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Experience with virtual reality-based technology in teaching restorative dental procedures.

This article reports on extensive experience with advanced simulation at the University of Pennsylvania, School of Dental Medicine (UPSDM). Virtual reality-based technology (VRBT) or advanced simulation is currently available for the instruction of dental students in preclinical restorative procedures. UPSDM was one of the first schools in the world to have extensive experience with VRBT technology using an advanced simulation unit (DentSim) from DenX, Ltd. UPSDM's experience consists of several years of research using control and experimental groups, employing students to participate in an investigative project, and using the units for remediation and a supplement to the preclinical laboratory. Currently, all first-year students (Class of 2007 and Class of 2008) are receiving most of their preparative operative training on the VRBT units. UPSDM started with one (beta) version unit in 1998, which was later updated and expanded first to four units and recently to fifteen units. This communication is presenting the studies that were of fundamental importance in making the decision to acquire fifteen units in 2003. The areas of main interest to the SDM concerning this technology were its use in teaching, refreshing, and remediating students in restorative procedures and its effectiveness as a teaching methodology in relation to time, efficiency, and faculty. Several studies with varying parameters were performed at various time points. The limited statistical analysis conducted was not conclusive for all measures, and in some cases the data only suggest areas of possible significance. This is due to the low number of students who could access the limited number of available units and the change of protocols in response to student and faculty input. Overall, the results do suggest, however, that students learn faster, arrive at the same level of performance, accomplish more practice procedures per hour, and request more evaluations per procedure or per hour than in our traditional laboratories. Students' attitudes, as measured by surveys, group interviews, and private interviews, are mixed. Our overall evaluation of our experience with this technology has been positive and led to the purchase of additional units, its full incorporation into our curriculum, and curriculum revision to maximize its potential. Our conclusion is that this technology offers significant potential in the field of dental education and that further use and investigation are both desired and justified.

Computer Simulation↗

Bonding to dentin achieved by general practitioners.

The objectives of this study were (1) to investigate the effect of operator variability on the shear bond strength of adhesives to dentin and (2) to determine the effectiveness of education on bonding performance for different types of adhesives. Thirty general practitioners were recruited for a CE course by a regional mailing. They used bovine dentin as a substrate for bonding the adhesive system they routinely used in practice and two other materials (no previous experience). Each adhesive OptiBond FL, ScotchBond Multipurpose Plus, ScotchBond 1 and Clearfil SE was applied according to manufacturer's instructions and immediately tested using a shear bond strength test. Shear bond strengths between adhesives and dentin were compared before and after a 90 min lecture on bonding principles and materials. For dentists with and without previous experience with a material, there were no statistically significant differences seen before and after the lecture (paired t-tests, p < or = 0.05). However, in every case, the bond strengths after the lecture were higher than those before (range of improvement from 15 to 150%). For dentists with routine experience with a particular material, all materials were statistically equivalent after the lecture, although the OptiBond FL was the highest. For dentists who had no previous experience with a material, the ScotchBond 1 had lower bond strengths than the other materials after the lecture. There was a large range in the ability of dentists to manipulate adhesive systems correctly. However, if a dentist has sufficient experience and receives sufficient education, any of these materials can give reasonable results.

Analysis of Variance↗

Absence of HIV transmission from an infected dentist to his patients. An epidemiologic and DNA sequence analysis.

OBJECTIVE: To determine if a general dentist with human immunodeficiency virus (HIV) infection transmitted HIV to any of his patients. DESIGN: A cohort study in which all patients treated by a dentist who developed the acquired immunodeficiency syndrome (AIDS) were identified and attempts were made to contact all patients for HIV antibody testing. SETTING: A general dentistry clinic operated by the Department of Veterans Affairs in southeastern Florida. PARTICIPANTS: All patients treated by a dentist during the 5 3/4 years before he developed AIDS were identified in a computerized registry of dental care. MAIN OUTCOME MEASURES: Attempts were made to contact all living patients for counseling and HIV antibody testing. Living patients with newly identified HIV infection were interviewed, and DNA sequence analysis was performed to compare genetic relatedness of their HIV to that of the dentist. Death certificates were obtained for decreased patients, and the medical records of those with diagnoses suggestive of HIV disease or drug abuse and those dying under the age of 50 years were reviewed in detail. RESULTS: There were 1192 patients who had undergone 9267 procedures, of whom 124 were deceased. A review of the death certificates of the deceased patients identified five who had died with HIV infection, all of whom were either homosexuals or users of illicit intravenous drugs. We were able to locate 962 (92%) of the remaining 1048 patients, and 900 agreed to be tested. Infection with HIV was documented in five of the 900 patients, including four who had clear evidence of risk factors for acquiring HIV infection. One patient who had only a single evaluation by the dentist denied high-risk behavior. Comparative DNA sequence analysis demonstrated that the viruses from the dentist and these five patients were not closely related. CONCLUSION: This study indicates that the risk for transmission of HIV from a general dentist to his patients is minimal in a setting in which universal precautions are strictly observed. Programs to ensure compliance with universal precautions would appear preferable to programs for widespread testing of dentists.

Cohort Studies↗

Brief communication: prehistoric dentistry in the American southwest: a drilled canine from Sky Aerie, Colorado.

A prehistoric Native American mandible from a Fremont site (circa AD 1025) in Colorado has a conical pit in the worn occlusal surface of the lower right canine. Natural causes for this modification are ruled out by the presence of internal striae, a finding confirmed by experimental replication. The canine was artificially drilled before the individual's death and is associated with a periapical abscess. This is one of a very few examples of prehistoric dentistry in the world, and the first from the American Southwest.

Adult↗

Iatrogenic molar borings in 18th and early 19th century Native American dentitions.

Six iatrogenic dental borings were identified in four individuals of a Native American skeletal collection from an 18th and early 19th century Middle Columbia River burial site. The borings, all in maxillary first molars with severe dental attrition and secondary dentin, demonstrate striated walls and associated periapical alveolar lesions. An ethnographic review of the subsistence pattern during the burial period indicates a diet that is consistent in dental attrition with other riverine fisher-hunter-gathers. Histological changes of dental pulp tissue during the process of attrition may result in dental necrosis. Access into the pulp chamber is a technique used to drain necrotic fluid. A common Euro-American therapeutic dental practice of the 18th and 19th centuries for diseases of the pulp was dental extraction. Multiple dental borings indicate that the practice of molar drilling into the pulp chamber was an effective and independent technique used by the Wishram and Wasco people.

Dental Pulp↗

A silver staining technique for investigating wear of restorative dental composites.

A silver staining technique was developed to demonstrate microdefects in dental restorative composites. Fine silver particles were preferentially introduced into the damaged region to provide optical contrast between the damaged and the undamaged regions. The amount of silver deposition determined with an electron probe microanalyzer, provided an indication of the extent of damage within the dental composites. Examples to demonstrate this technique were given with one clinically worn dental composite restoration and one in vitro worn composite sample.

Dental Materials↗

Probing the origins and control of shrinkage stress in dental resin composites. II. Novel method of simultaneous measurement of polymerization shrinkage stress and conversion.

This study probes the interrelationships between polymerization shrinkage stress development and the polymerization progress with a novel experimental technique. This technique is capable of real time, simultaneous measurement of double-bond conversion and shrinkage stress with the use of a noninvasive near-infrared fiber-optic system, along with a cantilever beam-based tensometer. The results from both filled and unfilled bis-GMA/TEGDMA (70:30 mass ratio) systems showed that the shrinkage stress buildup was concentrated in the latter stages of polymerization, with its dramatic increase linked to the asymptotic approach of conversion to its limiting value. The monotonic increase of shrinkage stress with conversion in the vitrified state is attributed to the dramatic increase of the sample's elastic modulus during the vitrification stage and a certain amount of cooling stress as the sample cools down from the temperature rise caused by the exothermic polymerization and light absorption. Excellent reproducibility of both the polymerization kinetics assessment and the shrinkage stress measurement has been achieved.

Biocompatible Materials↗

Prospects for tooth regeneration in the 21st century: a perspective.

The prospects for tooth regeneration in the 21st century are compelling. Using the foundations of experimental embryology, developmental and molecular biology, the principles of biomimetics (the mimicking of biological processes), tooth regeneration is becoming a realistic possibility within the next few decades. The cellular, molecular, and developmental "rules" for tooth morphogenesis are rapidly being discovered. The knowledge gained from adult stem cell biology, especially associated with dentin, cartilage, and bone tissue regeneration, provides additional opportunities for eventual tooth organogenesis. The centuries of tooth development using xenotransplantation, allotransplantation, and autotransplantation have resulted in many important insights that can enhance tooth regeneration. In considering the future, several lines of evidence need to be considered: (1) enamel organ epithelia and dental papilla mesenchyme tissues contain stem cells during postnatal stages of life; (2) late cap stage and bell stage tooth organs contain stem cells; (3) odontogenic adult stem cells respond to mechanical as well as chemical "signals"; (4) presumably adult bone marrow as well as dental pulp tissues contain "odontogenic" stem cells; and (5) epithelial-mesenchymal interactions are pre-requisite for tooth regeneration. The authors express "guarded enthusiasm," yet there should be little doubt that adult stem cell-mediated tooth regeneration will be realized in the not too distant future. The prospects for tooth regeneration could be realized in the next few decades and could be rapidly utilized to improve the quality of human life in many nations around the world.

Dentistry, Operative↗

Surgical aptitude test for otolaryngology-head and neck surgery resident applicants.

The search for a convenient, rapid manual dexterity examination, which could be used at the time of the otolaryngology resident applicant's interview, led us to assess the following areas: purposeful hand direction, depth perception, tactile discrimination, finger pressure coordination, finger visual tracking of moving objects, spatial visualization, finger strength, speed of movements, fine control precision, finger dexterity, steadiness during movement, steadiness without movement, and neatness. With the astronomical increase in applicants to a limited number of positions in the field of otolaryngology-head and neck surgery, the application of an accurate, efficient manual dexterity assessment at the time of applicant interview is desirable. Presently, dental school applicants are screened by a series of manual dexterity tests. To develop our screening test, we integrated manual performance tests currently in use by private industry, occupational therapists, and dental school admission committees. Thus, applicants who are able to master fine microsurgical and macrosurgical techniques common in our specialty will be preferentially selected.

Aptitude Tests↗

Current laser dentistry.

Current laser dentistry since our initial studies in 1964 is reviewed. Three areas are considered: routine dental office practice, tooth restoration, and oral surgery. For tooth restoration and oral surgery, CO2 and neodymium:YAG lasers are used and lasers are used in photodynamic therapy for oral cancer. Dental office practice today is concerned mostly with uncontrolled studies of biostimulation and requires more basic research and controlled clinical studies. The laser industry in the United States should take a more active interest in defining the applications of lasers in dentistry.

Dentistry, Operative↗

Gamma/delta T cells and human skin reactivity to heavy metals.

Gamma/delta T cells may act as a first line of defence and respond to stress signals from the surrounding tissue. In the present investigation the occurrence of gamma/delta T cells was studied in the human skin after application of heavy metal salts by a routine epicutaneous patch-testing procedure. Gamma/delta cells were not found in normal skin. They were observed in all 14 allergic or irritant patch-test reactions to gold chloride and in 6/8 such reactions to mercuric chloride, where they comprised 16 +/- 6% and 15 +/- 6%, respectively, of the CD3+ cells in the dermis. They were also epidermotropic. Very few of these cells were found in reactions to salts of nickel and silver, except that they were increased in hair follicle epithelium in a reaction to silver nitrate. The gamma/delta cells expressed the V delta 2 and the V gamma 2 gene segments and were CD4-8-, indicating that they had the same phenotype as gamma/delta lymphocytes in the peripheral blood. Moreover, they were 'memory' T cells. These results indicate that gamma/delta lymphocytes play a role in the skin defence against highly reactive heavy metals.

Antigens, CD↗

Noise level and ultrasound spectra during burring.

The aim of this study was to evaluate the noise spectra of current dentistry equipment during normal work at the dental clinic and in the laboratory. In the study, noise was measured during the dental treatment of seven patients at a dental clinic and also in the acoustics laboratory, where working noise was simulated by drilling a polyacetal plate. All samples were analyzed in audible and ultrasonic areas in the one-third octave bands of 20-80,000 Hz. The measuring instruments used were B&K 4135 microphones, B&K 2633 preamplifiers, the B&K 2811 multiplexer, and the B&K 2133 real-time analyzer with the ZT 0318 high-frequency expansion unit. In the in situ measurements, the A-weighted sound pressure level was occasionally over 85 dB(A), and the equivalent continuous A-weighted sound pressure level, L(Aeq), was 76 dB(A). The noise level was most powerful in the one-third octave band of 40,000 Hz, where it was 74 dB. In laboratory measurements, the noise levels of the air-turbine and the micromotor hand pieces (n=16) were also most powerful in the one-third octave band of 40,000 Hz, where they were 80-89 dB. The L(Aeq) of the different micromotor handpieces (n=6) varied between 76 dB(A) and 77 dB(A), and the L(Aeq) of the turbine hand pieces (n=10) varied between 77 dB(A) and 82 dB(A). The noise of the drills is most powerful in the high frequencies, so using hearing protectors, it is possible that speech communication improves because the protectors attenuate high frequencies more than low frequencies. The very light protectors give sufficient protection against the drilling noise.

Acoustics↗

Tooth-colored restorations of posterior teeth in German dental education.

Optimizing the quality of tooth-colored restorations is one of the main topics of current research. But there is only little information available about university education in this field. The aim of this study was to collect and evaluate data about the different aspects of dental education in Germany concerning tooth-colored restorations. Based on the response to a questionnaire from 90% of all German dental schools in the fall of 1997 a detailed survey is given of the utilization, indications, practical procedure, problems and limitations of both direct and indirect tooth-colored restorations done by students. The results indicate a wide-spread use of directly inserted composite for posterior teeth in the different education programs. Indeed, the preferred preparation of the cavity margin differs from school to school. Rebuilding an adequate proximal contact and a precise fit at the gingival margin are looked upon as the main problems of class II composite fillings. Ceramic inlays are mainly inserted by students in advanced clinical courses with the insertion procedure being claimed as the main problem of this technique. The findings of this study mostly show the same limitations and difficulties of tooth-colored restorations in education as found by research. Partly different teaching concepts are reflected in the differing scientific results.

Composite Resins↗