Loss Of Osseointegration Research Articles

Passive Fit in Screw Retained Multi-unit Implant Prosthesis Understanding and Achieving: A Review of the Literature

One of the considerable challenges for screw-retained multi-unit implant prosthesis is achieving a passive fit of the prosthesis' superstructure to the implants. This passive fit is supposed to be one of the most vital requirements for the maintenance of the osseointegration. On the other hand, the misfit of the implant supported superstructure may lead to unfavourable complications, which can be mechanical or biological in nature. The manifestations of these complications may range from fracture of various components in the implant system, pain, marginal bone loss, and even loss of osseointegration. Thus, minimizing the misfit and optimizing the passive fit should be a prerequisite for implant survival and success. The purpose of this article is to present and summarize some aspects of the passive fit achieving and improving methods. The literature review was performed through Science Direct, Pubmed, and Google database. They were searched in English using the following combinations of keywords: passive fit, implant misfit and framework misfit. Articles were selected on the basis of whether they had sufficient information related to framework misfit's related factors, passive fit and its achievement techniques, marginal bone changes relation with the misfit, implant impression techniques and splinting concept. The related references were selected in order to emphasize the importance of the passive fit achievement and the misfit minimizing. Despite the fact that the literature presents considerable information regarding the framework's misfit, there was not consistency in literature on a specified number or even a range to be the acceptable level of misfit. On the other hand, a review of the literature revealed that the complete passive fit still remains a tricky goal to be achieved by the prosthodontist.

Radiographic Analysis of a Transalveolar Sinus‐Lift Technique: A Multipractice Retrospective Study With a Mean Follow‐Up of 5 Years

Various sinus-lift techniques have been described in the literature. The aim of this retrospective study is to evaluate the efficacy of a transalveolar sinus-lift technique in terms of implant survival, marginal bone loss, and complications. A total of 538 patient records were examined, and after applying exclusion and inclusion criteria, a sample of patients was included with a mean follow-up of 5 years. Implants with a smooth or tapered surface were considered. Therefore, only sinus lifts with inorganic bovine bone matrix or demineralized bone matrix were included, and 1,536 periapical radiographs were analyzed. Outcome measures were implant success, implant failure (peri-implantitis and loss of osseointegration), marginal bone resorption, and biologic complications (membrane perforations, sinusitis, and intraoperative and/or postoperative hemorrhage). Periapical radiographs were evaluated before surgery, post-surgery, and after 6 months and 1, 3, and 5 years. We analyzed the residual crestal bone height under the sinus, the amount (mm) of height increase after surgery, and values of implant marginal bone resorption for considered follow-ups. Two hundred eighty-two (282) patients were excluded. Therefore, 256 patients treated with the transalveolar sinus-lift technique were included. A total of 376 dental implants and 323 sinus lifts were analyzed. The overall rates of implant success and failure were 94.9% and 5.1%, respectively. The mean bone loss around implants was 1.98 mm (mean follow-up of 5 years). Patients treated with inorganic bovine bone matrix showed a better implant success rate (P = 0.03) than did patients treated with demineralized human matrix. Three Schneiderian membrane perforations occurred in the 323 sinus lifts. In these cases, the surgeon performed another surgical operation after 3 months. Postoperative complications were peri-implantitis (six cases) and osseointegration losses (13 cases). The transalveolar sinus-lift technique was a safe, minimally invasive technique with an implant success rate comparable to traditional implantology. The implant success rate was positively affected by the low-resorption graft material, and a low bone-resorption rate around implants was found.

Accidental Migration of a Dental Implant into the Ethmoid Sinus following a Transalveolar Sinus Elevation Procedure

Migration of a dental implant into the paranasal sinuses may be the result of sinus membrane perforation, loss of osseointegration, and lack of initial stability. The majority of displaced implants migrate into the maxillary sinus, which may cause sinusitis. The purpose of this study is to report an extremely rare ethmoid sinus migration of a dental implant after crestal approach in a resorbed posterior maxilla. A 60-year old Korean male with a noncontributory medical history was referred from a local clinic to remove the migrated dental implant in the right ethmoid sinus. The patient had symptoms of mild sinusitis. The implant had been placed 6 months earlier through the bone-added transalveolar approach in a severely resorbed maxilla. The displaced implant was removed through the intraoral approach. A lateral window was made and an endoscopic surgery was performed to remove the implant. Healing was uneventful, and sinusitis symptom had ceased. The crestal approach for severely resorbed posterior maxillae should be performed when there is a potential for primary stability. If bone quality is poor and initial stability cannot be achieved, lateral window sinus elevation procedure is a better option for successful implant placement. Migrated implant may be removed with antrostomy and endoscopic surgery.

OP012: Outcome of dental implants in maxillectomy patients

Head and neck cancer patients’ quality of life is improved (1) by the surgical reconstruction of resection defects and (2) by the dental rehabilitation with an implant-supported prosthesis. Understanding the implant behavior in these compromised situations may improve treatment planning. Therefore, the survival rates of dental implants inserted in maxillectomy patients were estimated. In addition, treatment modalities such as the type of radiotherapy, the type of surgical reconstruction and the type of prosthetic rehabilitation were tried to identify as risk factors for implant failure. After tumor staging and unilateral or bilateral maxillectomy, followed by adjunctive chemo/radiotherapy, the dental rehabilitation was performed by the same prosthodontist (St.S.). Afterwards, patients were regularly followed up in an oncological and dental recall system. Implant failure (uncensored) was defined as explantation, loss of osseointegration or failed use for prosthetic reconstruction. Implant survival was estimated by applying Kaplan–Meier analysis. Cox models were used to evaluate any association between implant failure and medical treatment modality. 156 dental implants in 39 cancer patients were placed in 40 resected maxillae. Overall, 14 out of 156 implants in 8 patients were lost. The 1-year implant survival rate was 92.7% (±2.1% Std.Err) and the 4-year implant survival rate was 90.3% (±2.5% Std.Err), respectively. Sixteen resected maxillae were surgically reconstructed followed by insertion of 60 implants, resulting in 9 implant failures. 23 resected maxillary defects remained open and received 96 implants for oral rehabilitation, ending up with 5 implant losses. Unsplinted implants showed a non-statistically significant higher risk for failures (Logrank, P -value < 0.05). If considering the clinical challenge by the oral rehabilitation of maxillectomy patients, the 4-year implant survival rate was surprisingly high. A larger sample size and a longer observation time are needed to identify risk factors for implant failures.

Reversible, non‐plaque‐induced loss of osseointegration of successfully loaded dental implants

Excess loading has been often cited as a reason for the failure of dental implants or bone loss post-osseointegration. The available data from animal studies have failed to show a clear role for excessive loading in the loss of osseointegration. The present case documentations aimed at providing a deeper insight into the medium- to long-term influence of occlusal loading on osseointegrated implants, and describe the clinical manifestations of such pathology. Two cases of loss of osseointegration are documented with single implants in the posterior maxilla. Implant mobility was in both cases the first and only sign of pathology, with the absence of plaque-induced inflammation and marginal bone loss. Re-osseointegration of the implants was achieved after the removal of the prosthetic reconstruction. The two cases reported that the loss of osseointegration in the absence of plaque-induced peri-implant inflammation is possible, although the clinical manifestations were very different to these of peri-implantitis. Once the occlusal loading was withdrawn, re-osseointegration was clinically confirmed in a period of 6-8months.

Complications of bone-anchored hearing aids in pediatric patients

Objective To describe the range and rate of complications related to bone-anchored hearing aids in pediatric patients. Method We conducted a retrospective review all children 16 years of age or less who were implanted with a bone-anchored hearing aid from 2002 to 2009. The main outcome measures were post Baha ® implantation complications including infection, soft tissue hypertrophy, loss of osseointegration, and need for further surgery. Results Thirty-one patients were identified and 27 had sufficient follow up for complete analysis. Soft tissue reactions were seen in 24 patients (89%), half of which were considered minor. Ten patients (37%) had major complications defined as requiring revision surgery or removal of the implant. Soft tissue overgrowth and infection at the abutment required removal in 5 children (19%) and three implants (11%) failed to osseointegrate. Recurrent antibiotic treatment was required in eight patients (30%). Seven patients (26%) had a history of trauma and one of them lost the implant. To date, three of the children (11%) have been unable to use the device because of chronic infection and overgrowth of the abutment. There was a statistically significant increased risk for major complications in patients from socioeconomically deprived backgrounds and obesity appears to incur additional risk. Conclusions Complications of bone-anchored hearing aid implants are common in our experience and obesity and socioeconomic factors appear to contribute to a higher risk for complications. Frequent follow up and meticulous care of the implant site may minimize complications but can be challenging in this population.

Scanning Electron Microscope Evaluation of Vertical and Horizontal Discrepancy in Cast Copings for Single-Tooth Implant-Supported Prostheses

Despite careful attention to waxing, investing, and casting, marginal discrepancies are inevitable. Vertical and horizontal discrepancies can result in crestal bone resorption, peri-implantitis, and loss of osseointegration. The aim of this study was to evaluate marginal gap and overhang in 3 casting techniques for implant framework fabrication. A total of 24 frameworks, 8 each with the Burn-out Cap (ITI; Straumann) (group BC), with Impression Cap (ITI; Straumann) (group IC), and with conventional wax-up technique (group WX) were fabricated. All specimens were waxed on the analog abutments and cast with Type IV gold alloy. All castings were fixed on the analog abutments with cyanoacrylate and embedded in acrylic resin. Specimens were sectioned and prepared for scanning electron microscope evaluation. Frameworks were analyzed for vertical and horizontal discrepancies with x200 magnification (scanning electron microscopy). Data were analyzed statistically by multivariate analysis and the post hoc tests (alpha = 0.05). The vertical discrepancy measurements for the 3 groups showed mean values of 53.74 +/- 11.0 mum, 63.6 +/- 13.2 mum, and 50.1 +/- 17.3 mum, respectively. The interfacial gap differences were not statistically significant in all groups (P > 0.05). Waxing the frameworks with impression caps significantly increased the horizontal discrepancy at the interfaces (P < 0.001). Within the limitations of this experiment, it was demonstrated that the vertical discrepancy of the frameworks made with the 3 techniques were comparable in lack of accuracy with each other. Although conventional waxing produced the least horizontal discrepancy, the difference with burn-out cap group was not statistically different.

Long-term complications of bone-anchored hearing aids: a 14-year experience

To report cases of long-term surgical complications, implant failure and revision surgery, within a large bone-anchored hearing aid programme. Retrospective, case-cohort study. Tertiary referral centre. One hundred and sixty-five adults and children who had undergone a total of 177 bone-anchored hearing aid implantations. Diagnosis and explanation of adverse events and device failure. Operative complications and survival analysis, surgical challenges related to revisions, and causes of failure. Twenty-one per cent of patients (3.4 per cent of those observed) suffered from skin reactions; this rate did not increase over time. Seventeen per cent had loss of osseointegration at a median interval of 6.3 months. Loss of osseointegration was observed more frequently in patients with a 3 mm compared with a 4 mm fixture (p < 0.001). Intra-operatively, the only complication was bleeding, occurring in 3 per cent of patients. Post-operative complications included: primary bleeding (2 per cent); severe skin reactions requiring intravenous antibiotics, cautery or grafting (8 per cent); thickening or overgrowth of skin requiring excision (8 per cent); failure of osseointegration requiring a new fixture (18 per cent); and graft necrosis requiring revision (1 per cent). In two patients, it was necessary to explore the area to remove overgrowth of bone. In 16 patients (10 per cent), the bone-anchored hearing aid had to be abandoned due to failure of osseointegration (n = 4), dissatisfaction with the aid (n = 6), intolerable pain (n = 4), hair growth around the abutment (n = 1) or recurrent infections (n = 1). In 12 of these patients, the bone-anchored hearing aid was removed surgically. Overall, 57 patients (34 per cent) underwent revision surgery. Awareness of complications is becoming increasingly important in bone-anchored hearing aid programme. A substantial workload of device maintenance should be anticipated, and patients should be appropriately counselled beforehand. Ninety per cent of our patients chose to persevere with this form of hearing rehabilitation.

Simulation of Impact Test for Determining “Health” of Percutaneous Bone Anchored Implants

There is an ongoing requirement for a clinically relevant, noninvasive technique to monitor the integrity of percutaneous implants used for dental restorations, bone-anchored hearing aids, and to retain extra-oral prostheses (ear, eye, nose, etc). Because of the limitations of conventional diagnostic techniques (CT, MRI), mechanical techniques that measure the dynamic response of the implant-abutment system are being developed. This paper documents a finite element analysis that simulates a transient response to mechanical impact testing using contact elements. The detailed model allows for a specific interface between the implant and bone and characterizes potential clinical situations including loss of bone margin height, loss of osseointegration, and development of a soft connective tissue layer at the bone-implant interface. The results also show that the expected difference in interface stiffness between soft connective tissue and osseointegrated bone will cause easily measurable changes in the response of the implant/abutment system. With respect to the loss of bone margin height, changes in the order of 0.2 mm should be detectable, suggesting that this technique is at least as sensitive as radiography. A partial loss of osseointegration, while not being as readily evident as a bone margin loss, would still be detectable for losses as small as 0.5 mm.

Osseointegration of Dental Implants in Patients with and without Radiotherapy

Between 1987 and 1997, 275 dental implants were inserted in the mandibles of 63 patients with squamous cell carcinoma of the lower oropharyngeal level following a radical surgical procedure. Thirty-five of these patients had been preirradiated with a complete dose of 60 Gy. In a retrospective analysis we have reviewed the data of these patients for age, sex, localization of the implants, irradiation, interval of implantation and interval of the abutment operation. Thus far, the median follow-up time is 65 months. The 5-year success rate for all implants was 97.9%. We found that radiotherapy, age, sex, localization of implantation or the interval between the end of the tumor therapy and the time of implantation did not have any significant influence on osseointegration or loss of osseointegration. Only the time interval between implantation and the abutment operation was recorded to be of any great significance (p=0.0001). No augmentation in the osteoradionecrosis rate could be recorded after dental implantation (1.6%), which leads us to conclude that radiotherapy (60 Gy) in patients with head and neck cancers should not be regarded as a contraindication for dental implantation.

Loss of osseointegration caused by occlusal load of oral implants. A clinical and radiographic study in monkeys.

The breakdown of bone around oral implants following excessive occlusal load or plaque accumulation was evaluated in monkeys. 5 screw type implants of pure titanium (Astra) were inserted in the mandible of 4 monkeys (Macaca Fascicularis). 2 implants were placed in each of the lateral segments and 1 in the frontal area. Each monkey was provided with 2 cemented splints covering the premolars and molars in the right and left side of the maxilla, respectively. 6 months after insertion of the fixtures, a fixed partial prosthesis was mounted on the 2 implants in one of the lateral segments. The prosthesis was in supra-occlusal contact with the antagonizing splint. Each prosthesis was replaced during the course of the experiment. The renewed prosthesis caused a lateral displacement of the mandible during occlusion, and therefore resulted in a lateral rather than axial excessive occlusal load. Implants retaining the prosthesis were brushed 1 x a week and subgingival cleaning was performed 1 x a month. The remaining implants were never cleaned and, additionally, a cotton cord was placed passively around each of these to promote plaque accumulation. 5 out of 8 implants with excessive occlusal load lost osseointegration (mobility and peri-implant radiolucency). The loss of osseointegration was observed 4.5 months to 15.5 months after the occlusal overload was commenced. None of the implants with plaque accumulation lost osseointegration, although an average loss of 1.8 mm in the radiographic bone level was assessed after 18 months.

Retrospective multicenter analysis of 3i endosseous dental implants placed over a five-year period

Osseointegrated dental implants have now become an accepted form of treatment for patients with a fully or partially missing dentition. The purpose of this study was to evaluate the performance of 3i threaded and cylindrical implants. During a 5-year period, a total of 1969 3i endosseous implants were placed at 6 centers in the United States and 2 elsewhere in the edentulous and partially edentulous jaws of 653 consecutive patients ranging in age from 18 to 82 years. Of the total number of implants placed, 1341 were commercially pure titanium threaded implants and 628 were titanium plasma-sprayed implants with a cylindrical configuration. A total of 28 patients with 110 implants were lost to follow-up. Implants in these patients were considered neither a success nor a failure. Success was predicated on the osseointegration of each and every implant followed in this analysis rather than the persistence of prosthetic function. Confirmed bone anchorage was considered essential for success. A total of 625 patients with 1871 implants remain in the study with a follow-up period ranging from 6 to 60 months. A total of 93 implants (5.0% of the total implants followed) were considered as failures. A mean implant survival rate was 95.0% for both the threaded and the cylindrical implant was calculated. The success rate of threaded implants was 97.0% in the mandible and 93.8% in the maxilla. The success rate for the 3.3-mm cylindrical implants was 96.0% in the mandible and 95.5% in the maxilla, and the success rate of 4.0-mm-diameter cylindrical implants was 95% in the mandible and 92.0% in the maxilla. Causes of failure consisted of loss of osseointegration (2.3%), crestal bone loss requiring periodontal therapy after the first year of function (1.7%) had mechanical problems associated with the prosthesis (0.9%). This retrospective analysis of the 3i endosseous implant system is comparable to previous reports on other implant systems in terms of implant survival and prosthesis stability. It is demonstrated that 3i implants are predictable and can provide lasting osseointegration leading to improvement of oral function if the recommended surgical and restorative protocol is followed.

An investigation on heat transfer to the implant-bone interface due to abutment preparation with high-speed cutting instruments

Excessive heat generation at the implant-bone interface may cause irreversible bone damage and loss of osseointegration. The effect of heat generation in vitro at the implant surface caused by abutment reduction with medium- and extra-fine-grain diamond and tungsten burs in a high-speed dental turbine was examined. Titanium-alloy abutments connected to a titanium-alloy cylindrical implant embedded in an acrylic-resin mandible in a 37 degrees C water bath were reduced horizontally and vertically. Temperature changes were recorded via embedded thermocouples at the cervix and apex of the implant surface. Analysis of variance for repeated measures was used to compare seven treatment groups. Thirty seconds of continuous cutting with standard turbine coolant caused a mean temperature increase of 1 degrees C with a maximum of 2 degrees C. Similar tungsten cutting caused a mean increase of 2 degrees C with a maximum of 4.7 degrees C, significantly higher than diamond reduction. Additional air-water spray for continuous tungsten cutting had no significant effect, while intermittent cutting for 15-second increments reduced the temperature increase by 75%. Thus, abutment reduction with medium-grit diamonds using intermittent pressure and normal turbine coolant is unlikely to cause an interface-temperature increase sufficient to cause irreversible bone damage and compromise osseointegration.

The transmandibular implant

During the period from August 1976 until July 1989 the transmandibular implant was introduced in a total of 31 oral and maxillofacial surgery departments in the Netherlands and 1,466 patients were treated. This study includes 1,356 treated patients from 28 departments. The treatment course of 1,201 patients (89.6%) was uneventful. Of the 157 complications, 58 related to the anatomic contour of the mandible, 49 to the surgery, 25 to the prosthetic reconstruction, 8 to the psychosocial attitude of the patient, 8 to the use of medication, 5 to trauma, and 4 to the presence of a skin graft. Treatment of the complications included removal of the implant in 44 patients; in 106 patients the complication was treated satisfactorily. In the remaining 7 patients, hypesthesia was present. The reasons for the removal of the 44 implants were infection (11), operative error (5), premature loading of the implant (3), insufficient width of the mandible after a visor osteotomy (1), loss of osseointegration caused by the prosthesis (14), psychological problems (4), trauma (3), drug-related gingival hyperplasia (2), and inexplicable pain (1). The present survey shows a consistent success rate of 96.8%.

The transmandibular implant: A 13-year survey of its use

During the period from August 1976 until July 1989 the transmandibular implant was introduced in a total of 31 oral and maxillofacial surgery departments in the Netherlands and 1,466 patients were treated. This study includes 1,356 treated patients from 28 departments. The treatment course of 1,201 patients (89.6%) was uneventful. Of the 157 complications, 58 related to the anatomic contour of the mandible, 49 to the surgery, 25 to the prosthetic reconstruction, 8 to the psychosocial attitude of the patient, 8 to the use of medication, 5 to trauma, and 4 to the presence of a skin graft. Treatment of the complications included removal of the implant in 44 patients; in 106 patients the complication was treated satisfactorily. In the remaining 7 patients, hypesthesia was present. The reasons for the removal of the 44 implants were infection (11), operative error (5), premature loading of the implant (3), insufficient width of the mandible after a visor osteotomy (1), loss of osseointegration caused by the prosthesis (14), psychological problems (4), trauma (3), drug-related gingival hyperplasia (2), and inexplicable pain (1). The present survey shows a consistent success rate of 96.8%.