Choice of Restorative Materials for Direct Posterior Restorations among Undergraduate Saudi College Students

Background: The most common restorative materials used in dentistry are amalgam and composite. Amalgam is a controversial material owing to its mercury toxicity. With recent advances in the properties of composite materials, there has been a shift towards its use. Objectives: The aim of this study was to understand the perceptions of undergraduate dental students in a northern Saudi Arabian dental school about the choice of restorative materials for restoring posterior teeth. Methodology: The study included undergraduate students studying in 4th and 5th year dental program in College of Dentistry, Jouf University. A four-item questionnaire with 18 close-ended questions was developed by the investigators, which were hand delivered to all the students. Data analysis is presented through tables and descriptive methods. Results: A total of 98 (out of 131) undergraduate students participated in this study. Overall, the students reported a significantly strong influence of the type of restorative materials in relation to the cavity size and margin of the restorations along with the esthetics factor(p<0.05). There was slight influence on the student’s choice because of the instructor's influence, whereas the students felt they were knowledgeable and had appropriate training to use either amalgam or composite. The study also found that patient’s preference had a strong influence on choosing composite material. The students were mostly not influenced while choosing the material as far as the safety of it was concerned. However, the patient’s influence was slight when it came to the choice of the material. A significant difference was noted among the students when it came to pregnancy-related safety concerns where the choice of material was not influenced by either amalgam or composite (p=.002). Conclusion: The undergraduate dental students at College of Dentistry, Jouf University are comfortable in using both amalgam and composite as a posterior restorative material. They are knowledgeable about both the materials and are adequately trained to use either one.

In-vivo-wear in composite and ceramic full mouth rehabilitations over 3 years

The aim of this study was to quantify and to compare the wear rates of premolar (PM) and molar (M) restorations of lithium disilicate ceramic (LS2) and an experimental CAD/CAM polymer (COMP) in cases of complex rehabilitations with changes in vertical dimension of occlusion (VDO). Twelve patients with severe tooth wear underwent prosthetic rehabilitation, restoring the VDO with antagonistic occlusal coverage restorations either out of LS2 (n = 6 patients, n = 16 posterior restorations/patient; N = 96 restorations/year) or COMP (n = 6 patients; n = 16 posterior restorations/patient; N = 96 restorations/year). Data was obtained by digitalization of plaster casts with a laboratory scanner at annual recalls (350 ± 86 days; 755 ± 92 days; 1102 ± 97 days). Each annual recall dataset of premolar and molar restorations (N = 192) was overlaid individually with the corresponding baseline dataset using an iterative best-fit method. Mean vertical loss of the occlusal contact areas (OCAs) was calculated for each restoration and recall time. For LS2 restorations, the mean wear rate per month over 1 year was 7.5 ± 3.4 μm (PM), 7.8 ± 2.0 μm (M), over 2 years 3.8 ± 1.6 µm (PM), 4.4 ± 1.5 µm (M), over 3 years 2.8 ± 1.3 µm (PM), 3.4 ± 1.7 µm (M). For COMP restorations, the mean wear rate per month over 1 year was 15.5 ± 8.9 μm (PM), 28.5 ± 20.2 μm (M), over 2 years 9.2 ± 5.9 µm (PM), 16.7 ± 14.9 µm (M), over 3 years 8.6 ± 5.3 µm (PM), 9.5 ± 8.0 µm (M). Three COMP restorations fractured after two years and therefore were not considered in the 3-year results. The wear rates in the LS2 group showed significant differences between premolars and molars restorations (p = 0.041; p = 0.023; p = 0.045). The wear rates in COMP group differed significantly between premolars and molars only in the first two years (p < 0.0001; p = 0.007). COMP restorations show much higher wear rates compared to LS2. The presented results suggest that with increasing time in situ, the monthly wear rates for both materials decreased over time. On the basis of this limited dataset, both LS2 and COMP restorations show reasonable clinical wear rates after 3 years follow-up. Wear of COMP restorations was higher, however prosthodontic treatment was less invasive. LS2 showed less wear, yet tooth preparation was necessary. Clinicians should balance well between necessary preparation invasiveness and long-term occlusal stability in patients with worn dentitions.

The Ability of Dental Practitioners to Light-Cure Simulated Restorations

Clinical Relevance Using a patient simulator, dental professionals were tested to determine their ability to light-polymerize simulated restorations in their dental practice. After receiving specific instructions and training using the simulator, their ability to deliver sufficient light to polymerize restorations was significantly and substantially improved. SUMMARY Objectives: To determine the ability of dental professionals to deliver a radiant exposure of at least six J/cm2 in 10 seconds to simulated restorations. Methods and Materials: The study initially examined 113 light-emitting-diode (LED) light polymerization units (LPUs) used in dental offices to determine if they could deliver at least 6 J/cm2 radiant exposure (RE) in 10s. This assessment was completed by using a laboratory-grade light measuring device (checkMARC, BlueLight Analytics, Halifax, NS, Canada). The participating dental professionals whose LPUs could deliver 6 J/cm2 then used their own LPU to light-cure simulated anterior and posterior restorations in the MARC Patient Simulator (BlueLight Analytics). They then received specific instructions and were retested using the same LPUs. Data were statistically analyzed with a series of one-way analysis of variance (ANOVA), two-way ANOVA, paired-samples t-tests, Fisher post hoc multiple comparison tests, and McNemar tests with a preset alpha of 0.05 (SPSS Inc). Results: Ten (8.8%) LPUs could not deliver the required RE to the checkMARC in 10s and were eliminated from the study. For the anterior restoration, most dental practitioners (87.3%) could deliver at least 6 J/cm2 before instructions. After receiving additional light-curing instructions, only two (1.9%) participants were unable to deliver 6 J/cm2 to the anterior location. At the posterior location, only 55.3% (57) participants could deliver at least 6 J/cm2 before the instructions. After receiving these instructions, an additional 32 participants delivered at least 6 J/cm2. Overall, after receiving instructions on how to use the LPU correctly, the participants improved the amount of RE they delivered to anterior and posterior restorations by 22.5% and 30%, respectively. Conclusion: This study revealed that at the baseline, 44.7% of participating dental professionals failed to deliver 6 J/cm2 in 10s to the posterior simulated restoration when using their own LPU.

Effect of Shrinking and No Shrinking Dentine and Enamel Replacing Materials in Posterior Restoration: A 3D-FEA Study

The aim of the present study was to investigate the effect of shrinking and no shrinking dental filling materials combination in posterior restorations under the combined effects of polymerization shrinkage and occlusal load by means of 3D Finite Elements Analysis. Six computer-generated and restored class I or class II cavities models of a lower molar were designed in the CAD software and evaluated according to the cavity and restorative procedure. Different shrinking and no shrinking adhesive materials combination with diverse Young’s modulus were considered. A food bolus was modeled on the occlusal surface replicating the chewing load using static linear analyses Polymerization shrinkage was simulated for the shrinking different restorative materials. The maximum principal stress was selected as analysis criteria. All models exhibited higher stresses along the dentine restoration interfaces with different magnitude and a similar stress trend along enamel restoration interface. Stress values up to 22 MPa and 19 MPa were recorded in the enamel and restoration, respectively. The use of elastic not shrinking material layer in combination with bulk fill composite reduced the stress magnitude in dentine and enamel to replace dental tissues. Class I and class II posterior cavities adhesively restored with shrinking filling material’s combination showed the most unfavorable stress concentrations and the multilayer technique is a promising restorative alternative in posterior adhesive restorations when deep dentin and enamel volumes are missing.

Influence of short-fiber composite base on fracture behavior of direct and indirect restorations

Objectives The aim was to examine the influence of short-fiber composite (SFC) core on the fracture-behavior of different types of indirect posterior restorations. In addition, the effect of thickness ratio of SFC-core to the thickness of the veneering conventional composite (PFC) on fracture-behavior of bi-structured composite restorations was evaluated. Materials and methods MOD cavities with removed palatal cusps were prepared on 90 intact molars. Five groups of direct overlay restorations (n = 10/group) were fabricated having a SFC-core (everX Flow) with various thicknesses (0, 1, 2, 3, 4 mm) and layer of surface PFC (G-aenial Anterior), remaining the thickness of the bi-structure restoration to be 5 mm. Four groups of CAD/CAM-made restorations (Cerasmart 270 and e-max CAD) were fabricated either with 2-mm layer of SFC-core or without fiber reinforcement. Intact teeth (n = 10) were used as control group. Restorations were statically loaded until fracture. Fracture patterns were evaluated visually. Data were analyzed using ANOVA (p = 0.05). Results With indirect overlay restorations, no statistically significant differences (p > 0.05) were observed in the load-bearing capacities between restorations reinforced by 2-mm SFC-core (bi-structured) and those fabricated from plain restorative materials. ANOVA displayed that direct overlay restorations made from 4-mm layer thickness of SFC-core had significantly higher load-bearing capacities (3050 ± 574 N) (p < 0.05) among all the groups tested. Conclusions Restorations (direct/indirect) combining SFC-core and a surface layer of conventional material demonstrated encouraging achievement in reference to fracture behavior. Clinical relevance The use of flowable short-fiber composite as reinforcing base with large direct and indirect restorations may result in more repairable failure.