The International Journal of Oral & Maxillofacial Implants, 04/2001

Generally, endosseous implants can be placed according to a nonsubmerged or a submerged technique and in 1-piece or 2-piece configurations. Recently, it has been shown that peri-implant crestal bone reactions differ significantly radiographically as well as histometrically under such conditions and are dependent on a rough/smooth implant border in 1-piece implants and on the location of a microgap (interface) between the implant and the abutment/restoration in 2-piece configurations. The purpose of this study was to evaluate whether standardized radiography as a noninvasive clinical diagnostic method correlates with peri-implant crestal bone levels as determined by histometric analysis. Fifty-nine implants were placed in edentulous mandibular areas of 5 foxhounds in a side-by-side comparison in both submerged and nonsubmerged techniques. Three months after implant placement, abutment connection was performed in the submerged implant sites. At 6 months, all animals were sacrificed, and evaluations of the first bone-to-implant contact (fBIC), determined on standardized periapical radiographs, were compared to similar analyses made from nondecalcified histology. It was shown that both techniques provide the same information (Pearson correlation coefficient = 0.993; P .001). The precision of the radiographs was within 0.1 mm of the histometry in 73.4% of the evaluations, while the level of agreement fell to between 0.1 and 0.2 mm in 15.9% of the cases. These data demonstrate in an experimental study that standardized periapical radiography can evaluate crestal bone levels around implants clinically accurately (within 0.2 mm) in a high percentage (89%) of cases. These findings are significant because crestal bone levels can be determined using a noninvasive technique, and block sectioning or sacrifice of the animal subject is not required. In addition, longitudinal evaluations can be made accurately such that bone changes over various time periods can be assessed. Such analyses may prove beneficial when trying to distinguish physiologic changes from pathologic changes or when trying to determine causes and effects of bone changes around dental implants. Keywords: animal study, crestal bone loss, endosseous implants, histometry, standardized radiography

While the Periotest continues to be used in assessing the integrity of implants, there are numerous reports of its inconsistencies. To understand more precisely what the Periotest is actually measuring, a mathematical model was developed that illustrates the effect that various geometric and clinical parameters have on the Periotest value (PTV). In addition, the model was validated with an in vitro experiment. Results of the mathematical model are shown to correlate with those obtained from the experimental test. The PTV is very sensitive to the position at which the Periotest impacts the abutment and to angulation of the handpiece. It was shown that a change in position of 1 mm in striking height can produce a difference in PTV of between 1 and 2. Since the angulation of the handpiece can produce a difference in striking position of 2 mm, it must be controlled as well. The model also showed that the Periotest can detect changes in bone height of 0.5 mm. Keywords: biomechanics, dental implantation, dental implants, Periotest

Titanium-aluminum-vanadium (Ti-6Al-4V) implants were placed in the tibiae of 32 rats (male Sprague-Dawley, 350 g) to examine healing and bone response. Half of the implants were treated with fibroblast growth factor 1 (FGF-1) delivered in an activated fibrinogen matrix. Animals were injected with a radiopharmaceutical imaging agent, technetium-99m-methylene diphosphonate (Tc-99m-MDP), which concentrates in bone, especially in areas of higher osteoblastic activity. Binding of Tc-99m-MDP to the implant was detected in vivo by Anger gamma camera imaging. Fourteen days after implant surgery, specimens were recovered and prepared for histomorphometric analysis. Histologic examination revealed that samples treated with FGF-1 demonstrated significantly greater amounts of bone-to-implant contact (P .05) compared to controls. Also, FGF-1-treated samples showed significantly greater amounts of bone (percent volume) adjacent to implants (P .005). These findings were supported by analyses of the non-invasive Tc-99m-MDP images, which demonstrated significantly greater uptake of Tc-99m-MDP adjacent to FGF-1-treated implants (P .05). Results of the experiments supported the hypothesis that FGF-1 could increase bone production around implants in a rat model. Keywords: dental implants, fibroblast growth factor, osseointegration, radioimmunodetection

The present study investigated 124 stepped-screw implants (gritblasted and acid-etched surface) placed in 104 patients immediately after tooth extraction or implant explantation and followed between August 1990 and December 1996. Implants of varying diameters and lengths were used to cover a wide range of indications in both the maxilla and mandible; 68% of the implants supported single-tooth replacements. The study parameters included Plaque Index, Gingival Index, probing depth, Periotest values, and peri-implant bone loss. Statistical analysis according to Kaplan-Meier revealed a 97% survival rate. Keywords: alveolar bone loss, bone level, dental implants, endosseous dental implantation, implant-supported prosthesis, surface properties

Spontaneous early exposure of submerged implants during the osseointegration healing phase may be a harmful factor that results in early crestal bone loss around the implants. The objective of this study was to assess the effect of spontaneous early exposure on crestal bone loss around submerged implants, with special attention given to the relationship between the degree of exposure and the amount of peri-implant bone loss. Crestal bone level relative to the shoulder of the implant was measured at the time of placement and at the time of exposure 4 to 5 months later. During the period between stage I and stage II surgery, implant sites were observed, and each implant site in which spontaneous early exposure was detected was recorded. Perforations were classified according to the degree of implant exposure from Class 0 (no perforation) to Class IV (complete exposure). Measurements from 206 implants in 64 patients produced 85 groups valid for statistical comparison; each of these contained at least 2 lesions of different types. There was a statistically significant difference between bone loss associated with intact mucosa (Class 0) and Class I, Class II, and Class III lesions, and between Class I and II lesions. There were no significant differences between Class I and III and between Class II and III. In Class II and III lesions, there was more bone loss associated with the buccal aspect of the implants. Of the 115 perforated sites, 10 were associated with bone loss exceeding 2 mm, 2 presented 3 to 4 mm bone loss, 1 showed more than 4 mm, and 1 displayed more than 5 mm. In view of the clinical implications that spontaneous early exposure may have on the success of osseointegration, prematurely partially exposed implants should be exposed as soon as possible after the perforation is observed. Keywords: bone loss, dental implants, early implant exposure, gingival perforation

The aim of this study was to determine the influence of age on peri-implant tissues in patients treated with implant-supported overdentures in the mandible. A prospective study was carried out with 2 groups of healthy edentulous patients. The mean age of the younger group (n = 32) was 46 years (range 35 to 50 years); the mean age of the older group (n = 26) was 68 years (range 60 to 80 years). Two dental implants were placed in the interforaminal region of the mandible, and after a 3-month healing period, overdentures were fabricated. Clinical and radiographic parameters were evaluated immediately after completion of the prosthetic treatment, after 1 year, and after 3 years. The evaluated clinical parameters were implant loss, Plaque Index, Gingival Index, Bleeding Index, and probing depth. Radiographic evaluation was performed using a standardized long-cone technique with a direction device. Statistical analysis was carried out with SPSS software. One implant in the older group was lost during the healing period. After 3 years, the mean scores for Plaque Index, Gingival Index, and Bleeding Index were between 0 and 1 for both groups (out of possible scores of 0 to 3), and the mean probing depth was 3 mm in both groups. The mean bone loss after 3 years was 1.2 mm in the younger group and 0.8 mm in the older group, but this difference was not significant. It was concluded from this study population that the clinical performance of implant-supported overdentures in the mandible is equally successful in younger and older patients. Keywords: aging, dental implants, geriatric dentistry

This is the first report of a group of 50 partially edentulous patients who received a total of 151 Endopore dental implants in the maxilla. A mean implant length of 8.7 mm was used, and 76.8% of implants were placed in the posterior maxilla. At re-entry, all implants appeared to be osseointegrated and were used to support fixed prostheses. Approximately half of the crowns (57%) in these prostheses were splinted to one another, while the remainder (43%) were not. At the time of this report, the mean functional time was 34.6 months and the cumulative survival rate was 97.3% (4 implants had failed). Analysis of carefully standardized sequential radiographs indicated no significant changes in mean crestal bone levels between baseline and any of the examination times (after 6 months, 1 year, and 2 years in function). There were no detectable correlations between crestal bone loss and the factors implant length (7, 9, or 12 mm); implant diameter (3.5, 4.1, or 5.0 mm); implant position anteriorly or posteriorly in the maxilla; or whether or not the implant-supported crowns were splinted. Keywords: implant-supported prostheses, partially edentulous maxilla, porous-surfaced dental implant

This study was designed to compare the results of immediate and delayed loading of implants with implant-retained mandibular overdentures. Ten patients (test group) received 40 Brånemark System MKII implants (4 per patient) placed in the interforaminal area of the mandible. Standard abutments were immediately screwed to the implants, rigidly connected with a bar, and immediately loaded with an overdenture. Ten patients (control group) received the same type and number of implants in the same area, but the implants were left to heal submerged. Four to 8 months later, standard abutments were screwed to the implants and the same prosthetic procedure was applied. Each implant was evaluated at the time of prosthetic loading and at 6, 12, and 24 months after the initial prosthetic load with the following parameters: modified Plaque Index (MPI), modified Bleeding Index (MBI), probing depth (PD), and Periotest. Peri-implant bone resorption was evaluated on panoramic radiographs taken 12 and 24 months after initial prosthetic loading. No significant differences were found between the 2 groups regarding MPI, MBI, Periotest, peri-implant bone resorption, and PD at 6 and 24 months (P > .05). The only difference was found regarding PD values on the mesial and lingual sites at 12 months (P .05). The cumulative success rate of implants was 97.5% in both groups. Results from this study showed that immediate loading of endosseous implants rigidly connected with a U-shaped bar does not seem to have any detrimental effect on osseointegration. Conversely, this method significantly shortens the duration of treatment with relevant satisfaction for the patients. Keywords: endosseous dental implants, immediate loading, implant overdenture

The purpose of this research project was to compare the fit of a retrievable cement-retained implant-supported framework to that of a traditional wax and cast, screw-retained framework and to test the strength of the cemented restoration. Ten telescopic frameworks were luted to gold cylinders with a bis-GMA resin cement. The control group consisted of 10 frameworks fabricated with traditional wax and casting techniques directly to the gold cylinders. Frameworks were analyzed for distortion in the z-axis using scanning electron microscopy and a single screw test. Results demonstrated that the retrievable cement-retained group had a decreased gap distance and improved angular distortion (statistical significance P .01) compared to the control group. Retentive strength measurements for the cement-retained group with a direct pull-out test revealed a mean pull-out force of 65.7 kg. Three of the 5 samples surpassed the tensile strength of the gold retaining screws (76 kg). Cement-retained restorations demonstrated superior fit in the z-axis and angular distortion compared to traditional wax and cast screw-retained frameworks. Retentive tests support a simplified technique of clinically luting telescopic implant-supported frameworks with adequate retentive strength. Keywords: dental cement, dental implants, dental materials, fixed partial denture, implant-supported dental prosthesis, prosthesis fitting

Between 1994 and 1999, 515 Astra standard implants were placed and documented prospectively in 107 patients. Of these implants, 364 were placed in original jawbone, 38 in areas augmented with local osteoplasty, and 113 in bone grafts from the iliac crest. The main indications for implantation were an atrophic edentulous alveolar crest (n = 361) and a shortened dental arch (n = 113). Single-tooth implants were excluded. In a special clinical examination, 56 patients with 258 implants were investigated. The average in situ time of the implants was 34.2 months. Failing osseointegration (n = 10), peri-implantitis (n = 10), and implant fracture (n = 1) in 15 patients resulted in the failure of 21 implants (4.1%). Three patients with 8 implants died from malignant tumor. Currently, 27 implants have been lost to follow-up, and 488 implants remain in situ (95.9%). Under analyses with different implant success criteria, the success rate decreased to 85%. Based on the results in this patient population, this implant was found to be a useful alternative to established implant systems for the indications analyzed. Keywords: dental implant, implant failure, marginal bone resorption, osseointegration, peri-implantitis

The aim of this investigation was to evaluate the osteoinductive property of autogenous demineralized dentin matrix (ADDM) on experimental surgical bone defects in the parietal bone of rabbits using the guided bone regeneration (GBR) technique incorporating human amniotic membrane (HAM). Thirty-six rabbits were divided into 2 groups, HAM and ADDM+HAM. It was possible to conclude that HAM did not interfere with bone repair and was resorbed. Slices of ADDM induced direct bone formation and were incorporated by the newly formed bone tissue and remodeled. The bone defects healed faster in the ADDM+HAM group than in the group with HAM only. Keywords: autogenous demineralized dentin matrix, biologic dressings, bone repair, guided tissue regeneration, human amniotic membrane

Most clinical patient reports apply the biologic principles of guided bone regeneration, in addition to defect filling with autogenous bone grafts or bone graft substitutes, in peri-implantitis therapy. Not infrequently, sites with membrane coverage have revealed early exposure, with subsequent infections, premature membrane removal, and insufficient bone regeneration. The present patient report demonstrates another surgical approach that uses the clinical principles and soft tissue management of vertical ridge augmentation, strictly following the same surgical protocol, on previously cleaned implant surfaces. The successful outcome of this surgical approach in one patient supports the feasibility of the selected treatment method in maintaining both the implants and the prosthetic reconstruction involved with peri-implantitis. Keywords: alveolar ridge augmentation, endosseous dental implant, guided tissue regeneration, peri-implantitis

Use of electrosurgery or laser surgery in the presence of metallic implants has been implicated in generating heat-induced injury to peri-implant bone, with the subsequent loss of osseointegration. Studies involving lasers offer conflicting results, while in the case of the electrosurg, little research has been published supporting or refuting these claims. This study measured local heat effects created by use of a unipolar electrosurgical unit, a bipolar electrosurgical unit, and a neodymium:yttrium-aluminum-garnet (Nd:YAG) laser. Absolute temperature increase was measured during an in vitro uncovering surgical procedure performed with each unit. Analysis of variance for repeated measures was performed. Second, absolute temperature increase for each unit was compared with a theoretical clinical limit of a 10°C increase. The findings suggest that use of the unipolar electrosurgical unit should be avoided, while judicious use of both the bipolar unit or the laser unit should produce temperature profiles well within clinical limits. Keywords: dental implants, electrosurgery, heat, laser surgery

Despite significant advances in dental therapeutics, there are patients for whom no reasonable treatment is available that will reliably restore or maintain their existing dentition. The causes of future edentulism include advanced caries, failing root canal therapy, inadequate numbers of teeth to support a fixed prosthesis, untreatable periodontal disease, or a history of failed previous rehabilitations. For these patients, dental implants may provide a more predictable future than retention of their remaining teeth. It is proposed that transitional fixed prostheses designed specifically for a patient with terminal dentition offer the advantage of maintenance and development of proper gingival esthetics with improved function. Prior to implant placement, the gingival frame is established, enhancing the overall appearance of the final, full-arch implant rehabilitation. The specific prosthodontic and surgical techniques required for successful treatment of these patients are presented. Keywords: dental implantation, dental implants, gingival morphology, implant-supported dental prosthesis, ovate pontic, transitional prostheses