Comparative evaluation of marginal leakage of provisional crowns cemented with different temporary luting cements: In vitro study

Loss of pulp vitality correlated with the duration of the interim restoration and the experience of the dentist: A retrospective study

STATEMENT OF PROBLEM

The second most common biological complication in fixed prosthodontics is loss of pulp vitality, which may lead to restoration loss. While reasons for loss of pulp vitality are unclear, 2 potential contributing factors, duration of the interim restoration and operator experience, have not been fully investigated.

PURPOSE

The purpose of this retrospective study was to investigate whether the duration of the interim restoration or the experience of the dentist was correlated with loss of pulp vitality.

MATERIAL AND METHODS

Fixed prosthetic restorations placed between 2005 and 2012 were retrospectively analyzed. Abutment teeth supporting single-unti or multiunit restorations were evaluated regarding loss of pulp vitality. The Mann-Whitney U test and simple logistic regression were used, with α=.05 for the subsequent multiple logistic regression. The experience of dental professionals was defined by the number of treatments performed and coupled with failure rate by using an analysis of variance.

RESULTS

One hundred seventy-four dentists made 15 879 restorations, of which 1136 failed during the observation period, a failure rate of 7.2%. Two hundred fifty restorations were randomly selected from the failed restorations, and a corresponding 250 restorations were randomly selected from nonfailed restorations for the control group. Increased duration with interim replacement was linked to a higher risk of loss of pulp vitality (P<.001). Failure rate in the dentist group varied from 0% to 100%. No significant differences in failure rate were found among dentists who did few restorations and those who performed larger numbers of restorations.

CONCLUSIONS

The results of the present study suggest that operator experience does not affect failure rate. However, extended time with an interim restoration was a contributing factor to the loss of pulp vitality.

The occlusal precision of milled versus printed provisional crowns

OBJECTIVES

The aim of this study was to compare the occlusal precision of computer-aided-design/ computer-assisted-manufacturing (CAD/CAM) milled versus 3D printed polymethylmethacrylate (PMMA) temporary prosthetic crowns , starting from the same digital CAD design.

MATERIALS AND METHODS

The study sample included 34 patients presenting 34 premolars in need of prosthetic rehabilitation: a total of 68 temporary crowns were manufactured, 34 of which milled and 34 printed. Immediately after manufacturing, the milled and printed provisionals were scanned with a desktop scanner (E1, 3Shape) to obtain STL files, that were superimposed to the original CAD design in order to identify the occlusal trueness (Analysis A). A second occlusal comparison was performed by scanning both kind of provisional after being placed intraorally with Trios scanner (3 Shape); intraoral scans were obtained in order to compare STL files of provisionals before and after occlusal adjustments (Analysis B).  The occlusal trueness was identified at three reference points, P1 (vestibular cusp), P2 (palatal / lingual cusp), P3 (central fossa). The statistical analysis was performed using the R 3.4.3 statistical software (The R Foundation for Statistical Computing), with a significance level of p <0.05.

RESULTS

Overall, the printed crowns showed lower occlusal differences than the milled crowns, when compared to the CAD design file, with a statistically significant difference in P1 (difference of 0.025 ± 0.046 mm), P2 (difference of 0.027 ± 0 0.044 mm) and P3 ( difference of 0.018 ± 0.050) for Analysis A (p <0.05). In the Analysis B the direct comparison between the degree of average difference between the pre-adjustment and the post-occlusal adjustment of the milled and printed crowns shows that the printed crowns have lower occlusal mean difference values in all three points compared to the milled ones (difference of 0.146 ± 0.273 mm in P1, 0.285 ± 0.360 mm in P2 and 0.257 ± 0.277 mm in P3).

CONCLUSIONS

Within the limitation of this study, the data obtained showed a better occlusal surface dimensional accuracy of the 3D printed provisional crowns, when compared to the milled ones. Comparing the results obtained, it is possible to assume that the intraoral scans also had a contribution to occlusion, beside the manufacturing method. 3D printing can be successfully applied for manufacturing temporary PMMA crowns.

Microleakage at Implant Abutment and Prosthesis Interface in Cemented Implant-Supported Prosthesis

BACKGROUND

Dental implants have an important role in mainstream dental practice today to restore esthetics. The present study was conducted to evaluate the microleakage at implant abutment and prosthesis interface in cemented implant-supported prosthesis.

MATERIALS AND METHODS

The present study comprised sixty replicas of abutment analog with length 5 mm, width of platform 4.8 mm, and taper 6° which were milled and divided into three groups. In Group I, nickel-chromium copings were fabricated; marginal gap was evaluated with optical microscope and luted with zinc oxide noneugenol cement, Group II with zinc polycarboxylate cement, and Group III with zinc phosphate cement. Microleakage was scored by the method used by Tjan et al.

RESULTS

The mean microleakage score in Group I was 2.5, in Group II was 1.9, and in Group III was 1.05. The difference was significant (P < 0.05).

CONCLUSION

All cements showed microleakage. Minimum microleakage was seen with zinc phosphate cement than zinc oxide noneugenol cement and zinc polycarboxylate cement.

Microleakage and Bacterial Adhesion with Three Restorative Materials Used to Seal Screw-access Channels of Implant Abutments: An In vitro Study

Background:

Proper sealing of screw-access channels against microbial microleakage is advisable for the long-term success of screw-retained implant prosthesis.

Objective:

This study aimed to compare the bacterial adhesion and microleakage with three restorative materials, namely, composite resin, acrylic resin and bis-acryl, that are used to cover the access channels of screw-retained implant prostheses, using polytetrafluoroethylene tape as a spacer material.

Materials and Methods:

In this in vitro study, 18 titanium straight abutments (Hex-lock^® Zimmer) were torqued into implant analogs, which were then subdivided into three groups. The samples of each group were filled with polytetrafluoroethylene tape and sealed with the three restorative materials (Group A: composite resin; Group B: acrylic resin; Group C: bis-acryl). Measurements of surface bacterial adhesion and internal microleakage were then recorded. The results were statistically analyzed using Kruskal–Wallis and Chi-square tests.

Results:

No significant difference was found between the investigated materials in terms of their sealing effectiveness against microbial microleakage (P = 0.06). Regarding bacterial adhesion, composite resin showed the highest number of surface adhesion, but there was no significant difference between the three materials (P = 0.081).

Conclusion:

The results of this study suggest that composite resin, acrylic resin and bis-acryl materials could be used alternatively in sealing the implant access channel owing to no significant differences in terms of microleakage and bacterial adhesion.

Antimicrobial properties of dental cements modified with zein-coated magnesium oxide nanoparticles

The aim of this study was to test the antimicrobial properties of dental cements modified with magnesium oxide (MgO) nanoparticles. Zein-modified MgO nanoparticles (zMgO) in concentrations (0.0, 0.3, 0.5, and 1.0%) were mixed with dental cements (Fuji II, Rely X Temp E, Ionoglass Cem, Es Temp NE, and System P link). Eight discs were fabricated from each zMgO-cement pair for a total of 32 specimens for each cement. Characterization of the dental cements incorporating zMgO was done by X-ray Diffraction (XRD) and Field Emission Scanning Electron Microscopy (FESEM). The antimicrobial properties of the mixtures were tested using direct contact and agar diffusion assays against Streptococcus mutans, Staphylococcus aureus, Enterococcus faecalis, and Candida albicans. Data was analyzed using two-way analysis of variance and LSD post hoc test at 0.05 significance level. XRD spectra showed sharp peaks of zMgO indicating its high crystalline nature, while the amorphous dental cements with zMgO had broad peaks. FESEM analysis showed a uniform distribution of the zMgO nanoparticles in the cement. There were significant inhibition zone values associated with all concentrations of zMgO-cement mixtures tested compared to controls (p < 0.001) with a dose-response recorded only with Fuji II. Optical density values were significantly lower in zMgO groups compared to controls for all microorganisms. The effect was most prominent with Rely X against C. albicans and S. aureus. Dental cements containing zMgO showed significant antimicrobial properties that were dependent on the specific initial cement substrate.

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Antimicrobial nanoparticles (NPs) are widely used in dental materials to improve their biological properties.

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Magnesium Oxide (MgO) NPs are novel antimicrobial agents.

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Incorporation of MgO NPs in dental cements aids in minimizing bacterial colonization at the restoration margin.

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Zein polymer facilitates the dispersion of MgO NPs and avoid its agglomeration.

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Zein polymer effectively enhances the performance of MgO NPs.

Effect of cement space on marginal discrepancy and retention of CAD/CAM crown

This research aimed to evaluate the effect of cement space on the marginal discrepancy and retention of computer-aided design/computer-aided manufacturing (CAD/CAM) crowns. A total of 30 premolar Frasaco teeth were machined to receive crowns with cement spaces of 70, 90, and 110 μm. The marginal discrepancy measurements were done before and after cementation. Pull-off test was conducted using universal testing machine (UTM). Data was analyzed using two-way mixed ANOVA with post-hoc Bonferroni test and Kruskal-Wallis test. The crowns with cement space of 70 μm showed a significantly higher absolute marginal discrepancy than those with 90 and 110 μm. No significant effect on the crown retention was found. Within the limitations of this study, modifying cement space to 90 μm and 110 μm may improve the marginal adaptation of CAD/CAM crown, whereas adjusting cement space from 70 to 110 μm did not significantly affect the crown retention.

Comparative evaluation of microleakage of metallic copings luted with three different commercially available luting cements: An in vitro study

Aim

To evaluate the microleakage of metallic copings luted with three different commercially available luting cements.

Setting and Design

Comparative evaluation in vitro study.

Materials and Methods

Thirty replicas of abutment analog were milled and divided into 3 groups. Nickel chromium copings were fabricated; marginal gap was evaluated with optical microscope and luted with Zinc Oxide Non Eugenol cement, Zinc Polycarboxylate cement and Zinc Phosphate cement. After Thermocycling, cemented specimens were placed into 0.5% aqueous solution of basic fuchsin solution for 24 hours for dye penetration. Copings were longitudinally sectioned and microleakage scores were evaluated.

Statistical Analysis Used

Kruskal-Wallis analysis of variance (ANOVA) followed by Chi-Square test. Pairwise comparison of groups with Mann Whitney U test.

Result

Mean microleakage score was least for Zinc Phosphate cement (1.075 ± 0.85) followed by Zinc Polycarboxylate cement (1.80± 0.23) and most for Zinc Oxide Non Eugenol (2.1± 0.37). The results of the study were statistically significant, P < 0.05.

Conclusions

Within the limitations of the study, it was found that all cements exhibited certain amount of microleakage. Zinc Phosphate cement exhibited a mean microleakage score that was significantly lower than Zinc Oxide Non Eugenol cement and Zinc Polycarboxylate cement. When microleakage scores of Zinc Oxide Non Eugenol cement and Zinc Polycarboxylate cement were compared, the difference was found to be insignificant indicating that microleakage in these cements is similar.

Microleakage of different temporary luting agents used for cementing provisional restorations on custom cast posts and cores

BACKGROUND

This study aimed to compare the effect of four temporary luting agents on preventing the coronal microleakage of teeth restored with custom cast post and core.

MATERIALS AND METHODS

In this in vitro original study, after removing 9 mm of gutta percha from root canals of 32 single-canaled premolars, the acrylic resin patterns of the post and core were fabricated. Patterns were cast with Ni-Cr metal alloy and then cemented with glass ionomer. Using self-curing acrylic resin, provisional restorations were made. Then, teeth were randomly allocated to four groups for each temporary cement including zinc oxide eugenol (Temp Bond), zinc oxide noneugenol (Temp Bond NE), noneugenol resin-based temporary luting agent (Temp Bond Clear), and noneugenol urethane methacrylate polymer-based temporary luting agent (Dento temp). Teeth were subjected to thermocycling, immersed in silver nitrate for 6 h and then sectioned. The amount of dye penetration in the margin of provisional crown and into the coronal part of the root canals was measured using a stereomicroscope. Data were analyzed using the Kruskal-Wallis and Dunn tests with significance level of 0.05.

RESULTS

All the luting agents showed some degree of microleakage (Group 1 showed the most microleakage). According to the pair comparison between the groups, Group 1 revealed a significant difference with others (P < 0.05). Furthermore, Group 2 showed more microleakage as compared to Group 4 (P = 0.037).

CONCLUSION

Temp Bond showed the highest microleakage as compared to other luting agents. Furthermore, Temp Bond NE revealed a weaker sealability as compared to Dento temp.

Comparison of the Effects of Cytotoxicity and Antimicrobial Activities of Self-adhesive, Eugenol and Noneugenol Temporary and Traditional Cements on Gingiva and Pulp Living Cells

Aims and objectives:

The aim of this in vitro study was to investigate the antibacterial and cytotoxic effect of cements: zinc polycarboxylate, glass ionomer, self-adhesive resin cement, eugenol-containing and eugenol-free temporary cements.

Materials and methods:

The agar-diffusion test was carried out on 4 types of bacteria: Streptococcus mutans ( S. mutans; ATCC 35668), Streptococcus salivarius ( S. salivarius; ATCC 13419), Streptococcus sangius ( S. sangius; ATCC 10556), and Lactobacillus casei ( L. casei; ATCC 27139). Freshly prepared cement samples were placed on a brain heart infusion medium and left at 37°C for 24 hours in a CO2 incubator. Ampicillin disks of 10 mg were used as positive controls. Antimicrobial effects were determined using the zone of inhibition measurement in millimeters at 24 and 48 hours. Cytotoxicity was assessed through a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay (SERVA Electrophoresis GmbH, Heidelberg, Germany). To evaluate cell viability, an optical density microplate reader (Tecan™ Sunrise, Männedorf, Switzerland) was used at 24 and 48 hours at 570 and 630 nm, respectively.

Results:

Except the positive control group, the Adhesor luting cement showed a higher inhibitory effect on S. sangius and L. casei. RelyX Temp E temporary cement showed an inhibitory effect on S. sangius and L. casei, whereas the Cavex temporary cement showed an inhibitory effect on only S. sangius at 24 and 48 hours. At 100% concentration, Cavex temporary cement showed the least toxicity (23.6% pulp cell and 9.9% gingival cell) and highest cell viability (76.4% pulp cell and 90.1% gingival cell) at 24 hours. However, Meron, Adhesor, Panavia SA luting, and RelyX Temp E temporary cements showed the highest toxicity (above 94% gingival cell and 95% pulp cell) at 100% concentration.

Conclusions:

Meron, Adhesor, Panavia SA luting, and RelyX Temp E temporary cements may have a cytotoxic potential. None of the cements showed an inhibitory effect on S. mutan and S. salivarius, whereas Adhesor luting cement has a higher inhibitory effect than that of S. sangius and L. casei.