Nour A. Habib

Secondary caries is one of the main reasons for the clinical failure in dental restorations. Therefore, it is preferable for restorative materials to possess antibacterial properties, which support a longlasting restoration. The present in vitro study aimed to evaluate the effect of both the polyamidoamine (PAMAM) liquid and bioactive glass (BAG) powder added to glass ionomer cements (GICs) on their antibacterial properties. Polyamidoamine was prepared and characterized. Four groups were distinguished, as follows: GI - samples of commercially available GIC (control); GII - samples of GIC mixed with PAMAM; GIII - samples of GIC mixed with BAG; and GIV - samples of GIC mixed with PAMAM and BAG.The biofilm assessment test was conducted using a colony forming unit (CFU) count, and the ion release test was used to quantify the amount of released silica (Si), calcium (Ca), phosphorus (Ph), and sodium (Na) ions in mg/L. Thirty-six samples were prepared for each test. Furthermore, the pH of the soaking solution was measured for each sample in the ion release test. The parametric data was examined using one-way analysis of variance (ANOVA) followed by Tukey's post-hoc test. The biofilm assessment test revealed a significant reduction in the recovered Streptococcus mutans counts in all modified groups compared to the control group (p < 0.05). Also, the ion release test demonstrated a significant increase in the release of Si and Na ions for all modified groups compared to the control group (p < 0.05). The modification of GICs with PAMAM and BAG enhances their antibacterial properties.

Ceramic thickness and technicians’ manipulative variables are critical factors affecting the resultant shade of dental ceramo-metallic restorations. This study investigated the effect of the following variables on shade duplication of ceramo-metallic specimens: (a) ceramic thickness; (b) differences between several technicians (inter-technician variability); and (c) the ability of each technician to repeat the resultant shade (intra-technician variability). Ninety ceramo-metallic specimens were prepared and divided into three main groups (n = 30/gp) according to the different technicians who built up the veneering ceramic of the specimens. Each group was further subdivided into three subgroups (n = 10/subgroup) according to the thickness of the ceramic (1, 1.5, and 2 mm built over a 0.5 mm-thick metal substructure). Three different technicians were asked to follow the same protocol as regards the same ceramic batch (Shade 3M2, Vita VM13, Zahnfabrik, Germany), firing temperature, and number of firing cycles. Meanwhile, each technician followed his own protocol with regard to other ceramic manipulative variables. The duplicated shades of the specimens were investigated using the Vita Easyshade spectrophotometer by using the verify shade mode. Color difference (∆E) values were calculated between the target shade (3M2) and the duplicated shades of the specimens automatically by the Vita Easyshade spectrophotometer (Vita, Zahnfabrik, Germany). The effect of ceramic thickness and inter- and intra-technician variability on the duplication of the target shade was investigated. The results showed that the effect of ceramic thickness on the duplicated shades depended on inter-technician variability. High inter-technician variability (∆E = 2–6.4) was noticed in contrast to low intra-technician variability (∆E = 0.2–1.5). It could be concluded that proper shade-duplication of ceramo-metallic restoration was a cumulative technique intimately related to manipulative variables and ceramic thickness.

Zirconia is a high-strength ceramic material that expands the design and application possibilities for all-ceramic restorations and dental implants. To enhance the bonding of zirconia restorations to tooth substrates and the osseointegration of implants with the surrounding bone, the surface should be modified by surface treatment. Unfortunately, the effective treatment of sintered zirconia is difficult. Surface treatment for presintered zirconia may be less difficult; thus, the effectiveness of surface treatments of presintered zirconia was investigated herein. The zirconia specimens were randomly divided into eight groups: (1) control (untreated) and seven treated groups subjected to surface treatment (s.ttt.) in the presintered stage, followed by sintering: (2) s.ttt. 1: hydrofluoric acid (HF) gel left during sintering; (3) s.ttt. 2: HF gel washed before sintering; (4) s.ttt. 3: coated with nanosilica; (5) s.ttt. 4: coated with microsilica; (6) s.ttt. 5: coat followed by airborne-particle abrasion; (7) s.ttt. 6: coat followed by partial etching; and (8) s.ttt. 7: coat followed by total etching. The surface microstructure was examined using scanning electron microscopy (SEM) and the crystalline phase was identified using X-ray diffraction (XRD). Biaxial flexural strength was also tested. The results of SEM for s.ttt. 1 and 2 displayed irregular surfaces. S.ttt. 3 showed deeper penetration of the nanosilica into zirconia (27 µm) compared to the microsilica used in s.ttt. 4. S.ttt. 5 and 6 showed irregular coats. S.ttt. 7 showed intergranular pores. The XRD of s.ttt. 1, 2, and 3 revealed tetragonal zirconia as the control group. S.ttt. 4 and 5 showed cristobalite silica and tetragonal zirconia. S.ttt. 6 and 7 contained amorphous silica and tetragonal zirconia, while s.ttt. 7 also showed monoclinic zirconia. The highest flexural strength was for s.ttt. 4 (982.4 MPa), while the lowest was for s.ttt. 7 (386.6 MPa). There was no significant difference in the flexural strength between the control, s.ttt. 1, and 2 (846.3 MPa, 830.0 MPa, and 835 MPa, respectively). Compared to the control group, s.ttt. 3 had a lower flexural strength (634.1 MPa), while s.ttt. 5 and 6 had higher flexural strengths (863.1 MPa and 872.2 MPa, respectively). It can be concluded that the surface modification of presintered zirconia is a promising method as long as no phase transformation or deep subsurface penetration occurs.

Objectives: This study was conducted to create nanostructured surface titanium implants by anodic oxidation process aiming to bring out bioactivity and to assess the resultant bioactivity both in vitro and in vivo.Materials and Methods: An economic protocol was used to apply anodic spark discharge and create surface nanoporosities on grade II commercially pure titanium (cpTi). The in vitro investigation included morphology, surface chemical analysis, roughness and crystalline structure of titanium oxide (TiO₂) film prepared. Assessment of the bioactivity was carried out by immersing the specimens in simulate body fluid (SBF) and investigating the surface‐deposited layer. The in vivo investigation was conducted by surgically placing the anodized implants into rabbits tibia for different healing periods. Then biomechanical evaluation was performed to verify the effect of treatments on the interface resistance to shear force. Routine histological analysis was performed to evaluate the bone tissue reactions to anodized implants.Results: Anodization of titanium implants produced morphological changes, raised the percentage of oxygen in the TiO₂ layer, increased surface area and roughness of implants remarkably, and modified the crystallinity of the film. The in vitro assessments of bioactivity showed that a layer of calcium phosphate was precipitated on the titanium surfaces 7 days after soaking into SBF. The implant–bone interface resistance to shear force was enhanced at 2‐week healing period. This was confirmed by histological findings.Conclusion: Nanostructured surface titanium implants could be prepared by anodic oxidation with resultant accelerated bioactivity that may be recommended for early loading.

Clinical Relevance: Fiber inserts incorporated at the gingival floor of Class II composite restorations resulted in a significant reduction of microleakage scores as compared to restorations made without inserts. This may lead to a reduced incidence of recurrent caries.