Biomedical subjects

Frederick A Rueggeberg

Publications and source records attributed to Frederick A Rueggeberg.

At least 19 recordsLinked to original sources

PubMed2007

Effect of composite temperature on in vitro intrapulpal temperature rise.

OBJECTIVES: To measure in vitro intrapulpal temperature when placing and restoring with either room-temperature or pre-heated (54 and 60 degrees C) composite. METHODS: A K-type thermocouple was placed in the pulpal chamber of an extracted, human bifurcated upper premolar which had a Class V preparation (1 mm remaining dentin thickness) on the facial surface. Tooth roots were immersed in a thermostatically controlled water bath and perfused with water at 1.25 microl/min to simulate physiological circulation in the pulp chamber. The thermocouple was connected to an analog-to-digital converter. The preparation was filled using composite either at room-temperature, or pre-heated to 54 or 60 degrees C with a commercial compule heater (Calset), using standard clinical procedures by one person while continuously monitoring intrapulpal temperature (n=5). Temperature rise over baseline values were determined at various stages during the restoration process: composite placement, contouring, prior to light-curing, and immediately after light-curing (20s, Optilux 501). At each measurement interval, intrapulpal temperature values were compared using ANOVA and the Tukey-Kramer post hoc test (alpha=0.05). RESULTS: Significant differences were found in intrapulpal temperature when comparing pre-heated and room-temperature composite treatments with respect to baseline among the stages of the restorative process. However, the extent of this increase with heated composite was only 0.8 degrees C. A 5 degrees C intrapulpal temperature rise was seen for all groups during photopolymerization. SIGNIFICANCE: Use of pre-heated composite only mildly increased intrapulpal temperature values when compared to composite delivered at room-temperature in an in vitro test environment. The largest temperature change occurred with application of the curing light.

Acrylic Resins↗

PubMed2007

Infiltration/evaporation-induced shrinkage of demineralized dentin by solvated model adhesives.

During dentin bonding, solvated adhesive comonomers are applied to water-saturated decalcified dentin matrices. When alcohol-solvated hydrophilic or hydrophobic methacrylate monomers are applied, they chemically remove water and cause matrix shrinkage during comonomer infiltration. Evaporation of solvent induces further shrinkage. The purpose of this work was to compare the shrinkage of water-saturated dentin matrices infiltrated with ethanol- or methanol-solvated 2-hydroxyethyl methacrylate (HEMA), 2,2-bis[4(2-hydroxy-3-methacryloyloxy-propyloxy)-phenyl] propane (BisGMA), or triethyleneglycol dimethacrylate (TEGDMA) at 90/10, 70/30, 50/50, and 30/70 mass fraction % alcohol/monomer before and after evaporation of alcohol. Thin (ca 0.2 mm) disks of human mid-coronal dentin were demineralized and placed in a well beneath the contact probe of a linear variable differential transformer (LVDT). The height of the matrix was measured before and after random application of one of the twelve alcohol/monomer mixtures. Matrix height was measured during infiltration and during solvent evaporation. Between trials, residual monomer was extracted using ethanol. These studies were repeated on specimens in which 100% alcohol was used to substitute for water in the matrix. Both studies revealed that matrices shrink 30-50% but that pretreatment of matrices with alcohol prevents BisGMA phase separations from occurring. Wet bonding with ethanol instead of water permits infiltration of relatively hydrophobic alcohol/monomers.

Adhesives↗

PubMed2007

Effects on microstrain and conversion of flowable resin composite using different curing modes and units.

The flowable resin composite, Tetric Flow, was used to measure microstrain and degree of conversion after hardening with each of three curing machines: XL3000(XL) for 10, 20, 30, and 40 s; Optilux 501 using conventional mode (OC) for 10, 20, 30, and 40 s, as well as Optilux boost (OB, 10 s) and ramp modes (OR, 20 s); and LEDemetron (LEDe) for 10, 20, 30, and 40 s. The emitted power density and spectral distribution of the three light curing units were also measured. The LEDe output energy spectrum was centralized between 425 and 490 nm, which encompasses the excited wavelength of camphorquinone. The microstrain produced by the curing process is as a second-degree polynomial for each light source. The OB microstrain was highest, while the OR microstrain was lower. The ranking in order of degree of monomer conversion was as follows: XL10 <or=<or= OC10 <or=<or= LED 10 = OR = XL 20 = OC 20 = XL 30 <or=<or= LED 20 <or=<or= OC30 = LED 40 = XL 40 = OC40 = LED 30 <or= OB. The degree of conversion cured with OB was significant higher than other curing modes except OC30, OC40, LEDe30, LEDe40, and XL40. The conversion value of XL10 was the lowest. The LEDe produced higher conversion for the same emitted energy compared to the two halogen units.

Composite Resins↗

PubMed2006

Comparison of seal after obturation techniques using a polydimethylsiloxane-based root canal sealer.

A polydimethylsiloxane-based sealer (GuttaFlow) was used for filling single-rooted teeth with four obturation techniques. Prefitted gutta-percha master-cones were employed in groups 1 to 3 with backfilling of the sealer. Apical third of the roots were first filled with GuttaFlow, and sealer-coated master cones were seated with up-and-down motion (group 1) or rotated to place (group 2). Master-cones were used as carriers for introducing GuttaFlow into the canals (group 3). Canals were filled with GuttaFlow without master-cones (group 4). Canals were filled with AH Plus/gutta-percha using warm vertical compaction (control group 5). All obturated canals were tested for leakage after 1, 6, and 12 weeks using the fluid filtration technique. All groups exhibited equivalent seal regardless of time except for more extensive leakage in group 3. The use of GuttaFlow with a single gutta-percha master cone creates an apical seal that is equivalent to that produced with gutta-percha/AH Plus sealer using warm vertical compaction.

Analysis of Variance↗

PubMed2006

Use of fluorescent compounds in assessing bonded resin-based restorations: a literature review.

OBJECTIVES: This work reviews fundamental concepts involved with fluorescent imaging in the dental materials field. DATA: Fluorescent dyes have been widely used: incorporated into adhesive system components, placed in the pulp chamber and allowed to diffuse toward the restorative interface, as well as used as a visible tracer in microleakage tests. CONCLUSIONS: Although use of fluorescent imaging has substantially contributed to the existing knowledge base, there is no standardized methodology used, and as a result, interpretation of study results as well as comparison of results among studies remains questionable.

Composite Resins↗

PubMed2006

Net expansion of dried demineralized dentin matrix produced by monomer/alcohol saturation and solvent evaporation.

The purpose of this work was to determine if nonaqueous methacrylate monomer/alcohol mixtures could expand dried collapsed demineralized dentin matrix. Thin disks (ca. 200 microm) of human dentin were demineralized and placed in wells beneath contact probes of linear variable differential transformers. The probes were placed on water-saturated expanded matrices to record the shrinkage associated with drying. Monomer mixtures containing hydroxyethyl methacrylate, 2,2-bis[4-(2-hydroxy-3 methacryloyloxy)propoxyphenyl] propane, or triethyleneglycol dimethacrylate were mixed with methanol or ethanol at alcohol/monomer mass fraction % of 90/10, 70/30, 50/50, or 30/70. They were randomly applied to the dried matrices to determine the rate and magnitude of expansion; then shrinkage was recorded during evaporation of the alcohols. The results indicated that matrix expansion was positively correlated with the Hoy's solubility parameters for hydrogen bonding forces (delta(h)) of the monomer/solvent mixtures (p < 0.001). Expansions were more rapid with methanol-containing than with ethanol-containing monomer mixtures. For the test solutions, triethyleneglycol dimethacrylate-containing mixtures produced the slowest rate of matrix expansion and hydroxyethyl methacrylate-containing mixtures the most rapid expansion. When the solvents were evaporated, the matrix shrank in proportion to the solvent content and the delta(h) of the monomer-solvent mixtures. The results indicate that expansion of dried, collapsed dentin matrices requires that the delta(h) of the mixtures be larger than 17 (J/cm(3))(1/2). The greater the delta(h) of the monomer solutions, the greater the rate and extent of expansion.

Alcohols↗

PubMed2006

Effect of temperature on unpolymerized composite resin film thickness.

STATEMENT OF PROBLEM: Room temperature (RT) composite resins are viscous, and this condition may affect the ability of the material to flow and adapt to preparation walls. PURPOSE: The purpose of this study was to compare the film thickness of a variety of commercial composite resins heated prior to light polymerization. The film thickness of these heated materials was also compared to those of flowable products at RT. MATERIAL AND METHODS: Five flowable and 7 conventional composite resins were used: 2 microfills, a nanofill hybrid, 2 submicron hybrids, a trimodal hybrid, and a packable. Composite resin (0.05 mL) was pressed between 2 Mylar-covered glass plates (15 kg) for 180 seconds, light polymerized, and the thickness measured using a micrometer. When comparing conventional composite resin heated to 54 degrees C or 60 degrees C, the RT value was control, while the RT flowable values were control when compared to heated composite resin. (n=5/group). Data were analyzed using 1- and 2-way analysis of variance and the Tukey-Kramer post hoc test (alpha=.05). Correlation of filler content to flow potential was evaluated. Scanning electron microscopic analysis of polymerized specimens was characterized by filler size and shape. RESULTS: Room temperature conventional composite resin values varied in film thickness. Not all preheated products reduced in thickness. Thickness of the nanofill did not reduce, and one of the submicron hybrids reduced the greatest. No correlation existed between composite resin classification, filler content or shape, and film thickness. No difference in thickness existed between composite resins preheated to 54 degrees C and 60 degrees C. Room temperature and preheated conventional composite resin provided film thickness greater than that of flowable materials. CONCLUSIONS: Preheating conventional composite resin yields lower film thickness for some products, but flow cannot be attributed to composite resin classification, filler content, or shape. Preheated composite resin thickness was greater than that of all flowables.

Acrylic Resins↗

PubMed2006

Clinically relevant issues related to preheating composites.

STATEMENT OF THE PROBLEM: Issues regarding the use of composite preheating need to be investigated so that the clinician will better understand the variables associated with this method. PURPOSE: To examine the multiple aspects of use of a commercial composite preheating device (Calset, AdDent Inc., Danbury, CT, USA). MATERIALS AND METHODS: Temperature values of three heating units and composite compules were obtained using a K-type thermocouple and were recorded digitally in real time. The following parameters were measured: maximum heater and composite temperature and its stability upon storage, composite temperature change when removed from the heater and injected, the effect of delivery system on ejected composite temperature, and the effect of repeated and extended preheating on composite monomer conversion (using infrared spectroscopy). Monomer conversion was measured after repeated composite cycling (from room temperature [RT] to 60 degrees C, 10x) or extended preheating (24 hours at 60 degrees C), and values were compared with composite maintained at RT (control group). Among test parameters, data (N=5 for each parameter) were analyzed using Student's t-test, analysis of variance, and the Tukey-Kramer post-hoc test where appropriate (alpha=0.05). RESULTS/CONCLUSIONS: Two of the three tested units achieved the stated preset temperatures. Composite attained temperature values close to the heating unit. Composite temperature drop upon removal from the heater was dramatic: within 2 minutes a 50% temperature drop was noted. Heating the compule while preloaded in the syringe provided higher delivery temperatures than heating the compule separately (p < 0.00). Optimum results were achieved when preheated composite was dispensed and used as quickly as possible. Neither repeated nor extended preheating of composite significantly affected monomer conversion. CLINICAL SIGNIFICANCE: Preheating composite has potential benefits, but should be used with knowledge of its limitations. Reheating of unused composite does not affect its degree of conversion, thus decreasing material waste. Heating of the composite preloaded in the delivery syringe enhances the temperature of extruded composite.

Acrylic Resins↗

PubMed2006

A new technique for assessing hybrid layer interfacial micromorphology and integrity: two-photon laser microscopy.

PURPOSE: This study describes a two-photon laser fluorescence microscopy technique developed to evaluate the interfacial micromorphology of the hybrid layer in bonded restorations. MATERIALS AND METHODS: Micropermeability of the hybrid layer was characterized by means of simultaneously contrasting a dye-containing adhesive with a differently colored dye placed into the pulp chamber and allowed to diffuse toward the different-colored hybrid layer. A fluorescent red dye (rhodamine B) was incorporated into a commercial dentin bonding agent. Class I preparations (margins in enamel) were made on extracted human third molars. The teeth were restored using conventional methods: bonding agent, composite, finishing, and polishing. An aqueous solution of a yellow/green dye (fluorescein) was then placed into the pulp chamber for 3 h, allowing time to diffuse toward the different-colored bonded interface. The teeth were then embedded, sectioned, and microscopically analyzed using two-photon laser microscopy at 40X magnification. RESULTS: Subsurface fluorescent imaging using this technique enabled interfacial micromorphology to be characterized at submicrometer resolution and provided high-contrast images. The quality of surrounding structures and potential presence of gaps were also precisely assessed. CONCLUSION: Two-photon laser microscopy provided high quality, high-resolution images of the bonded interface and surrounding areas, allowing accurate qualitative and quantitative analysis of the structure and integrity of the hybrid layer.

Bisphenol A-Glycidyl Methacrylate↗

PubMed2006

Factors affecting use of fluorescent agents in identification of resin-based polymers.

PURPOSE: The present study is a compilation of methodologies developed in order to evaluate the effects of addition of a fluorescent agent, rhodamine B, to resin-based materials. The intent of the work was to develop a systematic methodology that accounts for variables not shown to be of concern in past testing, but may significantly affect interpretation of the resulting images and material properties. MATERIALS AND METHODS: Different methodologies were specifically developed to evaluate factors affecting the use of the fluorescent agent rhodamine B in the identification of resin-based materials. The influence of dye concentration was evaluated with respect to adhesive polymerization reaction kinetics and bond strength of the resin into which the dye is added. The pH of the dye-solvent solution was also considered. Additionally, the mass and percentage of rhodamine B leached into different media over time was determined. RESULTS: It was demonstrated that a specific dye must be used with caution, and the concentration of a fluorescent agent is important with respect to both the conversion and bond strength of the resin to which the dye is added. An alcohol-based dye solution also produced an extremely high amount of dye leaching from polymerized specimens. The adhesive pH was not altered. CONCLUSION: The standardized methodology developed here to analyze restoration interfaces using a fluorescent dye can lessen the impact of variables when interpreting results.

Composite Resins↗

PubMed2006

Bond strength of resin-based restorations polymerized with different light-curing sources.

PURPOSE: To evaluate the influence of different light-curing units on microtensile bond strength of resin composite restorations. MATERIALS AND METHODS: Standardized Class I preparations (6.0 x 4.5 mm, 2.5 mm deep) were made in extracted human third molars after abrading the cusps. Resin was inserted in bulk using a 3M ESPE restorative system [Adper Single Bond (DBA)/ Filtek Z250 (RC)]. Both materials were polymerized using different light-curing units: QTH at 540 mW/cm(2) (XL 3000, 3M ESPE); LED at 750 mW/cm(2) (Elipar FreeLight2, 3M ESPE); PAC at 2130 mW/cm(2) (Arc Light II, Air Techniques). Nine different light combinations were developed to polymerize both DBA and RC: QTH/QTH; QTH/LED; QTH/PAC; LED/LED; LED/QTH; LED/PAC; PAC/PAC; PAC/QTH; PAC/LED. Restored teeth were stored in distilled water for 24 h at 37 degrees C and then sectioned, yielding stick-shaped specimens with a bonded area of approximately 0.9 mm(2). Specimens were assessed in a testing machine at a crosshead speed of 1 mm/min. The results were analyzed using two-way ANOVA and Tukey's test at a pre-set alpha = 0.05. RESULTS: The combinations PAC/QTH and QTH/QTH presented the highest bond strength values, and LED/QTH the lowest (p < 0.05). Significantly lower values were observed in combinations when the LED light was used to polymerize DBA compared to QTH and PAC lights, irrespective of the light source used to polymerize RC (p < 0.05). Same light combinations presented similar bond strength values. CONCLUSIONS: Different light sources influence restoration bond strength. Bond strength is more dependent on the light source used for DBA than for curing RC.

Bisphenol A-Glycidyl Methacrylate↗

PubMed2005

Effect of resin hydrophilicity and temperature on water sorption of dental adhesive resins.

This study examined the effects of copolymer hydrophilicity and temperature on water sorption and solubility characteristics of five copolymer blends of increasing degree of hydrophilicity using gravimetric measurements. Six resin disks (15 mm in diameter x 1 mm in thickness) were prepared from each copolymer blend and were stored in deionised water at 23, 37 and 55 degrees C. Water sorption and solubility of the resin disks were measured before and after water immersion and desiccation. Multiple regression analysis of water sorption was performed on two independent variables, copolymer hydrophilicity and temperature. Maximum water sorption increased significantly with Hoy's total cohesive energy density (delta(t)), Hoy's solubility parameter for polar forces (delta(p)) and hydrogen bonding (delta(h)), but was not influenced by temperature. However, a significant positive relationship was observed between diffusion coefficients (obtained using Fick's law of diffusion) and temperature. The water absorption activation energy was 10 kJ/mol for the most hydrophilic copolymer blend R5 and 35-51 kJ/mol for copolymer blends R1-R4. The positive relationship between maximum water uptake and copolymer hydrophilicity suggests that water molecules diffuse through the polymer matrices by binding successively to the polar sites via hydrogen bonding. Such water sorption may determine the durability of resin-dentine bonds.

Adhesives↗

PubMed2005

Efficacy of composite surface sealers in sealing cavosurface marginal gaps.

OBJECTIVES: The ability of commercially available composite surface sealers to penetrate and seal a controlled gap formed in all-enamel margin, Class V in vitro resin composite restorations in human bicuspids was examined. METHODS: A fluorescent red dye (Rhodamine B) was incorporated to a variety of commercially available composite surface sealers. The teeth were restored using acid etching, a dentin bonding agent, and a photo-activated microfilled composite, finished, polished, and sealed. The teeth were thermocycled and then immersed in an aqueous solution of a green fluorescent dye (Dextran-Fluorescein) to evaluate the sealing ability and penetration of surface sealers into the controlled gaps formed at unbonded margins. Teeth were embedded, sectioned, and images recorded using confocal microscopy. RESULTS: All sealers leaked, and use of a dentin-bonding agent to seal the gap performed better than the commercial sealing products. CONCLUSIONS: Commercial surface sealers evaluated were not able to totally seal controlled-size cavosurface gaps, and sealer penetration into the controlled gap varied greatly. Composite restorative procedures should be performed to obtain ideal marginal sealing, minimizing the need for composite surface sealers, which were found to not totally seal an exposed cavosurface margin. Use of a dentin-bonding agent may provide better sealing than commercial products developed specifically for this purpose.

Analysis of Variance↗

PubMed2005

Molar extinction coefficients and the photon absorption efficiency of dental photoinitiators and light curing units.

OBJECTIVES: The light absorption of dental photoinitiators should correlate with the spectral emission profiles of dental light curing units compared on an equivalent basis. Spectral data of dental photoinitiators and light curing units can be used to define the photon absorption efficiency (PAE) obtained by integrating the product of the absorption and emission spectra in terms of photons. This parameter can be used to identify the best performance for photochemical process with specific photoinitiators. METHODS: The efficiency of two LED and one QTH lamps were tested comparing their performances with the photoinitiators camphorquinone (CQ); phenylpropanedione (PPD); monoacylphosphine oxide (Lucirin TPO); and bisacylphosphine oxide (Irgacure 819). Absorption and emission spectra of the photoinitiators and the LED (Ultrablue I and Ultrablue IS) and QTH (Optilux 401) LCUs were determined in the 360-550nm range. RESULTS: CQ exhibited an absorption centered in the blue region and, although the maxima of PPD, MAPO, and BAPO were in the UV-A region, their absorption extended to the visible region. Power output maxima of the LCUs were at 467 (Ultrablue I), 454 (Ultrablue IS) and 493nm (Optilux 401), and the total power densities were 170+/-1, 470+/-4 and 444+/-4mW/cm(2), respectively. SIGNIFICANCE: The use of the PAE allows a prediction of the most efficient photoinitiator/LCU systems. For similar photoinitiator concentrations, Lucirin and CQ are most efficiently photoinitiated by the QTH unit, whereas the high-power LED device is more efficient for Irgacure. PPD is photoactivated similarly by both LCUs.

Acrylic Resins↗

PubMed2005

Effects of resin hydrophilicity on water sorption and changes in modulus of elasticity.

UNLABELLED: As acidic monomers of self-etching adhesives are incorporated into dental adhesives at high concentrations, the adhesive becomes more hydrophilic. Water sorption by polymers causes plasticization and lowers mechanical properties. The purpose of this study was to compare the water sorption and modulus of elasticity (E) of five experimental neat resins (EX) of increasing hydrophilicity, as ranked by their Hoy's solubility parameters and five commercial resins. METHODS: After measuring the initial modulus of all resin disks by biaxial flexure, half the specimens were stored in hexadecane and the rest were stored in water. Repeated measurements of stiffness were made for 3 days. Water sorption and solubility measurements were made in a parallel experiment. RESULTS: None of the specimens stored in oil showed any significant decrease in modulus. All resins stored in water exhibited a time-dependent decrease in modulus that was proportional to their degree of water sorption. Water sorption of EX was proportional to Hoy's solubility parameter for polar forces (delta(p)) with increasing polarity resulting in higher sorption. The least hydrophilic resin absorbed 0.55 wt% water and showed a 15% decrease in modulus after 3 days. The most hydrophilic experimental resin absorbed 12.8 wt% water and showed a 73% modulus decrease during the same period. The commercial resins absorbed between 5% and 12% water that was associated with a 19-42% reduction in modulus over 3 days.

Absorption↗

PubMed2005

LED curing lights--what's new?

Technological changes to blue light-emitting diode (LED) light-curing units have taken place at an accelerated rate. The lighting industry, however, has not yet improved output levels of blue chip design used in dental LED units as quickly. In fact, the same 5 watt source has been offered since 1992. The next step in technology advancement is the use of conventional, contemporary chips with improved output levels. These levels may arise from supplying greater electrical power to the chip, and must be accompanied by designs that will reduce internal chip heat to avoid permanent damage. A new LED light design uses periodic level shifting (PLS) to intermittently increase chip output levels over those of baseline. In doing so, maximal output from the chip can be achieved, but not at the risk of destroying the source. This article describes the current state of LED light units, discusses the strategy of chip design and limitations, and presents a description of an LED recently introduced that uses PLS technology.

Dental Equipment↗

PubMed2004

Biological effects of blue light from dental curing units.

OBJECTIVES: This study assessed the effects of three common dental photo-curing light sources (quartz-tungsten-halogen (QTH), plasma-arc (PAC), and laser) on the cellular function of fibroblasts in vitro. METHODS: Mouse fibroblasts were exposed to light from dental photo-curing units for clinically relevant durations, with total energy exposures ranging from 1.3 to 60 J/cm(2). The temperature rise of the cell-culture medium was measured to assess any possible effect from temperature increases, and cellular function was assessed by succinic dehydrogenase (SDH) activity of mitochondria. To directly compare the three light sources, additional experiments were done using equivalent total energy exposures from each source by adjusting the exposure durations for each unit. RESULTS: In experiments that used clinically relevant exposure durations for each light, exposures ranging from 5 J/cm(2) (laser) to 15 J/cm(2) (PAC, QTH) irreversibly suppressed SDH activity nearly 100% when compared to no-light controls up to 72 h post-exposure. For the PAC and QTH sources, exposures as low as 3.5 J/cm(2) also irreversibly suppressed SDH activity. When equivalent energies were used from each light source, exposures of 1 J/cm(2) did not suppress SDH activity for the QTH and laser sources, but significantly (50%) suppressed SDH for the PAC source, indicating a difference in the biological effects of the outputs of the different curing units. Equivalent energy exposure experiments also indicated a definite dependence of SDH activity on the total light energy of exposure. Temperature rises ranged from 2 to 9 degrees C, and elevated temperatures lasted for 60-300 s above the base temperature of 37 degrees C, but peak temperature and the duration of temperature elevation were not always related and depended on the light source used. SIGNIFICANCE: Results from the current study indicate that these photo-curing sources pose some risk of disrupting cellular function in vivo. Further study is necessary in other cell types and under more clinically relevant conditions to estimate the in vivo risk of photo-curing to oral tissues.

3T3 Cells↗

PubMed2004

Curing kinetics of a photo-polymerized dental sealant.

PURPOSE: To evaluate the effect of using a variety of light-curing sources on the extent (monomer conversion) and rate of cure of a light-cured dental sealant. METHODS: Infrared spectroscopy recorded real-time polymerization of a self-cured and a light-cured sealant when the latter was exposed using manufacturer's recommendations [quartz-tungsten-halogen (QTH)] for 20 seconds as well as to other light sources: high intensity QTH, plasma arc light (PAC), and second-generation blue light emitting diode (LED) units. Specimens were heated to 37 degrees C and the degree and rate of conversion were recorded at each second for 300 seconds. Conversion extent and rate were compared among light units as well as to the self-curing product. Five replications for each test condition were performed. RESULTS: After 300 seconds, self-curing product conversion was equivalent to all light-exposed specimens. The self-cured rate of cure was significantly lower than all light-cured scenarios. The high intensity QTH light provided equivalent conversion as conventional 20-second QTH exposure (control) in only 10 seconds. The PAC light required similar exposure time as conventional QTH treatment. Second-generation blue LED units reached conversion similar to control in only 10 seconds, while one light required only 5 seconds' exposure.

Bisphenol A-Glycidyl Methacrylate↗