Use of zinc phosphate cement as a luting agent for Denzir trade mark copings: an in vitro study

Evaluation of Microleakage Using Different Luting Cements in Kedo Zirconia Crowns: An In Vitro Assessment

Introduction A space between the prepared tooth and the cemented crown can cause microleakage, allowing microorganisms to enter, which in turn leads to the breakdown of the luting cement. To achieve an optimum fit, several factors should be considered, including the type of crown used, the taper of tooth preparation, and the type of cementing agent. Aim The purpose of the current study is to evaluate the microleakage of zirconia crowns cemented with glass ionomer cement (GIC), resin-modified GIC (RMGIC), and self-adhesive resin cement. Materials Forty-five primary mandibular molars were divided into three groups: Group I receiving GIC, Group II receiving RMGIC, and Group III receiving self-adhesive resin cement. These cements were used to lute the teeth with Kedo zirconia crowns. The restored samples underwent thermal cycling and were assessed for microleakage under a stereomicroscope. For the statistical analysis, SPSS version 23.0 was used. Descriptive statistics were presented as frequencies and percentages. Analytical statistics, including the Mann Whitney U test, were used to assess the differences in the level of microleakage between the groups at p < 0.05. Results The Mann Whitney U test revealed no significant difference in the level of microleakage between GIC and RMGIC (p = 0.072). However, self-adhesive resin cement showed significantly less microleakage than GIC (p = 0.000). Similarly, when comparing RMGIC and self-adhesive resin cement, the latter showed significantly less microleakage than the former (p = 0.001). Conclusion Microleakage of Kedo zirconia crowns on mandibular first molars was highest when luted with GIC, followed by RMGIC, and was least when luted with self-adhesive resin cement.

Shear bond strength of different luting agents to polyether ether ketone

Background

Polyether ether ketone (PEEK) was recently introduced to dentistry. However, difficulty in provision of a strong durable bond is its main drawback. Thus, precise surface treatment and use of a suitable luting agent are imperative for bonding of PEEK restorations. This study aimed to assess the effect of type of luting agent on shear bond strength (SBS) of PEEK.

Materials and Methods

In this in vitro study, 60 square-shaped PEEK samples were fabricated and sandblasted with 110 μm Al₂O₃ particles. The samples were then divided into four groups based on the type of cement used (n = 15): zinc phosphate cement, Panavia F2, Panavia V5, and resin-modified glass-ionomer (RMGI) cement. After bonding, the samples were thermocycled for 5000 cycles. The SBS was measured by a universal testing machine. The surface of samples was inspected under a video measuring machine to determine the mode of failure. Data were analyzed using the Kruskal-Wallis test via SPSS version 24 (α = 0.05).

and Methods

In this in vitro study, 60 square-shaped PEEK samples were fabricated and sandblasted with 110 μm Al₂O₃ particles. The samples were then divided into four groups based on the type of cement used (n = 15): zinc phosphate cement, Panavia F2, Panavia V5, and resin-modified glass-ionomer (RMGI) cement. After bonding, the samples were thermocycled for 5000 cycles. The SBS was measured by a universal testing machine. The surface of samples was inspected under a video measuring machine to determine the mode of failure. Data were analyzed using the Kruskal-Wallis test via SPSS version 24 (α = 0.05).

Results

RMGI did not bond to PEEK. The SBS values were 4.02 ± 2.87 megapascals (MPa) for Panavia V5, 10.84 ± 6.05 MPa for Panavia F2, and 10.50 ± 2.88 MPa for zinc phosphate. The SBS in the Panavia V5 group was significantly lower than that in the Panavia F2 (P = 0.001) and zinc phosphate (P < 0.001) groups. No significant difference existed between the Panavia F2 and zinc phosphate groups in this respect (P > 0.05).

Conclusion

Panavia F2 resin cement and zinc phosphate conventional cement provided the highest bond strength to PEEK, while RMGI did not bond to PEEK.

Retention and Clinical Performance of Zirconia Crowns: A Comprehensive Review

Zirconia has been used for rehabilitation of edentulous spaces approximately for a decade, and there have been several reports regarding the clinical performance and retention of zirconia crowns. Outstanding mechanical properties, biocompatibility, and excellent aesthetics make zirconia-based crowns as a popular crown among the current all-ceramic crowns in restorative dentistry. However, restoration with a zirconia crown is a challenging treatment. The goal of this study was to assess the current literature to summarize the studies reporting the effective risk factors on retention of zirconia crowns to provide clinicians with a useful point of view in the decision-making process for use of these restorations. Literature based-search was performed to find related articles until August 2020 using EMBASE, Google Scholar, and MEDLINE. Search terms used were “zirconia restorations properties,” “zirconia crowns clinical performance,” “zirconia crown survival,” “biological complications,” and “zirconia crown retention.” Results were limited to papers available in English. The references of all related literature were also searched for further citations. Overall, although clinical long-term and follow-up studies are a vital requirement to conclude that zirconia has great reliability, it seems that zirconia crown restorations are both well tolerated and sufficiently resistant.

Microhardness evaluations of CAD/CAM ceramics irradiated with CO2 or Nd:YAP laser

BACKGROUND AND AIMS

The aim of this study was to measure the microhardness values of irradiated computer-aided design/computer-aided manufacturing (CAD/CAM) ceramics surfaces before and after thermal treatment.

MATERIALS AND METHODS

Sixty CAD/CAM ceramic discs were prepared and grouped by material, i.e. lithium disilicate ceramic (Emax CAD) and zirconia ceramic (Emax ZirCAD). Laser irradiation at the material surface was performed with a carbon dioxide laser at 5 Watt (W) or 10 W power in continuous mode (CW mode), or with a neodymium:yttrium aluminum perovskite (Nd:YAP) laser at 10 W on graphite and non-graphite surfaces. Vickers hardness was tested at 0.3 kgf for lithium disilicate and 1 kgf for zirconia.

RESULTS

Emax CAD irradiated with CO₂ at 5 W increased microhardness by 6.32 GPa whereas Emax ZirCAD irradiated with Nd:YAP decreased microhardness by 17.46 GPa.

CONCLUSION

CO₂ laser effectively increases the microhardness of lithium disilicate ceramics (Emax CAD).

Influence of type of cement on the color and translucency of monolithic zirconia

STATEMENT OF PROBLEM

With the development of translucent zirconia, questions regarding the influence of cements on the final color of monolithic zirconia restorations have arisen.

PURPOSE

The purpose of this in vitro study was to evaluate color changes in terms of the perceptibility and acceptability of monolithic zirconia-and-cement combinations with 2 monolithic zirconia thicknesses and 3 types of cement. The translucency parameters of these combinations were also compared.

MATERIAL AND METHODS

Sixty monolithic zirconia ceramic disks were milled with 2 different thicknesses (0.6 mm and 1 mm). A conventional glass ionomer cement, a resin-modified glass ionomer cement, and a resin cement from the same manufacturer were applied to the ceramic surfaces of both thickness disks (n=10). Translucencies and color changes of the monolithic zirconia specimens after cement application were examined by using a spectrophotometer, and translucency parameters (TPs) and color changes (ΔEs) were calculated and statistically analyzed.

RESULTS

Colors and TPs of the zirconia disks changed significantly after being cemented to 0.6- and 1-mm-thick disks (P<.05). The lowest ΔE values (3.53 for the 0.6-mm and 2.23 for the 1-mm thick disks) were observed for the zirconia-resin modified glass ionomer combination, whereas the highest ΔE values (5.64 for the 0.6-mm and 5.06 for the 1-mm thick disks) were observed for the zirconia-resin cement combination. The glass ionomer cement most strongly affected the TP values of both of the thicknesses.

CONCLUSIONS

Cement types and zirconia thickness affected the colors and translucencies of the monolithic zirconia specimens.

Influence of surface treatment of yttrium-stabilized tetragonal zirconium oxides and cement type on crown retention after artificial aging

STATEMENT OF PROBLEM

Information about the influence of zirconia crown surface treatment and cement type on the retention of zirconia crowns is limited. It is unclear whether zirconia crowns require surface treatment to enhance their retention.

PURPOSE

The purpose of this in vitro study was to evaluate the effect of surface treatment on the retention of zirconia crowns cemented with 3 different adhesive resin cements after artificial aging.

MATERIAL AND METHODS

Ninety extracted human molars were prepared for ceramic crowns (approximately 20-degree taper, approximately 4-mm axial length) and were divided into 3 groups (n=30). Computer-aided design and computer-aided manufacturing zirconia copings were fabricated. Three surface treatments were applied to the intaglio surface of the copings. The control group received no treatment, the second group was airborne-particle abraded with 50 μm Al2O3, and the third group was treated with 30 μm silica-modified Al2O3, The copings were luted with a self-etch (RelyX Unicem 2), a total-etch (Duo-Link), or a self-etch primer (Panavia F 2.0) adhesive cement. They were stored for 24 hours at 37°C before being artificially aged with 5000 (5°C-55°C) thermal cycles and 100,000 cycles of 70 N dynamic loading. Retention was measured on a universal testing machine under tension, with a crosshead speed of 0.5 mm/min. Statistical analysis was performed with 1-way and 2-way ANOVA.

RESULTS

Mean retention values ranged from 0.72 to 3.7 MPa. Surface treatment increased crown retention, but the difference was not statistically significant (P>.05), except for the Duo-Link cement group (P<.05). Analysis of the adhesives revealed that the Duo-Link cement resulted in significantly lower crown retention (P<.05) than the other 2 cements.

CONCLUSION

For zirconia crowns, retention seems to be dependent on cement type rather than surface treatment.

Oral health knowledge and practices of secondary school students, tanga, Tanzania

A good quality of life is possible if students maintain their oral health and become free of oral disease. A structured questionnaire assessed 785 students' level of oral health knowledge and practices. About 694 (88.4%) students had adequate level of knowledge on causes, prevention, and signs of dental caries, 760 (96.8%) on causes and prevention of periodontal diseases, 695 (88.5%) on cigarette smoking as cause of oral cancer, and 770 (98.1%) students on importance of dental checkups. Majority 717 (91.3%) had adequate practice of sugary food consumption; while 568 (72.4%) had acceptable frequency of tooth brushing, 19 (2.4%) brushed at an interval of twelve hours, and 313 (39.9%) visited for checkup. Majority of students had an adequate level of knowledge on oral health but low level of oral health practices. Both genders had similar level of knowledge with male predominance in oral health practices. Age had no influence on the level of oral health knowledge and practices of students.

Health promoting schools provide community-based learning opportunities conducive to careers in rural practice

The World Health Organization conceived "health-promoting schools" as a means of providing the information and support systems necessary for the worldwide changes in behavior that are needed to improve health globally and decrease health care costs. We developed and evaluated a model of progressively implementing health-promoting schools with support from university medical school trainees in Canada and Uganda. The model uses oral health as a medium for establishing rapport and success around a topic with little stigma. The evaluation involved questionnaires of the Canadian trainees about practice intentions before and after involvement in the health-promoting schools to determine whether community-based learning in health-promoting schools resulted in more trainees planning to work in rural areas or underserved countries. We found that Canadian medical trainees cited their personal involvement and perceived ability to effect significant and identifiable positive change in both the school children and the community as reasons why they were more willing to practice in rural or under-served areas.

Properties of Zinc Releasing Surfaces for Clinical Applications

Two series of glasses of general formula (2-p) SiO2·1.1Na 2O·CaO·pP2O5·xZnO (p=0.10, 0.20; x=0.0, 0.16, 0.35, and 0.78) have been analyzed for physico-chemical surface features before and after contact with simulated body fluid, morphological characteristics, and osteoblast-like cells behavior when cultured on them. The resulted good cell adhesion and growth, along with nonsignificant changes of the focal contacts, allow the authors to indicate HZ5 and HP5Z5 glasses as the ones having optimal ratio of Zn/P to maintain acceptable cell behavior, comparable to the bioactive glass (Bioglass®) used as a control; results are also rationalized by means of three-dimensional models derived by molecular dynamic simulations, with decomposition and conversion rates optimized with respect to the parent Hench's Bioglass®.