Immediate Dentin Sealing: A Fundamental Procedure for Indirect Bonded Restorations

The purpose of this article is to review evidence-based principles that could help optimize dentin bonding for indirect composite and porcelain restorations. More than 30 articles were reviewed, most of them addressing the specific situation of dentin bonding for indirect restorations. It appears that the combined results of this data plus clinical experience suggest the need for a revision in the dentin bonding procedure. Immediate application and polymerization of the dentin bonding agent to the freshly cut dentin, prior to impression taking, is recommended. This new application procedure, the so-called immediate dentin sealing (IDS), appears to achieve improved bond strength, fewer gap formations, decreased bacterial leakage, and reduced dentin sensitivity. The use of filled adhesive resins (low elastic modulus liner) facilitates the clinical and technical aspects of IDS. This rational approach to adhesion also has a positive influence on tooth structure preservation, patient comfort, and long-term survival of indirect bonded restorations.

CLINICAL SIGNIFICANCE

Tooth preparation for indirect bonded restorations (eg, composite/ceramic inlays, onlays, and veneers) can generate significant dentin exposures. It is recommended to seal these freshly cut dentin surfaces with a dentin bonding agent (DBA) immediately following tooth preparation, before taking impression. A three-step total-etch DBA with a filled adhesive resin is recommended for this specific purpose. The major advantages, as well as the technical challenges of this procedure, are presented in detail.

Benefit of active compression-decompression cardiopulmonary resuscitation as a prehospital advanced cardiac life support. A randomized multicenter study

BACKGROUND

We compared short-term prognosis of active compression-decompression (ACD) and standard (STD) cardiopulmonary resuscitation (CPR) in out-of-hospital cardiac arrests.

METHODS AND RESULTS

We randomized advanced cardiac life support (ACLS) with ACD ACLS CPR on odd days and STD ACLS CPR on even days. We measured the rates of return of spontaneous circulation (ROSC), survival at 1 hour (H1), at 24 hours (H24), and at 1 month (D30): hospital discharge (HD); neurological outcome; and complications. Mean times from collapse to basic cardiac life support CPR was 9 minutes and from collapse to ACLS CPR was 21 minutes. Compared with the STD ACLS patients (n = 258), ACD ACLS patients (n = 254) had higher survival rates (ROSC, 44.9% versus 29.8%, P = .0004; H1, 36.6% versus 24.8%, P = .003; H24, 26% versus 13.6%, P = .002; HD without neurological impairment, 5.5% versus 1.9%, P = .03) and a trend for improvement in neurological outcome at D30 (Glasgow-Pittsburgh Outcome Categories = 1.6 +/- 0.8 versus 2.3 +/- 1.1. P = .09). Sternal dislodgements (2.9% versus 0.4%, P = .03) and hemoptysis (5.4% versus 1.3%, P = .01) were more frequent in the ACD ACLS group.

CONCLUSIONS

Despite long time intervals, ACD significantly improved short-term survival rates in out-of-hospital cardiac arrests compared with STD CPR.

Efficient 3D finite element analysis of dental restorative procedures using micro-CT data

OBJECTIVES

This investigation describes a rapid method for the generation of finite element models of dental structures and restorations.

METHODS

An intact mandibular molar was digitized with a micro-CT scanner. Surface contours of enamel and dentin were fitted following tooth segmentation based on pixel density using an interactive medical image control system. Stereolithography (STL) files of enamel and dentin surfaces were then remeshed to reduce mesh density and imported in a rapid prototyping software, where Boolean operations were used to assure the interfacial mesh congruence (dentinoenamel junction) and simulate different cavity preparations (MO/MOD preparations, endodontic access) and restorations (feldspathic porcelain and composite resin inlays). The different tooth parts were then imported in a finite element software package to create 3D solid models. The potential use of the model was demonstrated using nonlinear contact analysis to simulate occlusal loading. Cuspal deformation was measured at different restorative steps and correlated with existing experimental data for model validation and optimization.

RESULTS

Five different models were validated by existing experimental data. Cuspal widening (between mesial cusps) at 100 N load ranged from 0.4 microm for the unrestored tooth, 9-12 microm for MO, MOD cavities, to 12-21 microm for endodontic access cavities. Placement of an MOD adhesive restoration in porcelain resulted in 100% cuspal stiffness recovery (0.4 microm of cuspal widening at 100 N) while the composite resin inlay allowed for a partial recuperation of cusp stabilization (1.3 microm of cuspal widening at 100 N).

SIGNIFICANCE

The described method can generate detailed and valid three dimensional finite element models of a molar tooth with different cavities and restorative materials. This method is rapid and can readily be used for other medical (and dental) applications.

Anatomic crown width/length ratios of unworn and worn maxillary teeth in white subjects

STATEMENT OF PROBLEM

Dimensions of teeth have been available for a century. Some significant and clinically relevant aspects of dental esthetics, however, such as the crown width/length ratios, have not been presented in tooth morphology sources until recently.

PURPOSE

The purpose of this study was to analyze the anatomic crowns of 4 tooth groups (central incisors, lateral incisors, canines, and first premolars) of the maxillary dentition with respect to width, length and width/length ratios and determine how these parameters are influenced by the incisal edge wear.

MATERIAL AND METHODS

Standardized digital images of 146 extracted human maxillary anterior teeth from white subjects (44 central incisors, 41 lateral incisors, 38 canines, 23 first premolars) were used to measure the widest mesiodistal portion "W" (in millimeters) and the longest inciso-cervical/occluso-cervical distance "L" (in millimeters). The width/length ratio "R" (%) was calculated for each tooth. A 1-way analysis of variance was used to compare the mean values of W, L, and R for the different groups ("unworn" and "worn" subgroups, except for premolars). Multiple least significant difference range tests (confidence level 95%) were then applied to determine which means differed statistically from others.

RESULTS

There was no influence of the incisal wear on the average value of W (width) within the same tooth group. The widest crowns were those of central incisors (9.10 to 9.24 mm) > canines (7.90 to 8.06 mm) > lateral incisors (7.07 to 7.38 mm). Premolars (7.84 mm) had similar width as canines and worn lateral incisors. The L-value was logically influenced by incisal wear (worn teeth were shorter than unworn teeth) except for lateral incisors. The longest crowns were those of unworn central incisors (11.69 mm) > unworn canines (10.83 mm) and worn central incisors (10.67 mm) > worn canines (9.90), worn and unworn lateral incisors (9.34 to 9.55 mm), and premolars (9.33 mm). Width/length ratios also showed significant differences. The highest values were found for worn central incisors (87%) and premolars (84%). The latter were also similar to worn canines (81%), which constituted a homogeneous group with worn lateral incisors (79%) and unworn central incisors (78%). The lowest ratios were found for unworn canines and unworn lateral incisors (both showing 73%).

CONCLUSIONS

Along with other specific and objective parameters related to dental esthetics, average values for W (mesiodistal crown dimension), L (inciso-cervical crown dimension), and R (width/length ratio) given in this study for white subjects may serve as guidelines for treatment planning in restorative dentistry and periodontal surgery.

Immediate dentin sealing improves bond strength of indirect restorations

STATEMENT OF PROBLEM

Delayed dentin sealing is traditionally performed with indirect restorations. With this technique, dentin is sealed after the provisional phase at the cementation appointment. It was demonstrated that this chronology does not provide optimal conditions for bonding procedures. Immediate dentin sealing (IDS) is a new approach in which dentin is sealed immediately following tooth preparation, before making the impression.

PURPOSE

The purpose of this study was to determine whether there were differences in microtensile bond strength to human dentin using IDS technique compared to delayed dentin sealing (DDS).

MATERIAL AND METHODS

Fifteen freshly extracted human molars were obtained and divided into 3 groups of 5 teeth. A 3-step etch-and-rinse dentin bonding agent (DBA) (OptiBond FL) was used for all groups. The control (C) specimens were prepared using a direct immediate bonding technique. The DDS specimens were prepared using an indirect approach with DDS. Preparation of the IDS specimens also used an indirect approach with IDS immediately following preparation. All teeth were prepared for a nontrimming microtensile bond strength test. Specimens were stored in water for 24 hours. Eleven beams (0.9 x 0.9 x 11 mm) from each tooth were selected for testing. Bond strength data (MPa) were analyzed with a Kruskal-Wallis test, and post hoc comparison was done using the Mann-Whitney U test (alpha=.05). Specimens were also evaluated for mode of fracture using scanning electron microscope (SEM) analysis.

RESULTS

The mean microtensile bond strengths of C and IDS groups were not statistically different from one another at 55.06 and 58.25 MPa, respectively. The bond strength for DDS specimens, at 11.58 MPa, was statistically different (P=.0081) from the other 2 groups. Microscopic evaluation of failure modes indicated that most failures in the DDS group were interfacial, whereas failures in the C and IDS groups were both cohesive and interfacial. SEM analysis indicated that for C and IDS specimens, failure was mixed within the adhesive and cohesively failed dentin. For DDS specimens, failure was generally at the top of the hybrid layer in the adhesive. SEM analysis of intact slabs demonstrated a well-organized hybrid layer 3 to 5 microm thick for the C and IDS groups. For DDS specimens the hybrid layer presented a marked disruption with the overlying resin.

CONCLUSIONS

When preparing teeth for indirect bonded restorations, IDS with a 3-step etch-and-rinse filled DBA, prior to impression making, results in improved microtensile bond strength compared to DDS. This technique also eliminates any concerns regarding the film thickness of the dentin sealant.

Immediate dentin sealing supports delayed restoration placement

STATEMENT OF PROBLEM

Immediate dentin sealing (IDS) is a new approach in indirect restorations. Dentin is sealed immediately following tooth preparation, prior to impression making. It is not known whether it is still possible to obtain an efficient bond between the resin-coated dentin and the restoration after 2 to 4 months of placement of provisional restorations.

PURPOSE

The purpose of this study was to determine if there were differences in microtensile bond strength to human dentin using the IDS technique when comparing 2, 7, and 12 weeks of delay until restoration placement, using 2 different dentin bonding agents (DBAs). Previously published preliminary IDS data were included for comparison.

MATERIAL AND METHODS

Fifty freshly extracted human molars were obtained and divided into 10 groups. A 3-step etch-and-rinse DBA (Optibond FL) and a 2-step self-etching DBA (SE Bond) were used. For each DBA, the control (C) specimens were prepared using a direct immediate bonding technique and composite restoration (Z100). Preparation of the other specimens used an indirect approach without dentin prebonding (delayed dentin sealing, DDS) or with immediate dentin sealing (IDS), immediately following preparation. IDS teeth had provisional restorations (Tempfil inlay) placed for 2 weeks (IDS-2W), 7 weeks (IDS-7W), or 12 weeks (IDS-12W) before restoration placement. All teeth were prepared for a nontrimming microtensile bond strength test (MTBS) 24 hours after definitive restoration with composite overlays (Z100). Ten to 11 beams (0.9 x 0.9 x 11 mm) from each tooth were selected for testing. MTBS data obtained from the 10 experimental groups were analyzed with a 2-way analysis of variance (ANOVA, dentin bonding system, and sequence of application) with each tooth (mean MTBS from the 10-11 beams) used as a single measurement. The Tukey HSD post hoc test was used to detect pairwise differences among experimental groups (alpha=.05). Fractured beams were also analyzed under stereoscopic microscope (x 30) and SEM.

RESULTS

For both adhesives, the mean microtensile bond strengths of C and all IDS groups were not significantly different and exceeded 45 MPa. DDS groups exhibited lower bond strength than all others sequences (P<.001) with SE Bond at 1.81 MPa significantly lower (P=.026) than Optibond FL at 11.58 MPa. The highest mean microtensile bond strength values were found with Optibond FL at 7 weeks (66.59 MPa) and 12 weeks (59.11 MPa). These were significantly higher than SE Bond in the same conditions with values of 51.96 MPa and 45.76 MPa (P=.001 and P=.003), respectively. Failures in DDS groups were all interfacial and purely adhesive. Both C and IDS-2W groups demonstrated interfacial failure that was typically mixed with both areas of failed adhesive resin and areas of cohesively failed dentin while IDS-7W and IDS-12W failed consistently between the existing resin coating (used during IDS) and the overlaying composite resin.

CONCLUSIONS

When preparing teeth for indirect bonded restorations, IDS with a 3-step etch-rinse or a 2-step self-etching DBA (prior to impression making) results in microtensile bond strength similar to that obtained with a freshly placed adhesive. The bond strength is not affected by up to 12 weeks of elapsed time prior to placement of the definitive restoration.

Stress distribution of inlay-anchored adhesive fixed partial dentures: a finite element analysis of the influence of restorative materials and abutment preparation design

STATEMENT OF PROBLEM

Indirect composite or ceramic fixed partial dentures (FPDs) have become an alternative to conventional metal-ceramic adhesive fixed partial dentures (AFPDs). Little information about the adequate restorative material and tooth preparation design for inlay-anchored AFPDs is available to the clinician.

PURPOSE

The purposes of this simulation study were: (1) to use 2-dimensional finite element modeling to simulate stresses at the surface and interface of 3-unit posterior AFPDs made with 6 different restorative materials, and (2) to investigate the influence of 3 different abutment preparation configurations on the stress distribution within the tooth/restoration complex.

MATERIAL AND METHODS

A mesio-distal cross-section of a 3-unit AFPD was digitized and used to create 2-dimensional models of the periodontal membrane, supporting bone, different restorative materials (gold, alumina, zirconia, glass-ceramic, composite, and fiber-reinforced composite), and different abutment preparation configurations (interproximal slots vs. 2-surface [MO, DO] vs. 3-surface [MOD]). A simulated 50-N vertical occlusal load was applied to the standardized pontic element. The principal stress within the restorative materials, stresses at the tooth/restoration interface, and surface tangential stresses at the level of the pontic were calculated in MPa from the postprocessing files and compared to each other.

RESULTS

All materials and tooth preparation design exhibited a similar stress pattern, with a definite compressive area at the occlusal side of the pontic, a tensile zone at the gingival portion of the pontic, and tensile stress peaks in the abutment/pontic connection areas. Among isotropic materials, standard non-reinforced composites exhibited better stress transfer and reduced tensile stresses at the adhesive interface than ceramics and gold. Optimized placement of the glass fibers within the composite resulted in similar stress distribution when tested in 2-surface abutment preparation configuration. There was no detectable influence of preparation design on the behavior of the pontic area. Among all 3 preparation designs, only the DO design exhibited almost pure compression at the interface.

CONCLUSION

Within the limitations of this simulation experiment, the composite materials tested demonstrated a resilient component that favored stress transfer within the tooth/restoration complex. Their clinical use, however, may be contraindicated due to insufficient strength and fracture toughness. The addition of extremely tough fibers to composites represents the most promising combination. Clinical trials are required to ensure that veneering composite can survive under clinical conditions.

Crack propensity of porcelain laminate veneers: A simulated operatory evaluation

STATEMENT OF PROBLEM

Anterior teeth are especially subject to the thermal variations of ingested food and drinks. Postoperative cracks of porcelain laminates are considered a possible consequence of polymerization shrinkage, function, and thermocycling.

PURPOSE

This investigation was conducted to define the parameters associated with the development of cracks in porcelain veneers using cyclic thermal fatigue.

MATERIAL AND METHODS

Twenty-seven maxillary incisors were restored with porcelain laminate veneers and subjected to thermocycling (5 degrees C to 50 degrees C) for 1000 cycles. Ceramic cracks were reported for 11 of the 27 specimens. Teeth were sectioned and prepared for SEM analysis. Measurements of the ceramic and the luting composite thicknesses were performed for each specimen at different restoration locations (facial, incisal, and proximal).

RESULTS

No significant differences in the ceramic or the luting composite thicknesses were observed between cracked and uncracked specimens. However, significant differences were observed in the ratio of the ceramic and luting composite thicknesses. Most cracked samples exhibited a ratio at the facial location below 3.0 (2.6 +/- 0.35), whereas most noncracked specimens were above this value (3.9 +/- 0.19). Incisal and especially proximal measurements alone were not significantly different between cracked versus uncracked specimens. Ceramic was slightly thinner in the facial aspect than in the proximal aspect, which was also thinner than the incisal aspect. Composite in the facial aspect was thinner in the cervical area than in the incisal third of the tooth.

CONCLUSIONS

Significant cyclic temperature changes can induce the development of flaws in porcelain veneers. Control of tooth reduction and the application of die spacers during laboratory procedures undoubtedly represent key elements; a sufficient and even thickness of ceramic combined with a minimal thickness of luting composite will provide the restoration with a favorable configuration with regard to crack propensity, namely, a ceramic and luting composite thickness ratio above 3.

Novel porcelain laminate preparation approach driven by a diagnostic mock-up

One critical step in the porcelain laminate technique is the achievement of sufficient ceramic thickness. At least two different strategies for tooth preparation can be found in the literature: (1) earlier simplified techniques included the use of depth cutters guided by the existing tooth surface-however, that approach did not take into consideration alterations of the tooth owing to aging, wear, or loss of enamel and thus led to greater risks for dentin exposures; (2) more recent and sophisticated methods have integrated an additive diagnostic procedure (ie, wax-up or mock-up) to compensate for tooth aging or severe existing loss of tooth substance. This approach allows for more enamel preservation and, as a consequence, more predictable bonding, biomechanics, and esthetics. The present article illustrates in detail the latest development in tooth preparation for porcelain laminates. This technique combines the time efficiency of earliest methods with the rationale and diagnostic foundations of the more recent techniques.

CLINICAL SIGNIFICANCE

Using this new laminate porcelain preparation approach, clinicians should be able to produce not only more accurate preparations, but also higher-quality tooth preparations in a time-efficient fashion.

Wear of enamel and veneering ceramics after laboratory and chairside finishing procedures

PURPOSE

This in vitro study compared the wear of enamel against 3 types of ceramics with high esthetic potential (designed for layering techniques): feldspathic porcelain (Creation), aluminous porcelain (Vitadur alpha), and low-fusing glass (Duceram-LFC). Laboratory finishing (glazing/polishing) and chairside polishing with a Dialite kit were simulated to compare their respective effects on wear.

METHODS

Tooth-material specimen pairs were placed in an artificial mouth using closed-loop servohydraulics. Constant masticatory parameters (13.5 N occlusal force, 0.62 mm lateral excursion; 0.23 second cuspal contact time) were maintained for 300, 000 cycles at a rate of 4 Hz. The occlusal surface of each pair was mapped and digitally recorded before and after each masticatory test. Quantitative changes were measured in terms of depth and volume of wear. Quantitative wear characteristics were assessed by SEM.

RESULTS

Significant differences were observed (2-factor ANOVA, P <.05). Duceram-LFC generated increased volume loss of enamel (0.197 mm(3)) compared with Creation (0.135 mm(3)) and Vitadur alpha (0.153 mm(3)). Creation exhibited the lowest ceramic wear and lowest combined volume loss (0.260 mm(3); the sum of the data for enamel and the opposing material) compared with Duceram-LFC (0.363 mm(3)) and Vitadur alpha (0.333 mm(3)). The most significant differences among materials were observed in volume loss, not in depth of wear. For all 3 ceramic systems, qualitative SEM evaluation revealed an abrasive type of wear. Wear characteristics of chairside polished specimens were similar to those of laboratory finished specimens (glazed and polished).

CONCLUSION

Duceram-LFC was the most abrasive ceramic for the antagonistic tooth. Creation ceramic was the least abrasive material and most resistant to wear. Defects, brittleness, and the possibly insufficient toughness of LFC may explain its increased abrasiveness. Laboratory and chairside finishing procedures generated similar results.

Ferrule-Effect Dominates Over Use of a Fiber Post When Restoring Endodontically Treated Incisors: An In Vitro Study

OBJECTIVES

 The aim of this study was to investigate the restoration of broken-down endodontically treated incisors with the ferrule effect using glass ceramic crowns bonded to composite resin core buildups with or without a fiber post. A no-ferrule group with post was also included for comparison.

METHODS AND MATERIALS

 Thirty decoronated endodontically treated bovine incisors with a 2-mm ferrule were restored with a direct buildup using a nanohybrid direct composite resin (Miris 2 and Optibond FL) with or without a glass-fiber-reinforced post. An additional group of 15 teeth without a ferrule were restored with buildup and a fiber post. All teeth were prepared to receive bonded glass ceramic crowns (e.max CAD luted with Variolink Esthetic DC) and were subjected to accelerated fatigue testing. Cyclic isometric loading was applied to the incisal edge at an angle of 30° and a frequency of 5 Hz, beginning with a load of 100 N (×5000 cycles). A 100 N load increase was applied each 15,000 cycles. Specimens were loaded until failure or to a maximum of 1000 N (×140,000 cycles). Groups were compared using the Kaplan Meier survival analysis (log rank test at p=0.05).

RESULTS

 None of the tested specimens withstood all 140,000 load cycles. Specimens with posts but without a ferrule were affected by an initial failure phenomenon (wide gap at the lingual margin between the buildup/crown assembly and the root). There was a significant difference in mean survived cycles between the ferrule groups (Fp=73,332× and FNp=73,244×) and the no-ferrule group (50,121×; p=0.001). The addition of a fiber post was not significant in the presence of the ferrule (p=0.884). In both groups with posts, 100% of failures were unrestorable. The no-post group had 47% of restorable and possibly restorable failures.

CONCLUSIONS

 The survival of broken-down nonvital incisors was improved by the presence of the ferrule but not by the fiber-reinforced post. Fiber posts were always detrimental to the failure mode and were not able to compensate for the absence of a ferrule.

Effect of luting composite shrinkage and thermal loads on the stress distribution in porcelain laminate veneers

STATEMENT OF PROBLEM

Cyclic thermal fatigue has demonstrated a significant influence of the thicknesses of luting composite and ceramic in crack propensity of porcelain laminates.

PURPOSE

This study was conducted to define potentially involved parameters for crack development in porcelain laminates bonded to teeth. Finite element modeling was used to evaluate the respective effects of luting composite shrinkage and significant thermal changes.

MATERIAL AND METHODS

A buccolingual cross-section of a maxillary incisor was digitized and used as a template to generate a single 2-dimensional mesh, including all the different restorative designs. Luting composite shrinkage was simulated at a baseline temperature of 20 degrees C. The effect of thermal loads from 20 degrees C to 5 degrees C and from 20 degrees C to 50 degrees C was assessed with and without preexisting composite shrinkage.

RESULTS

Shrinkage of the luting composite alone generated important compressive forces on the ceramic, either at the restoration surface or interface. Compression intensity was related to geometry and ratio of thicknesses between the ceramic and luting composite (CER/CPR). Lower ratios produced higher compression forces in the ceramic. When thermal loads were combined to the composite shrinking forces, the stress pattern was significantly changed only for the experimental conditions with the lowest CER/CPR ratio. Temperature increase reduced compressive stresses and exacerbated tensile stresses. Thermal loads were simulated alone (situation of an "ideal nonshrinking" luting composite) and generated mainly tensile stresses in the ceramic, which intensity was again modulated by the CER/CPR ratio and the local geometry of composite and ceramic. Because of ceramic brittleness, these tensile forces were more detrimental than the high compression created by composite shrinkage alone. The stress pattern was not influenced by the incisal length of the veneer but rather by the facial thickness of ceramic. The worst record made with a shrinking luting agent (500 microm of luting composite, lowest CER/CPR ratio, 5 degrees C) was much less harmful than the worst record made with a hypothetical "nonshrinking" luting material.

CONCLUSIONS

The ratio of the thickness of cement and luting composite appears to have a relevant influence on the stress distribution in porcelain laminates. Restorations that are too thin, combined with poor internal fit, resulted in higher stresses at both the surface and interface of the restoration. Because of its precompressed state given by composite shrinkage, ceramics performed better with regard to temperature-induced tensile forces.

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.

Influence of No-Ferrule and No-Post Buildup Design on the Fatigue Resistance of Endodontically Treated Molars Restored With Resin Nanoceramic CAD/CAM Crowns

Objectives

To evaluate the influence of adhesive core buildup designs—4-mm buildup, 2-mm buildup, and no buildup (endocrown)—on the fatigue resistance and failure mode of endodontically treated molar teeth restored with resin nanoceramic (RNC) CAD/CAM complete crowns placed with self-adhesive resin cement.

Methods and Materials

Forty-five extracted molars were decoronated at the level of the cementoenamel junction, and the roots were endodontically treated. Specimens received different Filtek Z100 adhesive core buildups (4-mm buildup, 2-mm buildup, and no buildup, endocrown preparation) and were restored with Cerec 3 CAD/CAM RNC crowns (Lava Ultimate). Restorations (n=15) and prepared teeth were treated with airborne-particle abrasion, followed by cementation with RelyX Unicem 2 Automix. Specimens were then subjected to cyclic isometric loading at 10 Hz, beginning with a load of 200 N (for 5000 cycles), followed by stages of 400, 600, 800, 1000, 1200, and 1400 N at a maximum of 30,000 cycles each. Specimens were loaded until failure or to a maximum of 185,000 cycles (10-mm-diameter composite resin sphere antagonist). The failure mode was assessed: “catastrophic” (tooth/root fracture that would require tooth extraction), “possibly reparable” (cohesive/adhesive failure with fragment and minor damage, chip or crack, of underlying tooth structure), or “reparable” fracture (cohesive or cohesive/adhesive fracture of restoration only). Groups were compared using the life table survival analysis. Intact specimens were loaded to failure and compared with one-way analysis of variance.

Results

All specimens survived the fatigue test until the 800 N-step. The survival rates for 4-mm, 2-mm, and no buildup (endocrown) were 53%, 87%, and 87%, respectively, and were not statistically different even though crowns with 2-mm buildups only started to fail at 1200 N. Minor cohesive chips were detected in many samples despite having survived all 185,000 cycles. Postfatigue load-to-failure ranged from 2969 N with 4-mm buildup (eight specimens), 2794 N for 2-mm buildup (13 specimens), and 2606 N for endocrowns (13 specimens) and were also not statistically different. There were only two catastrophic failures during the fatigue test and small subgingival delamination fractures and cracks (only with 4-mm buildup). All specimens in the load-to-failure test exhibited nonrestorable catastrophic fractures.

Conclusions

There was no influence of the buildup design on the performance of endodontically treated molars restored with RNC CAD/CAM complete crowns placed with self-adhesive cement. All restoration designs survived the normal range of masticatory forces. Failure mode tended to be more favorable with the 2-mm buildup or no buildup (endocrown).

Survival of extensively damaged endodontically treated incisors restored with different types of posts-and-core foundation restoration material

STATEMENT OF PROBLEM

Which post-and-core combination will best improve the performance of extensively damaged endodontically treated incisors without a ferrule is still unclear.

PURPOSE

The purpose of this in vitro study was to investigate the restoration of extensively damaged endodontically treated incisors without a ferrule using glass-ceramic crowns bonded to various composite resin foundation restorations and 2 types of posts.

MATERIAL AND METHODS

Sixty decoronated endodontically treated bovine incisors without a ferrule were divided into 4 groups and restored with various post-and-core foundation restorations. NfPfB=no-ferrule (Nf) with glass-fiber post (Pf) and bulk-fill resin foundation restoration (B); NfPfP=no-ferrule (Nf) with glass-fiber post (Pf) and dual-polymerized composite resin core foundation restoration (P); NfPt=no-ferrule (Nf) with titanium post (Pt) and resin core foundation restoration; and NfPtB=no-ferrule (Nf) with titanium post (Pt) and bulk-fill resin core foundation restoration (B). Two additional groups from previously published data from the same authors (FPf=2mm of ferrule (F) and glass-fiber post (Pf) and composite resin core foundation restoration; and NfPf=no-ferrule (Nf) with glass-fiber post (Pf) and composite resin core foundation restoration), which were tested concomitantly and using the same experimental arrangement, were included for comparison. All teeth were prepared to receive bonded glass-ceramic crowns luted with dual-polymerized resin cement and were subjected to accelerated fatigue testing under submerged conditions at room temperature. Cyclic isometric loading was applied to the incisal edge at an angle of 30 degrees with a frequency of 5 Hz, beginning with a load of 100 N (5000 cycles). A 100-N load increase was applied every 15000 cycles. The specimens were loaded until failure or to a maximum of 1000 N (140000 cycles). The 6 groups (4 groups from the present study and 2 groups from the previously published study) were compared using the Kaplan-Meier survival analysis (log-rank post hoc test at α=.05 for pairwise comparisons).

RESULTS

None of the tested specimen withstood all 140 000 cycles. All specimens without a ferrule were affected by an initial failure phenomenon (wide gap at the lingual margin between the core foundation restoration/crown assembly and the root). NfPfP, NfPt, and NfPtB had similar survival (29649 to 30987 mean cycles until initial failure). NfPfB outperformed NfPt and NfPtB. None of the post-and-core foundation restoration materials were able to match the performance of the ferrule group FPf (72667 cycles). In all groups, 100% of failures were catastrophic.

CONCLUSIONS

The survival of extensively damaged endodontically treated incisors without a ferrule was slightly improved by the use of a fiber post with a bulk-fill composite resin core foundation restoration. However, none of the post-and-core techniques was able to compensate for the absence of a ferrule. The presence of the posts always adversely affected the failure mode.

Composite Resin Core Buildups With and Without Post for the Restoration of Endodontically Treated Molars Without Ferrule

OBJECTIVE

The aim of this study was to investigate the restoration of highly damaged, broken-down endodontically treated molars without the ferrule effect using glass ceramic crowns on different dual-cure composite resin core buildups.

METHODS AND MATERIALS

Thirty (N=30, n=15) decoronated, endodontically treated teeth (no ferrule) were restored without a ferrule with a direct buildup using the dual-curing composite Multicore HB (group MHB) or the dual-curing composite core buildup Multicore Flow in combination with glass-fiber-reinforced composite post (FRC post; group MFP). All teeth were prepared to receive bonded glass ceramic crowns (Empress CAD luted with Variolink II) and were subjected to accelerated fatigue testing. Cyclic isometric loading was applied to the palatal cusp at an angle of 30 degrees and a frequency of 5 Hz, beginning 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. Specimens were loaded until failure or to a maximum of 185,000 cycles. Groups were compared using the life table survival analysis (log rank test at p=0.05). Average fracture loads and number of survived cycles were compared with one-way analysis of variance (Scheffé post hoc at p=0.05). Previously published data from the same authors about core buildups made of high-performance polymers (group HPP, n=15) and light-curing composite resin without FRC posts (group TEC, n=15) and with FRC posts (group TECP, n=15) using the same experimental setup were included for comparison.

RESULTS

None of the tested specimen withstood all 185,000 load cycles. There was no significant difference in mean fracture load (p=0.376), survived cycles (p=0.422), and survival (p=0.613) between MHB (facture load 859.4 N±194.92) and MFP (796.13 N±156.34). Group HPP from a previous study appeared to have significantly higher performance than all other groups except MHB. All groups with posts were affected by an initial failure phenomenon (wide gap at the margin between the buildup/crown assembly and the root).

CONCLUSIONS

HPP and MHB enhanced the performance of all-ceramic leucite-reinforced glass ceramic crowns, and insertion of a fiber-reinforced composite post was not influential when using other materials.

Ultrathin CAD-CAM glass ceramic and composite resin occlusal veneers for the treatment of severe dental erosion: An up to 3-year randomized clinical trial

STATEMENT OF PROBLEM

Ultrathin bonded posterior occlusal veneers represent a conservative alternative to traditional onlays and complete coverage crowns for the treatment of erosive dental wear. Data regarding the clinical performance of ceramic and composite resin ultrathin occlusal veneers are lacking.

PURPOSE

The purpose of this prospective randomized clinical trial was to evaluate the influence of computer-aided design and computer-aided manufacturing (CAD-CAM) restorative material (ceramic versus composite resin) on the clinical performance of ultrathin occlusal veneers bonded to worn posterior teeth.

MATERIAL AND METHODS

Eleven participants (mean age, 30.4 years) had their posterior teeth restored with 24 ceramic (e.max CAD) and 36 composite resin (Lava Ultimate) ultrathin occlusal veneers. The material type was assigned randomly. The tooth preparations were trial restoration driven and included immediate dentin sealing (OptiBond FL). The intaglio surfaces of the ceramic restorations were etched with hydrofluoric acid and silanated, and the composite resins were airborne-particle abraded and silanated. The tooth preparations were airborne-particle abraded and etched with phosphoric acid before restoration insertion. All restorations were adhesively luted with preheated composite resin (Filtek Z100). The participants were evaluated according to the modified United States Public Health Service (USPHS) criteria at baseline and then each year for up to 3 years. Survival rates were estimated with time to failure (primary outcome of interest) as the endpoint (scores 4 or 5).

RESULTS

No restorations were lost. Five partial failures, in the form of chipping (all scored 4), were observed in the composite resin group (Lava Ultimate). The Kaplan-Meier survival rates were 100% for ceramic and 84.7% (SE 0.065%) for composite resin. Differences between the 2 groups were not statistically significant (P=.124). In the surviving restorations, significant difference (P=.003) was found for surface roughness as restorations in the composite resin group experienced some surface degradation.

CONCLUSIONS

The findings of this medium-term clinical trial suggest that ceramic (e.max CAD) and composite resin (Lava Ultimate) CAD-CAM ultrathin occlusal veneers presented statistically comparable performance regardless of the minor partial failures (restorable chipping) observed in the composite resin group. Higher surface degradation was observed in the composite resin group.

Influence of post-etching cleaning and connecting porcelain on the microtensile bond strength of composite resin to feldspathic porcelain

STATEMENT OF PROBLEM

There are different methods to fabricate layered feldspathic porcelain restorations, including the refractory die technique and the hot-press technique. Standard adhesive protocol for such restorations requires etching and silanating the fitting surface of the porcelain. Variations in bond strength between porcelain and composite resin might result from the different fabrication methods for porcelain restorations.

PURPOSE

The purpose of this study was to determine differences in microtensile bond strength between composite resin (used as a luting agent) and feldspathic porcelain generated from the refractory die technique using 2 different connecting porcelains and the hot-press technique. The effect of post-etching cleaning was also investigated.

MATERIAL AND METHODS

Sixteen pairs of ceramic blocks (7 x 8 x 4 mm) were fabricated. Eight pairs were fabricated using feldspathic porcelain (D-B4) on refractory dies. For 4 pairs, the refractory dies were coated with a paste (Ducera Lay Connector Paste; group CON) as a connecting porcelain, and the other 4 pairs were coated with a clear translucent porcelain (CL-O; group CLO). Another 8 block pairs were fabricated using the hot-press technique (Authentic porcelain SL B00+; groups AUTH and AUTH-N). Surface conditioning of the ceramic blocks included airborne-particle abrasion followed by hydrofluoric acid etching (all groups), and post-etching cleaning with a brush/H3PO4 and ultrasonic bath immersion (cleaning not applied to group AUTH-N). All specimens were then silanated/heat dried, and blocks of the same porcelain were bonded to each other using an adhesive resin (Optibond FL) and a light-polymerizing composite resin (Z100). Specimens were stored in water for 24 hours. A nontrimming microtensile bond strength test was applied. Ten beams (0.9 x 0.9 x 8 mm) from each pair of blocks were selected for testing. Bond strength data (MPa) were analyzed with a Kruskal-Wallis test, and post hoc comparison was done using the Mann-Whitney U test (alpha = .05). Additional specimens (1 block per group) were also evaluated for the effect of conditioning steps and mode of fracture using optical microscopy and scanning electron microscopy (SEM) analysis.

RESULTS

The mean microtensile bond strengths of CLO and AUTH groups were not significantly different from one another at 46.3 and 49.7 MPa, respectively. For both CON and AUTH-N groups, the mean bond strengths at 37.9 MPa and 24.1 MPa, respectively, were significantly different (P < .05) from the other 3 groups. Optical microscopy revealed a significant amount of white residue for all groups as a result of hydrofluoric etching. Cleaning with a microbrush and 37.5% phosphoric acid for 1 minute resulted in the removal of the crystalline debris. The SEM analysis of specimens cleaned by phosphoric acid brushing alone revealed microscopic deposits still contaminating the etched surface; those were efficiently removed after ultrasonic cleaning. The SEM analysis of fractured beams demonstrated a trend for more mixed-type failure in CON and AUTH-N specimens involving both the composite resin and the surface of the porcelain, whereas CLO and AUTH fractured surfaces were primarily confined to the composite resin.

CONCLUSIONS

Increased resin bond strength to refractory-generated porcelain is obtained with CLO as the connecting porcelain compared to the CON paste. The AUTH porcelain exhibited the highest mean bond strength, but omission of post-etching cleaning resulted in the lowest bond strength.