Effect of substrate adjacent to the scan region on the trueness of four intraoral scanners: An in vitro study.

OBJECTIVES: The purpose of this in vitro study was to evaluate the trueness of four commercially available intraoral scanners (IOSs) on scanning different substrates that existed in the adjacent proximal contact area. METHODS: Four IOSs (TRIOS 4, TRIOS 3, Primescan, Omnicam) were used for scanning the intact enamel surface of a molar tooth, and six restorative materials (zirconia, lithium disilicate glass-ceramic, composite resin, hybrid ceramic, feldspathic ceramic, metal) that were located at the adjacent proximal contact area of the same tooth. Reference scans were obtained using an extraoral scanner (inEos X5). A 3-dimensional analyzing software (Geomagic Control X) was used to compare the reference and tested scans. The two-way analysis of variance (ANOVA) followed by Bonferroni correction was performed for statistical analyses (α=0.05). RESULTS: TRIOS 3 and TRIOS 4 showed higher trueness than Primescan, and Primescan showed higher trueness than Omnicam (p<0.001), while there were no differences between TRIOS 3 and TRIOS 4. Metal showed significantly higher Root Mean Square values (0.273 ± 0.24 mm) than other substrates. No difference was found between the scanners' zirconia, lithium disilicate glass-ceramic, composite, and feldspathic ceramic scans (p > 0.05). For the metal, TRIOS 3 and TRIOS 4 showed higher trueness than Primescan and Omnicam, while Omnicam showed lower trueness among all scanners. For the hybrid ceramic, TRIOS 3 showed higher trueness than Omnicam (p<0.001). For the enamel, TRIOS 3 showed higher trueness than Primescan and Omnicam (p<0.001). CONCLUSIONS: The trueness of IOSs can be affected by the substrates that exist in the proximal contact area. Amongst all, the metal substrate affected most the trueness of the IOSs. CLINICAL SIGNIFICANCE: The clinician should decide on the impression system, taking into account that the IOS and the surfaces to be scanned affect the trueness of the digital data. The deviation of the digital impression would be high in the presence of a metal restoration on the adjacent proximal surface.

The trueness of an intraoral scanner in scanning different post space depths.

OBJECTIVES: The purpose of this in vitro study was to evaluate the trueness of scanning the post space up to 20 mm with an intraoral scanner (IOS). METHODS: We captured 20-, 18-, 16-, 14-, 12-, and 10-mm length post space scans using an IOS (Primescan) eight times each by shortening the apical 2 mm end of the same mandibular canine tooth. The reference impressions of each length group were taken using a light-body polyvinyl siloxane impression material and were scanned with an extraoral scanner. The recorded standard tessellation language (STL) data of all impressions were uploaded to a 3D matching program for the trueness evaluation via the root mean square (RMS) calculation. For the statistical analysis, the Kruskal-Wallis and post-hoc Mann-Whitney U nonparametric tests were performed to compare the differences among the groups (α=0.05). RESULTS: The median RMS values increased in direct proportion to the length of the post space from 10 mm (357.1 µm) to 20 mm (897.5 µm). We noted a significant difference among groups (p< 0.001). In the pairwise comparisons, there were no significant differences between the 14 mm and 16 mm groups (p=0.431) or between the 18 mm and 20 mm groups (p=0.036), while other paired groups showed significant differences (p=0.001). CONCLUSIONS: The scanned space depth affected the trueness of the IOS (Primescan). If the post depth was below 14 mm, and the minimum diameter was 2.2 mm, Primescan could be used for impressions of the post-core structure, simplifying the impression procedure. CLINICAL SIGNIFICANCE: IOS seems to be a promising technology for taking digital impressions of post spaces, but cannot be recommended as a routine procedure at its present stage, as final results are highly dependent on the clinical situation. Further studies with different IOS systems are needed to gain sound evidence.

Influence of cement shade, ceramic thickness, and airborne-particle abrasion of titanium surface on the final color of monolithic lithium disilicate glass-ceramic hybrid-abutment systems in vitro.

OBJECTIVES: The purpose of this in vitro study was to evaluate the influence of the ceramic thickness, cement shade, and airborne-particle abrasion of the titanium on the final color of titanium base cemented lithium disilicate glass-ceramic restorations. METHOD AND MATERIALS: In total, 144 lithium disilicate glass-ceramic disks of three thicknesses (0.5, 1.0, and 1.5 mm) were cemented to airborne-particle-abraded and non-airborne-particle-abraded titanium disks with six adhesive resin cements. The color measurements were performed with a clinical spectrophotometer. The mean and standard deviation of evaluated ΔE values were calculated. A three-way analysis of variance (ANOVA) was used for analyzing the data. Statistical analyses were computed with a significance level of α = .05 using a statistical software program (Minitab 17, Minitab). RESULTS: The 0.5- and 1-mm-thick ceramic specimens cemented with Panavia V5 Opaque showed the lowest ΔE values when cemented on both non-airborne-particle-abraded (5.62 ± 1.66, 3.15 ± 1.28) and airborne-particle-abraded (5.55 ± 0.86, 3.16 ± 0.49) surfaces, while the highest values were seen in the groups cemented with RelyX U200 A2 (29.22 ± 0.83, 17.23 ± 0.45) and Panavia V5 A2 (29.94 ± 1.17, 16.71 ± 0.44) on airborne-particle-abraded surfaces. For the 1.5-mm-thick ceramics, the lowest ΔE values were seen when Multilink MO 0 cement was used on non-airborne-particle-abraded surfaces (1.56 ± 0.29) and when Panavia V5 Opaque was used on airborne-particle-abraded surfaces (1.56 ± 0.66). The highest values were seen when RelyX U200 A2 (9.77 ± 1.13), PA2 (9.24 ± 0.25), and Multilink HO 0 (9.19 ± 1.33) were used on airborne-particle-abraded surfaces, and when Multilink HO 0 (9.61 ± 1.70) was used on non-airborne-particle-abraded surfaces. The 1-mm-thick ceramics cemented with Multilink HO 0 showed higher ΔE values (12.05 ± 1.99) for airborne-particle-abraded and non-airborne-particle-abraded (12.58 ± 1.06) than thinner (0.5 mm) or thicker (1.5 mm) ceramics. CONCLUSION: Thinnest ceramic superstructures resulted in the highest ΔE values. Cements that mask the underlying color reflect their own shade under thin superstructures. Airborne-particle abrasion of titanium surfaces increases the grayish reflectance if cement shade does not have the color masking ability.

Comparison of Reliability of 3 Resonance Frequency Analysis Devices: An In Vitro Study.

The purpose of the present study was to investigate the intraobserver and interobserver reliability of 3 resonance frequency analysis (RFA) devices and to compare the implant stability quotient (ISQ) values according to implant macro design and diameter in 2 different bone densities. A total of 64 implants (Neoss ProActive; Neoss; Harrogate, UK) of varying diameters (3.5 and 4.0 mm) and implant macro design (tapered and straight) were placed in 2 artificial bone blocks (the density of type 2 and 3). The implant primary stability was measured using Osstell IDx (Osstell; Göteborg, Sweden), Osstell Beacon and Penguin RFA (Integration Diagnostics; Göteborg, Sweden). The ISQ value of each implant was measured by 2 observers and recorded 5 times in 2 directions. The intraobserver and interobserver reliability of RFA devices were evaluated. In addition to that, mean ISQ values were calculated for each RFA device to evaluate the effect of implant diameter, implant macro design, and bone density on ISQ values. ISQ values were significantly higher for implants placed within the type 2 bone than for the type 3 bone. The 4.0-mm diameter implants presented higher ISQ values than 3.5-mm diameter implants. The intraclass correlation coefficient (ICC) values for intraobserver reliability were above 0.85 for each observer and the ICC values for interobserver reliability were 0.94, 0.93, and 0.98 for Osstell IDx, Osstell Beacon, and Penguin RFA, respectively. Although there was excellent interobserver reliability with 3 RFA devices, the intraobserver reliability of Osstell Beacon and Penguin RFA were slightly better than Osstell IDx. Bone density and implant diameter were parameters affecting the primary stability of implants.

Accuracy of six intraoral scanners for scanning complete-arch and 4-unit fixed partial dentures: An in vitro study.

STATEMENT OF PROBLEM: The digital scan accuracy of different intraoral scanners (IOSs) for long-span fixed prosthesis and the effect of the starting quadrant on accuracy is unclear. PURPOSE: The purpose of this in vitro study was to evaluate the accuracy of 6 IOSs for complete-arch and prepared teeth digitally isolated from the complete-arch and to determine the effect of the starting quadrant on accuracy. MATERIAL AND METHODS: A maxillary model containing bilaterally prepared canines, first molar teeth, and edentulous spans between the prepared teeth was used. The model was scanned by using a highly accurate industrial scanner to create a digital reference data set. Six IOSs were evaluated: TRIOS, iTero, Planmeca Emerald, Cerec Omnicam, Primescan, and Virtuo Vivo. The model was scanned 10 times with each IOS by 1 operator according to the protocols described by the manufacturers. Five scans were made starting from the right quadrant (ScanR), followed by 5 scans starting from the left quadrant (ScanL). All data sets were obtained in standard tessellation language (STL) file format and were used to evaluate accuracy (trueness and precision) with a 3D analyzing software program (Geomagic Studio 12; 3D Systems) by using a best-fit alignment. The prepared teeth were digitally isolated from the complete-arch and evaluated with the analyzing software program. The Kruskal-Wallis and Mann-Whitney U statistical tests were used to detect differences for trueness and precision (α=.05). RESULTS: Statistically significant differences were found regarding IOSs (P<.003) and scanning sequence (P<.05). The TRIOS showed the best trueness for the complete-arch, but not statistically different from Primescan, Virtuo Vivo, and iTero (P>.003). The lowest median values for precision of the complete-arch were also found using TRIOS, but no significant difference was found among the scanners (P>.003). In terms of trueness and precision, Primescan had the best accuracy for preparations. Emerald showed significant differences depending on the scanning sequence for complete-arch accuracy. ScanR for trueness (P=.021) and ScanL for precision (P=.004) showed improved results. However, Emerald, TRIOS, and Virtuo Vivo showed statistically significant differences in precision of preparations depending on scanning sequence. ScanL deviated less than ScanR when scanned with TRIOS (P=.025) and Emerald (P=.004), and the opposite with Virtuo Vivo (P=.008). In terms of preparations trueness, no significant difference was found between the ScanR and ScanL of any IOS (P>.05). CONCLUSIONS: Based on this in vitro study, the accuracy of the complete-arch and prepared teeth differed according to the IOS and scanning sequence.

Effect of pulp chamber depth on the accuracy of endocrown scans made with different intraoral scanners versus an industrial scanner: An in vitro study.

STATEMENT OF PROBLEM: The accuracy of intraoral scanners (IOSs) has been evaluated. However, testing their performance when scanning deep endocrown preparations is lacking. PURPOSE: The purpose of this in vitro study was to assess the effect of pulpal chamber extension depth (PCED) on scanning accuracy and to compare the accuracy of different IOSs on scanning different PCEDs. MATERIAL AND METHODS: Six different IOSs were compared: TRIOS 3, CEREC Omnicam, CEREC Primescan, Planmeca Emerald, iTero Element2, and Virtuo Vivo. Endocrown preparations were digitally designed with a computer-aided design and computer-aided manufacturing (CAD-CAM) software program (Rhicoceros), and the PCEDs of preparations were 2, 3.5, and 5 mm. Designed preparations were milled from a polymethylmethacrylate block (Telio CAD) with a milling unit. Reference scans were obtained from an industrial scanner (ATOS), and 5 test scans of each cavity were made with 6 IOSs. All scans were converted into standard tessellation language (STL) files. The data sets obtained from the IOSs were superimposed on the reference scan to evaluate trueness and on each other within groups to determine precision by using a 3D analysis software program (Geomagic Control X). Obtained data were analyzed with 1-way ANOVA and Tukey HSD tests (α=.05). RESULTS: CEREC Primescan was found to have the best trueness and precision among the evaluated IOSs (P<.05), while Planmeca Emerald was found to have the lowest trueness (P<.05). For all tested PCEDs, statistically significant differences were found among IOSs. A PCED with a 2-mm depth (18.57 ±4.80 µm) showed significantly better scanning trueness than that with a 5-mm depth (23.81 ±6.53), while no significant differences were found between 2 and 3.5 mm (P>.05). CONCLUSIONS: Deep pulpal chamber extensions of endocrown restorations could negatively affect scanning accuracy, and scanning accuracy varies depending on the selected IOS. CEREC Primescan appears to be the best IOS choice for scanning endocrowns with deep pulpal chamber extensions.

Clinical performance of narrow-diameter titanium-zirconium implants in immediately loaded fixed full-arch prostheses: a 2-year clinical study.

OBJECTIVES: The aim of this study was to evaluate the outcomes of immediate fixed full-arch prostheses supported by axial or tilted narrow-diameter Ti-Zr implants (3.3 mm) (Roxolid®, Institut Straumann® AG, Basel, Switzerland) (NDIs) in combination with standard-diameter implants up to 2 years' follow-up. MATERIALS AND METHODS: The study was conducted at Kocaeli University Faculty of Dentistry from 2016 to 2018. 37 jaws of 28 patients with an average age of 52 years were rehabilitated with fixed full-arch prostheses supported by 179 implants. Cumulative survival rate (CSR), implant success, marginal bone loss (MBL), and prosthetic survival rate as well as complications were analyzed. RESULTS: Total CSR of 99.4% and 98.5% for all and narrow implants respectively have been observed at 2 years' follow-up. No prosthesis failures were observed, yielding a cumulative prosthetic survival rate of 100%. The NDIs achieved 0.63 mm MBL at 1 year and 1.02 mm at 2 years. The mean MBL at 1 year was 0.51 mm (mandible 0.63 mm/maxilla 0.41 mm) and 0.73 mm (mandible 0.90 mm/maxilla 0.43 mm) at 2 years. Both implant angulation and loading protocol did not influence the MBL. CONCLUSIONS: The combination of narrow-diameter implants with standard-diameter implants in immediate fixed full-arch rehabilitation has a good prognosis to become a new standard of care for severely atrophic jaws. CLINICAL RELEVANCE: The use of narrow-diameter implants in fixed full-arch rehabilitations in atrophic ridges would be a successful and predictable treatment approach.

Effect of different composite materials used as core build-ups on the trueness of intraoral scanning.

PURPOSE: To evaluate the trueness of digital impressions of different composite resin materials that can be used for core build-ups in clinical practice. MATERIALS AND METHODS: A maxillary central incisor was prepared and scanned with an intraoral scanner (Primescan, Dentsply Sirona). Ten composite resin specimens (in three groups: universal composite; flowable composite; and bulk fill resin composite) were milled in the same dimensions of the prepared tooth and scanned. The data of the prepared tooth were used as reference, and the data obtained from the composite resin specimens were aligned with the evaluation software (Geomagic Studio 12) to determine deviation values. Kruskal-Wallis with Dunn post hoc test was performed (α = .05). RESULTS: There were significant differences in the trueness of digital impressions between some composite resin groups (P < .05). The mean trueness deviation values were in the range of 12.75 µ m (G-aenial Posterior) to 17.06 µ m (Filtek Bulk Fill Posterior). The trueness of G-aenial Posterior (12.75 µ m) was higher than that of Core-X Flow (14.62 µ m), Clearfil Majesty Flow (16.93 µ m), and Filtek Bulk Fill Posterior (17.06 µ m). Filtek Bulk Fill Posterior exhibited lower trueness than Clearfil Majesty Esthetic (12.93 µ m), Clearfil Majesty Posterior (13.50 µ m), and Charisma Classic (13.81 µ m). CONCLUSION: Different composite resins used for core build-up can impact the trueness of digital impressions, with universal composite resin scans being the truest compared to flowable and bulk fill composite resin scans. All scanned substrate groups can be regarded as within a clinically acceptable range.

Accuracy of Digital Impressions Obtained Using Six Intraoral Scanners in Partially Edentulous Dentitions and the Effect of Scanning Sequence.

PURPOSE: To compare the accuracy of six intraoral scanners in two different partially edentulous maxillary models and to evaluate the effect of scanning sequence on accuracy. MATERIALS AND METHODS: Maxillary Kennedy Class I and Class IV situations were used as reference models. The reference datasets were obtained by scanning the models using a highly accurate industrial scanner (ATOS Core 80, GOM). The following six intraoral scanners were evaluated: Trios 3 (3Shape), iTero Element 2 (Align Technology), Emerald (Planmeca), CEREC Omnicam (Dentsply Sirona), CEREC Primescan (Dentsply Sirona), and Virtuo Vivo (Dental Wings). A total of 120 scans from both models were obtained using the six intraoral scanners and divided into two groups based on scanning sequence. Accuracy was evaluated by deviation analysis using 3D image processing software (Geomagic Studio 12, 3D Systems). Kruskal Wallis and Mann-Whitney U tests were performed (P ≤ .05) for statistical analysis. RESULTS: There were significant differences in the accuracy of digital impressions among intraoral scanners and scanning sequences. The trueness of the Trios scanner and the precision of the Trios, Primescan, and iTero scanners were significantly higher than for the other scanners. The Emerald had the lowest accuracy among the six intraoral scanners tested. Accuracy was affected by scanning sequence when using the Virtuo Vivo, Emerald, Primescan, and iTero. CONCLUSION: In Kennedy Class I and Class IV partially edentulous cases, it is useful to consider that the intraoral scanner used may affect the accuracy of the digital impression.

Comparing the accuracy of six intraoral scanners on prepared teeth and effect of scanning sequence.

PURPOSE: The aim of this study was to evaluate the accuracy of six recently introduced intraoral scanners (IOSs) for single crown preparations isolated from the complete arch, and to determine the effect of scanning sequence on accuracy. MATERIALS AND METHODS: A complete arch with right and left canine preparations for single crowns was used as a study model. The reference dataset was obtained by scanning the complete arch using a highly accurate industrial scanner (ATOS Core 80, GOM GmbH). Six different IOSs (Trios, iTero, Planmeca Emerald, Cerec Omnicam, Primescan, and Virtuo Vivo) were used to scan the model ten times each. The scans performed with each IOS were divided into two groups, based on whether the scanning sequence started from the right or left quadrant (n=5). The accuracy of digital impression was evaluated using three-dimensional analyzing software (Geomagic Studio 12, 3D Systems). The Kruskal Wallis and Mann-Whitney U statistical tests for trueness analysis and the One-way ANOVA test for precision analysis were performed (α=.05). RESULTS: The trueness and precision values were the lowest with the Primescan (25 and 10 µm), followed by Trios (40.5 and 11 µm), Omnicam (41.5 µm and 18 µm), Virtuo Vivo (52 and 37 µm), iTero (70 and 12 µm) and Emerald (73.5 and 60 µm). Regarding trueness, iTero showed more deviation when scanning started from the right (P=.009). CONCLUSION: The accuracy of digital impressions varied depending on the IOS and scanning sequence used. Primescan had the highest accuracy, while Emerald showed the most deviation in accuracy for single crown preparations.

The Effect of Luting Cement and Titanium Base on the Final Color of Zirconium Oxide Core Material.

PURPOSE: To evaluate the effects of different types of luting cements and different colors of zirconium cores on the final color of the restoration that simulates implant-supported fixed partial dentures (FPDs) by using a titanium base on the bottom. MATERIALS AND METHODS: One hundred and twenty zirconium oxide core plates (Zr-Zahn; 10 mm in width, 5 mm in length, 0.5 mm in height) were prepared in different shades (n = 20; noncolored, A2, A3, B1, C2, D2). The specimens were subdivided into two subgroups for the two types of luting cements (n = 10). The initial color measurements were made on zirconium oxide core plates using a spectrometer. To create the cement thicknesses, stretch strips with holes in the middle (5 mm in diameter, 70 µm in height) were used. The second measurement was done on the zirconium oxide core plates after the application of the resin cement (U-200, A2 Shade) or polycarboxylate cement (Lumicon). The final measurement was done after placing the titanium discs (5 mm in diameter, 3 mm in height) in the bottom. The data were analyzed with two-way ANOVA and Tukey's honestly significant differences (HSD) tests (α = 0.05). RESULTS: The ∆E*ab value was higher in the resin cement-applied group than in the polycarboxylate cement-applied group (p < 0.001). The highest ∆E*ab value was recorded for the zirconium oxide core-resin cement-titanium base, and the lowest was recorded for the polycarboxylate cement-zirconium oxide core (p < 0.001). CONCLUSION: The luting cement, the presence of titanium, and the color of zirconium are all important factors that determine the final shade of zirconia cores in implant-supported FPDs.

Efficacy of Low-Level Laser Therapy in the Management of Postoperative Pain in Children After Primary Teeth Extraction: A Randomized Clinical Trial.

OBJECTIVE: This study evaluated the effect of low-level laser therapy (LLLT) on postoperative pain in children undergoing primary molar extraction. MATERIALS AND METHODS: This randomized, controlled-crossover, double-blind clinical trial was conducted with 37 children requiring bilateral extraction of primary molars. In one tooth (LLLT group), a GaAlAs diode laser (wavelength, 810 nm; continuous mode, output power 0.3 W; 180 sec, 4 J/cm(2)) was applied intraorally 1 cm from the target tissue immediately following extraction. In the contralateral tooth (control group), the hand piece was applied, but without laser activation. Children and parents rated postoperative pain on the first three evenings following extraction using, respectively, the Wong-Baker FACES(®) Pain Rating Scale (PRS) and the Visual Analogue Scale (VAS). Parents also reported if their children received analgesics. Data were analyzed using χ(2) and Mann-Whitney U tests. RESULTS: Mean VAS scores were higher for the control group than for the LLLT group on the first and second evenings, and PRS scores were higher for the control group than for the laser group on the first evening, but the differences were not statistically significant (p > 0.05). More analgesics were given to children in the control group on the first evening; however, both groups received equal amounts on the next two evenings (p > 0.05). CONCLUSIONS: Within the limitations of this study, LLLT application following primary molar extraction was not found to affect postoperative pain in children.

The use of low-level laser therapy for controlling the gag reflex in children during intraoral radiography.

The current literature suggests that low-level laser stimulation of the PC 6 acupuncture points may prevent gagging. This study aimed to determine if low-level laser therapy (LLLT) can reduce the gag reflex in children undergoing intraoral maxillary radiography. This randomized, controlled, double-blind clinical trial was conducted with 25 children with moderate-to-very severe gag reflexes who required bilateral periapical radiographic examination of the maxillary molar region. Children's anxiety levels were initially evaluated using Corah's Dental Anxiety Scale (DAS) to identify any possible relationship between gagging and anxiety. A control radiograph was taken of one randomly selected side in each patient after simulated laser application so that the patient was blinded to the experimental conditions (control group). Laser stimulation was then performed for the experimental side. A laser probe was placed on the Pericardium 6 (PC 6) acupuncture point on each wrist, and laser energy was delivered for 14 s (300 mW, energy density 4 J/cm(2)) at a distance of 1 cm from the target tissue. Following laser stimulation, the experimental radiograph was taken (experimental group). Gagging responses were measured using the Gagging Severity Criteria for each group. Data were analyzed using Spearman's rho correlations and Mann-Whitney U tests. Both mean and median gagging scores were higher in the control group than in the experimental group. Patients who were unable to tolerate the intraoral control radiography were able to tolerate the procedure after LLLT. Differences between gagging scores of the control and experimental groups were statistically significant (P = .000). There was no significant correlation between gagging severity and anxiety score (P > .05). A negative correlation was found between age and gagging score in the control group (P ˂ .05). Within the limitations of this study, LLLT of the PC 6 acupuncture points appears to be a useful technique for controlling the gag reflex in children during maxillary radiography.

Diffusion of HEMA from resin cements through different dentin thicknesses in vitro.

PURPOSE: To evaluate the in vitro diffusion of 2-hydroxyethyl methacrylate (HEMA) from the resin cements through different thicknesses of dentin using high-performance liquid chromatography (HPLC) at two time intervals. METHODS: 60 freshly extracted caries- and restoration-free human third molar teeth were used in this study. Standardized box-shaped Class I inlay cavities (6 mm long, 3 mm wide and 2 mm deep) were prepared in all teeth with a high-speed handpiece mounted on a standard cavity machine. The remaining dentin thickness (RDT) between the pulpal wall of the cavity and the roof of the pulp chamber was measured at multiple points for each tooth so that two main groups of 30 teeth each were prepared with an RDT range 0.5-1.9 and 2.0-3.5 mm, respectively. Each of these main groups was divided into three subgroups (n = 10), according to the resin cements tested (RelyX ARC, Panavia F 2.0, Multilink Automix). Lithium disilicate-based ceramic inlays (IPS Empress 2) were manufactured to restore the prepared cavities. A polypropylene chamber containing 1 ml distilled water was attached to the cemento-enamel junction of each tooth. Then, ceramic inlays were cemented with resin cements according to the manufacturers' instructions. Water elutes were analyzed by HPLC at 4.32 minutes and 24 hours. HEMA diffusion amounts were analyzed using three-way ANOVA and Tukey's HSD tests (P < 0.05). RESULTS: HEMA was detected in the pulp chamber elutes of all the teeth. The amounts of released HEMA did not significantly differ between time periods. The diffused HEMA amounts were significantly different between the RDT of 0.5-1.9 and 2.0-3.5 mm (P < 0.05) and between resin cements tested (P < 0.05). Decreasing RDT substantially increased the amount of HEMA that diffused through the dentin to the pulp space.

The effect of transmitted Er:YAG laser energy through a dental ceramic on different types of resin cements.

BACKGROUND AND OBJECTIVE: The laser debonding procedure of adhesively luted all-ceramic restorations is based on the ablation of resin cement due to the transmitted laser energy through the ceramic. The purpose of this study was to determine the effect of Er:YAG laser irradiation transmitted through a dental ceramic on five different resin cements. MATERIALS AND METHODS: Five different resin cements were evaluated in this study: G-Cem LinkAce, Multilink Automix, Variolink II, Panavia F, and Rely X Unicem U100. Disc shaped resin cement specimens (n = 10) were fabricated for each group. A ceramic disc was placed between the resin cement discs and the tip of the handpiece of Er:YAG laser device. The resin cement discs were irradiated through the ceramic and the volume of the resin cement discs were measured using a micro-CT system before and after Er:YAG laser irradiation. The volume loss of the resin cement discs was calculated and analyzed with one-way ANOVA and Tukey-HSD tests. RESULTS: The highest volume loss was determined in G-Cem (1.1 ± 0.6 mm3 ) and Multilink (1.3 ± 0.1 mm3 ) (P < 0.05) groups, and the lowest volume loss was determined in Rely X (0.3 ± 0.07 mm3 ), Variolink (0.4 ± 0.2 mm3 ), and Panavia (0.6 ± 0.2 mm3 ) groups (P < 0.05). All resin cements were affected by the laser irradiation resulting in the volume loss of the cement; however, there are significant differences among different resin cements. CONCLUSIONS: All the resin cements tested in this study were effected by the Er:YAG laser irradiation and there were significant differences among the resin cements with regard to ablation volume. Lasers Surg. Med. 47:602-607, 2015. © 2015 Wiley Periodicals, Inc.

Diffusion of HEMA through human carious and non-carious dentin in vitro.

PURPOSE: The aim of this study was to evaluate the diffusion of 2-Hydroxyethyl methacrylate (HEMA) from resin cement through dentin both affected and unaffected by caries through high-performance liquid chromatography (HPLC) at two time intervals. MATERIALS AND METHODS: Ten freshly extracted restoration-free, caries-free and ten extracted carious human third molar teeth were used in this study. Standardized box-shaped Class I inlay cavities (6 mm long, 3 mm wide, 2 mm deep) were prepared in all teeth with a high-speed handpiece mounted on a standard cavity machine. In teeth affected by caries, after preparation, the remaining carious lesions were removed, with their removal guided by a proprietary caries detector dye. The remaining dentin thickness (RDT) between the pulpal wall of the cavity and the roof of the pulp chamber was measured at multiple points for each tooth so that groups of 10 teeth each were prepared with RDT 1.2 ± 0.5 mm. Lithium disilicate-based ceramic inlays were manufactured to restore the prepared cavities. A polypropylene chamber was attached to the cementoenamel junction of each tooth to contain 1 ml distilled water. Then, ceramic inlays were cemented with chemically polymerized resin cement (Multilink Automix) according to the manufacturer's instructions. Water elutes were analyzed by HPLC at 4.32 minutes and 24 hours. HEMA diffusion amounts were analyzed using two-way ANOVA and Tukey HSD tests (p < 0.05). RESULTS: HEMA was detected in the pulp chamber elutes of all the teeth. The diffused HEMA amounts were not significantly different between the affected caries and the unaffected groups (p= 0.80) or between time periods (p= 0.44). The carious dentin did not influence the amount of HEMA diffused through the dentin to the pulp space. CONCLUSIONS: The highest amount of eluted HEMA concentration detected was not viewed as critical for pulp tissue since the diffused HEMA amounts were below the level of cytotoxicity, according to the literature.

Effect of provisional cements on shear bond strength of porcelain laminate veneers.

OBJECTIVES: The purpose of this study was to evaluate the effect of three provisional cements and two cleaning techniques on the final bond strength of porcelain laminate veneers. METHODS: The occlusal third of the crowns of forty molar teeth were sectioned and embedded in autopolymerizing acrylic resin. Dentin surfaces were polished and specimens were randomly divided into four groups (n=10). Provisional restorations were fabricated and two provisional restorations were cemented onto each tooth. Restorations were fixed with one of three different provisional cements: eugenol-free provisional cement (Cavex), calcium hydroxide (Dycal), and light-cured provisional cement (Tempond Clear). Provisional restorations were removed with either a dental explorer and air-water spray, or a cleaning bur (Opticlean). In the control group, provisional restorations were not used on the surfaces of specimens. IPS Empress 2 ceramic discs were luted with a dual-cured resin cement (Panavia F). Shear bond strength was measured using a universal testing machine. Data were statistically analyzed by ANOVA, Tukey's HSD and Dunnett tests. Surfaces were examined by scanning electronic microscopy. RESULTS: Significant differences were found between the control group and both the light-cured provisional cement groups and the eugenol-free provisional cement-cleaning bur group (P<.05). Groups that had received light-cured provisional cement showed the lowest bond strength values. CONCLUSIONS: Selection of the provisional cement is an important factor in the ultimate bond strength of the final restoration. Calcium hydroxide provisional cement and cleaning with a dental explorer are advisable.

Effect of three types of light-curing units on 5-year colour changes of light-cured composite.

The purpose of this study was to determine colour changes in a composite cured with tungsten-halogen, light-emitting diode (LED) or a plasma arc after 5 years. Five specimens 10 mm in diameter and 2 mm in height were prepared using Hybrid (Clearfil AP-X) composite for each test group. The corresponding specimens were cured with a tungsten-halogen curing light, a LED unit or with a plasma arc. Specimens were stored in light-proof boxes for 5 years 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 5 years were measured using colorimeter. The DeltaE*( ab ) values varied significantly depending on the curing unit used (p < 0.001). Curing time did not affect the colour changes of the specimens (p = 0.4). The results of this study suggest that composite materials undergo measurable changes due to the curing unit exposure.

Temperature rise during polymerization of three different provisional materials.

The purpose of this study was to evaluate the temperature rise during polymerization of three different provisional materials by direct method on two different dentin disc thicknesses. Two autopolymerizing; bis-acrylic composite (Fill-in; Kerr), polymethyl methacrylate (Temdent; Weil Dental), and one light polymerizing composite (Revotek LC; GC) provisional restoration materials were used in this study. Sixty dentin discs were prepared from extracted molars (diameter, 5 mm; height, 1 or 2 mm). These dentin discs (1 or 2 mm) were placed on apparatus developed to measure temperature rise. The temperature rise during polymerization was measured under the dentin disc with a J-type thermocouple wire that was connected to a data logger. Statistical analysis was performed with two-way analysis of variance followed by Tukey HSD test (alpha=0.05). Temperature rise values statistically varied according to the provisional restoration material used (light polymerized, auto polymerized; P<0.001) and the dentin thickness (1 and 2 mm; P<0.001). The polymethyl methacrylate based provisional material induced significantly higher temperature rise than other provisional restoration materials at 2-mm dentin thickness (P<0.01). At 1-mm dentin thickness, polymethyl methacrylate and composite induced significantly higher temperature increase than bis-acrylic composite provisional material (P<0.05). The risk for heat-induced pulpal damage should be taken into consideration during polymerization of provisional materials in deep cavities in which dentin thickness is less than 1 mm.