Attenuation of near-ultraviolet, visible and near-infrared light in sound and carious human enamel and dentin.

OBJECTIVES: This in vitro study aimed to investigate the optical attenuation of light at 405, 660 and 780 nm sent through sound and carious human enamel and dentin, including respective individual caries zones, as well as microscopically sound-appearing tissue close to a carious lesion. MATERIALS AND METHODS: Collimated light transmission through sections of 1000-125-µm thickness was measured and used to calculate the attenuation coefficient (AC). The data were statistically analysed with a MANOVA and Tukey's HSD. Precise definition of measurement points enabled separate analysis within the microstructure of lesions: the outer and inner halves of enamel (D1, D2), the translucent zone (TZ) within dentin lesions and its adjacent layers, the enamel side of the translucent zone (ESTZ) and the pulpal side of the translucent zone (PSTZ). RESULTS: The TZ could be distinguished from its adjacent layers and from caries-free dentin at 125 µm. Sound-appearing dentin close to caries lesions significantly differed from caries-free dentin at 125 µm. While sound and carious enamel exhibited a significant difference (p < 0.05), this result was not found for D1 and D2 enamel lesions (p > 0.05). At 405 nm, no difference was found between sound and carious dentin (p > 0.05). CONCLUSIONS: Light optical means enable the distinction between sound and carious tissue and to identify the microstructure of dentin caries partially as well as the presence of tertiary dentin formation. Information on sample thickness is indispensable when interpreting the AC. CLINICAL RELEVANCE: Non-ionising light sources may be suitable to detect lesion progression and tertiary dentin.

Diagnostic validity of early proximal caries detection using near-infrared imaging technology on 3D range data of posterior teeth.

OBJECTIVES: This in vitro study analysed potential of early proximal caries detection using 3D range data of teeth consisting of near-infrared reflection images at 850 nm (NIRR). MATERIALS AND METHODS: Two hundred fifty healthy and carious permanent human teeth were arranged pairwise, examined with bitewing radiography (BWR) and NIRR and validated with micro-computed tomography. NIRR findings were evaluated from buccal, lingual and occlusal (trilateral) views according to yes/no decisions about presence of caries. Reliability assessments included kappa statistics and revealed high agreement for both methods. Statistical analysis included cross tabulation and calculation of sensitivity, specificity and AUC. RESULTS: Underestimation of caries was 24.8% for NIRR and 26.4% for BWR. Overestimation was 10.4% for occlusal NIRR and 0% for BWR. Trilateral NIRR had overall accuracy of 64.8%, overestimation of 15.6% and underestimation of 19.6%. NIRR and BWR showed high specificity and low sensitivity for proximal caries detection. CONCLUSIONS: NIRR achieved diagnostic results comparable to BWR. Trilateral NIRR assessments overestimated presence of proximal caries, revealing stronger sensitivity for initial caries detection than BWR. CLINICAL RELEVANCE: NIRR provided valid complement to BWR as diagnostic instrument. Investigation from multiple angles did not substantially improve proximal caries detection with NIRR.

Adhesion and whitening efficacy of P11-4 self-assembling peptide and HAP suspension after using NaOCl as a pre-treatment agent.

BACKGROUND: This study evaluated the adhesion and whitening efficacy of a mixture of hydroxyapatite and P11-4 self-assembling peptide (HAP-peptide) on bovine enamel after pre-treatment with low-concentrated sodium hypochlorite (NaOCl). METHODS: Fifty-two caries-free bovine incisors were selected. 50 teeth were randomly allocated to five groups (n = 10). The first group was treated with a mixture of 6.25 wt% HAP and 5 ml P11-4 peptide, using NaOCl 3% as pre-treatment. Second, third and fourth groups were treated with 6.25 wt% HAP, 5 ml P11-4 peptide, and NaOCl 3%, respectively. In the fifth group, only water was applied (control group). The color of samples was measured using a spectrophotometer (USB4000-VIS-NIR-ES, Ostfildern, Germany). To evaluate color changes, ΔE values were statistically analyzed. Finally, adherence of HAP particles on two enamel surfaces with and without pre-treatment with NaOCl was analyzed with SEM. RESULTS: It was observed that the ΔE of the HAP-peptide suspension after pre-treatment with NaOCl was significantly stronger than the control group. In contrast, the overall color changes of separate applications of HAP, peptide, and NaOCl did not differ notably from the control group. SEM observations confirmed that pre-treatment with NaOCl resulted in a more pronounced coverage of HAP on the enamel surface. CONCLUSIONS: Pre-treatment with a low-concentrated NaOCl enhanced the adherence of the HAP layer on the enamel surface, resulting in a stronger whitening effect. TRIAL REGISTRATION: The peptide-HAP suspension is effective in improving tooth whiteness.

Tooth whitening with an experimental toothpaste containing hydroxyapatite nanoparticles.

BACKGROUND: The aim of this study was to evaluate the postbrushing tooth-whitening effect of toothpaste containing hydroxyapatite nanoparticles (nano-HAPs). The impact of the concentration on the whitening performance of nano-HAP toothpaste was also investigated. METHODS: Two concentrations of nano-HAP (10 wt% and 1 wt%) were incorporated in nonabrasive toothpastes. Forty bovine incisors were randomly assigned into four groups: 10 wt% nano-HAP, 1 wt% nano-HAP, toothpaste without nano-HAP as a negative control and water as a blank control. Each tooth was treated with the toothpaste three times and hydrodynamic shear force (HSF) once. The teeth surfaces were observed by SEM after each application. Tooth color (L*, a* and b* values) was measured by a spectrophotometer, and color changes (△E, △L, △a and △b values) were calculated. Two-way mixed ANOVA was performed to evaluate the influence of the concentration and repeated application on the tooth-whitening effect of nano-HAP. RESULTS: We found that nano-HAP-treated enamel exhibited higher L* values and lower a* and b* values than the control groups (P < 0.05). The 10 wt% nano-HAP group showed significantly higher △E values than the 1 wt% nano-HAP group (P < 0.05). After three applications, the △E mean value of the 10 wt% nano-HAP group was 4.47. The △E and △L values were slightly reduced after HSF (P < 0.05). For both nano-HAP groups, HAP single crystallites and agglomerates were identified, and their sizes grew with nano-HAP reapplication. CONCLUSIONS: In conclusion, nano-HAP toothpaste has a satisfying postbrushing whitening effect and good resistance to mechanical forces. The whitening effect seemed to be concentration-dependent.

Adhesion and whitening effects of P11-4 self-assembling peptide and HAP suspension on bovine enamel.

OBJECTIVES: This study evaluated the adhesion and whitening effects of a combination of P11-4 self-assembling peptide and hydroxyapatite (peptide-HAP) on bovine enamel. METHODS: Forty-six caries-free bovine teeth were selected, and 40 teeth were randomly allocated to one of five groups (n = 8). First, the effects of application frequency, exposure time, and storage in saliva on the whitening effects of an experimental low-concentrated peptide-HAP suspension (0.5 wt% HAP; Curodont, Credentis) were evaluated and compared with a commercial bleaching agent (VivaStyle Paint on Plus, VS, Ivoclar Vivadent). Tooth color was measured using a spectrophotometer (Gretag MacBeth), and color changes ΔE were statistically analyzed. Second, the effects of peptide-HAP concentration (low versus high: 6.25% HAP; Curodont Protect), and its interactions with saliva and postapplication restaining, were investigated. Third, enamel surfaces (n = 2) were treated with low concentration peptide-HAP and high-concentration peptide-HAP in polymeric and monomeric forms (Curodont Protect & Curodont Repair, Credentis) and analyzed by SEM. RESULTS: The ΔE of the low-concentration peptide-HAP suspension did not differ from that of VS. Application frequency, exposure time, and storage in saliva did not have any significant impact on whitening efficacy of the peptide-HAP suspension. Increasing the concentration of the suspension did not promote overall ΔE. SEM observations confirmed the presence of the newly generated peptide and HAP on the enamel surface. CONCLUSIONS: The peptide-HAP suspension is a mild tooth whitener, and the adhesion of peptide-HAP to enamel is concentration dependent. CLINICAL RELEVANCE: This peptide-HAP suspension is effective in offsetting discoloration caused by restaining after treatment.

Shrinkage vectors in flowable bulk-fill and conventional composites: bulk versus incremental application.

OBJECTIVES: Sufficient depth of cure allows bulk-fill composites to be placed with a 4-mm thickness. This study investigated bulk versus incremental application methods by visualizing shrinkage vectors in flowable bulk-fill and conventional composites. MATERIALS AND METHODS: Cylindrical cavities (diameter = 6 mm, depth = 4 mm) were prepared in 24 teeth and then etched and bonded with OptiBond FL (Kerr, Italy). The composites were mixed with 2 wt% radiolucent glass beads. In one group, smart dentin replacement (SDR, Dentsply) was applied in bulk "SDR-bulk" (n = 8). In two groups, SDR and Tetric EvoFlow (Ivoclar Vivadent) were applied in two 2-mm-thick increments: "SDR-incremental" and "EvoFlow-incremental." Each material application was scanned with a micro-CT before and after light-curing (40 s, 1100 mW/cm2), and the shrinkage vectors were computed via image segmentation. Thereafter, linear polymerization shrinkage, shrinkage stress and gelation time were measured (n = 10). RESULTS: The greatest shrinkage vectors were found in "SDR-bulk" and "SDR-increment2," and the smallest were found in "SDR-increment1-covered" and "EvoFlow-increment1-covered." Shrinkage away from and toward the cavity floor was greatest in "SDR-bulk" and "EvoFlow-increment2," respectively. The mean values of the shrinkage vectors were significantly different between groups (one-way ANOVA, Tamhane's T2 test, p < 0.05). The linear polymerization shrinkage and shrinkage stress were greatest in Tetric EvoFlow, and the gelation time was greatest in "SDR-bulk." CONCLUSIONS: The bulk application method had greater values of shrinkage vectors and a higher debonding tendency at the cavity floor. CLINICAL RELEVANCE: Incremental application remains the gold standard of composite insertion.

Investigations of the optical properties of enamel and dentin for early caries detection.

INTRODUCTION: The aim of this study was to experimentally investigate the potential of different light wavelengths to distinguish between healthy and carious tissue using a two-circle goniometer. MATERIALS AND METHODS: Tooth slices were prepared from extracted human teeth that were caries free (n = 15) or had occlusal caries lesions (n = 10). The tooth slices were irradiated with diode laser modules of different wavelengths (532, 650, 780 nm). The transmitted and scattered laser light was spatially measured with a detector rotating on a two-circle goniometer. The anisotropy factor and attenuation coefficients were calculated. RESULTS: Enamel was more transparent than dentin and showed wavelength-dependent attenuation. Healthy dentin showed strong light scattering at all wavelengths, independent of the tested wavelength. The calculated attenuation coefficients of carious and healthy tooth tissue differed significantly (p < 0.05; t test). In contrast to healthy enamel, carious enamel showed lower light transmission and an increase in scattering. Differences in the light attenuation of carious versus healthy dentin were less pronounced than those for enamel. Carious dentin was slightly more transparent than healthy dentin. The light of longer wavelengths showed a better penetration of all tooth structures compared with shorter wavelengths. CONCLUSION: Healthy and carious dentin and enamel exhibited distinct optical properties using laser light at different wavelengths. In dentin, changes in the optical properties caused by caries are significantly less pronounced. CLINICAL RELEVANCE: The clear distinction between healthy and carious enamel makes optical caries diagnostic systems ideal tools for early caries detection.

Biomimetic tooth-whitening effect of hydroxyapatite-containing mouthrinses after long-term simulated oral rinsing.

PURPOSE: To investigate the tooth-whitening effects of mouthrinses containing different sizes of hydroxyapatite (HAP) particles after prolonged application time and compare them with a commercial whitening mouthrinse. METHODS: 50 bovine incisors were stained and randomly distributed into five groups: the HAP groups with 3 µm, 200 nm and 50 nm particle size, the commercial whitening mouthrinse group and the distilled water group. The teeth underwent prolonged mouthrinse applications that were equivalent to simulated 3- and 6-month mouthrinsing. Tooth color was measured and calculated before and after mouthrinsing. The group and application time effects were analyzed with a nonparametric analysis of longitudinal data using the nparLD package in R and ANOVA-type statistic was reported. Pairwise Wilcoxon rank-sum tests with BH correction were performed to compare the tooth color changes of individual groups. The mouthrinse-treated enamel was observed by SEM. RESULTS: The whitening effect of HAP mouthrinses after the prolonged application time was confirmed. The HAP mouthrinses exhibited similar whitening effects to the commercial mouthrinses. The particle size and application time could significantly affect the whitening performance of HAP mouthrinses. The 50 nm HAP group exhibited significantly higher ΔE values than the 3 µm group after the 6-month-equivalent application (P= 0.024). A longer period of application increased significantly the ΔE and ΔL values (P< 0.05). The HAP-treated enamel surfaces were entirely covered with HAP after the 6-month-equivalent application. CLINICAL SIGNIFICANCE: The HAP nanoparticles showed better tooth-whitening performance after a longer period of mouthrinsing than the microsized HAP particles. This should be taken into consideration by dental manufacturers for optimizing the particle size for their HAP-containing products. To achieve a better outcome in tooth-whitening, the patients should apply the mouthrinse regularly for an extended period of time.

Near-infrared transillumination with high dynamic range imaging for occlusal caries detection in vitro.

The aim of this study was to assess near-infrared transillumination with high dynamic range imaging (NIRT-HDRI) for occlusal caries detection in vitro and to compare it with visual inspection using the International Caries Detection and Assessment System II (ICDAS) and digital bitewing radiography (BWR). Sixty-one extracted permanent molars with sound or occlusal carious surfaces without severe cavitation were visually assembled. Two examiners assessed twice these surfaces independently using ICDAS, BWR and NIRT-HDRI. The latter was performed with a prototype consisting of two laser sources (780 nm), a CCD sensor and subsequent processing with image analysis software. Thresholds for carious surfaces, enamel and dentin lesions were defined for all methods. Micro-computed tomography served as the reference standard. Linear weighted Kappa analysis of the methods versus the reference at the threshold carious surface, enamel and dentin lesion revealed 0.59/0.08/0.12 for ICDAS, 0.37/- 0.06/0.58 for BWR and 0.33/- 0.01/0.51 for NIRT-HDRI. Sensitivity values at the three thresholds were 0.85/0.78/0.13 for ICDAS, 0.59/0.00/0.69 for BWR and 0.98/0.33/0.78 for NIRT. Specificity values at the three thresholds were 0.70/0.40/1.00 for ICDAS, 0.9./0.96/0.90 for BWR and 0.30/0.65/0.72 for NIRT-HDRI. Reliability analysis revealed substantial agreement for BWR and NIRT and almost perfect agreement for ICDAS. NIRT exhibited a strong ability to identify occlusal dental decay in general; however, it revealed a tendency towards overestimation. Its strength was the detection of dentin caries lesions compared with ICDAS and BWR. NIRT-HDRI seems to be a suitable method to detect hidden dentin caries as a supplement to visual examination.

A detailed report on the measures taken in the Department of Conservative Dentistry and Periodontology in Munich at the beginning of the COVID-19 outbreak.

OBJECTIVES: The corona disease (COVID-19) is developing into one of the greatest challenges for healthcare professionals around the world. In this article, we report the detailed actions taken in the Department of Conservative Dentistry and Periodontology, University Hospital, Ludwig-Maximilians-University (LMU), Munich, Germany, during the early phase of the COVID-19 pandemic. MATERIAL AND METHODS: After a joint on-site inspection of the dental clinic with the Department of Clinical Microbiology and Hospital Hygiene, existing clinical and hygiene protocols were adapted for COVID-19 patients. RESULTS: A comprehensive summary of the preparation of the facilities as well as pre- treatment, treatment and posttreatment protocols are described and arising problems are being discussed. CONCLUSIONS: The importance of rigorous hygiene and treatment protocols as well as a sufficient supply of PPE for dental offices and hospitals is highlighted. The measures reported may be subject to change due to the dynamics of the pandemic. CLINICAL RELEVANCE: The modes of transmission of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) (e.g., droplets, aerosols, and fomites) can pose a risk for dental healthcare professionals and patients alike. The presented measures may guide dental faculties and dental practices during the early stage of the COVID-19 crisis.

In-vitro validation of near-infrared reflection for proximal caries detection.

The aim of this study was the in-vitro validation of VistaCam iX HD, which uses near-infrared reflection (NIRR), for proximal caries detection. It was compared with digital bitewing radiography (BWR), and micro-computed tomography (µCT) was used as the reference standard. One-hundred teeth with either sound (n = 54) or carious (n = 46) proximal surfaces were selected using visual-tactile criteria. Images of these surfaces were generated using BWR and NIRR. Evaluation was performed by two examiners, twice, at an interval of 2 weeks. All samples were scanned with a micro-computed tomograph. Thresholds were defined for sound surfaces, and for enamel and dentin lesions, for all methods. Both BWR and NIRR showed moderate sensitivity for the detection of any caries (0.50 for NIRR and 0.53 for BWR). For enamel lesions, sensitivity was lower (0.13 for NIRR and 0.31 for BWR). Specificity was high (≥0.94) in all categories for both methods. Inter-rater reliability ranged from 0.89 to 0.93 and intra-rater reliability from 0.80 to 0.89. Surface evaluation of images generated using NIRR was complicated by overexposed areas; approximately 25% of the images were not clearly interpretable. In conclusion, NIRR and BWR were found to be reproducible methods with comparable diagnostic accuracy. However, NIRR cannot be recommended as a complementary diagnostic method for assessing proximal caries in permanent molars because of problems with image quality and artefacts.

Effect of fiber incorporation on the contraction stress of composite materials.

OBJECTIVES: This study aimed to assess the effects of fiber incorporation on the contraction stress (CS), time to gelation (TG), and temperature rise (TR) features of two experimental resin-based composites (RBCs) in comparison to those of bulk-fill RBCs and conventional RBCs in simulated, clinically relevant cavities. MATERIALS AND METHODS: CS over 300 s, TG and TR were assessed by a stress-strain analyzer (SSA T80) in two cavity configurations (2 × 4 × 4 mm3/4 × 4 × 4 mm3/configuration value [Formula: see text] and [Formula: see text]) for two experimental RBCs, eight bulk-fill RBCs (EverX Posterior, Filtek Bulk Fill, SDR, SonicFill, Tetric EvoCeram Bulk Fill, Venus Bulk Fill, X-tra base, and X-tra Fill) and one RBC (Filtek Supreme XTE) by light curing (1200 mW/cm2) (n = 10). The experimental materials used were based on EverX Posterior with modifications made to the fiber and filler content. Statistical analyses were performed via ANOVA; multiple pair-wise comparisons were performed via Tukey's test, and homogeneous subsets were identified ("multcomp" package, R). RESULTS: CS values ranged from 1.00 to 4.07 MPa (2 × 4 × 4 mm3) and from 0.97 to 2.49 MPa (4 × 4 × 4 mm3); TG values ranged from 1.31 to 4.05 s (2 × 4 × 4 mm3) and from 1.39 to 3.84 s (4 × 4 × 4 mm3). SDR values showed lowest stress values in both cavity configurations. The experimental composite with fibers presented significantly higher stress values than did the experimental composite without fibers. CONCLUSION: Bulk-fill RBCs showed lower levels of stress than did conventional RBCs. The incorporation of fibers had no positive impact on the CS and TG. CLINICAL RELEVANCE: Appropriate material selection may be essential to clinical success because certain RBCs exhibit higher CS, TG, and TR values.

In vitro validation of near-infrared transillumination at 780 nm for the detection of caries on proximal surfaces.

OBJECTIVES: The aim of the present in vitro study was to determine the ability of Diagnocam to detect caries at an early stage and to compare it with digital radiography. MATERIALS AND METHODS: One hundred twenty proximal surfaces composed equally of sound and decayed surfaces were evaluated by assessing images captured with Diagnocam (Kavo, Biberach, Germany) and digital radiography (DR). All images were assessed twice by two calibrated dentists with a minimum interval of 2 weeks between examinations. The results were compared with µCT scans. RESULTS: Inter-rater reliability showed nearly perfect agreement; a high intra-rater reliability was calculated. Spearman's rank correlation coefficients showed a strong correlation of Diagnocam and µCT (0.82). DR and µCT achieved a slightly lower correlation (0.73). The surfaces were categorized into sound surfaces, enamel lesions, and dentin lesions to determine intraclass correlation coefficients (ICCs), sensitivity and specificity. ICCs between µCT and DR ranged from 0.20 to 0.63. ICCs between Diagnocam and DR were higher in all categories and ranged from 0.56 to 0.83. Sensitivity, specificity, and accuracy of Diagnocam achieved mostly higher values than DR. In detecting enamel lesions, sensitivity was 0.36 for DR and 0.59 for the DC. The areas under the receiver operating characteristic (ROC) curves of Diagnocam were larger than those of DR in all categories. CONCLUSIONS: Diagnocam is more capable of detecting initial proximal lesions than DR and also has a higher sensitivity for dentin lesions. However, caries progression in dentin cannot be reliably determined with Diagnocam. CLINICAL RELEVANCE: Diagnocam may be suitable as a supplement to X-ray diagnostics in clinical use.

Effects of boundary condition on shrinkage vectors of a flowable composite in experimental cavity models made of dental substrates.

OBJECTIVES: Bond strength to enamel and dentin depends on the bonding approach or condition. This study investigated the effects of the boundary conditions, in terms of the bonding substrate and the bonding condition, on the shrinkage vectors of a flowable composite. MATERIALS AND METHODS: An experimental cylindrical cavity (diameter = 6 mm, depth = 3 mm) consisting of the enamel floor and the surrounding dentin cavity walls was prepared for the "enamel-floor" group. Cylindrical cavities of the same dimensions were prepared with access from the occlusal enamel into dentin and served as controls. Each cavity model group was divided and bonded with two bonding conditions (n = 9): a self-etch (Adper Easy Bond, 3M ESPE) and a total-etch approach (OptiBond FL, Kerr). The composite (Tetric EvoFlow, Ivoclar Vivadent) was mixed with glass beads, applied to the cavity, scanned twice by micro-CT (uncured and cured states). The scans were evaluated by rigid registration, sphere segmentation, and registration for computing shrinkage vectors. RESULTS: The free surface of all restorations moved downward. The shrinkage vectors in the experimental cavity model pointed downward towards the enamel cavity floor, and the net axial movement was downward. In the control group, shrinkage vectors additionally moved upward, away from the cavity floor. The effect of the bonding substrate and the bonding condition was investigated for the shrinkage vectors and the axial movement (univariate ANOVA). CONCLUSION: The bonding substrate, enamel, influenced the shrinkage vectors' direction, while the bonding condition caused only variations in the magnitude. CLINICAL RELEVANCE: Bonding to enamel influences shrinkage vectors' direction, while the bonding condition plays only a minor role. Graphical abstract ᅟ.

Immobilization of Denosumab on Titanium Affects Osteoclastogenesis of Human Peripheral Blood Monocytes.

Immobilization of proteins has been examined to improve implant surfaces. In this study, titanium surfaces were modified with nanofunctionalized denosumab (cDMAB), a human monoclonal anti-RANKL IgG. Noncoding DNA oligonucleotides (ODN) served as linker molecules between titanium and DMAB. Binding and release experiments demonstrated a high binding capacity of cDMAB and continuous release. Human peripheral mononuclear blood cells (PBMCs) were cultured in the presence of RANKL/MCSF for 28 days and differentiated into osteoclasts. Adding soluble DMAB to the medium inhibited osteoclast differentiation. On nanofunctionalized titanium specimens, the osteoclast-specific TRAP5b protein was monitored and showed a significantly decreased amount on cDMAB-titanium in PBMCs + RANKL/MCSF. PBMCs on cDMAB-titanium also changed SEM cell morphology. In conclusion, the results indicate that cDMAB reduces osteoclast formation and has the potential to reduce osteoclastogenesis on titanium surfaces.

Effects of occlusal cavity configuration on 3D shrinkage vectors in a flowable composite.

OBJECTIVE: The objective of this study was to investigate the effects of cavity configuration on the shrinkage vectors of a flowable resin-based composite (RBC) placed in occlusal cavities. MATERIALS AND METHODS: Twenty-seven human molars were divided into three groups (n = 9) according to cavity configuration: "adhesive," "diverging," and "cylindrical." The "adhesive" cavity represented beveled enamel margins and occlusally converging walls, the "diverging" cavity had occlusally diverging walls, and the "cylindrical" cavity had parallel walls (diameter = 6 mm); all cavities were 3 mm deep. Each prepared cavity was treated with a self-etch adhesive (Adper Easy Bond, 3 M ESPE) and filled with a flowable RBC (Tetric EvoFlow, Ivoclar Vivadent) to which had been added 2 wt% traceable glass beads. Two micro-CT scans were performed on each sample (uncured and cured). The scans were then subjected to medical image registration for shrinkage vector calculation. Shrinkage vectors were evaluated three-dimensionally (3D) and in the axial direction. RESULTS: The "adhesive" group had the greatest mean 3D shrinkage vector lengths and upward movement (31.1 ± 10.9 µm; - 13.7 ± 12.1 µm), followed by the "diverging" (27.4 ± 12.1 µm; - 5.7 ± 17.2 µm) and "cylindrical" groups (23.3 ± 11.1 µm; - 3.7 ± 13.6 µm); all groups differed significantly (p < 0.001 for each comparison, one-way ANOVA, Tamhane's T2). CONCLUSION: The values and direction of the shrinkage vectors as well as interfacial debonding varied according to the cavity configuration. CLINICAL RELEVANCE: Cavity configuration in terms of wall orientation and beveling of enamel margin influences the shrinkage pattern of composites.

Hydroxyapatite and Self-Assembling Peptide Matrix for Non-Oxidizing Tooth Whitening.

OBJECTIVES: The aim of this combined in vitro and in vivo study was to evaluate the efficacy of tooth whitening using a mixture of Self- Assembling Peptide Matrix (SAPM) and hydroxyapatite (HA). METHODS: The mixture was applied on stained bovine teeth, and the tooth color was measured using a spectrophotometer; mean changes in L*a*b values between measurements were expressed as DE. Additionally, the nature of the surface layer was investigated by ATRFTIR and EDX. The optical changes due to the additional surface layer were measured using a goniometer. Finally, a proof-of-concept clinical study was performed investigating the mixture of SAPM+HA. RESULTS: The results verified that the SAPM remained on the tooth surface and acted as a temporary adhesive to attach the HA particles to the tooth surface. Further, the optical changes due to the additional surface layer indicated a diffuse reflection to be the origin of the optical whitening. Lastly, the mixture of SAPM+HA showed significant and visible whitening after one application, increasing throughout the first week of home application (DE = 4.9 ± 3.3) and remaining stable for 30 days (DE = 4.8 ± 3.6). CONCLUSIONS: The combination of SAPM+HA particles caused optical whitening based on diffuse reflection by the HA particles on the tooth surface. The whitening effect and its magnitude observed in vitro were also seen in vivo.

Surface properties and color stability of incrementally-filled and bulk-fill composites after in vitro toothbrushing.

PURPOSE: To evaluate the effect of simulated toothbrush abrasion on the surface gloss, the surface roughness and the color stability of incrementally-filled and bulk-fill composites. METHODS: 48 dimensionally standardized composite specimens (n= 8/group) were made from four incrementally-filled composites (Tetric EvoCeram, IPS Empress Direct Enamel, Ceram X mono and Arabesk) and two bulk-fill composites (Quix fil and Tetric EvoCeram Bulk). Before and after toothbrushing simulation the surface gloss was measured by a glossmeter, the surface roughness was evaluated with a profilometer, and the color was measured using a spectrophotometer. RESULTS: Before and after the toothbrush abrasion, IPS Empress Direct Enamel yielded the highest gloss value, while Ceram X mono exhibited the lowest gloss value. Quix fil showed the highest Ra value before the toothbrushing simulation, however, it showed similar Ra value with Ceram X mono and Arabesk after the toothbrushing simulation. IPS Empress Direct Enamel showed the lowest ΔE after the simulated toothbrushing. Tetric EvoCeram Bulk showed similar gloss value, Ra value, and ΔE to Tetric EvoCeram after the toothbrushing simulation. Simple regression analysis showed no correlation between the roughness and the gloss, but it showed a positive linear relationship between ΔE and ΔRa. (R2= 0.863, P= 0.027). CLINICAL SIGNIFICANCE: The evaluated bulk-fill composites did not exhibit significantly worse surface properties and color stability than incrementally-filled materials after toothbrush abrasion. Color changes of composites caused by toothbrush abrasion were acceptable on the premise that 3.3ΔE units were considered as acceptable threshold values.

Polishing mechanism of light-initiated dental composite: Geometric optics approach.

BACKGROUND/PURPOSE: For light-initiated dental hybrid composites, reinforcing particles are much stiffer than the matrix, which makes the surface rugged after inadequate polish and favors bacterial adhesion and biofilm redevelopment. The aim of the study was to investigate the polishing mechanism via the geometric optics approach. METHODS: We defined the polishing abilities of six instruments using the obtained gloss values through the geometric optics approach (micro-Tri-gloss with 20°, 60°, and 85° measurement angles). The surface texture was validated using a field emission scanning electron microscope (FE-SEM). Based on the gloss values, we sorted polishing tools into three abrasive levels, and proposed polishing sequences to test the hypothesis that similar abrasive levels would leave equivalent gloss levels on dental composites. RESULTS: The three proposed, tested polishing sequences included: S1, Sof-Lex XT coarse disc, Sof-Lex XT fine disc, and OccluBrush; S2, Sof-Lex XT coarse disc, Prisma Gloss polishing paste, and OccluBrush; and S3, Sof-Lex XT coarse disc, Enhance finishing cups, and OccluBrush. S1 demonstrated significantly higher surface gloss than the other procedures (p < 0.05). The surface textures (FE-SEM micrographs) correlated well with the obtained gloss values. CONCLUSION: Nominally similar abrasive abilities did not result in equivalent polish levels, indicating that the polishing tools must be evaluated and cannot be judged based on their compositions or abrasive sizes. The geometric optic approach is an efficient and nondestructive method to characterize the polished surface of dental composites.

Do bonding agents protect the bracket-periphery?--Evaluation by consecutive µCT scans and fluorescence measurements.

OBJECTIVES: The aim of this in vitro study was to consecutively determine the effect of three bonding agents on the prevention of enamel demineralisation at the bracket-periphery and to compare the suitability of micro-computed tomography (µCT) scans and quantitative light-induced fluorescence (QLF) to detect changes within subsurface lesions. MATERIALS AND METHODS: The effect of a resin-modified glass ionomer cement (RMGI) (Fuji Ortho LC), a compomer (Assure) and a composite (Transbond XT) on the prevention of enamel demineralisation at the bracket-periphery was examined. After 7, 14, 21 and 28 days of pH cycling, the teeth (N = 45) were examined by consecutive µCT scans and by using a customised QLF set-up. RESULTS: Particularly for the RMGI and for the compomer, the QLF and µCT scans showed that the formation and the body of the lesion were not precisely located at the enamel next to the bracket margin. There was an area that was almost protected. The progression of demineralisation was decreased for the RMGI and the compomer-treated teeth. CONCLUSION: For bonding orthodontic brackets, the RMGI and compomer were comparably able to decrease the progression of white spot lesions (WSL), although the RMGI showed marginally superior protection. Both methods (QLF and µCT scans) were suitable for investigating the longitudinal fluoride effects on WSL, though these effects were more accurately described by mineral (fluorescence) loss or volume changes than by lesion depth. CLINICAL RELEVANCE: The progression of WSL at the bracket-periphery could be altered by using fluoride-releasing bonding agents for bracket application. This approach represents a minimally invasive preventive measure.