Aluminum zirconate nanoparticles in etch and rinse adhesive to caries affected dentine: An in-vitro scanning electron microscopy, elemental distribution, antibacterial, degree of conversion and micro-tensile bond strength assessment.

To incorporate different concentrations of Al2O9Zr3 (1%, 5%, and 10%) nanoparticles (NP) into the ER adhesive and subsequently assess the impact of this addition on the degree of conversion, µTBS, and antimicrobial efficacy. The current research involved a wide-ranging examination that merged various investigative techniques, including the application of scanning electron microscopy (SEM) for surface characterization of NP coupled with energy-dispersive x-ray spectroscopy (EDX), Fourier-transform infrared (FTIR) spectroscopy, µTBS testing, and microbial analysis. Teeth were divided into four groups based on the application of modified and unmodified three-step ER adhesive primer. Group 1 (0% Al2O9Zr3 NPs) Control, Group 2 (1% Al2O9Zr3 NPs), Group 3 (5% Al2O9Zr3 NPs), and Group 4 (10% Al2O9Zr3 NPs). EDX analysis of Al2O9Zr3 NPs was performed showing elemental distribution in synthesized NPs. Zirconium (Zr), Aluminum (Al), and Oxides (O2). After primer application, an assessment of the survival rate of Streptococcus mutans was completed. The FTIR spectra were analyzed to observe the characteristic peaks indicating the conversion of double bonds, both before and after the curing process, for the adhesive Etch and rinse containing 1,5,10 wt% Al2O9Zr3 NPs. µTBS and failure mode assessment were performed using a Universal Testing Machine (UTM) and stereomicroscope respectively. The µTBS and S.mutans survival rates comparison among different groups was performed using one-way ANOVA and Tukey post hoc (p = .05). Group 4 (10 wt% Al2O9Zr3 NPs + ER adhesive) specimens exhibited the minimum survival of S.mutans (0.11 ± 0.02 CFU/mL). Nonetheless, Group 1 (0 wt% Al2O9Zr3 NPs + ER adhesive) displayed the maximum surviving S.mutans (0.52 ± 0.08 CFU/mL). Moreover, Group 2 (1 wt% Al2O9Zr3 NPs + ER adhesive) (21.22 ± 0.73 MPa) samples displayed highest µTBS. However, the bond strength was weakest in Group 1 (0 wt% Al2O9Zr3 NPs + ER adhesive) (14.13 ± 0.32 MPa) study samples. The etch-and-rinse adhesive exhibited enhanced antibacterial activity and micro-tensile bond strength (µTBS) when 1% Al2O9Zr3 NPs was incorporated, as opposed to the control group. Nevertheless, the incorporation of Al2O9Zr3 NPs led to a decrease in DC. RESEARCH HIGHLIGHTS: 10 wt% Al2O9Zr3 NPs + ER adhesive specimens exhibited the minimum survival of S.mutans. 1 wt% Al2O9Zr3 NPs + ER adhesive samples displayed the most strong composite/CAD bond. The highest DC was observed in Group 1: 0 wt% Al2O9Zr3 NPs + ER adhesive.

Adhesive Performance Assessment of Universal Adhesives and Universal Adhesive/Composite Cement Combinations.

PURPOSE: To investigate the bonding performance of three universal adhesives (UAs) to dentin and the effect of different curing modes and hydrofluoric-acid (HF) etching of lithium-disilicate glass-ceramic on the adhesive performance of two UA/composite cement (CC) combinations. MATERIALS AND METHODS: In the first project part, the immediate and aged (25k and 50k thermocycles) microtensile bond strength (µTBS) of the two light-curing UAs G2-Bond Universal (G2B; GC) and Scotchbond Universal Plus (SBUp; 3M Oral Care), and the self-curing UA Tokuyama Universal Bond II (TUBII; Tokuyama) to flat dentin was measured, when applied in both E&R and SE bonding mode using a split-tooth design (n = 10). The resultant adhesive-dentin interfaces were characterized using TEM. In the second project part, CAD/CAM composite blocks were luted to flat dentin with either Scotchbond Universal Plus/RelyX Universal (SBUp/RxU; 3M Oral Care) or Tokuyama Universal Bond II/Estecem II Plus (TUBII/ECIIp; Tokuyama Dental) using different curing modes (AA mode: auto-curing of both adhesive and cement; AL mode: auto-curing of adhesive and light-curing of cement), upon which their immediate and aged (25k and 50k thermocycles) µTBS was measured. In the third project part, the same UA/CC combinations were luted to CAD/CAM glass-ceramic to measure their immediate and aged (6-month water storage) shear bond strength (SBS). RESULTS: In E&R bonding mode, the performance of G2B, SBUp and TUBII was not significantly different in terms of µTBS, while G2B and SBUp significantly outperformed TUBII in SE bonding mode. No significant difference in µTBS was found between the SBUp/RxU and TUBII/ECIIp UA/CC combinations, regardless of bonding mode, aging time, or curing mode. The cement-curing mode did not significantly influence µTBS, while a significantly higher µTBS was recorded for the UA/CC combinations applied in E&R bonding mode. HF significantly improved the SBS of the UA/CC combinations to glass-ceramic. CONCLUSION: The self-curing adhesive performed better when applied in E&R than in SE bonding mode. The curing mode did not influence the adhesive performance of the composite cements, while an E&R bonding mode rendered more favorable adhesion in a self-curing luting protocol. When bonding to glass-ceramic, the adhesive performance of the universal adhesive/composite cement combinations benefited from HF etching.

In vitro assessment of the effect of luting agents, abutment height, and fatigue on the retention of zirconia crowns luted to titanium base implant abutments.

STATEMENT OF PROBLEM: The bonding of implant-supported prostheses is determined by abutment material, convergence angle, height, surface treatment, and luting agents. However, studies evaluating the bonding of luting agents to titanium base abutments with different heights under fatigue conditions are scarce. PURPOSE: The purpose of this in vitro study was to evaluate the retention of zirconia crowns bonded with different luting agents to titanium base abutments of different heights before and after fatigue testing. MATERIAL AND METHODS: Zirconia crowns were designed, milled, and distributed into 4 experimental groups according to the luting agents (G-Multi Primer/G-Cem LinkForce [MP/GC] and Scotchbond Universal/RelyX Ultimate [SU/RU]) and titanium base abutment heights (2.5 mm and 4 mm) (n=10). Pull-out testing was performed in a universal testing machine at a crosshead speed of 1 mm/min until crown displacement. Fatigue testing was performed by an electric precision fatigue simulator (1×106 cycles; 100 N; and 15 Hz), followed by pull-out testing of fatigued specimens. Collected data were statistically evaluated by using a linear mixed model after post hoc comparisons by the least significant difference test (α=.05). RESULTS: Luting agents, abutment heights, and fatigue influenced the bonding retention of zirconia crowns to titanium base abutments. SU/RU agents promoted higher pull-out compared with MP/GC for both abutment heights before and after fatigue. Higher abutment height increased pull-out regarding lower abutment height for SU/RU materials before and after fatigue testing. Although fatigue had no significant effect on the pull-out of MP/GC, lower bond retention was observed for SU/RU after fatigue, regardless of abutment height. CONCLUSIONS: Luting agent composition and the interaction with abutment height and fatigue influenced the retention of zirconia crowns to titanium base abutments.

Physicochemical and microbiological assessment of a dental adhesive doped with cashew nut shell liquid.

To evaluate i) the inhibitory and bactericidal activity of cashew nut shell liquid (CNSL) and its isolated compounds (anacardic acid and cardol) against oral bacteria; ii) the biofilm formation inhibition, resin-dentin bond strength and physicochemical properties of a dental adhesive incorporated with these substances. The antibacterial effect of CNSL, anacardic acid, and cardol were assessed by determining the minimum inhibitory (MIC) and minimum bactericidal (MBC) concentrations. Effect in inhibiting biofilm formation of the adhesive incorporated with the substances (15 µg/ml) against a mixed-species biofilm of Streptococcus mutans and Candida Albicans and was determined by direct contact test. Additional Analysis included microtensile bond strength (µTBS) test, elastic modulus (EM), flexural strength (FS), degree of conversion (DC), water sorption (WS) and solubility (SL). The data were submitted to statistical analysis by one-way ANOVA and Tukey's test (p < 0.05). CNSL, anacardic acid and cardol showed antibacterial activity for all strains tested, with MIC and MBC values ranging from 3.12 to 25 µg/ml. There was no growth of colonies forming units in the adhesives incorporated with the substances. EM increased in the adhesive incorporated with anacardic acid, decreased after incorporation of cardol and it was not affected by incorporation of CNSL. The substances tested showed no effect in FS, DC, WS, SL and µTBS. In conclusion, the CNSL, anacardic acid and cardol showed antibacterial effects against oral bacteria and, the incorporation of substances did not reduce the performance of the adhesive.

Comparative assessment of bonding time and 1-year bracket survival using flash-free and conventional adhesives for orthodontic bracket bonding: A split-mouth randomized controlled clinical trial.

INTRODUCTION: A new flash-free adhesive promises to eliminate the flash removal step in bonding and to reduce bonding time by as much as 40% per bracket, with a bond failure rate of less than 2%. The aim of this trial was to compare bonding time and bracket failure rate over a 1-year period between the flash-free adhesive and a conventional adhesive for orthodontic bracket bonding. METHODS: Forty-five consecutive patients had their maxillary incisors, canines, and premolars bonded with ceramic brackets (Clarity Advanced; 3M Unitek, Monrovia, Calif) using a flash-free adhesive (APC Flash-Free Adhesive Appliance System; 3M Unitek) on 1 side and a conventional adhesive (APCII Adhesive Appliance System; 3M Unitek) on the other side. The side allocation was randomized. Bonding was timed to the nearest second. Bond failure was recorded at standardized intervals of 4 weeks. The primary outcome was bonding time (average per tooth for each patient and per quadrant). Secondary outcomes were bracket failure rate within 1 year, time to first-time failure of a bracket, and bond failure type (adhesive remnant index score). Bonding times and adhesive remnant index scores upon bond failure were compared using paired t tests, with P <0.05 considered statistically significant. The adhesives were considered equivalent if the confidence interval for the difference between bracket failure rates fell within a margin of equivalence of ±5%. RESULTS: The bonding times were significantly shorter with the flash-free adhesive than with the conventional adhesive, both per tooth (P <0.001) and per quadrant (P <0.001). Compared with the conventional adhesive, the average bonding times per tooth and per quadrant with the flash-free adhesive were 37.3% and 32.9% shorter, respectively. The bracket failure rates at 1 year were 3.7% for the flash-free adhesive and 0.9% for the conventional adhesive. This was statistically equivalent. The average times to first-time failure of a bracket were 25 weeks for the flash-free adhesive and 11 weeks for the conventional adhesive. Although there were no significant differences in the adhesive remnant index scores upon failure (P >0.05), the flash-free adhesive tended to fail more often at the enamel-adhesive interface than did the conventional adhesive. CONCLUSIONS: The use of the flash-free adhesive may result in bonding time savings of approximately one third compared with the conventional adhesive. With regard to bracket survival, a statistically significant difference was not found between the 2 adhesives when ceramic brackets were bonded. REGISTRATION: This trial was registered on December 3, 2013 (ClinicalTrials.gov ID, NCT02030002). PROTOCOL: The protocol was not published before trial commencement.

Assessment of a Cavity to Optimize Ultrasonic Efficiency to Remove Intraradicular Posts.

INTRODUCTION: The study assessed an in vitro protocol for the removal of cast metal posts using ultrasonic vibration in multirooted teeth by drilling a cavity in the coronal portion of the post followed by ultrasound application in the cavity. METHOD: Forty endodontically treated molars received intraradicular cast posts and were divided into 4 groups according to the removal protocol: the control group, no cavity and no ultrasonic vibration; the ultrasonic group, no cavity and ultrasonic vibration in the coronal portion of the core; the cavity group, a cavity in the core and no ultrasonic vibration; and the cavity ultrasonic group, a cavity in the core and ultrasonic vibration inside the cavity. The traction test was performed on all samples using a universal testing machine (EMIC DL-2000; EMIC Equipamentos e Sistemas de Ensaio LTDA, São José dos Pinhais, PR, Brazil) at a speed of 1 mm/min, obtaining values in Newtons. The data were statistically analyzed using analysis of variance and the Tukey-Kramer test (P < .05). RESULTS: The results showed statistically significant differences between the tested groups (control group = 322.74 N, ultrasonic group = 283.09 N, cavity group = 244.00 N, and cavity ultrasonic group = 237.69 N). The lowest mean strength was found in the group that received ultrasonic vibration inside the cavity. CONCLUSIONS: Preparing a cavity in the coronal core followed by ultrasonic vibration reduces the traction force required for removal. The removal protocol was effective for removing posts in multirooted teeth cemented with zinc phosphate.

Thiolated alginate-based multiple layer mucoadhesive films of metformin forintra-pocket local delivery: in vitro characterization and clinical assessment.

INTRODUCTION: Periodontal disease broadly defines group of conditions in which the supportive structure of the tooth (periodontium) is destroyed. Recent studies suggested that the anti-diabetic drug metformin hydrochloride (MF) has an osteogenic effect and is beneficial for the management of periodontitis. OBJECTIVE: Development of strong mucoadhesive multiple layer film loading small dose of MF for intra-pocket application. METHODOLOGY: Multiple layer film was developed by double casting followed by compression method. Either 6% carboxy methyl cellulose sodium (CMC) or sodium alginate (ALG) constituted the inner drug (0.6%) loaded layer. Thiolated sodium alginate (TSA; 2 or 4%) constituted the outer drug free layers to enhance mucoadhesion and achieve controlled drug release. Optimized formulation was assessed clinically on 20 subjects. RESULTS: Films were uniform, thin and hard enough for easy insertion into periodontal pockets. Based on water uptake and in vitro drug release, CMC based film with 4% TSA as an outer layer was the optimized formulation with enhanced mucoadhesion and controlled drug release (83.73% over 12 h). SEM showed the effective fabrication of the triple layer film in which connective lines between the layers could be observed. FTIR examination suggests possibility of hydrogen bonding between the -NH groups of metformin and -OH groups of CMC. DSC revealed the presence of MF mainly in the amorphous form. Clinical results indicated improvement of all clinical parameters six months post treatment. CONCLUSION: The results suggested that local application of the mucoadhesive multiple layer films loaded with metformin hydrochloride was able to manage moderate chronic periodontitis.

Resistance of Hydraulic Calcium Silicate Cements to Dislodgment in Short- and Long-term Assessment.

PURPOSE: To investigate the resistance to dislodgment produced by Biodentine (Septodont) and White-MTA (Angelus) after immersion in phosphate-buffered saline (PBS) for different durations. MATERIALS AND METHODS: Dentin disks 1 ± 0.1 mm thick were obtained from the middle third of the roots of 6 human maxillary canines. On the coronal surface of each dentin disk, four 0.8-mm-diameter holes were drilled. Then the slices were halved using a low-speed saw diamond disk, and the two holes in each half were filled with one of the two tested materials. Each filled half was immersed in PBS solution (pH 7.2) either for 7 days (short term) or 60 days (long term) at 37°C. The push-out test was performed after both time periods. A general linear model (GLM) for repeated measures ANOVA was used to verify the effect of the material and duration of contact with PBS on the push-out strength. The material was considered as the within-subject contrast and the contact duration as the between-subjects effect (p < 0.05). RESULTS: Repeated measures GLM indicated a significant impact of material and time on the push-out strength of the samples (p = 0.000 and p = 0.033, respectively). Biodentine significantly improved the push-out strength compared to MTA at both times (p = 0.000). The lack of significance in the interaction between material and time indicates that PBS immersion positively influenced the push-out values of both tested materials. CONCLUSION: Long-term PBS immersion positively influenced the resistance to dislodgement from dentin of all cements tested. The Biodentine cement provided greater resistance to push-out force than did the MTA.

BPA qualtitative and quantitative assessment associated with orthodontic bonding in vivo.

OBJECTIVE: To assess the in vivo amount of BPA released from a visible light-cured orthodontic adhesive, immediately after bracket bonding. METHODS: 20 orthodontic patients were recruited after obtaining informed consent. All patients received 24 orthodontic brackets in both dental arches. In Group A (11 patients), 25 ml of tap water were used for mouth rinsing, whereas in Group B (9 patients) a simulated mouth rinse formulation was used: a mixture of 20 ml de-ionized water plus 5 ml absolute ethanol. Rinsing solutions were collected before, immediately after placing the orthodontic appliances and after washing out the oral cavity and were then stored in glass tubes. Rinsing was performed in a single phase for 60s with the entire volume of each liquid. The BPA analysis was performed by gas chromatography-mass spectrometry. RESULTS: An increase in BPA concentration immediately after the 1st post-bonding rinse was observed, for both rinsing media, which was reduced after the 2nd post-bonding rinse. Water exhibited higher levels of BPA concentration than water/ethanol after 1st and 2nd post-bonding rinses. Two-way mixed Repeated Measures ANOVA showed that the primary null hypothesis declaring mean BPA concentration to be equal across rinsing medium and rinsing status was rejected (p-value <0.001). The main effects of the rinsing medium and status, as well as their interaction were found to be statistically significant (p-values 0.048, <0.001 and 0.011 respectively). SIGNIFICANCE: A significant pattern of increase of BPA concentration, followed by a decrease that reached the initial values was observed. The amount of BPA was relatively low and far below the reference limits of tolerable daily intake.

'The last post?': assessment of the failing post-retained crown.

Failure of a post-retained restoration can provide a challenge to the general dental practitioner (GDP) in terms of diagnosis, treatment planning and communication with the patient. The cause of failure must be identified, and a thorough assessment of the restoration, remaining tooth and its functional and aesthetic demands carried out in order to plan treatment to provide the most reliable result. Clinical Relevance: This article discusses the assessment of failing post-retained crowns, with discussion of reasons for failure, thereby assisting the GDP in decision-making and treatment planning for such teeth.

An in-vitro assessment of the shear bond strength of bulk-fill resin composites to permanent and deciduous teeth.

OBJECTIVES: This study aimed to evaluate the shear bond strength (SBS) of bulk-fill resin composites (RCs) to deciduous and permanent teeth. METHODS: The following parameters were investigated: (1) tooth type (deciduous and permanent), (2) tooth substrate (enamel and dentine), (3) restorative material (a high- and a low-viscosity bulk-fill RC and a regular nanohybrid RC as control), and (4) adhesive (two self-etching adhesives). The combination of those parameters resulted in a total of 24 different groups (n=20). Permanent caries-free human molars (240) and deciduous teeth (240) were selected. The bulk-fill RCs (Tetric Evo Ceram Bulk Fill and SureFil SDR) were applied in one 4-mm increment, whereas the regular RC (Tetric Evo Ceram) was layered in two consecutive 2-mm increments. The SBS was examined after storing the specimens for 24 h at 37 °C in distilled water, followed by thermal ageing (5000 cycles between 5 °C and 55 °C). RESULTS: Data were statistically analyzed using one- and multiway analyses of variance and an independent-samples t-test (α=0.05). The multivariate analysis (general linear model with partial eta-squared statistics) tested the influence of the parameters tooth type, tooth substrate, restorative material, and adhesive on the SBS. The parameter tooth type showed no significant impact on the SBS (p=0.576). The influence of the other parameters was significant (p<0.05) but low, and the highest influence was exerted by the parameter adhesive (η(P)(2)=0.120, p=0.0001) followed by tooth substrate (η(P)(2)=0.092, p=0.0001) and restorative material (η(P)(2)=0.028, p=0.0001). The fracture pattern was predominantly adhesive (61.9%) or mixed (38.1), and no cohesive or prefailure was registered. CONCLUSIONS: Bulk-fill materials performed comparable or better than the nanohybrid RC used as control, but the adhesive used was the most relevant factor of influence. This material type might be clinically an option for a faster restoration in both permanent and deciduous teeth. CLINICAL SIGNIFICANCE: Bulk-fill materials performed comparable or slightly better than the nanohybrid RC used as control. Clinically, flowable bulk-fill RCs might be an advantage in restoring deep, narrow cavities, with difficult access angles, whereas larger cavities might be restored easily and faster using high-viscosity compounds.

Nondestructive assessment of current one-step self-etch dental adhesives using optical coherence tomography.

ABSTRACT. This study aimed to nondestructively evaluate sealing performance of eight one-step self-etch adhesives (1-SEAs) using optical coherence tomography (OCT). The two-step self-etch adhesive (2-SEA) served as the control. Round tapered class-I cavities (D=4 mm, H=2 mm) were prepared in bovine incisors, treated with each adhesive (n=5), and restored with a flowable resin composite. Cross-sections were obtained from each restoration using swept-source OCT with 1310-nm laser. The average percentage of the sealed interface (SI%) for each adhesive was calculated using image analysis software, considering increased signal intensity at the interface as gap. Samples were then sectioned and observed under confocal laser scanning microscope (CLSM). Significantly different SI% values were found among different adhesives (analysis of variance, Bonferroni, p<0.05). There was also a significant correlation in SI% between OCT and CLSM (p<0.0001, r=0.96). Additionally, microscopic analysis revealed that the gaps in 1-SEAs occurred not only at dentine-adhesive interfaces but also frequently at adhesive-composite interfaces. Some recent 1-SEAs could achieve reliable short-term sealing comparable to 2-SEA. OCT is a unique tool to nondestructively evaluate the sealing performance of the restoratives through the cavity, provided that cavity walls have a certain minimum inclination with respect to the beam.

Ultrashort echo time (UTE) MRI for the assessment of caries lesions.

OBJECTIVE: Direct in vivo MRI of dental hard tissues by applying ultrashort echo time (UTE) MRI techniques has recently been reported. The objective of the presented study is to clinically evaluate the applicability of UTE MRI for the identification of caries lesions. METHODS: 40 randomly selected patients (mean age 41 ± 15 years) were enrolled in this study. 39 patients underwent a conventional clinical assessment, dental bitewing X-ray and a dental MRI investigation comprising a conventional turbo-spin echo (TSE) and a dedicated UTE scan. One patient had to be excluded owing to claustrophobia. In four patients, the clinical treatment of the lesions was documented by intraoral pictures, and the resulting volume of the cavity after excavation was documented by dental imprints and compared with the MRI findings. RESULTS: In total, 161 lesions were identified. 157 (97%) were visible in the UTE images, 27 (17%) in the conventional TSE images and 137 (85%) in the X-ray images. In total, 14 teeth could not be analysed by MR owing to artefacts caused by dental fillings. All lesions appear significantly larger in the UTE images as compared with the X-ray and TSE images. In situ measurements confirm the accuracy of the lesion dimensions as observed in the UTE images. CONCLUSION: The presented data provide evidence that UTE MR imaging can be applied for the identification of caries lesions. Although the current data suggest an even higher sensitivity of UTE MRI, some limitations must be expected from dental fillings.

Bonded functional esthetic prototype: an alternative pre-treatment mock-up technique and cost-effective medium-term esthetic solution.

As the economy has receded in recent years, many patients have been inclined to reject dental treatment beyond what they feel is the minimal amount necessary. Increasingly, there has been reluctance to take on the expense of full-mouth restorations and time-consuming procedures. Consequently, clinicians can benefit from innovative, conservative, interim solutions that enable them to provide segment treatment with long-term stability and esthetics, with lower initial cost. The bonded functional esthetic prototype (BFEP) allows fabrication of up to 14 teeth from composite in 1 hour, providing either a pre-treatment restoration or a long-term provisional solution until further treatment can be completed. As demonstrated herein, the BFEP enables superb function, stability, and esthetics in the interim while dispersing the cost of definitive treatment over time.

An in vitro assessment of circumferential grooves on the retention of cement-retained implant-supported crowns.

STATEMENT OF PROBLEM: Crowns cemented on short implant abutments may have insufficient retention. PURPOSE: The purpose of this study was to evaluate the effect of circumferential grooves on the retention of cemented cast copings on implant abutments. MATERIAL AND METHODS: Sixty similarly-shaped implant abutments were divided into 4 groups (n=15): without grooves, with 1 groove, with 2 grooves, and with 3 grooves. Fifteen identical NiCr cast copings were prepared to fit all 60 abutments. The castings were cemented to each group of abutments with a noneugenol provisional cement (Tempbond NE) and a zinc phosphate cement (Harvard). After thermal cycling and storage for 6 days in a water bath, retention tests were conducted with a tensile testing machine (Instron) (5 mm/min) and retentive forces were recorded. Data were subjected to 1 way-ANOVA, Tukey's (HSD) test, and repeated measures ANOVA (α=.05). RESULTS: For the noneugenol temporary cement, group retention values were increased according to the number of grooves (P<.001). For the zinc phosphate cement, the first groove increased the retention by approximately 60% (P<.001). The retentive values were higher for the zinc phosphate cement than the provisional cement. The influence of the grooves depended on the type of cement used (P<.001). Cement remnants were found primarily on the castings for provisional cement and for the plain abutments cemented with zinc phosphate cement. Remnants were found primarily on the abutments for the grooved abutments cemented with zinc phosphate cement. CONCLUSIONS: The addition of circumferential grooves to implant abutments increased the retention of cement-retained castings. For zinc phosphate cement, 1 groove was as effective as several, whereas for the provisional cement, the retention increased gradually with additional grooves.

Understanding mineral trioxide aggregate/Portland-cement: a review of literature and background factors.

AIM: This was to carry out a review of the literature concerning mineral trioxide aggregate (MTA) and Portland cement with regards to clinical, biological and mechanical findings and a possible substitution of MTA through Portland cement for endodontic use. STUDY DESIGN: Electronic literature search of scientific papers from January 1993 to January 2009 was carried out on the MEDLINE and Scopus databases using specific key words. In total, 57 papers were identified that dealt with MTA and Portland cement in a relevant way. RESULTS: The review of 50 papers conforming to the applied criteria showed that MTA and Portland cements have the same clinical, biological and mechanical properties. In animal experiments and technical characterisations both materials seemed to have very similar properties. The only difference is bismuth oxide in MTA added for better radio opacity. It seems likely that MTA materials are based on industrial Portland cements mixed with bismuth oxide. More studies, especially some long-term studies comparing MTA and Portland cement, are necessary. CONCLUSION: The existing literature gives a solid base for clinical studies with Portland cement in order to replace MTA as an endodontic material. Portland cement could be a substitute for most endodontic materials used in primary teeth.

Radiopacity and histological assessment of Portland cement plus bismuth oxide.

OBJECTIVE: The present study evaluated the subcutaneous connective tissue reactions and the radiopacity of MTA, Portland cement (PC), and Portland cement plus bismuth oxide (BO). STUDY DESIGN: Forty rats were divided into 5 groups (n = 8 per group): A1: Control (empty capsule); A2: Pro-Root MTA; A3: PC; A4: PC + BO 1:1; and A5: PC + BO 2:1. Polyethylene tubes were filled with the test materials and standardized radiographic images were taken. Histological evaluation was done after 7 and 60 days. Student t test and Fisher's test were used in the statistical analysis (P < .05). RESULTS: The radiopacity of the materials were in decreasing order: A2 > A4 > A5 > A3. No differences were found for the tissue response in the 2 experimental periods. A positive correlation between BO concentration and radiopacity of PC was determined. CONCLUSION: The histological evaluation suggests that all studied materials were biocompatible at 7 and 60 days.

All-ceramic single-tooth restorations: choosing the material to match the preparation--preparing the tooth to match the material.

The shape of a crown preparation is the prime determinant for the choice of material for an all-ceramic restoration. One essential factor is the available space for the restoration, which requires a certain occlusal thickness. The dentist's preparation design determines the available vertical clearance, and the dental technician has the responsibility of advising the dentist with regard to either choosing the right material to match the preparation or to preparing the tooth to match the material. Assuming a minimum static fracture strength of > 2000 N, the following materials can be used for all-ceramic crowns: Laboratory surveys have shown that in most situations, the available occlusal clearance in clinical reality is only 0.8 to 0.9 mm (after cementing). This shows that the available space will often be insufficient for providing monoblock crowns and still on the tight side for veneered oxide ceramics (In Ceram, zirconia, etc.). However, crowns made of veneered oxide ceramics are much more complex to fabricate and much more expensive. By simply providing a minimal occlusal thickness of 1.5 mm, the treatment provider could therefore easily facilitate the use of the much more economical monoblock crowns without compromising either esthetics or strength. Actually, crowns with veneered oxide ceramic copings do not offer any higher fracture resistance compared to Mark II crowns as long as the minimum thickness requirements are met. The flexural strength of CAD/CAM-fabricated lithium disilicate rods is about twice that of CAD/CAM-fabricated Mark II rods. When used for crowns with a wall thickness of 1.5 mm, however, both materials exhibit the same fracture strength of between 2000 and 2500 N. This is related to the different reinforcing action of the adhesive luting agent, which is essentially required for both these materials. When choosing a material, preparation shapes, technical complexity and cost should be thoroughly compared and scrutinized and should figure prominently in the discussions between dentists and dental technician. Unfavorable preparation shapes for single crowns will necessitate compromises in terms of the choice of materials that result in high cost but do not offer anything in the way of higher fracture resistance. What constitutes an appropriate all-ceramic restoration for a single tooth? Do all-ceramic single crowns require the same material bulk as multi-unit bridges? Everything would indicate that a suitable preparation geometry allows feldspathic ceramic monoblock crowns to be milled that do not require any extensive finishing efforts such as thermal annealing or in-laboratory veneering while at the same time demanding no compromises in terms of esthetics and load-bearing capacity.

Assessment of the tensile strength of hexagonal abutments using different cementing agents.

The aim of this study was to assess the uniaxial tensile strength after thermal cycling in replicas of CeraOne abutments (abutment and coping sets), using four types of cements (n = 10). A zinc phosphate cement (Fosfato de Zinco/ SSW), a resin-modified glass ionomer cement (RelyX luting / 3M-ESPE), a zinc oxide-eugenol cement (ZOE/ SSW) and a zinc oxide cement without eugenol (TempBond NE/ KERR) were used. After cementation, the samples were submitted to thermal cycles (1,000 cycles, 5 degrees C +/- 2 degrees to 55 degrees C +/- 2 degrees) for thirty seconds in each bath. Next, the samples were submitted to the tensile test in a universal test machine (0.5 mm/min). The data were submitted to ANOVA and the Tukey-Kramer test (p < 0.05), and statistically significant difference was found among the cements. The highest tensile strength mean value found was for zinc phosphate cement (33.6 kgf) followed by the resin-modified glass ionomer cement (20.5 kgf), zinc oxide-eugenol cement (8.4 kgf) and the temporary cement (3.1 kgf). Therefore, it was found that the permanent cements presented higher tensile strength, and the temporary cement could be used in situations requiring reversibility and the removal of cemented dental implant-supported prostheses.