Fixed temporization and bone-augmented ridge stabilization with transitional implants

Utilization of dental implants in full-mouth restorations is now a well-accepted treatment modality, with numerous modifications and implant systems documented in the literature. The efficacy of the treatment procedure generally requires an extended postplacement healing period prior to loading the implant fixture with the stress of mastication. Until recently, clinicians have not been able to address patient comfort requirements during the healing period. The teaching objective of this article is to present and evaluate a transitional implant system used to provide function during the healing phase. The system consists of thin titanium transitional implants and a three-component overdenture that is intended to absorb the pressure during function and protect the augmented implant site and the definitive implant fixtures from the stress of immediate loading. Treatment objectives for the transitional and definitive implants are made during the initial treatment planning. Three cases are presented to document and illustrate the clinical procedure.     

Osseointegration enhanced by chemical etching of the titanium surface. A torque removal study in the rabbit

Roughened implant surfaces are thought to enhance osseointegration. Torque removal forces have been used as a biomechanical measure of anchorage or osseointegration in which the greater forces required to remove implants may be interpreted as an increase in the strength of osseointegration. The purpose of this study was to compare the torque resistance to removal of screw shaped titanium implants having an acid etched (HC1/H2SO4) surface (Osseotite) with implants having a machined surface. Two custom screw shaped implants, 1 acid etched and the other machined, were placed into the distal femurs of 10 adult New Zealand White rabbits. These implants were 3.25 mm in diameter x 4.00 mm in length without holes, grooves or slots to resist rotation. Following a 2 month healing period, the implants were removed under reverse torque rotation with a digital torque measuring device. Two implants with the machined surface preparation failed to achieve osseointegration. All other implants were found to be anchored to bone. Resistance to torque removal was found to be 4 x greater for the implants with the acid etched surface as compared to the implants with the machined surface. The mean torque values were 20.50 +/- 6.59 N cm and 4.95 +/- 1.61 N cm for the acid etched and machined surfaces respectively. The results of this study suggest that chemical etching of the titanium implant surface significantly increases the strength of osseointegration as determined by resistance to reverse torque rotation.     

Effects of guided bone regeneration around commercially pure titanium and hydroxyapatite-coated dental implants. II. Histologic analysis

The purpose of this study was to determine which treatment of a large osseous defect adjacent to an endosseous dental implant would produce the greatest regeneration of bone and degree of osseointegration: barrier membrane therapy plus demineralized freeze-dried bone allograft (DFDBA), membrane therapy alone, or no treatment. The current study histologically assessed changes in bone within the healed peri-implant osseous defect. In a split-mouth design, 6 implants were placed in edentulous mandibular ridges of 10 mongrel dogs after preparation of 6 cylindrical mid-crestal defects, 5 mm in depth, and 9.525 mm in diameter. An implant site was then prepared in the center of each defect to a depth of 5 mm beyond the apical extent of the defect. One mandibular quadrant received three commercially pure titanium (Ti) screw implants (3.75 x 10 mm), while the contralateral side received three hydroxyapatite (HA) coated root-form implants (3.3 x 10 mm). Consequently, the coronal 5 mm of each implant was surrounded by a circumferential defect approximately 3 mm wide and 5 mm deep. The three dental implants in each quadrant received either DFDBA (canine source) and an expanded polytetrafluoroethylene membrane (ePTFE), ePTFE membrane alone, or no treatment which served as the control. Clinically, the greatest increase in ridge height and width was seen with DFDBA/ePTFE. Histologically, statistically significant differences in defect osseointegration were seen between treatment groups (P < 0.0001: DFDBA/ePTFE > ePTFE alone > control). HA-coated implants had significantly greater osseointegration within the defect than Ti implants (P < 0.0001). Average trabeculation of newly formed bone in the defect after healing was significantly greater for HA-coated implants than for titanium (P < 0.0001), while the effect on trabeculation between treatments was not significantly different (P = 0.14). Finally, there were significantly less residual allograft particles in defect areas adjacent to HA-coated implants than Ti implants (P = 0.0355). The use of HA-coated implants in large size defects with DFDBA and ePTFE membranes produced significantly more osseointegration histologically than other treatment options and more than Ti implants with the same treatment combinations. The results of this study indicate that, although the implants appeared osseointegrated clinically after 4 months of healing, histologic data suggest that selection of both the implant type and the treatment modality is important in obtaining optimum osseointegration in large size defects.     

A comparative study of osseointegration of titanium implants in autogenous and freeze-dried bone grafts

PURPOSE: This study was undertaken to compare the rate and degree of osseointegration of dental implants when placed into either autogenous corticocancellous chip or freeze-dried corticocancellous chip bone grafts. MATERIALS AND METHODS: The canine ilium was used as the model site. Thirty experimental and 15 control implants were placed in 15 dogs: autogenous versus freeze-dried corticocancellous chip bone grafts around the exposed implant surfaces. In addition to the placement of control implants, the apical portion of the grafted implants acted as their own control. The implants were harvested at 1, 2, and 3 months. The evaluation of the integration process was performed by means of light microscopy, microradiography, and histomorphometry. RESULTS: Using this model, the results indicate that at 1 month there was no statistical difference in the degree of osseointegration in the two bone grafts. At 2 months, there was a statistically greater degree of osseointegration noted in the autogenous corticocancellous chip sites than in the freeze-dried bone grafts. At 3 months, the degree of osseointegration in the two groups was 70% and 33%, respectively. At 3 months, there was virtually 100% integration with trabecular bone at the control implant sites. CONCLUSION: The results indicate that at 2 months postoperatively implants placed in an autogenous bone chip graft osseointegrate to a significantly greater degree than implants placed in a freeze-dried bone chip graft, and this difference remains at 3 months.     

Loaded and nonloaded titanium versus hydroxyapatite-coated threaded implants in the canine mandible

A commercially pure titanium threaded implant was compared to a hydroxyapatite-coated threaded implant of similar geometric design and dimensions in the canine model. Bilateral posterior implants supported fixed prostheses, and some implants in the same mandibles served as unloaded control implants. Implants were evaluated clinically, radiographically, and histomorphometrically at the light microscope level to detect any differences in bone response to loaded conditions. No statistically significant differences were found between the two implant designs under loaded or nonloaded conditions with regard to mobility, probing depth, percentage of osseointegration, and crestal bone position.     

Effects of irradiation on osseointegration before and after implant placement: a report of three cases

Three patients irradiated as a part of cancer treatment, both before and after placement of endosseous implants, were studied. Total irradiation doses varied from 80 to 195 Gy in the tumor/implant area. Implants failed at a rate of 64.2% during a 3-year follow-up period. All patients developed osteoradionecrosis in the tumor cavities adjacent to the implants. The combined effects of the pre- and postoperative irradiation, in conjunction with the placement of implants, appear to challenge the limits of osseointegration. Until further knowledge is obtained regarding how such highly radiated tissue should be handled, it is recommended that if anchorage of craniofacial prostheses is attempted according to osseointegration principles, it should be performed with the utmost care.     

Histologic evaluation of osseointegrated implants restored in nonaxial functional occlusion with preangled abutments

Of concern with the use of preangled abutments on implants is the transmission 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 various degrees and restored with type IV alloy castings. Straight abutments were used as control. Histologic evaluation revealed that, after 1 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 the preangled abutments to the implants. Preangled abutments appear to be a valuable adjunct in implant dentistry, although long-term studies are needed for confirmation.     

Two-implant-supported single molar replacement: interdental space requirements and comparison to alternative options

Posterior single-tooth implant restorations are subjected to an increased risk of bending overload. A high incidence of implant fracture has been reported when using a single standard 3.75-mm-diameter implant to support a molar restoration. The purpose of this article is to demonstrate the clinical feasibility of placing two implants to support a molar restoration and to compare this treatment option to the use of a single standard implant or a wide-diameter implant. Two osseointegrated dental implants used to support a molar restoration in interdental spaces as small as 10 mm is shown to be effective and predictable in 60 restorations over the past 7 years. The use of two implants provides more surface area for osseointegration and spreads the occlusal loading forces out over a wider area, reducing the potential bending forces that would otherwise exist in a single-implant molar restoration.     

Plasma levels of interferon gamma and interleukin 10 in patients with lymphonodular toxoplasmosis

Endosteal implants fail for a variety of reasons. These include failure to osseointegrate, long-term loss of osseointegration, and invasion of a vital structure or anatomic placement that prohibits its use. This case report describes the removal of an implant because of patient discomfort secondary to invasion of the mandibular canal. These histologic findings offered a unique opportunity to examine an osseointegrated human dental implant section.     

Dental implant outcomes in postmenopausal women undergoing hormone replacement

To determine if hormone supplementation reduces the risk of failure for osseointegration of dental implants in postmenopausal women, the treatment outcomes of 116 women older than age 50, treated with 450 endosseous dental implants, were analyzed in this retrospective study. The findings indicated that hormone replacement therapy may not be linked with improved outcomes of endosseous dental implant treatment in postmenopausal women. Smoking, however, appears to significantly increase the implant failure rate in the group observed in this study.     

A new animal model for molecular biological analysis of the implant-tissue interface: spatial expression of type XII collagen mRNA around a titanium oral implant

The objective of this study was to develop an animal model to investigate the molecular biological healing events at the tissue-implant surface occurring in the alveolar bone. Newly designed mini-titanium implants (2mm in length and 1 mm in diameter) were placed in the maxilla of retired-breeder male Sprague-Dawley rats. The implants were placed in freshly drilled holes in the maxillary bone, or in an area close to the roots of the maxillary first molar. The healing phase in each group was studied histologically at 28 days and at 56 days by means of non-decalcified polymethylmethacrylate-embedded sections and decalcified paraffin-embedded sections. Initial osseointegration was observed at 28 days, with mature osseointegration seen at 56 days. Specimens with implants placed immediately adjacent to the root showed fibrous healing at the implant-tissue surface. As a pilot study, the expression of type XII collagen, a molecular marker specific to the mature periodontal ligament (PDL), was studied by in situ hybridization. There was an absence of type XII expression close to the implant surface, whereas there was a zone of type XII collagen expression closest to the bony wall. Our preliminary results indicated a significant molecular variation in the fibrous-implant interface. This model will be useful in studies of the wound-healing patterns of the extracellular matrix around oral implants specifically relevant to alveolar bone osseointegration and potential formation of PDL.     

Implant reconstruction of the jaws and craniofacial skeleton

Full oral rehabilitation with a high degree of success is now possible with osseointegrated implants. Osseointegration is a direct connection between living bone and the titanium implant at the level of the light microscope. Osseointegrated implants are currently used to replace single teeth, support fixed bridges and stabilize full dentures. These implants can also be placed extraorally for attachment of facial prosthesis. The surgical technique used to place implants intraorally into jaws or facial skeleton is performed in two stages using a local anesthetic and/or conscious sedation. During stage I surgery, holes are placed into the jaw using a series of gradually larger diameter burs until the desired diameter and depth of the bony preparation is achieved. The implant is then placed. The implant must remain undisturbed for 4 months for osseointegration to take place. Stage II surgery is then required to remove the mucosa over the implant and place the transmucosal abutment. After 1-2 weeks of healing, the restorative dentist can take an impression and fabricate the prosthesis. On occasion, it is necessary to augment the height and width of the atrophic jaw with autogenous or allogeneic bone grafts prior to implant placement. Bone grafts are sometimes placed on the floor of the nose or the floor of the maxillary sinus. Guided tissue regeneration is a technique used to generate bone within bony defects adjacent to implants. With long-term rates of success (5 years) of 99% for implants placed in the mandible and 95% for those placed in the maxilla, reconstruction of the jaws and cranial facial skeleton with osseointegrated implants has become the treatment of choice.     

Evaluation of consecutively placed unloaded root-form and plate-form implants in adult Macaca mulatta monkeys

The present paper describes 18 consecutively-treated non-human primates (Macaca mulatta) as part of a balanced block design study of 36 animals to examine osseointegration in root- and plate-form implants prepared by atraumatic preparation of bone. Clinical measurements around selected teeth and digital radiology were utilized to monitor periodontal disease and bone deposition around the unloaded implants. Once a month scaling procedures were utilized as a means of preventing further advance of periodontal disease. Results indicate that once-monthly regimen of scaling and root planing can prevent attachment loss of natural teeth and will not interfere with the healing of either type of implant; once-monthly scalings produce significant reduction in redness (P < .05) and reduced probing depths (P = .01). A second finding is that both root and blade implants show radiographic evidence of osseointegration in this primate model. The quantitative analysis demonstrates bone gain is not stabilized until 6 months after healing. The data may indicate that occlusal loading of mandibular implants at 3 months may be premature.     

The use of the Periotest value as the initial success criteria of an implant: 8-year report

Osseointegration is a histometric process that occurs gradually over a period of time. The load that an implant is able to bear depends upon, among other parameters, the quality of the bone-implant contact. For 8 years the damping capacity of 1,182 Br?nemark implants inserted consecutively in 315 patients was measured using the Periotest method. The following clinical observations were made: (1) a relationship was found between implants with a specific Periotest value range that, at the moment of the transepithelial connection, were considered to be clinically stable, asymptomatic, and whose radiograph image was not radiolucent; (2) a relationship was found between clinically nonintegrated implants with a different Periotest value range; (3) variations in the Periotest value were related to the type of bone in which the implant was placed; (4) a small percentage of borderline implants with a Periotest value between the osseointegrated and the nonosseointegrated Periotest values was detected; (5) the percentage of secondary failures was related to an initial Periotest value corresponding to a borderline implant; (6) the healing time of each implant was individualized in accordance with the successively obtained Periotest value; (7) the load and the design of the prosthesis were individualized; (8) early detection of failing implants before fabrication of prostheses is possible; (9) communication was improved between the surgeon and the prosthodontist; and (10) variations in Periotest value were related to bone remodeling. The sensitivity of the principal clinical test in evaluating osseointegration is discussed regarding the moment of its application. The use of Periotest values as an initial success criteria of an implant is proposed.     

Biological factors contributing to failures of osseointegrated oral implants. (I). Success criteria and epidemiology

The aim of this review was to offer a critical evaluation of the literature and to provide the clinician with scientifically-based diagnostic criteria for monitoring the implant condition. The review presents the current opinions on definitions of osseointegration and implant failure. Further, distinctions between failed and failing implants are discussed together with the presently used parameters to assess the implant status. Radiographic examinations together with implant mobility tests seem to be the most reliable parameters in the assessment of the prognosis for osseointegrated implants. On the basis of 73 published articles, the rates of early and late failures of Br?nemark implants, used in various anatomical locations and clinical situations, were analyzed using a metanalytic approach. Biologically related implant failures calculated on a sample of 2,812 implants were relatively rare: 7.7% over a 5-year period (bone graft excluded). The predictability of implant treatment was remarkable, particularly for partially edentulous patients, who showed failure rates about half those of totally edentulous subjects. Our analysis also confirmed (for both early and late failures) the general trend of maxillas, having almost 3 times more implant losses than mandibles, with the exception of the partially edentulous situation which displayed similar failure rates both in upper and lower jaws. Surgical trauma together with anatomical conditions are believed to be the most important etiological factors for early implant losses (3.60% of 16,935 implants). The low prevalence of failures attributable to peri-implantitis found in the literature together with the fact that, in general, partially edentulous patients have less resorbed jaws, speak in favour of jaw volume, bone quality, and overload as the three major determinants for late implant failures in the Br?nemark system. Conversely, the ITI system seemed to be characterized by a higher prevalence of losses due to peri-implantitis. These differences may be attributed to the different implant designs and surface characteristics. On the basis of the published literature, there appears to be a number of scientific issues which are yet not fully understood. Therefore, it is concluded that further clinical follow-up and retrieval studies are required in order to achieve a better understanding of the mechanisms for failure of osseointegrated implants.     

Linkage of DFNB1 to non-syndromic neurosensory autosomal-recessive deafness in Mediterranean families

A study involving the immediate loading of Br?nemark implants in the edentulous mandibles of 10 patients is reported. The design involved the immediate loading of four widely distributed implants with a transitional fixed implant-supported prosthesis at first-stage surgery, avoiding the need for a removable prosthesis. A sufficient number of additional implants are allowed to heal in the conventional manner to provide sufficient support for a definitive fixed prosthesis even if all of the immediately loaded implants fail. Preliminary results have been favorable, with all patients functioning with a fixed implant prosthesis from the day of first-stage surgery.     

Capsular synovial metaplasia as a common response to both textured and smooth implants

Recent reports suggested that the presence of synovial metaplasia in the capsular tissues of breast implants is greater with textured-shelled implants compared with smooth. Textured implants, however, have become popular only in the last few years. Therefore, the studies do not address the possibility that synovial metaplasia may be a dynamic process related to time (e.g., implant age) rather than implant shell surface. In the current study, 159 implant capsules (85 patients) removed between February of 1992 and July of 1993 at UCLA Medical Center were evaluated histologically and correlated with clinical data, including the age of implants. Synovial metaplasia was identified in 40 percent (64 of 159) of the capsule specimens. A logistic regression analysis that removed the effect of implant age demonstrated no correlation of implant shell type (textured versus smooth) with the presence of synovial metaplasia. Gel bleed, implant location, pericapsular fluid, implant rupture, and capsular contracture also did not have any significant association with synovial metaplasia in the current study. The incidence of synovial metaplasia appears to decrease with age (77 percent at < 5 years; 22 percent at > 15 years). Our findings suggest that synovial metaplasia is not rare and in fact may be a fairly common transitional histologic finding. It may be part of the common progression that occurs at the implant-capsule interface. The clinical significance remains unknown.     

In vitro attachment of human gingival fibroblasts to endosseous implant materials

In recent years, the focus of dental implant research has been the nature of the bone-implant interface associated with osseointegration, yet the transgingival portion of endosseous dental implants has received little attention. The purpose of this study was to determine the attachment of human gingival fibroblasts to three different implant materials: commercially pure titanium, non-porous hydroxyapatite, and porous hydroxyapatite. Cell attachment was quantified by radiolabeling gingival fibroblasts with tritiated thymidine and counting attached cells by liquid scintillation following incubation for periods of 20, 40, and 60 minutes. Additional studies coating implant surfaces with fibronectin were also performed. The nature of the implant material itself appeared to affect the number of attached cells. Determined on a surface area basis, fibroblast attachment was greatest to titanium followed by non-porous hydroxyapatite. Porous hydroxyapatite demonstrated the least amount of fibroblast attachment. When incubated with fibronectin at a concentration of 50 micrograms/ml, no increase in the number of cells attached to the various implant materials was observed. A small but statistically significant increase in the number of fibroblasts attached to porous hydroxyapatite at 40 minutes was observed when implant materials were pre-treated with fibronectin.     

Tissue regeneration in bony defects adjacent to immediately loaded titanium implants placed into extraction sockets: a study in dogs

In this study of six greyhound mandibles, 24 implants were placed into extraction sockets. Eighteen of the implants were connected with abutments and immediately placed into normal function, and the remaining six submerged implants served as controls. At placement, dehiscence areas were created adjacent to 12 of the implants to study bone regeneration in extended membrane-protected defects. Six of the defects were covered with expanded polytetrafluoroethylene membranes, and six of the defects were augmented with autologous bone grafts and covered with expanded polytetrafluoroethylene material. The clinical and radiographic evaluations demonstrated that all implants achieved functional osseointegration and no implants were lost. Implant sites where membranes were used to regenerate bone over dehiscence defects demonstrated a high rate of membrane exposure and variable response to treatment. On completion of the study at 16 weeks, histomorphometric analysis demonstrated osseointegration with direct bone-to-implant contact for all implants, although the percentage of contact varied considerably. Histomorphometry indicates that the quality of osseointegration may be less favorable than the clinical and radiographic result would suggest.     

Maxillary sinus augmentation using different grafting materials and dental implants in monkeys. Part I. Evaluation of anorganic bovine-derived bone matrix

The aim of this study was to evaluate clinically, histologically and histometrically the use of anorganic bovine bone matrix (i.e. Bio-oss) as a grafting material for maxillary sinus augmentation procedures. In 4 adult male rhesus monkeys (i.e. Macaca mulatta) the 1st, 2nd and 3rd maxillary molars on one side of the jaws were extracted. The remaining bone between the alveolar crest and the bottom of the sinus was then reduced to 3-4 mm. After 3 months, maxillary sinus augmentation procedures were performed on one side of the jaws in each monkey and the sinuses were grafted with the bovine bone matrix. At that time, 2 IMZ pure titanium plasma coated implants were immediately placed into the augmented sinuses (i.e. simultaneous implants-loaded group). After 4 months, 2 additional similar implants were placed into these previously augmented sinuses (i.e. delayed implants-loaded group). Four months later, the abutment connection was performed and all 4 implants were loaded with a gold-alloy bridge for 6 months (i.e. until sacrifice of the animals). The contralateral side of each monkey received the same treatment with the exception that the extractions were performed 7 months after those in the opposite side and that the implants in this side were not loaded. Thus, 2 additional study groups (i.e. simultaneous implants-unloaded group and delayed implants-unloaded group) were obtained. Clinically, all loaded implants were stable at the day of sacrifice. Histologically, the grafted sinuses exhibited significant bone formation with integration of the bovine bone matrix particles to the new bone. Direct mineralized bone-to-implant contact was greater for the delayed implant placement groups than for the implants installed simultaneously with the sinus augmentation. Furthermore, the percentage of direct mineralized bone-to-implant contact was greater in the residual bone than in the augmented area. It was concluded that the anorganic bovine bone matrix facilitated bone formation and implant osseointegration in the augmented sinuses and that the delayed implant placement in combination with the sinus augmentation procedure seemed to be preferable.