Marco Gresnigt

Randomized controlled split-mouth clinical trial of direct laminate veneers with two micro-hybrid resin composites

OBJECTIVES This randomized, split-mouth clinical study evaluated the survival rate of direct laminate veneers made of two resin-composite materials. METHODS A total of 23 patients (mean age: 52.4 years old) received 96 direct composite laminate veneers using two micro-hybrid composites in combination with two adhesive resins (Ena-Bond-Enamel HFO: n=48, Clearfil SE Bond-Miris2: n=48). Enamel was selectively etched with 38% H(3)PO(4) for 30s, rinsed 30s and the corresponding adhesive resin was applied accordingly. Existing resin composite restorations in good conditions (small or big) were not removed but conditioned using silica coating (CoJet) and silanized (ESPE-Sil). Restorations were evaluated at baseline and thereafter every 6 months. Additional qualitative analysis was performed using modified USPHS criteria. RESULTS Mean observation period was 41.3 months. Altogether, 12 absolute failures were observed [survival rate: 87.5%] (Kaplan-Meier). The survival rates with the two resin composites did not show significant differences [Enamel HFO: 81.2%, Miris2: 93.8%] (p>0.05). The presence of existing composite restorations on the prepared teeth did not affect the survival rate significantly (intact teeth: 100%, small restorations: 90.6%, big restorations: 82.7%) (p>0.05). Surface roughness and marginal discolouration were the main qualitative deteriorations observed until the final recall. Secondary caries and endodontic complications did not occur in any of the teeth. CONCLUSION Early findings of this clinical study with the two micro-hybrid composite laminate veneers showed similar survival rate and their clinical performance was not significantly influenced when bonded onto intact teeth or onto teeth with existing restorations with the protocol applied.

Fracture strength, failure type and Weibull characteristics of lithium disilicate and multiphase resin composite endocrowns under axial and lateral forces

OBJECTIVE Multiphase resin composite materials have been advocated as an alternative to reinforced ceramics but limited information is available to date on their stability. This in vitro study evaluated the effect of axial and lateral forces on the strength of endocrowns made of Li2Si2O5 and multiphase resin composite. METHODS Sound human molars (N=60, n=10 per group) were randomly divided into 6 groups: Group C: Control, no preparation or restoration; Group LI: Endocrown made of Li2Si2O5 (IPS e.max CAD) and Group LA: Endocrown made of multiphase resin composite material (Lava Ultimate). After decapitation and endodontic preparation, immediate dentin sealing was performed. Following CAD/CAM fabrication, their cementation surfaces were silica coated (CoJet System) and silanized (ESPE-Sil). Endocrowns were then adhesively cemented (Variolink II). All specimens were thermocycled (×10,000 cycles). While half of the specimens in each group were subjected to axial (C(A), LI(A), LA(A)), the other half was subjected to lateral static (C(L), LI(L), LA(L)) loading (1mm/min). Failure type and location after debonding/fracture were classified. Data were analyzed using ANOVA and Tukeys post hoc test (α=0.05). Two-parameter Weibull distribution values including the Weibull modulus, scale (m) and shape (0), values were calculated. RESULTS Under axial loading, mean fracture strength (N) did not show significant difference between groups: LAA (2675±588)(a), LIA (2428±566)(a), CA (2151±672)(a) (p>0.05) and under lateral loading, LAL (838±169)(A) presented significantly lower mean values than those of other groups: CL (1499±418)(B), LIL (1118±173)(B) (p<0.05). Both endocrown materials and the control group were more vulnerable to lateral loading than axial loading. Under axial loading, Weibull distribution presented higher shape (0) for Groups LIA (5.35) and LAA (5.08) than that of the control (3.97) and under lateral loading LIL (7.5) showed higher shape (0) than those of other groups (4.69-6.46). After axial loading, failure types were mainly cohesive in the material and after lateral loading primarily adhesive between the material and dentin for both LI and LA, most of which were repairable. SIGNIFICANCE Under axial loading, molars restored with endocrowns performed similar with both Li2Si2O5 and multiphase resin composite but the latter was less durable under lateral loading.

Randomized Clinical Trial of Indirect Resin Composite and Ceramic Veneers: Up to 3-year Follow-up

PURPOSE This randomized controlled split-mouth clinical trial evaluated the short-term survival rate of indirect resin composite and ceramic laminate veneers. MATERIALS AND METHODS A total of 10 patients (mean age: 48.6 years) received 46 indirect resin composite (Estenia; n = 23) and ceramic laminate veneers (IPS Empress Esthetic; n = 23) on the maxillary anterior teeth. Veneer preparations with incisal overlap were performed and existing resin composite restorations of good quality were not removed but conditioned using silica coating (CoJet) and silanization (ESPE-Sil). Enamel and dentin were etched and rinsed; adhesive resin (ExciTE) was then applied. After cementation (Variolink Veneer), restorations were evaluated at baseline and thereafter every 6 months for up to 3 years using modified USPHS criteria. RESULTS Seventeen laminate veneers were bonded onto intact teeth and 29 on teeth having existing resin composite restorations. In total, 3 failures were observed in the form of debonding (n = 1) and fracture (n = 2) in the group of resin composite laminate veneers. No significant difference was observed between the survival rates of composite and ceramic laminate veneers (Estenia: 87%, IPS Empress Esthetic: 100%; p > 0.05). The overall survival rate was 93.5% (Kaplan-Meier). Of the 43 laminate veneers, minor voids and defects were observed in 6 of the composite and 3 of the ceramic veneers. Slight staining at the margins (n = 3) and slightly rough surfaces were more frequently observed for the resin composite laminate veneers (n = 18) up to the final recall. CONCLUSION Early findings of this clinical trial on two veneer materials showed statistically similar survival rates. Surface quality changes were more frequent in the composite veneer material.

Effect of static and cyclic loading on ceramic laminate veneers adhered to teeth with and without aged composite restorations.

PURPOSE Existing composite restorations on teeth are often remade prior to the cementation of fixed dental prostheses. The aim of this study was to evaluate the effect of static and cyclic loading on ceramic laminate veneers adhered to aged resin composite restorations. MATERIALS AND METHODS Eighty sound maxillary incisors were collected and randomly divided into four groups: group 1: control group, no restorations; group 2: two Class III restorations; group 3: two Class IV restorations; group 4: complete composite substrate. Standard composite restorations were made using a microhybrid resin composite (Anterior Shine). Restored teeth were subjected to thermocycling (6000 cycles). Window preparations were made on the labial surface of the teeth for ceramic laminate fabrication (Empress II). Teeth were conditioned using an etch-and-rinse system. Existing composite restorations representing the aged composites were silica coated (CoJet) and silanized (ESPE-Sil). Ceramic laminates were cemented using a bis-GMA-based cement (Variolink Veneer). The specimens were randomly divided into two groups and were subjected to either static (groups 1a, 2a, 3a, 4a) or cyclic loading (groups 1b, 2b, 3b, 4b). Failure type and location after loading were classified. Data were analyzed using one-way ANOVA and Tukeys test. RESULTS Significantly higher fracture strength was obtained in group 4 (330 ± 81 N) compared to the controls in group 1 (179 ± 120 N) (one-way ANOVA, p < 0.05). Group 1b survived a lower mean number of cyclic loads (672,820 cycles) than teeth of groups 2b to 4b (846x103 to 873x103 cycles). Failure type evaluation after the fracture test showed predominantly adhesive failures between dentin and cement, but after cyclic loading, more cohesive fractures in the ceramic were seen. CONCLUSION Ceramic laminate veneers bonded to conditioned aged composite restorations provided favorable results. Surface conditioning of existing restorations may eliminate the necessity of removing aged composite restorations.

Bonding of Glass Ceramic and Indirect Composite to Non-aged and Aged Resin Composite

PURPOSE Since adhesion of the restorative materials to pre-polymerized or aged resin composites presents a challenge to the clinicians, existing restorations are often removed and remade prior to cementation of fixed dental prostheses (FDPs). This study evaluated bond strength of non-aged and aged resin composite to an indirect resin composite and pressed glass ceramic using two resin cements. MATERIALS AND METHODS Disk-shaped specimens (diameter: 3.5, thickness: 3 mm) (N = 160) produced from a microhybrid resin composite (Quadrant Anterior Shine) were randomly divided into eight groups. While half of the specimens were kept dry at 37°C for 24 h, the other half was aged by means of thermocycling (6000 times, 5°C to 55°C). The non-aged and aged resin composites were bonded to a highly filled indirect composite (Estenia) and a pressed glass ceramic (IPS Empress II) using either a photopolymerizing (Variolink Veneer) or a dual-polymerizing (Panavia F2.0) resin cement. While cementation surfaces of both the direct and indirect composite materials were silica coated (30 µm SiO2, CoJet-Sand) and silanized (ESPE-Sil), ceramic surfaces were conditioned with hydrofluoric acid (20 s), neutralized, and silanized prior to cementation. All specimens were cemented under a load of 750 g. Shear force was applied to the adhesive interface in a universal testing machine (1 mm/min). Failure types of the specimens were identified after debonding. RESULTS Significant effects of aging (p < 0.05), restorative material (p < 0.05), and cement type (p < 0.05) were observed on the bond strength (3-way ANOVA). Interaction terms were also significant (p < 0.05) (Tukeys test). After aging, in terms of bond strength, indirect composite and pressed glass ceramic in combination with both cements showed no significant difference (p > 0.05). Both indirect composite (24.3 ± 5.1 MPa) and glass ceramic in combination with Variolink (22 ± 9 MPa) showed the highest results on non-aged composites, but were not significantly different from one another (p > 0.05). On the aged composites, indirect composite and glass ceramic showed no significant difference in bond strength within each material group (p > 0.05), with both Panavia (17.2 ± 6 and 15 ± 5.5 MPa, respectively) and Variolink (19 ± 8, 12.8 ± 5.3 MPa, respectively), but in all groups, glass ceramic-Variolink on aged composite revealed the lowest results (12.8 ± 5.3 MPa). Among all groups, predominantly cohesive failures were observed in the indirect resin composite substrate (79 out of 80) as opposed to the ceramic (18 out of 80) (p < 0.05) (Chi square). CONCLUSION Regardless of the resin cement type, considering the bond values and the failure types, the adhesion quality of indirect composite cemented to non-aged and aged resin composite was superior with both cements compared to that of pressed glass ceramic.

Effect of immediate and delayed dentin sealing on the fracture strength, failure type and Weilbull characteristics of lithiumdisilicate laminate veneers.

OBJECTIVES Adhesion on dentin is less reliable than on enamel, which could affect the durability of laminate veneers (LV). Immediate dentin sealing (IDS) is suggested instead of delayed dentin sealing (DDS) to overcome hypersensitivity and prevent debonding from dentin. This study evaluated the effect of IDS and DDS on the durability of Li2Si2O5 laminate veneers in vitro. METHODS Window preparations were made on the labial surfaces of sound maxillary central incisors (N=50). They were randomly divided into five groups: Group 1: Enamel only+H3PO4+Adhesive (control); Group 2: <1/4 dentin+H3PO4+DDS (2 weeks later); Group 3: Complete dentin+H3PO4+DDS (2 weeks later); Group 4: <1/4 dentin+H3PO4+IDS; Group 5: Complete dentin+H3PO4+IDS. Li2Si2O5 laminate veneers (e.max Press) were bonded to the labial surfaces of the teeth with adhesive resin cement (Variolink Veneer). IDS layers were silicacoated (CoJet System) and silanized (ESPE-Sil). The teeth with their bonded laminates were thermocycled (10.000× cycles) and then subjected to static loading (1mm/min). Failure type and location after debonding were classified. Data were analyzed using ANOVA and Tukeys post hoc test (α=0.05). Two-parameter Weibull distribution values including the Weibull modulus, scale (m) and shape (0), values were calculated. RESULTS Mean fracture strength (N) per group in descending order was as follows: Group 5 (576±254), Group 4 (478±216), Group 1 (473±159), Group 2 (465±186), and Group 3 (314±137). The presence of complete dentin exposure sealed with DDS after 2 weeks on the bonded surface (Group 3) resulted in significantly lower fracture strength results than those in group 5 with IDS (p=0.034). Weibull distribution presented higher shape (0) for Group 1 (3.67), than those of other groups (2.51-2.89). Failure types were predominantly adhesive failure between the cement and the laminate veneer in Groups 1, 2, 4 whereas Group 3 presented more often complete adhesive failures between the cement and dentin. In Group 5, failures showed some IDS and cement with or without ceramic fracture attached on the tooth. SIGNIFICANCE When laminate veneers are bonded to a large dentin substrate, application of immediate dentin sealing improves adhesion and thereby, the fracture strength of Li2Si2O5 laminate veneers.

Effect of luting agent on the load to failure and accelerated-fatigue resistance of lithium disilicate laminate veneers

OBJECTIVE The aim of this study was to investigate the influence of the luting agent on the application of laminate veneers (LVs) in an accelerated fatigue and load-to-failure test after thermo-cyclic aging. METHODS Sound maxillary central incisors (N=40) were randomly divided into four groups to receive LVs (Li2Si2O5) that were adhesively bonded: Group CEMF: Adhesive cement (Variolink Esthetic LC), fatigue test; Group CEMLF: Adhesive cement, load-to-failure test; Group COMF: Resin composite (Enamel HFO), fatigue test; Group COMLF: Resin composite, load-to-failure test. The specimens were thermo-mechanically aged (1.2×106 cycles at 1.7Hz/50N, 8000 cycles 5-55°C) and then subjected to either accelerated fatigue (5Hz, 25N increasing after each 500 cycles) or load to failure (1mm/min). Failure types were classified and data analyzed using chi-square, Kaplan Meier survival, Log Rank (Mantel-Cox) and independent-samples t-test. RESULTS After thermo-mechanical aging, fracture resistance (p<0.000) was higher in the composite groups. Kaplan Meier survival rates showed significant difference (p<0.001) between the composite (mean load: 1165N; mean cycles: 22.595) and the cement groups (mean load: 762.5N; mean cycles: 14.569). The same differences were observed in the load to failure test (cement M=629.4N, SD±212.82 and composite M=927.59N, SD±261.06); t (18)=-2.80, p=0.01. Failure types were observed as fractures and chipping in group CEMF, all other groups were predominantly adhesive failures between the luting agent and the laminate veneer. SIGNIFICANCE The delivery of laminate veneers using a direct restorative composite rather than a resin cement resulted in significantly less chipping and fractures, higher fracture strength in both accelerated fatigue and load-to-failure.

Cementation of Glass-Ceramic Posterior Restorations: A Systematic Review

Aim. The aim of this comprehensive review is to systematically organize the current knowledge regarding the cementation of glass-ceramic materials and restorations, with an additional focus on the benefits of Immediate Dentin Sealing (IDS). Materials and Methods. An extensive literature search concerning the cementation of single-unit glass-ceramic posterior restorations was conducted in the databases of MEDLINE (Pubmed), CENTRAL (Cochrane Central Register of Controlled Trials), and EMBASE. To be considered for inclusion, in vitro and in vivo studies should compare different cementation regimes involving a “glass-ceramic/cement/human tooth” complex. Results and Conclusions. 88 studies were included in total. The in vitro data were organized according to the following topics: (micro)shear and (micro)tensile bond strength, fracture strength, and marginal gap and integrity. For in vivo studies survival and quality of survival were considered. In vitro studies showed that adhesive systems (3-step, etch-and-rinse) result in the best (micro)shear bond strength values compared to self-adhesive and self-etch systems when luting glass-ceramic substrates to human dentin. The highest fracture strength is obtained with adhesive cements in particular. No marked clinical preference for one specific procedure could be demonstrated on the basis of the reviewed literature. The possible merits of IDS are most convincingly illustrated by the favorable microtensile bond strengths. No clinical studies regarding IDS were found.

Effect of immediate dentine sealing on the fracture strength of lithium disilicate and multiphase resin composite inlay restorations

PURPOSE Limited information is available on the effect of Immediate Dentin Sealing (IDS) on the fracture strength of indirect partial posterior restorations. This study evaluated the effect of IDS on the fracture strength and failure types of two indirect restorative materials. MATERIALS AND METHODS Standard MOD inlay preparations were made on sound molars (N=40, n=10 per group) and randomly divided into four groups to receive the inlay materials with and without the application of IDS: Group L-IDS-: Li2Si2O5 (Lithium disilicate, IPS e.max) without IDS; Group L-IDS+: Li2Si2O5 with IDS; Group MR-IDS-: Multiphase resin composite (MR, Lava Ultimate) without IDS; MR-IDS+: MR with IDS. Inlays made of L were etched with 5% hydrofluoric acid, and MR inlays were silica coated. After silanization, they were cemented using adhesive resin cement (Variolink Esthetic DC). The specimens were thermo-mechanically aged (1.2×106 cycles, 1.7Hz, 8000 cycles, 5-55°C) and then subjected to load to failure (1 mm/min). Failure types and locations of debondings were classified. Data were statistically analyzed using ANOVA, Mann Whitney U-test and Chi-square tests (α=0.05). Two-parameter Weibull distribution values including the Weibull modulus, scale (m) and shape (0), values were calculated. RESULTS After aging conditions, no apparent changes were observed in marginal integrity but occlusal wear facets were more common with MR than with L (p<0.001). Material type and the application of IDS significantly affected the results (p=0.013). While group L-IDS- showed the lowest mean fracture strength (1358±506N) among all groups (p<0.05), application of IDS significantly increased the results significantly (L-IDS+: 2035±403N) (p=0.006). MR groups with and without IDS, did not show significant difference (MR-IDS-: 1861±423, MR-IDS+: 1702±596 N) (p=0.498). When materials without IDS are compared, L showed significantly lower results than that of MR (p=0.035). With the application of IDS, no significant difference was noted between L and MR materials (p=0.160). Weibull distribution presented the highest shape (0) for L-IDS+ (5.66) compared to those of other groups (3.01-4.76). Neither the material type (p=0.830), nor the application of IDS (p=0.54) affected the severity of the failure types. In 95% of the cases, the IDS layer left adhered on the tooth surface after fracture tests. In groups where no IDS was used, resin cement remained on the tooth surface in 44% of the cases (p=0.001). No significant differences were observed between the materials with respect to cement remnants or IDS after fracture (p=0.880). The incidence of repairable failure types (83%) was more common with L than with MR (75%) material (p>0.05). CONCLUSION Immediate dentin sealing improves adhesion, and thereby the fracture strength of inlays made of lithium disilicate but not that multiphase resin composite.

Loss of Accuracy of Torque Wrenches Due to Clinical Use and Cleaning Procedure: Short Communication.

PURPOSE The aim of this study was to investigate the way intensive use and multiple cleanings of torque wrenches may interfere with accurary over time. MATERIALS AND METHODS Three different brands (one spring-style and two friction-style types) were tested at baseline and after enduring mechanical testing (1,000 cycles) and cleaning in a thermal disinfector (150 cycles). Torque wrenches were tested at a predetermined value of 30 Ncm at given intervals, and true values were registered by means of a digital torque gauge. RESULTS All measured values varied between 28.3 Ncm and 31.1 Ncm. Only the spring-style torque wrench revealed values that differed significantly from baseline after both mechanical testing (P < .001) and cleaning (P < .05). CONCLUSION The spring-style torque wrench produced values that changed significantly after multiple mechanical and multiple cleaning cycles. However, the differences were small and the measured values from all tested specimens were close to the predetermined value of 30 Ncm.