The International Journal of Oral & Maxillofacial Implants, 02/2000

Multinucleated giant cells have been observed at interfaces between bone marrow and titanium implants in mouse femurs. This raises concern that macrophage-derived factors might perturb local lymphohemopoiesis, possibly even predisposing to neoplasia in the B lymphocyte lineage. It has been found that an implant-marrow interface with associated giant cells persists for at least 1.5 years. Precursor B cells show early increases in number and proliferative activity. At later intervals, however, they do not differ significantly from controls, and there are no perturbations in spatial localization of either B lineage cells or DNA-synthesizing hemopoietic cells. The results of this investigation in mice demonstrate that, following initial marrow regeneration and fluctuating precursor B cell activity, and despite the presence of giant cells, titanium implants apparently become well-tolerated by directly apposed bone marrow cells in a lasting state of myelointegration. Keywords: B lymphopoiesis, bone marrow, giant cells, hemopoietic microenvironment, titanium implants

This study investigated the possibility of achieving osseointegration of implants placed in a distracted site during the consolidation period. Four healthy male mongrel dogs were used in this experiment. A subperiosteal corticotomy around the mandible was performed between the left mandibular premolar and first molar. After a 7-day latency period for soft tissue healing, the distraction was performed at the rate of 1 mm per day for 14 consecutive days to allow for 14 mm of elongation, using an extraoral distraction device. Three weeks after the completion of distraction, screw-type implants were placed in the distracted site. Twenty-four weeks after placement of the implants, they were stable, and osseointegration had been achieved physically, radiographically, and histologically. These results suggest the possibility of shortening the period of implant treatment by using the distraction osteogenesis technique. Keywords: bone regeneration, consolidation period, distraction osteogenesis, osseointegrated implant, osseointegration

The aim of this study was to investigate whether a new periodontal ligament attachment will form on titanium implants when they are implanted with cultured periodontal ligament cells. Periodontal ligament cells obtained from the teeth of 3 dogs were cultured and attached to the surface of titanium implants. The implants with the cultured autologous periodontal ligament cells were placed in the mandibles of the dogs. After 3 months of healing, histologic examination revealed that, on some implant surfaces, a layer of cementum-like tissue with inserting collagen fibers had been achieved. These results demonstrated that cultured periodontal ligament cells can form tissue resembling a true periodontal ligament around implants. Keywords: cell culture, implants, periodontal ligament, titanium implants

Quantitative assessment of osseointegration remains a goal of researchers and clinicians alike. In this study, an instrument was designed for this purpose and tested in an animal model. Effective mechanical impedance, linearized for quasi-static force, was measured in 22 implants placed in the hind tibiae of 2 large hounds. The results demonstrate that in this animal long-bone model, the effective impedance of titanium root-form implants exhibits a degree of nonlinear behavior correlated with their state of osseointegration. This observation may be the basis for useful clinical instrumentation. Keywords: animal model, dental, histomorphometry, impedance, implant, mechanical, nonlinear, osseointegration

Four types of implant superstructures were screwed onto implant bodies, and the strains created around the implant bodies were compared and analyzed within the IMZ Implant System. Three IMZ implants were embedded in the center of a polyurethane block (30 x 40 x 30 mm), and a total of 16 superstructures was fabricated by 4 methods: 1-piece cast, 1-piece cast/split soldering, soldering, and passive fit. Six strain gauges were placed on the surface of the block 1 mm apart. Three embedded implants were numbered, and a fixed partial denture was placed on these implants and screwed by a torque wrench using 14.5 Ncm torque. This procedure was repeated 7 times for each fixed partial denture, and each created strain was measured when the last screw was tightened. In all fixed partial dentures, strains were produced around the implant bodies when screws retaining the prosthesis were tightened, and the strain was relieved with unscrewing. The magnitude of strain was greater with the 1-piece cast method or the section/solder method than with the soldering and passive-fit methods. Of the 2 soldering methods, when the screw on the middle implant was tightened before those on the terminal 2 implants, the magnitude of strain was lower with the soldering method than with the 1-piece cast/split soldering method. When the order of screw tightening was changed, there were significant differences in the magnitude of strain at each gauge with the soldering method. With the passive-fit method, no differences in the magnitude of strain attributable to the order of screw tightening could be detected. The magnitude of strain produced around a screw-retained implant prosthesis was significantly lower with the passive-fit method when compared to the other 3 fabricating methods. Furthermore, the implants prepared by the passive-fit method were not affected by the order of screw tightening. Keywords: implant prosthesis, passive fit, strain gauge, stress distribution, tightening screw

This study tested the following hypotheses: (1) acid-cleaned and passivated unalloyed titanium implants have higher surface energies (which are considered desirable for bone implants) than ethanol-cleaned titanium; (2) higher temperatures of heat treatment of unalloyed titanium result in higher surface energies; and (3) these changes can be related to changes in surface composition and roughness. Thus, unalloyed titanium specimens were either acid-cleaned and passivated (CP) or ethanol-cleaned (Et). Each set was then divided into 3 groups and heat-treated for 1 hour at 316°C (600°F), 427°C (800°F), and 538°C (1,000°F), respectively. Surface roughness values for each of these groups were determined using atomic force microscopy, while surface compositions were determined using Auger electron, x-ray photoelectron, and Raman spectroscopic techniques. Surface energies were estimated using a 2-liquid geometric mean technique and correlated with surface roughness, elemental composition, and elemental thickness. The CP surfaces were slightly rougher than the Et specimens, which had greater oxide thickness and hydrocarbon presence. The surface oxides were composed of TiO2, Ti2O3, and possibly titanium peroxide; those heat-treated at 427°C or above were crystalline. The CP specimens had carbonaceous coverage that was of a different composition from that on Et specimens. The CP specimens had significantly higher surface energies, which showed statistically significant correlations with oxide thickness and carbonaceous presence. In conclusion, ethanol cleaning of unalloyed titanium dental implants may not provide optimal surface properties when compared to cleaning with phosphoric acid followed by nitric acid passivation. Keywords: ethanol, passivation, surface characterization, temperature, titanium

Three-dimensional bone response to 3 biomaterials--commercially pure titanium (Ti), hydroxyapatite (HA), and calcium-ion-mixing titanium (Ca-Ti)--embedded in the tibiae of rabbits was examined chronologically. The rabbits were sacrificed at 2, 4, and 8 weeks after implantation, and the percent bone volume around each implant was calculated from the implant surface to each of 4 measurements: 36 µm, 0.25 mm, 0.5 mm, and 1.0 mm in 2 regions (cortical bone and bone marrow regions). Percent bone volume in the cortical bone was consistent, whereas in the bone marrow region, the percent bone volume varied according to implant material, implantation period, and distance from the implant surface. With Ti implants the percent increased gradually up to 8 weeks at each distance, whereas in HA and Ca-Ti implants the percent was largest at 4 weeks and increased closer to the surface. The percent with Ti implants was largest at 36 ìm to 0.25 mm. Aspect of bone response to Ca-Ti was its position intermediate between those of HA and Ti. The decrease of the percent at 8 weeks was smaller than HA. Keywords: calcium-ion-mixing titanium, hydroxyapatite, percent bone volume, 3-dimensional bone response, titanium

The relationship of stress generation upon placement of cement-retained or screw-retained implant restorations has not been thoroughly investigated. Passivity of fit and marginal discrepancies of screw- and cement-retained implant fixed partial denture (FPD) designs were determined using a photoelastic model of a partially edentulous posterior mandibular arch with 3 screw-type implants. Buccal and lingual marginal openings, measured with a traveling microscope before cementation or screw tightening, revealed no statistical difference in adaptation between designs. Screw tightening caused a reduction in marginal opening (changes significant, P .05). The opening with the cemented FPDs was similar before and after cementation. Photoelastic evaluation of the FPDs showed that cement-retained FPDs exhibited a more equitable stress distribution than did their screw-retained counterparts. Keywords: cement-retained, custom abutment, implant biomechanics, implant prosthesis, loading, passive fit, screw-retained, telescopic crown

Craniofacial implants may present peri-implant inflammation because there is no close adhesion of the epithelium to abutments and because of bacteria infiltrating the subcutaneous tissue through the gap. Therefore an attempt was made to improve adhesion of epithelium to abutments. In an in vitro model, adhesion of epithelial cells (HaCat cells) to nonmodified and 3 modified Brånemark System abutment surfaces was quantified. It was found that more cells were adherent in sequence at silicone-coated surfaces, sandblasted surfaces, and collagen-coated (Types I and IV) surfaces than on nonmodified abutments. It was concluded that it is possible to improve epidermal adhesion to abutments through modification of abutment surfaces. Keywords: abutments, adhesion, craniofacial implants, HaCat cells

Single-tooth implants are an increasingly popular method for replacing single teeth. While the effects of growth on implants in children have been well documented, the changes that occur in adults have not been studied with respect to single-tooth implants. It has been assumed that adults are stable and do not change; however, research in the last few years has indicated that adults do change with aging, and adult growth does occur. The changes in adults occur over decades rather than rapidly, as seen in children. Aging changes are readily apparent in the soft tissues of the face and create dramatic changes. Changes in the jaws and teeth occur as a result of continued, slow growth, in contrast to the aging effects seen in soft tissues. Growth changes occur in the arches and result in adaptive changes in the teeth over time, both vertically and horizontally, and in alignment. These dental changes may result in a lack of occlusion vertically or malposition of adjacent natural teeth relative to the implant crown. Clinicians may be well advised to observe and report these changes and warn patients that changes can occur over the service life of the implant-supported crown. These changes may require maintenance adjustments or possible remaking of the implant crown as a result of adult growth, wear, or the esthetic changes of aging. Keywords: adult growth, aging, single-tooth implant

The survival rate of implants placed in the maxillary molar area in a 2-stage procedure was evaluated. Between 1990 and 1997, 60 consecutive patients (32 females and 28 males, mean age 51 years) received 87 implants to replace missing maxillary molar teeth. Radiographs were evaluated preoperatively for bone quantity (mesiodistal width, potential implant length not compromising the integrity of adjacent vital structures). Second-stage surgery was performed in a mean of 7.9 months postimplantation. The 5-year cumulative implant survival rate and the influence of implant characteristics (type, length, diameter, and coating) on implant failure and complication rates (between the 2 stages of surgery) were evaluated. The total 5-year cumulative survival rate was 95.4% (4 implants were lost). There were a total of 17 complications (premature spontaneous implant exposure) in non-failing implants, 11 with high and 6 with flat cover screws, respectively. Implantation in the edentulous maxillary molar area is a predictable procedure with a considerably high survival rate. The type of implant cover screw used can affect the complication rate. Keywords: implants, posterior maxilla, survival rate

Today, most tooth replacement in the esthetic zone is done using implants placed in a delayed surgical protocol. Unfortunately, this delay can result in loss of both hard and soft tissue during the healing period, necessitating guided tissue regeneration techniques at the time of implant placement. Recent developments with tapered implants have facilitated predictable immediate implant placement, preserving the osseous structure surrounding the socket. Further developments with custom healing abutments can preserve the crestal soft tissues, including the papillae. This article reviews techniques that provide for the preservation of both bone and soft tissue while enhancing the esthetic results around implants. Keywords: custom healing abutment, immediate placement, tapered implant, tissue preservation

The fabrication of a complete maxillary implant-supported prosthesis in a patient with slight resorption of the alveolar ridge and a high lip line presents a professional challenge. The implants must be placed with high precision to achieve good esthetics, phonetics, and function. A fixed surgical template using microimplants has been developed for this purpose. The objective of this investigation was to compare a fixed surgical template (FST) to a conventional movable surgical template (MST) for the precise placement of implants in the slightly resorbed edentulous maxilla. Three patients (28 implants), edentulous in the maxilla, with slight ridge resorption, in whom the implants were placed with an FST, were compared with 5 controls having the same characteristics and implants placed with an MST (35 implants). After completion of the prosthesis, occlusal photographs (1:1) were taken, and these images were scanned and transferred to a drawing program in which the contours of the teeth, the ideal emergence position of the occlusal hole of the abutment screw, and its real position were drawn. A blind evaluation was made using the following variables: frequency of location of the abutment screw hole outside of the tooth contour, and the relative measurements of the area of coincidence between the circle that represents the ideal position and real position. A significantly smaller frequency of implants outside the tooth contour was seen with the FST (7%) than with the MST (46%) (P .0008). Also, a significantly higher relative area of coincidence was observed between ideal position and real position in the FST (0.61) than in the MST (0.38) (P .003). This study revealed that considerably higher precision was associated with the use of an FST. Keywords: completely edentulous patient, esthetics, fixed surgical template, implants, microimplants, osseointegration, profile surgical template

An implant-supported prosthesis can potentially provide a functional and esthetic reconstruction, provided that the implants are precisely placed in the predetermined location and angulation. Since the accurate placement of osseointegrated implants in the anterior maxilla with questionable bone support is often a clinical challenge, the use of computed tomography and surgical guides is crucial. This article describes a technique to fabricate a template that served as a guide for radiographic evaluation and was then modified for use in the surgical phase of the treatment. Keywords: dental implants, dual-purpose surgical aid, implant placement, maxilla

A 72-year-old patient underwent the placement of 2 screw-type implants. After 5 months the patient died of a massive stroke, and a block section of the portion of the mandible containing the implants was done. The specimen was treated to obtain thin ground sections. A 1- to 5-µm gap was present between the implant and the healing cover screw, and this space was filled by bacteria and calculus; bacteria were also present in the most apical portion of the hollow part of the implant. An inflammatory infiltrate was present in the connective peri-implant tissues. The spaces between all implant components (implant, abutment, and healing screw) can act as conduits and reservoirs for bacteria, which could cause inflammation of the peri-implant soft tissues. In conclusion, the histologic data from this autopsy case may help to confirm the penetration by fluids and bacteria into the internal portion of the implants, obtained from previous in vitro and in vivo studies. Keywords: bacterial penetration, peri-implantitis, 2-stage implants

Paranasal sinus mucoceles are benign, locally expansile cystlike masses that are filled with mucus and lined with epithelium. Most occur in the frontal sinus. Maxillary sinus mucoceles are presumably uncommon in the United States and European countries, although they have been frequently reported in Japan, particularly following Caldwell-Luc surgery. Clinical symptoms may not appear for at least 10 years postoperatively. Chronic sinus inflammation and allergic disease are also common causes of paranasal mucoceles. This paper provides an overview of maxillary sinus mucoceles and presents a case study involving a 62-year-old Latin male whose asymptomatic maxillary sinus mucocele was not revealed until he presented for maxillary sinus grafting and implant placement. Keywords: maxillary sinus, mucocele, postoperative maxillary cyst, sinus augmentation, surgical ciliated cyst