Evaluation of replica techniques for the surface ultrastructure of rodent and human palatal mucosa

Root-end cavity preparation using the MicroMega Sonic Retro-prep Tip. SEM analysis

The objective of this laboratory study was to compare root-end cavities prepared with sonic Retro-prep tips in a MM1500 Sonic Air handpiece with those created by burs in a conventional handpiece. A total of 80 single-rooted extracted human teeth with mature apices and straight canals were included in the study. Four groups of 20 extracted teeth were prepared as follows: I, a 3-4 mm root-end resection perpendicular to the long axis of the root, with a size 40 sonic Retro-prep tip creating an apical cavity 3 mm into root canal system; II, a 45 degrees bevel of the root-face removing a 3-4 mm root segment and root-end preparation as per group I; III, root-end resection as per group I, with an apical cavity prepared using a size 010 inverted cone bur 3 mm down the long axis of the root; IV, resection as per group II, followed by an apical cavity preparation with a size 010 inverted cone bur 3 mm into the root canal system. The apical root portion and root-end cavities were replicated and prepared for SEM analysis at x 20 and x 80 magnification. The degree of chipping associated with the margin of the root-end cavities, as evaluated with a standard grading system, and the incidence of root-face cracks were noted. Marginal chipping of root-end cavities prepared using sonic instrumentation was significantly worse than that produced by burs (P < 0.001). Perpendicular root-end resections showed significantly better scores than bevelled root-end resections (P < 0.005). The incidence of root-face cracking was low with no significant difference between the experimental groups.

A SEM study of denture plaque and oral mucosa of denture-related stomatitis

The aim of this study was to compare the morphology of denture plaque and adjacent palatal mucosa in five subjects with denture-related stomatitis and a control group of five healthy subjects. Scanning electron microscope examination of copper plate replicas, which preliminary studies established were superior to epoxy resin replicas, showed that there were no consistent differences between the morphology of denture plaque and adjacent mucosa in the denture-related stomatitis group and control group. In each, the surface of the denture plaque was composed predominantly of coccoid- and rod-shaped bacteria with only some yeast cells. The mucosa was largely devoid of microorganisms and individual epithelial cells were shedding from its surface.

A new method to assess damaging effects on the gingival tissues of non-surgical instrumentation

A method of assessing the damaging effects of non-surgical instrumentation was developed. To test the technique, the effect of cavitational activity in the water supply of an ultrasonic scaler was investigated in an in vivo situation. Using a replication technique for the scanning electron microscope, it was shown that the water supply of the ultrasonic scaler caused superficial disruption of the surface of the gingiva, distant from the area of damage caused by mechanical contact. The results indicated that further investigations of this phenomenon using the technique were required.

Scanning electron microscopic investigation of changes in the dentogingival area during experimental gingivitis

The purpose of this study was to investigate the changes that occur in the dentogingival area during experimental gingivitis using a replication technique and scanning electron microscopy (SEM). The upper 1st premolars of 20 subjects were examined prior to plaque accumulation, after plaque had become clinically visible and after 3 weeks plaque accumulation. 3 distinct zones were examined: the tooth surface and its integuments, the gingival crevice and the oral gingiva. Surface features such as perichymata, pits, depressions and cracks were rapidly covered by plaque deposits. These had a raised globular surface with occasional embedded desquamated epithelial cells. Raised plaque colonies were frequently seen by the end of the study. Initially, the gingival crevice presented a layered undulating appearance. With plaque accumulation many desquamating epithelial cells were seen and variations occurred in the width of the crevice. These changes were mirrored in the oral gingiva. The junctional epithelium was initially smooth with occasional pores and emigrating leucocytes. As plaque accumulated, the presence of pores and leucocytes increased and considerable disruption by desquamating epithelial cells was noted. No subject proved resistant to the influence of plaque-induced changes.

Effects of cavitational activity on the root surface of teeth during ultrasonic scaling

It is recognised that roughness of the root surface will occur during ultrasonic scaling and this has been attributed to the vibrating scaling tip. Although the presence of cavitational activity and acoustic microstreaming forces have been described their effects on the root surface have not been fully evaluated. Utilising an in vitro system of polished gold, it was possible to demonstrate an indentation produced by the scaling tip. However cavitational activity around the tip within the water supply appeared to produce an area of erosion (0.66 +/- 0.3 mm2, 1 SD, n = 10), and the surface appeared pitted. A scanning electron microscope study (SEM) of root surfaces following ultrasonic scaling showed similar areas of erosion. A replica technique was utilised so that control and experimental root surfaces could be observed. Cavitational activity and acoustic microstreaming resulted in a superficial removal of root surface constituents, and this area of removal was measured as 0.7 +/- 0.3 mm2 (1 SD, n = 10), which was not significantly different from that area observed with the gold surface system (p greater than 0.1). It may be concluded that cavitational activity within the cooling water supply of the ultrasonic scaler results in a superficial removal of root surface constituents.