In this study, enamel surface roughness was investigated following the use of various combinations of bonding agents, burrs and polishing procedures. Orthodontic brackets were bonded to 135 premolar teeth extracted from adolescents. Subsequent to debonding and finishing, the enamel surface was gold coated and examined in the scanning electron microscope. Each 200x photomicrograph was graded according to surface roughness and assigned to one of four selected standard grades. The use of different composites and different burs showed no significant effect on the finish of the enamel surface using Chi-square tests. Only two finishing procedures had a significant effect on surface roughness. The use of a Soflex disc followed by pumice slurry resulted in the roughest enamel surface and the use of pumice alone produced the smoothest enamel surface.

The vascular architecture of the gingival crevice around rat molars was investigated using the SEM vascular casting technique. The crevicular plexus consisted of two major vascular arrangements. The first was a planar network immediately subjacent to the crevicular epithelium extending from the crest of the free gingival margin down to the epithelial attachment. Arterial supply to the planar network came from the gingiva proper, but venous drainage from the plexus was directed into the periodontal ligament plexus as well as the deeper gingival vessels. The second major arrangement was a row of twisted vascular loops sited in the middle annular third of the crevice on the buccal and lingual. These loops exhibited a more complex vascular arrangement in the col and occupied most of the volume of the col tissue. The planar network in the interproximal col region narrowed to a thin band adjacent to the epithelial attachment. The morphological arrangements described in this project modify the description of Kindlova and Matena (1962) which has been accepted as a model for vascular architecture of the gingival crevice.

The vascular architecture of the rat molar periodontal ligament was investigated using the SEM vascular casting technique. Vascular patterns varied within the different regions of the tooth socket. A different microvascular arrangement was found to be associated with (i) the buccal and lingual walls (ii) the interdental septum and (iii) the interradicular septum. Tracts of four to six vessels coursed occluso‐apically down the buccal and lingual walls. A similar pattern existed at the interdental septum except that the vessels were more closely packed. At the interradicular septum, the postcapillary venules coursed within the ligament for only 100 to 400 μm before re‐entering the bone. Overall, vessels were predominantly postcapillary venules with a lesser number of capillaries. Anastomoses between adjacent vessels coursing in the ligament occurred infrequently, although many communications with the alveolar plexus were noted. Except at the interradicular septum, ligament vasculature arose mainly from the deeper gingival vessels. A few vessels originated from branches of the alveolar plexus, forming a hairpin loop as they entered the plexus. These findings differed markedly from Kindlova & Matěna's (1962) description of morphologically paired arterial and venous systems. On a morphological basis vascular flow was considered to be directed from the coronal down to the apical region of the socket. However, Ligament vessels adjacent to the vertical walls of the interradicular septum received a greater arterial supply than the crestal region, where venous drainage was more prolific. Therefore, the vascular arrangement over the septum suggested a direction of vascular flow opposite to that occurring at the outer walls of the socket, although tidal flow could occur in either direction in the interradicular area.

Summary. Human premolars were obtained for sectioning following rapid maxillary expansion to observe the pattern of resorprion and cementum deposition. Some sections were demineralized and examined by light microscopy, while the root surface of adjacent sections were observed in the scanning electron microscope. The pattern of repair by cementum was noted and found to differ from normal cementum. In addition, the vascular pattern of the periodontal ligament in rat molars has been studied by methacrylate perfusion techniques. The vasculature of the inter‐radicular area differed from that over die remaining root surface because of the presence of a dense plexus of large venous vessels. It is considered that there may be a relationship between vascular architecture and the processes of cementum deposition and root resorption.

The response of the periodontal ligament to orthodontic extrusion of the incisor of a beagle was examined with light microscope and scanning electron microscope techniques. The ligament morphology was slightly altered by the procedure but was essentially normal. Teeth that were extruded and retained for 12 weeks exhibited partial relapse. Where a full thickness mucogingival flap was raised and immediately replaced in lieu of retention, continued extrusion was observed. Root resorption was observed at the interproximal region of the cervical third in three out of five specimens. The resorption had been repaired with cellular cementum.