Terence E. Donovan

Survival rate of lithium disilicate restorations at 4 years: A retrospective study

STATEMENT OF PROBLEM Ceramic restorations are frequently being placed due to the esthetic demand and the cost of noble metals that has increased considerably. One major disadvantage of ceramic restoration is failure of the material due to fracture by crack propagation. In vitro studies are of little clinical significance and in vivo studies are too short to support clinical success. PURPOSE The purpose of this retrospective study was to evaluate the failure rate of lithium disilicate restorations (monolithic and layered) at 4 years. MATERIAL AND METHODS Data were collected over 45 months from 2 commercial laboratories. Restorations were categorized into monolithic restorations and layered restorations. Each category was further classified into complete coverage single crowns, fixed dental prostheses, e.max veneers, and inlay/onlay restorations. Failure rates were compared and analyzed using Chi-square (α=.05). RESULTS A total of 21,340 restorations were evaluated in this study and included 15,802 monolithic restorations and 5538 layered restorations. The failure rate for single crown monolithic restorations was 0.91% and was 1.83% for single crown layered restorations. For fixed dental prostheses, 4.55% of monolithic restorations failed. For e.max veneers, 1.3% of monolithic veneers fractured and 1.53% of layered veneers fractured. Of the inlay/onlay restorations group, 1.01% of monolithic restorations fractured. CONCLUSION In the short term (45 months), restorations fabricated with the lithium disilicate material (IPS e.max) had relatively low fracture rates. Layered single crowns fractured at approximately 2 times the rate of monolithic crowns.

Fracture of layered zirconia restorations at 5 years: A dental laboratory survey

Statement of problem. The use of ceramic restorations has significantly increased in recent years because of their esthetic properties and the high cost of noble metals. However, given the lack of long‐term clinical trials and the limitations of in vitro studies, the durability of ceramic restorations is still questionable. Purpose. The purpose of this retrospective study was to determine the fracture rate of layered zirconia restorations at up to 5 years of clinical performance by using a dental laboratory survey model. Material and methods. Data up to 5 years were collected from 2 commercial dental laboratories. Layered zirconia restorations returned to the laboratory for remaking because of failure (fracture) were identified and included. Restorations were categorized as anterior or posterior. Each category was further divided into complete coverage single crowns (SCs) and multiple unit fixed dental prostheses (FDPs). Fracture rates were compared and analyzed using the chi‐square test (&agr;=.05). Results. A total of 31 594 restoration records were reviewed and included 13 419 anterior restorations (10 134 SCs and 3285 FDPs) and 18 175 posterior restorations (12 810 SCs and 5365 FDPs). The overall fracture rate up to 5 years for all restorations (anterior and posterior) was 3.31%. The fracture rates for anterior restorations were less than for posterior restorations. The fracture rates for anterior SCs were approximately half those of the posterior SC fracture rate, and the combined fracture rate (anterior and posterior) was 3.25%. For FDPs, anterior FDPs fractured at a rate similar to that of posterior FDPs. The combined fracture rate (anterior and posterior FDPs) was 3.47%. Conclusions. Layered zirconia restorations displayed relatively low fracture rates in the relatively short term of 5 years.

Effect of Finishing and Polishing on the Surface Roughness of Four Ceramic Materials after Occlusal Adjustment.

PROBLEM Intraoral occlusal adjustment of ceramic restorations can create a significant increase in surface roughness that can produce wear of the opposing dentition. PURPOSE To compare the surface roughness of glazed and polished monolithic ceramics with the surface roughness produced by different intraoral polishing systems on adjusted monolithic ceramics. MATERIALS AND METHODS Milled ceramic discs (10 mm diameter × 2 mm thickness) were manufactured and distributed according to the following groups (n = 10): BruxZir (glazed and polished), Zenostar (glazed and polished), IPS Empress CAD, and IPS e.max CAD. Surface roughness, expressed as arithmetic average height (Ra ), was measured using atomic force microscope and profilometer before and after adjustment and polishing with the following intraoral polishing systems: BruxZir and Dialite ZR (for BruxZir), Zenostar and Dialite ZR (for Zenostar), and OptraFine and Dialite LD for IPS Empress CAD and IPS e.max CAD. Mean and standard error for each material and polishing system were calculated. T-test, one-way ANOVA, and Bonferroni post hoc tests were used to analyze data. RESULTS BruxZir zirconia presented smoother surfaces with Dialite ZR system compared to BruxZir system, Zenostar zirconia shown smoother surfaces with Zenostar system compared to Dialite ZR system and IPS Empress CAD and IPS e.max CAD presented smoother surfaces with OptraFine system in comparison to Dialite LD system. CONCLUSION All materials presented smoother surfaces at baseline than after adjustment and polishing. CLINICAL SIGNIFICANCE This paper reveals the results of an in vitro study that provides information to clinicians regarding which intraoral polishing system will produce a smoother surface after the adjustment and polishing of IPS Empress CAD, IPS e.max CAD, BruxZir and Zenostar ceramic materials. (J Esthet Restor Dent 28:382-396, 2016).

Effect of Finishing Techniques on the Marginal Integrity of Resin-Based Composite and Resin-Modified Glass Ionomer Restoration

UNLABELLED The purpose of this study was to evaluate the marginal integrity of resin-based composite (RBC and resin-modified glass ionomer cement (RMGIC) restorations as a function of finishing technique and location of the tooth. Forty extracted third molars were assigned to four groups (N = 10) according to finishing instruments (aluminum oxide discs, fluted carbides, fine diamonds, and coarse diamond). Each specimen received standardized Class V preparations on the facial and lingual surfaces with occlusal margins on enamel and gingival margins on dentin. Each preparation was randomly assigned to be restored with either RBC or RMGIC. Specimens were finished with standardized pressure at approximately 0.16 N and evaluated at a magnification of 600× using an environmental scanning electron microscope. Occlusal and gingival margins were analyzed using an imaging software, and means for all measured gaps were calculated. Data were analyzed with a factorial analysis of variance. All possible two-way interactions were included, and the level of significance was set at 0.05. There were no statistically significant differences among the four types of finishing instruments used in the study. RBC-restored specimens exhibited significantly smaller mean marginal gaps (1.70-7.56 μm) than RMGI-restored specimens (5.24-14.24 μm) in enamel and dentin margins, respectively. There was a statistically significant difference between enamel and dentin with regard to marginal gap formation. Under the conditions of this study, marginal gap formation was not affected by finishing technique. RBC margins exhibited significantly less marginal gap than RMGI margins, whereas enamel margins resulted in significantly less marginal gap than did dentin margins. CLINICAL SIGNIFICANCE Multiple factors can affect the marginal integrity and the longevity of direct restorations. From these, the finishing and polishing techniques are critical steps that are under the clinicians control, and proper finishing and polishing techniques should be applied for avoiding introduction of stress to the margin of the restoration. It seems that instrumentation do not play a significant role, as much as the restorative material and the substrate to bond.

pH and Erosive Potential of Commonly Used Oral Moisturizers

PURPOSE To measure the pH values of commonly used oral moisturizers and to evaluate their erosive potential using a gravimetric analysis. MATERIALS AND METHODS A pH analysis was performed for seven commercially available oral moisturizers using a calibrated pH meter. The pH recording was repeated three times, from three different bottles each of the same product. The gravimetric analysis was performed by submerging human dentin blocks in 5 ml of each of the moisturizers for a total of 2 weeks, with gravimetric measurements made at baseline, 24 hours, 48 hours, 96 hours, 1 week, and 15 days. Tap water was used as positive control and citric acid as the negative control. The erosive potential was descriptively analyzed, and a Spearman correlation coefficient was used to assess the relationship between the erosive potential and the pH values. RESULTS The average pH values are as follows: Oasis, 6.3, Bioténe Moisturizing Mouth Spray, 6.1, CTx2 Spray, 9.1, Mouth Kote, 3.0, Thayers, 6.3, Bioténe Oral Balance, 6.6, Rain, 7.1, tap water 6.99, and citric acid 1.33. The results (% of tooth structure lost) of the gravimetric analysis were as follows: Mouth Kote, 9.6%, Bioténe Moisturizing Mouth Spray, 4.6%, Oasis, 3.2%, Thayers, 2.0%, Bioténe Oral Balance, 0.0%, Rain, 0.0%, CTx2 Spray, 0.0%, tap water 0.0%, and citric acid 18.8%. There was a significant negative correlation between the pH values and the erosive potential (r(s) = -0.73; P ≤ 0.0001). CONCLUSIONS There is large variation in the composition and pH values of commonly used oral moisturizers, and there is a strong correlation between pH values and erosive potential of commonly used oral moisturizers. CLINICAL SIGNIFICANCE Patients with dry mouth are at increased risk for erosion and root caries. Oral moisturizing agents are often prescribed for patients with hyposalivation to be used as needed for symptomatic relief. This study shows that there is large variation in the pH values and erosive potential of commonly used oral moisturizing agents.

Five-year success rate of resin-bonded fixed partial dentures: A systematic review

OBJECTIVES To assess and compare the 5-year success rate of resin-bonded fixed partial dentures (RBFPDs) fabricated from different materials. METHODS An electronic search on 3 databases from January 1965 to March of 2017 was done for human randomized clinical trials (RCTs), and prospective and retrospective cohort studies. The key words used in the search were: Bridge OR bridges OR fixed partial OR fixed dental AND resin bonded OR Maryland OR ceramic bonded. Quality assessment was done using the Newcastle-Ottawa scale. Success was defined as the RBFPDs remaining in situ and not having experienced debonding, biological failures, or mechanical failures at the examination visit. RESULTS Meta analyses of the included studies showed an estimated 5-year success rate of 88.18% for the metal framework RBFPDs and 84.41% for the nonmetal framework RBFPDs. The estimated 5-year success rate for each nonmetal material category was 92.07% for zirconia, 94.26% for In-Ceram alumina, and 84.83% for fiber-reinforced composite. The failure rate was not statistically significant among the single, double, and multiple retainers RBFPDs (P > .05). Technical complications were the main reason for failures. CONCLUSION The 5-year clinical performance of RBFPDs is similar to the performance of conventional fixed partial dentures (FPDs) and implant-supported crowns. CLINICAL SIGNIFICANCE Clinicians should consider using RBFPDs more often because their clinical performance is similar to the performance of conventional FPDs and implant-supported crowns.

Mechanical properties of resin-based cements with different dispensing and mixing methods

Statement of problem. Resin‐based cements are frequently used in clinical practice. To reduce time and technique sensitivity, manufacturers have introduced the same brand of cement with different dispensing methods. The effect of this change on properties of the cement is unknown. Purpose. The purpose of this in vitro study was to evaluate the mechanical properties of resin‐based cements with different dispensing systems. Material and methods. Specimens of resin‐based cements (n=14) PANAVIA SA Cement Plus Handmix, PANAVIA SA Cement Plus Automix, RelyX Unicem Handmix, RelyX Unicem 2 Automix, G‐CEM Capsule Automix, G‐CEM LinkAce Automix, Variolink II Handmix, and Variolink Esthetic Automix were prepared for each mechanical test. They were examined after thermocycling (n=7/subgroup) for 20 000 cycles as to fracture toughness (FT) (ISO standard 6872; single‐edge V‐notched beam method), compressive strength (CS) (ISO 9917‐1), and diametral tensile strength (DTS). The specimens were mounted and loaded at a crosshead rate of 1 mm/min (0.5 mm/min for FT) with a universal testing machine until failure occurred. The 2‐and 1‐way ANOVA followed by the Tukey HSD post hoc test were used to analyze data for statistical significance (&agr;=05). Results. Thermocycling had a significant effect in reducing the FT property of all resin‐based cements except RelyX Unicem 2 and G‐CEM LinkAce (P<.05). Variolink II and G‐CEM LinkAce showed better FT properties than their automixed counterparts (P<.05). The overall CS of all automixed resin‐based cements was better than that of their hand‐mixed counterpart, except for Variolink II. PANAVIA SA Automixed and G‐CEM LinkAce had higher DTS than their hand‐mixed counterparts (P<.05). Conclusions. Changing the dispensing method alters the mechanical properties of resin‐based cements. The clinical significance of these results is yet to be determined.