Tactile sensibility of sapphire endosseous dental implants.

Experiments are described in which the tactile thresholds of sapphire (bioceram) endosseous implants were measured and compared with those of natural teeth. The effects of local anaesthesia were determined in an attempt to localize the mechanoreceptors involved. The thresholds of the implants were higher than those of natural teeth but lower than those of another type of implant (alumina tubingen) examined in another study. The results of local anaesthesia testing indicated that the sensory receptors involved were located in the connective tissues around the implant.     

Surface treatment of dental implants with high-energy laser beam]

In the present study the biological value of the laser prepared titanium implants has been investigated. Screw-type implants with different surface modifications were placed into the femurs of rabbits. Removal torque measurements and histological examinations were prepared. The examinations were divided into two groups. In the first part of the examinations the laser surface treatment was compared to other type of surface modifications. In the examination groups the implants were prepared with the following surfaces: 1. machined, 2. sandblasted, 3. low intensity laser surface, 4. high intensity laser surface, 5. titanium oxide coated surface. In the second part of the examinations laser treatment with different physical variables were observed. It has been concluded, that in both cases the high energy laser treated implants needed higher removal torque and in some cases an osteogenic activity was observed around them in the medullary space as well. The authors think the advantage of laser surface treatment lies in special micromorphology and the increased cleanliness of the surface.     

Smoking and complications of endosseous dental implants

BACKGROUND: The purpose of this study was to compare the incidence of the complications and survival rate related to dental implants among smokers and non-smokers, and to evaluate the influence of smoking by analyzing data of 959 implants placed in 261 patients during the years 1995 to 1998. METHODS: Patients were divided into 3 groups: non-smokers, mild smokers (up to 10 cigarettes per day) and heavy smokers (more than 10 cigarettes per day); smokers were divided into 2 subgroups according to duration of smoking (less or more than 10 years). Complications included minor (spontaneous implant exposure), major (spontaneous implant exposure requiring surgical intervention), and implant failure. The influence of smoking was analyzed for the type of implant cover screw and immediate versus late implantation. RESULTS: The overall failure rate was 2% for non-smokers and 4% for all smokers. Minor and major complications were found in higher percentages (46%) in the smoking groups than in the non-smoking group (31%). A significantly higher incidence of complications was found among smokers who received dental implants with high cover screws (63%) compared to those who received dental implants with flat cover screws (27%). CONCLUSIONS: This study establishes a relationship between implant complications and smoking, implant type (external or internal hex), and time of implantation as significant factors. A higher incidence of complications was found in the smoking group, especially in implants that had a high cover screw. Most complications will not lead to failures. Immediate implants failed less frequently than non-immediate implants. Limiting or reducing smoking habits will decrease complications of endosseous dental implants.     

Effect of Nd:YAG, Ho:YAG, Er:YAG, CO2, and GaAIAs laser irradiation on surface properties of endosseous dental implants

PURPOSE: To analyze potential surface alterations in endosseous dental implants induced by irradiation with common dental lasers. MATERIALS AND METHODS: Sandblasted and acid-etched, plasma-sprayed, hydroxyapatite-coated, and smooth titanium discs were irradiated using Nd:YAG, Ho:YAG, Er:YAG, CO2, and GaAIAs lasers at various power settings. The specimens were examined by scanning electron microscopy and energy dispersive spectroscopy. Results: In an energy-dependent manner, the pulsed YAG lasers induced partial melting, cracking, and crater formation on all 4 surfaces. Within the energy range applied, the CO2 laser caused surface alterations on the hydroxyapatite and plasma coatings as well as in the acid-etched surface. GaAIAs laser irradiation did not damage any of the surfaces. Energy dispersive spectroscopy revealed an altered chemical compound of the surfaces with regard to titanium, oxygen, and silicon. DISCUSSION: The clinical application of most common dental laser systems can induce implant surface alterations. Relevant factors are not only the laser system and power setting, but also the application system. CONCLUSION: The results of the study indicate that Nd:YAG and Ho:YAG lasers are not suitable for use in decontamination of implant surfaces, irrespective of the power output. With the Er:YAG and CO2 laser, the power output must be limited so as to avoid surface damage. The GaAIAs laser seems to be safe as far as possible surface alterations are concerned.     

Quantitation of retention of endosseous dental blade implants in dogs.

This research was initiated in order to study the extraction forces associated with solid, single-vented and multi-vented blade dental implants placed in mandibles of dog for 2 months. An extraction device was used to measure the extraction forces on five of the implants and a histological study was carried out around the sixth multi-vented implant. The main finding was that the extraction forces for the multi-vented blade implants were 6 to 12 times those of the single-vented and solid blades. Other findings in this study were: none of the implants exhibited mobility; sulci ranged from 2 to 3 mm at the implant neck; bone covered the implant shoulder. There was gross and histologic evidence of bone growth in the vents of the multi-vented blade; close adaptation of the bone, connective tissue capsule and implant; and no gross, histologic, clinical or radiographic evidence of bone pathology.     

Histomorphometry of bone apposition around three types of endosseous dental implants.

Three different types of commercially available dental implants (Nobelpharma, IMZ, and Integral) were implanted in the edentulous mandibles of seven adult mongrel dogs. Twenty-one implants were harvested with block sections after 12 weeks and embedded in polymethyl methacrylate resin. Undecalcified sections were prepared with the sectioning-grinding technique. The percentage of bone contacting the implant surface was measured with a self-designed histomorphometry method using a millimeter grid in a stereomicroscope. The results demonstrated a significantly higher percentage of bone along the hydroxyapatite-coated implant than that seen with the titanium-surfaced implant types.     

Initial dissolution rate studies on dental enamel after CO2 laser irradiation.

The influence of CO2 laser irradiation on the dissolution behavior of human dental enamel has been investigated. Human enamel was irradiated by a continuous-wave CO2 laser at 10.6 microns and initial dissolution rates (IDRs) were measured in 0.1 mol/L acetate buffer, pH = 4.5, both with and without calcium and/or phosphate common ion, by means of a rotating disk assembly. The effects of (1-hydroxyethylidene) bisphosphonic acid (EHDP), fluoride (F), and dodecylamine HCl (DAC) at various levels upon the IDR were also determined. All of the findings were consistent with the hypothesis that CO2 laser irradiation converts dental enamel to hydroxyapatite (HAP) possessing site #2 character (Yamamoto et al., 1986). The dissolution driving force function, KHAP = aCa10aPO4(6)aOH2, was found to have a value of 10(-129.9) after being lased, as compared with 10(-121.4) before being lased. The IDR values for EHDP (3 mmol/L) and DAC (3 mmol/L) were essentially zero as expected for site #2 HAP. For solution F, the deduced dissolution driving force function, KFAP = aCa10aPO4(6)aF2 was 10(-128.6) after being lased as compared with 10(-116.3) before being lased. These results all support the hypotheses (1) that laser irradiation may convert the surface of human dental enamel to an apatite of significantly lower effective solubility (i.e., site #2 HAP) than that of unlased enamel; and (2) that there is significant synergism between laser treatment and these chemical dissolution rate inhibitors (again consistent with site #2 HAP). Simple model calculations indicate that, in both the presence and absence of fluoride, these laser-induced changes in the driving force for dissolution should dramatically lessen the susceptibility of enamel to the types of acid challenge that might be encountered in the mouth.     

Electron microscopy of bone response to titanium cylindrical screw-type endosseous dental implants.

This study investigated the undecalcified bone and enveloping tissues supporting commercially pure titanium one-stage and two-stage endosseous dental implants placed into the mandibles of adult mongrel dogs. Correlative light microscopy, transmission electron microscopy, and high-voltage transmission electron microscopy demonstrated a dynamic bone interface to the implants. Mineralized tissue was routinely observed within 20 to 50 nm from the implant interface, separated from the implant interface only by an electron-dense deposit. The densely mineralized collagen fiber matrix was oriented parallel to the implant interface, as were osteocytes that were found close to the interface. Osteocytic projections progressed through canaliculi, often directly to the implant interface. Unmineralized areas that appeared to have the potential for mineralization were also identified.     

Recombinant human bone morphogenetic protein-2 stimulation of bone formation around endosseous dental implants

BACKGROUND: Successful endosseous implant placement requires that the implant be stable in alveolar bone. In certain cases, the implant can be stabilized in native bone but some part of the implant is not covered by bone tissue. This often occurs during placement of implants into extraction sites or in areas where bone resorption has occurred and the ridge width is not sufficient to completely surround the implant. In those cases, the clinician usually employs a procedure to encourage bone formation. These procedures typically include a bone graft and/or membrane therapy. Recent advances have led to the isolation, cloning, and production of recombinant human proteins that stimulate bone formation. One of these bone morphogenetic proteins (rhBMP-2) has been extensively studied in animal models and is currently being tested in human clinical trials. METHODS: In this study, rhBMP-2 was tested using a collagen sponge carrier to stimulate bone formation in defects in the canine mandible around endosseous dental implants. Six animals had a total of 48 implants placed. rhBMP-2 with the collagen carrier was implanted around 24 of these, the remainder having only the collagen carrier placed. Half the sites were covered with a nonresorbable expanded polytetrafluoroethylene membrane. Histologic analysis was performed after 4 and 12 weeks. The area of new bone formed, percentage of bone-to-implant contact in the defect area, and percentage fill of the defect was calculated. RESULTS: The addition of rhBMP-2 resulted in significantly greater amounts of new bone area and percentage of bone-to-implant contact and with more percentage fill after 4 and 12 weeks of healing. The area of new bone formed was reduced after 4 weeks when a membrane was present but after 12 weeks, there was no significant difference between membrane and non-membrane treated sites. In some specimens, new bone was found coronal to the membranes, with rhBMP-2-treated sites having greater amounts than non-rhBMP-2-treated sites. CONCLUSIONS: These data demonstrate that a bone differentiation factor significantly stimulates bone formation in peri-implant bone defects in the canine mandible. In addition, bone-to-implant contact was significantly enhanced along the rough implant surface. Membrane-treated sites had less new bone formation after 4 weeks of healing but were similar to non-membrane sites after 12 weeks. These results demonstrate that rhBMP-2 can be used to stimulate bone growth both around and onto the surface of endosseous dental implants placed in sites with extended peri-implant osseous defects.     

Threshold of tactile sensitivity perceived with dental endosseous implants and natural teeth

The aim of this study was to determine the threshold of tactile perception of endosseous dental implants and to assess the relative difference of that threshold between implants and teeth. Twenty‐two subjects with implants of the ITI® Dental Implant System were included in the study. All implants served as abutments for single tooth crowns and had been in function for a minimum of 1 year. A strain gauge glued to the shaft of an amalgam plugger served as a force sensor. It transformed the elastic deformation exerted onto the shaft into an electronic signal for recording. By use of the amalgam plugger, a continuously increasing force was exercised on the implants or teeth until the first sensation of touch was indicated by the patient. Statistical analysis revealed threshold values for the implants ranging from 13.2 to 189.4g (1g=0.0lN)(mean 100.6; SD 47.7), while a range of 1.2 to 26.2g (mean 11.5; SD 11.5) was found for control teeth. Thus, the mean threshold values for implants were 8.75 times higher than for teeth. This difference was highly statistically significant. A general linear models procedure was applied to determine the influence of patient age, jaw, implant position and the threshold values of teeth on the measurements obtained for implants. Only gender and the threshold values for contralateral teeth had a significant influence. These 2 parameters together explained 27% of the variability in threshold measurements. It is concluded that a more than 8‐fold higher threshold value for tactile perception exists for implants compared with teeth.     

Implant-tissue interface of endosseous dental implants in dogs. Validity of clinical evaluation methods

Plaque and gingival bleeding were scored and probing, radiography, and histologic methods were used to evaluate clinical methods for estimating alterations of supporting structures at functioning endosseous dental implants. Twelve implant abutment posts in three Labrador retriever dogs were assessed. The observation period was 3 months of submerged healing followed by 6 months in function.In the presence of daily gingival cleaning, both plaque and gingival bleeding scores were reduced on implant abutments. No correlation was found between gingival scores and the degree of bone resorption.The correlation between probing and radiographic measurements was studied by comparing 136 parallel measurements. The average difference was 0.4 mm. Discrepancies were observed when evaluating bone loss that reached the shoulder area. Better accordance was obtained when moderate (2 to 4 mm) or extensive (6 to 8 mm) resorption was assessed.Histologic evaluation indicated alternating regions of implant-bone contact and fibrous encapsulation. Progressive infiltrates were observed in the permucosal area, sometimes extending into the deeper parts of the supporting bone.A combination of probing and radiographic measurements seems to give the most reliable information about the level of bone support and is recommended to be included in routine control of implant abutments.     

Use of bovine osteogenic protein to promote rapid osseointegration of endosseous dental implants.

An enriched bovine osteogenic protein preparation in combination with bone collagen matrix (osteogenic protein device) was used to effect new bone growth in extraction sites in the presence or absence of titanium dental implants. Incisor and canine teeth were extracted from each of three cynomolgus monkeys, and implants were inserted directly into the sockets without surgical site preparation. The osteogenic protein device induced new bone formation in close apposition to the titanium implants in all trials within 3 weeks. A lesser amount of new bone formation in both sets of control sites was limited to the bony socket walls and not closely apposed to the implant. These data show that the osteogenic protein device is capable of inducing new bone formation in tooth sockets within 3 weeks in the presence or absence of titanium implants. This is the first known demonstration of the therapeutic induction of bone formation in close apposition to metallic implants.     

Reduced corrosion of CP Ti and Ti-6A1-4V alloy endosseous dental implants after glow-discharge treatment: a preliminary report.

Inductively coupled argon plasma spectroscopic analysis was used to quantify titanium, aluminum, and vanadium corrosion products released by superficial layers of identically shaped commercially pure titanium and Ti-6A1-4V alloy dental implants. Halves of each of two originally sterile groups were analyzed directly from the manufacturer's packaging and the other halves received glow-discharge treatment prior to their corrosion assay. The implants were incubated in pH 3 modified saline solution and were analyzed after 2- and 12-week corrosion periods. Implants treated with glow discharge showed statistically significant reduction in the amounts of corrosion products released, apparently as a result of glow-discharge-produced surface oxides of greater passivity than originally present.     

The reconstruction of bilateral clefts using endosseous implants after bone grafting.

This article presents the orthodontic reconstruction of an adult bilateral cleft patient with a severe Class III malocclusion in which endosseous implants were inserted after secondary alveolar bone grafting. The patient was a 21-year-old Japanese male whose lateral incisors were congenitally missing and whose premaxilla was inclined lingually. The occlusion was classified as Angle Class III with an overjet of -8 mm. Orthodontic alignment was initiated to correct the position of the maxillary incisors before bone grafting. After the anterior occlusal relationship was corrected, bilateral alveolar clefts were reconstructed by bone grafting with autogenous particulate marrow and cancellous bone harvested from the iliac crest. ITI-SLA fixtures (Institute Straumann, Waldenburg, Switzerland) (length, 10 mm; diameter, 4.1 mm) were placed into the grafted bone for prosthetic restoration of the missing lateral incisors. The results illustrate that this protocol can be expected to provide an acceptable occlusion and good dentoalveolar stability in adult cleft patients.     

Relation between smoking and biomarkers of bone resorption associated with dental endosseous implants

The aim of this study was to determine the effects of smoking on pyridinoline concentrations in crevicular fluid collected from around dental implants. Samples of crevicular fluid were collected from 4 sites around each implant and tooth, if present, for a group of 16 patients using methylcellulose strips. Samples were collected from 104 implants and 49 teeth. Eight of the 16 patients were current smokers. Crevicular fluid samples were eluted from methylcellulose strips using phosphate-buffered saline containing 0.1% bovine serum albumin and centrifugation. Pyridinoline was quantified using a competitive enzyme immunoassay. Results showed that there were statistically insignificant differences between the amounts of pyridinoline (mean +/- standard deviation [SD]) around teeth of nonsmokers versus smokers (0.011 +/- 0.003 and 0.014 +/- 0.006 nmol/L, respectively). However, the mean (+/- SD) pyridinoline levels around the implants of nonsmokers (0.012 +/- 0.018 nmol/L) were significantly (P <0.01) less than that of smokers (0.030 +/- 0.006 nmol/L). These results demonstrate that pyridinoline levels are specifically elevated in the crevicular fluid associated with endosseous dental implants of smokers and suggest that smoking may affect implant success in part through alterations in the levels of bone resorption.     

A 3 to 4 year study of single tooth hydroxylapatite coated endosseous dental implants.

OBJECTIVE: To evaluate the clinical effectiveness, common complications and maintenance associated with hydroxylapatite (HA) coated cylindrical implants when used to support single crowns. DESIGN: A prospective medium term clinical study of the Calcitek HA-coated implant. SETTING: Implant placement, crown fabrication and follow-up procedures were carried out at the Leeds Dental Institute, between 1990 and 1998. SUBJECTS AND METHOD: 26 patients (33 implants) participated in the trial. They were referred from general dental practitioners because of their suitability for single tooth implant placement. MAIN OUTCOME MEASURES: The implants were assessed using recognised clinical review procedures e.g. radiographs and soft tissue assessments. RESULTS: At exposure there was 100% implant integration. The cumulative survival rate over 4 years was 100%. In five implants there was cervical bone loss of more than 4 mm and these were classified as failing. This gave an overall cumulative success rate of 58% by year 4. CONCLUSION: The Calcitek HA-coated single tooth implant shows exceptionally high initial integration however, the longer term results suggest that the cervical bone level adjacent to the implant failed to establish a steady state. Doubts remain regarding the long-term prognosis of these cylindrical HA-coated implants.