Evaluation of mineral content in healthy permanent human enamel by Raman spectroscopy

Background

An understanding of tooth enamel mineral content using a clinically viable method is essential since variations in mineralization may serve as an early precursor of a dental health issues, and may predict progression and architecture of decay in addition to assessing the success and effectiveness of the remineralization strategies.

Material and Methods

Twenty two human incisor teeth were obtained in compliance with the NIH guidelines and site specifically imaged with Raman microscope. The front portion of the teeth was divided into apical, medium and cervical regions and subsequently imaged with Raman microscope in these three locations.

Results

Measured mineralization levels have varied substantially depending on the regions. It was also observed that, the cervical enamel is the least mineralization as a populational average.

Conclusions

Enamel mineralization is affected by a many factors such as are poor oral hygiene, alcohol consumption and high intake of dietary carbohydrates, however the net effect manifests as overall mineral content of the enamel. Thus an early identification of the individual with overall low mineral content of the enamel may be a valuable screening tool in determining a group with much higher than average caries risk, allowing intervention before development of caries. Clinically applicable non-invasive techniques that can quantify mineral content, such as Raman analysis, would help answer whether or not mineralization is associated with caries risk.

Key words:Enamel, Raman spectroscopy, mineral content, dental caries.

Mechanical properties and DIC analyses of CAD/CAM materials

Background

This study compared two well-known computer-aided-design/computer-aided-manufactured (CAD/CAM) blocks (Paradigm MZ100 [3M ESPE] and Vitablocs Mark II [Vita] in terms of fracture toughness (Kic), index of brittleness (BI) and stress/strain distributions.

Material and Methods

Three-point bending test was used to calculate the fracture toughness, and the relationship between the Kic and the Vickers hardness was used to calculate the index of brittleness. Additionally, digital image correlation (DIC) was used to analyze the stress/strain distribution on both materials.

Results

The values for fracture toughness obtained under three-point bending were 1.87Pa√m (±0.69) for Paradigm MZ100 and 1.18Pa√m (±0.17) for Vitablocs Mark II. For the index of brittleness, the values for Paradigm and Vitablocs were 73.13μm-1/2 (±30.72) and 550.22μm-1/2 (±82.46). One-way ANOVA was performed to find differences (α=0.05) and detected deviation between the stress/strain distributions on both materials.

Conclusions

Both CAD/CAM materials tested presented similar fracture toughness, but, different strain/stress distributions. Both materials may perform similarly when used in CAD/CAM restorations.

Key words:Ceramic, CAD/CAM, hybrid materials, composite resin, fracture toughness.

Microtensile bond strength between a UDMA fiber post and different resin cements: Effect of pre-surface treatment

During a fiber post cementation, bonding failure often occurs at the junction between the fiber-post and resin-cement. Because this failure requires better characterization, we evaluated if different post surface treatment can affect the bond strength of urethane dimethacrylate (UDMA) fiber-posts with resin-cements. Three groups were created: G1: no treatment/silane; G2: ethyl alcohol (96° GL)/silane; G3: 24% H₂O₂/silane and further divided into four subgroups: I-Unicem/3MESPE; II-BisCem/Bisco; III-Panavia SA/Kuraray and IV-DuoLink/Bisco. Blocks of cured resin cements and posts placed in the center were serially cut into bar-shaped specimens and loaded into a micro tensile testing machine. ANOVA indicated no significant differences among post surface treatments (p>0.05), however, significant within the resin cements (p<0.05) and the interaction of both (p<0.05). The G3/IV showed the highest bond strength values. SEM showed that surface treatments on UDMA fiber posts presented no benefits in terms of surface roughness, thus, should not be performed.

Are different generations of CAD/CAM milling machines capable to produce restorations with similar quality?

BACKGROUND

Different CAD/CAM machines' generation may impact the restoration overall quality. The present study evaluated the marginal fit of CAD/CAM restorations manufactured with different generations of CEREC milling unit systems.

MATERIAL AND METHODS

Sixteen typodont teeth were divided into two groups (n=8) according to the machine's generation assigned. These are control group (G1): Cerec AC with Bluecam/Cerec 3 milling unit and (G2): Cerec AC with Bluecam/MC XL Premium Package milling unit. Scanning of the preparation were performed and crowns were milled using the Vita Mark II blocks. Blocks were cemented using epoxy glue on the pulpal floor only and finger pressure applied for 1 min. Upon completion of the cementation step, misfits between the restoration and abutment were measured by microphotography and the silicone replica technique using light body silicon material on Mesial (M) and Distal (D) surfaces.

RESULTS

Mean and SDs of marginal gaps in micrometers were: G1/M: 94.90 (±38.52), G1/D: 88.53 (±44.87), G2/M: 85.65 (±29.89), G2/D: 95.28 (±28.13). Two-way ANOVA indicated no significant differences among different groups (P>0.05); surface area (P>0.05) and the interaction (P>0.05). Overall, G2 had greater margin gaps than G1, however, without statistical difference (P>0.05).

CONCLUSIONS

Difference in milling unit generation did not significantly affect the marginal fit. Marginal gap means were in the range of the clinical acceptance levels for both generations of Cerec milling units, regardless the teeth site area. Key words:CAD/CAM, margin, ceramics.

Improving the value of clinical research through the use of Common Data Elements

The use of Common Data Elements can facilitate cross-study comparisons, data aggregation, and meta-analyses; simplify training and operations; improve overall efficiency; promote interoperability between different systems; and improve the quality of data collection. A Common Data Element is a combination of a precisely defined question (variable) paired with a specified set of responses to the question that is common to multiple datasets or used across different studies. Common Data Elements, especially when they conform to accepted standards, are identified by research communities from variable sets currently in use or are newly developed to address a designated data need. There are no formal international specifications governing the construction or use of Common Data Elements. Consequently, Common Data Elements tend to be made available by research communities on an empiric basis. Some limitations of Common Data Elements are that there may still be differences across studies in the interpretation and implementation of the Common Data Elements, variable validity in different populations, and inhibition by some existing research practices and the use of legacy data systems. Current National Institutes of Health efforts to support Common Data Element use are linked to the strengthening of National Institutes of Health Data Sharing policies and the investments in data repositories. Initiatives include cross-domain and domain-specific resources, construction of a Common Data Element Portal, and establishment of trans-National Institutes of Health working groups to address technical and implementation topics. The National Institutes of Health is seeking to lower the barriers to Common Data Element use through greater awareness and encourage the culture change necessary for their uptake and use. As National Institutes of Health, other agencies, professional societies, patient registries, and advocacy groups continue efforts to develop and promote the responsible use of Common Data Elements, particularly if linked to accepted data standards and terminologies, continued engagement with and feedback from the research community will remain important.

Investigation of Intra- and Inter-individual Variations of Mineralisation in Healthy Permanent Human Enamel by Raman Spectroscopy

PURPOSE

To systematically examine mineralisation of healthy human enamel using Raman spectroscopy and provide an understanding of baseline variations that may be inherent in the healthy enamel from individual to individual as well as variations within a tooth.

MATERIALS AND METHODS

Human teeth were obtained in compliance with the NIH guidelines. The teeth were collected fresh within the date of the extraction and kept moist at all times with wet tissue paper without any additional disinfecting treatment. The samples were individually wrapped in wet tissue paper and stored in a -20°C freezer. Prior to Raman analysis, the specimens were thawed at room temperature for 30 min. A Raman microscope was employed with a 10X objective used to focus the laser light (785 nm). Raman spectroscopy scores were validated by microcomputed tomography (μCT) on the two teeth which had the highest and lowest mineralisation found in the Raman scans.

RESULTS

Mineralisation levels varied substantially between individuals. The highest Raman-based mineralisation intensity was about 5-fold greater than the lowest mineralisation score. Incisor mineralisation also varied dramatically depending on different sites on the tooth.

CONCLUSIONS

Clinically applicable non-invasive techniques such as Raman spectroscopy that can quantify mineral content, such as Raman spectroscopy, may help answer whether or not mineralisation is associated with caries risk.

[Field investigation of occupational disease diagnosis in Guangdong Provincial Hospital for Occupational Disease Prevention and Treatment from 2009 to 2014: an analysis of 136 cases]

OBJECTIVE

To investigate the characteristics of 136 patients with occupational diseases, to summarize key techniques used in field investigation, and to provide a scientific basis for the development of standard operating procedures for field investigation of occupational disease diagnosis.

METHODS

Field investigation and routine data analysis were performed to analyze the cases diagnosed by Guangdong Provincial Hospital for Occupational Disease Prevention and Treatment from January 2009 to December 2014.

RESULTS

A total of 136 cases of occupational diseases were diagnosed by Guangdong Provincial Hospital for Occupational Disease Prevention and Treatment from 2009 to 2014, and there were 66 cases of leukemia, 18 cases of suspected occupational benzene poisoning, 12 cases of suspected occupational handarm vibration disease, and 11 cases of suspected pneumoconiosis. Of all these patients, 41.91% were engaged in at least three types of work, 70.59% were exposed to at least three types of chemicals, 25.74% experienced changes in technical processes and chemicals, and 47.06% had disputes on the chemicals they were exposed to during verification by both parties. Occupational hazard factors were detected. Most samples (358)were used to measure benzene concentration in workplace air, among which 11.7% had a benzene concentration of >6.00 mg/m(3)(exceeding standard), 13.41% had a benzene concentration of 3.26~6.00 mg/m(3), 75.42% had a benzene concentration of<0.03 to <3.25 mg/m(3). The samples of suspected occupational hand-arm vibration disease, suspected pneumoconiosis, and suspected occupational noiseinduced hearing loss had high overstandard rates (100%, 93.8%, and 83.3%, respectively).

CONCLUSION

Field investigation of occupational disease diagnosis reveals large numbers of cases of leukemia, suspected occupational benzene poisoning, suspected occupational hand-arm vibration disease, and suspected pneumoconiosis. The key aspects of field investigation include confirmation of the history of occupational exposure, identification of occupational hazard factors, confirmation of the changes in technical processes and chemicals, detection of occupational hazard factors, sampling and analysis of raw materials, and epidemiological investigation of workers with the same type of work.

Effect of different adhesive strategies on microtensile bond strength of computer aided design/computer aided manufacturing blocks bonded to dentin

Background:

The aim of this study was to determine the microtensile bond strength (μTBS) of ceramic and composite computer aided design-computer aided manufacturing (CAD-CAM) blocks bonded to dentin using different adhesive strategies.

Materials and Methods:

In this in vitro study, 30 crowns of sound freshly extracted human molars were sectioned horizontally 3 mm above the cementoenamel junction to produce flat dentin surfaces. Ceramic and composite CAD/CAM blocks, size 14, were sectioned into slices of 3 mm thick. Before bonding, CAD/CAM block surfaces were treated according to the manufacturer's instructions. Groups were created based on the adhesive strategy used: Group 1 (GI) - conventional resin cement + total-etch adhesive system, Group 2 (GII) - conventional resin cement + self-etch adhesive system, and Group 3 (GIII) - self-adhesive resin cement with no adhesive. Bonded specimens were stored in 100% humidity for 24h at 37΀C, and then sectioned with a slow-speed diamond saw to obtain 1 mm × 1 mm × 6 mm microsticks. Microtensile testing was then conducted using a microtensile tester. μTBS values were expressed in MPa and analyzed by one-way ANOVA with post hoc (Tukey) test at the 5% significance level.

Results:

Mean values and standard deviations of μTBS (MPa) were 17.68 (±2.71) for GI/ceramic; 17.62 (±3.99) for GI/composite; 13.61 (±6.92) for GII/composite; 12.22 (±4.24) for GII/ceramic; 7.47 (±2.29) for GIII/composite; and 6.48 (±3.10) for GIII/ceramic; ANOVA indicated significant differences among the adhesive modality and block interaction (P < 0.05), and no significant differences among blocks only, except between GI and GII/ceramic. Bond strength of GIII was consistently lower (P < 0.05) than GI and GII groups, regardless the block used.

Conclusion:

Cementation of CAD/CAM restorations, either composite or ceramic, can be significantly affected by different adhesive strategies used.

Dental Students' Learning Experiences and Preferences Regarding Orofacial Pain: A Cross-Sectional Study

Pain is a global health problem, the effects of which range from diminished quality of life to pain management costs and loss of work and productivity. Pain in the head and neck region is defined as a separate entity: orofacial pain (OFP). However, some graduates from dental schools have reported feeling less competent in their ability to diagnose OFP than in other areas of dentistry. The aims of this study were to assess how students at one U.S. dental school had learned about OFP and to identify the teaching methods and venues they would like to see enhanced in the school's OFP curriculum. A cross-sectional four-question survey was administered to 140 dental students in their third and fourth years; the survey had a response rate of 53%. Most students reported having gained their OFP knowledge mainly in dental school, and 91.9% selected didactic courses as the main teaching method in which they had learned about this topic. Clinical education was the main teaching venue these students said they would like to see enhanced in order to gain more knowledge in most forms of OFP; this result aligned with their learning preferences in general. These findings may help dental schools design their OFP curricula to take account of students' preferences as well as practical limitations regarding availability of clinical experiences.

Dental Students' Use of AMSTAR to Critically Appraise Systematic Reviews

The idea of basing clinical procedures upon evidence gathered by observation is less than 200 years old, with the first set of evidence-based position papers dating back only to the early 1970s. The relationship between evidence-based education and health outcomes is difficult to test and may be indirect, but teaching critical appraisal skills may be beneficial in developing knowledge. Systematic reviews have a central role in the process of clinical decision making in practice and therefore should be of high quality, following a rigorous protocol that can be evaluated with validated tools. The aim of this study was to assess how dental students utilized the Assessment of Multiple Systematic Reviews (AMSTAR) appraisal tool to evaluate systematic reviews in the context of a treatment planning course. During the in-class final exam, students were required to appraise the quality of a systematic review and to justify their answers. Of the 74 third-year students who took the exam, 100% answered all questions on the AMSTAR form. The mean number of correct answers was nine (SD=1.047, Min=6, Max=10), with no student providing all 11 correct answers. The fact that nearly 90% of the students provided eight or more correct answers suggests that AMSTAR can be used by students to evaluate the methodological quality of systematic reviews. It also was evident that although the AMSTAR tool requires less than 15 minutes to complete an evaluation, using it requires extensive training and repetition to achieve consistent and reliable results.

Wide-field Raman imaging of dental lesions

Detection of dental caries at the onset remains as a great challenge in dentistry. Raman spectroscopy could be successfully applied towards detecting caries since it is sensitive to the amount of Raman active mineral crystals, the most abundant component of enamel. Effective diagnosis requires full examination of a tooth surface via Raman mapping. Point-scan Raman mapping is not clinically relevant (feasible) due to lengthy data acquisition time. In this work, a wide-field Raman imaging system was assembled based on a high-sensitivity 2D CCD camera for imaging the mineralization status of teeth with lesions. Wide-field images indicated some lesions to be hypomineralized and others to be hypermineralized. The observations of wide-field Raman imaging were in agreement with point-scan Raman mapping. Therefore, sound enamel and lesions can be discriminated by Raman imaging of the mineral content. In conclusion, wide-field Raman imaging is a potentially useful tool for visualization of dental lesions in the clinic.

Pruning the ALS-associated protein SOD1 for in-cell NMR

To efficiently deliver isotope-labeled proteins into mammalian cells poses a main challenge for structural and functional analysis by in-cell NMR. In this study we have employed cell-penetrating peptides (CPPs) to deliver the ALS-associated protein superoxide dismutase (SOD1) into HeLa cells. Our results show that, although full-length SOD1 cannot be efficiently internalized, a variant in which the active-site loops IV and VII have been truncated (SOD1(ΔIVΔVII)) yields high cytosolic delivery. The reason for the enhanced delivery of SOD1(ΔIVΔVII) seems to be the elimination of negatively charged side chains, which alters the net charge of the CPP-SOD1 complex from neutral to +4. The internalized SOD1(ΔIVΔVII) protein displays high-resolution in-cell NMR spectra similar to, but not identical to, those of the lysate of the cells. Spectral differences are found mainly in the dynamic β strands 4, 5, and 7, triggered by partial protonation of the His moieties of the Cu-binding site. Accordingly, SOD1(ΔIVΔVII) doubles here as an internal pH probe, revealing cytosolic acidification under the experimental treatment. Taken together, these observations show that CPP delivery, albeit inefficient at first trials, can be tuned by protein engineering to allow atomic-resolution NMR studies of specific protein structures that have evaded other in-cell NMR approaches: in this case, the structurally elusive apoSOD1 barrel implicated as precursor for misfolding in ALS.