Predictors of initial stability of orthodontic miniscrew implants

The purpose of this retrospective study was to elucidate potential confounding factors affecting initial stability of miniscrews inserted to enhance orthodontic anchorage. Four hundred and seven miniscrews inserted in 168 patients treated by 17 orthodontic residents were analysed in a consecutive chart review. The outcome variable was the stability of the miniscrew, measured as a dichotomous variable, 0 if the miniscrew loosened during a 1 week period after insertion to the time of orthodontic force application and a value of 1 otherwise. Potential confounding variables examined were gender, age, jaw, insertion site, tissue type, length and diameter of the miniscrew, and number of previous insertions. Generalized estimating equations (GEE) methods were used to estimate the influence of each factor on stability for the correlated binary outcomes of each patient. A weighted analysis for the GEE approach was also performed for the convergence calculation of the estimation procedure due to a value of 0 in one of the cells. Crude odds ratio (cOR) and adjusted odds ratio (aOR) and their 95 per cent confidence intervals (CI) were calculated for this purpose. The overall success rate after 1 week was 93.1 per cent (379/407). The screws inserted by more experienced clinicians (more than 20 miniscrews) were found to have approximately a 3.6-fold higher success rate of initial stability compared with those inserted by less experienced clinicians after adjusting for the insertion site (aOR = 3.63, P = 0.015). The results of the present study suggest that the initial stability depends on insertion site and clinician experience.     

Painless swelling proved to be a central giant cell granuloma

A 32-year-old female patient was referred to an oral and maxillofacial surgeon with an asymptomatic swelling in the left mandibular premolar region. After extraction of these premolars and enucleation of the lesion histopathological examination confirmed the presence of a giant cell granuloma. This is a benign lesion and enucleation generally results in a permanent cure and is only recurrent in a few cases. Approximately 1 year after treatment, the patient was still free of recurrence and together with a prosthodontist, the appropriate rehabilitation of the resulting defect will be sought.     

A survey of program directors: trends, challenges, and mentoring in prosthodontics. Part 1.

PURPOSE: This study consisted of two parts. Part 1, a survey of program directors, was conducted to examine current trends in advanced education in prosthodontics in the United States. Part 2 will report on the survey results distributed to the deans of US dental schools to evaluate their observations of trends in prosthodontics. MATERIALS AND METHODS: A national e-mail survey of 45 program directors was used to collect enrollment data for years 1 to 3 of prosthodontics training for US and international dental school graduates, the total number of applicants and applications considered, and the trends over time of applicants to prosthodontic programs for US dental school graduates and for international graduates. In addition, the program directors were asked to rank 13 key factors that may have contributed to any changes in the prosthodontic applicant pool. Comments were accepted on why more or less US- or internationally trained applicants have applied. Program directors were also asked for information on student financial incentives, whether their programs were state or federally funded, and whether their sponsoring institution was a dental school. RESULTS: Of the 45 program directors, 39 responded, for an 86.7% response rate. Respondents reported that 64% of their enrollments were graduates of US dental schools. Between 2000 and 2004 the applicant pool in prosthodontics increased by 23%, with 41% of program directors reporting an increase in US-trained applicants, 46.2% reporting no change, and only 12.8% reporting a decrease. Using the Spearman correlation, there was a moderate, positive statistically significant correlation that the following factors contributed to an increase in the number of US dental graduates applying to prosthodontic programs: (1) mentoring by prosthodontists at the predoctoral level, (2) interest in prosthodontics among US dental students, and (3) society's demand for a higher level of training and credentialing, (4) data depicting current and projected income for dental specialists, and (5) number of trained prosthodontists full- or part-time faculty at the predoctoral level. Only five programs offered no financial packages to offset tuition. The remaining 34 respondents reported some financial package. Among the respondents, there were 25 state-sponsored programs, 9 sponsored by private universities, and 5 sponsored by hospitals or federal agencies. CONCLUSION: An increased applicant pool and more US-trained applicants to prosthodontics programs create a more competitive applicant pool for our specialty. Program directors reported that factors such as mentoring, society's demand for a higher level of training and credentialing, data depicting current and projected income for prosthodontists, exposure to prosthodontic faculty at the predoctoral level, the dollar value of prosthodontic training, and advances in implant, aesthetic, and reconstructive dentistry have all had some impact on increasing the applicant pool to prosthodontic training in the United States.     

Salivary nitrate--an ecological factor in reducing oral acidity

Human oral cavities represent a novel environment with a constant supply of concentrated nitrate. For humans, over 80% of dietary nitrate originates from fruit and vegetables. With a healthy, balanced diet, rich in fruit and vegetables, the concentration of nitrate in saliva can reach up to more than three times the European drinking water standard. The physiological function of the active excretion of salivary nitrate is unknown. Furthermore, little is known of the ecological function of oral nitrate and the effect on the oral environment during its subsequent oral microbial conversions. The objectives of the research were to investigate the effect on salivary pH coupled with oral microbial nitrate and/or nitrite reduction. Human saliva samples were incubated anaerobically in the presence of 111.0 mmol glucose (2%), with and without 1.5 mmol nitrate/nitrite, and pH and nitrate/nitrite consumption were measured during the time-course of the incubations. We found that anaerobic incubation of saliva containing a mixture of oral bacteria in the presence of nitrate/nitrite substrates and glucose resulted in a higher pH than was found in controls in the absence of nitrate/nitrite. These results suggest that the presence of these electron acceptors repressed acid fermentation, or increased alkali production, or consumed acid produced, thus reducing salivary acidity. This finding identifies salivary nitrate as a possible ecological factor in reducing oral acidity. The possibility that a symbiotic relationship between host nitrate excretion and nitrate-reducing microorganisms might help to protect against tooth decay should be explored further.     

Nanomechanical and chemical characterization of incipient in vitro carious lesions in human dental enamel

OBJECTIVE: The research was designed to examine the growth of in vitro carious lesions in dental enamel using nanoindentation and time-of-flight secondary ion mass spectroscopy (TOF-SIMS). This was intended to give maps of mechanical properties and chemistry over the cross-section of the lesions. METHODS: Incipient carious lesions were grown on the buccal faces of 20 human premolars by exposure to acid for 3, 5, 7 or 14 days. The lesions were then cut in cross-section normal to the exposed surface. The lesions' cross-sections were then examined using nanoindentation and TOF-SIMS. RESULTS: The earliest lesions (3 days of acid exposure) showed little evidence of lesion growth, but the 5, 7 and 14 days of exposure all gave lesions with a weak, demineralized interior, but a stronger, less demineralized surface zone. The thickness of the surface zone was found to diminish with the length of exposure to acid, but it was still present even after 14 days of exposure. CONCLUSION: The results indicate that carious lesions develop subsurface and that the surface zone forms by a coupled diffusion process. Mechanically the lesion has a strong surface layer, but a very weak interior which makes the lesion vulnerable to mechanical loading. However, the presence of a surface zone that retains a high mineral content and is mechanically strong suggests that lesion development can be arrested and possibly reversed even when the lesions are relatively mature.     

Total Etch—The Rational Dentin Bonding Protocol

Phosphoric acid etching of dentin is critically reexamined in view of current adhesive resin development. Research and clinical experience both suggest that "total etch," the simultaneous etching of dentin and enamel, is a rational protocol with many modern adhesive resins.     

Bactericidal effects of human neutrophils and sera on selected endodotic pathogenic bacteria in an anaerobic environment

Phagocytosis by normal human neutrophils and the bactericidal activity of normal human pooled serum were measured under anaerobic conditions on six endodontic pathogenic bacterial species from the genera Actinomyces, Bacteroides, Fusobacterium, Peptostreptococcus and Streptococcus. The results revealed that Actinomyces viscosus was not killed either by human neutrophils or by 20 per cent serum; Peptostreptococcus anaerobius was not killed by either 20 per cent or 95 per cent serum; and Bacteroides intermedius was susceptible to both 20 per cent and 95 per cent serum, but was not killed by neutrophils after exposure for 20 minutes. The other species showed intermediate susceptibility patterns. Such results suggest that oral pathogens vary with regard to the bactericidal effects of these two host defense mechanisms, and that this variation may at least in part explain the relative quantities of microbes recovered in certain oral infections.