The International Journal of Oral & Maxillofacial Implants, 06/1998

Cylindrical dental implants coated with cancellous structured titanium (CSTi) were studied in a dog model. CSTi-2-coated and hydroxyapatite-coated (HA) implants were placed in 8 mongrel dogs. The porosity of the CSTi-2 coating was 9% less than that of the previously studied CSTi-1, resulting in greatly improved mechanical strength and cosmetic appearance. A slightly lower level of bone ingrowth was observed for CSTi-2 than for CSTi-1. However, the in vivo attachment strength of the CSTi-2 coating was comparable both to CSTi-1 and to an HA-coated control after 8 weeks. Measured porosity is technique dependent; digital analysis of in vitro samples yielded higher porosity values than in vivo histology cross sections. Keywords: bone ingrowth, dental implant, osseointegration, porous coating, porous titanium

The aim of this prospective study was to evaluate the results of 2-stage maxillary sinus reconstruction using titanium implants placed into iliac corticocancellous bone blocks previously grafted to the floor of sinuses. Fifty consecutive patients received 314 Brånemark implants of varying lengths; 202 implants were placed in the grafted bone and 112 were placed in the adjacent anterior maxillary alveolar process, which had received buccal onlay bone grafts. Follow-up time was 9 to 48 months after implant placement, which was accomplished 5 months after bone grafting. Eighty-four percent of the implants were integrated into the grafted sinuses and 75% were integrated into the anterior graft. Six patients (12%) lost implants in strategic positions, leading to secondary implant placement prior to fabrication of fixed prostheses. Thirty-eight patients (76%) received fixed prostheses. Only 5 individuals (10%) attained permanent implant-anchored overdentures. One patient lost all implants. The total implant survival rate (80.9%) and the survival rate of the fixed prostheses (100%) compare favorably with other reports. Keywords: bone grafting, endosseous implants, maxillary sinus reconstruction, oral rehabilitation, two-stage

Surgical, medical, and prosthodontic records of 61 consecutively treated patients with mandibular discontinuity were reviewed retrospectively. All 61 patients had undergone discontinuity reconstruction with autogenous bone grafts; 31 of 61 had also received endosseous dental implants and a dental osseoprosthesis. Of these 31 implant-reconstructed patients, 23 had free autogenous nonvascularized and 8 had vascularized bone grafts. The surgical-prosthetic protocol consisted primarily of secondary, free autogenous nonvascularized bone graft reconstruction and secondary root-form endosseous implant and fixed prosthesis dental reconstruction. Vascularized bone (8 patients) or soft tissue (4 patients) grafts were utilized selectively for severely compromised patients after extensive oncologic resection, avulsive trauma, or after previous radiation treatment. Endosseous implant survival (95.5% in 31 patients), autogenous bone graft success (98.4% in 61 patients), and dental osseoprosthesis success (100% in 31 patients) were favorable. A high incidence (9.1%) of nonfunctioning (sleeping) implants was recorded for this patient population. The need to remove the titanium mesh tray for various reasons (17.6%) and the need to reconstruct soft tissue in the irradiated patient (12%) were noteworthy. Keywords: autogenous bone graft, discontinuity defect, endosseous implant, nonvascular, prosthesis, radiation, reconstruction, vascular

A 3-dimensional finite element analysis was conducted to assess stress distribution in bone, implant, and abutment when gold alloy, porcelain, or resin (acrylic or composite) was used for a 3-unit prosthesis. A unit force was applied axially and then buccolingually to the center of the pontic. For gold and porcelain, similar maximum equivalent stress was found in each part of the models. In almost all cases, stress in the model with the resin prostheses was similar to or higher than that in the models with the other 2 prosthesis materials. The highest increase in stress with the resins was found in the implant-abutment unit under axial load. The protective role of resin for the implant-bone interface could not be demonstrated under the conditions of this analysis. Keywords: dental implants, fixed partial prostheses, prosthesis material, stress, 3-dimensional finite element analysis

Limited bone height restricts the use of long dental implants, so short implants may be selected in these situations. Recent reports on clinical results with short implants have been negative, however, and have suggested that indications for the use of these implants are limited. To verify these findings, a multicenter study of short ITI implants was carried out. In a 6-year period 253 short implants with a length of 6 mm were placed into 126 patients, who were followed up from 1 to 7 years. Altogether 7 implants were removed; 6 of these were located in the maxilla and 1 in the mandible. The quality of survival was comparable with the clinical results of longer implants from the same implant system. Although the clinical results of these short implants were favorable, it is recommended that they be used in combination with longer implants, especially when used in the less dense bone that is often seen in the maxilla. Keywords: atrophy, clinical results, nonsubmerged, short dental implants

Forty-three sites in 16 patients were selected for placement of implants using osteotomes in a single-stage surgical technique. Most sites were treated to enhance bone quality. Sixteen sites in the posterior maxilla had sinus elevation performed in conjunction with implant placement. No soft tissue coverage of the implant cover screw was attempted in either the sinus-elevated or the nonelevated sites. Sinus elevation was significant relative to baseline (mean gain 3.25 mm, P .01). The implant survival rate was 95.3%. Keywords: bone quality, dental implant, endosseous, human, implant surgery, osteotomes, ridge expansion, single stage surgery, sinus elevation, sinus grafting, site development

The aim of this study was to make a comparative analysis between the bone response to machined and sandblasted implants. The sandblasting was done with 150-ìm aluminum oxide particles. Under scanning electron microscopic examination, the machined implants presented typical machining grooves, while a very rough, highly irregular surface with depressions and indentations was present on the sandblasted implants. Light microscopy showed a different bone growth pattern on machined (implantopetal growth) and sandblasted (implantofugal growth) implants. No negative effects on the rate of bone growth were observed in spite of the presence of aluminum ions. The histomorphometric analysis showed that sandblasted implants presented, from the third week onwards, a significantly higher contact percentage (P .0001). These values could point to higher osteoconductivity as a result of the higher surface roughness of sandblasted surfaces. Keywords: bone growth, sandblasting, surface roughness, titanium implants

This study measured maxillary sinus volume as an aid in determining the volume of graft bone needed before grafting autogenous bone to the maxillary sinus floor. Maxillary sinus volumes were measured from computerized tomographic images of 38 sinuses using a 3-dimensional reconstruction system. When the sinus-lift procedure was simulated, volumes (mean ± SD) of the inferior portion of the sinuses were 4.02 ± 1.44 cm3 for 15-mm lifting and 6.19 ± 1.77 cm3 for 20-mm lifting. In bone grafting of the maxillary sinus floor, taking into consideration individual differences in maxillary sinus volume and resorption of the grafted bone, 5.46 cm3 or more were required for a 15-mm lift and 7.96 cm3 or more were required for a 20-mm lift. Keywords: bone grafting, computerized tomographic image, maxillary sinus floor, maxillary sinus volume, simulation

Between 1990 and 1995, 214 implants were placed in 29 maxillae and mandibles of 22 patients following extraction of all residual teeth as a consequence of severe periodontal disease. All patients were discharged wearing immediate dentures. The implants were analyzed with regard to the number per arch, location, length, and diameter. The 5-year cumulative survival rate was 98.5%. The mean number of implants per arch was 7.5 for the maxilla and 7.2 for the mandible. The preferred implant locations were canines, central incisors, lateral incisors, and second premolars in the maxilla; and lateral incisors, first molars, and canines in the mandible. The mean implant length was 14.7 mm in the mandible and 14.5 mm in the maxilla. The mean implant diameter was 3.8 mm in the maxilla and 3.8 mm in the mandible. The results of the present study indicate that immediate implantation for fixed full-arch reconstruction can be considered a viable treatment alternative in patients with severe periodontal disease. Keywords: immediate implantation, residual teeth extraction

This in vitro study attempts to delineate the role of extracellular matrix (ECM) constituents at the epithelial tissue-implant interface. To know which ECM constituents have a beneficial influence on the behavior of epithelial cells, the attachment, proliferation, morphologic pattern, and differentiation or cytoskeletal organization of human oral epithelial cells on ECM-coated (type IV collagen, fibronectin, type I collagen, laminin, and vitronectin) and noncoated titanium surface have been evaluated and compared. In each experiment comparing commercially pure titanium and oxygen plasma-cleaned titanium, the same ECM constituents were used. In this study, type IV collagen could provide an excellent substratum for epithelial cell attachment on titanium surface, but vitronectin-coated titanium revealed lower effectiveness for attachment of epithelial cells than noncoated titanium. These results suggested that type IV collagen could be used as a means for obtaining good epithelial seal, whereas vitronectin could be used to restrain the attachment of epithelium to dental implants. Keywords: cell attachment, cell proliferation, extracellular matrix protein, implant, oral epithelium, titanium

Hot isostatic pressing (HIP) was used in a new procedure to produce hydroxyapatite (HA) coatings on a commercially pure titanium (cpTi) substrate for osseous implantation. Eighteen HIP-processed HA-coated implants were placed in the inferior border of the mandibles in 2 Labrador retriever dogs and left submerged for 3 months. As control specimens, 12 sandblasted cpTi implants were placed in the same mandibles and, to compare the bone reaction, 2 additional plasma-sprayed HA-coated implants (Integral) were placed. Tissue reactions at the bony interfaces of the implants were studied in ground sections with the implants in situ, using ordinary, fluorescent, and polarized light microscopy and scanning electron microscopy (SEM). The HIP-processed HA coatings displayed an increased density in light microscopy and SEM as compared to plasma-sprayed coatings. Direct bone-implant contact was found in all 3 types of surfaces. However, the production of new bone was far more abundant for the HA-coated implants than for sandblasted cpTi implants. The presence of bone-forming and bone-resorbing cells indicated active bone remodeling in the interface area at 3 months after implant placement. The present results support the view that epitaxial bone growth may occur from the HA-coated implant surface. It was concluded that the increased density of the present HIP-processed HA material does not reduce the bioactive properties of the coatings. Keywords: experimental study, hydroxyapatite implants, light microscopy, scanning electron microscopy, titanium implants

The aim of the present study was to compare the cleansing properties of mechanical supportive care for dental implants with the use of an etching gel. Sixteen patients underwent a 5-month clinical trial with monthly recalls. These patients, wearing maxillary complete dentures and mandibular overdentures supported by a bar device on 4 implants, were treated in a split-mouth study design. Test and control therapy were randomly assigned to left and right sides of the mandible. At the test side, 35% phosphoric etching gel (pH 1) was applied in the peri-implant sulcus. After 1 minute, the sulcus was thoroughly rinsed with a water spray for approximately 15 seconds per implants. Control therapy consisted of supra- and subgingival debridement using carbon fiber curettes and a rubber cup. Plaque, calculus, probing pocket depth, and modified Gingival Index were determined before each treatment. Microbiologic evaluation was performed at baseline, 1 month later, and 5 months later, just before and immediately after each treatment. Per treatment and per assessment, the mean scores of all clinical parameters were calculated for each patient. The number of colony-forming units was used as the primary efficacy variable in the analysis of microbiologic data. At baseline, no differences between test and control sites were observed for any of the clinical parameters. The mean Gingival Index and the mean probing pocket depth were reduced over the 5-month period. The mean reduction in Gingival Index at the test sites proved to be significantly larger at the control sites (P = .03). Both treatment modalities resulted in an instant reduction of the number of colony-forming units, where the reduction by chemical cleaning was larger (P .05). This short-term study employing a high recall frequency indicates that local application of 35% phosphoric acid gel can be as effective as conventional mechanical supportive therapy. Keywords: acid gel, implant, maintenance

This in-vivo study aimed to investigate the load on the working-side implant and on the edentulous distal mucosa of the nonworking side in a mandibular implant-retained overdenture (MIR-OVD) anchored to 2 implants by either a ball- or a clips-and-bar attachment. Three female patients were provided with duplicate dentures anchored in the 2 ways. Strain on the implant was investigated using a strain-gauged abutment, and load on the mucosa was measured using a suitably placed load cell. Ball attachments appeared to provide greater stability to the MIR-OVD, since load was more evenly distributed onto the distal mucosa of both sides. When the MIR-OVD was bar-anchored, axial load on the working-side abutment increased. Keywords: ball attachments, bar, implants, load, overdenture, strain gauges

This paper describes the design and fabrication of a soft liner-retained, implant-supported overdenture used in 10 patients over a period of 1 to 6 years. A final complete denture impression is made of the dental arch, including implant abutments extending 5 mm above the gingival tissue. The master cast is fabricated with actual abutments placed in the impression. After the final wax try-in, the denture is flasked in the usual manner with the metal abutments in place. Before packing with acrylic resin, plastic tubing 1 to 2 mm thick is placed around each abutment. The denture is trial packed and allowed to bench cure over night. The plastic tubing is then removed and a soft denture lining material is placed in these areas only. The flask is closed and cured according to the manufacturers recommendation. The denture is delivered as a conventional overdenture. Keywords: dental implant, overdenture, soft liner, treatment planning

Traditionally, the procedure of implant placement requires a surgical periosteal flap to be raised. In a percentage of implant cases, there is no need for flap surgery for implant placement, or for a follow-up surgical procedure for abutment connection. In this clinical investigation, 20 maxillary and mandibular implants were placed in seven adult male patients. The sites for implant placement were prepared according to an alternative surgical technique without raising a surgical flap. Patients were recalled periodically for 2 years to evaluate healing and clinical integration of implants. The results showed normal clinical healing at the first week of reexamination in all implant sites; periodontal probing of less than 2 mm circumferentially around all healing caps at 3 months and later at subsequent recall periods; no radiolucency observed in the peri-implant zone; no sign of clinical mobility during recall examination; and no persistent or irreversible sign or symptoms of pain, infection, or necrosis. This alternative surgical technique can provide several advantages over the traditional 2-step procedure. Keywords: alternative surgical technique, implant placement, surgical flap

Because of the frequent lack of bone in the posterior maxilla, sinus augmentation has become a commonly practiced treatment modality. Many different materials have been used for augmenting the sinus, and the ideal graft is yet to be found. The present article reports the results of sinuses grafted with calcium sulfate in 2 patients. Bone biopsies were harvested 9 months after the augmentation procedure. In the first patient, 3 titanium threaded-cylinder implants were placed in the grafted area after 9 months, while in the second, 1 acid-etched, screw-shaped titanium implant was placed simultaneously with the graft. Light microscopic evaluation revealed new bone formation with ongoing remodeling and progressive lamellar maturation in the specimens. No remnants of the alloplastic material were detectable in any section, either within the bone or in the medullary tissue. When reevaluated at the uncovering procedure, the implants were radiographically and clinically judged to be osseointegrated. These observations suggest that, when used in the appropriate form and with the proper technique, calcium sulfate is a promising graft material for sinus augmentation, producing adequate quantity and quality of new bone for implant placement. Keywords: bone apposition, bone grafts, bone substitute, calcium sulfate, maxillary sinus