Gildo Coelho Santos

Effect of ceramic shade on the degree of conversion of a dual-cure resin cement analyzed by FTIR

OBJECTIVES The aim of this research was to evaluate the degree of monomer conversion of different resin cement shades when photocured under different feldspathic ceramic shades. The photocuring time was also evaluated as well as the translucency of each ceramic shade. METHODS Three VITA VM7 ceramic shades (Base Dentin 0M1, Base Dentin 2M2 and Base Dentin 5M3) were used to determine the translucency percentage. A spectrophotometer MiniScan was used to measure the opacity percentage of each specimen (2-mm-thick) and then the translucency was calculated. To measure the degree of conversion (DC), the resin cement (Variolink II; A3 Yellow and transparent) specimens (thickness: 100 μm) were photocured under a ceramic block (2-mm-thick) for 20 or 40s. Specimens photocured without the ceramic block were used as control. Sixteen groups (n=3) were evaluated. Micro-ATR/FTIR spectrometry was used to evaluate the extent of polymerization of all specimens after 24h. The %DC was calculated of experimentally polymerized versus maximally polymerized composite. RESULTS The translucency percentages of 0M1, 2M2 and 5M3 ceramics were 12.41 (1.02)%, 5.75 (1.91)% and 1.07 (0.03)%, respectively. The %DC of both resin cement shades cured under ceramic 5M3 was significantly lower than the other groups (p<0.05). The %DC of 0M1 groups exhibited no significant difference from 2M2 groups (p>0.05), with the exception of the transparent cement photocured for 40s. CONCLUSION Photocuring under 2mm ceramic showed that the increase in chroma saturation significantly decreased Variolink II resin cement %DC (100-μm-thick).

Clinical evaluation of ceramic inlays and onlays fabricated with two systems: five-year follow-up.

This study evaluated the five-year clinical performance of ceramic inlays and onlays made with two systems: sintered Duceram (Dentsply-Degussa) and pressable IPS Empress (Ivoclar Vivadent). Eighty-six restorations were placed by a single operator in 35 patients with a median age of 33 years. The restorations were cemented with dual-cured resin cement (Variolink II, Ivoclar Vivadent) and Syntac Classic adhesive under rubber dam. The evaluations were conducted by two independent investigators at baseline, and at one, two, three, and five years using the modified United States Public Health Service (USPHS) criteria. At the five-year recall, 26 patients were evaluated (74.28%), totalling 62 (72.09%) restorations. Four IPS restorations were fractured, two restorations presented secondary caries (one from IPS and one from Duceram), and two restorations showed unacceptable defects at the restoration margin and needed replacement (one restoration from each ceramic system). A general success rate of 87% was recorded. The Fisher exact test revealed no significant difference between Duceram and IPS Empress ceramic systems for all aspects evaluated at different recall appointments (p>0.05). The McNemar chi-square test showed significant differences in relation to marginal discoloration, marginal integrity, and surface texture between the baseline and five-year recall for both systems (p<0.001), with an increased percentage of Bravo scores. However, few Charlie or Delta scores were attributed to these restorations. In conclusion, these two types of ceramic materials demonstrated acceptable clinical performance after five years.

Shear bond strength of resin cement bonded to alumina ceramic after treatment by aluminum oxide sandblasting or silica coating

PURPOSE To evaluate the shear bond strength and bond durability between a dual-cured resin cement (RC) and a high alumina ceramic (In-Ceram Alumina), subjected to two surface treatments. MATERIALS AND METHODS Forty disc-shaped specimens (sp) (4-mm diameter, 5-mm thick) were fabricated from In-Ceram Alumina and divided into two groups (n = 20) in accordance with surface treatment: (1) sandblasting by aluminum oxide particles (50 μm Al(2) O(3) ) (SB) and (2) silica coating (30 μm SiO(x) ) using the CoJet system (SC). After the 40 sp were bonded to the dual-cured RC, they were stored in distilled water at 37°C for 24 hours. After this period, the sp from each group were divided into two conditions of storage (n = 10): (a) 24 h-shear bond test 24 hours after cementation; (b) Aging-thermocycling (TC) (12,000 times, 5 to 55°C) and water storage (150 days). The shear test was performed in a universal test machine (1 mm/min). RESULTS ANOVA and Tukey (5%) tests noted no statistically significant difference in the bond strength values between the two surface treatments (p = 0.7897). The bond strengths (MPa) for both surface treatments reduced significantly after aging (SB-24: 8.2 ± 4.6; SB-Aging: 3.7 ± 2.5; SC-24: 8.6 ± 2.2; SC-Aging: 3.5 ± 3.1). CONCLUSION Surface conditioning using airborne particle abrasion with either 50 μm alumina or 30 μm silica particles exhibited similar bond strength values and decreased after long-term TC and water storage for both methods.

Retrospective clinical evaluation of ceramic onlays placed by dental students

Statement of problem. Indirect restorations with partial or complete occlusal surface coverage have been recommended to restore teeth with weakened walls in order to prevent cusp fracture. The success of these restorations when performed by dental students is unknown. Purpose. The purpose of this retrospective study was to evaluate the clinical performance of adhesively bonded ceramic onlay restorations placed by third‐ and fourth‐year dental students. Material and methods. Sixty‐five ceramic onlays were placed in patients between 2009 and 2015. The onlays were laboratory or chairside fabricated with a computer‐aided design and computer‐aided manufacturing (CAD‐CAM) system, using either IPS e.max Press or IPS e.max CAD. An adhesive technique and luting composite resin agent were used to cement the restorations. Thirty‐seven onlays were evaluated clinically using the modified United States Public Health Service (USPHS) criteria. Data were statistically analyzed using the Cox proportional hazards model to compare tooth type and failures and the Fisher exact and McNemar tests to compare the USPHS criteria for significant differences (&agr;=.05). Survival probability was calculated using the Kaplan‐Meier algorithm. Results. Five onlays were considered to be failures and needed replacement. According to the Kaplan‐Meier analysis, the estimated survival rate was 96.3% after 2 years and 91.5% at 4 years. All 5 of the failures occurred on molars (13.5%) and none on premolars (P=.025). A statistically significant difference was found for marginal discoloration between onlays placed within 0 to 3 years and 3 to 6 years (P<.05) but no differences between any other criteria. Conclusions. Ceramic onlays placed by dental students demonstrated acceptable long‐term clinical performance.

Marginal adaptation of CAD-CAM onlays: Influence of preparation design and impression technique

Statement of problem. Factors that may affect the marginal adaptation of computer‐aided design and computer‐aided manufacturing (CAD‐CAM) restorations include preparation design, impression technique, and CAD‐CAM system. The influence of impression technique and preparation design on CAD‐CAM partial coverage restorations has not been fully addressed. Purpose. The purpose of this in vitro study was to investigate the influence of direct and indirect digital scanning techniques and 2 preparation designs on the marginal adaptation of CAD‐CAM onlays. Material and methods. Two mesio‐occlusal buccal onlay preparations with reduction of the mesiobuccal cusp were made: conventional preparation (CP) with a 1.2‐mm modified shoulder margin and modified preparation (MP) flat cuspal reduction without shoulder. Virtual models were generated from each preparation by using a digital scanner (BlueCam; Dentsply Sirona) from the plastic teeth (direct digital scan) or from the stone dies (indirect digital scan). Onlays were designed using a CAD‐CAM system (CEREC 4.0; Dentsply Sirona), and nanoceramic resin blocks (Lava Ultimate Restorative; 3M ESPE) were milled using the CEREC MCX milling machine. Marginal discrepancy was evaluated using an optical stereomicroscope at ×25 magnification in 18 locations distributed along the margins of the preparation. The data were analyzed by using 3‐way ANOVA followed by the Tukey HSD test (&agr;=.05). Results. CP presented a statistically significant reduced average marginal adaptation (59 ±50 &mgr;m) than did MP (69 ±58 &mgr;m) (P<.001). The Tukey HSD test showed the presence of a significantly larger marginal discrepancy in the mesial and buccal locations of MP when compared with CP. Regarding impression techniques, the buccal location presented the smallest average marginal discrepancy in restorations fabricated with indirect impression when compared with direct impression (42 ±33 &mgr;m and 60 ±39 &mgr;m) (P<.001). Conclusions. The results showed that conventional preparation with a modified shoulder margin presented improved marginal adaptation compared with modified preparation with flat cuspal reduction. Direct and indirect digital scanning techniques produced restorations within a clinically acceptable range; however, the indirect scanning technique resulted in the fabrication of restorations with superior marginal adaptation on the buccal location.