The Effect of Various Preparation and Cementation Techniques of Dental Veneers on Periodontal Status: A Systematic Review and Meta-Analysis.

Dental veneers are widely used to restore or/and enhance dental aesthetics. However, it is not well understood how various veneer preparation and cementation methods affect periodontal health. To provide a quantitative estimate of the overall effect size of the intervention, this study was conducted to synthesize the available evidence on the impact of various dental veneer preparation and cementation methods on periodontal status. A thorough search strategy was implemented using Medical Subject Headings keywords and Boolean operators across various major databases, guided by the Preferred Reporting Items for Systematic Reviews and Meta-Analyses protocol. Nine papers were ultimately selected for inclusion in the review. Seven studies demonstrated a positive impact of dental veneers on overall periodontal health, while two studies reported a slight worsening. The forest plot analyses showed a somewhat protective effect of dental veneers on periodontal health, with odds ratio of 0.18 and relative risk of 0.34, suggesting that dental veneers may have a positive impact on overall periodontal health. The current study, with considerable heterogeneity among the studies, indicates that dental veneers are associated with an overall positive effect on the periodontal health. However, given the variations in study designs, sample sizes, and follow-up times, additional research may be required to confirm and generalize these results.

Fatigue Resistance of 3-Unit CAD-CAM Ceramic Fixed Partial Dentures: An FEA Study.

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.

Optical properties of CAD-CAM monolithic systems compared: three multi-layered zirconia and one lithium disilicate system.

OBJECTIVE: this in vitro investigation aims to evaluate and compare optical properties of three types of esthetic CAD-CAM monolithic multi-layered zirconia materials with a control (conventional lithium disilicate, IPS e. max CAD). METHODS: Four monolithic CAD-CAM ceramic materials were investigated: Ceramill Zolid® FX Multilayer (ZF), IPS e. max® ZirCAD MT Multi (ZM), Katana® STML (KS) and one lithium disilicate glass-ceramics as a control (IPS e. max® CAD LT; LC). A total of 72 (15 × 15 × 1 mm) samples were CAD CAM fabricated and sintered based on sample-size power calculations, and each material comprised 18 samples. The translucency and opalescence parameters with the contrast ratio were evaluated with a dental spectrophotometer over the backgrounds of black and white. The data were analyzed by ANOVA, then Bonferroni post hoc comparison test was made between groups. The statistical significance was set at p < 0.05. RESULTS: Zirconia materials revealed lower optical properties than the lithium disilicate control LC (P < 0.05). TP values ranged from 14.174 to 20.439. No differences were detected between the zirconia products in terms of TP and CR (P = 1.000). OP values ranged from 5.068 to 10.097. The lowest OP values were found statistically significant for ZF followed by KS and ZM (P = 1.000). LC had the highest TP and OP values, as well as the lowest CR (p < 0.05). CONCLUSIONS: The optical properties of monolithic zirconia systems tested here are still lower than those of lithium disilicate glass-ceramics. The only difference observed between the monolithic CAD CAM zirconia materials, was for the low opalescence parameter for the ZF. CLINICAL SIGNIFICANCE: Multi-layered monolithic zirconia systems have better esthetics by shade layers resembling natural tooth color gradients. CAD-CAM technology allowed for in-office milling and shaping of restorations using these systems. This study reports on their optical properties affecting human vision/perception of natural tooth shade to conclude about their use in the esthetic zones.

Correlating dental caries with oral bacteria and the buffering capacity of saliva in children in Madinah, Saudi Arabia.

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 10(5) 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.

Effect of an occlusal screw-access hole on the fracture resistance of permanently cemented implant crowns: a laboratory study.

This study aimed to evaluate the fracture resistance of cement-retained metal-ceramic implant-supported posterior crowns. Three groups of 10 restorations each were tested: group A (cement-retained using zinc phosphate), group B (cement-retained using zinc oxide-eugenol), and group C (cement-retained using zinc phosphate but with an occlusal screw-access hole). All specimens were thermocycled and vertically loaded in a universal testing machine. Mean values of fracture loads were calculated and analyzed statistically. The cement-retained restorations without an occlusal screw-access hole showed significantly higher mean fracture loads than those having one. The type of cement did not affect the porcelain fracture resistance significantly.

Porcelain fracture resistance of screw-retained, cement-retained, and screw-cement-retained implant-supported metal ceramic posterior crowns.

PURPOSE: The purpose of this in vitro study was to compare the porcelain fracture resistance between screw-retained, cement-retained, and combined screw- and cement-retained metal-ceramic (MC) implant-supported posterior single crowns; and to investigate the effect of offsetting the occlusal screw-access opening on porcelain fracture resistance of screw-retained and cement-retained MC implant-supported posterior single crowns. MATERIALS AND METHODS: Forty standardized MC molar-shaped restorations were fabricated. The 40 restorations were divided into four groups (SRC, SRO, CRP, and CSC) of 10 specimens each. Group SRC: screw-retained, screw-access hole placed in the center of the occlusal surface; Group SRO: screw-retained, screw access hole placed 1 mm offset from the center of the occlusal surface toward the buccal cusp; Group CRP: cement-retained, zinc phosphate cement was used; Group CSC: cement-retained with a screw-access hole in the center of the occlusal surface. The screw-retained restorations and abutments were directly attached to 3i implant fixtures embedded in acrylic resin blocks. Subsequently, all test specimens were thermocycled and vertically loaded in a universal testing machine at a crosshead speed of 2 mm/min until fracture. Mean values of load at fracture (in N) were calculated in each group and compared with a one-way ANOVA and Tukey's Studentized test (alpha= 0.05). RESULTS: Mean values of loads required to fracture the restorations were as follows (N): Group SRC: 1721 +/- 593; Group SRO: 1885 +/- 491; Group CRP: 3707 +/- 1086; Group CSC: 1700 +/- 526. Groups SRC, SRO, and CSC required a significantly lower force to fracture the porcelain than did the CRP group (p < 0.05). CONCLUSION: 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.

Interventions for cleaning dentures in adults.

BACKGROUND: Removing denture plaque may be essential for maintaining the oral health of edentulous people. Brushing and soaking in chemical products are two of the most commonly used methods of cleaning dentures. OBJECTIVES: To evaluate the effectiveness and safety of different methods for cleansing removable dentures. SEARCH STRATEGY: We searched the following databases: the Cochrane Oral Health Group Trials Register (to May 2009); CENTRAL (The Cochrane Library 2009, Issue 2); MEDLINE (1965 to May 2009); EMBASE (1980 to May 2009); LILACS (1980 to May 2009); and CINAHL (1997 to May 2009). There were no language restrictions. SELECTION CRITERIA: Randomised controlled trials (RCTs) comparing any mechanical method (e.g. brushing or ultrasound) or chemical (e.g. enzymes, sodium hypochlorite, oral rinses or peroxide solutions) in adults over the age of 18 wearing removable partial dentures or complete dentures.The primary outcomes considered were the health of denture bearing areas (soft tissues, periodontal tissues and teeth) and participants' satisfaction and preference. Secondary outcomes included denture plaque coverage area, indicators of halitosis and microbial counts on abutment teeth, soft tissues or denture base or saliva. DATA COLLECTION AND ANALYSIS: Two independent review authors screened and extracted information from, and independently assessed the risk of bias in the included trials. MAIN RESULTS: Although six RCTs were included in this review, the wide range of different interventions and outcome variables did not permit pooling of data in a meta-analysis. Isolated reports indicated that chemicals and brushing appear to be more effective than placebo in the reduction of plaque coverage and microbial counts of anaerobes and aerobes on complete denture bases. AUTHORS' CONCLUSIONS: 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.