The International Journal of Oral & Maxillofacial Implants, 03/1993

This study evaluated patients who were reconstructed with the IMZ system, which consists of a cylindrical implant with an intramobile element for stress relief. It is placed through a two-stage surgical procedure resulting in osteointegration. During a 5-year period, 1,059 implants were placed in 322 patients. Twenty-one implants were lost to follow-up. A total of 28 implants failed over the 5-year period, of which 9 had not integrated at stage 2 surgery. Of the remaining implants, 19 failed primarily for periodontal and prosthetic reasons. The life table method was used for statistical analysis. The 5-year survival rate of all IMZ implants was 95%. Seventy-five percent of the implants were placed to restore partial edentulism, with a survival rate of 96%. The survival rate for totally edentulous patients was also 96%. Forty-four percent of the implants were placed in the maxilla, with a survival rate of 92%. The survival rate in the mandible was 99%. Sixty-six percent of the implants were placed in women, with a survival rate of 94%. The survival rate in men was 98%. Major factors that positively influenced long-term survival were use of the longest and largest-diameter implants appropriate for the clinical situation. Keywords: life table, lost to follow-up, IMZ implant, osteointegration, partial edentulism, total edentulism

It is usually suggested that loading forces be transmitted to implants in the vertical direction. In 44 subjects treated with mandibular implants and overdentures, the inclination of the implant axis relative to the occlusal plane of the corresponding prostheses was measured by means of cephalometric radiographs. The degree of mandibular atrophy was also assessed. Peri-implant parameters such as plaque index, bleeding scores, and probing depths were registered on four implant sites. About 70% of the implants showed a buccal inclination, 11% showed a lingual inclination, and only 19% were found with an angle of 90 degrees. After an observation period of 5 years, no positive relationship between inclination of the implant axis, mandibular atrophy, and peri-implant findings could be established. Aspects of facial morphology and the interalveolar relationship of both jaws should be considered additional parameters and should be included in investigations concerning functional dynamics of removable dentures. Keywords: cephalometry, implants, mandibular atrophy, overdentures

Using 3H-thymidine-labeled MC3T3-E1 osteoblastic cells, the number of osteoblasts bound to titanium surfaces after various surface treatments and incubation periods was directly measured. MC3T3-E1 cell binding to titanium surfaces was saturable at a low level (approximately 10,000 cells/cm2). Although treatment of these surfaces with fibronectin, keratin sulfate, and the fibronectin-derived peptide GRGDS (glycine-arginine-glycine-glutamate-serine) increases cellular binding by 29% to 31%, the relative binding to titanium was 5 to 10 times lower than binding to collagen I gels. A collagen I matrix competed with the commercially pure titanium surfaces for cell binding from solution, suggesting that direct binding of osteoblasts to titanium surfaces present within an organic matrix may not be favored. The significance of immediate and direct bone cell attachment to titanium surfaces for osseointegration should be reevaluated. Keywords: cell attachment, osseointegration, titanium

A review of the peri-implant sulcus, including the histology of the sulcular epithelium, epithelial attachment, and the gingival connective tissue, is presented. The peri-implant junctional epithelial attachment is mediated by hemidesmosomes, as in the periodontal tissue. There is some controversy on the possible attachment of connective tissue fibers to the implant, but current studies indicate a parallel orientation with no insertion of the peri-implant connective tissue fibers. This difference in connective tissue attachment may affect the peri-implant tissue's susceptibility to disease. Keywords: epithelial attachment, gingival connective tissue, histology, peri-implant sulcus, sulcular epithelium

This study evaluated the treatment of ligature-induced peri implantitis using guided tissue regeneration (GTR) around submerged and nonsubmerged implants in beagle dogs. Two titanium implants were placed bilaterally in the premolar regions of the mandible in each of 10 beagle dogs. Cotton floss ligatures were placed around the implant necks and no oral hygiene procedures were performed for 5 months. Periodontal surgery was performed, and in five dogs (submerged group) the abutments were removed and an e-PTFE barrier was placed to cover the test implants and their adjacent osseous defects, while the control implants received no barriers. In the other five dogs (nonsubmerged group), flap surgery was performed without removing the abutments. In the test sites, an e-PTFE barrier was placed around the abutment and adjacent defects, while on the control sites no barrier was placed. Nondecalcified specimens were prepared using standard histologic methods and analyzed. No differences were found between any of the clinical parameters in both the control and experimental sites from the submerged and nonsubmerged groups. Histologic and histomorphometric analyses also revealed no significant differences between groups with regard to new bone formation. In the experimental (GTR) groups, however, the amount of regenerated connective tissue was significantly greater than on the control groups. Under the conditions of this study, the treatment of peri-implantitis using GTR did not enhance clinical parameters or bone formation around diseased implants. Keywords: dental implants, guided tissue regeneration, peri-implantitis, regeneration, wound healing

The inferior alveolar nerve may extend beyond the mental foramen as an intraosseous anterior loop. The purpose of this study was to determine if panoramic radiography accurately identifies the anterior loop of the inferior alveolar canal. Adult skulls (n = 25) were radiographed using two panoramic machines both with and without radiopaque markers placed into the inferior alveolar canal and anterior loop. The anterior loop was also measured directly using flexible tubing (2 mm in diameter). Significantly fewer loops were detected in radiographs as compared with anatomic assessment (P .001). A significant loop (>2 mm) was identified in 92% to 96% of the direct measurements, whereas radiographs identified only 56% (Panelipse) and 76% (Orthoralix). Analysis of variance demonstrated that the skeletal length of the anterior loop was significantly greater than that measured radiographically (P .0001). The average length of the anterior loop based on direct measurements was 6.95 mm, whereas radiographic measurements were 3.18 mm (Panelipse) and 3.45 mm (Orthoralix). The difference in detection of anterior loops among the radiographic procedures studied was not significant (P > .05). Keywords: anterior loop, inferior alveolar nerve, radiography

An animal study was conducted with unloaded blocks and hydroxyapatite (HA)-coated titanium implants. Four HA blocks were positioned in rabbit tibiae and four HA-coated titanium implants were positioned in pig tibiae. Implants were positioned so that half was placed in cortical bone and half in medullary space. Biopsy specimens were taken 4 months after implant placement for histologic evaluation. Light microscopy and confocal laser scanning microscopy demonstrated that the HA resorption rate was higher in the medullary spaces, whereas resorption was almost absent in the areas embedded in cortical bone. Keywords: cortical bone, hydroxyapatite, medullary bone, resorption

The longevity of an osseointegrated implant is directly affected by the maintenance of its osseous anchorage. Progressive marginal bone loss would be detrimental to its survival. This article proposes a new radiographic index for use in the radiographic assessment of peri-implant marginal bone levels. The index scores range from 0 to 6 and denote marginal bone loss in percentages relative to the implant body length measured from its coronal-most margin in an apical direction. The proposed index should be of significance in: (1) use of short implants (7 to 10 mm); (2) evaluation of implants functioning in areas of low bone density (types 3 and 4); (3) prognosis and treatment of ailing/failing implants; (4) follow-up of implants placed in extraction sites; and (5) correlation of crown-to-implant ratio with marginal bone loss. Keywords: marginal bone level, osseointegration, radiographic index

A palatal lift prosthesis (PLP) is a prosthetic speech aid used to compensate for palatopharyngeal incompetence. However, it requires dental abutments to facilitate its function. In two edentulous patients with cleft palate, hydroxyapatite-coated dental implants were used to increase PLP retention. In both cases, palatopharyngeal closure was obtained and PLP function was deemed effective, as determined by speech evaluation and nasal air flow measurements, for more than 3 years. This treatment is useful for enhancing the retention of a PLP in patients who have few or no remaining natural tooth abutments. Keywords: cleft palate, dental implant, palatal lift prosthesis

The edentulous mandible provides a frequent indication for oral implants. In many cases implants are placed in the interforaminal region to support fixed prostheses or give retention to removable overdentures. One of the hazards of this seemingly safe surgical area is hemorrhage of the floor of the mouth. In this article, two cases of this life-threatening complication are reported. Keywords: complication, floor of the mouth, hemorrhage, interforaminal region, oral implants

A technique is described for augmenting an edentulous ridge buccally with a mixture of freeze-dried bone and resorbable tricalcium phosphate covered with a Gore-Tex membrane. Titanium screws are used to prevent the collapse of the regenerative materials. In the patient described, the buccolingual dimensions of the edentulous mandibular ridge more than doubled, thus allowing the placement of two implant cylinders. The rationale for such a procedure is discussed. Keywords: bone graft, guided tissue regeneration, membrane, ridge augmentation, titanium implants, tricalcium phosphate