The International Journal of Oral & Maxillofacial Implants, 04/1998

To propose a mechanism for apical epithelialization at the implant-tissue interface, cell contact to titanium surfaces and adhesive strength of epithelial-like (HGE) and fibroblastic (HGF) cells derived from human gingiva were investigated under three different media conditions containing plaque extracts: nonfiltered, 5-µm pore filtered, and 0.22-µm pore filtered. The plaque extracts had a greater effect in decreasing the growth rate of the HGF than of the HGE. Similarly, the HGE exhibited greater adhesive strength than the HGF. These differences in the cells resistance to plaque extracts were also observed using light and electron microscopy. Evidence from this study suggests that the difference in growth, contact, and adhesive strength of the HGE and HGF cells to titanium surfaces may promote apical epithelialization under the pathologic condition. Keywords: biologic seal, cell culture, epithelialization, plaque extracts

Clinical measurements on gingival indices and morphologic observations were performed in this study to verify the defending mechanism of gingival soft tissue against foreign invasions from the perspective of epithelial adhesion/attachment to implant surfaces in the monkey mandible. The following zones were observed using scanning electron microscopy: (1) plaque zone, suggesting susceptibility of the gingival tissue to bacterial invasion; (2) nude zone, demonstrating indirect adhesion of epithelial cells to the implant surface through the mucous layer and preventing bacterial invasion; and (3) epithelial cell attached zone, having greater bond strength of epithelial cells at the cell-implant interface as compared to cell-cell bonding within the epithelial cell layer. This study suggested that epithelial cell attachment/adhesion may play a dominant role in retaining the successful condition of a dental implant. Keywords: biologic seal, cell adhesion, gingival index, implant, scanning electron microscopy

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

This research examined the nature and role of a linea alba, found consistently at the crest of edentulous ridges in dogs. Angiovist dye was used to outline the microvasculature in these regions. The findings demonstrated a zone of avascularity directly beneath each linea alba. When novel incision designs were used in the gingivae and the outlined mucoperiosteal flaps were elevated and then replaced, alterations in underlying bone morphology were noted. In a subsequent study during which implants were placed, a direct relationship was noted between incision design and level of pericervical bone support. Keywords: alveolar bone, implant, incision, linea alba, vascularity

Osseointegration involves an osseous healing response that may be compromised by aging. This study aimed to test the hypothesis that there is no difference between older and younger adults in osseointegration success. A comparison was made between closely matched groups of 39 older adults who had 190 implants supporting 45 oral prostheses and 43 younger adults who had 184 implants supporting 45 oral prostheses. Patients were monitored for a period of 4 to 16 years after prosthetic loading. At the most recent follow-up, the cumulative implant success was 92.0% for the older group compared to 86.5% for the younger group. No statistical significance could be attributed to the difference in implant survival between the groups throughout the study period. Furthermore, the most common outcome for individual prosthetic sites was 100% implant success, and the original prosthetic design was maintained for as long as each patient was monitored in 41 of 45 prosthetic prescriptions for the older patients, and in 39 of 45 prescriptions for the younger patients. Keywords: age, clinical effectiveness, older adults, oral implants, osseointegration, success

The purpose of this prospective study was to investigate the clinical outcome and marginal bone resorption of three different endosseous implants placed in the anterior mandibles of 15 elderly patients. Eleven women and 4 men (ranging from 65 to 80 years, mean 71 years) had three different endosseous implants placed in the anterior mandible; one titanium plasma-sprayed cylinder implant (4-mm diameter), one titanium cylinder implant with hydroxyapatite coating (4-mm diameter), and one standard threaded titanium implant (3.75-mm diameter). Three months later, at the second-stage surgical procedure, ball abutments were connected and an overdenture was placed. At 12, 24, and 36 months, marginal bone resorption and Periotest values were recorded. None of the implants was lost in this period. An analysis of variance with repeated measurement was performed annually to test the existence of significant differences between the implants. When differences appeared, paired t tests were used to identify which differences were significant. Bonferroni multipliers were used to adjust for multiple testing. When marginal bone resorption was concerned, threaded titanium and hydroxyapatite-coated implants had significantly better scores than titanium plasma-sprayed cylinder implants. Periotest values for hydroxyapatite-coated implants were significantly better than test values for the other implants after 2 years. After 3 years significance was obtained between hydroxyapatite and screw-shaped implants only (P .05). It was concluded that titanium plasma-sprayed cylinder implants have a less favorable prognosis than the other implants used in this study. Keywords: clinical follow-up, hydroxyapatite-coated implants, marginal bone resorption, overdentures, titanium plasma-spray-coated implants, titanium threaded implants

Nineteen patients who were treated for oncologic pathology by surgery and radiotherapy (average dose = 57 Gy) received prosthetic reconstruction with 53 implants placed in the residual mandible or maxilla and/or replacement bone graft. Implants were placed within a minimum period of 5 months after radiotherapy. The healing period before placement of the prosthesis also was at least 5 months. Two to six implants were placed as a function of tooth loss and required prosthetic design. Prostheses included both removable and fixed restorations. Two implants were lost as a result of osseointegration failure. Fifteen implants in six patients could not be followed throughout the study because of patient expiration. Patients were followed up to 68 months and for an average of 38 months. No osteoradionecrosis phenomenon was seen in this study. However, caution is urged in placing implants in irradiated bone because of the potential for osteoradionecrosis. Patients should be carefully selected and a strict therapeutic protocol should be followed. Keywords: implants, irradiated patients, prosthetic reconstruction

In this study, a new approach involving placement and subsequent retrieval of titanium microimplants was employed for the histologic investigation of the implant-tissue interface in conjunction with maxillary sinus floor augmentation. Nine patients scheduled for sinus floor augmentation and simultaneous placement of Brånemark implants were included in the study. After a sinus graft procedure and placement of implants, an additional microimplant was placed into the graft through the lateral wall of the sinus. At abutment connection, the microimplants were retrieved using a 3- or 5-mm-wide trephine drill. Six specimens were retrieved after 6 to 14 months from sites augmented with particulate radiated mineralized cancellous allograft. Another six implants were retrieved after 6 to 12 months from maxillary sinuses augmented with particulate autogenous bone grafts. The histologic analysis showed distinct differences between the two types of grafts. The sites with autogenous bone grafts displayed a normal morphology of bone and bone marrow, including formation of bone on the surfaces of the grafted particles and remodeling of newly formed as well as grafted bone. The bone was more mature after 11 to 14 months than at 6 months. The allografted sites had a mixed morphologic appearance of newly formed bone and nonviable allograft particles (about 75% of the total bone area) in loose connective tissue. Significantly more bone was found at the autografted than at the allografted implants. The use of autogenous bone for augmentation of the maxillary sinus floor resulted in a greater amount of viable bone surrounding the implant; however, simultaneous placement of implants apparently resulted in a low proportion of bone-implant contact after 6 to 14 months irrespective of graft type. Keywords: allograft, autograft, histology, osseointegration, sinus floor augmentation, titanium oral implants

The aim of this study was to test whether bone could be formed in peri-implant defects at immediate transmucosal implants using guided bone regeneration. Ten patients (median age 48 years) underwent comprehensive dental care including the placement of an implant into an extraction socket immediately following removal of a tooth. An expanded polytetrafluoroethylene membrane and the mucoperiosteal flap were adapted around the neck of the implants, leaving the sites to heal in a transmucosal fashion. During implantation (baseline) and at membrane removal surgery 5 months later, the following clinical measurements from the implant shoulder were assessed at six sites: implant-bone contact (defect depth), level of the alveolar crest, level of the membrane, and distance from the crest to the implant body (defect width). Estimates of the defect volume bordered by the membrane, the implant, and the bony walls were calculated. At baseline, the mean defect depth was 4.7 mm (SD 1.3 mm, range 1 to 14 mm). At membrane removal, the mean defect depth had decreased to 2.1 mm (SD 0.8 mm). Compared to baseline, this decrease was statistically significant (P .01). The mean increase in bone height at the deepest defect site of each implant was 6.7 mm (SD 3.0 mm), which was significant (P .01). At baseline, the mean value for the defect volume estimates was 9.45 mm3 (SD 5.75 mm3). At membrane removal, a significant decrease (P .01) was found. After 5 months, 94% of the area beneath the membrane was filled with new bone. It was concluded that guided tissue regeneration at immediate transmucosal implants is successful in generating bone into peri-implant defects. Keywords: e-PTFE membrane, guided bone regeneration, implantation, new bone formation, transmucosal

This retrospective study involved Japanese patients with prostheses supported by Brånemark implants following maxillectomy. Questionnaires were sent to 75 institutions, and data on 19 patients were collected from 8 institutions. The mean age of patients at the time of implant placement was 64.2 years (range 22 to 82 years). The mean follow-up time was 27.6 months. Of the 81 implants placed, 16 were lost for an implant survival rate of 80.2%. The effects on implant survival rate of radiotherapy, chemotherapy, hyperbaric oxygen therapy, and the support system of the prosthesis were analyzed, but no significant differences were observed. Keywords: Brånemark implants, chemotherapy, maxillary prostheses, maxillary tumor, multicenter study, radiotherapy, survival rate

Edentulous patients with a severely resorbed mandible often experience problems with their dentures. Treatment concepts involving two to four implants for the support of an overdenture have been proposed. The aim of this study was to develop a treatment concept for mandibular overdentures supported by endosseous implants based on a review of the literature. It is proposed that two implants supporting a mandibular overdenture (bar construction) are sufficient for most applications. Four implants are indicated in situations involving a dentulous maxilla, a narrow mandibular arch, extreme resorption of the mandible (bone height greater than 12 mm), and mandibular soreness and pain. Keywords: implants, mandible, overdenture, review

The effectiveness of dental implants is widely studied, especially in terms of their clinical outcomes. However, from the policymakers point of view, variables other than safety and efficacy, such as the costs and effectiveness of dental implants as compared to other treatment alternatives, are vital in decision making. This paper compares the costs of different treatment strategies in a randomized clinical trial in patients with resorbed mandibles and persistent problems with their conventional dentures: treatment with a mandibular overdenture on permucosal dental implants, an overdenture on a transmandibular implant, new dentures after preprosthetic surgery, and new dentures only. Data were gathered on an individual patient level to gain insight into specific cost episodes. Direct costs were subdivided into labor, material, technique, and overhead. Data concerning these components were gathered during the consecutive treatment phases in the first year. Results show that the resources used to treat a patient with an overdenture supported by a transmandibular implant are seven times those of a complete new set of dentures. Comparison of the cost ratio of an implant-retained overdenture supported by permucosal implants and conventional new prostheses proves less unfavorable: 1:3. New dentures after preprosthetic surgery are almost as expensive as treatment with permucosal implants. Keywords: costs, dental implants, dentures

One hundred eighty-five dental implants loaded for at least 1 year in 49 patients treated with ablative tumor and reconstructive surgery in the oral cavity were examined to ascertain peri-implant bone resorption. While 96 implants penetrated local mucosa and served as the control group, 27 implants were associated with split-thickness skin grafts, 9 in mucosal grafts, 18 in myocutaneous flaps, 30 in jejunal grafts, and 5 in a vastus lateralis and a temporalis muscle flap. Restoration type was similar in all groups (overdentures) except for implants placed in the jejunal grafts (fixed implant-supported prostheses). Regular follow-up was done over an observation period of 3 to 5 years after implant placement. Overall survival rate of the 89 implants surrounded by transplanted soft tissues was 94.1%. Bone loss under the various transplanted soft tissues was similar to or less than that under local mucosa. Over time, only horizontal bone resorption under jejunal grafts and vertical bone resorption under mucosal grafts showed higher values. Mean values of all measurements for split-thickness skin grafts were higher than for local mucosa for the horizontal as well as for the vertical resorption pattern. It can be concluded that transplanted tissues foreign to the oral cavity have no detrimental effect on bone resorption around loaded dental implants and do not endanger their long-term stability. Of all the transplants used, split-thickness skin grafts are least recommended as peri-implant soft tissue. Keywords: dental implants, jejunal graft, long-term results, myocutaneous flaps, peri-implant bone loss, soft tissue

Although they are fortunately rare, implant fractures can cause significant problems for both clinicians and patients. The authors present a light and scanning electron microscopic study of four fractured implants in two patients. Both patients had parafunctional habits (bruxism), hypertrophic masticatory muscles, and wear of occlusal surfaces. The scanning electron microscopic study of the fractured surfaces of all four implants showed the presence of fatigue striations. Bending overload was probably created by a combination of parafunctional forces, bone resorption, posterior location of the implants, and implant diameter. Keywords: bending moments, biomechanics, bone resorption, bruxism, fractures overload, implant failure, metal fatigue

A revised stage-two technique, suitable for the severely resorbed mandible, is described. The objective is to eliminate mucosal mobility around the peri-implant area. This is achieved by means of a technique that limits the detachment of the lingual flap, augments the band of attached masticatory mucosa with a free gingival graft, deepens the vestibule, and prevents the reattachment of the muscles by means of a postsurgical stent. Keywords: attached masticatory mucosa, free gingival graft, implants, muscle pull, postsurgical stent, severely resorbed mandible, stage-two surgery, vestibule

This article presents a simple, inexpensive method for precisely locating the floor of the maxillary sinus, as well as the presence of any septa, at the time of sinus augmentation surgery. Using an anesthesia light wand placed transnasally to illuminate the sinus, the surgeon can reliably elevate the lateral maxillary wall overlying the sinus with relative ease without fear of placing the osteotomy cuts too far from the sinus floor. The same procedure can be used postoperatively to evaluate the density of the bone graft placed into the sinus prior to closure. Keywords: light wand, maxillary sinus, sinus augmentation, transillumination