Symmetry of horizontal and sagittal condylar path angles: an in vivo study.

The specific aims of the study were to determine (1) the mean condylar path inclination (CP) and Bennett angles (BA) in occlusally healthy dentate subjects and (2) whether there was right-left asymmetry of CP and BA. Eccentric movements of three mm and five mm from reference positions were recorded for 45 subjects using a Cadiax system. The mean right CP angles: 48.8 +/- 8 degrees (three mm) and 48.2 +/- 7 degrees (five mm); the mean left CP angles: 48.8 +/- 8 degrees (three mm) and 49.5 +/- 70 (5mm) were steeper than suggested means for setting articulators. The mean right BA: 7.7 +/- 3 degrees (3mm) and 7.9 +/- 4 degrees (five mm); and the mean left BA: 8.1 +/- 4 degrees (three mm) and 8.5 +/- 4 degrees (five mm) were lower than suggested means for setting articulators. Paired-t-tests showed no significant differences between right-left CP and right-left BA. These results suggest that current recommended average settings for semi-adjustable articulators for dentate individuals need to be reassessed.

In vitro comparative bond strength of contemporary self-adhesive resin cements to zirconium oxide ceramic with and without air-particle abrasion.

This study compared shear bond strengths of six self-adhesive resin cements to zirconium oxide ceramic with and without air-particle abrasion. One hundred twenty zirconia samples were air-abraded (group SB; n = 60) or left untreated (group NO). Composite cylinders were bonded to the zirconia samples with either BisCem (BC), Maxcem (MC), G-Cem (GC), RelyX Unicem Clicker (RUC), RelyX Unicem Applicator (RUA), or Clearfil SA Cement (CSA). Shear bond strength was tested after thermocycling, and data were analyzed with analysis of variance and Holm-Sidak pairwise comparisons. Without abrasion, RUA (8.0 MPa), GC (7.9 MPa), and CSA (7.6 MPa) revealed significantly higher bond strengths than the other cements. Air-particle abrasion increased bond strengths for all test cements (p < 0.001). GC (22.4 MPa) and CSA (18.4 MPa) revealed the highest bond strengths in group SB. Bond strengths of self-adhesive resin cements to zirconia were increased by air-particle abrasion. Cements containing adhesive monomers (MDP/4-META) were superior to other compositions.

Resin-bonded fixed partial dentures with a new modified zirconia surface: a clinical report.

This report describes the clinical application of a new modified zirconia surface. Resin-bonded fixed partial dentures were fabricated for nonprepared abutments, cemented, and evaluated for retention and esthetics. Initial evaluation of this new modified zirconia surface reveals acceptable mechanical and esthetic properties.

Influence of contamination and cleaning on bond strength to modified zirconia.

OBJECTIVE: To evaluate the influence of contamination and cleaning procedures on shear bond strength (SBS) to modified zirconia surfaces. METHODS: One hundred zirconium-oxide ceramic disks fabricated with a rough modified surface (Nobel Bond), which allows more micromechanical interlocking for adhesive cementation, were divided into five groups. Groups were contaminated with organic (OC; human blood and saliva) and/or inorganic contaminants (IC; type IV dental stone). For cleaning, modified surfaces were etched with phosphoric acid for 1min (PA) or fired in a ceramic furnace up to 910 degrees C and cleaned in an ultrasonic bath in ethanol (FU). Following combinations of contamination and cleaning protocols were chosen: group 1: OC-PA; group 2: IC-FU; group 3: OC+IC-PA+FU; group 4: OC+IC-no cleaning; group 5: no contamination-no cleaning. Level of contamination and efficacy of cleaning were evaluated using X-ray photoelectron spectroscopy (XPS). Composite cylinders were bonded to the disks using dual curing adhesive resin cement (RelyX ARC). Fifty samples were subjected to 20,000 thermal cycles (TC). All samples were tested for SBS. Statistical analysis was performed using one-way ANOVA with alpha=0.05. RESULTS: SBS ranged from 16.6 to 18.8MPa (non-TC) and 10.6-21.7MPa (TC). TC did not lower SBS, except for group 1. XPS showed that OC produced higher levels of carbon, nitrogen, and silica, whereas IC generated elevated levels of calcium, sulfur, carbon, and potassium. Cleaning with both procedures reduced contamination significantly. SIGNIFICANCE: A combination of FU and PA is an efficient method for cleaning contaminated modified zirconia surfaces.

In vitro shear bond strength of dual-curing resin cements to two different high-strength ceramic materials with different surface texture.

OBJECTIVE: The purpose of this study was to evaluate the shear bond strength (SBS) of two dual-curing resin cements to two high-strength ceramics with different surface texture. MATERIAL AND METHODS: Composite cylinders were bonded to aluminum oxide (A) and zirconium oxide (Z) ceramic disks with six different surfaces. Investigated surfaces were for both ceramics: dry-pressed Procera Crown (A1, Z1), machined Procera Bridge (A2, Z2), airborne particle abraded Procera bridge (A3, Z3). Additional surfaces were, for alumina, dry-pressed Procera Laminate (A4) and, for zirconia, two modified surfaces (Z4, Z5). Two adhesive resin cements were used (Clearfil Esthetic and RelyX ARC). SBS was tested in a universal testing machine before and after artificial aging by thermal cycling. RESULTS: Mean SBS ranged from 6.1 to 38.4 MPa before and from 0.0 to 41.4 MPa after aging. Clearfil Esthetic in A3, A4, and Z3 performed better than RelyX ARC. Aging decreased SBS, except for Z1, Z4, and Z5. For alumina, A4 was higher in SBS than A2, but similar to A1 and A3. For zirconia, Z5 showed the highest SBS. Z4 was higher than Z2 and Z3, but similar to Z1. CONCLUSIONS: Shear bond strength to alumina and zirconia increases with surface roughness. The modified zirconia surface Z5 provides stable long-term shear bond strength and can be bonded to either of the two used cements.

Selected mechanical and physical properties and clinical application of a new low-shrinkage composite restoration.

Polymerization shrinkage is a major concern for bonded direct posterior restorations. Recently, a new low-shrinkage composite resin restorative material was developed. However, few data are available regarding clinical manipulation of this composite. Silorane-based composites represent an alternative to conventional methacrylate-based composites for direct posterior restorations. This article critically discusses the latest peer-reviewed reports related to polymerization, bonding, polishing, and color stability of silorane composite, focusing on its clinical application. Initial evaluation of this new category of composite material shows acceptable mechanical and physical properties.

The effect of immediate dentin sealing on the marginal adaptation and bond strengths of total-etch and self-etch adhesives.

STATEMENT OF PROBLEM: Sealing ability and bond strengths of total-etch and self-etch dentin adhesives used for immediate dentin sealing have not been assessed and established. PURPOSE: The purpose of this study was to determine the effectiveness of immediate dentin sealing (IDS) using total-etch or self-etch dentin adhesives on microleakage and microtensile bond strength. MATERIAL AND METHODS: Twenty recently extracted molars were selected, and standard MOD inlay preparations were made with the gingival margins located below the cemento-enamel junction. The teeth were assigned to 4 experimental groups (n=5) according to the indirect composite restoration cementation technique used: (1) immediate dentin sealing with Adper Single Bond (TEBI); (2) conventional adhesive cementation technique using Adper Single Bond (TEAI); (3) immediate dentin sealing using Adper Prompt L-Pop (SEBI); or (4) conventional adhesive cementation technique using Adper Prompt L-Pop (SEAI). The restored teeth were thermal cycled 1,000 times between 5 degrees and 55 degrees C and then immersed in 50% ammoniacal silver nitrate. Three specimens per restoration were evaluated for microleakage, according to predefined scores, and submitted to Friedman's test (alpha=.05). The specimens were then sectioned to obtain 0.8 +/-0.2-mm-thick sticks (with n ranging from 32 to 57 specimens) and submitted to microtensile bond strength (muTBS) testing. The obtained data were submitted to 2-way ANOVA test (alpha=.05). RESULTS: None of the experimental groups demonstrated complete elimination of marginal microleakage. There were significant differences in microleakage of the tested adhesives (P>.001). IDS microleakage scores were similar to those obtained using the conventional cementation technique (CCT) for both adhesives. The highest mean bond strengths were obtained with TEBI (51.1 MPa), whereas SEAI showed the lowest mean bond strengths (1.7 MPa). IDS resulted in significantly higher bond strengths than CCT (P<.001). CONCLUSIONS: Total-etch and self-etch adhesives have a significant effect on IDS. IDS resulted in high bond strengths for both adhesives; however, the microleakage was similar to that obtained with CCT. (J Prosthet Dent 2009;102:1-9).

Shade-matching abilities of dental laboratory technicians using a commercial light source.

PURPOSE: The purpose of this study was to evaluate dental laboratory technicians' abilities to match shades using a light-corrective device under conventional laboratory conditions. The variables measured were years experience, gender, and light source. MATERIALS AND METHODS: A 14-item shade-matching quiz (SMQ) was field-tested and deemed adequate. Information included age, gender, number of years experience, and Ishihara's Colour-Blindness Assessment. Forty-two dental technicians from five northeast Ohio laboratories were invited to participate. The SMQ was administered twice: under the lighting conditions in the individual laboratories (SMQ-Lab) and with a light-corrective source (SMQ-LC). For each item, the technicians were to select the matching Vita shade tab from five preselected shade tabs. SMQ scores equaled the number of correct matches. Statistical analysis included calculation of means, standard deviations, correlation coefficients, and independent and paired t-tests. Significance was set at p

Nanoleakage, ultramorphological characteristics, and microtensile bond strengths of a new low-shrinkage composite to dentin after artificial aging.

OBJECTIVES: To study the microtensile bond strengths and nanoleakage of low-shrinkage composite to dentin. The null hypotheses tested were (1) aging does not affect the bonding of low-shrinkage composite; (2) there is no difference in microtensile bond strengths and nanoleakage using different bonding strategies. METHODS: 32 extracted molars were assigned to one of four groups: LS System Adhesive (LS, 3M ESPE); dentin etched for 15s with phosphoric acid+LS System Adhesive (LSpa); Adper Single Bond Plus (SB, 3M ESPE); SB+LS Bond (SBLS). Occlusal dentin was exposed and restored with Filtek LS (3M ESPE). The samples were tested after 24h or after 20,000 thermocycles and 6 months of aging. Teeth were sectioned with a cross-section of 0.8+/-0.2mm(2) and fractured at a crosshead speed of 1mm/min. The data were submitted to ANOVA/Duncan's post hoc test, at p<0.05. Five slabs from each group were selected and immersed in 50wt% ammoniacal silver nitrate. Then, specimens were processed for SEM, the silver penetration was measured and data analyzed with Kruskal-Wallis at p<0.05. RESULTS: No statistically significant difference was found among the experimental groups for the factor dentin treatment (p=0.165) and aging (p=0.091). All experimental groups exhibit some degree of nanoleakage. There was no adhesion of Filtek LS applied directly over dentin surfaces treated with SB. SIGNIFICANCE: The new low-shrinkage resin composite showed compatibility only with its dedicated adhesive. Pre-etching did not improve the bond strengths to low-shrinkage resin composite. Some degree of nanoleakage was evident in all groups.

An in vitro evaluation of the long-term resin bond to a new densely sintered high-purity zirconium-oxide ceramic surface.

STATEMENT OF PROBLEM: Successful long-term bonding to zirconia ceramic remains a challenge, requiring special cements and surface roughening by airborne-particle abrasion, which might negatively affect the ceramic. PURPOSE: The purpose of this study was to evaluate the shear bond strength (SBS) of composite resin cylinders to a modified zirconia surface using different luting techniques after thermal cycling. MATERIAL AND METHODS: Composite resin (TPH3) cylinders with a diameter of 3 mm were bonded to zirconia ceramics (Procera Zirconia) with a modified surface (RZ) and a machined surface (MZ). Three different adhesive luting cements (Panavia F2.0, RelyX ARC, RelyX Unicem) in combination with and without airborne-particle abrasion (50-microm and 110-microm Al(2)O(3)) were used. RZ was bonded using all 3 cements with (50 mum) and without airborne-particle abrasion; with 110 microm, only Panavia F2.0 was used. MZ was bonded using only Panavia F2.0 with (50 microm, 110 microm) and without airborne-particle abrasion. SBS was tested in a universal testing machine (Instron) before and after 90 days of water storage and 20,000 thermal cycles (dwell time, 15 seconds). Statistical analysis was performed using a multifactorial ANOVA model with alpha=.05. RESULTS: Mean SBS ranged from 10.1 to 20.0 MPa after 3 days and from 0.16 to 14.8 MPa after thermal cycling. Thermal cycling decreased SBS significantly. Airborne-particle abrasion significantly decreased SBS to the modified surface, regardless of cements used. SBS to the modified zirconia surface was significantly higher than to the machined surface. CONCLUSIONS: SBS to the modified zirconia surface is higher than to airborne-particle-abraded, machined zirconia. Airborne-particle abrasion of the modified zirconia surface is not recommended.

A retrospective case series of implants used to restore partially edentulous patients with implant-supported removable partial dentures: 31-month mean follow-up results.

OBJECTIVE: The incorporation of dental implants into removable partial dentures is a common clinical practice, but it is poorly documented in the dental literature. The purpose of this retrospective case series study was to evaluate the survival of endosseous dental implants used in restoring partially edentulous patients with implant-supported removable partial dentures (ISRPDs) of different configurations, based on up to 10 years of follow-up. METHOD AND MATERIALS: The sample consisted of 23 consecutively treated partially edentulous patients, who, between 1996 and 2005, had a total of 44 implants placed in different arch sites and who were treated with ISRPDs. The mean age was 44.2 +/- 7.5 years at inclusion. Mean follow-up time from implant placement was 31.5 months (range, 9 to 120 months). Smoking status, arch configuration before and after implant placement, follow-up time from implant placement, implant location, implant dimensions, implant and abutment survival, and overall satisfaction (assessed by questionnaire) with the restoration are presented. RESULTS: The overall implant survival rate was 95.5%; 2 implants failed. Kennedy Class I in the maxilla (6 patients) followed by Kennedy Class II in the mandible (4 patients) were the most prevalent arch configurations before implant placement. Arch configuration was modified by implant placement in 6 patients (26.1%). During follow-up, 1 abutment tooth was lost 2 years after prosthesis delivery. All patients were satisfied with their prosthesis. CONCLUSIONS: Implant-supported removable partial dentures could serve as a long-term predictable treatment modality. Careful patient selection, with an appropriate maintenance and recall system, is recommended to obtain satisfactory results.

Microtensile bond strengths and scanning electron microscopic evaluation of self-adhesive and self-etch resin cements to intact and etched enamel.

STATEMENT OF PROBLEM: The longevity of indirect adhesively cemented restorations is directly related to the bond quality of resin cements to dental tissues. Bonding to cervical enamel can generate significantly lower bond strengths than bonding to other enamel areas. The effect of enamel pretreatment on bond strengths of self-etch and self-adhesive resin cements to cervical enamel remains undetermined. PURPOSE: The purpose of this study was to evaluate cervical enamel bond strengths of self-adhesive, self-etch resin cements according to acid pretreatment, using a total-etch resin cement as the control. MATERIAL AND METHODS: The proximal surfaces of 20 extracted molars were sectioned to obtain 40 enamel rectangles with an area of 8.0 x 4.0 mm. The rectangular enamel specimens were assigned to 1 of 5 enamel experimental groups: intact enamel + RelyX Unicem (UN), etched enamel + UN (UNpa), intact enamel + Multilink (ML), etched enamel + ML (MLpa), and the total-etch-based RelyX ARC (RX; control group). Standard 8.0 x 4.0 x 6.0-mm composite resin blocks (Z250) were cemented to all specimens. The bonded enamel surfaces were sectioned into sticks with a cross-section of 0.8 +/-0.2 mm(2) and tested to failure in tension mode at a crosshead speed of 1 mm/min. The data were submitted to 1-way analysis of variance (ANOVA), followed by Tukey's HSD post hoc test (alpha=.05). Additionally, the enamel etching pattern was investigated for all experimental groups using field-emission electron microscopy. RESULTS: Statistical analysis showed significant differences among different resin cements (P<.001) and phosphoric acid etching (P<.002). The highest mean (SD) bond strengths were obtained with UNpa (32.92 (4.23)) > RX (19.40 (9.47)). Acid etching of enamel before application of self-etch resin cement did not improve the mean bond strengths (SD) for self-etch resin cement [ML (5.38 (5.97)); MLpa (5.23 (1.1))]. Self-adhesive and self-etch resin cements yielded the lowest significant mean bond strengths (SD) when applied on intact enamel: UN (13.03 (2.82)) > ML (5.38 (5.97)). Scanning electron microscopy showed a consistent etching pattern for phosphoric acid-etched specimens. Self-etch and self-adhesive resin cements applied directly to intact enamel showed inconsistent areas of etching. CONCLUSIONS: Etching cervical enamel surfaces resulted in significantly higher bond strengths for self-adhesive resin cement. For self-etch resin cement, etching did not improve bond strength.

Influence of cementation technique on fracture strength and leakage of alumina all-ceramic crowns after cyclic loading.

OBJECTIVE: To compare in vitro the influence of 3 cementation techniques on leakage and fracture strength of alumina all-ceramic crowns after cyclic loading in an artificial chewing simulator. METHOD AND MATERIALS: Forty-eight extracted molars were mounted in a way that simulates natural tooth mobility. Crowns (Procera Alumina, Nobel Biocare) were fabricated and inserted with either conventional cementation with zinc phosphate cement without pretreatment (group ZOP); cementation with a universal adhesive resin cement without pretreatment (group HYB); or adhesive bonding with composite resin after pretreatment of the tooth (dentin bonding agent) and the crown (airborne-particle abrasion and a special ceramic priming agent containing adhesive monomers that bond to metal-oxide ceramics) (group ADH). All specimens were stored in artificial saliva and subjected to 1.2 million load cycles in a dual-axis chewing simulator (Willytec). Eight specimens per group were subjected to compressive load until failure, while the remaining 8 specimens were stained and sectioned for measuring of dye penetration. One-way ANOVA and Tukey HSD were used for statistical analyses (alpha = .05). RESULTS: Cementation techniques were significantly different (P = .009) in regard to mean load at failure. Fracture strength was significantly greater for ADH (mean load at fracture, 2,782 +/- 419 N) as compared to HYB (1,980 +/- 270 N) or ZOP (1,788 +/- 242 N). All groups differed significantly for leakage values (P < .001), with ADH showing the lowest mean leakage (0.04 +/- 0.07 mm), followed by HYB (0.96 +/- 0.16 mm) and ZOP (2.44 +/- 0.19 mm). CONCLUSION: Cementation technique affects fracture strength and leakage of all-ceramic molar crowns. Fracture strengths were well above natural chewing forces for all cementation methods. However, adhesive bonding significantly increased fracture strength and improved marginal seal of alumina crowns.

Biomechanical considerations for the restoration of endodontically treated teeth: a systematic review of the literature, Part II (Evaluation of fatigue behavior, interfaces, and in vivo studies).

OBJECTIVE: The restoration of endodontically treated teeth has long been guided by empirical rather than biomechanical concepts. Part I of this literature review presented up-to-date knowledge about changes in tissue structure and properties following endodontic therapy, as well as the behavior of restored teeth in monotonic mechanical tests or finite element analysis. The aim of the second part is to review current knowledge about the various interfaces of restored, nonvital teeth and their behavior in fatigue and clinical studies. REVIEW METHOD: The basic search process included a systematic review of articles contained in the PubMed/Medline database, dating between 1990 and 2005, using single or combined key words to obtain the most comprehensive list of references; a perusal of the references of the references completed the review. RELEVANT INFORMATION AND CONCLUSIONS: Nonvital teeth restored with composite resin or composite resin combined with fiber posts resisted fatigue tests and currently represent the best treatment option. In comparison to rigid metal and/or ceramic posts, when composite resin or composite resin/fiber posts fail, the occurrence of interfacial defects or severe tooth breakdown is less likely. Adhesion into the root, however, remains a challenge because of the unfavorable ovoid canal configuration, as well as critical dentin microstructure in the deepest parts of the canal. Thus, specific combinations of adhesives and cements are recommended. The clinical performance of post-and-core restorations proved satisfactory overall, in particular with a contemporary restorative approach using composite resin and fiber posts. However, the clinical literature does not clearly isolate or identify exact parameters critical to success. This, in turn, emphasizes the importance and relevance of in vitro studies to further improve the quality and long-term stability of prosthetic foundations.

Biomechanical considerations for the restoration of endodontically treated teeth: a systematic review of the literature--Part 1. Composition and micro- and macrostructure alterations.

The specific biomechanical alterations related to vitality loss or endodontic procedures are confusing issues for the practitioner and have been controversially approached from a clinical standpoint. The aim of part 1 of this literature review is to present an overview of the current knowledge about composition changes, structural alterations, and status following endodontic therapy and restorative procedures. The basic search process included a systematic review of the PubMed/Medline database between 1990 and 2005, using single or combined key words to obtain the most comprehensive list of references; a perusal of the references of the relevant sources completed the review. Only negligible alterations in tissue moisture and composition attributable to vitality loss or endodontic therapy were reported. Loss of vitality followed by proper endodontic therapy proved to affect tooth biomechanical behavior only to a limited extent. Conversely, tooth strength is reduced in proportion to coronal tissue loss, due to either caries lesion or restorative procedures. Therefore, the best current approach for restoring endodontically treated teeth seems to (1) minimize tissue sacrifice, especially in the cervical area so that a ferrule effect can be created, (2) use adhesive procedures at both radicular and coronal levels to strengthen remaining tooth structure and optimize restoration stability and retention, and (3) use post and core materials with physical properties close to those of natural dentin, because of the limitations of current adhesive procedures.