Search

Fixed prosthodontics is one of the major components of clinical activity for U.S. dentists. It has been estimated that in 2010, about 36 million units of fixed prostheses were placed in the United States (R. Braswell, coexecutive director, National Association of Dental Laboratories, oral communication, Jan. 7, 2011). Assuming that there are about 140,000 active general dentists and prosthodontists in the United States, that means that the average general dentist or prosthodontist placed about 257 units during the year, or about 21 units per month. Multiplying this number by the average revenue produced for a crown in the United States (about $900) indicates that gross revenue from crowns was about $231,000 per dentist for the year. That number is about 30 percent of the average overall annual gross revenue of the approximately $780,000 reported for a general dentist by the American Dental Association (ADA). In other words, it obviously is important that dental students, and subsequently dentists, are competent in fixed prosthodontics. However, there are questions about whether this has been achieved. I routinely hear reports from dental laboratory technicians about challenges with the tooth preparations, impressions and interocclusal records they receive from their dentist clients. In my opinion, all three of those topics need immediate and in-depth attention from instructors in dental schools and dental continuing education settings. In this article, I will discuss one of those topics: methods by which dentists can make more adequate interocclusal records that are based on scientific evidence, on my observations of crowns and fixed prostheses that have been accomplished in laboratories in this country, and on opinions held by me and by the laboratory technicians at CR Foundation in the course of nearly 50 years. THE CHALLENGE WITH INTEROCCLUSAL RECORDS

A significant change is occurring in fixed prosthodontics, and, in my opinion, there is no question but that it will continue. Many dental laboratories have closed in the past few years. According to the National Association of Dental Laboratories (NADL), approximately 5,000 laboratories closed in the period from 2006 through 2013, with 9,042 laboratories now functioning (Bennett Napier, CAE, chief staff executive, NADL, written communication, April 2, 2014). Why are dental laboratories closing? One reason is that laboratory owners cannot afford to upgrade their facilities to include expensive digital technology such as scanners, milling machines and the various accessory items. Another major reason is the significant percentage of crowns being made offshore. NADL estimates that approximately 34 percent of crowns currently placed in the United States have been made offshore (Bennett Napier, written communication, April 2, 2014). A third significant reason is the lowering of laboratory prices seen nationally and the inability of small dental laboratories to compete with the laboratories that are oriented toward mass production of indirect restorations. So what does the future hold in terms of the obvious major changes now going on in the fabrication of crowns and fixed prostheses? In this column, I will discuss the changes in fabrication of indirect restorations and the various steps necessary in the primary methods of fabricating restorations, as well as compare the potential influence each technique has on dental practices and the cost of each concept. This information should assist dentists attempting to make a decision about which of the methods of crown and fixed-prosthesis fabrication to use in their practices. The techniques and times I have listed in the following information are based on my long experience mentoring numerous conventionalfixed-prosthodontic study clubs and accomplishing research about scanning and in-office milling.

T he global economic downturn has taken a toll on many dental offices. As I talk with dentists around the country and inquire about their clinical activity, some have commented that patients are not as receptive to the expensive elective procedures in which they were interested a few years ago. This reluctance probably is related not as much to patients’ actual income as it is to their fear and anxiety about the current economy and their own uncertain financial future. What can dentists and staff members do to encourage patients to become interested in the many and varied elective oral procedures that are available or to upgrade their treatment for mandatory procedures? Many articles have been published on the effect of patient education. Here, I will discuss several types of staff members who work in every dental office and who have the potential to provide patient education; suggest several methods that can be incorporated into dental practices to educate patients about oral preventive and treatment procedures; and outline methods to educate dental staff members to the level at which they can assume a proactive role in the patient education process.

P orcelain-fused-to-metal (PFM) restorations have been the dominant option in esthetic crown and fixedprosthesis restorations for about 50 years. When these restorations were introduced, there was pessimism about their value and their potential for long-term service. However, both research and clinical observation since have shown that they serve well. Research regarding the longevity of service of PFM crowns and fixed prostheses shows variable but relatively impressive results, depending on the number of units replaced, period of observation and location of the study. The method of PFM failure is apparent to clinical practicing dentists. The most destructive type of failure is breakage of a large piece of ceramic from the metal substructure. If the piece is small, the restoration can be smoothed and continue to serve. If it is a larger piece of ceramic, the restoration must be replaced. Another challenge arises when, across time, the gingival tissues recede, the crown margins become visible and the restoration is easily identified by a lay observer as a “false tooth.” Additionally, superficial color placed on crowns and fixed prostheses may abrade or dissolve from the restorations, leaving them chalky and often a lighter color than when they were placed. Again, they appear to be unnatural. Nevertheless, from a purely functional standpoint, the PFM restorations continue to serve long after they have become relatively unesthetic, and if a chip breaks from the restoration, the underlying metal substructure protects the tooth structure until some other restoration can be placed. Dentists trust PFM restorations because of their clinically observable service longevity when compared with several previous generations of all-ceramic crowns. The current generation of zirconia-based all-ceramic crowns and fixed prostheses is becoming popular. I have observed in the continuing education (CE) courses I teach that many general dentists and prosthodontists have used these restorations to a significant degree. Jim Schuck, vice president of sales and marketing of Glidewell Laboratories, Newport Beach, Calif. (the largest laboratory in the United States), estimates that use of all-ceramic restorations is increasing (J. Schuck, oral communication, April 2009). He also estimated Porcelain-fused-to-metal versus zirconia-based ceramic restorations, 2009

This critical appraisal deviates from our standard format to address a topic of great clinical interest but with relatively few published research studies.

S everal decades ago, when root-form dental implants were introduced to the profession, the implants had an external hexagonally shaped extension on the most coronal aspect of the implant. The clinician used that hexagonal extension to screw the implant body into the bone. Later, some companies introduced implants without hexagonal extensions; these were acceptable clinically if the clinician connected the subsequently placed prostheses to several implants, thus preventing rotation of the prostheses during service. Initially, most implant prostheses were multiunit implantsupported restorations fabricated over cast frameworks, with denture resin base material retaining standard denture teeth. Soon, dentists began using the implants to replace single teeth, and they used the hexagonal extensions to prevent rotation of the abutments from the implant bodies during service. They could not use implants without external extensions for single-tooth restorations because the abutments and the prostheses rotated out of the implant bodies during service. Early in the development of root-form dental implants, these external hexagonal extension designs worked adequately because most restorations were prostheses connected to several teeth. Implant manufacturers soon developed other antirotational features, such as hexagonal shapes inside the implant body or other designs inside the implants, but until the patents on these internal antirotational features expired, companies selling the concept had difficulty in penetrating the market. Now, many types of implants using various antirotational concepts are available. Most root-form implants now are manufactured with internal antirotational designs into which abutments fit, thus preventing rotation of the abutment and the prosthesis during service. In this article, I identify the available abutment types and discuss the best clinical situations in which the clinician potentially can use each.

Many new high-tech concepts and devices for dentistry have been introduced in recent years, and corresponding advertisements are predominant throughout the dental profession. Most high-tech devices and concepts are useful, some more than others. It would be difficult and costly to incorporate into dental practice every new technology that comes out on the market. It is common knowledge among most dentists that some dental procedures can be accomplished faster, easier and better with well-known, time-proven techniques, whereas other tasks are better accomplished with today's newest technologies. Dentists must weigh technology's perceived value to patients, as well as the relative efficiency of clinical techniques accomplished by conventional versus high-tech concepts when deciding whether to incorporate technology into their practices. This article has expressed my opinions about various high-tech concepts as I perceive them, and from my experience as I see them being accepted and used by the practicing profession.

In-office CAD/CAM is a reality. It allows fabrication of tooth-colored inlays and onlays, crowns and veneers in one appointment. It is especially well-suited to dentists who accomplish many single-tooth or single-quadrant restorations. As with any new technology, its cost is high, but using it can be financially feasible. Clinical and basic science investigations have resulted in positive findings on the concept. There are some significant advantages and several disadvantages. In-office CAD/CAM works well for many dentists, but practitioners should evaluate it carefully before accepting it, as it is not for everybody.

The dental laboratory industry appears to need immediate change to face many challenges, the four most significant of which are described in this column and in our column in May JADA. The first article on this subject described the current challenges facing the laboratory industry, as determined by conference attendees representing all aspects of the dental industry and related professions. This article reports on the suggestions made by attendees of this conference to solve the identified challenges.

Impressions for crowns and fixed prostheses could be better. I have offered several suggestions to improve their quality. None of the suggestions is difficult or time-consuming. The result of making better impressions will be greater longevity for the resultant restorations and happier patients, dentists and laboratory technicians.

Dental CE is mandatory for ongoing competency in dental practice. There are numerous methods of obtaining CE, some of which are highly successful and others that are of minimal value. In this article, I have described and prioritized the various methods of obtaining CE according to their effectiveness as I perceive it. CE in dentistry can be enjoyable, will allow dentists to serve their patients at a higher level of competency and will keep practitioners mentally stimulated as they learn new concepts and techniques.

It is not difficult to observe and record patient occlusal characteristics before starting simple or complex occlusal rehabilitations. If this is done, and if the subsequently placed crowns and fixed prostheses are constructed in observation of similar characteristics, clinical success usually is the result. Deviations from the suggestion to duplicate the "normal" occlusion should be made when the original natural occlusion had caused overt pathosis, or when all teeth or one arch of the teeth is being restored at one time. If this is the case, centric relation occlusion is more reproducible and easier to develop than occlusion with a shift from centric relation to centric occlusion. Peculiar requests of patients relative to occlusal positioning, or routine dependence on various devices to predetermine occlusal characteristics for rehabilitation (as is currently popular in some groups), should be considered, but they should be tempered with careful observation of preoperative occlusal characteristics.

I apologize for making some of you nervous, and perhaps even resentful, but I HAVE HAD ENOUGH! I do not like the new unethical face of my profession, where incessant seeking of more money has replaced service to the public, honesty, and self-respect. Numerous areas of major ethical concern in dentistry are identified in this article. The ongoing, if not accelerating, degeneration of professional ethics in dentistry is clearly evident to even casual observers. Improvements in professional ethics are necessary to regain our self-respect and the respect of the people we serve. All of us need to improve, including practitioners, speakers, dental schools accomplishing research, manufacturers, editors, and evaluating groups. It is time to return to honesty and to dealing with our fellow men and women in the way we would want to be treated ourselves. I do not think it is too late.

It is apparent that conventional impressions, usually made in vinyl polysiloxane or polyether material, could be better. One of the significant reasons for impressions' inadequacy is incomplete inclusion of the tooth preparation margins in the impression. There are numerous reasons for this challenge, some of which could be overcome by implementing the technique changes I have described in this column.

In spite of their significant cost, the relatively long learning curve associated with their use, frustrations during use, their occasional need for being replaced and their peculiar appearance to patients, magnifying loupes assist all types of clinical dentists in producing higher-quality dentistry. Seeing better also means decreasing operating time. Properly fitted loupes also can improve posture during operating and reduce muscle pain in the shoulders, neck and back. Working under magnification is useful, and clinicians should give strong consideration to adopting the concept.

Types of commonly used implant prostheses have been described and illustrated, including single tooth replacements, multiple tooth replacement fixed prostheses, implant and soft-tissue-supported removable complete dentures, implant-supported removable complete dentures, and fixed-detachable complete dentures.

Background Studies in different animal models and plasma analyses in humans suggest that members of the interleukin-6 (IL-6) cytokine family may be involved in the pathogenesis of congestive heart failure (CHF). Accordingly, we have examined IL-6-related cytokines in chronic CHF in humans by analysing gene and protein expression in myocardium derived from patients with end-stage heart failure and donor hearts. Methods Gene expression of cytokines/receptors of the IL-6 family was documented in myocardial samples using cDNA array hybridization and RNase protection assays. Immunohistochemistry was used to detect leukaemia inhibitory factor (LIF), IL-6 and glycoprotein 130 (gp130) in myocardial tissues. Results Myocardial gene activity was documented for the majority of IL-6 family cytokines and their receptors. Immunohistochemical analysis localized IL-6, LIF and their common receptor subunit gp130 to myocytes and vascular smooth muscle cells. LIF mRNA levels were enhanced in the left ventricles of CHF patients relative to the left ventricles of donor hearts (patients 4·6 ± 4·7 vs. donors 0·3 ± 0·3, P

RMGI is the most popular cement in North America, but several other cement types also are used for routine cementation of the most commonly placed indirect dental restorations. After many years of dominant use, RMGI appears to possess most of the characteristics desired by most dentists. When additional cement strength, translucence or a choice of cement colors is required, resin cements can fulfill those needs. However, RMGI still is an excellent choice for routine cementation of most indirect restorations.

Endothelin-1 (ET-1) is a strong bronchoconstrictor which possesses pro-inflammatory properties and is claimed to be an important mediator in bronchial asthma. The present study was undertaken to investigate whether ET-1 synthesis, in an inflammation dominated by neutrophilic granulocytes, is as pronounced as previously demonstrated in an airway inflammation dominated by eosinophils. Moreover, the authors compared the production of ET-1 and tumour necrosis factor (TNF)-alpha in rat lungs following intratracheal instillation of either lipopolysaccharide (LPS) (neutrophilic inflammation) or Sephadex (SDX) (eosinophilic). The lung tissue ET-1 messenger ribonucleic acid (mRNA) expression was not increased in LPS treated animals whereas a six-fold increase was measured after 30 min in the SDX group (p

The described double-arch impression technique provides an accurate and stable impression, accurate dies and the ability to make one or two crowns with minimal or no adjustments. Both scientific evidence and clinical observation attest to the adequacy of the double-arch impression concept, when it is accomplished in accordance with the requirements enumerated in this column.

Available information regarding the cellular and molecular mechanisms for reduced myocardial function after myocardial infarction (MI) is scarce. In rats with congestive heart failure (CHF), we examined cardiomyocytes isolated from the non-infarcted region of the left ventricle 6 weeks after ligation of the left coronary artery. Systolic left-ventricular pressure was reduced and diastolic pressure was markedly increased in the CHF-rats. The cardiomyocytes isolated from the CHF-hearts had increased resting length, reduced fractional shortening by 31% and a 34% increase in time to 90% relaxation compared to sham cells (P