Incidence of periodontitis recurrence in treated patients with and without cultivable Actinobacillus actinomycetemcomitans, Prevotella intermedia, and Porphyromonas gingivalis: a prospective study

A total of 98 adults previously treated for moderate to advanced periodontitis and on a trimonthly recall schedule were screened for the presence of critical levels of Actinobacillus actinomycetemcomitans, Prevotella (Bacteroides) intermedia, and Porphyromonas (Bacteroides) gingivalis. Patients with at least 2 positive sites were placed in a positive group and patients without or with low levels of these bacteria in a negative group. During the 30-month study the incidence of disease recurrence was greater in the positive group, but did not reach statistical significance. Positive patients with deeper pockets tended to be at greater risk of developing recurrent disease than those with shallower pockets. In the positive group only, both A. actinomycetemcomitans recovery and antibody levels to A. actinomycetemcomitans strain NCTC 9710 (serotype c) were inversely correlated with disease recurrence. The presence of A. actinomycetemcomitans and P. intermedia above critical levels did not reliably predict future episodes of disease recurrence in this population. The sparse recovery of P. gingivalis did not permit us to assess its diagnostic value. With the exception of P. gingivalis, for which insufficient data were available, the results indicate that the presence or absence of the above bacterial species cannot of itself serve as a reliable predictor of future episodes of recurrent disease in a population of treated patients on a regular trimonthly recall schedule.     

Effect of immune bovine milk on Streptococcus mutans in human dental plaque

The use of a mouthrinse of bovine milk containing antibodies to Streptococcus mutans resulted in an initial reduction in the numbers of recoverable Strep. mutans in a group of 9 individuals. Ten volunteers who used control bovine milk that contained no antibody activity to Strep. mutans had variable levels of plaque Strep. mutans. In addition, after culture on Mitis Salivarius and Gold's agar, the plaque Strep. mutans from subjects who used the immune bovine milk rinse formed smaller colonies than those from pre-treatment plaque and from all plaque samples of subjects who used the control rinse.     

Influence of mixing disinfectant solutions into alginate on working time and accuracy

Possible transfer of pathogens from dental surgery to dental laboratory is of concern to the profession. This study investigates changes in the working time and accuracy of an alginate impression material when mixed with solutions of selected disinfectants rather than water. The results indicate that certain disinfectant solutions, when used as a water substitute, do not modify the working time of the alginate investigated beyond acceptable limits and have no significant effect on the dimensional accuracy of that material. The use of a 0.2 per cent solution of chlorhexidene gluconate is recommended as a water substitute for the alginate investigated.     

A comparison between estimated and registered natural head posture

Using tracings of facial profiles, four observers made two independent, subjective estimations of natural head posture (NHP) in 28 adults. The results of these estimations were compared with recordings of NHP obtained through photographic registration of the same subjects. Only minor average differences (between 0 and 1.4 degrees) were found between the two methods. The differences between estimated and registered head posture found at the first and second observation, were positively correlated for both intra- and inter-observer registrations (r = 0.59-0.80 and r = 0.50-0.71, respectively). The inclination of the basion-nasion line was measured; first, in relation to the photographically registered horizontal line and, secondly, in relation to the horizontal line derived from the estimation of NHP. Both methods of measurement gave similar mean values and standard deviations. A panel comprising 18 persons was asked to compare the head orientations of two subjects in whom a marked difference between estimated and registered NHP had been recorded. In the majority of these comparisons, the profiles orientated according to the subjective estimation were judged to have a more 'natural posture' than those orientated by the photographic method. This unexpected finding is discussed.     

Bond strength of ceramic brackets with various bonding systems

The purpose of this investigation was to determine the shear and tensile bond strengths of various ceramic and ceramic-filled brackets in combination with commonly used bonding systems. One monocrystalline, two polycrystalline and one ceramic-filled plastic bracket types were tested in combination with one light-cured and two chemically-cured bonding systems. Bonding procedures were performed on properly prepared human teeth. Shear and tensile tests were performed on an Instron test machine. The shear bond strength of the mono- and polycrystalline ceramic brackets was not affected by the bonding system. There was a difference among bonding systems used with the ceramic-filled plastic bracket. Ceramic-filled plastic and polycrystalline ceramic brackets exhibited the greatest resistance to tensile force, while monocrystalline brackets showed the highest propensity for tensile fracture of the wings.     

Diagnosis of alveolar bone changes with digital subtraction images and conventional radiographs. An in vitro study

The purpose of the present study was to compare the diagnostic properties of radiographs obtained with Ultra-Speed and Ektaspeed films when analyzed conventionally radiographs and after conversion in digital subtraction images. Artificial lesions, measuring 0.5, 0.7, 0.9, and 1.1 mm in diameter, were drilled in a dry skull with slow-speed burs. Standardized radiographs were obtained by means of acrylic bite blocks and a modification of the Rinn system. The results of this study demonstrated that sensitivity in the detection of the lesions was doubled after digitizing and displaying subtraction images compared with the conventional radiographic interpretation, independent of the use of Ektaspeed or Ultra-Speed films for the original radiographs. The diagnostic information seemed to be equal in radiographs obtained from Ultra-Speed and Ektaspeed films after digitization and image processing procedures.     

Potential application of shape memory plastic as elastic material in clinical orthodontics

Polynorbornen, a shape memory plastic developed in Japan, has a glass transitional point of 35 degrees C. Once the environmental temperature exceeds the critical point, this plastic will begin to display an elastic property, then return to its original shape, if deformed. We examined whether the force generated during the elastic phase of polynorbornen could be used to displace human teeth. We found that the shape memory plastic wire of 1 mm in diameter stretched to two to three times of its original length at a temperature of 50 degrees C and a speed of 0.5 mm/sec would exert a relatively stable continuous light force of 119-156 g to move the teeth. This new material, compared with conventional elastic modules used in orthodontic therapy, exhibited a lesser degree of force degradation at a body temperature of 37 degrees C for a long period, and can be manufactured to near the tooth colour required. These advantages make feasible clinical application of the shape memory plastic in orthodontics.     

Effect of mouthrinsing after toothbrushing with a fluoride dentifrice on human salivary fluoride levels

In a recent clinical trial of sodium monofluorophosphate dentifrices, oral rinsing habits were found to influence dental caries. Thus an oral fluoride clearance study has been undertaken which was designed to test a possible mechanism for the observed effects. Eight subjects brushed with one of the trial dentifrices and then rinsed using 1 of 8 procedures of varying thoroughness. The salivary fluoride concentration measured 5 min after dentifrice application decreased significantly with increasing rinse volume, rinse duration, and rinse frequency (p less than 0.01, analysis of variance). The area under the clearance curve determined over a further 3 h was significantly higher (300%; p less than 0.01) following use of the least thorough rinsing procedure (5 ml x 2 s once) as compared with the corresponding area under the clearance curve following the most thorough procedure (20 ml x 10 s twice). These findings indicate that rinsing habits may play an important role in the oral retention of fluoride from dentifrices which may, in turn, affect their clinical efficacy.     

Effects of zinc oxide-eugenol on leucocyte number and lipoxygenase products in artificially inflamed rat dental pulp

The number of leucocytes and level of endogenous LTC4 in the pulp tissue were measured by a histological method and radioimmunoassay, respectively. When the mandibular incisor pulp was irritated by drilling a hole in the dentine without using any coolant, the number of polymorphonuclear leucocytes and lymphocytes and the concentration of LTC4 increased to 3.2, 1.9 and 1.8 times their respective levels in normal pulp 6 h after the injury. The total leucocyte number in blood collected from these rats was also increased significantly. In contrast, when the cavities cut in dentine were filled with a zinc oxide-eugenol mixture (powder: liquid 100 mg/25 microliters), the increase in the number of cells was significantly curtailed, and the LTC4 level fell to 50% of that in normal pulp within 1 h after the filling. No decrease in the LTC4 level was observed after filling with a zinc oxide-water mixture, but the level decreased in response to an increase in eugenol content in the zinc oxide-eugenol placed in the cavity. Biosynthesis of [14C]-HETE and HPETE from [14C]-arachidonic acid was inhibited by the addition of 10 microM eugenol to the pulp homogenate. Thus eugenol released from zinc oxide-eugenol inhibited the biosynthesis of lipoxygenase products and the early chemotactic accumulation of leucocytes.