International Journal of Periodontics & Restorative Dentistry, 06/1995

The final color of all-ceramic restorations is mainly dependent on the light-transmission characteristics of the different components of the ceramic material. This article is a report on the improvement in light reflection and light transmission possible with the new In-Ceram Spinell crown system, which provdes a natural- looking appearance.

Histologic studies of periodontal reconstructive therapies have repeatedly shown a zone of nondescript connective tissue adaption, or collagen adhesion, to the root surface between the apical extension of the junctional epithelium and the coronal extension of identifiable regenerated cementum. To clarify the nature of this zone, supra-alveolar periodontal defects were created bilaterally in the mandibular premolar region in three beagel dogs,and exposed roots were instrumented to remove the cementum. Flaps were then coronaly advanced and sutured. Histologic analysis after 12 weeks of healing showed instrumented root dentin not associated with junctional epithelium, new cementum, root resorption, or ankylosis in 27 of 60 root surfaces. In 10 of these specimens subsequently examined by transmission electron microscopy, collagen fibrill were generally oriented parallel to and in close proximity to the root. A mechanism of collagen attachment was, in fact, functioning at sites of collagen adhesion; these areas may validly be included in the histologic attachment level reported in studies of periodontal reconstructive therapy.

When maxillary sinus grafting is performed to allow placement of fixed restorations in edentulous posterior sites, standard procedures involce placement of the sinus graft and then, after a graft-maturing time, placement of implants, which must osseointegrate before they can be used to support a restoration. Transplantation of a preosseointegrated implant from the mental area to the graft site may be preferabel to standard two-step procedures. Advantages of the transplant procedure include redction in total treatment time, a more predictable therapeutic outcome, and, it appears, improved bone quality, configuration, and retention around the implant.

The gain in open probing attachment level as a result of a guided tissue regeneration procedure with Gore-Tex Periodontal Material was measured in 62 sites. The incidence of complications was evaluated. When sites with a complication were compared to those without complication, there was no statistically different gain or loss of newly regenerated tissue. However, the occurance of sloughing of the gingival flap decreased the amount of gain in open probing attachment level. Analysis of the data also revealed that the combined use of allografts and a delay in the removal of the Gore-Tex Periodontal Material had a synergistic positive effect on the gain in open probing attachment level. No association between these treatment variables and the incidence of the complications was found.

Of concern with the use of preangled abutments on implants is the transmisson of masticatory forces and the angle at which they occur. Nineteen endosseous implants were placed in two subhuman primates. After 6 months, to allow for osseointegration, the implants were fitted with preangled abutments of vaious degrees and restored with type IV alloy castings. Straight abutments were used as control. Histologic evaluation revealed, that after one year of service, the implants exhibited complete osseointegration. Implants, whether restored with straight or preangled abutments, had no adverse effect on the surrounding bone. Soft tissue pockets measured, on average, from 2.2 to 2.6 mm; acute and chronic inflammatory cells were present. When crown loss was observed, it was caused by mechanical failure of components, such as gold screws and the screws used to secure te preangled abutments to the implants. Preangles abutments appear to be a valuable adjunct in implant dentistry, although long-term studies are needed for confirmation.

Periodontal healing after use of Atrisorb barrier material (polylactic acid) for guided tissue regenreation was studied in the premolar and molar teeth of six beagle dogs. Defects studied were surgically induced or were caused by naturally occurring periodontitis. Barriers fragmented and became displaced in 2 to 5 weeks after application. Granulation tissue was sometimes present between the barrior and root surface at 10 days to 4 weeks. Several sites were surgically reentered at 4 months, and new bone covered 60% to 100% of the formarly exposed furcations and root surfaces. Sites obtained for histologic evaluation 9 to 12 months after the baseline surgery showed new connective tissue attachment, cementum, and alveolar bone. Histomorphometric analyses quantitated these tissue changes, and new connective tissue attachment covered 72% of surgically exposed root surfaces and 77% of periodontitis-exposed root surfaces. It was conlcuded that the new periodontal supporting tissues became reconstituted on root and furcation surfaces after use of the Atrisorb barrier material for GTR.

The purpose of the present study was to evaluate the effect of barrier membrane exposure on the success of guided tissue regeneration in Class II furcation defects. Twenty-six subjects with mandibular Class II furcation defects received initial periodontal therapy followed by guided tissue regeneration surgery. The membrane was placed and the flaps were repositioned so that the membrane was totaly submerged. Membranes were removed 4 to 6 weeks later, at which time the extent of their exposure was recorded. An overall improvement in all clinical parameters was observed for all subjects 1 year after surgery. Half of the patients had experienced no membrane exposure, while the other 13 subjects had experienced mild to pronounced exposure; both groups showed similar improvement in all clincal and surgical parameters. In light of the comparable results obtained in exposed sites, and the anatomic difficulties sometimes encountered in covering a membrane completely,in some of these cases the membrane may be left only partially submerged, This approach will allow for tighter occlusal seal of the tooth-membrane interface and preserveation of the keratinized gingiva.