Biomedical subjects

Aslihan Usumez

Publications and source records attributed to Aslihan Usumez.

18 recordsLinked to original sources

PubMed2006

Bond strength between root dentin and three glass-fiber post systems.

STATEMENT OF PROBLEM: Glass-fiber posts were introduced for use after endodontic therapy instead of metal alloy and ceramic posts. There are several new types of glass-fiber post systems available, but little is known about how well these posts bond to the root surface. PURPOSE: The purpose of this in vitro study was to compare the bond strengths of 3 different types of glass-fiber post systems-opaque, translucent, and electrical glass-in 3 different locations of prepared post spaces. MATERIAL AND METHODS: Sixty human intact single-rooted extracted teeth were used. The root canals were prepared using a step-back technique and obturated with gutta-percha using lateral condensation. The roots were divided into 3 experimental groups and further divided into 2 subgroups according to testing time (n=10). Roots were restored with 1 of the following post systems according to the manufacturer's instructions: opaque glass-fiber posts (Snowpost), translucent glass-fiber posts (FiberMaster), and electrical glass-fiber posts (Everstick). A self-etching primer (Clearfil Liner Bond) was applied to the walls of the post spaces, allowed to etch for 30 seconds, and gently air dried. A dual-polymerized bonding agent (Clearfil Liner Bond, Bond A and B) was then applied to the same walls. A dual-polymerizing resin luting agent (Panavia F) was mixed for 20 seconds and then placed in the post spaces using a lentulo spiral instrument. The roots were placed in light-protected cylinders; then the light source was placed directly on the flat cervical tooth surfaces and the cement was polymerized. Specimens were stored in light-proof boxes for 24 hours or 1 week after the polymerization procedure. Each root was cut horizontally, and six 1-mm-thick root segments (2 apical, 2 middle, and 2 cervical) were prepared. Using a push-out test, the bond strength between post and dentin was measured after 24 hours or 1 week using a universal testing machine. Statistical analysis was performed with 3-way ANOVA followed by independent t tests (alpha=.05) to detect differences between groups defined by the specific interacting variables. The different combinations of posts and luting material from the cervical segments were analyzed with SEM. RESULTS: The 3-way ANOVA indicated that push-out test values varied significantly according to the post system used (opaque, electrical, and translucent) (P<.01); the root segments (cervical, middle, and apical) (P<.01), however, did not vary statistically according to the time of testing (24 hours and 1 week). Opaque and electrical glass-fiber posts showed higher bond strength values than translucent posts (P<.01). Push-out bond strength values of cervical segments were significantly higher than the middle and apical segments in translucent and electrical glass-fiber post groups (P<.01). In the opaque glass-fiber post group, there were no significant differences between cervical and middle segments. In SEM analysis, a distinct hybrid zone with long, numerous resin tags located between luting material and dentin was exhibited in all post systems. CONCLUSION: The opaque and electrical glass-fiber posts exhibited similar bond strengths, and translucent posts exhibited the lowest bond strength. The highest bond strength was observed in the cervical third of the post spaces for translucent and electrical glass-fiber post groups.

Dental Bonding↗

PubMed2006

Replacement of missing posterior teeth with an all-ceramic inlay-retained fixed partial denture: a case report.

Adhesively luted all-ceramic inlay-retained fixed partial dentures can be a clinical alternative for the replacement of missing posterior teeth in certain situations. This type of restoration allows satisfactory esthetics and reduced tooth preparation compared to a conventional metal-ceramic fixed restoration. This case report describes the use of an inlay-retained fixed partial denture as a conservative alternative for the replacement of missing posterior teeth.

Adult↗

PubMed2005

Pulpal temperature rise during light-activated bleaching.

The purpose of this study was to measure intrapulpal temperature rise induced by two kinds of bleaching gels when the tooth was exposed to a variety of light-curing units and a diode laser in vitro. The root portions of 80 extracted intact human maxillary central incisors were sectioned with a carborundum disk approximately 2 mm below the cementoenamel junction perpendicular to the long axis of the teeth. Two bleaching agents containing heat-enhancing colorant was applied to the labial surface. Light-curing units used were a conventional halogen (40 s), a high-intensity halogen (30 s), a light-emitting diode unit (40 s), and a diode laser (15 s). The temperature rise was measured in the pulpal chamber with a J-type thermocouple wire that was connected to a data logger. Ten specimens were used for each system and bleaching-agent combination. Differences between the starting temperature and highest temperature reading were taken and the calculated temperature changes were averaged to determine the mean value in temperature rise. Temperature rise values were compared using two-way analysis of variance (ANOVA) at a preset alpha of 0.05. Temperature rise varied significantly depending on curing unit and diode laser used. The diode laser induced significantly higher temperature increases than any other curing unit (11.7 degrees C). The light-emitting diode unit produced the lowest temperature changes (6.0 degrees C); however, there were no statistically significant differences among the curing units and there were no statistically significant differences between bleaching agents. Light activation of bleaching materials with diode laser caused higher temperature changes as compared to other curing units and the temperature rise detected was viewed as critical for pulpal health.

Dental Pulp↗

PubMed2005

The influence of various occlusal materials on stresses transferred to implant-supported prostheses and supporting bone: a three-dimensional finite-element study.

The aim of this numerical analysis was to evaluate the amount and localization of stress that occurs with various materials used in implant-crown design under functional forces. Computer-aided design techniques and a finite-element stress analysis method were used for evaluation. A 4.1 x 10-mm implant placed in the mandibular second premolar area was simulated and analyzed. Simulation and analysis were performed with the use of COSMOS/M software and Pro/Engineer 2000i on a Dual Pentium III 1-GHz computer. Crown designs were as follows: porcelain fused to noble metal crown, porcelain fused to base metal crown, In-Ceram porcelain crown, and IPS Empress 2 porcelain crown. A 300-N vertical force was applied to the centric relation stop points of the crowns. The results of this study indicated that different types of restorative materials play an important role in the amount and distribution of the stresses in the superstructure and the implant. The highest stress values were observed in the IPS Empress 2 porcelain crown design (600 MPa). Porcelain fused to base metal and In-Ceram framework designs transferred less stress to abutment. Type of restorative materials used in implant crown designs are significant factors in the amount and distribution of the stresses on superstructure and implant under functional forces. Porcelain fused to base metal (149 MPa) and In-Ceram (173 MPa) crown designs induced higher von Mises stress values within the framework than porcelain fused to noble metal (108 MPa) and IPS Empress 2 (119 MPa) porcelain crown designs.

Biocompatible Materials↗

PubMed2005

Three-dimensional finite-element analysis of functional stresses in different bone locations produced by implants placed in the maxillary posterior region of the sinus floor.

STATEMENT OF PROBLEM: Implants placed in the posterior maxilla have lower success rates compared to implants placed in other oral regions. Inadequate bone levels have been suggested as a reason for this differential success rate. PURPOSE: The purpose of this study was to determine the amount and localization of functional stresses in implants and adjacent bone locations when the implants were placed in the posterior maxilla in proximity to the sinus using finite element analysis (FEA). MATERIAL AND METHODS: A 3-dimensional finite element model of a maxillary posterior section of bone (Type 3) was used in this study. Different bony dimensions were generated to perform nonlinear calculations. A single-piece 4.1x10-mm screw-shaped dental implant system (ITI solid implant) was modeled and inserted into atrophic maxillary models with crestal bone heights of 4, 5, 7, 10, or 13 mm. In some models the implant penetrated the sinus floor. Cobalt-Chromium (Wiron 99) was used as the crown framework material placed onto the implant, and porcelain was used for occlusal surface of the crown. A total average occlusal force (vertical load) of 300 N was applied at the palatal cusp (150 N) and mesial fossa (150 N) of the crown. The implant and superstructure were simulated in finite element software (Pro/Engineer 2000i program). RESULTS: For the porcelain superstructure for bone levels, maximum von Mises stress values were observed on the mesial fossae and palatal cusp. For the bone structure, the maximum von Mises stress values were observed in the palatal cortical bone adjacent to the implant neck. There was no stress within the spongy bone. High stresses occurred within the implants for all bone levels. CONCLUSION: The maximum von Mises stresses in the implants were localized in the neck of implants for 4- and 5-mm bone levels, but for 7-, 10-, and 13-mm bone levels more even stresses occurred within the implants.

Bite Force↗

PubMed2005

Thermal changes in the pulp chamber during different adhesive clean-up procedures.

The aim of this in vitro study was to measure the temperature changes in the pulpal chamber when different adhesive clean-up procedures were used. Ninety intact extracted human maxillary central incisors were used in the study. The teeth were divided into six groups of 15 teeth each. The removal of the remaining composite on the tooth surface was performed with a tungsten carbide bur. The residual adhesive was removed using a high-speed handpiece with and without water cooling and a contra-angle handpiece with and without water cooling at high and low speeds. A J-type thermocouple wire was positioned in the center of the pulp chamber. The results were analyzed with analysis of variance (ANOVA) and the Tukey-honestly significant difference test. Two-factor ANOVA revealed significant interaction between the handpiece type and water cooling. In this study, the high-speed contra-angle handpiece without water cooling group had the highest deltaT values (7.58 degrees C+/-1.84 degrees C) among all the clean-up procedures. The decrease in pulpal temperature with water cooling was -5.34 degrees C for the handpiece, -5.36 degrees C for the low-speed contra-angle handpiece and -4.98 degrees C for the high-speed contra-angle handpiece. Clinicians should be aware of the potential thermal damage to the pulp, which may result from long clean-up procedures without water cooling. Adhesive removal procedures should be performed with adequate water cooling to prevent temperature increases that might be harmful to pulpal tissues.

Analysis of Variance↗

PubMed2004

Bond strength of a silicone lining material to alumina-abraded and lased denture resin.

The aim of this study was to investigate the bond strength and adhesion of commercially available polydimethylsiloxane denture liner (Molloplast-B) to alumina-abraded or lased heat-cured polymethyl methacrylate denture base resin. The effect of laser irradiation on denture base resin by a surface analyzer and scanning-electron microscopy (SEM) was also determined. Laser-treated specimens demonstrated statistically significantly higher surface roughness values compared to alumina-abraded and untreated (control-group) specimens (p < 0.05). There were no statistically significant differences in surface roughness between alumina-abraded and control specimens. In the tensile debonding test, no statistically significant differences were found among the treatment modalities tested (alumina abraded, lased, and control) (p > 0.05). Molloplast-B applied to alumina-abraded polymethyl methacrylate resin surface recorded the highest mean tensile bond strength. Laser-treated specimens produced the next highest mean tensile bond strength, and untreated polymethyl methacrylate resin surface recorded the lowest tensile bond strength. Laser irradiation produced significant surface texture changes of the denture base material. However, this mechanical surface preparation of denture base before application of a resilient liner did not improve the adhesion between denture base and soft lining material.

Aluminum Oxide↗

PubMed2004

The influence of occlusal loading location on stresses transferred to implant-supported prostheses and supporting bone: A three-dimensional finite element study.

STATEMENT OF PROBLEM: Information about the influence of occlusal loading by location on the stress distribution in an implant-supported fixed partial denture and supporting bone tissue is limited. PURPOSE: The purpose of this study was to investigate the effect of loading at 1 to 3 different locations on the occlusal surface of a tooth on the stress distributions in an implant-supported mandibular fixed partial denture (FPD) and surrounding bone, using 3-dimensional finite element analysis. MATERIAL AND METHODS: A 3-dimensional finite element model of a mandibular section of bone (Type 2) with missing second premolar and its superstructures were used in this study. A 1-piece 4.1 x 10-mm screw-shape ITI dental implant system (solid implant) was modeled for this study. Cobalt-Chromium (Wiron 99) was used as the crown framework material and porcelain was used for occlusal surface. The implant and its superstructure were simulated in a Pro/Engineer 2000i program. Total loads at 300 N were applied at the following locations: 1) tip of buccal cusp (300 N); 2) tip of buccal cusp (150 N) and distal fossa (150 N); or 3) tip of buccal cusp (100 N), distal fossa (100 N), and mesial fossa (100 N). RESULTS: The results demonstrated that vertical loading at 1 location resulted in high stress values within the bone and implant. Close stress levels were observed within the bone for loading at 2 locations and 3 locations; the former created the most extreme stresses and the latter the most even stresses within the bone. With loading at 2 or 3 locations, stresses were concentrated on the framework and occlusal surface of the FPD, and low stresses were distributed to the bone. CONCLUSION: For the loading conditions investigated, the optimal combination of vertical loading was found to be loading at 2 or 3 locations which decreased the stresses within the bone. In this situation, von Mises stresses were concentrated on the framework and occlusal surface of the FPD.

Aluminum Silicates↗

PubMed2004

The efficiency of different light sources to polymerize composite beneath a simulated ceramic restoration.

STATEMENT OF PROBLEM: Inadequate polymerization diminishes the physical properties of composite and compromises material strength. Newly developed light-polymerizing units (plasma arc and high intensity halogen) operate at relatively high intensity and are purported to provide optimum properties to composites in a shorter time. PURPOSE: The aim of this in vitro study was to examine the polymerization efficacy of 3 different polymerization units through a simulated ceramic restoration by determining degree of monomer conversion of a composite luting Material. MATERIAL AND METHODS: A conventional halogen light, a plasma arc light, and a high-intensity halogen light were used to polymerize a composite (Variolink II) with or without catalyst. A pressable ceramic block (5 mm in diameter, 2 mm in height) was used as an interface between the polymerizing light tip and composite. The composite/veneer combination was exposed to 2 different polymerization time protocols for each polymerization unit: (1) 20 or 40 seconds for conventional halogen light, (2) 3 or 6 seconds for plasma arc light, and (3) 10 or 20 seconds (under ramp mode) for the high-intensity halogen light. Using different light units, 120 composite specimens were evaluated (n = 5). Fourier transformation infrared spectroscopy was used to determine the level of light polymerization of the resin through the ceramic material with each of the light sources immediately after polymerization or after 24 hours. Degree of conversion was calculated as a percentage of experimentally polymerized versus maximally polymerized composite. The data were analyzed by 4-factor analysis of variance (alpha = .05). Independent t tests (alpha = .05) were used to detect differences between groups defined by the specific interacting variables. RESULTS: Degree of conversion values varied with the light source (P < .05), polymerization type (P < .05), testing time (P < .01), and exposure to each light source (P < .01). Significant interactions were present between light source and polymerization type (P = .00), light source and testing time (P = .007), and polymerization type and testing time (P = .004). The degree of conversion values were significantly higher in dual-polymerized specimens after 24 hours (P < .01), but there were no significant differences in light-polymerized specimens after 24 hours. The degree of conversion values achieved were significantly lower (P < .05) when specimens were dual polymerized by conventional halogen light and measured immediately (31.59 +/- 7.76). The degree of conversion values achieved were significantly (P < .05) higher with dual polymerization by high-intensity halogen measured after 24 hours (65.06 +/- 8.14). There were no other significant differences among groups. CONCLUSION: The highest degree of conversion values of composite were achieved with polymerization by high-intensity halogen. The plasma arc light achieved similar polymerization of composite through ceramic material in a markedly shorter period than conventional halogen light.

Analysis of Variance↗

PubMed2004

Microleakage of endodontically treated teeth with different dowel systems.

STATEMENT OF PROBLEM: Several new esthetic dowel systems are available for the restoration of endodontically treated teeth, but little is known about how effectively these dowels seal the restored teeth. PURPOSE: The purpose of this in vitro study was to compare microleakage of 3 esthetic, adhesively luted dowel systems with a conventional dowel system. MATERIAL AND METHODS: The root canals of 41 human intact single-rooted extracted teeth were prepared using a step-back technique. The teeth were randomly divided into 4 experimental groups (n=10), and 1 tooth served as a positive control. The decoronated roots were obturated with gutta-percha using lateral condensation. Roots were restored with 1 of the following dowel systems according to the manufacturer's instructions: (1) stainless steel dowels (ParaPost), (2) glass fiber dowels (Snowpost), (3) resin-supported polyethylene fiber (Ribbond) dowels, or (4) zirconia dowels (Cosmopost). Using a fluid filtration method, coronal leakage of the specimens along the dowel space and root canal restorative material was measured. Fluid movement measurements were made at 2-minute intervals for 8 minutes to measure the presence of voids existing in the obturated canals, at 1 week, 3 months, and 6 months following dowel insertion. A repeated-measures analysis of variance (ANOVA) was used to analyze logarithmic transformations of data (time and dowel material) for significant differences. The Tukey HSD test and paired 2-tailed tests were used to perform multiple comparisons (alpha=.05). RESULTS: The data indicated that the leakage values varied according to the dowel system used (P<.01). There was significant interaction between dowel systems and time of testing (P<.01). The sealing ability of zirconia dowels decreased over time (P<.01), but sealing abilities of stainless steel and resin-supported polyethylene fiber dowels remained constant (P>.05). The sealing ability of glass fiber dowels increased at 3 months (P=.032) and remained constant over the next 3 months (P=.758). Statistically, resin-supported polyethylene fiber and glass fiber dowels showed the lowest coronal leakage when compared with stainless steel and zirconia dowels at all time periods (P<.01). There were no significant differences between resin-supported polyethylene fiber and glass fiber dowels at any time period. The initial leakage measurement in zirconia dowel and stainless steel dowels were similar (P=.914), but became significantly different at 3 and 6 months (P<.01). CONCLUSION: Resin-supported polyethylene fiber dowels and glass fiber dowels tested exhibited less microleakage compared to zirconia dowel systems. The latter system should be further evaluated because of its unacceptable level of leakage.

Acrylic Resins↗

PubMed2003

Restoring function and esthetics in a patient with amelogenesis imperfecta: a clinical report.

This clinical report describes the prosthodontic treatment for an 18-year-old man diagnosed with amelogenesis imperfecta. The aim of treatment was to reduce dental sensitivity and to restore esthetics and masticatory function. Metal-ceramic fixed partial dentures were placed on posterior teeth to modify the occlusion, and porcelain laminate veneers were placed to improve the esthetics of the maxillary anterior teeth. Clinical examination 12 months after treatment revealed no evidence of disorders associated with the restored teeth or their supporting structures.

Adolescent↗

PubMed2003

Bond strengths of porcelain laminate veneers to tooth surfaces prepared with acid and Er,Cr:YSGG laser etching.

STATEMENT OF PROBLEM: The erbium, chromium: yttrium, scandium, gallium, garnet (Er,Cr:YSGG) hydrokinetic laser system has been successful in the ablation of dental tissues. It has been reported that this system is also useful for preparing tooth surfaces for adhesion, but results to date have been controversial. PURPOSE: This in vitro study evaluated the bond strengths of porcelain laminate veneers to tooth surfaces after etching with acid and Er,Cr:YSGG laser conditioning. Material and method Forty extracted caries- and restoration-free human maxillary central incisors were used. The teeth were sectioned 2 mm below the cementoenamel junction. The crowns were embedded in autopolymerizing acrylic resin with the labial surfaces facing up. The labial surfaces were prepared with.05 mm reduction to receive porcelain veneers. The teeth were divided into 4 groups of 10 specimens. Thirty specimens received 1 of the following surface treatments before the bonding of IPS Empress 2 laminate veneers: (1) laser radiation from an Er,Cr:YSGG laser unit; (2) 37% orthophosphoric acid; and (3) 10% maleic acid. Ten specimens received no surface treatment and served as the control group. The veneers were bonded with dual-polymerizing resin, Variolink II. One microtensile specimen from each of the cervical and incisal thirds measuring 1.2 x 1.2 mm was prepared with a slow-speed diamond saw sectioning machine with a diamond-rim blade. These specimens were attached to opposing arms of the microtensile testing device with cyanoacrylate adhesive and fractured under tension at a crosshead speed of 1 mm/min, and the maximum load at fracture (Kg) was recorded. The data were analyzed with a 2-way analysis of variance and Tukey HSD tests (alpha=.05). RESULTS: No statistically significant differences were found among the bond strengths of veneers bonded to tooth surfaces etched with Er,Cr:YSGG laser (12.1 +/- 4.4 MPa), 37% orthophosphoric acid (13 +/- 6.5 MPa), and 10% maleic acid (10.6 +/- 5.6 MPa). The control group demonstrated the lowest bond strength values in all test groups. Statistically significant differences were found between the bond strengths of cervical and incisal sections (P<.001). CONCLUSION: In vitro microtensile bond strengths of porcelain laminate veneers bonded to tooth surfaces that were laser-etched showed results similar to orthophosphoric acid or maleic acid etched tooth surfaces.

Acid Etching, Dental↗

PubMed2003

Effect of complete dentures on dynamic measurement of changing head position: A pilot study.

STATEMENT OF PROBLEM: Complete dentures contribute significantly to the facial esthetics of edentulous patients. However, information as to the effect of complete dentures on the natural position of the head is limited. PURPOSE: The purpose of this pilot study was to evaluate the immediate and 30-day effect of wearing complete dentures on the dynamic natural head position measured during walking. MATERIALS AND METHODS: The sample consisted of a volunteer group of 16 patients, 8 women and 8 men, who received new complete dentures. The ages of the subjects ranged from 45 to 64 years (mean=52 years). Dynamic measurement of head posture was carried out by a specially constructed inclinometer device. Each subject in turn was fitted with the inclinometer system and instructed to walk in a relaxed manner for 5 minutes. The data, measured as degrees, were stored in a pocket data logger. This procedure was repeated before insertion of dentures (T1), immediately after insertion of dentures (T2), and 30 days after insertion of dentures (T3). Stored dynamic head posture data were transferred to computer for analysis. The means of the measurements were statistically compared with Friedman and following Wilcoxon tests (alpha =.05). RESULTS: Twelve of 16 (75%) subjects showed an average of 4.6 degrees of cranial extension immediately after insertion of dentures. Six (37.5%) subjects showed an average of 6.4 degrees of cranial flexion, and 8 (50%) subjects showed an average of 5.2 degrees of cranial extension at T3 relative to the T1 measurement. Dynamic head posture measurements of the other 2 subjects remained unchanged. There were significant differences between different measurements of dynamic head posture positions (P<.025). However, only the T1 and T2 measurements were significantly different (P<.015). CONCLUSION: The findings indicate that the statistically significant average extension 4.6 degrees in subjects immediately after insertion of complete dentures was not stable after a 30-day evaluation period and did not produce any statistically significant change. The overall effect of wearing dentures was an irregular flexion or extension pattern on dynamic head posture.

Dental Occlusion, Balanced↗

PubMedDate not supplied

Temperature increase during resin cement polymerization under a ceramic restoration: effect of type of curing unit.

PURPOSE: This study measured the temperature increase induced by various types of curing units during resin cement polymerization under ceramic restorations. MATERIALS AND METHODS: The resin cement was polymerized between a ceramic specimen (diameter 5 mm, height 2 mm) and a dentin disk (diameter 5 mm, height 1 mm) with a conventional halogen light, a high-intensity halogen light, a plasma-arc light, and a light-emitting diode unit. The temperature increase was measured under the dentin disk with a J-type thermocouple wire connected to a data logger. Ten measurements were carried out for each curing unit. Difference between starting and highest temperature readings was measured, and the 10 calculated temperature changes were averaged. RESULTS: Temperature increase varied significantly depending on curing unit used. The plasma-arc light induced significantly higher temperature increases than any other curing unit. The light-emitting diode unit produced the lowest temperature changes. There were no statistically significant differences between the conventional and high-intensity halogen curing units. CONCLUSION: Polymerization with curing units characterized by high energy output (plasma-arc light) caused higher temperature changes compared to other curing units, but the temperature increase detected was not viewed as critical for pulpal health.

Analysis of Variance↗

PubMedDate not supplied

Temperature rise during adhesive and resin composite polymerization with various light curing sources.

This study evaluated the temperature rise in two different adhesive (Clearfil SE Bond [CSEB] and EBS-Multi [EBSM]) and composite systems (Clearfil AP-X [CAPX,] Pertac II [PII]) by the same manufacturer when illuminated by four different light sources: Light-emitting diode (LED), Plasma arc curing (PAC), high intensity quartz tungsten halogen (HQTH) and quartz tungsten halogen (QTH). Forty dentin disks were prepared from extracted premolars. These dentin disks were placed in apparatus developed to measure temperature rise. Temperature rise during photopolymerization of adhesive resin and resin composite was then measured. The mean values of temperature increases for adhesive and resin composites did not differ significantly (p=0.769). The highest temperature rise was observed during photopolymerization of EBSM with PAC (5.16 degrees C) and HQTH (4.28 degrees C), respectively. Temperature rise values produced by QTH (1.27 degrees C - 2.83 degrees C for adhesive resin; 1.86 degrees C - 2.85 degrees C for resin composite) for both adhesive and resin composites were significantly lower than those induced by PAC and HQTH (p<0.05). However, these values were significantly higher than those produced by LED (1.16 degrees C - 2.08 degrees C for adhesive resin; 1.13 degrees C - 2.59 degrees C for resin composite). Light sources with high energy output (PAC and HQTH) caused significantly higher temperature rise than sources with low energy output (QTH and LED). However, in this study, no temperature rises beneath 1-mm dentin disk exceed the critical 5.6 degrees C value for pulpal health.

Analysis of Variance↗

PubMedDate not supplied

Degree of conversion and surface hardness of resin cement cured with different curing units.

OBJECTIVE: The aim of this study was to evaluate the degree of conversion and Vickers surface hardness of resin cement under a simulated ceramic restoration with 3 different curing units: a conventional halogen unit, a high-intensity halogen unit, and a light-emitting diode system. METHODS AND MATERIALS: A conventional halogen curing unit (Hilux 550) (40 s), a high-intensity halogen curing unit used in conventional and ramp mode (Optilux 501) (10 s and 20 s, respectively), and a light-emitting diode system (Elipar FreeLight) (20 s, 40 s) were used in this study. The dual-curing resin cement (Variolink II) was cured under a simulated ceramic restoration (diameter 5 mm, height 2 mm), and the degree of conversion and Vickers surface hardness were measured. For degree of conversion measurement, 10 specimens were prepared for each group. The absorbance peaks were recorded using the diffuse-reflection mode of Fourier transformation infrared spectroscopy. For Vickers surface hardness measurement, 10 specimens were prepared for each group. A load of 200 N was applied for 15 seconds, and 3 evaluations of each of the samples were performed. RESULTS: Degree of conversion achieved with Optilux 501 (20 s) was significantly higher than those of Hilux, Optilux 501 (10 s), Elipar FreeLight (20 s), and Elipar FreeLight (40 s). For Vickers surface hardness measurement, Optilux 501 (20 s) produced the highest surface hardness value. No significant differences were found among the Hilux, Optilux 501 (10 s), Elipar FreeLight (20 s), and Elipar FreeLight (40 s). CONCLUSION: The high-intensity halogen curing unit used in ramp mode (20 s) produced harder resin cement surfaces than did the conventional halogen curing unit, high-intensity halogen curing unit used in conventional mode (10 s) and light-emitting diode system (20 s, 40 s), when cured through a simulated ceramic restoration.

Dental Porcelain↗

PubMedDate not supplied

Two-year color changes of light-cured composites: influence of different light-curing units.

This study determined color changes in a composite cured with various types of curing units after two years. A hybrid (Clearfil AP-X) composite was cured with a conventional halogen, a high intensity halogen, a plasma arc and a light emitting diode unit. The specimens were stored in light-proof boxes after the curing procedure to avoid further exposure to light and stored in 37 degrees C in 100% humidity. Colorimetric values of the specimens immediately after curing and after two years were measured using a colorimeter. The CIE 1976 L*a*b color system was used to determine color differences. Differences from baseline were calculated as deltaE*ab. Data were analyzed with two-way analysis of variance (p<0.05). The deltaE*ab values varied significantly, depending on the curing unit used. The specimens cured with a plasma arc curing unit induced significantly higher color changes than any other specimen and the color differences were also visually appreciable by the non-skilled operator (deltaE*ab >2.5). The specimens cured with a high intensity halogen curing unit produced the lowest color change; however, there were no statistically significant differences among the color changes of specimens cured with conventional halogen, high intensity halogen and the light emitting diode unit, and the color changes were not clinically relevant (deltaE*ab <2.5). The results of this study suggest that composite materials undergo measurable changes due to curing unit exposure. The specimens cured with a plasma arc light showed the highest color changes as compared to specimens cured with other curing units.

Analysis of Variance↗

PubMedDate not supplied

In vivo heat transfer capacities of autopolymerizing, heat-polymerizing, and injection-molded acrylic resins.

The aim of this pilot study was to measure the heat transfer capacities of heat-polymerizing, injection-molded, and autopolymerizing acrylic resins in vivo. Two volunteers used acrylic resin removable plates and consumed hot (69 degrees C) and cold drinks (6 degrees C). Differences between oral temperature and highest and lowest temperature readings were recorded. Temperature changes for the autopolymerizing acrylic resin were found to be significantly higher than the heat-polymerizing and injection-molded acrylic resins for both cold and hot drinks. Despite the disadvantages of autopolymerizing acrylic resins, their high heat transfer capacity may be an advantage.

Acrylic Resins↗