The International Journal of Oral & Maxillofacial Implants, 04/2002

Purpose: The purpose of this study was to examine the dimensions and relationships of the periimplant tissues surrounding osseointegrated 2-stage implants placed at different depths in bone. Materials and Methods: Twenty-four implants were placed in the mandibles of 4 mongrel dogs. A modification of the surgical protocol was introduced so that in group I, implants remained 1 mm above the bone crest; in group II, implants were placed level with the bone crest; and group III implants were countersunk to approximately 1 mm below the bone crest. After 3 months, abutment operations were carried out with the placement of 3-mm standard abutments. Following a healing period of 3 months the dogs were sacrificed. A total of 20 implants were available for histometric analysis. Non-decalcified sections were evaluated for the dimensions of the junctional epithelium, connective tissue band, marginal bone level, and bone-to-metal contact. Results: Histologic observations showed a mucosal barrier consisting of keratinized oral epithelium continuous with a thin junctional epithelium facing the implant and abutment surface. Junctional epithelium showed a mean of 1.67 mm for group I, 1.93 mm for group II, and 2.78 mm for group III. These values were not statistically different. The band of connective tissue had a mean of 1.13 mm for group I, 0.92 mm for group II, and 1.60 mm for group III. These values were not statistically different, except for group II versus group III. Bone level had a mean of 2.50 mm for group I, 2.30 mm for group II, and 1.60 mm for group III. These differences were significant between groups I and III. The surface of bone contact along the implant (BMC%) showed mean values of 46.8% in group I, 53.7% in group II, and 49.0% in group III (no significant differences among the 3 groups). Discussion: There was a clear tendency of the epithelium and connective tissue to be longer the deeper the implants were placed, although those differences were not statistically significant. Bone loss was smaller for group III (countersink group). This is not in accordance with recent articles which have stated that bone will maintain its biologic width. Conclusions: When the microgap between implants and abutments was placed deeper in the bone, additional bone loss did not result.

Purpose: This prospective clinical trial examined the effect on teeth and implants when rigidly or nonrigidly connected in a cross-arch model. Materials and Methods: Thirty patients received 2 implants, 1 on each side of the mandible, and were restored with 3-unit fixed partial dentures connected either rigidly or non-rigidly to an abutment tooth. Patients were followed for at least 5 years post-restoration. Results: Repeated-measures analysis revealed no significant difference in crestal bone loss at implants (rigid versus non-rigid methods). An overall significant difference (P .001) was found comparing methods for teeth. Paired t tests revealed no significant differences in crestal bone levels for implants or teeth at the 5-year recall. Kaplan-Meier methods and the Cox proportional hazards model showed no differences between attachment methods with regard to success based on survival and bone loss criteria. During the 5-year recall period, 1 implant (rigid side) was removed. Four implants developed bone loss greater than 2 mm during the course of this trial. One tooth on the rigid side and 2 teeth on the non-rigid side had greater than 2 mm of crestal bone loss and were removed secondary to fractures. In all, 5 abutment teeth were removed, all of which had been treated with root canal therapy and fractured at the interface of the post within the tooth. There was no clear relationship of tooth fracture to attachment. Repeated-measures analysis of mobility values revealed no significant changes over the time course of this study, and paired t tests revealed no statistically significant differences between implants for mobility. Repeated-measures analysis and paired t tests for probing depth revealed no significant changes over the time course of this study. There were no significant differences in soft tissue indices for either attachment method. The percentage of patients who had measurable intrusion was 66% for the non-rigid group, and 44% for the rigid group; 25% of the non-rigid teeth had greater than 0.5 mm intrusion, compared with 12.5% for the rigid group. For the 2 time periods evaluated, there was no significant increase in intrusion over time. The non-rigid-side implant required more nonscheduled visits to treat problems than the rigid implant and the teeth. Discussion: Most patients were treated successfully with rigid or non-rigid attachment of implants to teeth. Conclusion: The high incidence of intrusion and non-scheduled patient visits suggest that alternative treatments without connecting implants to teeth may be indicated.

Purpose: This work evaluated the osteoconductive properties of autogenous demineralized dentin matrix (ADDM) on surgical bone defects in the parietal bone of rabbits, using the guided bone regeneration technique and polytetrafluoroethylene (PTFE) membrane. Materials and Methods: Surgical bone defects were created in 24 adult rabbits and repaired with either ADDM and PTFE (experimental group) or PTFE alone (control group). The ADDM had been obtained from the central incisors of the experimental rabbits. The rabbits were sacrificed after 15, 30, 60, and 90 days and the defects examined radiographically and histologically. Results: Radiographically, the defects in the experimental animals achieved radiopacity more quickly than the defects in the control group. Discussion: After 15, 30, 60, and 90 days of observation following surgery, the ADDM slices appeared to stimulate new bone formation. The dentin slices were completely incorporated into the new bone tissue and were resorbed during the bone repair. Conclusions: Bone repair was accelerated on the bone defects treated with ADDM when compared to the control group.

Purpose: The aim of this study was to investigate the influence of particle size of autogenous bone grafts on the early stages of bone regeneration. Materials and Methods: Bicortical skull bone defects were prepared in 15 rabbits (4 in each rabbit). Two defects were filled at random with either small (0.5 to 2 mm3) or large (10 mm3) autogenous bone particles. In addition, 1 defect was left unfilled (control defect). All defects were covered bicortically by expanded polytetrafluoroethylene membranes. The animals were divided randomly into 3 groups and sacrificed after 1, 2, and 4 weeks, respectively. Histologic and stereologic evaluations were performed after the sections were blinded. Results: No significant differences in total vessel surface area could be identified among the 3 groups. The total volume of newly formed bone in defects with small particles was larger and more mature compared to defects with large particles after 2 and 4 weeks. Furthermore, the resorption of small particles was more pronounced after 4 weeks, documenting a higher level of bone substitution compared to large particles. Discussion: The early stages of bone regeneration were influenced by the particle site of autogenous bone grafts. Conclusion: The present study indicated that particles of 0.5 to 2 mm3 in size should be preferred to particles of 10 mm3 in size for bone grafting.

Purpose: The aim of this study was to histologically analyze the bone repair of maxillary areas reconstructed with autogenous bone grafts using 2 different donor sites, the ilium and the chin. Materials and Methods: Specimens were retrieved with trephine burs positioned transversely in augmented ridges 4 months after placement of the grafts. To analyze bone conditions, a histomorphometric study of ground sections was performed using a special template to identify 3 specific regions of the specimens: cortical bone, cancellous bone, and the region of transition between the alveolar ridge and the graft. Ten patients, 5 men and 5 women, with a mean age of 47 years (range 28 to 67) were evaluated. Results: Results indicated good incorporation of the grafts in this period, demonstrated by intense osteogenesis indicating an active remodeling process. Discussion: In both groups, the improvement in bone quality of the receptor site was evident, independent of the size of the reconstruction, although chin grafts presented better bone quality. Conclusions: From this study it was possible to conclude that a period of 4 months is sufficient for the placement of osseointegrated implants in reconstructed areas, where chin or iliac autogenous grafts have been used.

Purpose: This report of a clinical patient series indicates the relative safety and illustrates the procedures involved in the extraction of remaining teeth followed by immediate implant placement and loading with a simple acrylic resin fixed denture. Materials and Methods: Ten consecutive patients who selected tooth extraction and implant-supported fixed denture rehabilitation of the mandible were treated using a 1-visit approach for extraction, implant placement, and restoration. Healthy individuals (10 women) were treated under local anesthesia. Fifty-four implants were placed in 10 patients. Five or 6 Astra Tech implants (11 or 13 mm long) were placed into the edentulous parasymphyseal region of the mandible. Four to 6 implants (48 of 54) were immediately loaded by the fabrication of a simple acrylic resin fixed denture. The criterion for loading was clinical judgment of primary stability, ie, the absence of axial or lateral mobility with physical resistance to rotation. Patients were recalled at 1, 3, and 12 weeks. At 12 weeks, impressions were made for the fabrication of a screw-retained fixed denture. The fixed dentures were completed using conventional fabrication and prosthetic techniques. Results: After a period of 6 to 18 months, all 54 implants had survived and were considered 100% successful by independent testing of mobility and radiographic evidence of osseointegration. There were no surgical complications. Fracture and debonding of the acrylic resin provisional denture occurred for 1 patient during the first 12 weeks of treatment. Discussion: Advantages to extraction with simultaneous replacement include the maintenance of vertical dimension, elimination of reline procedures and interim denture therapy, and potential improvement of soft tissue healing. Conclusion: This therapeutic approach simplifies patient care without apparent additional risk.

Purpose: The aim of this study was to compare the retention and stability of the Nobel Biocare standard ball (NBS), Nobel Biocare 2.25-mm-diameter ball (NB2), Zest Anchor (ZA), Zest Anchor Advanced Generation (ZAAG), Sterngold ERA orange (SEO), and Sterngold ERA white (SEW) attachments on an implant-retained overdenture model. Materials and Methods: The attachments were tested using 2 permanently placed Brånemark System implants on a test model that was attached to an Instron machine (crosshead speed 50.8 mm/minute). Each attachment had one part embedded in a denturelike housing and the other part screwed into the implants. Dislodging tensile forces were applied to the housings in 3 directions simulating function: vertical, oblique, and anterior-posterior. Eight tests were done in 3 directions with 6 samples of each attachment. The dislodging forces generated measurements of the peak load (maximum dislodging force). A 1-way analysis of variance followed by the Tukey studentized range test was used to determine groups that were significantly different. All tests for significance were carried out at the .05 level of significance. Results: Results showed the ZAAG attachment to be the most retentive for the peak load measurement when subjected to vertically directed forces, with mean values and standard deviations of 37.2 ± 5.5 N. The next most retentive attachment was the NBS, followed by the SEO, NB2, SEW, and ZA. For obliquely directed forces, the ZAAG attachment was the most retentive, with mean values and standard deviations of 27.2 ± 4.2 N. The next most retentive was the NBS, followed by the NB2, SEO, ZA, and SEW. For anterior-posteriorly directed forces, results showed the NBS had the highest measured retentive force, with mean values and standard deviations of 34.6 ± 18.8 N, but this was not statistically different from the NB2 and ZAAG; this was followed by the SEO, SEW, and ZA. Discussion: There has been a marked resurgence in the treatment of patients with overdentures using implant attachments as retentive devices. The maximum force developed (a measure of retention) as the implant stud attachments were resisting removal from the implant abutments was determined. Conclusions: Based on the present study, the clinician may be able to make empirical decisions on attachment selection, depending on the amount of retention desired and the specific clinical situation.

Purpose: Provisional cements are commonly used to facilitate retrievability of cement-retained fixed implant restorations. While the functional life spans of these cements are unpredictable, the relative retentiveness of various permanent and provisional cements between dental alloys and titanium abutments is not well documented. The aim of this study was to compare the uniaxial resistance forces of permanent and provisional luting cements used for implant-supported crowns. Materials and Methods: Seven samples on 4 different abutments (a total of 28 crowns) were cast using a gold-platinumpalladium alloy. The crowns were cemented with 3 different provisional, polycarboxylate, and glassionomer cements and 1 zinc phosphate cement. After storage of samples in artificial saliva for 24 hours, tensile tests were performed. Results: While the highest uniaxial resistance forces were recorded for polycarboxylate cements, provisional cements exhibited significantly lower failure strengths (P .05). The uniaxial resistance force of cements on different abutments exhibited notably different trends; however, more force was required to remove crowns cemented to long abutments (P .05). Discussion: Glass-ionomer and zinc phosphate cements may be used to increase the maintenance of implant-supported crowns. Temporary cementation of such restorations may necessitate frequent recementation, particularly for restorations on short abutments. Conclusions: Temporary cementation may be more suitable for restorations supported by multiple implants.

Purpose: Didactic predoctoral dental implant education is part of the curriculum in most US dental schools. However, fewer than half offer laboratory instruction, and only a few allow dental students to place and restore dental implants. The additional time necessary for laboratory and clinical experience encroaches on an already crowded curriculum. Is the additional time necessary in the curriculum for laboratory and clinical experience by dental students reflected by the practice patterns of graduates who have completed such a program over the past 10 years? Materials and Methods: A survey was designed to determine the implant practice patterns of graduates of the Creighton School of Dentistry, Omaha, Nebraska, for the 10-year period 1988 to 1997. These graduates had all participated in a formal undergraduate didactic and laboratory curriculum in implant dentistry. Approximately half also had the opportunity to place and/or restore dental implants while students. The survey was also sent to graduates (also 1988 to 1997) from a midwestern dental school without a formal laboratory or clinical component (used as a control group). The data were analyzed statistically. Results: In comparison to the control group (56% versus 23%), more than twice as many Creighton graduates restore dental implants as a part of their general practice, surgically place more dental implants, refer more implant patients to surgical specialists, and seek more continuing education hours related to implant dentistry. These conclusions were all supported by statistical analysis of the data. Discussion: Student clinical experience with implant dentistry appears to significantly increase the incorporation of implant dentistry into future dental practices. Even if clinical experience was not an option, a school curriculum which included both didactic and laboratory participation still significantly increased the number of graduates who included implant dentistry in their practices. Conclusion: The inclusion of laboratory and clinical experience in implant dentistry in the CUSD undergraduate curriculum resulted in significantly greater participation in implant dentistry at the general practice level.

Purpose: This report involves the retrospective analysis of ITI implants placed and/or restored by a group of 7 clinicians located throughout the United States (5 periodontists and 2 prosthodontists). Materials and Methods: Six hundred seventy-five posterior single-tooth implants were restored in 471 patients (average time of loading 21.30 months, with a range of 1 to 78 months). Three hundred seventy implants and 71 implants were placed in mandibular and maxillary molar sites, respectively, and 108 and 126 were placed in mandibular and maxillary premolar sites, respectively. Results: A cumulative survival rate of 99.1% was obtained for all sites (6 failures). The survival rates for individual sites were as follows: 98.4% mandibular molars, 100% maxillary molars, 100% mandibular premolars, and 100% maxillary premolars. "At-risk" implants (1 to 2 mm of radiographic bone loss) were noted at 5 sites. Discussion: Minimal restorative problems were found with either screw-retained (n = 71) or cemented restorations on solid abutments (n = 600); 80.3% of screw-retained and 98.2% of cemented restorations were free of complications, respectively. Patient satisfaction scores were high (97.4%) as determined by the Patient Satisfaction Questionnaire. Conclusion: The data suggest that solid-screw (4.1 or 4.8 mm wide) ITI implants can be a satisfactory choice for posterior single-tooth restorations.

Purpose: It was the aim of the present prospective study to quantify the gain in height of implant sites by endoscopically controlled osteotome sinus floor elevations (ECOSFE) with simultaneous implant placement and to report the number of sinus membrane perforations. Materials and Methods: From October 1999 to December 2000, of 92 sinus floor elevations, 18 were carried out endoscopically controlled with an osteotome technique. As augmentation material, -tricalcium phosphate (-TCP) or autogenous bone was used; 22 implants were placed. Results: The residual height of the alveolar crest in the posterior maxilla was 6.8 ± 1.6 mm on average. The implant lengths ranged from 10 to 16 mm (mean implant length 12.2 ± 1.4 mm). They were significantly larger than the residual height of the alveolar crests (P .0005). Elevation of the sinus floor with an osteotome had to be supported by conventional sinus floor elevation instruments after a mean elevation of 3.0 ± 0.8 mm to prevent perforation of the sinus membrane. However, 1 perforation occurred, which was repaired with a periosteal patch. At stage 2 surgery, 2 implants were removed because of mobility. Endoscopic control revealed one case in which -TCP could be found within the sinus; another case showed areas of polypoid mucosa on the sinus floor. Discussion: With the ECOSFE, perforations of the sinus membrane can be visualized; however, they cannot be avoided. Although this technique is less invasive than the lateral window technique, it cannot be recommended as a standard procedure in the posterior maxilla because of the large amount of additional equipment needed and the technically demanding procedure. Conclusion: The use of the ECOSFE should be confined to scientific trials.

Purpose: This prospective study evaluated the immediate loading of single, threaded, root-form implants placed in the maxillary premolar area. Materials and Methods: Ten human subjects were included in this preliminary report. In all cases, a screw-retained temporary acrylic resin crown was placed immediately after implant surgery. The definitive screw-retained metal-ceramic crown was placed 6 months later. Results: Standardized radiographs demonstrated 0.58, 0.73, 0.84, and 0.90 mm mean marginal bone loss at 1, 3, 6, and 12 months after implant surgery, respectively. Implant mobility was evaluated with the Periotest device. At the day of surgery, mean mobility was -3.3, while minor changes were observed thereafter: mean values of -3.77, -3.47, and -3.63 were recorded at 3, 6, and 12 months after implant surgery, respectively. Sulcus depth appeared relatively stable after the 3rd month when the implant platform was used as a reference. Recession of 0.43 mm was recorded between the 3rd and 12th month; when the depth of the peri-implant sulcus was measured from the implant platform, 0.1 mm of change was seen between the 3rd and 12th month. Probing depth measurements revealed that 3 months after implant placement, average probing depth was 3.60 mm, while at 12 months it was 3.20 mm. Discussion: The peri-implant soft tissue parameters (bleeding on probing, probing depth, peri-implant soft tissue level), mobility, and marginal bone level appeared to be similar to findings of previous studies regarding the conventional 2-stage loading protocol. Conclusion: Results of the current study provided evidence that, under the condition of this investigation, single root-form implants can be immediately loaded when placed in the maxillary premolar area.

Purpose: To rehabilitate the mastication and speech of edentulous congenital cleft lip and palate patients with the use of endosseous implants in conjunction with bone augmentation. Materials and Methods: Between 1992 and 1999, 6 partially and 4 completely edentulous adult patients with complex cleft palate defects were treated. Six patients had large, unrepaired defects of the hard and soft palate, whereas the other 4 had residual oronasal fistulas after failed palatoplasty and bone grafting. In 8 patients, free inlay-antral and simultaneous lateral-onlay bone grafts (3 patients) were obtained from the iliac crest, and dental implants were placed secondarily. In the other 2 patients, the implants were placed without grafting in recent extraction sites. Rigid bars with extensions over the defects were used to support obturator prostheses (n = 7), or patients were provided with fixed implant-supported prostheses (n = 3). In all, 50 cylindric, screw-type dental implants were placed and followed up for 1 to 8 years (mean, 5 years). Results: Six implants were regarded as early failures and 1 was lost during the first year of loading; 1 patient lost all 5 implants. The cumulative success rate at 5 years was 85.7%. Discussion and Conclusion: All 9 successfully rehabilitated patients reported a remarkable functional and psychologic improvement after the treatment. The described treatment protocol also seemed to be effective for correcting velopharyngeal insufficiency in patients using an obturator prosthesis.

Purpose: The objective of this study was to evaluate the effect of radiofrequency- (RF) sputtered calcium phosphate (CaP) coating of titanium implants on bond strength at the bone-implant interface and percent bone contact length. Materials and Methods: Cylindric sputtered CaP-coated and plasmasprayed hydroxyapatite- (HA) coated implants (4.0 mm diameter and 8 mm length) were implanted in dog mandibles. Half the sputtered CaP-coated implants were heat-treated. Results: Twelve weeks after implant placement, no statistical differences in the mean ultimate interfacial strengths were observed between as-sputtered CaP-coated, sputtered CaP-coated heat-treated, and control plasma-sprayed HAcoated implants. Histomorphometric evaluation indicated that the percent bone contact lengths for the plasma-sprayed HA-coated implants and the as-sputtered CaP-coated implants were similar and significantly greater than that for the sputtered CaP-coated heat-treated implants. Differences in the ultimate interfacial strength and percent bone contact length between different implant sites in the mandible were not observed. Discussion: The results of this study, considered together with the results of previous studies, suggest that once early osseointegration is achieved, biodegradation of the thin CaP coatings is not detrimental to bone-coating-implant fixation, and does not compromise bone responses to the coated implant surfaces. Conclusion: The interfacial strength and histomorphometric data suggest that the CaP coatings applied using the sputtering process produce bone responses similar to those of HA coatings applied using plasma spraying.

This patient report concerns etiologic factors leading to a failed natural dentition, masticatory function, and poor dental esthetics in a 30-year-old woman. The surgical and restorative treatment provided for the patient was designed to address her dental phobia, location of residence, and debilitated oral condition. While the following case report details an example of the clinical success that can be achieved through advances in dental implant treatment, the most satisfying event was not necessarily the procedure itself, but the profound change that the generosity of the osseointegration community has made on the life of a needy individual. Through the active leadership of the Osseointegration Foundation Charitable Grant Program, the patient, whose complex treatment is described here, was able to take advantage of treatment that otherwise would not have been available to her. This complex treatment was enabled by the Osseointegration Foundation and other caring donors.