International Journal of Periodontics & Restorative Dentistry, 05/2002

This study considered the loading configuration of intact teeth by using finite element analyses to rationalize the clinical and biologic advantage inherent to posterior tooth shape. The biomechanical behavior of opposing molars was investigated in consideration of different loadcases simulating working, nonworking, and vertical closing micromotions starting in a position close to maximum intercuspation. The resulting stress distribution was assessed in a numerical model, reproducing 2-D buccolingual cross sections of maxillary and mandibular molars. In each case (working/ nonworking/closure), the stroke was applied to the mandibular tooth in a stepping procedure (nonlinear contact analysis) until a total external force of 200 N was attained on the contact nodes. The principal stress distribution and modified Von Mises stresses were extracted from the postprocessing files. Vertical loading of the teeth did not generate harmful concentrations of stress. More challenging situations were encountered during working and nonworking micromotions, both of which generated inverted stress patterns. Supporting cusps were generally well protected during both working and nonworking cases (mostly subjected to compressive stresses). Nonsupporting cusps tended to exhibit more tensile stresses. High stress levels were found in the central groove of the maxillary molar during nonworking micromotion and at the lingual surface of enamel of the mandibular tooth during single-contact working micromotion. The occlusal load configuration as well as geometry and hard tissue arrangement had a marked influence on the stress distribution within opposing molars. Additional computations demonstrated the essential role of enamel bridges and crests to protect the crown from harmful tensile stresses.

This report presents a novel surgical approach of a one-stage maxillary sinus elevation using a bone core containing a preosseointegrated implant harvested from the mandibular symphysis. As a result, the elevation of the floor of the maxillary sinus and the placement of the implant were achieved at the same time, and the required healing time was significantly reduced. Three months after placement of the implant in the symphysis, a bone core containing the implant was retrieved using a trephine. The bone core was placed in the resorbed posterior maxillary ridge, thereby elevating the maxillary sinus floor. The bone core containing the implant was allowed to heal for 5 months, after which the implant was restored and followed up for 30 months. This technique represents a surgical modification intended to avoid the conventional two-step sinus elevation surgery in which the surgical procedure of graft placement is followed by surgical implant placement. This approach requires significantly reduced healing time and provides an increased bone quality around the implant, which is of clinical importance, particularly in the posterior maxilla.

The relationship between radiographic crestal alveolar bone mass and changes in clinical periodontal attachment level following guided tissue regeneration (GTR) was evaluated in this retrospective study. A total of 12 intrabony two- or threewalled defects and 12 adjacent nondiseased proximal sites in 10 nonsmoking adult subjects received subgingival debridement and GTR using resorbable (Resolut; five sites) or nonresorbable (Gore-Tex; seven sites) barrier membranes. At a mean of 48.8 months posttreatment, clinical periodontal attachment level alterations were measured, and crestal alveolar bone mass changes on digital subtraction radiographic images derived from serial periapical radiographs were analyzed to correct for between-film geometric and contrast density differences. Intrabony defects exhibited a mean clinical periodontal attachment level gain of 2.3 ± 0.4 mm, in contrast to a mean loss of 0.5 ± 0.2 mm in adjacent nondiseased interproximal sites. Digital subtraction radiography revealed an increase in crestal alveolar bone mass at all intrabony sites treated with GTR and a decrease in three of the adjacent nondiseased sites. Site-based analysis yielded an odds ratio of 36 (P .001) for the association between radiographic increases in crestal alveolar bone mass and clinical periodontal attachment level gains of >= 2 mm. These results suggest a strong concordance between digital subtraction radiographic assessments of crestal alveolar bone mass and clinical periodontal attachment level in evaluating the long-term effects of GTR at human interproximal intrabony defects.

Replacement of two adjacent teeth in an anterior maxilla with deficient hard and soft tissues appears to be the utmost challenge in implant dentistry in the esthetic zone. In this case report, baseline conditions for implant placement were improved by alveolar distraction to enhance hard and soft tissues around the maxillary central incisors. Three months after the active phase of distraction, the roots of the central incisors were extracted and two screw-type dental implants were immediately placed into the extraction sockets. For immediate provisionalization, acrylic resin crowns were fabricated on UCLA abutments, providing the ideal emergence profile to support the periimplant soft tissue. Six months after implant placement, the prosthetic restoration of the case was finished with ceramic crowns cemented to individually fabricated zirconium oxide abutments. The described treatment strategy appears to have a great potential to restore natural esthetics in cases with major tissue deficiencies in the esthetic zone.

The purpose of this study was to evaluate two variations of the subepithelial graft. Two hundred consecutively treated patients received subepithelial grafts to obtain root coverage. One hundred patients were treated with connective tissue grafts combined with double pedicle grafts. The other one hundred patients were treated with connective tissue grafts combined with coronally positioned pedicle grafts. The mean root coverages were 97.6% and 96.1%, respectively. When the overlying pedicle was a double pedicle, there was a larger increase in the amount of keratinized tissue (3.0 mm versus 1.8 mm). When the preoperative recession depth was 5.0 mm or greater and a connective tissue graft was combined with a coronally positioned pedicle, there was less mean root coverage. The results of this study confirm that the subepithelial graft is an effective method to obtain root coverage. Additionally, the type of pedicle used to cover the connective tissue graft can affect the results.

It has become widely accepted that modern titanium dental implants are successful and predictable. However, there is bone loss in relation to any interface (microgap) that occurs between the implant parts when the microgap is in proximity or apical to the osseous crest. The principle of biologic width may be responsible for such bone remodeling in an apical manner. A new, biologically derived implant design that conceptually may minimize bone remodeling and promote better bone and overlying gingival contours and stability is suggested. The parabolic occlusal platform of this design is in harmony with the biologic width of the soft tissue around the circumference of the implant when the proximal bone is occlusal to the facial and lingual bone. Preservation of proximal bone for an isolated implant, and between implants, will help support and maintain physiologic and cosmetic gingival contours and papillae. This is of particular importance in esthetic areas, where interproximal bone loss between implants or between an implant and an adjacent tooth may cause a reduction in gingival papilla height.

The authors report on the fracture of a standard endosseous dental implant 11 years after placement. It had been connected to a natural tooth using a nonrigid connector to compensate for the lack of a built-in antirotational system on the prosthetic abutment of the implant restoration. Scanning electron microscopy revealed striations on the fracture surface, suggesting a fatigue-associated failure.

The purpose of this study was to compare the effectiveness of three methods using calcium sulfate as a graft/barrier for the treatment of Class II mandibular furcation defects. Thirty-six defects in 17 patients were treated with a graft/barrier of pure calcium sulfate, calcium sulfate plus doxycycline, or demineralized freezedried bone allograft (DFDBA) in a 2:1 ratio by volume. Defects were randomly selected for treatment, and all measurement parameters were standardized to a light-cured acrylic resin stent at baseline and 6, 9, and 12 months. Linear regression, ANOVA, and chi-squared analysis revealed that all three groups showed significant bone fill (P .05), vertical and horizontal probing depth reduction, defect volume reduction, and a gain in vertical clinical attachment. Furthermore, the addition of either doxycycline or DFDBA to calcium sulfate significantly enhanced the clinical outcome more than did the calcium sulfate alone, and the addition of DFDBA was more effective in the treatment of Class II mandibular furcation defects than doxycycline.

Prehardened medical-grade calcium sulfate hemihydrate was placed as a grafting material for sinus floor elevation in the left posterior maxilla. After 8 months of healing, three titanium plasma-sprayed screw implants (Biolock) were placed. At the same time, a bone biopsy was harvested for histologic evaluation. The specimen was processed according to standard techniques for hard tissue histology. In both the grafted area and the previously existing area of sinus floor, the histology showed complete calcium sulfate resorption and the bone was primarily of lamellar structure. In the 5-month radiograph, a new trabecular design appeared from the periphery of the grafted area, and on the 8-month radiograph, the graft material was no longer detectable and the augmented area was filled by new tissue showing a trabecular design. This case report documented that medicalgrade calcium sulfate hemihydrate, when used as a grafting material for augmentation of the sinus floor, may lead to proper osseointegration of dental implants.