White-opaque flowable composite liner as a depth marker in composite restorations prevents tooth substance loss in filling removal: a randomized double-blinded in vitro study.

OBJECTIVES: Removal of esthetic restorations leads to loss of tooth structure and the extent of the loss is difficult to estimate due to exact-shade matching. This randomized double-blinded in vitro study aimed examining the influence of a white-opaque flowable composite depth marker as an optical removal aid for tooth substance preservation and shortened restoration removal time. MATERIALS AND METHODS: Class II cavities (n = 100) in extracted healthy mandibular molars (n = 50, two runs) were prepared, filled, and the restoration removed. Tooth weight and volume (before and after) and removal time were measured and remnants visually documented. An optimal tooth shade-matched flowable composite liner was used as control. RESULTS: Tooth structure loss was significantly lower using a white-opaque liner. Mean values for volume/weight loss were 0.037 ± 0.030 g and 0.016 ± 0.005 cm3 (p < 0.01) for white-opaque liner; 0.067 ± 0.000 g and 0.028 ± 0.003 cm3 (p < 0.01) for tooth-colored composite. Removal time and number of pulp chamber perforations showed no significant differences (p = 0.80). CONCLUSIONS: Within the limitations of this randomized double-blinded in vitro study, the use of a white-opaque flowable liner as a depth marker may provide the practitioner a visual aid in the replacement of a composite restoration and may protect against tooth structure loss. CLINICAL RELEVANCE: When restoration replacement is indicated, removal of esthetic restorations often causes tooth structure loss due to difficult optical color matching. Using a white-opaque flowable liner as a depth marker clinically aids in restoration removal and protects against tooth structure loss.

One-year Clinical Performance of Flowable Bulk-fill Composite vs Conventional Compomer Restorations in Primary Molars.

PURPOSE: To evaluate the clinical performance of a flowable bulk-fill composite vs a compomer in Class II cavities of primary molars. MATERIALS AND METHODS: In a clinical study, 100 restorations were placed in two randomly assigned comparable Class II cavities in 32 children (aged 6.7 ± 1.2 years) with at least one bulk-fill composite (Venus Bulk Fill, Heraeus Kulzer) and one compomer (Dyract eXtra, Dentsply). After caries excavation, the adhesive Scotchbond Universal (3M Oral Care) was applied in self-etching mode. According to the manufacturer's instructions, Venus Bulk Fill was used for the entire Class II cavity of primary molars without a cover layer. After visible-light curing, both restorations were finished and polished. Both restorative materials were evaluated at baseline and after one year, including esthetic, functional, and biological parameters, using the FDI criteria. The Mann-Whitney U-test was used to determine the difference in the complete scores at baseline and after one year (p < 0.05). RESULTS: After one year, 99 restorations were reevaluated; one tooth had exfoliated physiologically. Concerning the esthetic parameters, Dyract eXtra showed slightly higher scores than Venus Bulk Fill. Both materials showed similar scores regarding functional and biological parameters. No severe postoperative sensitivities or side-effects were reported. There was no statistically significant difference between the performance of Venus Bulk Fill and Dyract eXtra for primary molars. CONCLUSION: The flowable bulk-fill composite Venus Bulk Fill can be considered as an alternative material for clinical use in primary teeth, but longer-term studies might still be needed.

Visible Light Curing Devices - Irradiance and Use in 302 German Dental Offices.

PURPOSE: To determine the irradiance delivered by visible-light curing (VLC) units and obtain information about the exposure times and the maintenance protocols used by dentists. MATERIALS AND METHODS: The irradiance (mW/cm2) delivered by 526 VLCs from 302 dental offices from the Rhine-Main area, Germany, was measured using an integrating sphere (IS) and a MARC patient simulator (M-PS); additional information was gathered using a survey. RESULTS: Irradiance was measured from 117 standard quartz-tungsten-halogen (QTH), 5 high-power QTH, 2 LED 1st-generation, 333 LED 2nd-generation, 61 LED 3rd-generation, and 8 plasma-arc curing (PAC) units. Depending on the measurement method, 8% (IS) or 11% (M-PS) of the VLCs delivered < 400 mW/cm2. Depending on the VLC, the shortest exposure times required to deliver a radiant exposure of 16 J/cm2 ranged from 7 to 294 s. The number of exposure cycles used by dentists when light curing a restoration ranged from 1 to 14. The shortest total exposure time used by dentists on a restoration was 5 s, the maximum was 200 s, and the median was 20 s. Of the 526 VLCs, 41% had intact, undamaged light tips. Only half of the dental offices checked the irradiance from their VLCs regularly, 97% disinfected the VLC, and 86% used eye protection. CONCLUSION: Approximately 10% of the VLCs delivered < 400 mW/cm2 and 14% of the dental offices used no form of eye protection. To achieve sufficient light curing of RBC restorations, more awareness about the VLCs used in the dental office is required.

Effect of thermocycling with or without 1 year of water storage on retentive strengths of luting cements for zirconia crowns.

STATEMENT OF PROBLEM: Bond stability between zirconia crowns and luting cement and between cement and dentin is a main concern; however, only limited evidence is available as to its longevity. PURPOSE: The purpose of this in vitro study was to measure the retentive strengths of 7 self-adhesive cements (RelyX Unicem Aplicap, RelyX Unicem Clicker, RelyX Unicem 2 Automix, iCEM, Maxcem Elite, Bifix SE, SpeedCem), 2 adhesive cements with self-etch primers (Panavia 21, SEcure), 1 glass ionomer cement (Ketac Cem), 1 resin-modified glass ionomer cement (Meron Plus), and 1 zinc phosphate cement for luting zirconia crowns (LAVA) to extracted teeth after thermocycling with or without 1 year of water storage. MATERIAL AND METHODS: Two-hundred-forty extracted human molars (2 treatments; n=10 per cement) were prepared in a standardized manner. All cements were used according to the manufacturers' recommendations. The intaglios of the crowns were treated with airborne-particle abrasion. After thermocycling (×5000, 5°C/55°C) with or without 1 year of water storage, the cemented ceramic crowns were removed by using a Zwick universal testing device. Statistical analyses were done with the Wilcoxon rank sum and the 2-independent-samples Kolmogorov-Smirnov test. RESULTS: Median retentive strengths [MPa] for specimens thermocycled only/thermocycled with 1 year of water storage were as follows: Panavia 21: 1.7/2.5, SEcure: 3.0/3.0, RelyX Unicem Aplicap: 3.1/3.4, RelyX Unicem Clicker: 4.1/4.2, RelyX Unicem 2 Automix: 3.8/3.1, iCEM: 2.3/2.7, Maxcem Elite: 3.0/3.2, Bifix SE: 1.7/1.7, SpeedCem: 1.3/1.6, Meron Plus: 3.1/2.7, Ketac Cem: 1.4/1.4, and zinc phosphate cement: 1.1/1.6. Statistically significant differences were found only among specimens thermocycled only or thermocycled with 1-year water storage (P<.001). CONCLUSIONS: Significant differences in retentive strengths were observed among cements after thermocycling only or thermocycling with 1 year of water storage, but not for the effect of the additional 1 year of water storage.

Clinical comparison of gluma and Er:YAG laser treatment of cervically exposed hypersensitive dentin.

PURPOSE: To compare the desensitizing effects of a glutaraldehyde-based desensitizing system (Gluma) and an Er:YAG laser treatment on cervically exposed hypersensitive dentin. METHODS: A total of 22 subjects (mean age: 39 +/- 13.7 years; 15 females, 7 males) suffering from cervical dentin hypersensitivity was included in a prospective, split-mouth clinical study. The teeth were treated on one side of the mouth with the glutaraldehyde-based desensitizing system and on the other side with the Er:YAG laser. Sensitivity perception was recorded before treatment (baseline), during and immediately after treatment, after 1 week, 1 month, 3 months and 6 months. The subjects were asked to rate the sensitivity experienced during air stimulation by placing a mark on a visual analogue scale (VAS). RESULTS: Both techniques showed an effective reduction of cervical dentin hypersensitivity. The subjects experienced equal improvements compared to their status before and 6 months after treatment with both methods (P<0.001).

Photoelastic determination of polymerization shrinkage stress in low-shrinkage resin composites.

Low-shrinkage resin composites are in the focus of research in posterior resin composite restoratives. The aim of the study was to examine the polymerization shrinkage stress of new composites (Venus Diamond/ Heraeus Kulzer; SDR/DENTSPLY) and an experimental low-shrinkage resin composite (Ormocer/VOCO) in comparison to established low-shrinkage resin composites (Filtek Silorane/ 3M ESPE; els/Saremco; Filtek Supreme XT/3M ESPE; Clearfil Majesty Posterior/Kuraray). Cylindrical cavities (∅ 4 mm) in Araldit-B epoxy resin plates (40×40×4 mm) were pretreated with the Rocatec system to ensure bonding of the resin composites. The resin composite specimens (n = 10) were exposed to light for 60 s with a QTH curing device (Translux energy, Heraeus Kulzer, Germany). The samples were stored dark and dry (23 °C). Polymeri-zation shrinkage stress data (MPa) 4 min and 24 h post exposure were calculated based on the diameter of the first-order isochromatic rings, obtained from the Araldit plates. The statistical analysis of the obtained data was carried out with the Wilcoxon test (p = 0.05). After 24 h, the following mean stress values and standard deviations were obtained: Venus Diamond 3.4 ± 0.27 MPa; SDR 3.3 ± 0.26 MPa; exp. Ormocer 4.0 ± 0.18 MPa; Filtek Silorane 2.8 ± 0.19 MPa; els 2.5 ± 0.09 MPa; Filtek Supreme XT 6.0 ± 0.20 MPa; and Clearfil Majesty Posterior 5.6 ± 0.15 MPa. For all materials, higher polymerization stress values were recorded after 24 h. All differences in the shrinkage data obtained after 24 h were statistically significant (p < 0.05) except Venus Diamond/SDR. Venus Diamond, els and SDR showed shrinkage data closer to that of Filtek Silorane.

Shortest exposure time possible with LED curing lights.

PURPOSE: To investigate the shortest exposure time of different light emitting diode (LED)-curing devices for different resin composites in a clinically relevant laboratory model. METHODS: Nine LED curing devices (Bluephase, Bluephase 16i, Bluephase G2, Bluephase 20i/Ivoclar Vivadent, DEMI/sds Kerr, Elipar FreeLight 2, Elipar S10/3M ESPE, Radii plus/SDI, mini LED Autofocus/Satelec) were investigated to polymerize Tetric EvoCeram (TEC) and Filtek Supreme XT B (FS) in the shades A1, A2, A3, A3.5, and A4. The Bluephase 20i was investigated in its high power and turbo modes. Stainless steel molds (Ø = 5 mm, h = 6 mm, six resin composite test samples per curing device, material, and shade) were filled in three increments of 2 mm thickness each and incrementally exposed with the light guide tip in a 7 mm distance from the bottom side to simulate a Class II curing situation. Surface hardness was measured 10 minutes post exposure at bottom surfaces of resin samples (n=3 per sample). A bottom/top-surface hardness ratio of 80% of a reference surface hardness cured at a zero-distance (40 seconds) was defined as clinically acceptable for safe curing. A statistical analysis (Excel) was carried out. RESULTS: To ensure a ratio in surface hardness of at least 80% the minimal exposure time(s) were: Elipar FreeLight 2, DEMI: TEC and FS: 10 seconds for all shades, except DEMI FS A4: 20 seconds. Elipar S10: 10 seconds for both, TEC and FS shades A2-A4 but 5 seconds for shades A1. Bluephase, Bluephase 16i and Bluephase G2: FS: 10 seconds for shades A1-A3.5; 20 seconds for shade A4. TEC: Bluephase: A1-A3.5: 10 seconds, A4: 20 seconds. Bluephase 16i: A1-A3: 10 seconds; A3.5 + A4: 30 seconds. Bluephase G2: A1-A3: 10 seconds; A3.5 + A4: 20 seconds. Bluephase 20i-HIP: 10 seconds for all shades of TEC and FS, Bluephase 20i-Turbo: 10 seconds for all shades of TEC but 5 seconds for all shades of FS: Radii plus: TEC A1-A3: 10 seconds; A3.5+A4: 20 seconds. FS A1, A2 and A4: 10 seconds; A3+A3.5: 20 seconds. Mini LED Autofocus: TEC A1, A3, A3.5: 10 seconds; A2: 15 seconds; A4: 20 seconds. FS A1: 5 seconds; A2-A4: 10 seconds. In its turbo mode with a 5-second exposure time, the Bluephase 20i was able to polymerize all shades of FS, but not of TEC. For the Elipar S10 and the Mini LED Autofocus this was also possible for the A1 shade of FS; for Elipar S10 additionally for TEC. The higher power of the Bluephase G2 and the S10 LED allowed the use of an enhanced light guide tip diameter while the exposure time was not affected compared to their predecessors equipped with an 7.5 or 8 mm light guide tip diameter respectively. Nevertheless, 10 seconds should be the minimal exposure time recommended for lighter shades under optimal circumstances.

Protein structure determination via an efficient geometric build-up algorithm.

BACKGROUND: A protein structure can be determined by solving a so-called distance geometry problem whenever a set of inter-atomic distances is available and sufficient. However, the problem is intractable in general and has proved to be a NP hard problem. An updated geometric build-up algorithm (UGB) has been developed recently that controls numerical errors and is efficient in protein structure determination for cases where only sparse exact distance data is available. In this paper, the UGB method has been improved and revised with aims at solving distance geometry problems more efficiently and effectively. METHODS: An efficient algorithm (called the revised updated geometric build-up algorithm (RUGB)) to build up a protein structure from atomic distance data is presented and provides an effective way of determining a protein structure with sparse exact distance data. In the algorithm, the condition to determine an unpositioned atom iteratively is relaxed (when compared with the UGB algorithm) and data structure techniques are used to make the algorithm more efficient and effective. The algorithm is tested on a set of proteins selected randomly from the Protein Structure Database-PDB. RESULTS: We test a set of proteins selected randomly from the Protein Structure Database-PDB. We show that the numerical errors produced by the new RUGB algorithm are smaller when compared with the errors of the UGB algorithm and that the novel RUGB algorithm has a significantly smaller runtime than the UGB algorithm. CONCLUSIONS: The RUGB algorithm relaxes the condition for updating and incorporates the data structure for accessing neighbours of an atom. The revisions result in an improvement over the UGB algorithm in two important areas: a reduction on the overall runtime and decrease of the numeric error.

Influence of different luting concepts on long term retentive strength of zirconia crowns.

PURPOSE: To evaluate the retentive strength of a resin cement in combination with a conventional adhesive (Variolink II/Syntac Classic), two resin cements with self-etching adhesives (Panavia F 2.0/ED Primer, Multilink/Multilink Primer A/B), two self-adhering cements (RelyX Unicem Aplicap, Maxcem), and a resin-modified glass-ionomer cement (FujiCem) after cementation of zirconium-oxide ceramic crowns (LAVA) on extracted human teeth. METHODS: 160 extracted teeth (n=20) were prepared in a standardized manner (10 degrees, h=3 mm). The crowns' inner surfaces were air-abraded/sandblasted (Rocatec Pre). Additional pretreatment was carried out with Multilink (metal primer or Monobond S). With RelyX Unicem Aplicap, an additional group that also received Rocatec Plus pretreatment was examined. Immediately after thermocycling (x5000, 5/55 degrees C), 50% of the luted ceramic crowns (n=10) were pulled off along the path of insertion (Zwick 1425); the remaining samples (n = 10) were tested after 1 year of water storage. Statistical analysis was performed using the Wilcoxon Mann-Whitney U-test and Bonferroni adjustment at the 5% level of significance. RESULTS: The retentive strength values (N/mm2) after 1 year of water storage were (Min/Q1/Median/Q3/Max): Variolink II/Syntac: 1.0/1.9/2.5/3.3/5.2, Panavia F 2.0: 1.5/1.8/2.1/3.6/5,4, Multilink/Metallprimer: 2.9/4.6/5.3/9.4/11,7, Multilink/Monobond S: 4.1/4.8/5.4/7.7/12.6, RelyX Unicem Aplicap: 3.9/6.3/7.5/9.0/10.7, RelyX Unicem Aplicap/Rocatec Plus: 4.4/5.8/7.2/9.4/11.9, Maxcem: 0.9/2.2/3.0/3.3/4.5, FujiCem: 1.6/2.7/4.3/5.4/6.7. RelyX Unicem Aplicap and Multilink showed the highest median retentive strength values. Long-term water storage did not affect the retentive strength.

Minimal exposure time of different LED-curing devices.

OBJECTIVES: The purpose of the study was to investigate the shortest possible exposure time of different LED-curing devices for five different resin composites in a clinically relevant in vitro-model, where a 7 mm distance from the light guide tip to the bottom side of the cavity was compiled. METHODS: Resin composite samples (Tetric EvoCeram A3, Filtek Supreme XT A3B, Premise A3, CeramX Mono M5, QuiXfil) were filled in three increments of 2mm thickness each in stainless steel moulds (Ø=5 mm, h=6 mm, n=9). The samples were incrementally exposed to different blue LED-curing devices (Bluephase, Bluephase C8, Bluephase 16i/Ivoclar Vivadent, L.E. Demetron II/sds Kerr, Elipar FreeLight 2/3M ESPE, Smartlite PS/DENTSPLY, Translux Power Blue/Heraeus) according to the manufacturer's recommendations at a distance of 7 mm from the bottom of the cavity to simulate a class II-curing situation. Surface hardness was measured (Zwick Z2.5/TS1S) 10 min post-exposure at the bottom surfaces of the resin sample. A bottom/top-surface hardness ratio of 80% of a reference sample (2mm thickness, 40s), was defined as clinically acceptable for safe curing. A descriptive statistical analysis was carried out. RESULTS: The curing devices Bluephase, Bluephase C8, Smartlite PS and Translux Power Blue could cure all composite resins investigated sufficiently in the exposure time recommended by the manufacturers (10-20s). The curing device Bluephase 16i and L.E. Demetron II only cured the composite Quixfil sufficiently in the exposure time recommended by the manufacturer. FreeLight 2+ allowed a 10s exposure time for all materials except Ceram X Mono (20s). SIGNIFICANCE: When incrementally exposed, all resin composites investigated were polymerized sufficiently at a maximum of 20s exposure time.

Marginal integrity of class V restorations: SEM versus dye penetration.

OBJECTIVES: To perform an in vitro investigation on the marginal integrity of different adhesives (Optibond FL, Scotchbond 1XT, Clearfil SE Bond, Adper Prompt L-Pop, S(3) Bond, iBond exp., Adper Prompt L-Pop) in combination with Tetric Ceram as well as an experimental silorane-restorative (Hermes, Hermes Bond; 3M ESPE) using SEM and dye penetration (2% methylene blue) in a comparative manner. METHODS: Standardized class V-cavities (3 mm x 1.5 mm) were prepared in 70 extracted human teeth (n=10). The adhesives were applied according to manufacturers' instructions. The cavities were restored with three increments. After finishing and polishing (Sof-Lex discs) and thermocycling (5000x, 5/55 degrees C), replicas were taken and the teeth immersed in the dye for 10s (D10) and evaluated. After another penetration of 30 min (D30) a final evaluation of the percentage of dye-penetrated margins was conducted. RESULTS: The median percentages in marginal gaps (%) at the enamel margins for the three methods investigated (D10/D30/SEM) were--Optibond FL: 0/0/4, Scotchbond 1 XT: 5/16/11, Clearfil SE Bond: 0/0/0, S(3) Bond: 0/0/1, iBond exp.: 20/42/12, Adper Prompt L-Pop: 5/23/8, Hermes/Hermes Bond: 5/45/24. Cementum margins--Optibond FL: 0/1/0, Scotchbond 1 XT: 0/21/23, Clearfil SE Bond: 0/0/4, S(3) Bond: 0/0/0, iBond exp.: 0/0/0, Adper Prompt L-Pop: 10/32/23, Hermes/Hermes Bond: 0/0/13. After pooling the data of all groups, a Spearmann's rho test showed a good correlation between the methods D10 and D30 at the enamel margins and at the entire cavity margins (correlation coefficient 0.8 and 0.7). SIGNIFICANCE: SEM did not correlate with the results obtained from D10 (correlation coefficient <0.5). A fair correlation was found between SEM and D30 for the entire cavity margin but a good correlation for the enamel margins. No correlation between investigation methods was determined at the cementum margins. D30 showed a better correlation to SEM than D10 did. Therefore, 30 min of dye penetration time seems to be more suitable than 10 s.

In-vitro shear bond strength of self-etching versus traditional adhesives for orthodontic luting.

OBJECTIVE: To determine the enamel shear bond strength (SBS) of various established (Resulcin Aqua Prime & Monobond N [RA], Prompt L-Pot III [PLP]) and experimental (AC-Bond [AC], AC-Bond + Desensitizer [ACD]) self-etching adhesives in comparison to fourth (Total Etch, Primer and Bonding have separate liquids; OptiBond FL [FL]) and fifth-generation (Total Etch, Primer and Bonding "One Bottle"; Excite [EX], Gluma Comfort Bond [CB]) adhesives. MATERIALS AND METHODS: All adhesives were applied on flattened human enamel surfaces following the manufacturers' instructions and light-cured using a quartz-tungsten-halogen curing device. 3.5 x 2.0 mm Tetric Ceram A2 composite cylinders were sheared off (Zwick Universal-testing-machine 1445, 1 mm/min) after thermocycling (5-55 degrees C, 5000x). Normal distribution was tested for all groups and analysis of variance was conducted. The t-test (5% level, Bonferroni-correction) was used for statistical analysis to evaluate intergroup differences. RESULTS: Shear bond strength in enamel: Resulcin Aqua Prime & Monobond N: 27.0 +/- 5.8 MPa, Prompt L-Pop III: 15.9 +/- 3.4 MPa, AC-Bond: 28.1 +/- 4.4 MPa, AC-Bond + Desensitizer: 22.2 +/- 4.1 MPa, OptiBond FL: 33.2 +/- 3.2 MPa, Excite: 30.5 +/- 5.1 MPa, Gluma Comfort Bond: 30.1 +/- 3.7 MPa. OptiBond FL demonstrated significantly higher SBS (p < 0.002) in enamel than Resulcin Aqua Prime & Monobond N, AC-Bond, AC-Bond + Desensitizer and Prompt L-Pop III. Resulcin Aqua Prime & Monobond N performed significantly better than Prompt L-Pop III, but did not differ from AC-Bond or AC-Bond + Desensitizer. The SBS values of Excite and Gluma Comfort Bond were both on the same level of significance as AC-Bond and Resulcin Aqua Prime & Monobond N, but the former showed superior results to AC-Bond + Desensitizer and Prompt L-Pop III. Prompt L-Pop III yielded significantly lower SBS-values than all the other products evaluated. CONCLUSION: Resulcin Aqua Prime & Monobond N and AC-Bond did not differ significantly from established 5th-generation products. Further in-vivo studies are required to investigate intra-oral stability and resistance against changing forces and force directions.

Two-year clinical performance of a nanofiller vs a fine-particle hybrid resin composite.

The aim of the study was to evaluate the clinical performance of the nanofiller resin composite Filtek Supreme (3M ESPE) vs the conventional fine hybrid resin composite Tetric Ceram (Ivoclar Vivadent) in stress-bearing posterior cavities. In accordance with a split mouth study design, 50 patients (35.7+/-11.3 years) received at least one pair of Filtek Supreme and Tetric Ceram restorations in each of two comparable class II cavities. To obtain comparability, the adhesive Scotchbond 1 was used for all the restorations. After 2 years, the restorations (total number 112) were scored according to the Ryge criteria. After 2 years (recall rate 100%), the results (%) of the Ryge evaluation for the two groups Filtek Supreme/Tetric Ceram were marginal adaptation: Alfa 96/96, Bravo 2/2, Charlie 2/0, and Delta 0/2; anatomic form: Alfa 98/98, Bravo 0/0, and Charlie 2/2; secondary caries: Alfa 100/100 and Bravo 0/0; marginal discoloration: Alfa 98/100, Bravo 2/0, and Charlie 0/0; surface: Romeo 95/95, Sierra 4/4, Tango 0/0, and Victor 2/2; and color match: Oscar 46/57, Alfa 50/39, Bravo 2/4, and Charlie 2/0. One Tetric Ceram and one Filtek Supreme restoration showed fractures that needed restorative intervention. No severe postoperative sensitivities were reported within the observation period. All restored teeth remained vital; the integrity of all the teeth was scored Alfa. After 2 years, no statistically significant differences (Wilcoxon-Mann-Whitney test) was found between the two restorative materials investigated. Therefore, Filtek Supreme, based on a new nanofiller technology, has proved efficaciousness for clinical use in stress-bearing posterior cavities.

Clinical study on the effectiveness and side effects of hexetidine and chlorhexidine mouthrinses versus a negative control.

OBJECTIVES: The aim of this clinical, controlled double-blind trial was to evaluate the effectiveness and side effects of two different mouthrinses. METHOD AND MATERIALS: Ninety subjects with gingivitis (or slight periodontitis) were randomly allocated to three groups: group 1, Chlorhexamed (0.1% chlorhexidine); group 2, Hexoral (0.1% hexetidine); and group 3, a placebo-control compound. The subjects were instructed on how to use the mouthrinse. At baseline, as well as after 2 and 4 weeks, the Approximal Plaque Index (API), the Bleeding Index (BI), the Community Periodontal Index of Treatment Needs, the Gingival Index (GI), and the Discoloration Index (DI), were measured. Statistical analysis was carried out with the Kruskal-Wallis test, Fisher's exact test, and Wilcoxon test. RESULTS: In group 1, the mean API improved significantly (P < or = .001) after 4 weeks. The mean BI was reduced significantly, as was the GI. In group 2, the mean API and the mean BI both decreased significantly, and a statistically significant reduction of the GI was also seen. In group 3, significant improvements of the mean values of all parameters were documented after 4 weeks. When comparing group 3 with groups 1 and 2, the difference in the reduction of the API was statistically significant (P < .002). No statistical difference could be shown when comparing groups 1 and 2. Regarding the improved results of the BI and the GI, no statistically significant difference was found in the effectiveness of all 3 compounds. All 3 groups showed some increase in the mean DI after 4 weeks. Comparing groups 1 and 2 directly, the difference in the increase in the discoloration of the teeth was statistically significant (P = .0035). There was no statistical difference in the mean discoloration scores comparing groups 2 and 3. CONCLUSION: This double-blind clinical trial demonstrated Hexoral to be a useful alternative to Chlorhexamed mouthrinse, as well as one causing less discoloration.

In vitro retentive strength of zirconium oxide ceramic crowns using different luting agents.

STATEMENT OF PROBLEM: In contrast to gold crowns, in vitro determination of the retentive strength of all-ceramic crowns is more difficult because components allowing connection to testing apparatus are not as easily integrated into the all-ceramic material. Nevertheless, retentive strength data are crucial for obtaining information about the potential clinical performance of luting cements for all-ceramic restorations. Therefore, a new in vitro model was necessary to evaluate the retentive strength of all-ceramic crowns. PURPOSE: The purpose of this in vitro study was to determine the retentive strength of 4 resin-cement systems, a compomer, a glass-ionomer cement, a resin-modified glass-ionomer cement, and a self-adhesive resin for luting zirconium oxide ceramic crowns. MATERIAL AND METHODS: One-hundred-twenty extracted human teeth were randomly divided into 12 groups (n = 10) and prepared in a standardized manner (5-degree taper, 3-mm occlusogingival height). All-ceramic crowns (Lava) were fabricated in a standardized manner for each tooth. The following cements and corresponding bonding regimens were used to lute the crowns to the teeth according to manufacturers' recommendations: CO, Compolute/EBS Multi; CO/RT, Compolute/EBS Multi/Rocatec; CB, Superbond C and B; CB/RT, Superbond C and B/Rocatec; CB/PL, Superbond C&B/Porcelain Liner M; PA, Panavia F; DC, Dyract Cem Plus/Xeno III; CH/PL, Chemiace II/Porcelain Liner M; RL, RelyX Luting, K/C, Ketac Cem/Ketac Conditioner; K, Ketac Cem; and RU, RelyX Unicem. After thermal cycling (5000 cycles, 5 degrees C-55 degrees C), the outer surfaces of the cemented zirconium oxide ceramic crowns were treated (Rocatec) to improve bonding and then placed into a low-shrinkage epoxy resin block (Paladur). The block/crown and tooth components for each specimen were connected to opposing ends of a universal testing machine so that crown retention could be measured. Crowns were removed from teeth along their path of insertion. The retentive surface area (mm 2 ) was determined individually for each tooth. Statistical analyses were performed using the Wilcoxon exact test, (alpha =.05) and a Bonferroni correction (alpha =.001). RESULTS: The median (minimum/maximum) retentive strength values (MPa) were as follows: CO, 1.7 (0.6/4.3); CO/RT, 3.0 (1.3/5.4); CB, 4.8 (3.7/7.9); CB/RT, 8.1 (4.2/12.7); CB/PL, 5.3 (3.7/10.2); PA, 4.0 (3.3/5.1); DC, 3.3 (2.1/5.6); CH/PL, 4.0 (1.3/6.3); RL, 4.7 (2.8/6.6); K/C, 1.8 (0.6/2.3); K, 1.9 (0.2/4.5); and RU, 4.8 (2.5/6.7). Superbond C&B (+ Rocatec) specimens showed the highest median retentive strength, but were not significantly different from Superbond C&B without Rocatec pretreatment of the all-ceramic crown's inner surface. Compolute specimens also did not benefit significantly from the Rocatec pretreatment. Within the materials used without pretreatment of the ceramic, Superbond C&B, Panavia, Dyract Cem Plus, RelyX Luting, and RelyX Unicem showed the highest median retentive strength values and were not significantly different. CONCLUSION: Within the conditions of this study, the compomer-cement, the resin-modified glass-ionomer cement, and the self-adhesive resin luting agent had the same level of retentive quality as the resin luting agents, Superbond C&B, and Panavia. Rocatec pretreatment of the ceramic surface did not improve the retentive strengths of Compolute and Superbond C&B.

Depth of cure of LED vs QTH light-curing devices at a distance of 7 mm.

PURPOSE: To determine the depth of cure of 5 blue LED curing devices compared to that obtained with 3 QTH curing devices. MATERIALS AND METHODS: The LED curing devices tested were 1) e-Light: 40 s; 2) Elipar FreeLight: 40 s; 3) Elipar FreeLight 2: 20 s and 40 s; 4) Ultra-Lume LED 2: 20 s and 40 s; 5) LEDemetron 1: 20 s and 40 s. The QTH curing devices tested were 1) Optilux 501: standard light guide 20 s and 40 s, turbo light guide 20 s; 2) Elipar TriLight: 40 s; 3) Astralis 10: 20 s. Surface hardness was measured (Zwick Z2.5/TS1S) 10 min after exposure on the top and bottom surface of resin samples (Tetric Ceram A3, 1 to 5 mm; 0.5 mm increment, diameter 5 mm, n = 9) which were cured at a distance of 7 mm from the bottom of the sample to the light-guide tip to simulate a Class II curing situation. A reference sample was cured under direct contact with the light guide. The reference sample with the greatest top surface hardness of all devices measured served as the overall control. A bottom/top surface hardness ratio of > or = 80% of the reference sample cured at zero distance was defined as clinically acceptable for safe curing. A descriptive statistical analysis was carried out. RESULTS: With QTH lamps, the mean maximum resin composite sample thickness which cured sufficiently (relative surface ratio > or = 80%) was: 3 mm for Optilux 501, standard light guide, 40 s; 2.5 mm for Trilight, 40 s; and 1.5 mm for Astralis 10, 20 s. The first-generation LED curing devices FreeLight and GC e-Light, both applied for 40 s, and the Optilux 501 operated for 20 s with the standard and the turbo light guide could not sufficiently cure a 1-mm-thick sample at a distance of 7 mm. The new FreeLight 2 and the Ultra-Lume LED 2 cured resin samples up to 2.5 mm thick in 40 s with a relative surface ratio > or = 80%, while no sufficient depth of cure was found after 20 s exposure time for the FreeLight 2. However, a 1.5-mm depth of cure with the Ultra-Lume LED 2 and the LEDemetron 1 with the 13/11 mm light guide was obtained after 20 s. The LEDemetron 1 equipped with a 13/8 mm light guide reached a depth of cure of 2.0 mm. No significant difference was found between the Elipar FreeLight 2, Ultra-Lume LED 2, and LEDemetron 1 in their overall curing potential (linear statistical model, 5% level, Bonferroni-correction) given 40 s or 20 s of exposure time. CONCLUSION: Application of the first-generation LED curing devices FreeLight and e-Light did not ensure clinically sufficient depths of cure, while the new high-power LED curing devices FreeLight 2, Ultra-Lume LED 2, and LEDemetron 1 showed a curing potential equal to the Optilux 501, given 40 s of exposure time.

In vivo validation of the historical in vitro thermocycling temperature range for dental materials testing.

In dental research, restorative materials have been regularly subjected to alternating in vitro thermal stress in investigations since the 1950s, in order to simulate in vivo alternating temperature stress and to artificially stress them in vitro. The provocation temperature is mostly 5 degrees C for cold provocation, and 55 degrees C for hot provocation. These temperatures are determined quite arbitrarily based on very few examinations in vivo. Extensive temperature data for the approximal space of teeth, which is decisive for the success of fillings adhesively attached to dentin, has so far not been addressed. The objective of this study was to examine the interproximal temperature characteristics created in the space of all teeth in vivo with thermal alternating stress, and therefore to validate the in vitro standardized thermal alternating stress of 5-55 degrees C. Fifteen study participants with healthy teeth were used to determine the temperature in each inter-dental space, resulting from hot/cold provocation in the upper and lower jaw, from the central incisor to the second molars. This was performed by a thermal element (cable sensor GTF 300, Greisinger Electronic GmbH, Regenstauf, Germany). The temperature sensor was attached with dental floss into the interproximal space and the temperature was recorded by the computer. The participants in the pilot test had to state when they were able to sip an 85 degrees C hot drink. That particular temperature value was taken for hot provocation as maximum temperature reference. Cold ice water (0 degrees C) was used for cold provocation as minimum temperature reference. The respective recordings with a total of 14 measurements for each individual were performed simultaneously in the upper and lower jaw. The study participants were to start with hot provocation, followed by cold provocation. This cycle was repeated at least once with an individual dwell time. The highest recorded approximal space temperature was 52.8 degrees C in the lower jaw, between the first and the second premolar. The lowest temperature of 13.7 degrees C was recorded in two participants in the upper jaw, between the 1st and 2nd incisor, and between the two central incisors. The mean of the maximum temperatures was 43.8+/-3.7 degrees C, and the mean of the minimum temperatures 24.2+/-4.6 degrees C. The mean initial temperature was 35.2+/-1.3 degrees C. None of the recordings reached either the upper threshold (55 degrees C) or the lower threshold (5 degrees C). This study showed that the actual thermal stress in the interproximal space of teeth is slightly lower than the one used in in vitro examinations. For class II cavities, most of the alternating temperature stress limits selected at 5-55 degrees C cover the actually occurring temperature interval quite well.