Evolution of Aesthetic Dentistry.

One of the main goals of dental treatment is to mimic teeth and design smiles in a most natural and aesthetic manner, based on the individual and specific needs of the patient. Possibilities to reach that goal have significantly improved over the last decade through new and specific treatment modalities, steadily enhanced and more aesthetic dental materials, and novel techniques and technologies. This article gives an overview of the evolution of aesthetic dentistry over the past 100 y from a historical point of view and highlights advances in the development of dental research and clinical interventions that have contributed the science and art of aesthetic dentistry. Among the most noteworthy advancements over the past decade are the establishment of universal aesthetic rules and guidelines based on the assessment of natural aesthetic parameters, anatomy, and physiognomy; the development of tooth whitening and advanced restorative as well as prosthetic materials and techniques, supported by the pioneering discovery of dental adhesion; the significant progress in orthodontics and periodontal as well as oral and maxillofacial surgery; and, most recently, the implementation of digital technologies in the 3-dimensional planning and realization of truly natural, individual, and aesthetic smiles. In the future, artificial intelligence and machine learning will likely lead to automation of aesthetic evaluation, smile design, and treatment-planning processes.

Eighteen-month Clinical Study of Universal Adhesives in Noncarious Cervical Lesions.

OBJECTIVE: To evaluate the clinical performance of Scotchbond Universal (3M Oral Care) and Prime & Bond Elect (Dentsply Sirona) in the restoration of noncarious cervical lesions (NCCLs). METHODS AND MATERIALS: This was a randomized controlled clinical trial involving 63 subjects. Two hundred and three NCCLs were restored using Scotchbond Universal and Prime & Bond Elect using both an etch-and-rinse and a self-etch technique. Lesions were notch-shaped NCCLs, and the restorations were placed without any mechanical retention. Restorations were finished immediately after placement and scored with regard to retention, marginal discoloration, marginal adaptation, and secondary caries. Similar assessment of the restorations was performed 18 months after placement. Logistic regression was performed for each outcome separately with a compound symmetric variance-covariance structure assumed to consider a correlation of restorations within subjects. All analyses were conducted using SAS version 9.4 (SAS Inc). RESULTS: One hundred and fifty-eight teeth (77.8% of the restorations placed) in 46 subjects (73% of subjects enrolled) were available for the 18-month follow-up. A statistically significant difference was reached only for the comparison Scotchbond Universal/self-etch (SU_SE) and Prime & Bond Elect/etch-and-rinse (PBE_E&R) groups ( p=0.01), where a restoration with SU_SE was 66% less likely to maintain a score of Alpha for marginal discoloration than a restoration performed with PBE_E&R. CONCLUSIONS: Scotchbond Universal and Prime & Bond Elect presented acceptable clinical performance after 18 months of clinical service. However, Scotchbond Universal, when applied with a self-etch approach, did demonstrate a relatively high level of marginal discoloration when compared to the other groups.

Tooth whitening products and the risk of oral cancer.

Tooth whitening products (TWP) containing hydrogen peroxide (HPO) or carbamide peroxide (CPO) were evaluated in relation to potential oral cancer risk from their use. HPO is genotoxic in vitro, but such activity is not expressed in vivo. The genotoxic risk of HPO exposure of the oral mucosa encountered from TWP use is likely therefore to be vanishingly small. Available animal data on the carcinogenicity of HPO are of limited relevance to risk assessment of oral hazard of HPO exposure from TWP, and where relevant, do not indicate that there is an increased oral cancer risk for people using TWP. Clinical data on HPO-containing TWP only show evidence of mild, transient gingival irritation and tooth sensitivity, with no evidence for the development of preneoplastic or neoplastic oral lesions. Exposures to HPO received by the oral cavity, including areas commonly associated with oral cancer, are exceedingly low and do not plausibly pose a risk for the promotion of initiated cells or for induction of co-carcinogenic effects in conjunction with cigarette smoke or alcohol. The use of TWP was concluded not to pose an increased risk for oral cancer in alcohol abusers and/or heavy cigarette smokers. Furthermore, TWP were concluded to be safe for use by all members of the population, including potential accidental use by children.

Tooth whitening: facts and fallacies.

Since the introduction of nightguard vital bleaching (tray bleaching) in 1989, dentistry has witnessed an astronomical rise in the interest in tooth whitening.(1) As a result, the most frequently asked question is, 'what bleaching technique works best?' Virtually all of today's whitening approaches work, because bleach is bleach. Whether a nightguard bleach is used with only 10% carbamide peroxide (which contains only 3% hydrogen peroxide), over-the-counter (OTC) whitening strips are applied containing 6% hydrogen peroxide, or an in-office bleach is employed using 25-35% hydrogen peroxide, the end results can potentially be the same. Similarity of results is possible because the mechanism of action is the same: oxidation of organic pigments or chromogens in the tooth. Granted, some bleaching approaches are more expeditious than others, owing to differences in concentration or exposure time. But as just noted, the most important factors in the efficacy of any bleaching treatment are concentration of the bleaching agent and duration of the exposure time.

Clinical evaluation of two one-bottle dentin adhesives at three years.

BACKGROUND: The method currently used to adhere resin to dentin involves etching, priming and bonding. Many commercial adhesives now combine priming and bonding functions in a single solution, and these are frequently called one-bottle adhesives. The purpose of this study was to compare the 36-month clinical performance of two commercial one-bottle adhesives. METHODS: The authors enrolled 33 patients with noncarious cervical lesions in the study. A total of 101 lesions were restored with either a filled, ethanol-based adhesive (OptiBond Solo, SDS Kerr) or an unfilled, acetone-based adhesive (Prime & Bond 2.1, Dentsply Caulk) and a hybrid resin-based composite. Enamel margins were not beveled, and no mechanical retention was placed. The restorations were evaluated at baseline and six months, 18 months and 36 months after placement using modified Cvar/Ryge criteria. RESULTS: The retention rates at 36 months were 93.3 percent for the ethanol-based adhesive and 89.4 percent for the acetone-based adhesive. The difference in retention rates was not statistically significant. In both groups, 12 percent of the retained restorations had marginal staining, but no recurrent caries was detected around any restoration. Other restoration characteristics such as marginal adaptation and color match remained excellent three years after placement. CONCLUSIONS: The performance of both adhesives was excellent during this 36-month clinical trial. At the most recent recall evaluation (that is, 36 months), the filled, ethanol-based adhesive exhibited slightly better bond durability, but the difference between the two materials was not statistically significant. CLINICAL IMPLICATIONS: The one-bottle adhesives evaluated in this study provided excellent clinical retention of Class V restorations without mechanical retention. When the materials are used properly, restorations are retained at a high rate during at least three years of clinical service.

Eighteen-month clinical evaluation of a filled and unfilled dentin adhesive.

OBJECTIVE: The purpose of this study was to evaluate the performance of a filled (OptiBond Solo) and an unfilled (Prime & Bond 2.1) "one-bottle" adhesive in Class V restorations after 18 months of clinical service. METHODS: Thirty-three patients with non-carious cervical lesions were enrolled in the study. A total of 101 lesions were restored using one of the adhesives and a hybrid composite resin. Enamel was not beveled, nor was any mechanical retention placed. The restorations were evaluated at baseline, and at 6 and 18 months after placement using modified USPHS criteria. RESULTS: Cumulative 18-month retention rates were 93.6% for OptiBond Solo and 98.0% for Prime & Bond 2.1. The difference in retention rates was not statistically significant. For OptiBond Solo, the only notable problems were interfacial staining and marginal adaptation, both of which were less than ideal in 9% of restorations. Marginal problems were slightly less frequent for Prime & Bond 2.1 restorations, but the difference was not significant. CONCLUSIONS: Both adhesives provided Class V retention rates exceeding the 18-month, full acceptance guidelines set by the American Dental Association. Any additional benefit provided by the use of a filled adhesive was not detected in this 18-month clinical trial.

Effect of conditioner and restorative resin on enamel bond strengths.

PURPOSE: To evaluate the effect of three enamel conditioners and four restorative materials on enamel shear bond strengths. MATERIALS AND METHODS: 120 bovine incisors were polished to 600-grit and randomly assigned to three enamel adhesive systems (n=40): Syntac Single Component with phosphoric acid etching (PA-SSC), Syntac Single Component without phosphoric acid etching (SSC), and Experimental Prompt L-Pop (LPI), a self-etching adhesive. The specimens were restored with one of four resin restorative materials (n=10): (1) Compoglass F, a high-viscosity compomer; (2) Compoglass Flow, a low-viscosity compomer; (3) Tetric Ceram, a high-viscosity resin-based composite (RBC); and (4) Tetric Flow, a low-viscosity RBC. After thermocycling, shear tests were carried out with an Instron Universal Testing Machine. Mean enamel bond strengths were analyzed with ANOVA and Duncan post hoc test at P < or = 0.05. RESULTS: PA-SSC resulted in higher mean bond strengths than LP1, but the difference was not statistically significant. Both PA-SSC and LP1 resulted in statistically higher mean bond strengths than SSC at P < or = 0.0001. The lowest mean bond strengths of all the groups were obtained when SSC was used with an RBC (Tetric Ceram or Tetric Flow). SSC and PA-SSC resulted in statistically higher mean bond strengths when used with a compomer than when used with an RBC, regardless of the viscosity. Although recommended to be used only with compomers, LP1 resulted in statistically similar enamel bond strengths when used with the composite of corresponding viscosity (Tetric Ceram vs. Compoglass F; Tetric Flow vs. Compoglass Flow). LP1, however, resulted in higher enamel bond strengths when combined with Tetric Ceram than when combined with Tetric Flow. When the results were pooled for "viscosity", high-viscosity restorative materials resulted in higher bond strengths than low-viscosity materials at P < or = 0.041. When the data were pooled for "restorative material", compomers resulted in higher bond strengths than composites at P < or = 0.0001.

Shear bond strengths of one-bottle adhesives to oil-contaminated enamel.

PURPOSE: To evaluate resin bond strength to enamel contaminated with handpiece oil. MATERIALS AND METHODS: Bovine teeth were randomly assigned to six groups of 20 teeth each for treatment with one of six different bonding systems (five one-bottle and one multibottle). For each system, 10 enamel specimens were contaminated with handpiece oil before acid-etching and 10 were contaminated after acid-etching. The enamel was etched for 15 seconds using 35% phosphoric acid. Following adhesive application, composite resin was bonded using a gelatin capsule technique. Shear bond strengths from the two contaminated groups were compared to bond strengths to uncontaminated enamel obtained from a previous study that was performed by the same group of investigators, using the same facility, materials, and methods. RESULTS: Two-way analysis of variance (ANOVA) showed that the factor "surface contamination" did not have a significant effect on bond strength (p > .542). The type of adhesive and the interaction of adhesive and surface contamination were significant (p < .0001 and p < .003, respectively). When oil was applied before etching, mean bond strengths ranged from 18.0 +/- 4.8 MPa for OptiBond SOLO (Kerr Corp., Orange, California) to 25.3 +/- 5.6 MPa for Tenure Quik with Fluoride (Den-Mat Corp., Santa Maria, California). With oil applied after etching, bond strengths ranged from 18.4 +/- 8.0 MPa for Tenure Quik with Fluoride to 27.4 +/- 5.4 MPa for Single Bond (3M Dental Products, St. Paul, Minnesota). For the same adhesive, comparing uncontaminated and "oil-before-etch" contaminated groups, the only statistically significant difference in bond strengths was for OptiBond SOLO: 21.8 +/- 4.0 MPa (uncontaminated) versus 18.0 +/- 4.8 MPa (oil before etch). Comparing uncontaminated and "oil-after-etch" groups, the only statistically significant difference was for Tenure: 24.5 +/- 5.7 MPa (uncontaminated) and 18.4 +/- 8.0 MPa (oil after etch).

Effects of different re-wetting techniques on dentin shear bond strengths.

PURPOSE: For contemporary hydrophilic resin adhesive systems, bonding to dentin is improved if the substrate is maintained in a hydrated state following acid-etching. The purpose of this study was to compare the dentin shear bond strengths of two single-bottle adhesives (one acetone-based and one ethanol-based) applied under different etched-dentin conditions: dry, wet, or dry and re-wetted with different solutions. MATERIALS AND METHODS: Bovine incisors (N = 120) were mounted in acrylic, polished to 600-grit, and randomly assigned to 12 groups (n = 10). Dentin was etched for 15 seconds using 35% phosphoric acid, rinsed, and either blot-dried, air-dried, or air-dried and re-wetted with different solutions (distilled water, Gluma Desensitizer, Aqua-Prep, and 5% glutaraldehyde in water). Two adhesives (Single Bond and Prime & Bond NT) were applied to each of the surface conditions following manufacturers' instructions. After adhesive application and curing, composite was applied in a No. 5 gelatin capsule and light-cured. Specimens were loaded in shear, using an Instron at 5 mm per minute. Shear bond strengths were calculated by dividing the failure load by the bonded surface area. Data were subjected to analysis of variance (ANOVA) and a post hoc Tukey test. RESULTS: Mean shear bond strengths ranged from 12.5 to 26.6 MPa for Single Bond and from 5.6 to 14.7 MPa for Prime & Bond NT. Significant differences were found in both groups of materials (p < .001). The three highest mean bond strengths were obtained (in order) on dentin that was re-wetted with Gluma Desensitizer, re-wetted with Aqua-Prep, or never dried. Differences between these surface conditions were not statistically significant for either material.

Shear bond strengths of one-bottle adhesives to moist enamel.

PURPOSE: This study evaluated bond strengths of six one-bottle bonding agents and a control (primer plus unfilled resin) to moist enamel. MATERIALS AND METHODS: One-hundred and five bovine teeth were randomly assigned to seven groups of 15. Enamel was etched for 15 seconds with 35% phosphoric acid. Etched enamel was rinsed, and excess water was blotted with tissue paper. Following application of the adhesive, composite resin was bonded using a gelatin capsule technique. Shear bond strengths to enamel were determined using a universal testing machine (Instron Corp., Canton, Massachusetts). RESULTS: Mean bond strengths ranged from 21.9 MPa for OptiBond Solo (Kerr Corp., Orange, California) to 29.6 MPa for Prime & Bond 2.1 (Dentsply/Caulk, Milford, Delaware). Prime & Bond 2.1 had a significantly higher mean bond strength than the other adhesives. CLINICAL SIGNIFICANCE: The results of this study suggest that all of the one-bottle systems tested should provide clinically acceptable bonding to moist enamel.

Dental and oral discolorations associated with minocycline and other tetracycline analogs.

UNLABELLED: It has been well acknowledged in recent literature that minocycline, a semisynthetic tetracycline derivative, causes discolorations in adult teeth and various other collagenous tissues. This article presents the most common patterns of minocycline staining in addition to comparing the staining patterns of other tetracycline analogs in the permanent dentition. It also reviews the literature's most prominent theories describing the process of minocycline discoloration, and evaluates their plausibility. It is a goal of this article to make dental practitioners aware of the possible effects of minocycline therapy and to highlight useful ways to treat or prevent these discolorations. Currently, conventional treatments include vital and nonvital bleaching, veneers, or crowns, depending on the severity of the discoloration. The literature shows that possible preventive efforts revolve around cessation of the drug or the use of large doses of vitamin C or other antioxidants in conjunction with minocycline therapy to prevent the formation of the pigment responsible for the staining. CLINICAL SIGNIFICANCE: Minocycline and other tetracycline analogs are well known for causing discoloration of developing teeth in children. However, practitioners must be aware of the tooth staining potential of minocycline in adult populations as well. Studies suggest that the concomitant use of vitamin C may help prevent adult-onset pigmentation caused by minocycline.

Two-year clinical evaluation of tooth whitening using an at-home bleaching system.

PURPOSE: The purpose of this study was to evaluate the 2-year effectiveness of a carbamide peroxide at-home bleaching gel used to provide tooth lightening treatment. MATERIAL AND METHODS: Twenty-nine patients participated in the original study, during which they treated their maxillary teeth with a 10% carbamide peroxide gel nightly for 2 weeks. Shades were determined before and after treatment by comparison with a Vita shade guide. Twenty-four patients (a recall rate of 83%) were recalled for evaluation 2 years after the initial bleaching treatment. The shade of the maxillary incisors was evaluated and compared with shades before, immediately after, and at 6 months and 2 years after initial treatment. Data were analyzed using a repeated-measures analysis of variance. RESULTS: At 2 years after bleaching with a 10% carbamide peroxide gel, the median shade was D2, a six-increment difference from the baseline median of D3. Twenty of 24 patients (83.3%) had a shade change of two or more units, which is the threshold value for bleaching efficacy using American Dental Association guidelines. The lightening result remained statistically significant (p < .0001) at 2 years. CLINICAL SIGNIFICANCE: Although some reversal of the lightening effect occurs over time following the original bleaching treatment, loss of the lighter color appears to be gradual for most patients. Although the longevity of the lightening effect remains to be determined, this clinical trial indicates that the majority of patients have a satisfactory result 2 years after treatment.

Margin gap size of ceramic inlays using second-generation CAD/CAM equipment.

OBJECTIVE: The goal of this study was to determine if the fit of second-generation computer-assisted design/computer-assisted manufacturing (CAD/CAM) (CEREC 2, Sirona Dental Systems, Bensheim, Germany) inlays within Class II cavity preparations were within the range of 50 to 100 microns and were equal or better to CEREC 1 inlays. MATERIALS AND METHODS: Extracted human molars free of surface defects and caries were prepared with standard mesio-occlusodistal cavity preparations. Ceramic inlays were fabricated with CEREC 2 CAD/CAM equipment and seated into cavity preparations. Digital images were captured at 100 times magnification. Marginal gaps were measured with an image analysis program. For each restoration, gaps were measured at 12 locations along interproximal margins and 10 locations along occlusal margins. RESULTS: No difficulty occurred in seating any of the milled inlays. Average marginal gaps for occlusal (59 +/- 35 microns) and interproximal (97 +/- 66 microns) margins were statistically different (t-test, p < or = .01). Average marginal gap for all sites combined was 80 +/- 57 microns. Marginal gap widths were smaller than those obtained from a similar study done earlier with the CEREC 1 unit for occlusal (89 +/- 65 microns) and interproximal (105 +/- 81 microns) margins. Ease of seating with CEREC 2 inlays was much better than with CEREC 1. CLINICAL SIGNIFICANCE: Improvements in software and hardware allow the CEREC 2 to adapt well to standard inlay cavity preparations. The ability of the device to create inlays that seat without interference is remarkable. The improved fit and ability to create the occlusal surface in a variety of ways make CEREC 2 an attractive restorative option for all-ceramic restorations.

Enamel bond strengths of "one-bottle" adhesives.

PURPOSE: Several "one-bottle" dental adhesives recently have been introduced. These contain hydrophilic resin monomers that should readily wet tooth surfaces. Most also contain solvents that could increase enamel bond strengths by driving out residual moisture from enamel and increasing resin penetration. The purpose of this study was to evaluate bond strengths obtained by six one-bottle bonding agents and one conventional unfilled resin (control). METHODS: Seventy bovine teeth were randomly assigned to seven groups of 10. Enamel was etched for 15 s with 35% phosphoric acid. Following application of the adhesive, composite resin was bonded using a gelatin capsule technique. Shear bond strengths to enamel were determined. RESULTS: Mean bond strengths ranged from 14.2 MPa for Syntac Single-Component to 27.8 MPa for Single Bond. The mean for Syntac Single-Component was significantly less than that of all other systems tested. CONCLUSION: The results of this study indicate that one-bottle bonding agents, with the exception of the Syntac material, provide enamel bond strengths at least equal to that of a conventional unfilled resin.

Clinical evaluation of two carbamide peroxide tooth-whitening agents.

A blinded study was conducted to evaluate the efficacy and safety of a dentist-prescribed, accelerated carbamide peroxide tooth-whitening system. Fifty-one patients with discolored teeth completed a clinical trial using an overnight bleaching regimen. One group used an experimental bleaching (whitening) regimen with 10% carbamide peroxide bleaching paste, and another group used the Colgate Platinum Professional Overnight Whitening System. The study included an initial 1-week control/compliance phase using a placebo gel, followed by a 1-week active phase using the assigned bleaching agent. The shade of each participant's maxillary anterior teeth was evaluated by 2 trained and calibrated evaluators at the start of the control/compliance phase, the beginning of the active phase, and days 3, 5, and 7 of the active phase. A value-oriented Vita shade guide with 16 rankings was used to measure color changes, and the number of shade guide units of change (delta sgu) was calculated. Potential side effects, such as tooth hypersensitivity and gingival irritation, also were assessed at each recall examination, as well as recorded by the patients in their daily diaries. At the end of the 7-day active phase, the mean delta sgu for the group using the experimental bleaching agent was 7.1 +/- 2.4, and for the Colgate Platinum Overnight group, the delta sgu was 7.5 +/- 2.2. There were no statistically significant (p > or = 0.05) differences between the results of both groups at the 0-, 3-, 5-, and 7-day evaluations. After 7 days, the change in shade guide units for both groups ranged from 3 to 13 units, far exceeding the minimum required change by the American Dental Association Guidelines (delta sgu = 2 units) for demonstrating efficacy. There was no statistical difference in the whitening achieved at day 5 vs. day 7 for either tooth-whitening group. There were no notable changes in any gingival, bleeding, or plaque indexes for the 50 patients completing the active phase. The number of days of mild tooth sensitivity during the active phase was 0.9 +/- 1.3 days for the experimental agent group and 1.1 +/- 1.5 days for the Colgate Platinum group.

Effect of powder/liquid ratio on the clinical and laboratory performance of resin-modified glass-ionomers.

OBJECTIVES: To compare the effects of powder/liquid (P/L) ratio and surface wetness on retention of adhesive Class V restorations. METHODS: One-hundred and six Fuji II LC restorations were placed at two clinical trial sites. In the 'high-dry group (Site A), Fuji II LC was mixed at a P/L ratio of 3.0 and applied to dentine that was visibly dry, but not desiccated. In the 'low-wet' group (Site B), Fuji II LC was mixed at a P/L ratio of 2.25 and applied to dentine that was glisteningly moist. The restorations were evaluated at baseline, 1 and 2 years at both sites, and at 3 years at one site. The P/L ratio effects on viscosity and wetting were evaluated in vitro by determining the film thickness possible at different ratios. RESULTS: At 2 years the retention levels at the two sites differed significantly (p < or = 0.1). Site B ('low-wet' group) exhibited 100% retention, and Site A ('high-dry' group) exhibited 78% retention. At 3 years Site A exhibited 74% retention, and nine of the 12 retention failures occurred in patients 65 years and older. Laboratory measurements demonstrated that the viscosity of 'low-wet' mixtures permitted film thickness that were one-half those of the 'high-dry' group. CONCLUSIONS: The study demonstrated that a higher powder/liquid ratio and a drier dentine surface compromised wetting by a resin-modified glass-ionomer resulting in a decline in retention from baseline to 3 years. This study suggests that the dentine surface should be kept hydrated to promote bonding, and that the powder/liquid ratio should be low enough to create low-viscosity mixtures which promote wetting. In the 'high-dry' dentine group there was still 74% retention at 3 years, indicating that factors other than wetting affect retention.

Effect of a re-wetting agent on the performance of acetone-based dentin adhesives.

PURPOSE: To compare the in vitro bond strengths of two acetone-based one-bottle dentin adhesives applied to four surface moisture conditions. The tested hypothesis was that wetting a dried dentin surface with an aqueous HEMA solution would result in bond strengths similar or higher than those obtained by leaving the surface moist as per manufacturers' instructions. MATERIALS AND METHODS: Eighty flat dentin bonding sites were polished to 600-grit on middle dentin of the labial surface of bovine incisors mounted in acrylic resin. The specimens were equally and randomly divided between two acetone-based dentin adhesives (One-Step and Prime & Bond 2.1) and four different levels of surface moisture (moist dentin, dentin dried for 1 s, dentin dried for 5 s, and dentin dried for 5 s followed by re-wetting with Aqua-Prep, an aqueous HEMA solution). A composite post was then adapted to the treated area and light-cured. After thermocycling, the bond strengths were determined by testing the specimens in shear. Field Emission SEM examinations were carried out to evaluate the effects of different treatments on the dentin-resin interface. RESULTS: Statistical analysis revealed that the application of One-Step resulted in similar mean shear bond strengths for the groups in which moisture was present on the dentin surface (12.0-14.2 MPa). The mean shear bond strengths for the group in which One-Step was applied to a dried dentin surface was significantly lower (6.0 MPa). For Prime & Bond 2.1, the application of a re-wetting solution significantly increased mean shear bond strengths (13.9 MPa). The remaining three Prime & Bond 2.1 groups yielded statistically similar mean bond strengths, regardless of the surface condition (6.6-8.1 MPa).