There is a lack of evidence about the comparative effectiveness of the different denture cleaning methods considered in this review. Few well designed RCTs were found. Future research should focus on comparisons between mechanical and chemical methods; the assessment of the association of methods, primary variables and costs should also receive future attention.

The cement-retained restorations showed significantly higher mean fracture loads than the restorations having screw-access openings in their occlusal surface. The position of the screw-access hole within the occlusal surface did not significantly affect the porcelain fracture resistance.

Introduction:Caries is associated with high counts of mutans streptococci (MS), lactobacillus (LB), and a low saliva buffering capacity (BC). No study using odds ratios (OR) has correlated caries and these factors and no similar study has been done in Saudi Arabia before. Objectives: To determine: The prevalence of caries, the number of colony forming units (CFUs) of MS and LB, the saliva buffering capacity (BC) and the relationship between these factors.Materials and Methods:This was an analytical cross sectional study on children from Madinah. Caries was recorded using dmft/DMFT (decayed, missing, filled teeth). The scores for MS and LB and the BC of saliva was calculated using the Caries Risk Test (CRT)®.Results:A total of 316 students were examined; two-thirds (62%) were female and 25% were caries free. Saliva was collected from 235 participants and the majority had high MS and LB scores (66 and 71%, respectively) while 25% had a low saliva BC. The odds for those who had high LB and MS CFUs, were 9 and 4 times more at risk to developing dental caries and those with a low BC had significantly more caries (P = 0.03). The likelihood for those having severe caries and high counts of LB and MS was 25 (P < 0.01) and 6 (P = 0.042) times greater, respectively, compared to those with no or mild caries. Those with multiple risk factors were more likely to have caries compared to those with single or no risk factors present.Conclusions:The prevalence of caries was relatively high and many respondents had greater than 105 CFUs/ml of MS and LB. Almost all with a low BC had severe caries. There was a strong correlation between high MS, high LB, and low BC and the high prevalence of caries; hence the combination of these factors could be confidently used to predict caries in this population.

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Metal-ceramic restorations are widely used in dentistry with a high degree of general success. However, fracture of these restorations does occur and usually frustrates both the dentist and the patient. Objective: This literature review discusses the factors that may lead to the fracture of these restorations whether they are tooth-supported or implant-supported with the aim of making dentists and technicians aware of these factors to avoid them. Factors reviewed include: technical factors, dentist-related factors, inherent material properties, direction, magnitude and frequency of applied loads, environmental factors, screw-retained implant-supported restorations, and posterior cantilevered prostheses. Material and Methods: A netbased search in "Pubmed" was performed and combined with a manual search. The search was limited to articles written in English. Conclusions: the published literature revealed that the factors predisposing to fracture of metal-ceramic restorations may be related to the technician, dentist, patient, environment, design of the restoration, or to inherent structure of ceramics and others. However, if the dentist and technician understand these factors and respect the physical characteristics of the materials, most of those are avoidable.

Purpose: To estimate the fatigue life of 3‐unit molar fixed partial dentures (FPDs) made from two different monolithic ceramic systems, zirconia cercon (ZC) and lithium disilicate (LD). The effect of the connector size on the fatigue resistance of the monolithic FPD was also investigated. Methods: Two models for the FPDs were built, a 3‐unit all‐ceramic and a porcelain‐fused‐to‐metal. The porcelain–fused‐to‐metal FPD model was used as the control. Actual 3‐unit FPDs (replacing the second lower premolar) were constructed using a computer aided design and computer‐aided manufacturing (CAD‐CAM) system. Finite element analysis (FEA) was executed. A hemispherical indenter was used to simulate occlusal load. The occlusal load phase of the chewing cycle was applied at the premolar pontic. Results: The failure location for the monolithic FPD was always located at the distal connector. Connector size played a key role in determining the long‐term survival of the prosthesis. The fatigue resistance was predicted to be 670 N for the ZC with a connector size 4 × 3 mm, while it was only 226 N for LD. As for porcelain‐fused‐to‐metal (PFM), FEA predicts that fatigue resistance can reach up to 770 N. Under the cyclic load of 670 N, the fatigue life for the zirconia FPD with connector size 4 × 3 mm was 2.23 × 106 cycles while it survived only 3.1 × 105 cycles when the connector was reduced to 3.5 × 2.5 mm. The angle of the oblique load has a significant effect on the stress distribution. Conclusion: 3‐unit monolithic FPDs made of ZC have superior fatigue performance compared to those made of LD. The fatigue life of the zirconia FPD was about three times longer than that made of LD with a connector size of 4 mm × 3 mm. The survival rates of ZC FPDs are comparable to porcelain‐fused‐to‐metal. A significant reduction in fatigue strength is predicted for reduced connector size. Therefore, it is necessary to establish general guidelines for the minimum connector size.

Monolithic zirconia and hybrid ceramic restorations have been widely used in the last decade for both anterior and posterior dental restorations. However, their use lacks sufficient scientific evidence in most cases, as the expeditious manufacturing of these versatile ceramic materials exceeds the limits of in vitro and/or in vivo validation. This study aimed to evaluate and compare the mechanical properties (flexural strength, fracture toughness, Vickers hardness, and brittleness index) of three CAD-CAM monolithic multilayer zirconia ceramics (GNX—Ceramill Zolid® Gen-X, ZCP—IPS e.max® ZirCAD, and UPC—Upcera® Esthetic Explore Prime) and one CAD-CAM monolithic multilayer polymer-infiltrated hybrid ceramic (ENM—Vita® Enamic) with a CAD-CAM monolithic lithium disilicate ceramic as a control (EMX —IPS e.max® CAD). A total of 160 discs (GNX = 32, ZCP = 32, UPC = 32, ENM = 32, and EMX = 32) were cut, polished, and fully sintered (except for the ENM). Half of the samples for each group were subjected to hydrothermal aging. Descriptive analysis and ANOVA tests were used to compare the groups. The zirconia groups showed significantly higher mechanical properties than the EMX group for both the non-aged and aged samples (p < 0.05). The ENM group showed the lowest brittleness index, while EMX showed the highest. The mechanical properties of monolithic multilayer zirconia ceramics were generally better than those of monolithic multilayer polymer-infiltrated hybrid ceramic and lithium disilicate ceramic. All groups showed, to some extent, a change in their mechanical properties after aging, with the ENM being the most affected.

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