of the base layer was 1 mm; The maximum of the equivalent stress, the first, second, and third principal stress in the endocrown, abutment, and alveolar bone, are basically the same with the different base materials. The stress on the base layer increases with the elastic modulus of base materials increases.

CONCLUSIONS

The base layer played a force buffering effect on the dental body restored with endocrowns, and the effect was the best at 1 mm; The selection of base material has little influence on the whole, but in order to protect the weak tissues of the cavity bottom, the base material with lower elastic modulus can be used.

The effect of space setting values and restorative block materials on the bonding of metal-free CAD/CAM onlay restorations

The effects of space setting values and restorative materials on the bonding of metal-free CAD/CAM onlay restoration were examined quantitatively and qualitatively. Seventy-two standardized MODB onlay cavities, prepared using human molars were restored under nine conditions, based on three space setting values, Increased (IC), Standard (SC, control), Decreased (DC), and three restorative block materials, resin-composites (RC), lithium disilicate glass-ceramics (LD), Feldspar ceramics (FC, control). All the restored specimens were subjected to cyclic loading and thereafter the microtensile bond strength (µ-TBS) was measured and analyzed statistically. The effect of space setting value on the µ-TBS varied with the restorative material. The bonding reliability of RC and the bonding durability of LD were significantly superior to FC. The bonding characteristics of RC under IC and DC were similar to those under SC. LD under DC and FC under IC were effective in obtaining an excellent bonding reliability relative to their SC.

A clinical evaluation of resin nanoceramic CEREC Omnicam restorations associated with several factors

PURPOSE

The aim of this study was to assess the clinical performance of computer-aided design and computer-aided manufacturing resin nanoceramic posterior restorations fabricated by CEREC Omnicam system.

MATERIALS AND METHODS

Fifty-seven Lava Ultimate posterior restorations were placed in 44 patients by one operator. Restorations were cemented using a resin cement system (Duo-Link). The clinical performance of the restorations was evaluated with USPHS guidelines in a mean time of 45-month. Data were statistically analyzed using Kaplan-Meier and Log Rank (Mantel-Cox) tests (SPSS 22.0, α = 0.05).

RESULTS

Thirty-eight restorations in 26 patients were evaluated at recall examinations by two evaluators other than the clinician who had placed the restorations who were blinded to groups. The survival rates of Lava Ultimate were 86.8%. A total of 5 (13.2%) failures were found. After a mean time of 45-month survival rate of vital and non-vital teeth were 90 and 83.3% respectively. The failures were not significantly influenced by gender, tooth arch, restoration size, the treated region and vitality.

CONCLUSION

Chair-side posterior resin nanoceramic restorations were clinically successful restorations with a survival rate of 86.8% after a mean time of 45-month.

CLINICAL SIGNIFICANCE

Chair-side CAD/CAM resin nanoceramic restorations can be a successful choice for vital and non-vital teeth with acceptable survival rates.

Survival of Cast Gold and Ceramic Onlays Placed in a School of Dentistry: A Retrospective Study

PURPOSE

This study was done to compare the survival rates of cast gold and ceramic onlays placed in a dental school setting.

MATERIAL AND METHODS

An electronic search was conducted in the patient records at Adams School of Dentistry, University of North Carolina at Chapel Hill for onlay codes that were in the database (From 1998 until 2018). Progress notes and radiographs were scrutinized to establish the survival time of the restorations. Any complications that occurred during the life time of the restorations were noted. The survival was summarized by categorization based on ranges of survival time in years; group 1: 1 to 5 years, group 2: 6 to 22 years. The mean survival time and standard deviation were calculated. One-way ANOVA was used to determine whether there was a statistically significant difference in the survival times between gold and ceramic onlays.

RESULTS

The mean survival rate of cast gold onlays (86.6%) was comparable to that of ceramic onlays (81.1%). The gold onlays in Group 1 had a higher mean survival time (2.43 years) than the ceramic onlays (2.03 years). This difference was statistically significant (p = 0.002). The ceramic onlays in Group 2 had a mean survival time of 19.75 years while gold onlays had a mean survival time of 17.63 years. This difference was not statistically significant (p = 0.91).

CONCLUSION

It was concluded that while the survival rate of ceramic onlays (81.1%) was inferior to that of cast gold onlays (86.6%), it was comparable.

Effect of immediate dentin sealing applications on bonding of CAD/CAM ceramic onlay restoration

The effects of immediate dentin sealing (IDS) applications on the bonding of computer-aided design/computer-aided manufacturing (CAD/CAM) ceramic onlay restorations after cyclic loading were examined. Standardized mesial-distal-occlusal-palatal cavities in 32 extracted human molars were prepared. The cavities were divided into four groups: those receiving thin-layered (T), slope-shaped (S), and base-shaped (B) sealing, and the non-sealing group (N) as a control. The intra-cavity dentin walls of the T, S, and B groups were sealed with an all-in-one adhesive and a flowable composite. All cavities were scanned; hence, CAD/CAM onlays were fabricated using ceramic blocks and bonded with a resin cement system. Cyclic loading was applied and the microtensile bond strength (μ-TBS) was measured. It was found that IDS application improved not only the μ-TBS, but also the bonding reliability and durability of the CAD/CAM restoration. In particular, the S restoration exhibited the highest-performance as regards both robust bond strength and stable bonding.

Clinical Evaluation of Indirect Particle-Filled Composite Resin CAD/CAM Partial Crowns after 24 Months

PURPOSE

Resin-based CAD/CAM compound materials might be promising for single-tooth restorations. Insufficient clinical data are available for this new material class. The purpose of this study was to describe initial clinical in vivo results for indirect particle-filled composite resin CAD/CAM restorations after 24 months.

MATERIALS AND METHODS

Indirect particle-filled composite resin restorations were fabricated with a CAD/CAM method (CEREC Bluecam intraoral scanner, CEREC MCXL milling unit) by calibrated dental students. Forty-two partial crown restorations were seated adhesively in 30 patients with caries lesions or insufficient restorations (baseline). Strict inclusion criteria were defined for the patient collective. Follow-up evaluation comprised 40 restorations after 12 months and 33 restorations after 24 months. Evaluation criteria were modified FDI criteria with grades (1) to (5). Rating with FDI criteria (5) was defined as clinical failure. Statistical analysis was performed with Wilcoxon-Test (p < 0.05).

RESULTS

The success rate of indirect particle-filled composite resin CAD/CAM restorations after 12 months was 95.0% with two debondings observed. The cumulative success rate for indirect particle-filled composite resin CAD/CAM restorations after 24 months was 85.7% with two tooth fractures and one debonding. Statistically significant differences were found for baseline and 24-month follow-up evaluation for anatomic form and marginal adaptation criterion examined in respect to FDI criteria guidelines (Wilcoxon-Test, p < 0.05).

CONCLUSIONS

This study demonstrates particle-filled composite resin CAD/CAM restorations having a clinical success rate of 85.7% after 24 months. Adhesive bonding procedures need to be ensured carefully. A longer clinical evaluation period is necessary to draw further conclusions.

Survival Rate of Resin and Ceramic Inlays, Onlays, and Overlays: A Systematic Review and Meta-analysis

This systematic review and meta-analysis aimed to evaluate the survival rate of ceramic and resin inlays, onlays, and overlays and to identify the complication types associated with the main clinical outcomes. Two reviewers searched PubMed, EMBASE, and the Cochrane Central Register of Controlled Trials for articles published between 1983 through April 2015, conforming to Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines for systematic reviews. Clinical studies meeting the following criteria were included: 1) studies related to resin and ceramic inlays, onlays, and overlays; 2) prospective, retrospective, or randomized controlled trials conducted in humans; 3) studies with a dropout rate of less than 30%; and 4) studies with a follow-up longer than 5 y. Of 1,389 articles, 14 met the inclusion criteria. The meta-regression indicated that the type of ceramic material (feldspathic porcelain vs. glass-ceramic), study design (retrospective vs. prospective), follow-up time (5 vs. 10 y), and study setting (university vs. private clinic) did not affect the survival rate. Estimated survival rates for glass-ceramics and feldspathic porcelain were between 92% and 95% at 5 y (n = 5,811 restorations) and were 91% at 10 y (n = 2,154 restorations). Failures were related to fractures/chipping (4%), followed by endodontic complications (3%), secondary caries (1%), debonding (1%), and severe marginal staining (0%). Odds ratios (95% confidence intervals) were 0.19 (0.04 to 0.96) and 0.54 (0.17 to 1.69) for pulp vitality and type of tooth involved (premolars vs. molars), respectively. Ceramic inlays, onlays, and overlays showed high survival rates at 5 y and 10 y, and fractures were the most frequent cause of failure.

Bonding values of two contemporary ceramic inlay materials to dentin following simulated aging

PURPOSE

To compare the push-out bond strength of feldspar and zirconia-based ceramic inlays bonded to dentin with different resin cements following simulated aging.

MATERIALS AND METHODS

Occlusal cavities in 80 extracted molars were restored in 2 groups (n=40) with CAD/CAM feldspar (Vitablocs Trilux forte) (FP) and zirconia-based (Ceramill Zi) (ZR) ceramic inlays. The fabricated inlays were luted in 2 subgroups (n=20) with either etch-and-bond (RelyX Ultimate Clicker) (EB) or self-adhesive (RelyX Unicem Aplicap) (SA) resin cement. Ten inlays in each subgroup were subjected to 3,500 thermal cycles and 24,000 loading cycles, while the other 10 served as control. Horizontal 3 mm thick specimens were cut out of the restored teeth for push out bond strength testing. Bond strength data were statistically analyzed using 1-way ANOVA and Tukey's comparisons at α=.05. The mode of ceramic-cement-dentin bond failure for each specimen was also assessed.

RESULTS

No statistically significant differences were noticed between FP and ZR bond strength to dentin in all subgroups (ANOVA, P=.05113). No differences were noticed between EB and SA (Tukey's, P>.05) bonded to either type of ceramics. Both adhesive and mixed modes of bond failure were dominant for non-aged inlays. Simulated aging had no significant effect on bond strength values (Tukey's, P>.05) of all ceramic-cement combinations although the adhesive mode of bond failure became more common (60-80%) in aged inlays.

CONCLUSION

The suggested cement-ceramic combinations offer comparable bonding performance to dentin substrate either before or after simulated aging that seems to have no adverse effect on the achieved bond.

Effect of 1-Piece Post and Core Fabrication Techniques on Fracture Strength

Purpose

The purpose of this in vitro study was to evaluate and compare the fracture strengths of post and core systems produced with different fabrication techniques and materials.

Methods

Forty extracted human single-root premolars were used in this study. After root canal treatment, the teeth were randomly divided into 4 groups of 10 each as follows: group C: metallic 1-piece posts and cores fabricated by casting, and serving as the control; group CM: metallic posts and cores fabricated with the copy milled technique; group LS: 1-piece posts and cores fabricated with the laser sintering technique; and group ZR: 1-piece zirconia posts and cores fabricated with computer-aided design and computer-aided manufacturing (CAD-CAM). The posts and cores were cemented to the teeth with adhesive resin cement; then, the specimens were mounted to acrylic resin blocks, attached to an Instron Universal Testing Machine, and loaded with a crosshead speed of 1 mm/min, until fracture. Data were statistically analyzed using 1-way analysis of variance (ANOVA), followed by the post hoc Tukey test (α = 0.05).

Results

The highest fracture results were found in group ZR (315.4 ± 53.4 N), which showed significant differences from all other groups (p<0.05). The lowest test values were found in group C (230.2 ± 29.8 N). Group LS (250.9 ± 29.0 N), group CM (253.0 ± 22.4 N) and group C did not show any significant differences (p>0.05).

Conclusions

Custom-made zirconia 1-piece posts and cores, fabricated using the CAD-CAM procedure, can be an alternative treatment method when compared with other techniques.

Influence of preparation design on fit and ceramic thickness of CEREC 3 partial ceramic crowns after cementation

OBJECTIVE

This study investigated the influence of preparation design on the marginal and internal gap and ceramic thickness of partial ceramic crowns (PCCs) fabricated with the CEREC 3 system.

MATERIALS AND METHODS

Sixteen extracted human mandibular molars were prepared according to two different preparation designs (n = 8): a retentive preparation design with traditional cusp capping (Group I) and a non-retentive preparation design with horizontal reduction of cusps (Group II). PCCs were fabricated from IPS Empress CAD with the CEREC 3 system. The parameters for luting space and minimum occlusal ceramic thickness were set to 30 μm and 1.5 mm, respectively. The fabricated PCCs were cemented to their corresponding teeth with self-adhesive resin cement and were then scanned by micro-computed tomography. The marginal and internal gaps were measured at pre-determined measuring points in five bucco-lingual and three mesio-distal cross-sectional images. The ceramic thicknesses of the PCCs were measured at the measuring points for cusp capping areas.

RESULTS

Group II (167.4 ± 76.4 μm) had a smaller overall mean gap, which included the marginal and internal gap measurements, than that of Group I (184.8 ± 89.0 μm). The internal gaps were larger than the marginal gaps, regardless of preparation design. Group I presented a thinner ceramic thickness in the cusp capping areas than the minimum occlusal ceramic thickness parameter of 1.5 mm. CONCLUSION. Preparation design had an influence on fit, particularly the internal gap of the PCCs. Ceramic thickness could be thinner than the minimum ceramic thickness parameter.

Examination of ceramic restoration adhesive coverage in cusp-replacement premolar using acoustic emission under fatigue testing

Background

This study investigates CAD/CAM ceramic cusp-replacing restoration resistance with and without buccal cusp replacement under static and dynamic cyclic loads, monitored using the acoustic emission (AE) technique.

Method

The cavity was designed in a typical MODP (mesial-occlusal-distal-palatal) restoration failure shape when the palatal cusp has been lost. Two ceramic restorations [without coverage (WOC) and with (WC) buccal cuspal coverage with 2.0 mm reduction in cuspal height] were prepared to perform the fracture and fatigue tests with normal (200 N) and high (600 N) occlusal forces. The load versus AE signals in the fracture and fatigue tests were recorded to evaluate the restored tooth failure resistance.

Results

The results showed that non-significant differences in load value in the fracture test and the accumulated number of AE signals under normal occlusal force (200 N) in the fatigue test were found between with and without buccal cuspal coverage restorations. The first AE activity occurring for the WOC restoration was lower than that for the WC restoration in the fracture test. The number of AE signals increased with the cyclic load number. The accumulated number of AE signals for the WOC restoration was 187, higher than that (85) for the WC restoration under 600 N in the fatigue test.

Conclusion

The AE technique and fatigue tests employed in this study were used as an assessment tool to evaluate the resistances in large CAD/CAM ceramic restorations. Non-significant differences in the tested fracture loads and accumulated number of AE signals under normal occlusal force (200 N) between different restorations indicated that aggressive treatment (with coverage preparation) in palatal cusp-replacing ceramic premolars require more attention for preserving and protecting the remaining tooth.

Evaluation of Resin Bond Strength to Yttria-stabilized Tetragonal Zirconia and Framework Marginal Fit: Comparison of Different Surface Conditionings

The purpose of this study was to evaluate the effect of different surface treatments of yttria-stabilized tetragonal zirconia (Y-TZP) on bond strength durability and marginal discrepancies. For adhesion testing, 144 specimens of VITA In-Ceram YZ ceramic for InLab were obtained (5.25×3.75×4.5 mm) and divided into six groups (n=24) according to the surface treatment: 1) Control (CRTL): untreated; 2) SIL: tribochemical silica coating (CoJet system, 3M/ESPE AG); 3) V1+HF: spray application of low-fusing porcelain glaze (V1, VITA Akzent Spray Glaze) followed by etching with hydrofluoric acid (HF) (one minute); 4) V1+SIL: V1 glazing (VITA Akzent Spray Glaze) followed by tribochemical silica coating; 5) V2+HF: brush application of low-fusing porcelain glaze (VITA Akzent Glaze) plus etching with HF (one minute); and 6) V2+SIL: V2 glazing (VITA Akzent Glaze) plus tribochemical silica coating. After all treatments, the surfaces were silanized for five minutes (ESPE-SIL) and cementation was performed using Panavia F (Kuraray). Half of the specimens in each treatment were tested 24 hours after cementation (dry), with the other half subjected to storage (150 days) and thermocycling (12,000×) (aging), and then a shear test was carried out (1 mm/min). The micromorphological (digital optical profilometry and scanning electron microscopy) and elemental analyses of the treated surfaces were performed. The inner surfaces of 60 Y-TZP infrastructures were conditioned and marginal fit was evaluated. The statistical analysis revealed that the groups treated via surface glaze application followed by hydrofluoric acid etching and silanization showed the highest bond strength (in dry and aging conditions), but the bond strengths were affected by aging. The highest marginal discrepancies were observed in the groups receiving glaze (117.4 ± 29.6 to 105.8 ± 12.2 μm) when compared to other groups (55.3 ± 8.7 and 55 ± 8.5 μm). Low-fusing porcelain glaze + hydrofluoric acid etching changed the morphology of the Y-TZP ceramic and improved the adhesion to the resin cement, but obtaining high and stable bond values to Y-TZP remains challenging. Marginal discrepancies increased with glazing.

Influence of CAD/CAM all-ceramic materials on cell viability, migration ability and adenylate kinase release of human gingival fibroblasts and oral keratinocytes

OBJECTIVES

The aim of this study was to analyze the influence of four CAD/CAM all-ceramic materials on cell viability, migration ability and adenylate kinase (ADK) release of human gingival fibroblasts (HGF) and oral keratinocytes (HOK).

MATERIALS AND METHODS

HGF and HOK were cultured on disc-shaped CAD/CAM all-ceramic materials (e.max CAD LT, e.max CAD HT, Empress CAD and Mark II) and on discs made of tissue culture polystyrene surface (TCPS) serving as control. Cell viability was analyzed by using an MTT assay, and migration ability was investigated by a scratch assay. A ToxiLight assay has been performed to analyze the effect of all-ceramic materials on ADK release and cell apoptosis.

RESULTS

At MTT assay for HGF, no significant decrease of cell viability could be detected at all points of measurement (p each > 0.05), while HOK demonstrated a significant decrease in cell viability especially on Empress CAD and Mark II at each point of measurement (p each < 0.001). Scratch assay demonstrated an increased migration ability for HGF on e.max CAD HT, Empress CAD and Mark II (p each < 0.001), whereas HOK showed a significantly decreased migration ability on all tested materials at all points of measurement (between -36 % and -71 %; p each < 0.001). At ToxiLight assay, only small cytotoxic effects of the all-ceramic materials could be investigated.

CONCLUSIONS

This study disclosed significant differences in cell viability and migration ability of HGF and HOK on CAD/CAM all-ceramic materials.

CLINICAL RELEVANCE

CAD/CAM all-ceramic materials can influence oral cell lines responsible for soft tissue creation which may affect the esthetic outcome.

Clinical Evaluation of Ceramic Inlays and Onlays Fabricated With Two Systems: Five-Year Follow-Up

This study evaluated the five-year clinical performance of ceramic inlays and onlays made with two systems: sintered Duceram (Dentsply-Degussa) and pressable IPS Empress (Ivoclar Vivadent). Eighty-six restorations were placed by a single operator in 35 patients with a median age of 33 years. The restorations were cemented with dual-cured resin cement (Variolink II, Ivoclar Vivadent) and Syntac Classic adhesive under rubber dam. The evaluations were conducted by two independent investigators at baseline, and at one, two, three, and five years using the modified United States Public Health Service (USPHS) criteria. At the five-year recall, 26 patients were evaluated (74.28%), totalling 62 (72.09%) restorations. Four IPS restorations were fractured, two restorations presented secondary caries (one from IPS and one from Duceram), and two restorations showed unacceptable defects at the restoration margin and needed replacement (one restoration from each ceramic system). A general success rate of 87% was recorded. The Fisher exact test revealed no significant difference between Duceram and IPS Empress ceramic systems for all aspects evaluated at different recall appointments (p&gt;0.05). The McNemar chi-square test showed significant differences in relation to marginal discoloration, marginal integrity, and surface texture between the baseline and five-year recall for both systems (p&lt;0.001), with an increased percentage of Bravo scores. However, few Charlie or Delta scores were attributed to these restorations. In conclusion, these two types of ceramic materials demonstrated acceptable clinical performance after five years.

Fatigue resistance and crack propensity of large MOD composite resin restorations: direct versus CAD/CAM inlays

OBJECTIVES

To assess the influence of material/technique selection (direct vs. CAD/CAM inlays) for large MOD composite adhesive restorations and its effect on the crack propensity and in vitro accelerated fatigue resistance.

METHODS

A standardized MOD slot-type tooth preparation was applied to 32 extracted maxillary molars (5mm depth and 5mm bucco-palatal width) including immediately sealed dentin for the inlay group. Fifteen teeth were restored with direct composite resin restoration (Miris2) and 17 teeth received milled inlays using Paradigm MZ100 block in the CEREC machine. All inlays were adhesively luted with a light curing composite resin (Filtek Z100). Enamel shrinkage-induced cracks were tracked with photography and transillumination. Cyclic isometric chewing (5 Hz) was simulated, starting with a load of 200 N (5000 cycles), followed by stages of 400, 600, 800, 1000, 1200 and 1400 N at a maximum of 30,000 cycles each. Samples were loaded until fracture or to a maximum of 185,000 cycles.

RESULTS

Teeth restored with the direct technique fractured at an average load of 1213 N and two of them withstood all loading cycles (survival=13%); with inlays, the survival rate was 100%. Most failures with Miris2 occurred above the CEJ and were re-restorable (67%), but generated more shrinkage-induced cracks (47% of the specimen vs. 7% for inlays).

SIGNIFICANCE

CAD/CAM MZ100 inlays increased the accelerated fatigue resistance and decreased the crack propensity of large MOD restorations when compared to direct restorations. While both restorative techniques yielded excellent fatigue results at physiological masticatory loads, CAD/CAM inlays seem more indicated for high-load patients.

Fracture Strength of Minimally Prepared Resin Bonded CEREC Inlays

Minimal preparation designs for inlay restorations are a viable option for CAD/CAM systems (CEREC) and could potentially strengthen the restored tooth.

Evaluation of the relative contributions of multi-factors in an adhesive MOD restoration using FEA and the Taguchi method

OBJECTIVES

This study determines the relative contribution of changes (design factors) in cavity dimension, restorative material, adhesive layer modulus and thickness and loading condition on the biomechanical response of a premolar adhesive Class II MOD restoration.

METHODS

A validated finite element (FE) model was used to simulate the mechanical responses. The Taguchi method was employed to identify the significance of each design factor in controlling the stress.

RESULTS

The results indicated that the loading condition was the major factor affecting the stress values (49% in tooth and 46% in cement). Cavity depth was found as the second contributor affecting the stress values (31 % in tooth and 30% in cement), followed by resin cement modulus (12% in tooth and 13% in cement). Other factors were found to have no significant effect on the tooth and cement stress values. Increased stress values were found with lateral force, deeper cavity and higher luting cement modulus.

SIGNIFICANT

The combined use of FE analysis and the Taguchi method efficiently identified the relative contributions of several restorative factors and indicated that cavity depth was the most critical factor on the cavity dimensions in attaining a proper occlusal adjustment. Reduced lateral occlusal force and lower modulus luting material application are recommended to obtain a better force-transmission mechanism.

Ceramics as biomaterials for dental restoration

Sintered ceramics and glass-ceramics are widely used as biomaterials for dental restoration, especially as dental inlays, onlays, veneers, crowns or bridges. Biomaterials were developed either to veneer metal frameworks or to produce metal-free dental restorations. Different types of glass-ceramics and ceramics are available and necessary today to fulfill customers' needs (patients, dentists and dental technicians) regarding the properties of the biomaterials and the processing of the products. All of these different types of biomaterials already cover the entire range of indications of dental restorations. Today, patients are increasingly interested in metal-free restoration. Glass-ceramics are particularly suitable for fabricating inlays, crowns and small bridges, as these materials achieve very strong, esthetic results. High-strength ceramics are preferred in situations where the material is exposed to high masticatory forces.

The clinical success of all-ceramic restorations

BACKGROUND

The authors conducted a comprehensive literature review to compile and compare clinical evidence for the treatment of teeth using all-ceramic restorations.

TYPES OF STUDIES REVIEWED

The authors searched the English-language peer-reviewed literature using MEDLINE and PubMed with a focus on research published between 1993 and 2008. They also conducted a hand search of relevant dental journals. They reviewed randomized controlled trials, nonrandomized controlled studies, longitudinal experimental clinical studies, longitudinal prospective studies and longitudinal retrospective studies.

RESULTS

Evidence suggests that for veneers, intracoronal restorations and complete-coverage restorations for single-rooted anterior teeth, clinicians may choose from any all-ceramic system on the basis of esthetic needs (many systems have had greater than 90 percent success at six years). Well-studied molar restorations include those made of alumina and, increasingly, zirconia and bonded lithium disilicate. Reasonable evidence has shown the effectiveness of anterior three-unit fixed partial dentures made of lithium disilicate, alumina and zirconia. For three-unit restorations involving a molar, expert consensus suggests that only zirconia-based systems are indicated.

CLINICAL IMPLICATIONS

Available evidence indicates the effectiveness of many all-ceramic systems for numerous clinical applications. Bonding has been shown to increase clinical success. Studies of zirconia prostheses indicate problems with porcelain cracking.

Long-term Survival of Cerec Restorations: A 10-year Study

Class I and II CAD-CAM ceramic restorations can be considered durable alternatives to direct and laboratory-fabricated restorations.

Marginal Fit of Heat-pressed vs CAD/CAM Processed All-ceramic Onlays Using a Milling Unit Prototype

The marginal fit of all-ceramic restorations has an important influence on the clinical performance and lifetime of adhesively luted restorations. In proximal boxes, an average marginal gap of less than 100 μm is claimed. These clinical requirements are fulfilled by both processing procedures.

Survival of Inlays and Partial Crowns Made of IPS Empress After a 10-year Observation Period and in Relation to Various Treatment Parameters

Ceramic inlays as aesthetic restorations in the posterior region can be used successfully in routine clinical therapy. Cement viscosity, the operator (experienced dentist vs dental student) and the number of surfaces have no influence on longevity.

Recent advances in materials for all-ceramic restorations

The past 3 years of research on materials for all-ceramic veneers, inlays, onlays, single-unit crowns, and multi-unit restorations are reviewed in this article. The primary changes in the field were the proliferation of zirconia-based frameworks and computer-aided fabrication of prostheses, and a trend toward more clinically relevant in vitro test methods. This article includes an overview of ceramic fabrication methods, suggestions for critical assessment of material property data, and a summary of clinical longevity for prostheses constructed of various materials.

Developing meaningful systematic review of CAD/CAM reconstructions and fiber-reinforced composites

OBJECTIVE

Clinical literature was examined for evidence supporting use of CAD/CAM reconstructions and fiber-reinforced materials.

MATERIALS AND METHODS

Potential evidence was identified via databases [PubMed; EMBASE (R) Drugs & Pharmacology; Center for Reviews and Dissemination, University of York; Cochrane Library], hand search of non-indexed literature, secondary reference searches, and personal contacts with clinical trial PI's. Search terms included: dental restorations; CAD/CAM; CEREC; LAVA; CERCON; Procera; inlay/onlay; dental prosthesis; fiber-reinforced composite (FRC).

RESULTS

Two randomized-controlled clinical trials were identified as examined in one Cochrane Collaboration review relevant to CAD/CAM inlays. One systematic review of 15 CAD/CAM inlay studies was examined. Six studies were identified of three commercial FRC endodontic posts and eight reported on FRC use for fixed denture prostheses. Fifteen ongoing prospective trials were identified studying CAD/CAM fabricated zirconia-based prostheses. A total of 76 papers were referenced including those related to use of in vitro measures as evidence.

CONCLUSIONS

Review of the Cochrane analysis raised concerns that typical RCT protocols may prove insufficient for stratification of confounding variables (patient, practitioner, material) when treatment outcomes are primarily prosthesis- or material-based (not patient-based, e.g., as in fracture). RCT designs are most straightforward when treatment outcomes are patient-based (e.g., soft tissue changes). When treatment responses are material-based, controls also become difficult to define and studies become tests of equivalency/superiority; where well-stratified cohort designs are likely preferred. Large numbers of independent cohort studies support the use of CAD/CAM ceramic inlay/onlay restorations and crowns but many complications inhibit the application of high-level systematic review. Except perhaps for fiber-based endodontic posts, the clinical FRC literature appears insufficient for expert review. Single in vitro measures cannot currently serve as evidence for clinical practice, except in limited cases of simple function (e.g., impression material accuracy). Batteries of in vitro measures are often applied during materials development but cannot substitute for clinical study.

An overview of treatment considerations for esthetic restorations: a review of the literature

Controversy persists regarding the treatment planning criteria for esthetic restorations. This article reviews the literature regarding the biocompatibility, marginal adaptation, color matching, patient selection, technique sensitivity, and mode and rate of failure of tooth-colored restorations. A Medline search was completed for the period from 1986 to 2006, along with a manual search, to identify pertinent English peer-reviewed articles and textbooks. The key words used were amalgam, posterior composite resin, ceramic inlays/onlays, CEREC, porcelain laminate veneers, all-ceramic crowns, and all-ceramic fixed partial dentures.

Materials for chairside CAD/CAM-produced restorations

BACKGROUND

and Overview. Although the use of computer-aided design/computer-aided manufacturing (CAD/CAM) seems to be a recent addition to the dental restorative armamentarium, this concept was first investigated more than 35 years ago. CEREC (Sirona Dental Systems GmbH, Bensheim, Germany) was the first and is the only available chairside system, and it has more than 20 years of use in the dental office. The initial concept had three tenets: esthetic ceramic reconstruction, a single patient visit and minimal tooth reduction (inlays and onlays instead of crowns). The author reviews the materials used for CAD/CAM-fabricated restorations. The structure, properties and clinical success of the materials for full-contour chairside restorations, as well as laboratory-based high-strength all-ceramic restorations are presented.

RESULTS

CAD/CAM restorations have demonstrated clinical success owing to a combination of improvements in materials with advances in CAD/CAM systems. Full-contour ceramic restorations fabricated chair-side may reinforce the tooth, providing good long-term clinical success. High-strength milled restorations allow for the use of all-ceramic restorations for multiple-unit posterior and anterior bridges.

CLINICAL IMPLICATIONS

Examination of the structure, properties and clinical results of CAD/CAM materials supports their use in routine dental practice.

Clinical performance of chairside CAD/CAM restorations

BACKGROUND

The CEREC system (Sirona Dental Systems GmbH, Bensheim, Germany) is marking its 20th year of clinical service. The author reviews the literature on the effectiveness of this chairside CAD/CAM system.

TYPES OF STUDIES REVIEWED

The author identified and reviewed clinical studies from 1985 through 2006 that included CEREC-generated inlays, onlays or crowns. These studies were conducted in both private practice and university settings. The author summarized the findings as they relate to postoperative sensitivity, restoration fracture, color match, margin adaptation and clinical longevity.

RESULTS

Although postoperative sensitivity was reported, it was due to mainly occlusal interferences. Long-term postoperative sensitivity was not a reported problem. Similar to other ceramic restorations, restoration fracture is the primary mode of failure for CEREC-generated restorations. Although margin wear is detected consistently, consequences of the wear leading to restoration failure were reported rarely. The survival probability of CEREC-generated restorations was reported to be approximately 97 percent for five years and 90 percent for 10 years.

CLINICAL IMPLICATIONS

The low rate of restoration fracture and long-term clinical survivability document the effectiveness of the CEREC system as a dependable, esthetic restorative option for patients.

Two-year clinical performance of cast gold vs ceramic partial crowns

Cast gold partial crowns (CGPC) are an accepted means of restoring posterior teeth with extended lesions. However, for esthetic reasons, CGPC are being increasingly substituted with partial ceramic crowns (PCC). The aim of the present prospective split-mouth study was to compare the clinical performance of PCC and CGPC. There were 29 patients (male 12, female 17) who participated in the investigation for a total of 58 restorations. In each patient, one CGPC (Degulor C) and one PCC (Vita MarkII/Cerec III) were placed. CGPC were inserted using conventional zinc-phosphate cement (Harvard); PCC were adhesively luted to the cavities (Variolink II/Excite). The restorations were clinically rated using modified United States Public Health Service (USPHS) criteria at baseline and 1 and 2 years after placement. The median patient age was 38 years (range 25-54). There were 29 of the CGPC and 14 PCC placed in molars, while 15 PCC were placed in premolars. All patients were available for the 1- and the 2-year recall. One PCC (1.7%) failed and had to be replaced after 2 years in situ. The rest of the restorations were functional without need of replacement. The evaluation using USPHS criteria revealed no statistically significant differences between CGPC and PCC with the exception of anatomic form: PCC showed occlusal chipping in two cases without need of replacement. From these data, it can be concluded that PCC may provide an esthetic and tissue-conservative alternative to CGPC. However, long-term studies comparing the clinical performance and longevity of cast gold and ceramic partial crowns for posterior teeth are desirable.

Evaluation of a reinforced slot design for CEREC system to restore extensively compromised premolars

OBJECTIVES

The structural stability and adhesive strength of a large-cavity premolar with a CEREC restoration is a frequent problem in long-term use. This study sought to determine whether an additional reinforced slot could increase tooth/ceramic retention using finite element (FE) analysis and fracture testing.

METHODS

The cavity was designed in a typical MODL restoration failure shape when the lingual cusp has been lost. Two FE restored-tooth models with different cavity designs were created using image processing, contour stacking, and mesh generation. Interfacial (normal and shear) stresses were then calculated with and without the slot design for restored teeth under lateral and axial forces and different interfacial conditions (bonded and de-bonding). For validation, a fracture experiment was performed with and without reinforced slot designs for large ceramic CEREC restorations.

RESULTS

The maximum stresses at the buccal wall increased when a lateral occlusal force acted on the restored tooth with a slot design. Conversely, the interfacial stresses decreased when the restored tooth received a uniform axial occlusal force. After de-bonding on the buccal tooth/ceramic interface, the stresses increased by an average factor of three over those obtained with a bonded interface. The fracture forces were consistent with the tendencies predicted in FE analyses.

CONCLUSIONS

An additional reinforced slot for the CEREC restoration of a large cavity could increase retention when a restored tooth receives an axial occlusal load. However, the benefits of a slot seem to be doubtful for a premolar often subjected to a lateral load.

The Effect of Base Materials with Different Elastic Moduli on the Fracture Loads of Machinable Ceramic Inlays

Based on the results of this study, the elastic moduli of base materials had an influence on fracture loads of machinable ceramic inlays. The use of a base material with a high elastic modulus to support a ceramic inlay is recommended.

Survival of resin-bonded porcelain veneer crowns placed with and without metal reinforcement

OBJECTIVES

The purpose of this retrospective case study of dental records was to compare the long-term failure rates and modes for resin-bonded sintered feldspathic porcelain veneer crowns (RBPVCs) either containing or without metal substructure reinforcement.

METHODS

Two prosthodontists placed 62 RBPVCs fabricated with, and 167 without, metal reinforcement in 143 older adolescent and adult patients treated in a private practice. Clinical judgement determined the type of crown design placed. Preparation margins were generally finished on enamel, and all crowns occluded with opposing teeth. Observations included the patients, operators, crown designs and failure modes. Chi-square or Fisher's exact tests and life table survival statistics were used to evaluate the findings (alpha = 0.05).

RESULTS

Over five years, failures occurred in 14.5% of RBPVCs fabricated with, and in 18.6% without, metal reinforcement. Cumulative survival estimates were 74.3 +/- 8.5(Standard Error)% and 72.9 +/- 4.8(SE)%, respectively (P = 0.96). Mandibular posterior crowns comprised 27.1% of the placements, but 47.5% of the failures. Bulk fracture of porcelain occurred in 7.0% of the crowns, all without metal reinforcement. Minor porcelain fractures and debonding were less frequent in both types of crowns. Persistent pulpitis occurred in 3.5% of all teeth.

CONCLUSIONS

There was a significant risk of failure for sintered porcelain RBPVCs placed as posterior restorations. Although metal reinforcement was able to reduce the risk of bulk fracture of porcelain, other causes of failure were less affected.

Evidence-based decision making: Guide to reading the dental materials literature

Although potential links between materials data and clinical behavior are often implied, the status of such linkage is often left obscure. This paper provides clinicians a context within which to view materials information as evidence for clinical indications and to broaden readers' appreciation for the subject. Hierarchies of both clinical and nonclinical data are presented and discussed from the point of view of their predictive potential regarding clinical performance. Excellent sources of information are identified for the clinician making treatment decisions, and perspectives are offered on the value of other published materials data.