Effect of masticatory simulation on the translucency of different types of dental zirconia.

STATEMENT OF PROBLEM: Translucent zirconia has been marketed to dentists seeking to provide esthetic monolithic dental restorations. Evidence on differences in translucency between recently introduced translucent zirconia and conventional zirconia before and after fatigue testing with thermocycling is lacking. PURPOSE: The purpose of this in vitro study was to evaluate the effect of fatiguing and thermocycling on the translucency of 5 mol% yttria partially stabilized zirconia (5Y-PSZ) and 3 mol% yttria partially stabilized zirconia (3Y-PSZ) at clinically relevant thicknesses. MATERIAL AND METHODS: Translucent zirconia (BruxZir Anterior Solid Zirconia [5Y-PSZ]) and conventional zirconia (BruxZir Shaded Zirconia [3Y-PSZ]) were evaluated. Disk-shaped specimens were prepared to 0.7-mm and 1.2-mm thicknesses for each zirconia type. Four groups (n=10/group) were evaluated. Translucency parameter (TP), contrast ratio (CR), and light blockage percentage (Lb%) were recorded by using an integrating sphere spectrophotometer before and after fatiguing (1.2 million cycles at 110-N load with simultaneous thermocycling at 5 °C to 55 °C). Data were analyzed by repeated-measures analysis of variance for statistical significance (α=.05). CR values were compared with the reported 0.06 translucency perception threshold of the human eye. RESULTS: A statistically significant difference was found in TP, CR, and Lb% between 5Y-PSZ and 3Y-PSZ (P<.001). Thickness had a statistically significant effect on TP, CR, and Lb% (P<.05). The 0.7-mm thickness groups were more translucent and had lower Lb% than the 1.2-mm thickness groups (P<.001). Baseline ranking from most to least translucent according to TP and CR measurements was as follows: 5Y-PSZ (0.7 mm), 3Y-PSZ (0.7 mm), 5Y-PSZ (1.2 mm), and 3Y-PSZ (1.2 mm). Lb% was 64% at the 1.2-mm and 56% at the 0.7-mm thickness in the 3Y-PSZ groups. Lb% was 61% at the 1.2-mm and 53% at the 0.7-mm thickness in the 5Y-PSZ groups. None of the groups, before and after fatiguing, had a CR value exceeding the clinically perceivable 0.06 translucency perception threshold value. CONCLUSIONS: Translucent (5Y-PSZ) and conventional (3Y-PSZ) zirconias evaluated in this study displayed degrees of translucency that were inversely related to the zirconia thickness. 5Y-PSZ was more translucent and blocked less light than 3Y-PSZ, but this difference may not be perceivable to the human eye. Both 5Y-PSZ and 3Y-PSZ were optically stable after fatiguing and thermocycling.

The erosive potential of additive artificial flavoring in bottled water.

Acidic beverage consumption is a well-recognized contributor to extrinsic dental erosion. Although the pH values of some commercially available bottled waters are below neutral pH, water is still considered to be a safe and healthy choice. Artificial flavoring liquids or powders, known as water enhancers (WEs), have been introduced to the market to modify the taste of water. The purposes of the present study were to measure the pH and titratable acidity of WEs and to perform gravimetric analysis of teeth immersed in solutions of WEs mixed with different brands of bottled water in order to determine the erosive potential in vitro. The pH and titratable acidity using 0.1M sodium hydroxide were calculated for 7 brands of WEs added to 3 brands of bottled water, which had different initial pH values. Extracted human molar teeth were submerged in each combination of solutions for gravimetric analysis. Distilled water was used as the positive control and citric acid as the negative control. Data were analyzed with 2-way analysis of variance and post hoc Tukey-Kramer testing (P = 0.05). The pH value (2.9-3.0) and titratable acidity (32.2-35.3 mmol/L hydroxide) of all of the experimental solutions were considered acidic, regardless of the WE brand. Average tooth structure loss after 1 month of immersion in the solutions was 4%, and surface changes were consistent with erosive dissolution. The results showed that adding a WE to water significantly increases the potential for dental erosion. The high content of citric acid in WEs is believed to be the cause. Patients should be advised to use WEs with caution.

Survey of dentists to determine contemporary use of endodontic posts.

STATEMENT OF PROBLEM: Although the scientific literature provides sound decision-making tools for the restoration of endodontically treated teeth, dentists have different opinions on the rationale for the use of endodontic posts (dowels) and selection of post systems. The decision to place a post is at times contrary to the literature. Updated information on the treatment of endodontically treated teeth among general dentists is lacking. PURPOSE: The purpose of this survey was to gain insight into the rationale for choice of endodontic posts and the different endodontic post systems currently used by dental practitioners. Post and core restorations distribute stress and replace missing tooth structure in endodontically treated teeth. Guidelines exist to help select post systems. With the advent of new materials, prefabricated posts have gained popularity among dentists. However, cast-metal post-and-core systems are still considered the gold standard. MATERIAL AND METHODS: Surveys were distributed to dentists attending continuing education meetings in the United States, Canada, Scotland, Ireland, and Greece. The questions addressed years of practice, specialty training, and brand, type, shape, and material of the endodontic post systems used. RESULTS: Descriptive statistical analysis was used to assess the percentage of respondents. Ninety-two percent of the participants were general practitioners with 25.94 ±13.35 years of experience. The majority agreed upon using endodontic posts when insufficient coronal tooth structure remains and for stress distribution. Passive, parallel posts were the most commonly reported type and shape. With regard to post material, fiber posts were the most frequently used (72.2%), followed by prefabricated alloys (38.6%), cast-metal posts (33.9%), prefabricated titanium posts (30.1%), and stainless-steel posts (21.7%). For cementation, resin-modified glass ionomer (40%) was most frequently used, followed by self-adhesive resin (29.6%). CONCLUSIONS: The majority of the practitioners used fiber posts. This may be because, in terms of fracture, they compare favorably with cast-metal post and core, although little evidence in the literature validates this claim.

Gingival displacement: Survey results of dentists' practice procedures.

STATEMENT OF PROBLEM: A high percentage of fixed prosthodontic restorations require a subgingival margin placement, which requires the practice of gingival displacement or a deflection procedure to replicate the margins in impression. PURPOSE: The purpose of this study was to learn the different gingival displacement techniques that are currently used by dentists in their practice and to compare the current concepts of gingival displacement with previously published articles. MATERIALS AND METHODS: A survey of questions pertaining to gingival deflection methods was distributed as part of continuing education (CE) course material to dentists attending CE meetings in 7 states in the U.S. and 1 Canadian province. Question topics included initial patient assessment procedures, gingival displacement methods, dentist's knowledge and assessment of systemic manifestations, and brand names of materials used. RESULTS: Ninety-four percent of the participants were general practitioners with 24.11 ± 12.5 years of experience. Ninety-two percent used gingival displacement cords, while 20.2% used a soft tissue laser and 32% used electrosurgery as an adjunct. Sixty percent of the dentists used displacement cords impregnated with a medicament. Of the preimpregnated cords, 29% were impregnated with epinephrine, 13% with aluminum chloride, and 18% with aluminum potassium sulfate. CONCLUSION: The study showed a steady decrease compared with results of previously published articles in the use of epinephrine as a gingival deflection medicament.

Education About Dental Erosion in U.S. and Canadian Dental Schools.

Dental erosion (DE) is a well-accepted multifactorial form of tooth wear involving acids. Due to its irreversible nature, recognizing the early signs is important to develop appropriate preventive strategies. However, its place in dental curricula remains unclear. Consensus has not been established regarding the integration of erosive tooth wear into core cariology curricula in North America. The extent to which DE is taught is questionable since etiology, risk assessment, and management are not all the same as for dental caries. The aim of this study was to survey U.S. and Canadian dental schools regarding their teaching of DE. Email invitations were sent to deans, chairs, and selected faculty members at all 76 U.S. and Canadian dental schools in 2016, asking them to either respond or forward the survey-link provided to the appropriate person in their school. Responses from the same school were combined for analysis. Respondents from 59 schools (77.6% response rate) responded to the survey, and all of them confirmed the inclusion of DE in their curricula. However, only 15.3% of respondents identified correctly all the clinical signs of DE. Although management through behavioral intervention was prioritized, diet analysis was often not a clinical requirement, and 45.8% of respondents did not teach any type of tooth wear index for monitoring. This study concluded that DE has a place in dental curricula, but whether this topic is adequately covered is questionable. There is a need to establish clearer topics and requirements emphasizing the diagnosis and management of DE, potentially in cariology curricula.

Teaching Silver Diamine Fluoride in U.S. Dental Schools' Predoctoral Curricula.

Silver diamine fluoride (SDF), a low-cost topical agent used in many countries to arrest dental caries, was cleared as a desensitizing agent by the Food & Drug Administration for the U.S. market in 2014. The aim of this study was to survey U.S. dental schools regarding their teaching of SDF. Email invitations were sent to all accredited U.S. predoctoral dental education programs (n=66) in September 2016. Deans, chairs, and selected faculty members were asked to respond or forward the survey-link provided to the appropriate person in their school. Under the assumption that some respondents from the same school were unaware of SDF implementation across departments, multiple responses from the same school were collapsed for analysis. A total of 62 schools (94% response rate) responded to the survey, and 67.7% of them reported that SDF was part of their curricula. There was a wide variation across dental schools' teaching about SDF indications and protocols of application. All but one school consistently agreed on using SDF for arresting caries on primary teeth. Only 18 respondents were able to confirm if there was an existing protocol at their school for the use of SDF. When re-application after initially arresting caries with SDF was taught, 50% of respondents advocated 2×/year re-application. Schools not teaching SDF (n=20) planned on including it in their curricula in the future. These findings suggest that, with the use of SDF increasing rapidly in the U.S. and its adoption in most dental schools, there is a need for the development of standardized evidence-based protocols.

The quality of fixed prosthodontic impressions: An assessment of crown and bridge impressions received at commercial laboratories.

BACKGROUND: The authors evaluated and quantified clinically detectable errors commonly seen in impressions sent to commercial laboratories and determined possible relationships between finish line errors and other factors involved. METHODS: The authors visited 3 large and 1 small commercial dental laboratories over a 12-month period. Three calibrated examiners evaluated the impressions. The examiners evaluated all impressions for errors by using ×2.5 magnification loupes under ambient room lighting without the aid of additional illumination. RESULTS: The authors evaluated 1,157 impressions; 86% of the examined impressions had at least 1 detectable error, and 55% of the noted errors were critical errors pertaining to the finish line. The largest single error categories evaluated were tissue over the finish line (49.09%), lack of unprepared stops in dual-arch impressions (25.63%), pressure of the tray on the soft tissue (25.06%), and void at the finish line (24.38%). The factors blood on the impression (odds ratio, 2.31; P < .001) and tray type (odds ratio, 1.68; P < .001) were associated significantly with finish line errors. CONCLUSIONS: Marginal discrepancies made up the largest category of error noted in impressions evaluated. The authors noted an increase in errors at the finish line with dual-arch impression techniques and in the presence of blood. PRACTICAL IMPLICATIONS: Dentists have ethical, moral, and legal obligations bestowed on them by the profession and need to evaluate critically the work they send to laboratories. The authors strongly recommend an improvement in technique and reviewing of all impressions and working casts.

The selection of contemporary restorative materials: anecdote vs. evidence-based?

The contemporary practitioner is faced with a bewildering number of options from which to choose when selecting restorative materials. There are not only many different types of materials available, but also numerous options for any given group of materials. For example, many manufacturers offer their customers three or even four different dentin bonding agents. The sheer number of available products is in itself overwhelming. When coupled with aggressive marketing strategies, misinformation supplied by paid clinicians at many seminars and lectures, and infomercials disguised as scientific articles in many of the trade journals, it is little wonder that the average ethical practitioner is frustrated when attempting to make rational choices. Clinicians use information gleaned from a variety of sources to make these difficult decisions. This article will attempt to evaluate the validity of these sources and will provide a philosophical matrix to assist the practitioner in making rational decisions relative to materials selection.

Longevity of the tooth/restoration complex: a review.

The contemporary dentist has a wide variety of materials to utilize in the restoration of defective teeth. The decision as to which restorative approach should be utilized in any given clinical situation is a joint one between the patient and the treating dentist. The dentist's primary obligations are to understand the indications and contraindications of various materials, understand how to optimally manipulate those materials, and educate the patient so that they make intelligent decisions and give proper informed consent. The ultimate decision as to which approach to use rests with the patient, and the patient must clearly understand the benefits and risks associated with different restorative options. Clearly, one of the important considerations with any treatment is the prognosis and restoration longevity. When attempting to predict the long-term prognosis of any restoration, it is important to consider both the restorative material being considered as well as the specific tooth that is being restored. Many times the amount of remaining tooth structure has a more significant bearing on long-term prognosis than what material is used for restoration. Thus, the tooth/ restoration complex must be considered as a whole when predicting potential longevity. Many clinical trials have been conducted to attempt to answer those questions, and relatively few unbiased, unambiguous answers are available. The only completely honest answer to those questions is "It depends". This is because the prognosis of all restorative therapy depends on the complex interaction of a number of variables, some of which are controlled by the dentist, and some of which are totally out of the dentist's control. This article will attempt to delineate some of the factors related to the long-term prognosis of the tooth/restoration complex, and specifically identify factors that decrease the prognosis of the tooth/restoration complex.

Selection of luting agents, part 1.

The clinical success of indirect restorations is dependent on multiple factors that include preparation design, mechanical forces, restorative material selection, oral hygiene, and selection of a proper luting agent. The selection of the luting agent is dependent on the specific clinical situation, the type of restoration utilized and the physical, biologic, and handling properties of the luting agent. Although it is important to choose the best luting agent for each clinical situation, far greater variations in physical properties result from improper manipulation of a given luting agent than exist between different types of cements. One study listed loss of retention as the third-leading cause of prosthetic replacement, with failure occurring after only 5.8 years in service. The primary purpose of the luting procedure is to achieve a durable bond and to have good marginal adaptation of the luting material to the restoration and tooth. Conventional cements have always relied upon retention and resistance forms in tooth preparations; Adhesive-type luting agents offer the clinician an added advantage by bonding to the tooth structure. Three main types of conventional "cements" are commonly used, zinc phosphate and the polyelectrolyte cements polycarboxylate, and glass ionomer cements. Because of its long history of successful clinical use, zinc phosphate is considered the gold standard against which all other luting agents are compared because of its long clinical history of successful use. Currently, two additional types of luting agents have gained considerable popularity. These include the resin-modified glass ionomer cements and resin cements. The resin cement category includes light-cured, dual-cured and chemically cured agents. The purpose of this article is to discuss the ideal attributes of a luting agent and make clinical recommendations for their use.

Cervical margin design with contemporary esthetic restorations.

The contemporary dentist has a wide variety of options to use in the restoration of extensively damaged or previously restored teeth. Metal-ceramic and all-ceramic crowns are frequently used to restore esthetics and function. One of the essentials for success with either option is proper tooth preparation, which includes proper selection and preparation of the cervical margin of the preparation.

Current concepts in gingival displacement.

Gingival displacement is an important procedure with fabricating indirect restorations. Gingival displacement is relatively simple and effective when dealing with healthy gingival tissues and when margins are properly placed a short distance into the sulcus. Several techniques have proven to be relatively predictable, safe,and efficacious. No scientific evidence has established the superiority of one technique over the others, so the choice of technique depends on the presenting clinical situation and operator preference.

A review of contemporary impression materials and techniques.

The contemporary restorative dentist has a host of impression materials available for making impressions in fixed prosthodontics,implant dentistry, and operative dentistry. With proper material selection and manipulation, accurate impressions can be obtained for fabrication of tooth- and implant-supported restorations. This article outlines the ideal properties of impression materials and explains the importance of critical manipulative variables. Available impression materials are analyzed relative to these variables, and several "specialized" impression techniques are described. Special attention is paid to polyvinyl siloxane impression materials because they have become the most widely used impression material in restorative dentistry.

Esthetic considerations with removable partial dentures.

The reduction in partial edentulism that has occurred due to successful preventive procedures and the predictable use of osseointegrated implants has reduced the need for removable partial dentures. However, for a variety of reasons, many patients can continue to benefit from partial denture therapy; and these patients deserve the best esthetic result possible. The primary esthetic objection to removable partial denture therapy is the unsightly display of the clasp assemblies. This article describes three strategies that can be used by the discriminating clinician to eliminate the display of the clasp assembly and provide an esthetic and functional removable prosthesis.

The role of all-ceramic crowns in contemporary restorative dentistry.

A large number of all-ceramic alternatives to metal-ceramic restorations are being marketed aggressively to the dental profession. Most of these all-ceramic alternatives have little or no scientific evidence to support their use. This article present guidelines for clinicians to analyze new ceramic systems and specific indications and contraindications for use. It is suggested that before practitioners consider using an all-ceramic system, they make sure that published clinical trials document a survival rate of at least 95 percent over five years. In addition, each system should be evaluated to determine whether it delivers the esthetic results anticipated.