Distribution of bone quality in patients receiving endosseous dental implants

Bone microarchitecture at oral implant sites in ectodermal dysplasia (ED): a comparison between males and females

OBJECTIVE

The aim of this study was to analyse the microarchitecture of bone in association with implant placement in young ectodermal dysplasia (ED) patients. The general hypothesis was that the structural and morphological features of bone microarchitecture are different between males and females, which may influence clinical outcomes.

MATERIALS AND METHODS

The bone harvesting is not additionally invasive, as the procedure was made at the time and site of implant placement. Twenty one samples (8 female, 13 male) were harvested from nine ED participants whose age ranged between 14 and 21 years and specified by the site of harvesting. Micro-CT analysis at 5 µm resolution was conducted on each sample. Specialized CT analysis of the three-dimensional (3-D) bone microstructure was made to compare structural parameters. In addition, two bone samples (one male, one female) were sent to the University of Michigan and analysed at 9 µm resolution.

RESULTS

No significant difference was found between male and female samples. Bone analysis of particular sites revealed that bone-specific surface (BS/BV) was found to be significantly higher in male than in female samples, whilst the mean values of 10 parameters, the grey scale value histograms and 3-D visualization showed that female samples had higher compact density than male samples.

CONCLUSION

Microstructural analyses indicated that female ED bone was more compact and with greater trabecular connectedness than male bone. These features may enhance resistance to external force transfer of mastication compared with male bone. Further bone samples from other jaw bone areas will provide information on whether there are regional differences in jawbone quality and quantity, which may influence implant treatment outcomes, as well as follow-up analyses of treatment outcomes.

The effect of smoking on survival and bone loss of implants with a fluoride-modified surface: a 2-year retrospective analysis of 1106 implants placed in daily practice

AIM

To compare the survival and peri-implant bone loss of implants with a fluoride-modified surface in smokers and nonsmokers.

MATERIALS AND METHODS

Patient files of all patients referred for implant treatment from November 2004 to 2007 were scrutinized. All implants were placed by the same experienced surgeon (B. C.). The only inclusion criterion was a follow-up time of at least 2 years. Implant survival and bone loss were assessed by an external calibrated examiner (S. V.) comparing digital peri-apical radiographs taken during recall visits with the post-operative ones. Implant success was determined according to the international success criteria (Albrektsson et al. 1986). Survival of implants installed in smokers and nonsmokers was compared using the log-rank test. Both nonparametric tests and fixed model analysis were adopted to evaluate bone loss in smokers and nonsmokers.

RESULTS

One-thousand one-hundred and six implants in 300 patients (186 females; 114 males) with a mean follow-up of 31 months (SD 7.15; range 24-58) were included. Nineteen implants in 17 patients failed, resulting in an overall survival rate of 98.3% at the implant level and 94.6% at the patient level. After a follow-up period of 2 years, the cumulative survival rates was 96.7% and 99.1% with the patient and implant as the statistical unit, respectively. Implant survival was significantly higher for nonsmokers compared with smokers (implant level P=0.025; patient level P=0.017). The overall mean bone loss was 0.34 mm (n=1076; SD 0.65; range 0-7.1). Smokers lost significantly more bone compared with nonsmokers in the maxilla (0.74 mm; SD 1.07 vs. 0.33 mm; SD 0.65; P<0.001), but not in the mandible (0.25 mm; SD 0.65 vs. 0.22 mm; SD 0.5; P=0.298).

CONCLUSION

The present study is the first to compare peri-implant bone loss in smokers and nonsmokers from the time of implant insertion (baseline) to at least 2 years of follow-up. Implants with a fluoride-modified surface demonstrated a high survival rate and limited bone loss. However, smokers are at a higher risk of experiencing implant failure and more prone to show peri-implant bone loss in the maxilla. Whether this bone loss is predicting future biological complications remains to be evaluated.

A wide-body implant as an alternative for sinus lift or bone grafting

PURPOSE

The aim was to evaluate the outcome of a short wide-body implant in the atrophic posterior jaw without a grafting procedure.

MATERIALS AND METHODS

Patients treated with a tapered wide-body implant measuring 8 to 9 mm in width and 7 to 9 mm in length (Max implant; Southern Implants, Irene, South Africa) were recalled to scrutinize implant survival. Preoperative cone beam computed tomography images were analyzed to measure bone height in reference to the mandibular canal and sinus floor.

RESULTS

There were 57 implants inserted in 18 men and 24 women after a 2-stage procedure and delayed loading. The mean follow-up was 15 months (SD, 10; range, 1-32 months), with 63.2% of the implants having at least 1 year of follow-up and 26.3% having at least 2 years' follow-up. Forty-six implants were inserted in the posterior maxilla and eleven in the mandible. Fifteen were placed in an extraction socket and forty-two in healed bone. Thirteen implants were supporting a single crown. Two implants failed, resulting in a survival rate of 96.5%, with rates of 90.9% and 97.8% for mandible and maxilla, respectively. This was not affected by gender, jaw, immediate or delayed placement, implant diameter and length, or the use of a bone substitute. The mean preoperative bone height was 7.21 mm in maxilla and 8.76 mm in mandible. In 41 cases implant length surpassed available bone height.

CONCLUSIONS

Despite the compromised bone condition and height, the survival rate of 96.5% is comparable to normal implants and, therefore, placing a wide-body implant may be an alternative to avoid grafting procedures. This is probably related to the enlarged implant surface area and the good primary stability.

Ambiguity in bone tissue characteristics as presented in studies on dental implant planning and placement: a systematic review

OBJECTIVES

To survey definitions of bone tissue characteristics and methods of assessing them in studies of dental implant planning and placement.

MATERIAL AND METHODOLOGY

Three databases were searched using specified indexing terms. Three reviewers selected from the titles and retrieved abstracts in accordance with inclusion and exclusion criteria. Descriptions of bone tissue characteristics (bone quality, density and quantity) used before or during dental implant placement were searched for and categorized.

RESULTS

The search yielded 488 titles. One hundred and fort-nine publications were selected and read in full text. One hundred and eight were considered relevant. There were many different definitions and classification systems for bone tissue characteristics and examination protocols. Approximately two-third of the included publications reported the Lekholm & Zarb classification system for bone quality and quantity. However, only four studies implemented the Lekholm & Zarb system as originally proposed. A few publications described bone quality in accordance with the Misch or Trisi and Rao classifications systems. Assessment methods were often described only briefly (or not at all in one-fifth of the publications). Only one study presented the diagnostic accuracy of the assessment method, while only two presented observer performance.

CONCLUSION

The differing definitions and classification systems applied to dental implant planning and placement make it impossible to compare the results of various studies, particularly with respect to whether bone quality or quantity affect treatment outcomes. A consistent classification system for bone tissue characteristics is needed, as well as an appropriate description of bone tissue assessment methods, their diagnostic accuracy and observer performance.

Interferon alfa-2b for recurrent and metastatic giant cell tumor of the spine: report of two cases

STUDY DESIGN

Case report.

OBJECTIVE

To demonstrate that interferon alfa-2b is a therapeutic option for obtaining long-term control of recurrent and metastatic giant cell tumor of spine.

SUMMARY OF BACKGROUND DATA

Interferon alfa served as angiogenesis inhibitor and has been successfully used to treat giant cell tumor of long bones and facial bones. Up to date, no report is found with regard to the use of interferon as a stand-alone treatment for unresectable, recurrent, and metastatic giant cell tumor originated from the spine.

METHODS

A 29-year-old woman with C1 and C2 giant cell tumor was treated by radiotherapy, intralesional curet, and chemotherapy orderly. Tumor recurred after 2 years. A second curet was undertaken. Tumor recurred second time and caused severe spinal cord compression. Lung metastasis was diagnosed simultaneously. A 24-year-old man with recurrent giant cell tumor of T5 and T6 was treated by spondylectomy of T5 and T6. Six months later, a giant metastatic lesion was found in sacrococcygeal region, which was excised and proved to be giant cell tumor of bone. Four months later, 2 recurrent lesions were found beside the rectum. Interferon alfa-2b at a dose of 3,000,000 U/m was then administered subcutaneously everyday for both patients for 3.5 and 3 years, respectively.

RESULTS

No major complications related to the use of interferon occurred. The lesion in C1-C2 of the first patient regressed steadily and was restricted and encircled within the lateral mass. The metastatic lesions in the lungs also significantly reduced. The pararectal lesions of the second patient disappeared completely.

CONCLUSION

Interferon therapy may be an effective and safe treatment for spine giant cell tumor recurrence and metastasis in soft tissue. The effectiveness may be time and dosage dependent.

Management of combined ridge defect and osteotome sinus floor elevation with simultaneous implant placement--a 36-month follow-up case report

This report demonstrated the management of combined ridge defect and maxillary sinus pneumatization with simultaneous implant placement. One case with vertical and horizontal ridge deficiency and sinus pneumatization in the maxillary premolar area was indicated for ridge augmentation and sinus elevation before implant placement. Implant osteotomy was enlarged using a ridge expansion osteotome to 1 mm short of the sinus floor; sinus elevation was performed using sinus lift osteotomes; the implant was placed; bone graft and resorbable membrane were used to augment the remaining defect. The second stage was done after 6 months, followed by final restoration. The patient was reevaluated for 36 months following the final prosthesis. The surgical site healed without complication following implant placement. During the second stage, the implant was completely surrounded by bone, with bone covering the buccal aspect of the cover screw. The X-ray showed a 5 mm apical shift of the sinus floor at 6 months post surgery. At 12 months post loading, crestal bone loss to the level of the first thread was noted; no changes were observed at the sinus or surrounding teeth. Pocket depth ranged from 3-4 mm. No further bone loss or soft tissue contour change was noted at 18, 24, 30, and 36 months post loading. The combination of these three techniques with simultaneous implant placement as described in this report seems to be successful. Further research is needed to evaluate whether the combination of these techniques with simultaneous implant placement offers similar results when compared with the stage approach.

The effect of smoking on early bone remodeling on surface modified Southern Implants®

INTRODUCTION

Smoking affects the survival of turned titanium implants. Although smoking has less impact on the failure rate of rough surface implants, the effect on bone loss on rough surface implants has not been studied yet and may be an important factor in biological stability.

AIM

To determine the effect of smoking on early implant failures and bone remodeling around moderately rough implants (Southern Implants®, Southern Implants, Irene, South Africa).

MATERIALS AND METHODS

Three hundred twenty-nine patient records, containing information on 712 installed implants, were scrutinized retrospectively and periapical radiographs were analyzed for interproximal bone level. Mann-Whitney U-test and Fisher's exact test were performed to compare bone level and implant survival in smokers and nonsmokers. Only implants with at least 6 months of function time were analyzed for bone level changes.

RESULTS

The overall survival rate was 98.3%. Implants in smokers had a threefold higher failure rate compared with nonsmokers (5/104 = 4.8% vs 7/608 = 1.2%). This was statistically significant on implant level (p = .007) but not on patient level (1/41 vs 7/288, p = .997). Readable radiographs from 363 implants in 169 patients were available with a mean follow-up of 12 months (SD 5.11; range 6-28). The mean interproximal bone level was 1.36 mm (n = 363; SD 0.41; range 0.48-3.70). Bone levels were independent of jaw location. Sixty implants from 21 smokers lost statistically significantly (p = .001) more bone (mean 1.56; SD 0.53; range 0.75-3.22) than the 303 implants in 148 nonsmokers (mean 1.32 mm; SD 0.38; range 0.48-3.7). The maxilla is especially prone to bone loss compared with the mandible (1.70 mm vs 1.26 mm, p < .001).

CONCLUSION

The Southern Implants® system demonstrated a high absolute survival rate. Although smokers are not more prone to implant loss, more pronounced peri-implant bone loss was observed, especially in the maxilla. Whether this affects future biological complications remains to be investigated in prospective long-term studies.

Implant failure predictors in the posterior maxilla: a retrospective study of 273 consecutive implants

BACKGROUND

The goal of this study was to retrospectively analyze a cohort of 136 patients who underwent dental implant placement in the posterior maxilla at the University of Connecticut Health Center to assess and identify predictors for implant failure in the posterior maxilla.

METHODS

Data were retrieved from patient charts to identify subjects older than 21 years of age who received dental implant(s) in the posterior maxilla. Patients without a postoperative baseline radiograph were excluded. A recall radiograph was taken 3 to 6 months after implant placement. If there was no recall radiograph, the subject was contacted for a recall visit that included a clinical evaluation and radiographs to determine the implant status. Based on a univariate screening, variables considered potential implant failure predictors included gender, diabetes, smoking, implant length, implant diameter, membrane use, sinus-elevation technique, and surgical complications. These parameters were further assessed, and a multivariable logistic regression was performed with implant failure as a dependant variable. All tests of significance were evaluated at the 0.05 error level.

RESULTS

Two hundred seventy-three implants were placed in the posterior maxilla. Fourteen implants failed (early and late failures combined), resulting in a 94.9% overall survival rate. The survival rates for the sinus-elevation group and native bone group were 92.2% and 96.7%, respectively (P = 0.090). Based on the multivariable analysis, sinus floor-elevation procedures were not associated with increased risk for implant failure (P = 0.702). In contrast, smoking and surgical complications had a statistically significant effect on implant failure; the odds ratios for implant failure were 6.4 (P = 0.025) and 8.2 (P = 0.004), respectively.

CONCLUSION

Sinus-elevation procedures with simultaneous or staged implant placement do not increase the risk for implant failure, whereas smoking and surgical complications markedly increase the risk for implant failure.

Performance of threaded versus sintered porous-surfaced dental implants using open window or indirect osteotome-mediated sinus elevation: a retrospective report

BACKGROUND

The purpose of this retrospective report was to evaluate the performance of dental implants placed in a teaching environment in patients requiring maxillary sinus elevation.

METHODS

Threaded (acid-washed or sand-blasted acid-etched) and sintered porous-surfaced (SPS) press-fit implants were used. Sinuses were managed using direct (open window) or indirect (osteotome-mediated) techniques. Records were available for 97 implants in 62 patients. Preoperative subantral bone heights were determined from radiographs, primarily panoramic. Of 69 threaded implants used, 40 and 29 were placed using direct (DTH) and indirect (ITH) techniques, respectively. Twenty-eight SPS implants were placed using the indirect technique. Implant failure rates using the Kaplan-Meier method of analysis and cumulative crestal bone loss (the latter based on bone levels seen in the most recent radiographs) were determined for both types of implants.

RESULTS

The mean preoperative subantral bone height for DTH implants was 5.0 mm (range, 1 to 12 mm). Preoperative bone heights for ITH implants and SPS implants placed using the indirect approach were 7.2 mm (range, 4 to 12 mm) and 4.2 mm (range, 3 to 6 mm), respectively. Significant differences in preoperative bone height were seen between DTH and ITH implants (P <0.0001) and between ITH and SPS implants (P <0.0001). Average functional times were 18.7 months and 16.3 months for DTH and ITH implants, respectively, whereas the average functional time for SPS implants was 49.9 months. Time in function was significantly greater (P <0.0001) for SPS than DTH and ITH implants. Significant differences in implant length were also seen, with SPS implants significantly shorter than DTH or ITH implants. Three implants failed to integrate, one in each of the three treatment groups, giving initial survival rates of 97.5%, 96.6%, and 96.4% for DTH, ITH, and SPS implants, respectively. Mean cumulative crestal bone loss measurements were 1.84, 1.90, and 0.57 mm for DTH, ITH, and SPS implants, respectively. Bone loss was significantly less with SPS implants than with DTH or ITH implants. A second SPS implant failed after 7 years in function, likely because of prosthetic deficiencies. This late failure reduced the Kaplan-Meier survival rate to 80.4% for the SPS group.

CONCLUSION

Results from this teaching clinic suggest that the use of dental implants with sinus elevation procedures is a predictable treatment for the resorbed posterior maxilla.

Relations between the bone density values from computerized tomography, and implant stability parameters: a clinical study of 230 regular platform implants

AIMS

The objective of this study was to determine the relationship between bone density, insertion torque, and implant stability at implant placement.

MATERIALS AND METHODS

One-hundred and eight patients were treated with 230 Brånemark System implants. A computerized tomography (CT) machine was used for pre-operative evaluation of the jaw bone for each patient. The maximum insertion torque values were recorded with the OsseoCare equipment. Implant stability measurements were performed with the Osstell machine for only 142 implants.

RESULTS

The mean bone density and insertion torque values were 721+/-254 Hounsfield unit (HU) and 39.1+/-7 N cm for 230 implants, and the correlation was significant (r=0.664, p<0.001). The mean bone density, insertion torque, and resonance frequency analysis values were 751+/-257 HU, 39.4+/-7 Nc m, and 70.5+/-7 implant stability quotient (ISQ), respectively, for 142 implants. Statistically significant correlations were found between bone density and insertion torque values (p<0.001); bone density and ISQ values (p<0.001); and insertion torque and ISQ values (p<0.001).

CONCLUSION

The bone density values from pre-operative CT examination may provide an objective assessment of bone quality, and significant correlations between bone density and implant stability parameters may help clinicians to predict primary stability before implant insertion.

Randomized clinical trials in implant therapy: relationships among methodological, statistical, clinical, paratextual features and number of citations

OBJECTIVES

The aim of the present study was to investigate the relationships among reported methodological, statistical, clinical and paratextual variables of randomized clinical trials (RCTs) in implant therapy, and their influence on subsequent research.

MATERIALS AND METHODS

The material consisted of the RCTs in implant therapy published through the end of the year 2000. Methodological, statistical, clinical and paratextual features of the articles were assessed and recorded. The perceived clinical relevance was subjectively evaluated by an experienced clinician on anonymous abstracts. The impact on research was measured by the number of citations found in the Science Citation Index. A new statistical technique (Structural learning of Bayesian Networks) was used to assess the relationships among the considered variables.

RESULTS

Descriptive statistics revealed that the reported methodology and statistics of RCTs in implant therapy were defective. Follow-up of the studies was generally short. The perceived clinical relevance appeared to be associated with the objectives of the studies and with the number of published images in the original articles. The impact on research was related to the nationality of the involved institutions and to the number of published images.

CONCLUSIONS

RCTs in implant therapy (until 2000) show important methodological and statistical flaws and may not be appropriate for guiding clinicians in their practice. The methodological and statistical quality of the studies did not appear to affect their impact on practice and research. Bayesian Networks suggest new and unexpected relationships among the methodological, statistical, clinical and paratextual features of RCTs.

Bone density assessments of oral implant sites using computerized tomography

The type and architecture of bone are considered to affect its load-bearing capacity and it has been indicated that poorer quality bone is associated with higher implant failure rates. To date, bone classifications have only provided subjective methods for pre-operative assessment, which can be considered unreliable. The aim of this study was to evaluate variations of the bone density in designated endosseous implant sites using computerized tomography. One hundred and thirty-one designated implant sites in 72 patients were utilized. Computerized tomography results indicated that bone densities may vary markedly when different areas of a designated implant site are compared. It has been observed that a difference in the bone density exists for the four regions within the oral area, with the anterior mandible yielding mean density values of 944.9+/-207 Hounsfield units (HU)>anterior maxilla, 715.8+/-190 HU>posterior mandible, 674.3+/-227 HU>posterior maxilla and 455.1+/-122 HU. Computerized tomography may be a useful tool for determining the bone density of interest areas before implant placement, and this valuable information about the bone quality provides dental practitioners to make better treatment planning regarding the implant positions.

Bone Augmentation Techniques

BACKGROUND

The advent of osseointegration and advances in biomaterials and techniques have contributed to increased application of dental implants in the restoration of partial and completely edentulous patients. Often, in these patients, soft and hard tissue defects result from a variety of causes, such as infection, trauma, and tooth loss. These create an anatomically less favorable foundation for ideal implant placement. For prosthetic-driven dental implant therapy, reconstruction of the alveolar bone through a variety of regenerative surgical procedures has become predictable; it may be necessary prior to implant placement or simultaneously at the time of implant surgery to provide a restoration with a good long-term prognosis. Regenerative procedures are used for socket preservation, sinus augmentation, and horizontal and vertical ridge augmentation.

METHODS

A broad overview of the published findings in the English literature related to various bone augmentation techniques is outlined. A comprehensive computer-based search was performed using various databases that include Medline and PubMed. A total of 267 papers were considered, with non-peer-reviewed articles eliminated as much as possible.

RESULTS

The techniques for reconstruction of bony defects that are reviewed in this paper include the use of particulate bone grafts and bone graft substitutes, barrier membranes for guided bone regeneration, autogenous and allogenic block grafts, and the application of distraction osteogenesis.

CONCLUSIONS

Many different techniques exist for effective bone augmentation. The approach is largely dependent on the extent of the defect and specific procedures to be performed for the implant reconstruction. It is most appropriate to use an evidenced-based approach when a treatment plan is being developed for bone augmentation cases.

Assessment of correlation between computerized tomography values of the bone, and maximum torque and resonance frequency values at dental implant placement

The aim of this study was to determine the bone density in the designated implant sites using computerized tomography (CT), the fastening torque values of dental implants, and the implant stability values using resonance frequency analysis. Further aim was to evaluate a possible correlation between bone density, fastening torque and implant stability. Eighty-five patients were treated with 158 Brånemark System implants. CT machine was used for preoperative evaluation of the jawbone for each patient, and bone densities were recorded in Hounsfield units (HU). The fastening torque values of all implants were recorded with the OsseoCare equipment. Implant stability measurements were performed with the Osstell machine. The average bone density and fastening torque values were 751.4 +/- 256 HU and 39.7 +/- 7 Ncm for 158 implants. The average primary implant stability was 73.2 +/- 6 ISQ for seventy implants. Strong correlations were observed between the bone density, fastening torque and implant stability values of Brånemark System TiUnite MKIII implants at implant placement (P < 0.001). These results strengthen the hypothesis that it may be possible to predict and quantify initial implant stability and bone quality from pre-surgical CT diagnosis.

Bone quality at the implant site after reconstruction of a local defect of the maxillary anterior ridge with chin bone or deproteinised cancellous bovine bone

The purpose of this study was to investigate the quality of bone at grafted implant sites in the anterior maxilla. Grafting of these sites was necessary because of insufficient bone volume in a buccopalatinal direction (width at the top of the crest 1-3mm). Reconstruction was performed with chin bone (N=5), chin bone and a resorbable Bio-Gide GBR membrane (N=5) or Bio-Oss spongiosa granules in combination with a Bio-Gide GBR membrane (N=5). Biopsies were taken prior to implantation, i.e. 3 months after grafting with chin bone, and 6 months after grafting with Bio-Oss. Evaluation was done by assessing the histological and histomorphometric characteristics of full-length biopsies taken from the actual implant site. Both areas with non-vital bone and areas with apposition of bone and remodelling phenomena were observed in the chin bone group at the time of placement of the implants. Similar results were observed at implant sites reconstructed with a chin bone graft covered by a membrane. In the chin bone group without and with a GBR membrane, the mean total bone volume (TBV) was 55.2+/-6.8% and 57.7+/-11.5%, respectively; the marrow connective tissue volume (MCTV) was 44.8+/-6.8% and 42.3+/-11.5%, respectively. Remnants of the resorbable GBR membrane were not detected. In the Bio-Oss((R)) group, at implant placement some newly formed bone was observed in the connective tissue surrounding the Bio-Oss((R)) particles (mean TBV (newly formed bone) 17.6+/-14.5%), but most particles were surrounded by connective tissue. No convincing signs of remodelling were observed (mean remaining Bio-Oss volume 40.5+/-9.3%; mean MCTV 41.9+/-13.1%). No implants were lost during follow up (12 months). At the time of placement of the implants the grafting material (either chin bone or Bio-Oss is still not fully replaced by new vital bone. In case of Bio-Oss, most of the grafting material is even still present. Despite these differences, the 1-year clinical results were very good and comparable between the various grafting techniques applied.

Humanex vivobone tissue strains around immediately loaded implants supporting maxillary overdentures

PURPOSE

To evaluate ex vivo bone tissue strains around maxillary implants supporting immediately loaded bar-retained overdentures.

MATERIAL AND METHODS

Ninety degree two-element rosette strain gauges were bonded on the labial bone of four ITI dental implants placed in the maxillary anterior region of four completely edentulous maxilla of fresh human cadavers. The installation torque value (ITV) of each implant was measured by a custom-made torque wrench and resonance frequency analyses (RFAs) were undertaken. A bar-retained overdenture was fabricated for each cadaver, and two miniature load cells were integrated in the first molar region of the overdentures for controlled loading experiments. Strain measurements were performed at a sample rate of 10 kHz and under a maximum load of 100 N, simultaneously monitored from a computer connected to a data acquisition system. Finally, removal torque values (RTVs) of the implants were measured.

RESULTS

RFA values did not mirror ITVs, while RTVs of implants were slightly lower than the ITVs. Any correlation could not be obtained between RFA values and ITVs or RTVs. Maximum strains around loaded implants ranged between -100 and -550 microepsilon under 25-100 N. The axial and lateral strain values of posterior implants of both sides were higher than those of anterior implants under all loads (P<0.05).

CONCLUSION

Because occlusal forces in humans tend to decrease because of age-related factors, maximum strains around immediately loaded implants supporting maxillary overdentures fall within physiologic levels.

Sinus Floor Elevation Using Osteotomes: A Systematic Review and Meta-Analysis

BACKGROUND

Various techniques of sinus floor elevation (SFE) are described. The elevation with osteotomes (OSFE) from a crestal approach is a relatively new technique. The aim of this systematic review and meta-analysis was to evaluate the clinical outcome of implants placed into the maxillary sinus augmented with an OSFE technique.

METHODS

A systematic online and manual review of the literature identified articles dealing with OSFE. Applying rigid inclusion criteria, screening and data abstraction were performed independently by two reviewers. The follow-up of loaded implants was a minimum of 6 months. The identified articles were analyzed regarding implant outcome and defined surgical aspects. Survival and success rates were estimated by Kaplan-Meier curves.

RESULTS

Eight out of 44 articles dealing with osteotome sinus floor elevation met the inclusion criteria. Five of the studies met established success criteria. The survival and success rates were 95.7% and 96.0% after 24 months and 36 months, respectively. The median and mean follow-up periods were 24 and 18.73 months for the survival rate and 24 and 19.7 months for the success rate. Regarding different surgical elements, i.e., osteotome techniques, implant types, and augmentation materials, the database was multivariate. Thus, no statistical analysis could be performed on these parameters.

CONCLUSIONS

Short-term clinical success/survival (<or years) of implants placed with an osteotome sinus floor elevation technique seems to be similar to that of implants conventionally placed in the partially edentulous maxilla. Controlled prospective clinical studies are needed to evaluate the long-term outcome and various surgical modifications of OSFE.

Overview of the SwissPlus Implant System

Although many improvements have been made to implant dentistry during the last quarter of a century, clinical challenges still remain. For the surgeon, achieving implant stability in low-density bone can be difficult. For the restorative dentist, incompatibility between implant systems and the increasing complexity of esthetic restorative options frequently require special training in the selection and use of prosthetic components. This article presents an overview of a 1-stage implant system with a textured surface and osteocompressive surgical protocol designed to achieve stability in soft bone. Self-tapping, double lead threads and a separate surgical protocol also enable the implant to be placed in high-density bone. The implant is packaged on a fixture mount that also functions as a transfer and transitional or definitive abutment for cemented restorations. This implant is designed to help simplify restorative procedures by eliminating many ancillary restorative components. For multiple-unit, screw-retained restorations, the prosthesis can be splinted directly to the top of the implant without an intermediate abutment. Overdenture attachments and straight, angled, screw-receiving, and custom-cast abutments complete the restorative system.

Prosthetically driven Implant Placement. How to achieve the appropriate implant site development

Dental implants are established alternatives for replacing missing teeth. Tooth loss for different reasons may leads to alveolar resorption. Shortage of bone can prevent proper positioning of dental implants according to prosthetic needs and treatment planning, unless the volume of hard and soft tissues is increased before implantation. In the esthetic area it is essential not only to achieve well-anchored implants but also sufficient soft and hard tissue in order to obtain natural looking result. This article will present several treatment modalities to augment the soft and hard tissues in order to obtain proper insertion of implants according to prosthetic needs and patient satisfaction.

Dentoalveolar reconstructive procedures as a risk factor for implant failure

PURPOSE

Dentoalveolar reconstructive procedures (DRPs) are commonly used to enhance deficient implant recipient sites. It is unclear, however, if these procedures are independent risk factors for implant failure. The specific aim of this study was to assess the use of DRPs as a risk factor for implant failure.

MATERIALS AND METHODS

To address the research aim, we used a retrospective cohort study design and a study sample derived from the population of patients who had one or more implants inserted between May 1992 and July 2000. The main predictor variable was the use of DRPs, such as external or internal sinus lifts, onlay bone grafting, or guided-tissue regeneration with autogenous bone grafts or autogenous bone graft substitutes, to enhance the recipient sites before implant insertion. The major outcome variable was implant failure. Appropriate descriptive, bivariate, and multivariate statistics were computed.

RESULTS

The study sample was composed of 677 patients who had 677 implants randomly selected (1 implant per patient) for analysis. The overall 1- and 5-year implant survival rates were 95.2% and 90.2%, respectively. Bivariate analyses revealed 4 factors statistically or nearly statistically associated with implant failure: current tobacco use, implant length, implant staging, and type of prosthesis (P <.15). In the multivariate model, patients with DRPs did not have a statistically significant increased risk for implant failure (odds ratio = 1.4, P =.3).

CONCLUSIONS

The results of this study suggest that the use of DRPs to reconstruct deficient implant recipient sites was not an independent risk factor for implant failure in either the unadjusted or adjusted analyses.

AICRG, Part I: A 6-Year Multicentered, Multidisciplinary Clinical Study of a New and Innovative Implant Design

PROBLEM

Repetitive microstrains, which occur at the bone-implant interface during function, can lead to implant loss. In an attempt to improve survival by directing the stresses during function away from the dense cortical bone and toward the resilient trabecular bone, the Ankylos implant was developed with a roughened, progressive thread and a smooth cervical collar. The highly polished collar reduces the stresses in areas of the crestal bone. A precisely machined Morse taper prevents rotation of the abutment on the implant and eliminates the microgap present in many 2-stage implant systems. Clinical studies of other implants at different clinical research centers have demonstrated varying degrees of survival.

PURPOSE

The purpose of this paper was (1) to assess the overall clinical survival of this new implant design and (2) to compare implant stability (ie, Periotest values [PTVs]) over time with other implants.

METHOD

The investigation represented a comprehensive, multicentered, international clinical study conducted over a period of 6 years. It was conducted under an Investigational Device Exemption (IDE) protocol that was reviewed and accepted in the United States by the Food and Drug Administration (FDA). Over 1500 implants were placed and restored, and follow-up data were gathered for a period of up to 3 to 5 years.

RESULTS

Over 44% of the clinical research centers reported no failures (100% survival). A total of 63% of the centers had none or only 1 failure during the study. One center reported 6 failures in 1 patient, which were not related to the implant design. Overall survival for implants in function for 3 to 5 years was 97.5%. Using failure criteria of earlier studies of other implants, 5-year survival was 98.3%. Higher handpiece speeds were associated with an increase in the number of failures. This new design produced a slightly more resilient trabecular bone-implant complex with a difference of about 1 PTV in all bone densities when compared with other implants.

CONCLUSIONS

The following conclusions can be made: (1) the implant design was effective under all clinical conditions; (2) no significant and unexpected complications or risk factors were evident; (3) survival was found to be excellent; and (4) this implant is well suited for use in the restoration of masticatory function and esthetics in patients with missing natural teeth.

Maxillary Sinus Elevation Surgery: An Overview

Maxillary sinus elevation surgery was developed to increase the height of bone available for implant placement in the posterior maxilla. The efficacy and predictability of this procedure have been determined in numerous studies. The basic approach to the sinus (Caldwell-Luc operation) involves an osteotomy performed on the lateral maxillary wall, elevation of the sinus membrane, and placement of bone graft material. The graft materials can be categorized into four groups: autogenous bone, allografts (harvested from human cadavers), alloplasts (synthetic materials), and xenografts (grafts from a nonhuman species). These graft materials can be used alone or in combination with each other. Implant placement can occur at the same surgical procedure (immediate placement) or following a healing period of 6 to 9 months (delayed placement). A more conservative approach to the sinus, the osteotome technique, has been described as well.

CLINICAL SIGNIFICANCE

This article provides an overview of the surgical technique, with emphasis on anatomic considerations, preoperative patient evaluation (clinical and radiographic), indications and contraindications to the procedure, and possible risks and complications.

Augmentation of the narrow traumatized anterior alveolar ridge to facilitate dental implant placement

Traumatic tooth loss leads to alveolar resorption especially in sagittal direction. This can be due to avulsion of bone substance during the accident itself or due to resorption of the alveolar crest that takes place afterwards. Shortage of bone can prevent proper positioning of dental implants unless the volume of bone is increased before implantation. In the maxillary anterior area, this is also an esthetic problem. Several treatment modalities have been presented to augment the bone. This report reviews the latest literature on bone grafting, bone substitutes, guided bone regeneration, osteocompression and distraction which are potentially useful in the anterior maxilla. A special emphasis is paid to the versatility of using a crestal split osteotomy, by means of chisels and osteotomes to widen the narrow ridge. Three examples are illustrated showing onlay grafting, preservation of alveolar width with alloplastic coral material and lateral widening of a narrow maxillary alveolar ridge, using the crestal splitting technique.

Histomorphometric and fluorescence microscopic analysis of bone remodelling after installation of implants using an osteotome technique

The influence of the osteotome technique on the osseointegration of rough-surfaced stepped cylinder implants (Frialit)-2) was compared to conventional preparation of the implant site in an animal model. A total of 104 implants were placed into the distal femoral condyle of 52 New Zealand white rabbits. This region contains sufficient trabecular bone for implant placement. The implant site was prepared either by the osteotome technique or by conventional technique with drills as a control group. During the healing period polychromatic fluorescence labelling was performed with four different fluorescent dyes. After 2, 4 and 8 weeks, the implants were removed with the surrounding bone. The sample preparation was done using the 'sawing and grinding' technique. Ground sections 100 microm thick were used for fluorescence microscopic analysis; 30- microm-thick ground sections were examined histomorphometrically. After 2 weeks the bone-to-implant contact ratio was 55.0 +/- 7.1% for the osteotome technique and 29.2 +/- 4.8% for the control group (P < 0.0005). After 4 weeks, the bone-to-implant contact ratio was still significantly better for the osteotome technique (bone-to-implant contact ratio osteotome technique 71.1 +/- 7.2%, bone-to-implant contact ratio control 59.0 +/- 6.3%, P = 0.003). Eight weeks after implant placement the bone-to-implant contact ratio was still better for the osteotome technique compared to the conventional implant placement. However it was no longer statistically significant. The qualitative fluorescence microscopic examination showed an earlier and stronger signal for the osteotome technique than the control group. With the latter, the zone of mineralization moved slowly towards the implant surface. Implant sites prepared by the osteotome technique showed a pronounced signal in the whole compressed area already by the second day. In conclusion, the osteotome technique increases new bone formation and leads to an enhanced osseointegration of dental implants in trabecular bone. However, more experimental trials have to be carried out on higher mammals that show a metabolic rate of bone that is more comparable to humans.

SwissPlus Implant System, Part 1: Surgical aspects and intersystem comparisons

Implant survival in poor-quality bone continues to pose a significant clinical challenge to dentists. The SwissPlus System comprises one-piece, straight and tapered implant designs with self-tapping, apical threads, and a microtextured surface on the intraosseous portion of the implant bodies. Although both designs are indicated for all ranges of bone density, Tapered SwissPlus features double-lead threads and a soft-bone surgical protocol designed to enhance initial mechanical stability at the time of placement. This paper presents an overview of the SwissPlus System with emphasis on the surgical aspects. Presented test data also illustrate intersystem compatibility and differences between the straight SwissPlus and ITI synOcta implants.

Clinical application of spiral tomography in anterior implant placement: case report

BACKGROUND

Placement of endosseous dental implants in edentulous areas of the anterior maxilla poses a unique challenge due to variations in the amount of residual alveolar bone. Implant position becomes crucial in cases demanding high esthetic results but possessing minimal ridge width or in cases requiring augmentation. Recent advances in spiral tomography have allowed for more precise planning and placement of endosseous implants in these challenging areas.

METHODS

The purpose of this report is to describe a series of clinical cases in which spiral tomography was utilized in the planning and placement of endosseous dental implants. Two cases will be described utilizing initial spiral tomographic radiographs for implant planning and surgical guide fabrication, followed by post-insertion tomography to evaluate the results of implant position and inclination.

RESULTS

Preimplant spiral tomograms revealed that the initial prosthetic trajectory through the proposed incisal edge of each tooth replacement would result in a final osteotomy site that would compromise the overall thickness of the facial cortical plate. After adjusting for magnification and distortion factors, new prosthetic/surgical trajectories were fabricated into the surgical guide, and this information was utilized to prepare the final implant osteotomy site. This adjustment resulted in 2 mm of residual crestal facial bone postimplant insertion, which became wider at more apical measurements. These findings were verified in the postimplant serial tomograms.

CONCLUSIONS

Spiral tomography was a valuable adjunct in the treatment planning phases of endosseous dental implant placement especially in cases with minimal crestal width, high esthetic demands, or where exact implant placement is critical for successful treatment outcomes.

The influence of functional forces on the biomechanics of implant-supported prostheses--a review

OBJECTIVES

To evaluate published evidence related to the influence of functional forces on the biomechanics of implant-supported prostheses.

DATA AND SOURCES

The literature was searched for original research articles relating control of loads on dental implants, effects of early and late occlusal loads, the influence of bone quality, prosthesis type, prosthesis material, number of supporting implants, and engineering techniques employed for evaluating mechanical and biomechanical behavior of implants using MEDLINE and manual tracing of references cited in key papers otherwise not elicited.

STUDY SELECTION

Current literature on implant biomechanics as main focus and pertinent to key aspects of the review.

CONCLUSIONS

The outcome of implant treatment is often maximized when implants are placed in dense bone, number of supporting implants are increased, implant placement configuration reduces the effects of bending moments, and when a fixed prosthesis is delivered to the patient.

Risk factors for dental implant failure: a strategy for the analysis of clustered failure-time observations

This study's objective was to identify, in a statistically valid and efficient manner, the risk factors associated with dental implant failure. We hypothesize that factors exist which can be modified by clinicians to enhance outcome. A retrospective cohort study design was used. Cohort members had >or= one implant placed. Risk factors were classified as demographic, health status, implant-, anatomic-, or prosthetic-specific, and reconstructive variables. The outcome variable was implant failure. The cohort was composed of 677 patients who had 2349 implants placed. Based on the adjusted multivariate model, factors associated with implant failure were tobacco use, implant length, staging, well size, and immediate implants (p <or= 0.05). In the setting of correlated survival observations, we recommend adjusting for the correlation of the observations to provide statistically valid and efficient results. Three of the identified factors--tobacco use, immediate implants, and implant staging--potentially may be modified to enhance implant survival.

Optimal implant stabilization in low density bone

Initial stability of the implant is one of the fundamental criteria for obtaining osseointegration. An adequate primary anchorage is often difficult to achieve in low density bone (type IV). Various surgical suggestions were advanced in the 1980s which were aimed at achieving optimal osseous integration in poor quality bone. They offered satisfactory short-term results. Recently, as a result of surgical and technological innovations, new therapeutic proposals have shown very interesting results in their initial studies.