Effect of Deep Margin Elevation on CAD/CAM-Fabricated Ceramic Inlays

CLINICAL RELEVANCE

Using the deep margin elevation technique in preparations extending beyond the cemento-enamel junction appears to be beneficial in maintaining structural integrity of CAD/CAM-fabricated feldspathic ceramic inlays.

SUMMARY

Objective: To evaluate the effect of deep margin elevation on structural and marginal integrity of ceramic inlays.Methods and Materials: Forty extracted human third molars were collected and randomly separated into four groups (n=10/group). In group 1 (enamel margin group), the gingival margin was placed 1 mm supragingival to the cemento-enamel junction (CEJ). In group 2 (cementum margin group), the gingival margin was placed 2 mm below the CEJ. In group 3 (glass ionomer [GI] margin group), the gingival margin was placed 2 mm below the CEJ, and then the margin elevated with GI to the CEJ. In group 4 (resin-modified glass ionomer [RMGI] margin group), the gingival margin was placed 2 mm below the CEJ, and then the margin elevated with RMGI to the CEJ. Standardized ceramic class II inlays were fabricated with computer-aided design/computer-aided manufacturing and bonded to all teeth, and ceramic proximal box heights were measured. All teeth were subjected to 10,000 cycles of thermocycling (5°C/55°C) and then underwent 1,200,000 cycles of vertical chewing simulation at 50 N of force. Ceramic restorations and marginal integrity were assessed with a Hirox digital microscope. The Fisher exact test (two-tailed) with adjusted p-values (α=0.05) and logistic regression were used for statistical analysis.Results: The cementum margin group had a significantly higher ceramic fracture rate (90%) compared to other groups (10% in enamel margin and GI margin groups, p=0.007; 0% in RMGI group, p<0.001). Logistic regression showed that with increased ceramic proximal box heights, the probability of ceramic fracture increased dramatically.Conclusion: Deep marginal elevation resulted in decreased ceramic fracture when preparation margins were located below the CEJ. There was no difference found between margin elevation with GI or RMGI. Increased heights of ceramic proximal box may lead to an increased probability of ceramic fracture.

Lead and Mercury Exposure and Related Health Problems in Metal Artisan Workplaces and High-Risk Household Contacts in Thimphu, Bhutan

Background

Metal artisans have been using lead and mercury in their settings for centuries. Exposure to these toxic heavy metals causes adverse health effects. We assessed the occupational exposure of metal artisans and their high-risk household contacts at Thimphu, Bhutan.

Methods

A cross-sectional study in which 134 metal artisan center employees and 48 high-risk household contacts were tested for blood lead and mercury levels. Sociodemographic data, occupational exposure risk factors, and clinical syndrome related to lead and mercury exposure were further obtained and analyzed using EpiInfo 7.0.

Results

The mean age of the metal artisan center employees was 36.02 ± 10.3. The prevalence of elevated blood lead and mercury level was 38.4% and 51.9%, respectively. Significantly higher prevalence of mercury level was observed among the artisans compared to nonartisans (66.97 vs, 16.0). Among three centers, the goldsmith section of the Department of National Properties had the highest (94.1%). Profession as an artisan, mold designing, performing gold amalgamation, working for >8 hours a day, working for >5 years, and working at home were significant risk factors associated with elevated blood mercury level. Significant association was observed between elevated mercury level and complaints of burning or watery eyes (p=0.001), anxiety, nervousness, irritability, severe shyness (p=0.001), anxiety, nervousness, irritability, severe shyness (p=0.001), anxiety, nervousness, irritability, severe shyness (p=0.001), anxiety, nervousness, irritability, severe shyness (p=0.029), muscle aches (p=0.019), and stomach cramps or pain (p=0.009).

Conclusion

The prevalence of elevated blood mercury level is concerning among the artisans. Advocacy, proper usage of personal protective equipment, awareness on chemical safety, and hazard associated with lead and mercury usage are needed to minimize the exposure.

Difference assessment of composite resins and sound tooth applicable in the resin-imbedded tooth for resin repair using fluorescence, microhardness, DIAGNOdent, and X-ray image

OBJECTIVE

Visual differentiation of resin and tooth in a tooth cavity is not simple due to their highly similar shade. The purpose of the present study was to find any noninvasive method which can effectively differentiate resin from sound tooth in a resin-imbedded tooth for resin repair.

MATERIALS AND METHODS

For the study, various resin products were imbedded into the cavity of sound tooth. By applying laser of different wavelengths, autofluorescence (AF) of sound tooth and resin products were obtained. Microhardness, X-ray radiograph, and DIAGNOdent were tested for each tooth, resin product, and resin-imbedded tooth.

RESULTS

For the AF spectra obtained using the 405-nm wavelength, sound tooth has emission peak at 440-470 nm and near 490 nm. Sound tooth has several times higher microhardness than resin products regardless of position in tooth subsurface. Due to the difference of radiopaque fillers' composition and concentration, resin products have different brightness in the X-ray radiograph. DIAGNOdent readings for tooth and resin products were inconsistently different, and the difference of obtained values was slightly not to be applicable for the differentiation.

CONCLUSION

Among the tested methods, with noninvasive treatment, AF spectrum by the 405-nm wavelength showed the apparent difference between resin and tooth.

CLINICAL SIGNIFICANCE

For the resin repair in a resin-imbedded tooth cavity, AF spectrum produced by 405-nm wavelength could be a useful method in tracing the resin-tooth boundary if combined with conventional X-ray radiography.

Mercury concentrations in urine of amerindian populations near oil fields in the peruvian and ecuadorian amazon

BACKGROUND

Mercury is a global contaminant with toxic, persistent effects on human health. Petroleum extraction is an important source of elemental mercury; little is known about human exposure levels near oil fields in the Amazon basin.

OBJECTIVES

To characterize mercury levels in people living near oil production sites in the Peruvian and Ecuadorian Amazon, controlling for fish consumption, occupation, source of water and socio-demographic characteristics.

METHODS

Analyze mercury levels in urine samples using cold vapour atomic fluorescence spectrometry from 76 indigenous men and women in eight riverine communities situated near oil wells or pipelines. Subjects answered a questionnaire soliciting socio-demographic, occupational and dietary information. Data were analyzed using multiple linear regression modeling.

RESULTS

The mean value of U-Hg was 2.61μg/g creatinine (95% CI: 2.14-3.08), with 7% of the sample recording values above the global background standard suggested by The World Health Organization (5μg/g creatinine). Women who used water from a surface source had two and a half times the amount of mercury in their urine (mean=3.70μg/g creatinine, 95% CI: 2.26-5.15) compared with women who used other water sources (mean =1.39μg/g creatinine, 95% CI: 0.51-2.25). Men who were involved in an oil clean-up operation had twice as much mercury in their urine (mean =3.07μg/g creatinine, 95% CI: 1.97-4.16) as did those who worked on other tasks (mean =1.56μg/g creatinine, 95% CI: 1.48-2.65). Mercury levels were not associated with the number of fish meals per week.

CONCLUSIONS

Indigenous peoples of the Peruvian and Ecuadorian Amazon living near oil production sites generally had urine mercury levels within the global background standard suggested by the World Health Organization. Increased levels of mercury in urine were detected for men involved in oil spill remediation and for women who relied on surface water for household needs. These findings signal the need for strict safety measures to limit the amount of oil entering the waterways in Andean Amazonia so as to protect the health of indigenous people.

Does the adhesive strategy influence the post-operative sensitivity in adult patients with posterior resin composite restorations?: A systematic review and meta-analysis

OBJECTIVES

A systematic review and meta-analysis were performed on the risk and intensity of postoperative sensitivity (POS) in posterior resin composite restorations bonded with self-etch (SE) and etch-and-rinse (ER) adhesives.

SOURCE

A comprehensive search was performed in the MEDLINE via PubMeb, Scopus, Web of Science, LILACS, BBO and Cochrane Library and SIGLE without restrictions. The abstracts of the annual conference of the IADR (1990-2014), unpublished and ongoing trials registry were also searched. Dissertations and theses were searched using the ProQuest Dissertations and Periodicos Capes Theses databases.

STUDY SELECTION

We included randomized clinical trials that compared the clinical effectiveness of SE and ER used for direct resin composite restorations in permanent dentition of adult patients. The risk/intensity of POS was the primary outcome. The risk of bias tool of the Cochrane Collaboration was used. The meta-analysis was performed on the studies considered 'low' risk of bias.

DATA

After duplicates removal, 2600 articles were identified but only 29 remained in the qualitative synthesis. Five were considered to be 'high' risk of bias and eleven were considered to be 'unclear' in the key domains, yielding 13 studies for meta-analysis. The overall relative risk of the spontaneous POS was 0.63 (95% CI 0.35 to 1.15), while the stimuli-induced POS was 0.99 (95% CI 0.63 to 1.56). The overall standardized mean difference was 0.08 (95%CI -0.19 to 0.35). No overall effect was revealed in the meta-analyses, meaning that no influence of the ER or SE strategy on POS.

SIGNIFICANCE

The type of adhesive strategy (ER or SE) for posterior resin composite restorations does not influence the risk and intensity of POS. CRD42014006617.

Longitudinal analysis of the association between removal of dental amalgam, urine mercury and 14 self-reported health symptoms

BACKGROUND

Mercury vapor poses a known health risk with no clearly established safe level of exposure. Consequently there is debate over whether the level of prolonged exposure to mercury vapor from dental amalgam fillings, combining approximately 50% mercury with other metals, is sufficiently high to represent a risk to health. The objective of our study is to determine if mercury exposure from amalgam fillings is associated with risk of adverse health effects.

METHODS

In a large longitudinal non-blind sample of participants from a preventative health program in Calgary, Canada we compared number of amalgam fillings, urine mercury measures and changes in 14 self-reported health symptoms, proposed to be mercury dependent sub-clinical measures of mental and physical health. The likelihood of change over one year in a sample of persons who had their fillings removed was compared to a sample of persons who had not had their fillings removed. We use non-parametric statistical tests to determine if differences in urine mercury were statistically significant between sample groups. Logistic regression models were used to estimate the likelihood of observing symptom improvement or worsening in the sample groups.

RESULTS

At baseline, individuals with dental amalgam fillings have double the measured urine mercury compared to a control group of persons who have never had amalgam fillings. Removal of amalgam fillings decreases measured urine mercury to levels in persons without amalgam fillings. Although urine mercury levels in our sample are considered by Health Canada to be too low to pose health risks, removal of amalgam fillings reduced the likelihood of self-reported symptom deterioration and increased the likelihood of symptom improvement in comparison to people who retained their amalgam fillings.

CONCLUSIONS

Our findings suggest that mercury exposure from amalgam fillings adversely impact health and therefore are a health risk. The use of safer alternative materials for dental fillings should be encouraged to avoid the increased risk of health deterioration associated with unnecessary exposure to mercury.

The decision to repair or replace a defective restoration is affected by who placed the original restoration: findings from the National Dental PBRN

OBJECTIVES

To evaluate how restoration characteristics are associated with the decision to repair or replace an existing restoration. The following hypotheses were studied: dentists who placed the original restoration are more likely to repair instead of replace restorations (H1) that are in molar teeth; (H2) that are in the upper arch; (H3) that have amalgam restorative material; (H4) if a fracture is not the primary reason for the defect; and (H5) when the restoration comprises more than one surface.

METHODS

This cross-sectional study used a consecutive patient/restoration recruitment design. 194 dentists members of a dental practice-based research network recorded data on restorations in permanent teeth that needed repair or replacement.

RESULTS

For 6623 of the 8770 defective restorations in 6643 patients, the treatment was provided by the dentist who had not placed the original restoration (75%). The 2-way interaction revealed that dentists who had placed the original restoration often chose to repair when the defective restoration was in a molar, relative to premolar or anterior teeth (OR=2.2, p<.001); and chose to replace when the restoration had amalgam (OR=0.5, p<.001), and when it was a fracture compared to another reason (OR=0.8, p=001).

CONCLUSION

Most dentists are not conservative when they revisit a restoration that they originally placed regardless of type of failure, number of surfaces or material used. However, dentists who had placed the original restoration were significantly more likely to repair it when the defective restoration was in a molar tooth.

CLINICAL SIGNIFICANCE

Most dentists who placed the original restoration were prone to replace it, however if the defective restoration was located in a molar tooth they would consider repairing it.

Potential release of in vivo trace metals from metallic medical implants in the human body: from ions to nanoparticles--a systematic analytical review

Metal ion release from metallic materials, e.g. metallic alloys and pure metals, implanted into the human body in dental and orthopedic surgery is becoming a major cause for concern. This review briefly provides an overview of both metallic alloys and pure metals used in implant materials in dental and orthopedic surgery. Additionally, a short section is dedicated to important biomaterials and their corrosive behavior in both real solutions and various types of media that model human biological fluids and tissues. The present review gives an overview of analytical methods, techniques and different approaches applied to the measurement of in vivo trace metals released into body fluids and tissues from patients carrying metal-on-metal prostheses and metal dental implants. Reference levels of ion concentrations in body fluids and tissues that have been determined by a host of studies are compiled, reviewed and presented in this paper. Finally, a collection of published clinical data on in vivo released trace metals from metallic medical implants is included.

Human brain mercury levels related to exposure to amalgam fillings

The safety of dental amalgam as the primary material in dental restoration treatments has been debated since its introduction. It is widely accepted that amalgam restorations continuously release elemental mercury (Hg) vapor, which is inhaled and absorbed by the body and distributed to tissues, including the brain. The aim of the present study was to investigate whether the presence of amalgam fillings is correlated with brain Hg level. The Hg levels in the parietal lobes of the brains of 32 cadavers were analyzed with an atomic absorption spectrometer with the mercury hydride system. A total of 32 brain samples were tested; of these, 10 were from cadavers with amalgam fillings, while 22 of them were amalgam free. Hg was detected in 60.0% (6 of 10) of the samples in the amalgam group and in 36.3% (8 of 22) in the amalgam-free group. The average Hg level of the amalgam group was 0.97 ± 0.83 µg/g (minimum: 0.3 µg/g and maximum: 2.34 µg/g), and in the amalgam-free group, it was 1.06 ± 0.57 µg/g (minimum: 0.17 µg/g and maximum: 1.76 µg/g). The results of the present study showed no correlation between the presence of amalgam fillings and brain Hg level.

A Prospective Clinical Study on Blood Mercury Levels Following Endodontic Root-end Surgery with Amalgam

INTRODUCTION

The purpose of this clinical study was to compare the blood mercury levels before and after endodontic surgery using amalgam as a root-end filling material.

MATERIALS AND METHODS

Fourteen patients requiring periradicular surgery participated in this prospective clinical study. A zinc-free amalgam was employed as root-end filling material. Blood samples were collected at three intervals: immediately before, immediately after and one week postoperatively. Mercury content of the blood was determined using gold amalgamation cold-vapor atomic absorption spectrometry. Obtained data were analyzed using analysis of variance for repeated measures and paired t-test.

RESULTS

The mean (SD) of blood mercury levels was 2.20 (0.24) ng/mL immediately before surgery, 2.24 (0.28) ng/mL immediately after surgery and 2.44 (0.17) ng/mL one week after the periradicular surgery. The blood mercury level one week post-operative was significantly higher than both blood mercury levels immediately before (P<0.001) and immediately after (P=0.005) the surgery.

CONCLUSION

Placement of an amalgam retroseal during endodontic surgery can increase blood mercury levels after one week. The mercury levels however, are still lower than the toxic mercury levels. We suggest using more suitable and biocompatible root-end filling materials.

Restorative material and other tooth-specific variables associated with the decision to repair or replace defective restorations: findings from The Dental PBRN

OBJECTIVES

Using data from dentists participating in The Dental Practice-Based Research Network (DPBRN), the study had 2 main objectives: (1) to identify and quantify the types of restorative materials in the existing failed restorations; and (2) to identify and quantify the materials used to repair or replace those failed restorations.

METHODS

This cross-sectional study used a consecutive patient/restoration recruitment design. Practitioner-investigators recorded data on consecutive restorations in permanent teeth that needed repair or replacement. Data included the primary reason for repair or replacement, tooth surface(s) involved, restorative materials used, and patient demographics.

RESULTS

Data for 9875 restorations were collected from 7502 patients in 197 practices for which 75% of restorations were replaced and 25% repaired. Most of the restorations that were either repaired or replaced were amalgam (56%) for which most (56%) of the material used was direct tooth-coloured. The restorative material was 5 times more likely to be changed when the original restoration was amalgam (OR=5.2, p<.001). The likelihood of changing an amalgam restoration differed as a function of the tooth type (OR=3.0, p<.001), arch (OR=6.6, p<.001); and number of surfaces in the original restoration (OR=12.2, p<.001).

CONCLUSION

The probability of changing from amalgam to another restorative material differed with several characteristics of the original restoration. The change was most likely to take place when (1) the treatment was a replacement; (2) the tooth was not a molar; (3) the tooth was in the maxillary arch; and (4) the original restoration involved a single surface.

Removal of dental amalgam fillings and its influence on saliva morphological picture - case report

The influence of dental restorative materials on patients' general and oral health is the main interest of many researchers but the question of their safety is still under consideration. An otherwise healthy 23-year-old patient with no history of oral abnormalities was examined. Dental amalgam restorations were replaced by composite resin material. Salivary smears prepared two days and two weeks after the amalgam removal were compared with those taken before the procedure.