Transferring Occlusal Anatomy from Worn Temporary Crowns to Zirconium Oxide Crowns.

Purpose/Aim: To evaluate the accuracy of transferring the occlusal anatomy of provisional crowns to monolithic zirconium oxide crowns. Materials and Methods: From a prepared typodont-tooth (#36), ten CAD/CAM provisional polymethylethacrylate crowns were fabricated with the E4D system. Each provisional crown had its occlusion adjusted. They were scanned (E4D) and the .stl files of the crown preparations were merged with the files from the adjusted crowns (3 shape software) to produce ten polished monolithic zirconium oxide crowns. For comparison, provisional and monolithic zirconium oxide crowns were scanned (True-Definition scanner), the .stl files aligned, converted into a normalized 76x76-matrix, analyzed with ANOVA with repeated measures and Tukey's test. To generate deviation distribution tables and difference plots, .stl files (provisional crowns and monolithic zirconium oxide crowns) were merged with Geomagic software. Results: There were significant differences between provisional crowns and monolithic zirconium oxide crowns. The differences were manly in the fissure area. 86% of the calculated deviations were between + 0.06mm and - 0.04mm, 42.4% of all data points were within ± 0.022mm with a SD of 0.005mm. The main differences were in the fissures, requiring clinically none or only minimal occlusal adjustments for these zirconium oxide crowns.

Temporary Tooth Separation to Improve Assessment of Approximal Caries Lesions: A School-Based Study.

CLINICAL RELEVANCE: Radiographic lesion depth should not be used as the single determinant of the restorative threshold for clinically inaccessible approximal caries lesions. Temporary tooth separation is a feasible and effective diagnostic aid for assessment and appropriate management of approximal lesions. SUMMARY: In the era of tooth-preserving dentistry, the decision to restore approximal caries lesions must be based on the accurate assessment of tooth cavitation, as the accumulation of oral biofilms in these areas encourages lesion progression. However, lesions radiographically into dentin remain the main threshold criterion for restoring approximal lesions even though most of these lesions may not be cavitated. A school-based clinical protocol for temporary tooth separation (TTS) was developed to improve visual-tactile assessment and management of clinically inaccessible approximal lesions. TTS data retrieved from electronic health records were used to correlate radiographic lesion depth and surface cavitation status with lesion location and the patient's caries risk and to evaluate the effectiveness of TTS as a diagnostic aid for approximal lesions. Of the 206 lesions assessed, 66.5% (n=137) were located in the maxillary arch, 56.6% (n=116) in distal surfaces, 61.3% (n=114) in premolars, and 21.5% (n=40) in molars. After tooth separation, 79.6% (n=164) of the lesions were diagnosed as noncavitated, including 90% (n=66) of the lesions radiographically at the inner half of enamel (E2) and 66% (n=49) of those at the outer-third of dentin (D1). Logistic regression analysis using E2 and D1 lesions showed no significant association between lesion depth or cavitation status with lesion location and caries risk. TTS is a feasible and effective diagnostic aid for the assessment and appropriate management of approximal caries lesions. There is a need to reevaluate the use of radiographic lesion depth as the single determinant of the restorative threshold for clinically inaccessible approximal lesions.

The Combination of CQ-amine and TPO Increases the Polymerization Shrinkage Stress and Does Not Improve the Depth of Cure of Bulk-fill Composites.

OBJECTIVES: To evaluate the effect of combining camphorquinone (CQ) and diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide (TPO) on the depth of cure and polymerization shrinkage stress of bulk-fill composites. METHODS AND MATERIALS: Experimental bulk-fill composites were produced containing equal molar concentrations of either CQ-amine or CQ-amine/TPO. The degree of in-depth conversion through each millimeter of a 4-mm-thick bulk-fill increment was evaluated by Fourier transform near-infrared microspectroscopy using a central longitudinal cross section of the increment of each bulk-fill composite (n=3). Light-transmittance of the multi-wave light-emitting diode (LED) emittance used for photoactivation (Bluephase G2, Ivoclar Vivadent) was recorded through every millimeter of each bulk-fill composite using spectrophotometry. The volumetric shrinkage and polymerization shrinkage stress were assessed using a mercury dilatometer and the Bioman, respectively. The flexural modulus was also assessed by a three-point bend test as a complementary test. Data were analyzed according to the different experimental designs (α=0.05 and ß=0.2). RESULTS: Up to 1 mm in depth, adding TPO to CQ-based bulk-fill composites increased the degree of conversion, but beyond 1 mm no differences were found. The light-transmittance of either wavelengths emitted from the multi-wave LED (blue or violet) through the bulk-fill composites were only different up to 1 mm in depth, regardless of the photoinitiator system. Adding TPO to CQ-based bulk-fill composites did not affect volumetric shrinkage but did increase the flexural modulus and polymerization shrinkage stress. CONCLUSION: Adding TPO to CQ-based bulk-fill composites did not increase the depth of cure. However, it did increase the degree of conversion on the top of the restoration, increasing the polymerization shrinkage stress.

The Use of Different Photoinitiator Systems in Photopolymerizing Resin Cements Through Ceramic Veneers.

OBJECTIVE: To evaluate the effect of different photoinitiator systems on photopolymerizing resin cements through ceramic veneers with different thickness on microshear bond strength (µSBS), flexural strength (FS), and ultimate tensile strength (UTS) and verify the light attenuation through these ceramic veneers. METHODS AND MATERIALS: Four photopolymerizing experimental resin cements were produced with the same resin matrix and associated with four different photoinitiator systems: camphorquinone (CQ), diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide (TPO), Ivocerin, and TPO + Ivocerin. Eighty disc-shaped ceramic veneers (IPS Empress Esthetic, Ivoclar Vivadent) were fabricated (10-mm diameter) in two different thicknesses: 0.7 and 1.5 mm. A previously characterized multiwave LED (Bluephase G2, Ivoclar Vivadent) was standardized for 40 seconds of photoactivation. Light transmittance through each ceramic veneer thickness (n=5) was measured using a spectrometer (USB 2000, Ocean Optics). The µSBS of each resin cement (n=15) to the ceramic veneer was evaluated using 0.5-mm cylinders with 0.7-mm diameters photoactivated through the different ceramic veneer thicknesses. Samples for FS and UTS tests were made either with or without ceramics veneers (0.7 and 1.5 mm) fixed to the light-curing tip. Data were submitted to two-way analysis of variance and the Tukey test (α=0.05). RESULTS: The multiwave LED emitted higher irradiance into the blue wavelength spectra than into the violet wavelength spectra (p=0.0001). Light transmittance through the ceramic veneers was reduced in a systematic manner based on thickness regardless of the wavelength spectra emitted from the multiwave LED (p=0.00037). The µSBS was reduced in a systematic manner based on thickness regardless of the photoinitiator system (p<0.05). However, resin cements with CQ and Ivocerin showed higher bond strength values in comparison to the resin cement with TPO regardless of the ceramic veneer thickness (p<0.05). The FS and UTS means decreased (p<0.05) with the interposition of 0.7- and 1.5-mm ceramic veneers for all resin cements. The resin cement containing only TPO showed the lowest FS and UTS means (p<0.05) for all ceramic veneers. CONCLUSIONS: The thickness of the ceramic veneers reduced the irradiance of the multiwave LED in all wavelength spectra. Ivocerin alone or associated with TPO showed to be an effective alternative photoinitiator to substitute for CQ. The resin cement containing only TPO had lower bond strength values in comparison to resin cements with CQ, Ivocerin, and Ivocerin + TPO.

Effect of Different Adhesive Systems Used for Immediate Dentin Sealing on Bond Strength of a Self-Adhesive Resin Cement to Dentin.

OBJECTIVE: The purpose of this study was to investigate the immediate and three-month water storage behavior of adhesives when used for immediate dentin sealing (IDS). METHODS AND MATERIALS: Four adhesive systems were used to perform IDS: a one-step self-etch (Xeno V), a two-step self-etch (Clearfil SE Bond), a two-step etch-and-rinse (XP Bond), and a three-step etch-and-rinse (Optibond FL). For the control group, IDS was not performed. The self-adhesive resin cement RelyX Unicem was used for the luting procedures. After seven days of water storage, specimens (n=6) were sectioned into beams (n=5) with an approximately 1-mm2 cross-sectional area. Half of the specimens were tested in tension after seven days of water storage at 37°C, while the other half was stored for three months prior to testing in tension using a universal testing machine (1 mm/min). The failure pattern was determined using a stereomicroscope and scanning electron microscopy. Microtensile bond strength (µTBS) data were statistically analyzed by two-way analysis of variance and Tukey post hoc test (α=0.05). RESULTS: After seven days, the control group presented the lowest µTBS but did not differ from XP Bond and Clearfil SE Bond. After three months, there was no µTBS difference between the IDS groups and the control. CONCLUSIONS: After seven days of water storage, the groups with IDS presented higher µTBS values than the control group, although XP Bond and Clearfil SE Bond did not present significant differences. However, after three months of storage in water, IDS groups did not differ significantly from control group, which did not receive IDS.

A Measurement Protocol for the Marginal and Internal Fit of All-Ceramic Crowns.

AIMS: To evaluate in vitro the influence of firing on marginal and internal fit of all-ceramic milled and pressed lithium-disilicate crowns. MATERIALS AND METHODS: One Standardized model with 1.6mm occlusal and 1.4mm axial reduction was used to fabricate 64 crowns. Using a factorial design, eight groups of lithium disilicate ceramics (n=8) using P=press, C=CAD/CAM, M=monolithic, O=coping, V=veneered, R=as produced: PMR, PMG, POR, PVG, CMR, CMG, COR, CVG. Crowns were produced and cemented on stone dies, then embedded in clear epoxy resin and sectioned into two plains. With a digital microscope, the distance between die and crowns was measured at the occlusal and axial walls. The horizontal/vertical fit at the finishing line of each section were measured as well. RESULTS: For the marginal fit, the analysis shows that the influence of material and design was significant on horizontal and vertical margins, and the influence of finish was significant with horizontal but not vertical margins (p=0.09). For the internal fit, the analysis showed that the axial gap was significantly influenced by material and finish but not by design (p=0.44). CONCLUSIONS: With a few exceptions, horizontal and vertical marginal discrepancies were below 100 µm. Additional firing increased the discrepancies.

Influence of cavity preparation, light-curing units, and composite filling on intrapulpal temperature increase in an in vitro tooth model.

This study examined the effect of both the tooth substance and restorative filling materials on the increase in pulp chamber temperature when using light-curing units with different power densities. The tip of a temperature sensor was positioned on the pulpal dentinal wall of the buccal side of a maxillary premolar. Metal tubes were inserted in the palatal and buccal root of the tooth, one for water inflow and the other for water outflow. Polyethylene tubes were connected from the metal tubes to a pump to control the flow rate. For the unprepared tooth group (group 1), the tooth was light-cured from the buccal side using two light-curing units (three curing modes): the VIP Junior (QTH, BISCO, Schaumburg, IL, USA) and the Bluephase LED light-curing units (two modes: LEDlow and LEDhigh; Ivoclar Vivadent, Schaan, Liechtenstein). The power densities of each light-curing unit for the LEDlow, QTH, and LEDhigh modes were 785 mW/cm(2), 891 mW/cm(2), and 1447 mW/cm(2), respectively. All light-curing units were activated for 60 seconds. For the prepared tooth group (group 2), a Class V cavity, 4.0 mm in width by 4.0 mm in height by 1.8 mm in depth in size, was prepared on the buccal surface of the same tooth for the temperature measurement. The light-curing and temperature measurements were performed using the same methods used in group 1. The cavity prepared in group 2 was filled with a resin composite (Tetric N Ceram A3 shade, Ivoclar Vivadent) (group 3) or a flowable composite (Tetric N Flow with A3 shade, Ivoclar Vivadent) (group 4). The light-curing and temperature measurements were performed for these groups using the same methods used for the other groups. The highest intrapulpal temperature (TMAX) was measured, and a comparison was conducted between the groups using two-way analysis of variance with a post hoc Tukey test at the 95% confidence level. The TMAX values were as follows: 38.4°C (group 1), 39.0°C (group 2), 39.8°C (group 3), and 40.3°C (group 4) for the LEDlow mode. For the QTH mode, the TMAX values were 40.1°C (group 1), 40.4°C (group 2), 40.9°C (group 3), and 41.4°C (group 4). For the LEDhigh mode, the TMAX values were 43.3°C (group 1), 44.5°C (group 2), 44.7°C (group 3), and 45.3°C (group 4). The statistical analysis revealed the following: the TMAX values were arranged by mode in the following manner: LEDlow < QTH < LEDhigh (p<0.05) and group 1 < group 2 ≤ group 3 ≤ group 4 (p<0.05).

Sealing properties of a new root canal sealer.

AIM: To evaluate bacterial leakage of Apexit Plus, a new root canal sealer, in comparison with AH Plus. METHODOLOGY: A total of 56 single-rooted human teeth were randomly divided into two experimental groups of 16 roots and two control groups. Roots were filled by lateral condensation with Gutta-percha and AH Plus or with Gutta-percha and Apexit Plus. A split chamber microbial leakage model was used in which Streptococcus mutans placed in the upper chamber could reach the lower chamber only through the filled canal. Positive controls were filled only with Gutta-percha and tested with bacteria, whereas negative controls were sealed with wax to test the seal between chambers. Additionally, film thickness, solubility and dimensional change were determined. RESULTS: All positive controls leaked within 24 h, whereas none of the negative controls leaked after 30 days. Apexit Plus had significant less bacterial leakage (log-rank test, P < 0.0001) than AH Plus. AH Plus (0.3% solubility) showed a slightly lower solubility than Apexit Plus (0.5% solubility) but a larger film thickness (28 vs. 11 mum) according to ISO 6876:2001. CONCLUSION: Apexit Plus had a better sealing ability in comparison with AH Plus.

Recommendations for conducting controlled clinical studies of dental restorative materials.

About 35 years ago, Ryge provided a practical approach to evaluation of clinical performance of restorative materials. This systematic approach was soon universally accepted. While that methodology has served us well, a large number of scientific methodologies and more detailed questions have arisen that require more rigor. Current restorative materials have vastly improved clinical performance and any changes over time are not easily detected by the limited sensitivity of the Ryge criteria in short term clinical investigations. However, the clinical evaluation of restorations not only involves the restorative material per se but also different operative techniques. For instance, a composite resin may show good longevity data when applied in conventional cavities but not in modified operative approaches. Insensitivity, combined with the continually evolving and non-standard investigator modifications of the categories, scales, and reporting methods, has created a body of literature that is extremely difficult to meaningfully interpret. In many cases, the insensitivity of the original Ryge methods is misinterpreted as good clinical performance. While there are many good features of the original system, it is now time to move to a more contemporary one. The current review approaches this challenge in two ways: (1) a proposal for a modern clinical testing protocol for controlled clinical trials, and (2) an in-depth discussion of relevant clinical evaluation parameters, providing 84 references that are primarily related to issues or problems for clinical research trials. Together, these two parts offer a standard for the clinical testing of restorative materials/procedures and provide significant guidance for research teams in the design and conduct of contemporary clinical trials. Part 1 of the review considers the recruitment of subjects, restorations per subject, clinical events, validity versus bias, legal and regulatory aspects, rationales for clinical trial designs, guidelines for design, randomization, number of subjects, characteristics of participants, clinical assessment, standards and calibration, categories for assessment, criteria for evaluation, and supplemental documentation. Part 2 of the review considers categories of assessment for esthetic evaluation, functional assessment, biological responses to restorative materials, and statistical analysis of results. The overall review represents a considerable effort to include a range of clinical research interests over the past years. As part of the recognition of the importance of these suggestions, the review is being published simultaneously in identical form in both the "Journal of Adhesive Dentistry" and the "Clinical Oral Investigations." Additionally an extended abstract will be published in the "International Dental Journal" giving a link to the web full version. This should help to introduce these considerations more quickly to the scientific community.

Effect of exponential polymerization on color stability of resin-based filling materials.

PURPOSE: To investigate the influence of a halogen light curing device used with constant or exponential polymerization mode on the color stability of contemporary resin-based filling materials. MATERIALS AND METHODS: Eight samples of Charisma (CH), Durafill (DU), Definite (DE), and Dyract AP (DY) each were light-cured with constant power or with soft-start mode (Translux Energy) for 20, 40 or 60s. The CIE-Lab-values (L(*), a(*), b(*)) were measured prior to and after performing dry aging, water aging or a Suntest (EN ISO 7491) and Delta L-, Delta a-, Delta b-, and Delta E-values were calculated. RESULTS: Statistical analysis (GLM and repetition of measures) showed significant changes (p<0.05) of the color values for each material's curing mode and time after each of the aging processes. Four-way ANOVA revealed significant differences (p<0.05) between Delta L-, Delta a-, Delta b-, and Delta E of the materials in dependence on the curing time and mode and aging condition. Exponentially-cured DU was the most color-unstable material after aging in water followed by the 20s exponentially cured DE and CH samples. After the Suntest, DY showed significant bleaching (negative Delta b) and the largest Delta E for all curing times and modes followed by the DE samples. DU and CH were the most color-stable materials in this test. SIGNIFICANCE: The extent of discoloration depends on the (a) curing time, (b) curing mode, (c) aging condition, and (d) material. For the constant curing mode, 40s curing time for the exponential 60s seems to be appropriate.