The hardness and modulus of elasticity of primary molar teeth: an ultra-micro-indentation study

Objective: Baseline information on the mechanical properties of and the effect of load upon dental hard tissue is important in the development of successful dental materials. Existing methods of measuring such properties of tissue are subject to significant experimental error. This study reports on the use of an Ultra-Micro-Indentation System (UMIS) to measure the hardness and elastic modulus of primary enamel and dentine.

Methods: Primary molar teeth were sectioned, set in resin and polished. Thirty indentations were made in enamel and dentine using a Berkovitch indentor, 15 of which were subject to a load of 50 mN and 15 to a load of 150 mN. An automated computerised system converted the force/penetration graph for each indentation in to a hardness vs depth graph from which values for the mean hardness and elastic modulus were calculated.

Results: Primary enamel had a mean hardness of 4.88±0.35 GPa whilst the hardness of dentine was 0.92±0.11 GPa The elastic modulus for enamel was 80.35±7.71 GPa and that of dentine 19.89±1.92 GPa. Using linear regression analysis a significant relationship could be shown between the hardness and the elastic modulus for both enamel and dentine when loaded to 150 mN but only for dentine at 50 mN (P<0.05). In general the elasticity of tooth structure increased as the hardness increased.

Conclusion: The UMIS offers a simple and reproducible method of measuring basic mechanical properties of small samples of enamel and dentine.     

Dental school faculty shortages increase: an update on future dental school faculty

The 1999 publication of the American Association of Dental Schools (AADS) President s Task Force on Future Dental School Faculty revealed a crisis in the shortages of dental school faculty. Stakeholders from around the nation have used the AADS Task Force report to address the crisis. In addressing one of the AADS Task Force recommendations, the American Dental Education Association (ADEA), formerly AADS, gathered additional data through a new survey of dental school deans to elucidate the current state of faculty shortages. Based on this research, ADEA projects that the number of unfilled budgeted faculty positions in U.S. dental schools now approaches 400. Survey respondents identified retirement as the leading reason for full-time faculty separations, while separation to enter private practice was the second most frequent reason for leaving the institution. Offering a salary competitive with that of private practice was identified as the most critical factor in recruiting future faculty. A number of short and long-range strategies to recruit and retain faculty are presented. Ultimately, the dental school faculty shortage places in jeopardy the general and oral health of the public.     

Dentin bond strength and marginal adaption after NaOCl pre-treatment

The aim of this in vitro study was to compare the dentin bond strength and marginal adaptation of direct composite resins with and without additional NaOCl treatment after the etching process. A total of 150 cavities were prepared into disks of freshly extracted human third molars and filled with direct composite resins. Dentin adhesives of the fourth (with total etching: Scotchbond Multi-Purpose Plus, EBS, and Solid Bond), and fifth generation (one-bottle adhesives: Prime&Bond 2.1, Syntac Sprint) were used in combination with corresponding composite resin materials. Dentin disks without cavity preparation treatment served as controls. After 24 hours of storage and 24 hours of thermocycling (1150 cycles), replicas were made and push-out testing was performed. Replicas were examined regarding marginal adaptation using SEM (X200 magnification). In general, fourth-generation dentin adhesives produced better results in bond strength and marginal adaptation than fifth-generation one-bottle systems (P < 0.05). Within the fourth generation, Scotchbond Multi-Purpose Plus and EBS achieved significantly higher push-out values and percentages of gap-free margins than Solid Bond (P < 0.05). After hypochlorite treatment, dentin bond strength (-25%) and marginal adaptation (-30%) decreased significantly (P < 0.05) in all groups.     

Anesthetic efficacy of the supplemental intraosseous injection for teeth with irreversible pulpitis

The purpose of this study was to determine the efficacy of a supplemental intraosseous injection (IOI) of 2% lidocaine with 1:100,000 epinephrine using the Stabident device, after conventional anesthetic methods had failed. Patients who experienced pain during endodontic access and required a supplemental IOI using 0.45 to 0.90 ml of the local anesthetic were identified. All 37 of the patients treated had teeth diagnosed with irreversible pulpitis. Thirty-four of the teeth were mandibular posterior teeth, 2 were maxillary posterior teeth, and 1 was a maxillary anterior tooth. Patients with maxillary teeth had received infiltration anesthesia, and those with mandibular teeth had received an inferior alveolar nerve block in conjunction with long buccal infiltration. A minimum of 3.6 ml of local anesthetic was used with the conventional techniques. Modified visual analogue scales, coupled with operator evaluations, were used to measure success. The Stabident IOI was an effective supplemental anesthetic technique in 89% (+/- 5.1) or 33/37 patients evaluated. The 95% confidence interval was 74 to 97%. The IOI was successful in 91% (+/- 4.9) of the mandibular posterior teeth (31/34), and 67% of the maxillary teeth (2/3).     

Contralateral masking effects on cerebral auditory evoked potentials in man: a trial in working practice application in conservative dentistry]

In hearing the masking consists to disturb the information perception which means its reception, codeage and transmission are distorted in the auditory system. The electrophysiological technique by auditory evoked potentials on brain has permitted to study the noise effects with homolateral and contralateral masking method in monaural hearing. The results show that the noise distorts the maximal amplitude of the evoked response and lengthens latency. They do to appear a better resistance of a left ear preference and a superiority of right hemisphere corresponding: they characterize by an important development of auditory evoked potentials with or without masking. As a result for men who are exposed to excessive noise like teachers and students in Odontology, we suggest an inequality protection of auditory system considering the both ear sensibility difference.     

Determining the temperature rise in the pulp and at the root surface during pin hole drilling and placing of dentine pins

The purpose of this study was to determine the temperature at specific sites in the pulp and periodontium during consecutive dentine pin placement. Twenty extracted human permanent lower first molar teeth were used, cut flat at a depth of 2 mm from the occlusal surface and Titanium pins of medium size placed 1 mm inside the dentinoenamel junction. The middle of the mesial root, mesial apex and the bifurcation were sites of evaluation of the temperature of the periodontium using a thermocouple. Measurements of the temperature change in the pulp chamber were also performed. Consecutive hole drilling and placing of four pins caused a statistically significant increase in temperature in the pulp chamber, but failed to show a significant temperature rise at the root surface. The maximum temperature rises were below those reported to threaten pulpal and periodontal health.     

Direct detection of Streptococcus mutans in human dental plaque by polymerase chain reaction

Igarashi T, Yamamoto AA, Goto N. Direct detection of Streptococcus mutans in human dental plaque by polymerase chain reaction.
Streptococcus mutans is an etiological agent in human dental caries. A method for the detection of S. mutans directly from human dental plaque by polymerase chain reaction has been developed. Oligonucleotide primers specific for a portion of the dextranase gene (dexA) of S. mutans Ingbritt (serotype c) were designed to amplify a 1272-bp DNA fragment by polymerase chain reaction. The present method specifically detected S. mutans (serotypes c, e and f), but none of the other mutans streptococci: S. cricetus (serotype a), S. rattus (serotype b), S. sobrinus (serotypes d and g), and S. downei (serotype h), other gram-positive bacteria (16 strains of 12 species of cocci and 18 strains of 12 species of bacilli) nor gram-negative bacteria (1 strain of 1 species of cocci and 20 strains of 18 species of bacilli). The method was capable of detecting 1 pg of the chromosomal DNA purified from S. mutans Ingbritt and as few as 12 colony-forming units of S. mutans cells. The S. mutans cells in human dental plaque were also directly detected. Seventy clinical isolates of S. mutans isolated from the dental plaque of 8 patients were all positive by the polymerase chain reaction. These results suggest that the dexA polymerase chain reaction is suitable for the specific detection and identification of S. mutans.     

Dentists' attitudes and behaviors regarding domestic violence. The need for an effective response

BACKGROUND: The authors examined the attitudes and behaviors of a national sample of dentists regarding domestic violence and the barriers dentists face in intervening to help victims. METHODS: The authors surveyed a national random sample of 321 dentists by mail from November 1997 to March 1998 about their attitudes and clinical practice behaviors related to domestic violence. Survey items were developed based on the domestic violence and health care literature. The authors used the Total Design Method to maximize the response rate and analyzed data to determine differences between dentists who had received domestic violence education and those who had not. RESULTS: Eighty-seven percent of responding dentists never screened for domestic violence; 18 percent never screened even when patients had visible signs of trauma on their heads or necks. Overall, respondents intervened only minimally to help patients whom they had identified as victims. Respondents reported that the major barriers to screening were the presence of a partner or children (77 percent), lack of training (68 percent), concern about offending patients (66 percent) and their own embarrassment about bringing up the topic of abuse (51 percent). Respondents who had received domestic violence education were significantly more likely to screen for domestic violence and to intervene. CONCLUSIONS: Dentists face many barriers to identifying and helping patients who are abuse victims, yet these data suggest that education about domestic violence could help them overcome some of these barriers. CLINICAL IMPLICATIONS: We suggest that dentists follow the AVDR model when approaching abused patients in their practice: Ask about abuse, provide Validating messages, Document presenting signs and Refer victims to domestic violence specialists.     

Clinical application of a new compact computed tomography system for evaluating the outcome of regenerative therapy: a case report

BACKGROUND: The limitations of conventional 2-dimensional (2-D) radiographs have been emphasized in many studies. Because the image is a 2-D map of the 3-dimensional (3-D) tooth and periodontal tissue, these structures may be superimposed on each other. Recently, 3-D image analysis by computed tomography (CT) was introduced to dentistry, but it has been used only rarely in the periodontal field. METHODS: The purpose of this case report was to introduce the clinical application of a newly developed, compact computed tomography system for evaluating the outcome of regenerative therapy in an adult patient with periodontitis (male, aged 55 years). To evaluate the bone defects including furcation involvement, we took an intraoral radiograph and performed CT scanning on tooth #19. We recorded a number of clinical parameters at the time of surgery. We compared the images of the bone defect obtained by CT images and the conventional radiograph with the true bone defect morphology at the surgical site. RESULTS: One year after the periodontal surgery, we again took CT scans and a conventional radiograph, and the new images of the bone defect were compared and evaluated. The new CT images were reconstructed for 3-D evaluation and compared with those taken before surgery. The CT provides 3-D images of excellent quality for evaluating the morphology of the periodontal bone defect and furcation involvement. CONCLUSIONS: We consider that CT is a useful aid in periodontal examination and diagnosis, and in the prediction and evaluation of periodontal treatment outcomes.     

Radiographic and clinical assessments of destructive periodontal disease

191 subjects, aged 35-80 years, were examined for periodontal disease using radiographic and clinical means. At all approximal tooth surfaces, assessments were made of (i) the distance on radiographs between the cementoenamel junction and the most coronal level of the alveolar bone, and (ii) probing attachment loss. The results revealed that (i) a strong correlation existed between the radiographic and the clinical assessments (r = 0.80, p = 0.0001), (ii) the difference between the 2 types of assessments was within 2 mm in 92% of the tooth sites examined, (iii) the degree of agreement between the 2 methods was similar, irrespective of tooth type and tooth surface, but (iv) the agreement was poor at sites with severe periodontal tissue breakdown.