Ayman Al-Dharrab

Influence of denture adhesives on occlusion and disocclusion times

STATEMENT OF PROBLEM The effectiveness of adhesives in enhancing several functional aspects of complete denture performance has been well established. The direct influence of adhesives on occlusal contact simultaneity has not yet been investigated. PURPOSE The purpose of this crossover clinical trial was to evaluate quantitatively the influence of adhesives on occlusal balance by recording timed occlusal contacts; namely occlusion time (OT) and disocclusion time during right (DT-right) and left (DT-left) excursions by using computerized occlusal analysis. MATERIAL AND METHODS A crossover clinical trial was adopted. Assessments were carried out while participants (n=49) wore their dentures first without then with adhesives. Computerized occlusal analysis using the T-Scan III system was conducted to perform baseline computer-guided occlusal adjustment for conventionally fabricated dentures. Retention and stability assessment using the modified Kapur index and recording of OT and DT-right and DT-left values using the T-Scan III were subsequently carried out for all dentures, first without adhesives and then after application of adhesive. All T-Scan procedures were carried out by the same clinician. Wilcoxon signed-rank test was used to analyze the Kapur index scores and occlusal parameters (α=.05). RESULTS Stability and retention of conventional dentures ranged initially from good to very good. However, adhesive application resulted in significant improvement (P<.001) in stability and retention and a significant decrease in duration of all occlusal parameters (OT [P=.003], DT-right [P=.003], and DT-left [P=.008]). CONCLUSIONS Adhesives significantly decreased OT and DT durations in initially well-fitting complete dentures with fairly well balanced occlusion, and further enhanced denture stability and occlusal contact simultaneity.

TRAP-positive osteoclast precursors mediate ROS/NO-dependent bactericidal activity via TLR4.

Osteoclastogenesis was induced by RANKL stimulation in mouse monocytes to examine the possible bactericidal function of osteoclast precursors (OCp) and mature osteoclasts (OCm) relative to their production of NO and ROS. Tartrate-resistant acid phosphatase (TRAP)-positive OCp, but few or no OCm, phagocytized and killed Escherichia coli in association with the production of reactive oxygen species (ROS) and nitric oxide (NO). Phagocytosis of E. coli and production of ROS and NO were significantly lower in TRAP+ OCp derived from Toll-like receptor (TLR)-4 KO mice than that derived from wild-type (WT) or TLR2-KO mice. Interestingly, after phagocytosis, TRAP+ OCp derived from wild-type and TLR2-KO mice did not differentiate into OCm, even with continuous exposure to RANKL. In contrast, E. coli-phagocytized TRAP+ OCp from TLR4-KO mice could differentiate into OCm. Importantly, neither NO nor ROS produced by TRAP+ OCp appeared to be engaged in phagocytosis-induced suppression of osteoclastogenesis. These results suggested that TLR4 signaling not only induces ROS and NO production to kill phagocytized bacteria, but also interrupts OCm differentiation. Thus, it can be concluded that TRAP+ OCp, but not OCm, can mediate bactericidal activity via phagocytosis accompanied by the production of ROS and NO via TLR4-associated reprograming toward phagocytic cell type.

A novel computational analysis of computer milled zirconium implant abutment head design under reinforced implant supported overdenture

During the past few decades, unalloyed titanium has been extensively used as a material of dental implant-supported restorations but it cause gingival discoloration and unnatural appearance of the surrounding soft tissue. Currently, yttrium oxide partially-stabilized zirconia (Y-TZP) is a ceramic of special interest because of its superior mechanical properties. This study was carried out with four one piece zirconium implants embedded on a standard acrylic resin mandibular edentulous model, the abutment of zirconium implant was classified into two designs and then laboratory test was applied with proposed biting force (sensor (BS) and a bidirectional transmit-receive module. Our study concluded that the use of one piece Zirconium implant with box or parallel shape abutment head in implant supported over-denture without a need of cement, screws or plastics or metal housing for attachment in other types of implant had a superior results and easier maintenance and repair of the prosthesis if any complications occur.

Phosphoglycerol dihydroceramide, a distinctive ceramide produced by Porphyromonas gingivalis, promotes RANKL-induced osteoclastogenesis by acting on non-muscle myosin II-A (Myh9), an osteoclast cell fusion regulatory factor

Among several virulence factors produced by the periodontal pathogen Porphyromonas gingivalis (Pg), a recently identified novel class of dihydroceramide lipids that contains a long acyl-chain has the potential to play a pathogenic role in periodontitis because of its higher level of tissue penetration compared to other lipid classes produced by Pg. However, the possible impact of Pg ceramides on osteoclastogenesis is largely unknown. In the present study, we report that the phosphoglycerol dihydroceramide (PGDHC) isolated from Pg enhanced osteoclastogenesis in vitro and in vivo. Using RAW264.7 cells, in vitro assays indicated that PGDHC can promote RANKL-induced osteoclastogenesis by generating remarkably larger TRAP+ multinuclear osteoclasts compared to Pg LPS in a TLR2/4-independent manner. According to fluorescent confocal microscopy, co-localization of non-muscle myosin II-A (Myh9) and PGDHC was observed in the cytoplasm of osteoclasts, indicating the membrane-permeability of PGDHC. Loss- and gain-of-function assays using RNAi-based Myh9 gene silencing, as well as overexpression of the Myh9 gene, in RAW264.7 cells showed that interaction of PGDHC with Myh9 enhances RANKL-induced osteoclastogenesis. It was also demonstrated that PGDHC can upregulate the expression of dendritic cell-specific transmembrane protein (DC-STAMP), an important osteoclast fusogen, through signaling that involves Rac1, suggesting that interaction of PGDHC with Myh9 can elicit the cell signal that promotes osteoclast cell fusion. Taken together, our data indicated that PGDHC is a Pg-derived, cell-permeable ceramide that possesses a unique property of promoting osteoclastogenesis via interaction with Myh9 which, in turn, activates a Rac1/DC-STAMP pathway for upregulation of osteoclast cell fusion.

A novel method of sampling gingival crevicular fluid from a mouse model of periodontitis.

Using a mouse model of silk ligature-induced periodontal disease (PD), we report a novel method of sampling mouse gingival crevicular fluid (GCF) to evaluate the time-dependent secretion patterns of bone resorption-related cytokines. GCF is a serum transudate containing host-derived biomarkers which can represent cellular response in the periodontium. As such, human clinical evaluations of PD status rely on sampling this critical secretion. At the same time, a method of sampling GCF from mice is absent, hindering the translational value of mouse models of PD. Therefore, we herein report a novel method of sampling GCF from a mouse model of periodontitis, involving a series of easy steps. First, the original ligature used for induction of PD was removed, and a fresh ligature for sampling GCF was placed in the gingival crevice for 10min. Immediately afterwards, the volume of GCF collected in the sampling ligature was measured using a high precision weighing balance. The sampling ligature containing GCF was then immersed in a solution of PBS-Tween 20 and subjected to ELISA. This enabled us to monitor the volume of GCF and detect time-dependent changes in the expression of such cytokines as IL-1b, TNF-α, IL-6, RANKL, and OPG associated with the levels of alveolar bone loss, as reflected in GCF collected from a mouse model of PD. Therefore, this novel GCF sampling method can be used to measure various cytokines in GCF relative to the dynamic changes in periodontal bone loss induced in a mouse model of PD.

Correlation of psychomotor skills and didactic performance among dental students in Saudi Arabia.

Objectives The objective of this study is to investigate the correlation between the psychomotor skills and the academic performance of dental students. Methods Didactic and preclinical scores were collected for students who graduated from the Faculty of Dentistry, King Abdulaziz University, Jeddah, Saudi Arabia, in 2011. Three courses (Dental Anatomy, Removable Prosthodontic Denture, and Orthodontics) were selected. Correlations comparing didactic and practical scores were done for the total samples, then for the males and females separately. Results There was no significant correlation between the practical and didactic scores for the three courses for the total sample. There was a significant correlation between all three subjects in the didactic scores. For females, the results showed that there was only a significant correlation between the practical and didactic scores for Dental Anatomy. For males, no correlation was observed between the practical and didactic scores for all subjects. Conclusion In the present sample, didactic performance did not correlate well with the students’ psychomotor performance.

Surface roughness and internal porosity of partial removable dental prosthesis frameworks fabricated from conventional wax and light-polymerized patterns: A comparative study

STATEMENT OF PROBLEM Surface roughness and internal porosity are 2 potential risk factors that threaten the biocompatibility and long-term mechanical stability of cast partial removable dental prostheses frameworks. PURPOSE The purpose of this study was to investigate the influence of the material, of conventional wax patterns, and the recently introduced light-polymerized patterns on the initial surface roughness and internal porosity of the cobalt-chromium castings of partial removable dental prostheses. MATERIAL AND METHODS Twenty-eight identical partial removable dental prosthesis frameworks were fabricated on a cast of a maxillary Kennedy Class III modification 1 partially edentulous patient. Fourteen frameworks were fabricated from each pattern material. The initial surface roughness, Ra (μm), of the resultant castings was measured with a profilometer. Radiographs of the castings were made on dental occlusal films with a dental x-ray unit with the following exposure conditions: tube voltage 70 kV; exposure time 1.0 seconds; tube current 7 mA; and source-film distance 35 cm. The number and size of porosities in the 3 main components (clasp units, major connectors, denture base meshwork) were assessed. Statistical analysis was conducted with the independent sample t test for surface roughness and the Mann Whitney test for internal porosity (α=.05). RESULTS The statistical analysis of mean surface roughness and internal porosity revealed no significant difference between the 2 groups. CONCLUSIONS The surface roughness and internal porosity of frameworks fabricated from conventional wax and Liwa patterns were comparable, with no significant differences between the 2 pattern materials.

The Effect of Different Storage Conditions on the Physical Properties of Pigmented Medical Grade I Silicone Maxillofacial Material

Objective. This study aimed to evaluate the effect of different storage solutions that simulate acidic, alkaline, and sebum conditiions on the physical properties of pigmented (colorant elastomer) cosmesil M511 maxillofacial prosthetic material. Materials and Methods. Sixty specimens were prepared according to the manufacturers instructions and were tested before and after immersion of different storage conditions for six months at 37 °C. The following tests were performed: color changes (group I), solution absorption (group II), surface roughness (group III), and scanning electron microscopy (group IV). Results. There were no significant changes observed in the color and solution absorption tests while surface roughness revealed significant difference between control group and other testing storage medium groups, and this result was supported by SEM analysis that revealed limited surface changes. Conclusions. Cosmaseil material is an acceptable cross-linked formulation that withstands storage in different solutions with variable pH. The addition of pigment cannot vary the physical properties of these materials. Surface roughness test as well as SEM microscopic study showed moderate changes indicating a limited effect on the surface of the material.

OC-STAMP promotes osteoclast fusion for pathogenic bone resorption in periodontitis via up-regulation of permissive fusogen CD9

Cell fusion‐mediated formation of multinuclear osteoclasts (OCs) plays a key role in bone resorption. It is reported that 2 unique OC‐specific fusogens [i.e., OC‐stimulatory transmembrane protein (OC‐STAMP) and dendritic cell–specific transmembrane protein (DC‐STAMP)], and permissive fusogen CD9, are involved in OC fusion. In contrast to DC‐STAMP‐knockout (KO) mice, which show the osteopetrotic phenotype, OC‐STAMP‐KO mice show no difference in systemic bone mineral density. Nonetheless, according to the ligature‐induced periodontitis model, significantly lower level of bone resorption was found in OC‐STAMP‐KO mice compared to WT mice. Anti‐OC‐STAMP‐neutralizing mAb down‐modulated in vitro: 1) the emergence of large multinuclear tartrate‐ resistant acid phosphatase‐positive cells, 2) pit formation, and 3) mRNA and protein expression of CD9, but not DC‐STAMP, in receptor activator of NF‐κB ligand (RANKL)‐stimulated OC precursor cells (OCps). While anti–DC‐STAMP‐mAb also down‐regulated RANKL‐induced osteoclastogenesis in vitro, it had no effect on CD9 expression. In our mouse model, systemic administration of anti–OC‐STAMP‐mAb suppressed the expression of CD9 mRNA, but not DC‐STAMP mRNA, in periodontal tissue, along with diminished alveolar bone loss and reduced emergence of CD9+ OCps and tartrate‐resistant acid phosphatase‐positive multinuclear OCs. The present study demonstrated that OC‐STAMP partners CD9 to promote periodontal bone destruction by up‐regulation of fusion during osteoclastogenesis, suggesting that anti–OC‐STAMP‐mAb may lead to the development of a novel therapeutic regimen for periodontitis.—Ishii, T., Ruiz‐Torruella, M., Ikeda, A., Shindo, S., Movila, A., Mawardi, H., Albassam, A., Kayal, R. A., Al‐Dharrab, A. A., Egashira, K., Wisitrasameewong, W., Yamamoto, K., Mira, A. I., Sueishi, K., Han, X., Taubman, M. A., Miyamoto, T., Kawai, T. OC‐STAMP promotes osteoclast fusion for pathogenic bone resorption in periodontitis via up‐regulation of permissive fusogen CD9. FASEB J. 32, 4016–4030 (2018). www.fasebj.org

Radiographic evaluation of dental age maturity in 3–17-years-old saudi children as an indicator of chronological age

Objective: This study was aimed to evaluate the dental age in Saudi children from panoramic radiographs using the Demirjian method to estimate their chronological age. Materials And Methods: This retrospective cross-sectional study consisted of 1902 panoramic radiographs of 955 boys and 947 girls between the ages of 3–17 years. All children were placed in the age group closest to their chronological age. The dental age was scored on all seven left mandibular teeth by calibrated examiners. Bivariate analyses using the t-test and Pearson correlation were performed. Results: There was significant difference in both boys and girls in all the age groups between their chronological age and dental age. Even though there was a slight overestimation in boys in some age groups and slight underestimation in girls in some groups, correlation analysis showed that there was a highly significant correlation between the chronological age and dental age for both boys (r2 = 0.96, P < 0.001) and girls (r2 = 0.98, P < 0.001). Moreover, correlation analyses for each age group showed a significant correlation between the chronological age and the dental age, using the Demirjian method, in most age groups (P < 0.01). When comparing the maturation score between boys and girls, the Students t-test showed that there were no statistical differences between boys and girls in most age groups. Conclusion: Saudi boys and girls living in the western region of Saudi Arabia exhibited similar pattern of dental development when compared to the Demirjian method. Hence, the Demirjian method could be used as reference in children from the western region of Saudi Arabia.