Abfraction is a type of noncarious cervical lesion (NCCL) characterized by loss of tooth tissues with different clinical appearances. Evidence supports that abfraction lesions, as any NCCLs, have a multifactorial etiology. Particularly, the cervical wear of abfraction can occur as a result of normal and abnormal tooth function and may also be accompanied by pathological wear, such as abrasion and erosion. The interaction between chemical, biological, and behavioral factors is critical and helps to explain why some individuals exhibit more than one type of cervical wear mechanism than others. In an era of personalized dentistry, patient risk factors for NCCLs must be identified and addressed before any treatment is performed. Marked variations exist in dental practice concerning the diagnosis and management of these lesions. The lack of understanding about the prognosis of these lesions with or without intervention may be a major contributor to variations in dentists’ management decisions. This review focuses on the current knowledge and available treatment strategies for abfraction lesions. By recognizing that progressive changes in the cervical area of the tooth are part of a physiologically dynamic process that occurs with aging, premature and unnecessary intervention can be avoided. In cases of asymptomatic teeth, where tooth vitality and function are not compromised, abfraction lesions should be monitored for at least 6 months before any invasive procedure is planned. In cases of abfraction associated with gingival recession, a combined restorative-surgical approach may be performed. Restorative intervention and occlusal adjustment are not indicated as treatment options to prevent further tooth loss or progression of abfraction. The clinical decision to restore abfraction lesions may be based on the need to replace form and function or to relieve hypersensitivity of severely compromised teeth or for esthetic reasons.
Objective: To estimate the time required for teeth to dehydrate and rehydrate and its relation to the accuracy of tooth shade selection.Materials and Methods: Thirty-two participants were recruited, and color measurements were conducted using a spectrophotometer placed with a custom jig. After isolation, baseline measurements were made at 1, 2, 3, 5, 7, 10, and 15 min intervals to determine dehydration time.After mouth rinsing, measurements were made to determine rehydration time. CIEDE2000 values were obtained for color change between the baseline recordings and all intervals and compared to the 50:50% perceptibility and acceptability thresholds. Analysis of variance (ANOVA) and Tukey test was used for multiple comparisons.Result: The tooth color changes were beyond the ΔE 00 perceptibility threshold (0.8) within the first minute of dehydration (P > 0.0001). After the first minute, 87% of the teeth were beyond the ΔE 00 perceptibility threshold (0.8), and 72% of the teeth were beyond the ΔE 00 acceptability threshold (1.8). After 15 min of rehydration, 90% of the teeth were beyond the perceptibility threshold, and 65% were beyond the acceptability threshold.Conclusions: Shade selection procedures should be carried out within the first minute and before teeth dehydrate by means of isolation. Teeth do not rehydrate within 15 min after rehydration.Clinical Significance: Teeth dehydration has a negative impact on shade selection, which can affect the final esthetic outcome. Shade selection should be performed at the beginning of any restorative procedure.operative dentistry, prosthodontics, shade selection, teeth dehydration, teeth rehydration 1 | INTRODUCTION Shade selection for direct and indirect restorations is one of the most challenging components of esthetic dentistry. 1 Clark in 1931, the first to address the problem of color in dentistry, stated that "we as dentists are not educationally equipped to approach a color problem". 2 This statement applies to this day despite numerous advances in shade matching techniques in recent decades. Based on current prospective and retrospective clinical studies, 50% of cemented ceramic crowns exhibit incorrect color matches. [3][4][5][6] The CIELAB system is frequently used to measure color and color differences, which is based on the 1976 Commision Internationale de l´E clairage (CIE) L*a*b* color space. The three coordinates that determine color are L* coordinate represents lightness, while a* represents green-red, and b* represents blue-yellow coordinate. This system is the basis for transforming spectral energy data into meaningful color data. 6,7 Recently, the CIE published a new CIEDE2000 formula model which is extended to the CIE 1976 (L*a*b*) color-difference model with corrections for variation in color-difference perception dependent on Lightness, Chroma, Hue and Chroma-Hue interaction. Additionally, the CIE investigated the nonuniformity of the CIELAB space and developed this empirical correction to improve agreement between perceived visual color differenc...
ObjectiveTo evaluate and compare color stability and gloss retention of ceramic stains and glaze under simulated toothbrushing using dentifrices with different relative dentin abrasion (RDA).Materials and MethodsFeldspathic porcelain, lithium disilicate, 3 mol% yttria partially stabilized zirconia, and 5 mol% yttria partially stabilized zirconia were evaluated. Ceramics were externally stained, glazed and mounted in the toothbrush simulator. A toothbrush with 300 g force was applied. Regular toothpaste (72 RDA) and charcoal toothpaste (RDA <200) were used. Linear brushing motion with cycle intervals: 5 k, 10 k, 30 k, and 50 k was achieved. Change in color (CIEΔE2000) and gloss measurements were collected using a reflection spectrophotometer (Ci 7600, X‐rite) at baseline and cycle intervals. Repeated measures analysis of variance within specimen factors (ceramic type, toothpaste and cycles) was performed.ResultsΔE00 was significantly different at 50 k cycles and with zirconia ceramics (P < .0001). Charcoal toothpaste was significantly different in ΔE00 compared to regular toothpaste (P > .0001). Loss of gloss was observed at 5 k and 30 k (charcoal and regular toothpaste respectively) regardless type of ceramic (P > .0001).ConclusionGlass‐phase ceramics retain stains longer than zirconia ceramics. Charcoal toothpaste affect color and gloss stability. Ceramic glaze maybe lost within the first 6 months in patients' mouth.Clinical SignificanceLong‐term color and gloss stability of externally stained and glazed ceramics maybe a clinical concern. Charcoal toothpastes enhance loss of color and gloss of ceramic restorations.
SUMMARY Objective: To evaluate the effect of different photoinitiator systems on photopolymerizing resin cements through ceramic veneers with different thickness on microshear bond strength (μSBS), flexural strength (FS), and ultimate tensile strength (UTS) and verify the light attenuation through these ceramic veneers. Methods and Materials: Four photopolymerizing experimental resin cements were produced with the same resin matrix and associated with four different photoinitiator systems: camphorquinone (CQ), diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide (TPO), Ivocerin, and TPO + Ivocerin. Eighty disc-shaped ceramic veneers (IPS Empress Esthetic, Ivoclar Vivadent) were fabricated (10-mm diameter) in two different thicknesses: 0.7 and 1.5 mm. A previously characterized multiwave LED (Bluephase G2, Ivoclar Vivadent) was standardized for 40 seconds of photoactivation. Light transmittance through each ceramic veneer thickness (n=5) was measured using a spectrometer (USB 2000, Ocean Optics). The μSBS of each resin cement (n=15) to the ceramic veneer was evaluated using 0.5-mm cylinders with 0.7-mm diameters photoactivated through the different ceramic veneer thicknesses. Samples for FS and UTS tests were made either with or without ceramics veneers (0.7 and 1.5 mm) fixed to the light-curing tip. Data were submitted to two-way analysis of variance and the Tukey test (α=0.05). Results: The multiwave LED emitted higher irradiance into the blue wavelength spectra than into the violet wavelength spectra (p=0.0001). Light transmittance through the ceramic veneers was reduced in a systematic manner based on thickness regardless of the wavelength spectra emitted from the multiwave LED (p=0.00037). The μSBS was reduced in a systematic manner based on thickness regardless of the photoinitiator system (p<0.05). However, resin cements with CQ and Ivocerin showed higher bond strength values in comparison to the resin cement with TPO regardless of the ceramic veneer thickness (p<0.05). The FS and UTS means decreased (p<0.05) with the interposition of 0.7- and 1.5-mm ceramic veneers for all resin cements. The resin cement containing only TPO showed the lowest FS and UTS means (p<0.05) for all ceramic veneers. Conclusions: The thickness of the ceramic veneers reduced the irradiance of the multiwave LED in all wavelength spectra. Ivocerin alone or associated with TPO showed to be an effective alternative photoinitiator to substitute for CQ. The resin cement containing only TPO had lower bond strength values in comparison to resin cements with CQ, Ivocerin, and Ivocerin + TPO.
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