Design, maintenance and biomechanical considerations in implant placement

Successful treatment using implants involves careful consideration of fixture placement and prosthesis design if the biomechanical conditions are to be optimized. These parameters may be related to the implant/tissue interface at the individual fixture level, and thence to the relationship between the components of a prosthesis. The influence of the nature and magnitude of occlusal forces can also be significant and should be carefully assessed before placement.     

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.     

Cat scratch disease and AIDS

The success of a bar superstructure for an orbital prosthesis may be compromised by the placement and angulation of implants. The following technique describes a modification to a bar superstructure that provided the advantages of convenience, security, and consistent positioning even though one implant was lost and the angulation of implants limited accuracy.     

Bone rehabilitation to achieve optimal aesthetics

Treatment involving oral implants has established a high success rate, including implant survival on a long-term basis. The challenge facing the clinicians today is to achieve an optimal long-term aesthetic result. To address this challenge, the volume of the underlying hard and soft tissue must be restored either prior to or simultaneously with the implant placement. The learning objective of this article is to review the critical biologic and clinical criteria essential in achieving a predictable success in aesthetic enhancement of the implant site. The article discusses the five phases of ridge reconstruction, utilization of bone grafts (with or without membranes), and the use of membranes alone. Soft tissue management and augmentation in aesthetic and nonaesthetic regions are differentiated and presented. Surgical complications are recognized as a clinical reality, and exposure of the membranes is evaluated and discussed. Four cases are used to describe and illustrate the clinical procedure.     

Advances in the identification of Dirofilaria repens and Dirofilaria immitis by a PCR-based approach

Correct placement of implants is facilitated by the parameters that are already established, dictated by the struts and borders of the existing implant frame. The root-form implants should be: Contained in the anterior symphysis of the mandible. Completely encompassed in bone, without any contact with the Vitallium frame. As long as possible, to enhance biomechanical support of the superimposed bar and prosthesis. Evenly dispersed, in order to support a Hader bar. Independent of the previous implant system. Placed to fill the anteroposterior spread as completely as possible. The rationale and approach should comprise these requirements in order to achieve a predictable solution to mechanical failure of a subperiosteal implant, in an efficient manner, with the least possible trauma to the patient.     

Acute liver failure

PURPOSE: This article reviews the literature on radiographic imaging techniques and image interpretation for dental implant treatment. MATERIALS AND METHODS: MEDLINE was used to identify published peer-reviewed literature for this report. RESULTS: Radiographic images are indispensable in the evaluation of osseous structures when planning treatment for dental implants. Potential bone sites for implant placement can be assessed clinically by means of palpation or probing through the mucosa; however, diagnostic imaging provides the best means for indirectly measuring bone dimensions. After healing of the implant site, the application of radiology is useful to verify the amount of bone adjacent to the implant and that the transmucosal abutments fit the implant. Upon completion of the implant prosthesis, radiology may be used to monitor initial and long-term success of implant treatment. CONCLUSION: Recommendations for the application of radiology over the course of treatment are made for various implant cases ranging from the overdenture to the single-tooth implant.     

Use of provisional restorations to enhance soft-tissue contours for implant restorations

The objective of restoring missing teeth with implant-supported restorations should not merely be achieving osseointegration with an implant and a biomechanically sound restoration. The objective must be the esthetic and functional restoration of the missing teeth. To achieve this, proper treatment planning is critical. Precise implant placement and delicate soft-tissue manipulation during surgery will allow the restorative dentist to enhance the peri-implant soft-tissue contours with the use of provisional restorations. Empirically, it seems that the earlier the provisional restoration is delivered in the treatment process the more ideal the esthetics. Several methods of using provisional restorations to enhance soft-tissue contours are presented. The concept of immediately delivering provisional restorations on placement of an implant is discussed.     

Long-term efficacy of total SILASTIC implants: a subjective analysis

A retrospective analysis of the long-term efficacy of total SILASTIC implant arthroplasty performed before 1986 is presented. A total of 50 patients responded to subjective questionnaires regarding pain, function, complications, and overall patient satisfaction. The average age of the patients at the time of surgery was 55.1 years with an average follow-up of 13.4 years (range 10.7 to 16.9 years). Ninety-seven percent of patients reported relief from pain, and the overall success rating was 90.7%. Results were calculated based on a modification of the American Orthopaedic Foot and Ankle Society clinical rating system; the mean rating was 87.3. Attention must be directed at realigning the joint via appropriate osteotomies and soft tissue balancing procedures for increased success. Although radiographic deterioration of the implant was demonstrated in all implants, this deterioration did not correlate with patient satisfaction and should not be the sole criterion for implant removal. We conclude that total implant arthroplasty is a proven procedure for long-term relief of pain in selected patients with degenerative joint disease of the first metatarsophalangeal joint.     

Rehabilitation of patients with severely resorbed maxillae by means of implants with or without bone grafts. A 1-year follow-up study

Forty-three patients with severely resorbed maxillae who had been referred for implant treatment were assigned to one of three treatment groups: bone grafting and implant placement (graft group); modified implant placement but no bone grafting (trial group); or optimized complete dentures (no-implant group). Sixteen, 20, and 7 patients, respectively, were assigned to the three groups. At the 1-year follow-up, 10% of the implants had been lost. Only a few of the failures (3/22) occurred after prosthesis placement. The cumulative success rates were 83% in the graft group and 96% in the trial group. A substantial reduction of the grafted bone, especially of the onlay grafts, occurred in many patients. During the period from prosthesis connection to the 1-year follow-up, marginal peri-implant bone loss was on average 0.5 mm. Despite the often demanding procedures involved, all but one patient in each implant group said that they would undergo the treatment again. Most patients were very satisfied with the treatment outcome and their improved masticatory ability. Those who had renounced implant treatment appeared modestly adapted to their optimized dentures, but reported retention problems and less satisfaction with mastication.     

Ten-year results for Br?nemark implants immediately loaded with fixed prostheses at implant placement

This investigation was initiated to develop a method to provide patients with a fixed provisional prosthesis placed at the time of implant placement. Sixty-three standard 3.75-mm Nobel Biocare implants of varying lengths were placed into mandibular sites in 10 patients and followed for up to 10 years. Twenty-eight implants were immediately loaded at implant placement, providing support for fixed provisional prostheses, while 35 adjacent implants were allowed to heal submerged and stress-free. Following a 3-month healing period, the submerged implants were exposed and definitive reconstruction was accomplished. All 10 prostheses supported by 28 implants placed into immediate function at the time of implant placement were successful during the 3-month healing period. Of these 28 implants placed into immediate function, 4 ultimately failed. Of the 35 submerged implants, all are osseointegrated and in function to date. Life-table analysis demonstrates an overall 10-year survival rate of 93.4% for all implants. The 10-year life-table analysis of survival is 84.7% for immediately loaded implants and 100% for submerged implants. Statistical analysis of the submerged versus immediately loaded implants demonstrates failure rates for immediately loaded implants to be significantly higher (P = .022 by the log rank test). These data demonstrate that although mandibular implants can be successfully placed into immediate function in the short term to support fixed provisional prostheses, long-term prognosis is guarded for those implants placed into immediate function distal to the incisor region.     

Prosthetic considerations in the fabrication of surgical stents for implant placement

The utilization of surgical stents/templates for implant placement is of significant importance to the success of the definitive prosthesis. However, major conceptual differences exist between surgical stents designed for implant-supported crowns and bridges and those designed for implant overdentures. In addition, various types of surgical stents exist within each group. In either case, optimizing the prosthetic result by customization of the stent should be a major consideration in the fabrication process. The design of the stent must account for several treatment conditions, including position of the implant, the tissue present, and the anticipated prosthesis. The teaching objective of this article is to present the prosthetic considerations in the fabrication and customization of surgical stents. The article compares the two groups and offers specific guidelines for the fabrication of surgical stents for the various types of restorations within each group.     

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.     

Implant placement without flaps: a single-stage surgical protocol--Part 1

Osseointegrated implants have been demonstrated to be predictable, efficacious means of restoring aesthetics and long-term function to edentulous patients. Although the surgical and placement protocols for the use of implant therapy have continued to evolve, specific criteria must be addressed when utilizing this modality. The objective of this article is to describe the requisites for proper implant placement and demonstrate the use of a novel surgical protocol to insert implant fixtures in selected edentulous sites with a mucosal tissue punch rather than a conventional flap elevation procedure.     

Lipid peroxidation in patients with ischemic heart disease, hyperlipidemia and/or hypertension while polyunsaturated omega-3 fatty acids of plant and animal origin were in their diet

Missing anterior teeth are being replaced by implant-supported restorations quite frequently in modern dentistry. Providing the patient with a temporary prosthesis prior to or following implant fixture placement must satisfy established esthetic and functional criteria. When orthodontic treatment is included as part of the overall treatment effort, additional considerations include the retention and stabilization of newly established tooth positions. This article describes the fabrication, use and advantages of a provisional anterior prosthesis that replaces missing teeth prior to or following implant placement.     

Biomechanical considerations when combining tooth-supported and implant-supported prostheses

The force distribution of multiple tooth-supported and implant-supported prostheses is completely different. A direct correlation exists between the degree of flexion at the site of loading and the amount of force distribution to other members of the prosthesis. Micromovement produced by the periodontal fibers facilitates force distribution to all the root surfaces of the natural tooth abutments. The rigidity of the implant/abutment/prosthesis configuration concentrates the force at the crestal bone at the site of loading with limited distribution to the remaining implants. Differential mobility concentrates the force distribution to the bone support of the most rigid members of splinted natural teeth or to the implants when they are united with natural teeth in a combined prosthesis. Implants always support the natural teeth and never the other way around. Therefore a nonrigid attachment is recommended between a tooth-supported prosthesis and an implant-supported prosthesis when they are combined. However, when implants are interspersed with natural teeth in the same prosthesis, the restoration will be implant borne. This requires special force distribution analysis to prevent implant overload.     

Hard-tissue augmentation for the placement of anterior dental implants

Dental implants have become a popular alternative for replacing missing teeth in every region of the oral cavity. In the anterior zone, special esthetic concerns require not only a stably anchored implant for long-term success, but also the presence of adequate hard and soft peri-implant tissues. Anterior tooth loss is often accompanied by considerable loss of alveolar bone, so augmenting hard tissue before or in combination with implant placement becomes a critical part of therapy. One of the most successful augmentation techniques is guided bone regeneration (GBR). Thus far, augmentation procedures using expanded polytetrafluoroethylene membranes (ePTFEa) have proved to be the most efficient and predictable surgical technique to enhance deficient bone sites. This article discusses some critical biological and clinical/technical aspects of GBR and describes techniques for anterior hard-tissue augmentation with the photographic documentations of three clinical cases.     

Long-term follow-up on hydroxylapatite-coated cylindrical dental implants: a comparison between developmental and recent periods

PURPOSE: To compare success rates for dental implants placed from 1985 through 1988 and from 1989 through 1991, and to investigate the factors associated with success or failure. PATIENTS AND METHODS: All hydroxylapatite-coated cylindrical implants placed from 1985 through 1991 were followed yearly. Lifetable survival analyses compared implant success for a "developmental period" from 1985 through 1988 (4 to 8 years follow-up) and a "recent period" from 1989 through 1991 (1 to 4 years follow-up). Reasons for success or failure, time from implant placement to removal related to failure reason, outcome after implant removal, and a morbidity analysis are included. RESULTS: The 7 to 8-year cumulative success rate for all implants placed in the developmental period (maxilla and mandible combined) was 86.5%; it was 84.2% for all maxillary implants and 87.5% for all mandibular implants. The cumulative success rate for all implants placed in the recent period was 97.5%; it was 97.5% for all maxillary implants and 97.6% for all mandibular implants. The difference between the two periods was statistically significant only for the anterior maxilla. Regression analysis on the interval success rates indicates that interval failure did not follow a linear relationship with time. The most common reasons associated with failure were lack of keratinized gingiva, poor oral hygiene, mechanical overload, and malposition. CONCLUSION: Comparison with previously reported cumulative success rates indicated learning curve experiences comparable with other implant systems. Improvements in hardware, surgical and prosthetic techniques, and patient selection have led to an improvement in success rates with the recent period implants.     

A qualitative and quantitative method for evaluating implant success: a 5-year retrospective analysis of the Br?nemark implant

A proposed protocol and differentiated success criteria for long-term evaluation of oral implants are presented. The protocol and criteria were applied to a retrospective patient material treated during a 1-year period and followed for 5 years. The protocol comprised a two-stage analysis of the collected clinical data. First, a quantitative analysis of the outcome was made using a life table. Based on the information obtained during the follow-up, each implant was categorized into one of three groups: unaccounted for, failure, or survival. A qualitative analysis of the survival group was then performed by active testing against defined criteria. Depending on the modes of clinical and radiographic examinations and their results, surviving implants were either further assigned to one of three success grades or remained in the survival group. The data are presented in a four-field table at one level of success. Strict success criteria together with individual stability testing and radiographic examination of each consecutive implant should be used when a new implant system is evaluated or when a new application is explored. Radiography alone and more moderate success criteria may be used to document routine treatments, provided that an already well-documented implant system is studied.     

Altered patterns of DNA methylation on chromosomes from leukemia cell lines: identification of 5-methylcytosines by indirect immunodetection

The feasibility of implant treatment in patients after oral ablative tumor surgery has not yet been investigated with consideration of the requisite high periodontal standards. A report on this topic has to deal not only with implant survival but also with implant health, bone response, soft tissue health, failure pattern, time of failure, and ease of restoration. For the assessment of an implant system, an overview must be accomplished that takes into account the different restorations used and their interaction with the implant system that was used. This study presents the Bone-Lock implant system (Howmedica Leibinger GmbH, Freiburg, Germany) in a retrospective investigation after 5 years of follow-up with special emphasis on the prosthetic restorations used following resection of oral malignancies. From early in 1990 through June 1996, we inserted 210 dental endosteal Bone-Lock implants (58 patients) after oral tumor resectioning. Included in the study were 45 patients with 162 implants and prosthetic restorations that had been loaded for 1 year (dentures retained by telescopic or bar-clip or ball attachments, implant-supported prostheses, tooth-to-implant connected bridges). Regular follow-up consisted of evaluation of the Plaque Index (Silness and L?e) and of the Sulcus Bleeding Index (L?e), measurements of pocket probing depth, implant mobility (by means of the Periotest method), bone resorption (according to X-ray findings), and a questionnaire that registered patient satisfaction. The results were evaluated for each restoration and were compared with baseline standards. The overall 5-year survival rate was 83.2%. For implants that had been in place for over 365 days, the survival rate was 93%. The investigation showed that after resection of oral malignancies, patients could be treated with dental implants and superstructures with long-term efficacy similar to that found in healthy subjects considering internationally accepted standards. Implant treatment in tumor patients appeared to offer the most positive periodontic results when use of bar-clip or telescope-retained overdentures was involved. The patient satisfaction level with the described prosthodontic treatment was satisfactory.     

The custom implant impression coping: technical note

Unsupported soft tissue can collapse around a submerged implant or abutment head during the time interval between removal of the provisional prosthesis and placement of the impression material. A technique is described for accurately recording the implant or abutment position as well as the position of the soft tissue for a single tooth restoration using the provisional prosthesis as a custom implant impression coping.