Clinical marginal fit of zirconia crowns and patients' preferences for impression techniques using intraoral digital scanner versus polyvinyl siloxane material.

STATEMENT OF PROBLEM: The use of digital intraoral scanners is increasing; however, evidence of its precision in making crown impressions clinically remains scarce. Patients should also feel more comfortable with digital impressions, but only a few studies evaluating this subject have been performed. PURPOSE: The purpose of this clinical study was to evaluate the marginal fit of monolithic zirconia crowns and patients' preferences for digital impressions versus polyvinyl siloxane (PVS) impressions. MATERIAL AND METHODS: Sixteen participants with indications for single molar crowns were included. After crown preparation, digital impressions by intraoral scanner and PVS impressions were made. The participants were asked to complete a 6-item questionnaire with a visual analog scale related to perceptions of each of the following topics: time involved, taste/smell, occlusal registration, size of impression tray/scanner, gag reflex, and overall preference. Computer-aided design and computer-aided manufacturing monolithic zirconia crowns were fabricated from both impressions. The crowns were evaluated intraorally, and a blinded examiner measured the marginal discrepancy of silicone replicas under a stereomicroscope. Intraexaminer reliability was evaluated by calculating the intraclass correlation coefficient. Data for patients' preferences and marginal discrepancies were analyzed using the paired t test (α=.05). RESULTS: Visual analog scale scores for digital impressions were statistically significantly higher than those for PVS impressions in every topic (P<.05), except for occlusal registration. The results showed excellent reliability of the examiner with an intraclass correlation coefficient of .996. No significant difference was found in marginal discrepancies between the PVS group and the digital group on all sides (P>.05). CONCLUSIONS: No differences were found in the clinical marginal fit of zirconia crowns fabricated from either digital impressions compared with PVS impressions. Furthermore, patients' satisfaction with digital impressions was significantly higher than with conventional impressions.

Fracture Resistance of Lithium Disilicate Ceramics Bonded to Enamel or Dentin Using Different Resin Cement Types and Film Thicknesses.

PURPOSE: To investigate the influence of cement film thickness, cement type, and substrate (enamel or dentin) on ceramic fracture resistance. MATERIALS AND METHODS: One hundred extracted human third molars were polished to obtain 50 enamel and 50 dentin specimens. The specimens were cemented to 1-mm-thick lithium disilicate ceramic plates with different cement film thicknesses (100 and 300 µm) using metal strips as spacers. The cements used were etch-and-rinse (RelyX Ultimate) and self-adhesive (RelyX U200) resin cements. Compressive load was applied on the ceramic plates using a universal testing machine, and fracture loads were recorded in Newtons (N). Statistical analysis was performed by multiple regression (p < 0.05). Representative specimens were evaluated by scanning electron microscopy to control the cement film thickness. RESULTS: The RelyX Ultimate group with a cement thickness of 100 µm cemented to enamel showed the highest mean fracture load (MFL; 1591 ± 172.59 N). The RelyX Ultimate groups MFLs were significantly higher than the corresponding RelyX U200 groups (p < 0.05), and thinner film cement demonstrated a higher MFL than thicker films (p < 0.05). Bonding to dentin resulted in lower MFL than with enamel (p < 0.001). CONCLUSIONS: Higher fracture loads were related to thinner cement film thickness and RelyX Ultimate resin cement. Bonding to dentin resulted in lower fracture loads than bonding to enamel. CLINICAL SIGNIFICANCE: Reduced resin film thickness could reduce lithium disilicate restoration fracture. Etch-and-rinse resin cements are recommended for cementing on either enamel or dentin, compared with self-adhesive resin cement, for improved fracture resistance.

Effectiveness of a motionless ultrasonic toothbrush in reducing plaque and gingival inflammation in patients with fixed orthodontic appliances.

OBJECTIVE: To compare the effectiveness of a motionless ultrasonic toothbrush to a manual toothbrush in reducing dental plaque, gingival inflammation, and mutans streptococci in patients with fixed orthodontic appliances. MATERIALS AND METHODS: Twenty-five orthodontic patients were recruited to this crossover study. The patients were randomized into two groups starting with manual or motionless ultrasonic toothbrushes for 30 days. After a 30-day washout period, the patients switched to the other toothbrush type for 30 days. Plaque and gingival indices were evaluated by two calibrated-blinded examiners before and after each 30-day period of brushing. Salivary samples were also collected for quantification of mutans streptococci. RESULTS: On the bracket side, the motionless ultrasonic toothbrush showed a significantly higher mean plaque index bracket score after 30-day usage than baseline (P = .049), while the manual toothbrush group showed no difference between the before and after brushing periods (P = .10). The changes in plaque index bracket score were significantly more favorable in the manual toothbrush group than in the ultrasonic toothbrush group (P = .04). In contrast, no difference was observed on the nonbracket side. There was no significant difference in the changes of gingival index or the numbers of mutans streptococci between the two groups. CONCLUSION: Manual toothbrushing performed better than brushing with the motionless ultrasonic toothbrush in plaque removal on the bracket side in orthodontic patients. However, no difference was observed in terms of gingival status and the numbers of mutans streptococci.

Wear of human enamel opposing monolithic zirconia, glass ceramic, and composite resin: an in vitro study.

STATEMENT OF PROBLEM: Demand is increasing for ceramic and composite resin posterior restorations. However, ceramics are recognized for their high abrasiveness to opposing dental structure. PURPOSE: The purpose of this study was to investigate the wear of enamel as opposed to dental ceramics and composite resin. MATERIAL AND METHODS: Twenty-four test specimens (antagonists), 6 each of monolithic zirconia, glass ceramic, composite resin, and enamel, were prepared into cylindrical rods. Enamel specimens were prepared from 24 extracted human permanent molar teeth. Enamel specimens were abraded against each type of antagonist with a pin-on-disk wear tester under a constant load of 25 N at 20 rpm for 4800 cycles. The maximum depth of wear (Dmax), mean depth of wear (Da), and mean surface roughness (Ra) of the enamel specimens were measured with a profilometer. All data were statistically analyzed by 1-way ANOVA, followed by the Tukey test (α=.05). A paired t test was used to compare the Ra of enamel at baseline and after testing. The wear of both the enamel and antagonists was evaluated qualitatively with scanning electron microscopic images. RESULTS: No significant differences were found in enamel wear depth (Dmax, Da) between monolithic zirconia (2.17 ±0.80, 1.83 ±0.75 µm) and composite resin (1.70 ±0.92, 1.37 ±0.81 µm) or between glass ceramic (8.54 ±2.31, 7.32 ±2.06 µm) and enamel (10.72 ±6.31, 8.81 ±5.16 µm). Significant differences were found when the enamel wear depth caused by monolithic zirconia and composite resin was compared with that of glass ceramic and enamel (P<.001). The Ra of enamel specimens increased significantly after wear tests with monolithic zirconia, glass ceramic, and enamel (P<.05); however, no difference was found among these materials. CONCLUSIONS: Within the limitations of this in vitro study, monolithic zirconia and composite resin resulted in less wear depth to human enamel compared with glass ceramic and enamel. All test materials except composite resin similarly increased the enamel surface roughness after wear testing.

The influence of finish line curvature on the marginal gap width of ceramic copings.

STATEMENT OF PROBLEM: As a result of natural tooth anatomy or gingival recession, anterior teeth are more likely to present increased abutment finish line curvature. PURPOSE: The purpose of this study was to investigate the influence of the curvature of the finish line on the marginal gap widths of ceramic copings. MATERIAL AND METHODS: An ivorine maxillary central incisor was prepared for 3 different abutment finish line curvatures (1, 3, and 5 mm). Thirty-six copings were fabricated for each of these curvatures by using Cercon, IPS e.max, and Lava systems. The marginal gap width was measured by using a stereomicroscope, and the data were subsequently analyzed by means of a 2-way ANOVA and a 1-way ANOVA (α=.05). RESULTS: A significantly higher mean marginal gap width was found for the 5-mm curvature group (Cercon, 76.59 ±23.01 µm; IPS e.max, 106.44 ±18.48 µm; Lava, 128.34 ±20.79 µm) than for both the 3-mm curvature group (Cercon, 60.18 ±9.74 µm; IPS e.max, 81.79 ±16.20 µm; Lava, 99.19 ±15.32 µm) and the 1-mm curvature group (Cercon, 38.3 ±6.85 µm; IPS e.max, 52.22 ±10.66 µm; Lava, 69.99 ±6.77 µm). CONCLUSIONS: The greater the finish line curvature, the wider the marginal gap widths for the 3 ceramic systems.

Anterior space management: interdisciplinary concepts.

UNLABELLED: This case report describes the treatment of one patient with maxillary anterior spacing, caused by bilateral lateral peg-shaped incisors, using a planned sequence of multidisciplinary approaches for esthetic treatment. An asymmetrical gingival line was visible when the patient smiled. To evaluate the desired gingival level and the proportion of restoration to be made using the recurring esthetic dental (RED) proportion method, a diagnostic wax-up model was fabricated. Esthetic crown lengthening corrected the gingival line. RED proportion analysis suggested minor tooth movement prior to any restoration. Two weeks' use of an orthodontic removable appliance with finger springs achieved the proper dental proportion. Home whitening was prescribed for 2 weeks, with an additional 2-week waiting period to ensure tooth color stability. Resin composite treatment corrected the mesial contour of the maxillary canines and reduced the space between the canines and lateral incisors. Final restoration was obtained by placing ceramic veneers on the lateral peg-shaped incisors. The esthetic treatment achieved excellent results; after veneer cementation, the patient exhibited greater confidence with a new smile. CLINICAL SIGNIFICANCE: Esthetic dental treatment requires various disciplines to achieve the treatment goal. This case report is an example of well-planned sequences of treatment from the beginning to complete treatment. By conservative and practical treatment approaches used in this case, the clinician will be able to manage to obtain the highest result of esthetic treatment.

Surface Hardness of Resin Cement Polymerized under Different Ceramic Materials.

Objectives. To evaluate the surface hardness of two light-cured resin cements polymerized under different ceramic discs. Methods. 40 experimental groups of 2 light-cured resin cement specimens (Variolink Veneer and NX3) were prepared and polymerized under 5 different ceramic discs (IPS e.max Press HT, LT, MO, HO, and Cercon) of 4 thicknesses (0.5, 1.0, 1.5, and 2.0 mm), Those directly activated of both resin cements were used as control. After light activation and 37°C storage in an incubator, Knoop hardness measurements were obtained at the bottom. The data were analyzed with three-way ANOVA, t-test, and one-way ANOVA. Results. The KHN of NX3 was of significantly higher than that of Variolink Veneer (P < 0.05). The KHN of resin cement polymerized under different ceramic types and thicknesses was significant difference (P < 0.05). Conclusion. Resin cements polymerized under different ceramic materials and thicknesses showed statistically significant differences in KHN.

Clinical evaluation of a resin-modified glass-ionomer liner for cervical dentin hypersensitivity treatment.

PURPOSE: To evaluate the effectiveness of two agents for treating cervical dentin sensitivity associated with gingival recession or noncarious cervical lesions. METHODS: 44 patients with at least mild sensitivity affecting cervical dentin were enrolled in a longitudinal randomized clinical trial. A resin-based desensitizer or an experimental glass-ionomer was assigned to treat at most two teeth from each side of the mouth. Sensitivity was assessed by tactile and cold tests, measured with a Visual Analogue Scale at baseline, after treatment, and at 1 week, 1, 3, 6, and 12 months after treatment. Other noteworthy clinical observations were recorded. RESULTS: Both treatments effectively reduced dentin sensitivity (mixed linear model analysis). Sensitivity score for the glass-ionomer was significantly lower than for the resin-based desensitizer after treatment and at all follow-up periods (P < 0.0001). Some overhanging margins were observed in the glass-ionomer group, which could accumulate plaque and cause gingivitis. Despite material loss from some teeth treated with the glass-ionomer, the follow-up sensitivity scores were still lower than baseline scores.