Influence of Chairside Simulated Adjustment (Finishing and Polishing) Protocol and Chlorhexidine Mouthwash Immersion on Color Stability and Translucency of 2 and 3 Preshaded Multilayered Monolithic Zirconia

BACKGROUND Preshaded monolithic zirconia (MLZ) is reported to have high translucency. This study aimed to assess the effect of chlorhexidine gluconate (ChG) mouthwash on color and translucency parameter (TP) of 2 different preshaded MLZ dental ceramics after clinical adjustment. MATERIAL AND METHODS Two MLZ disk-shaped specimens [NPM (Nacera Pearl Multi-Shade) (n=72) and CZM (Ceramill Zolid FX Multilayer)] (n=72) were simulated for clinical adjustment, finished, and polished using 2 adjustment kits [recommended kit, third-party kit: Diasynt Plus and SUN (n=12 each)] and later immersed in ChG mouthwash (Avohex) for 2 weeks. Difference in color (ΔE) and TP (Y) were calculated using the CIELab formula after measuring the coordinates (Lab) with a colorimeter. Individual changes in color and TP were assessed on the Clinical acceptance (perceptible) threshold (CAT/CPT) and Translucency perception threshold (TPT), respectively. Differences between the 2 ceramics were assessed using one-way ANOVA and post hoc tests, with all differences considered significant at P<0.05. RESULTS NPM and CZM differed in color at baseline despite having the same Vita shade combination. Between the 2 preshaded MLZ ceramics, NPM showed significant changes in color when adjusted with a third-party kit. Chlorhexidine produced changes in color and TP that were designated as clinically perceptible (ΔE=1.0 to 3.3) on the CAT/CPT and TPT scales, irrespective of the adjustment kit used. ChG produced the least or no changes in glazed MLZ specimens. CONCLUSIONS ChG mouthwash, whenever prescribed for preshaded MLZ restoration, should be adjusted prior to final glazing to avoid clinical adjustments that adversely affects color and translucency of the restoration.

Shear Strength of Repaired 3D-Printed and Milled Provisional Materials Using Different Resin Materials with and without Chemical and Mechanical Surface Treatment

The aim of this study was to assess the shear bond strength of 3D-printed and milled provisional restorations using various resin materials and surface finishes. There were 160 preliminary samples in all, and they were split into two groups: the milled group and the 3D-printed group. Based on the resin used for repair (composite or polymethylmethacrylate (PMMA)) and the type of surface treatment utilized (chemical or mechanical), each group was further divided into subgroups. The specimens were subjected to thermocycling from 5 °C to 55 °C for up to 5000 thermal cycles with a dwell time of 30 s. The mechanical qualities of the repaired material underwent testing for shear bond strength (SBS). To identify the significant differences between the groups and subgroups, a statistical analysis was carried out. Three-way ANOVA was used to analyze the effects of each independent component (the material and the bonding condition), as well as the interaction between the independent factors on shear bond strength. Tukey multiple post-hoc tests were used to compare the mean results for each material under various bonding circumstances. The shear bond strengths of the various groups and subgroups differed significantly (p < 0.05). When compared to the milled group, the 3D-printed group had a much greater mean shear bond strength. When compared to PMMA repair, the composite resin material showed a noticeably greater shear bond strength. In terms of surface treatments, the samples with mechanical and chemical surface treatments had stronger shear bonds than those that had not received any. The results of this study demonstrate the effect of the fabrication method, resin type, and surface treatment on the shear bond strength of restored provisional restorations. Particularly when made using composite material and given surface treatments, 3D-printed provisional restorations showed exceptional mechanical qualities. These results can help dentists choose the best fabrication methods, resin materials, and surface treatments through which to increase the durability and bond strength of temporary prosthesis.

Effects of Blood Contamination and Decontamination Protocol on Reverse Torque Value of Abutment Screws in Dental Implants: An In Vitro Study

Background and Objective: Loosening of abutment screws in dental implants is a mechanical complication that affects prosthetic treatments and hence, patient satisfaction. Blood contamination of abutment screws may play a role in this phenomenon. However, only limited research attention has been given to this issue. In the present study, we determined the effect of blood contamination and decontamination protocol on the reverse torque value (RTV) of abutment screws. Materials and Methods: A questionnaire-based survey was sent to 210 implantologists requesting feedback on their attitude to the blood contamination issue and the decontamination protocols used. The survey responses were used in a selection of the decontamination solutions that were used in the subsequent in vitro study on the effects of blood decontamination protocol on the RTV of abutment screws. Thus, three study groups were used (n = 20 abutment screws in each group): Group 1 (control group; blood-contaminated screws); Group 2 (screws decontaminated with 5.25% sodium hypochlorite (NaOCl) solution); and Group 3 (screws decontaminated with normal saline solution (0.9%)). Then, each of the connections were subjected to thermocycling, and RTVs of the screw were measured using a digital torque meter. Intragroup and intergroup RTVs were analyzed for significance using analysis of variance (ANOVA) and Tukey's honestly significant difference (HSD) tests. Results: 48% of the implantologists responded to the survey; 80% of them were concerned with blood contamination in the implant connection, especially before abutment loading and 85% of them used either chlorhexidine solution or normal saline solution as the decontamination agent. The mean RTV for Group 2 screws (30.27 ± 2.8 N.cm) was significantly greater than that for Group 3 screws (26.02 ± 1.99 N.cm) which, in turn, was significantly greater than that for Group 1 screws (23.64 ± 1.84 N.cm). Conclusion: Decontamination of blood-covered connections using 5.25% NaOCl solution or normal saline solution restores the RTV of abutment screws. This finding may have clinical relevance in that the decontaminated screws may contribute to the low incidence of screw loosening and, ultimately, improved patient satisfaction.

Mast cells/basophils in the peripheral blood of allergic individuals who are HIV-1 susceptible due to their surface expression of CD4 and the chemokine receptors CCR3, CCR5, and CXCR4

A population of metachromatic cells with mast cell (MC) and basophil features was identified recently in the peripheral blood of patients with several allergic disorders. This study now shows that these metachromatic cells express on their surface the high-affinity IgE receptor (FcepsilonRI), CD4, and the chemokine receptors CCR3, CCR5, and CXCR4, but not the T-cell surface protein CD3 and the monocyte/macrophage surface protein CD68. This population of MCs/basophils can be maintained ex vivo for at least 2 weeks, and a comparable population of cells can be generated in vitro from nongranulated hematopoietic CD3(-)/CD4(+)/CD117(-) progenitors. Both populations of MCs/basophils are susceptible to an M-tropic strain of human immunodeficiency virus 1 (HIV-1). Finally, many patients with acquired immunodeficiency syndrome have HIV-1-infected MCs/basophils in their peripheral blood. Although it is well known that HIV-1 can infect CD4(+) T cells and monocytes, this finding is the first example of a human MC or basophil shown to be susceptible to the retrovirus. (Blood. 2001;97:3484-3490)

The level of HIV infection of macrophages is determined by interaction of viral and host cell genotypes

The outcome of HIV infection in vivo and in vitro depends on the interaction of viral and cellular genotypes. Analysis of infection of blood monocyte-derived macrophages by primary HIV strains shows that approximately one-third of 32 isolates was consistently high-replicating, one-third was consistently low-replicating, and one-third was dependent on the donor of the macrophages (i.e., variable). HIV isolates from patients with AIDS showed enhanced replication within macrophages and predominant use of CCR5 for entry, although 13% did use CXCR4. Tissue isolates from brain and CSF showed an enhanced ability to infect 1-day-old monocytes compared with blood isolates from patients with AIDS. The ability of primary isolates to infect neonatal or adult monocytes maturing into macrophages or placental macrophages correlated directly with the extent of CCR5 expression. Studies of macrophages from pairs of identical twins and unrelated donors showed genetic control over CCR5 expression, which was independent of the CCR5delta32 genotype. Furthermore, these studies showed a marked host-cell genetic effect on the variable primary HIV strains. Although CCR5 was essential for the entry of most primary isolates, it was not the essential "bottleneck" determining productivity of infection. The location of this bottleneck in the HIV replication cycle differs according to viral strain and host-cell donor, but it was exerted before the stage of reverse transcription in 80-90% of cases. Such host-cell genetic factors may affect viral load in vivo where macrophages are the predominant target cells.

Persistent CCR5 utilization and enhanced macrophage tropism by primary blood human immunodeficiency virus type 1 isolates from advanced stages of disease and comparison to tissue-derived isolates

Viral phenotype, tropism, coreceptor usage, and envelope gene diversity were examined in blood isolates collected from 27 individuals at different stages of human immunodeficiency virus type 1 (HIV-1) disease and tissue derived isolates from 10 individuals with AIDS. The majority (89%) of blood and all tissue HIV-1 isolates from all stages of infection were non-syncytium inducing and macrophage (M) tropic. Tropism and productive infection by HIV isolates in both monocytes and monocyte-derived macrophages (MDM) increased in advanced disease (HIV tropism for monocytes, 1 of 6 from categories I and II versus 11 of 21 [P = 0.05] from category IV and II [CD4 < 250]; and high-level replication in MDM, 1 of 6 from categories I and II versus 16 of 21 from categories IV and II [P = 0. 015]). There was a high level of replication of blood and tissue isolates in T lymphocytes without restriction at any stage. Overall, the level of replication in MDM was 5- to 10-fold greater than in monocytes, with restriction in the latter occurring mainly at entry and later stages of replication. Only three blood isolates were identified as syncytium inducing, and all had a dualtropic phenotype. There was a significant increase of HIV envelope gene diversity, as shown by a heteroduplex mobility assay, in advanced disease; this may partly underlie the increase of HIV replication in MDM. Unlike blood isolates (even those from patients with advanced disease), tissue isolates displayed greater similarities (90%) in productive infection between MDM and monocytes. The majority (87%) of all isolates, including those from patients with advanced disease, used CCR5, and only 5 of 37 isolates showed expanded coreceptor usage. These results indicate that in the late stage of disease with increasing viral load and diversity, CCR5 utilization and M-tropism persist in blood and tissue and the replicative ability in macrophages increases. This suggests that these characteristics are advantageous to HIV and are important to disease progression.

Definition of the stage of host cell genetic restriction of replication of human immunodeficiency virus type 1 in monocytes and monocyte-derived macrophages by using twins

Using identical (ID) twins, we have previously demonstrated that host cell genes exert a significant impact on productive human immunodeficiency virus (HIV) infection of monocytes and macrophages (J. Chang et al., J. Virol. 70:7792-7803, 1996). Therefore, the stage in the replication cycle at which these host genetic influences act was investigated in a study using 8 pairs of ID twins and 10 pairs of sex- and age-matched unrelated donors (URDs). In the first phase of the study, blood monocytes and monocyte-derived macrophages (MDM) of ID twins and URDs were infected with 15 HIV type 1 strains. Four well-characterized primary isolates and HIV-BaL were then examined in more detail. The host cell genetic effect in MDM was exerted predominantly prior to complete reverse transcription, as the HIV DNA level and p24 antigen levels were concordant (r = 0.91, P = 0.0001) and similar between the pairs of ID twin pairs (r = 0.96, P = 0.0001) but discordant between URD pairs (r = 0.11, P = 0.3) in both phases of the study. To further examine genetic influence on viral entry, we examined the proportion of CCR5 membrane expression on MDM. As expected, there was wide variability in proportion of MDM expressing CCR5 among URDs (r = 0. 58, P = 0.2); however, this variability was significantly reduced between ID twin pairs (r = 0.81, P = 0.01). Differences in viral entry did not necessarily correlate with CCR5 expression, and only very low levels of CCR5 expression restricted HIV entry and production. In summary, the host cell genetic effect on HIV replication in macrophages appears to be exerted predominantly pre-reverse transcription. Although CCR5 was necessary for infection, other unidentified host genes are likely to limit productive infection.

CCR5 expression correlates with susceptibility of maturing monocytes to human immunodeficiency virus type 1 infection

The chemokine receptor CCR5 and to a lesser extent CCR3 and CCR2b have been shown to serve as coreceptors for human immunodeficiency virus type 1 (HIV-1) entry into blood- or tissue-derived macrophages. Therefore, we examined the expression of the chemokine receptors CCR1, CCR2b, CCR3, CCR5, and CXCR4 as RNAs or as membrane-expressed antigens in monocytes maturing into macrophages and correlated these results with the susceptibility of macrophages to HIV-1 infection, as measured by their concentrations of extracellular p24 antigen and levels of intracellular HIV DNA by quantitative PCR. There was little change in levels of CCR1, CCR2b, and CCR5 RNAs. CCR3 RNA and surface antigen were undetectable throughout maturation of adherent monocytes over 10 days. CXCR4 RNA and membrane antigen were strongly expressed in newly adherent monocytes, but their levels declined at day 7. The amounts of CCR5 RNA remained stable, but the amounts of CCR5 antigen increased from undetectable to peak levels at day 7 and then declined slightly at day 10. Levels of susceptibility to laboratory (HIV-1BaL) and clinical strains of HIV-1 showed parallel kinetics, peaking at day 7 and then decreasing at days 10 to 14. The concordance of levels of HIV DNA and p24 antigen suggested that the changes in susceptibility with monocyte maturation were at or immediately after entry and correlated well with CCR5 expression and inversely with CXCR4 expression.

HIV infection of macrophages and pathogenesis of AIDS dementia complex: interaction of the host cell and viral genotype

AIDS dementia complex (ADC) develops in only a third of HIV-infected patients who progress to AIDS. Macrophages and microglial cells are the major cellular sites of productive HIV replication in brain. Using 11 blood isolates of HIV from asymptomatic patients there was marked variation in tropism and the level of productive infection in recently adherent monocytes and monocyte-derived macrophages cultured in vitro. However, less variation was seen with 19 blood isolates from advanced HIV infection and 11 postmortem tissue isolates from brain, cerebrospinal fluid, spleen, and lung. Newly adherent monocytes expressed CCR5 in all seven patients tested, consistent with their susceptibility to infection but not explaining the above variability. There is, also marked regional variability in neuropathology in the brain of patients with ADC. We have demonstrated that there was marked variation in the V3 sequences of HIV clones from different regions of the cortex of a patient with ADC, suggesting independent evolution of HIV replication in brain. Furthermore, production of the neurotoxin quinolinic acid from HIV-infected macrophages varied, depending on the host and source of HIV isolate. Hence variations in viral genotype, production by infected macrophages, and subsequent toxin production may contribute to the variability in neuropathology between individuals and between different regions of the brain in the same individual.