Objective To study the effect of using different cement types under pediatric stainless-steel crown (SSC) around mandibular second primary molar using three-dimensional (3D) finite element analysis. Materials and Methods A 3D finite element model was built for pediatric mandibular molar by laser scanning of natural extracted tooth. Four types of cement (zinc phosphate, glass ionomer, resin-modified glass ionomer, and resin) of 200 μm layers thickness were tested under a stainless-steel crown of 130-μm thickness. Twelve case studies were reported within this research, as the applied load of 330 N was tested with three angulations: vertical, oblique at 45°, and laterally. Results Linear static stress analysis was performed. The resultant stresses and deformations' distribution patterns did not change with cement type, while the values were altered. All deformations and stresses were found within the normal range. Conclusions Analysis results indicated that using stiffer cement material increases tooth structure stresses and reduces crown body stresses and deformations, while bone was nearly insensitive to cement type.

Background: Pulpal involvement, secondary to dental caries, is not uncommon and is a challenging task for pediatric dentists. Morphological differences in root canal of deciduous teeth increases the complexity of management. The aim of this study was to compare two rotary file systems and hand instrumentation for root canal preparation in regard to canal transportation, centering ability ratio, and dentin thickness using cone-beam computed tomography (CBCT). Methods: A total of 72 canals from 24 freshly extracted mandibular deciduous second molars were divided into a set of 8 teeth, then prepared using 2 rotary files systems: the Kedo-S pediatric file system (Group A) and Pro AF Baby Gold file system (Group B) were compared to hand instrumentation (Group C). CBCT scans before and after root canal preparation were used to evaluate tested parameters. Instrumentation time for all three techniques was also measured using a chronometer. Results: Although rotary file systems have shown superior results in root canal preparation as compared to hand instrumentation, no significant differences were observed between all the groups for canal transportation and dentin thickness at all three levels of prepared canals. A comparison of centering ability ratio between all the groups was found to be statistically significant only at the cervical level. A significant difference was observed between hand instrumentation using K-files (117.3 s) and both rotary systems (Kedo-S (81 s) and Pro AF Baby Gold (81.5 s)) in terms of canal preparation time (P < 0.001). Conclusions: Both tested rotary systems and hand instrumentation demonstrated comparable canal preparation results, with differences that were statistically non-significant in most tested parameters, without shaping errors. However, both the rotary systems were more efficient and faster than hand instrumentation.

AIM: The aim of the current in vitro study was to evaluate the changes in surface roughness of bulk fill composites after simulated toothbrushing with different dentifrices. MATERIALS AND METHODS: Three types of bulk fill resin composites were used in this study; 27 specimens of each composite resin were randomly divided into three main groups (n = 9). Each main group was further subdivided into three subgroups (n = 3). Each group was subjected to simulated toothbrushing with three different dentifrices. One-way analysis of variance was used to evaluate the effect of brushing using dentifrices on the surface roughness of each type of composite resin, followed by Tukey’s test at a significance level of p ≤ 0.5%. RESULTS: Results revealed that different effects on composite surface roughness were detected after simulating toothbrushing with different dentifrices. Lacalut toothpaste abrades more with Filtek Bulk Fill, Tetric N-Ceram then Bulk Fill SDR. Crest 3D toothpaste abrades more with Tetric N-Ceram, Bulk Fill SDR then Filtek Bulk Fill. BlanX toothpaste abrades more with Tetric N-Ceram, Bulk Fill SDR then Filtek Bulk Fill. CONCLUSION: Chemical composition of both resin composites and dentifrices plays an important role in influencing the degree of surface roughness of bulk fill composite resin restorations.

Background: glass ionomer is one of the most frequently used restorative materials for primary teeth restoration. It has been in use for more than 30 years. Their restoration usefulness is preferential compared to other restorations due to their fluoride release and recharge, chemical adhesion to the structure of the dentin and their range of uses. Increasing the antibacterial efficacy of restorative materials is one of the primary goals to decrease the incidence of recurrent caries. Chlorhexidine is the gold standard antibacterial agent in dentistry. Objectives: the objective of this study is to evaluate the antibacterial effect of Chlorhexidine incorporated with glass ionomer on streptococcus mutans. Methods: Thirty Children between ages ranged 6-9 years old were selected to participate in this study. Children with bilateral caries in lower second primary molars affecting the occlusal and proximal surfaces without pulpitis were included in the study. All cavities were divided into two groups; group (A) restored with Glass Ionomer and group (B) restored with Glass Ionomer Chlorhexidine mixture. The sound proximal surfaces in all cavitated teeth acted as a control. After one month, two months and three months’ plaque samples were obtained and streptococcus mutans counts were calculated. Results: The number of SM taken from sound proximal surfaces for all groups were not changed significantly in whole periods of study. At the all-time interval, the mean log10 of SM in CHX group was lower than GI group and the difference was statistically significant. There is a significant difference in the mean log10 of SM in CHX group between the 1St month and the 3rd month. Conclusion: The growth of SM was found to be higher in the sound tooth than in GI groups and in GI group was higher than in CHX- GI mixture up to three months.