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PubMed2001

Effect of recombinant human bone morphogenetic protein-2 on bone regeneration and osseointegration of dental implants.

Recombinant human bone morphogenetic protein-2 (rhBMP-2) induced bone regeneration and osseointegration was evaluated in bony defects created within the hollow chamber of endosseous dental implants in 14 foxhound dogs. Bilateral extractions of mandibular premolars were performed and surgical implantation of 104 hollow cylinder implants followed after 8 weeks of healing. Experimental implants had their hollow chamber filled with 20 microg of rhBMP-2 delivered with a bovine collagen carrier, whereas the control implants had their apical chamber left empty. Dogs were followed for 2, 4, 8 and 12 weeks. Histomorphometric evaluation and immunohistochemical analysis were performed. Minimal bone was regenerated at 2 weeks for both groups. At 4 weeks, bone fill averaged 23.48% for the rhBMP-2 and 5.98% for the control group (P<0.05). At 8 weeks, mean bone fill was 20.94% and 7.75% for the rhBMP-2 and the controls, respectively (P<0.05). At 12 weeks, mean bone fill was 31.39% and 24.31% for the rhBMP-2 and control implants, respectively (P>0.05). Bone-implant contact (BIC) increased for both groups over time and at 8 weeks the rhBMP-2 BIC value was 18.65% and for the control 7.22% (P<0.05). At 12 weeks, the BIC was 43.78% and 21.05% for the rhBMP-2 and the control group, respectively (P<0.05). Immunohistochemical staining for type II collagen was positive only for parts of the collagen carrier and formation of cartilaginous intermediate was not observed in any of the specimens. The results suggest that, in confined defects adjacent to dental implants, rhBMP-2 can induce bone regeneration in close apposition to the implant surface.

Animals↗
PubMed2003

Corrosion behaviour of commercially pure titanium shot blasted with different materials and sizes of shot particles for dental implant applications.

It is well known that the osseointegration of the commercially pure titanium (c.p. Ti) dental implant is improved when the metal is shot blasted in order to increase its surface roughness. This roughness is colonised by bone, which improves implant fixation. However, shot blasting also changes the chemical composition of the implant surface because some shot particles remain adhered on the metal. The c.p. Ti surfaces shot blasted with different materials and sizes of shot particles were tested in order to determine their topographical features (surface roughness, real surface area and the percentage of surface covered by the adhered shot particles) and electrochemical behaviour (open circuit potential, electrochemical impedance spectroscopy and cyclic polarisation). The results demonstrate that the increased surface area of the material because of the increasing surface roughness is not the only cause for differences found in the electrochemical behaviour and corrosion resistance of the blasted c.p. Ti. Among other possible causes, those differences may be attributed to the compressive residual surface stresses induced by shot blasting. All the materials tested have an adequate corrosion and electrochemical behaviour in terms of its possible use as dental implant material.

Corrosion↗
PubMed1983

[Dental implants and their materials].

Some new trends in materials for dental implants, which also effect in the operative techniques and implant design, are described. Advantages and shortcomings of the different material types are exemplified and correlated with their bioinert resp. bioactive functions. The practical interest in metallic implants focussed in titanium resp. oxide ceramics in the ceramic field, whereas the special goal of implant research follows from the improvement of the bioactive principle with loaded calcium phosphate implants.

Biocompatible Materials↗
PubMed1997

Osseointegration of dental implants in rabbit bone with low mineral density.

PURPOSE: The purposes of this study were to establish an experimental animal model with bone of low mineral density, and to then investigate the reaction of the bone-implant interface in these experimental animals. MATERIALS AND METHODS: To prepare the experimental model, rabbits were ovariectomized and fed a 0.15% low-calcium diet. The bone mineral density (BMD) of the tibia was periodically measured by dual-energy X-ray absorptiometry. Approximately 1 month after the introduction of the low-calcium diet, when BMD had decreased to about 12% less than that of control rabbits, a titanium implant (TI) was inserted into the tibia of each rabbit. At 2, 4, 8, and 12 weeks after the insertion of the TI, the rabbits were killed, and the reaction of the bone tissue surrounding the TI was examined both histologically and radiographically. RESULTS: The combined ovariectomy and low-calcium diet produced rabbits having bone with low mineral density, and the histologic features of the tibia in these rabbits were consistent with those in human osteoporotic bone. In control rabbits, new bone formation surrounding the TI was evident 2 weeks after its insertion, and the TI surface was almost completely covered with new bone after 8 weeks. In contrast, new bone formation in the experimental rabbits was delayed, but considerable direct bone contact with the TI was observed after 12 weeks. CONCLUSION: These results suggest that osteoporotic bone may affect the healing period of bone tissue after the insertion of dental implants, but that osseointegration of dental implants may be obtained even in osteoporotic bone.

Animals↗
PubMed2000

In vivo, thyroid and lens surface exposure with spiral and conventional computed tomography in dental implant radiography.

OBJECTIVE: To compare the surface dose exposure to the lens of the eye and the thyroid gland received by patients undergoing spiral and conventional computed tomography (CT) examinations during dental implant pretreatment evaluation in critical radiosensitive structures of the maxillofacial region. STUDY DESIGN: Two groups of 10 patients each had a dental implant CT examination performed, with 5 patients in each group having maxillary and 5 having mandibular examinations. One group was examined with conventional CT and the other with spiral CT. Seven examination parameters were standardized to both types of examinations. Lithium fluoride thermoluminescent dosimeters were placed over the thyroid gland, lateral orbit, and infraorbital foramen of each patient to measure the surface dose. The Wilcoxon rank sum test was used to compare doses, with statistical significance set at P <.05. RESULTS: For the maxillary examination, there was a 57.4% reduction in the surface dose at the lateral orbit, 47% at the infraorbital foramen, and 60.8% at the thyroid when spiral CT was used instead of conventional CT with the same parameters. Similarly, for the mandibular examination, there was a 57.4% reduction at the lateral orbit, 60% reduction at the infraorbital foramen, and 70.9% at the thyroid. All the dose reductions were statistically significant at P <.05. CONCLUSION: The use of spiral CT for preimplant evaluation reduces the surface absorbed dose in certain critical structures of the maxillofacial region compared with conventional CT.

Adult↗
PubMed1994

Applications of guided tissue regeneration with dental implants.

This article has discussed and illustrated various applications of GTR associated with dental implants. At present, in the opinion of this author, the material of choice for these procedures is GTAM. Other barriers are currently available while still more are under development. It is not within the scope of this article to include a comprehensive discussion of all available materials but it is noteworthy that resorbable membranes such as GUIDOR (Butler) show promise. At present the predictability of the various GTAM techniques discussed in this article, in the experience of the author are as follows: a) There is good predictability with immediate implant placement in extraction sockets. b) There is fairly good predictability regenerating localized osseous ridge deformities prior to implant placement. c) There is fairly good predictability regenerating new bone at dehiscences and/or fenestration defects that are associated around initial implant placements. d) There is poorer predictability regenerating new bone i.e. "re-osseointegration" around "ailing" i.e. contaminated implants.

Adult↗
PubMed2006

The use of a dental implant as an abutment in three unit implant-tooth supported fixed partial denture: a case report and 32 month follow-up.

The combined use of dental implants and teeth as abutments in fixed partial dentures may offer advantages to both patients and practitioners in certain clinical situations. An implant-tooth retained prosthesis may reduce surgical intervention and cost to the patient. It may also mean that anatomical restrictions to the provision of an implant-retained fixed prosthesis may be overcome. In this case report, the steps in provision of a three unit implant-to-tooth fixed partial denture are described and the treatment planning and prognosis of a restoration of this type are discussed.

Dental Abutments↗
PubMedDate not supplied

Two dental implants designed for immediate loading: a finite element analysis.

PURPOSE: The aim of this study was to evaluate by finite element analysis the influence of the design of 3 different dental implants on micromovements, cervical shearing stress intensity, and stress distribution after occlusal loading. MATERIALS AND METHODS: The first investigated implant was a classical cylinder, the second was reinforced by 2 bicortical locking pins, and the third was an expanding dental implant. The parameters analyzed were the implant's geometry, the quality of the cancellous bone, and the orientation of occlusal loading. RESULTS: It was found that initial stability of the locking pin implant was greater than the initial stability of the other investigated implant designs, regardless of the quality of cancellous bone and orientation of occlusal loading; in low-rigidity cancellous bone, under a horizontal load (500 N), decreasing displacement compared to those of the other investigated implants was 16 microm. The apical expansion and locking pin implants exhibited favorable behavior regarding the distribution and intensity of cervical shearing stresses; in low-rigidity cancellous bone, under horizontal load, decreasing cervical stresses compared with those of the cylindric implant were 10 MPa for the apical expansion implant and 150 MPa for the locking pin implant. DISCUSSION: For the cylindric implant, stresses were concentrated in the neck region; for the apical expansion implant, stresses were evenly distributed from the neck to the apex of the implant. For the locking pin implant, stresses around the neck were moderate and appeared concentrated around the pins. CONCLUSIONS: Initial stability of the pin implant was greater than that of the expanding implant, but the expanding implant showed the most favorable stress distribution.

Bite Force↗
PubMed1998

Evaluation of the Periotest as a diagnostic tool for dental implants.

The Periotest is examined as a possible replacement for outdated, inconsistent dental implant stability diagnosis tools. The Periotest has the advantage of offering reproducible findings by measuring the levels of subclinical mobility using an ultrasonically vibrating probe. The Periotest is successful in assessing the stability status of an implant, but it can detect the quantity of bony osseointegration only in terminal cases. Radiography proved to be a more sensitive method of determining pericervical bone loss; therefore, periapical radiographs in addition to the Periotest device were found to offer the most reliable assessment of an implant's status.

Alveolar Bone Loss↗
PubMed2000

The development of the ITI DENTAL IMPLANT SYSTEM. Part 2: 1998-2000: Steps into the next millennium.

In 1998 and 1999, the ITI DENTAL IMPLANT SYSTEM underwent its greatest modification since it came into existence. Prosthetic possibilities with regard to implant position transfer and master-cast manufacturing have been considerably enlarged by synOcta, surgical instruments have been improved in a multitude of ways and, by introducing SLA, the sand-blasted, large grit, acid-etched surface for oral implants which shortens time to loading by 50%, the ITI and Straumann have achieved a major breakthrough in surface technology.

Dental Abutments↗
PubMed1998

Guidelines for analysis and redesign of dental implants.

This article describes the simulation of the mechanical behavior of two types of endosseous-threaded dental implants and the development of design guidelines for such implants. Two- and three-dimensional representations, static and dynamic cyclic loads, different material models, axial loads, and loads directed at the occlusal angle are all used. A novel model of trabecular bone is used to incorporate fatigue effects. Directional material behavior, progressive bone loss, and partial osseointegration are also modeled. Bone support using muscle attachment is modeled using spring constraints as opposed to fixed constraints used in previous studies. The tapered thread design from Brånemark Inc. exhibited higher stress levels in bone than those observed in the parallel profile thread from BUD Medical Devices, Inc. The BUD implant distributes stresses more evenly. Studies examining 25%, 75%, and 100% osseointegration showed cortical bone carried most of the load with resulting overload leading to crestal bone loss. Plots of stress showed that with increasing crestal bone loss, the majority of the load was transferred directly to the weaker trabecular bone tissue. Finally, it was shown that with proper implant redesign, loads can be transferred more evenly to the implant. This also improves fatigue life of the bone.

Alveolar Process↗
PubMed2002

Mental nerve function after inferior alveolar nerve transposition for placement of dental implants.

BACKGROUND: One option for successful placement of dental implants in an atrophic posterior mandible without injury to the inferior alveolar nerve (IAN) is to transpose or lateralize the nerve. This procedure carries the risk of numbness along the distribution of the nerve, the complication that the procedure is undertaken to avoid in the first place. The purpose of the present study was to assess mental nerve function after transposition of the IAN. METHOD: We determined the outcomes of 20 IAN transposition procedures in 12 consecutive patients at the Queen Elizabeth II Health Sciences Centre in Halifax, Nova Scotia. The study included objective testing of sensory nerve function as well as subjective assessment by the participants. RESULTS: All subjects reported initial transient sensory disturbance. Objective testing after a minimum of 6 months revealed that, for each patient, affected sites had the same level of sensation as unoperated areas. Eighty percent of the patients said that the lower lip and chin felt normal. The others said that these structures did not feel exactly normal but that the difference was of no consequence. CLINICAL SIGNIFICANCE: It is concluded that IAN transposition can be safely and predictably performed with low risk to the mental nerve sensibility.

Dental Implantation, Endosseous↗
PubMed1990

Dental implant abutment resembling the two-phase tooth mobility.

Natural teeth and dental implants have differing degrees of mobility thus causing a potential biomechanical problem when connected by fixed bridgework. The clinical follow-up often discloses marginal bone loss around an implant neck probably due to high stress factors. An implant with a built-in compliance resembling the tooth mobility could be advantageous for stress distribution. With axial loading the proposed 'elastic'-test model accomplishes this demand. By means of theoretical and experimental studies this 'elastic'-test model is optimized and compared with a stiff implant-model. The results show a 20 times reduction of stress accumulation in bone with the 'elastic'-test model.

Biocompatible Materials↗
PubMedDate not supplied

Mechanical properties and biomechanical compatibility of porous titanium for dental implants.

Titanium powder with a granule diameter of 420-500 micron was prepared and porous titanium specimens were made from this powder. The mechanical properties of these specimens were examined. The compressive strength and low cyclic compressive fatigue strength were 182 and 40 MPa, respectively. Fractography was also observed by scanning electron microscopy. Typical fatigue characteristics of the bonding areas of the powder were observed. In addition, porous-titanium-coated dental implants with pure titanium cores were prepared. The compressive strength of the material used was 230 MPa, fatigue strength not being improved. Biomechanical stress calculations using the finite element method were made using a model that employed the use of the material implanted in alveolar bone. Shear stress at the implant-bone interface as well as compressive stress concentrations in the bone was calculated. The most suitable elastic modulus for the dental implant was then estimated from these calculations. Finally, based on these results, the use of porous titanium for dental implants was assessed.

Chemical Phenomena↗
PubMed2006

Dental implants placement in conjunction with osteotome sinus floor elevation: a 12-year life-table analysis from a prospective study on 588 ITI implants.

OBJECTIVES: The purpose of this prospective study was to evaluate the clinical success of placing ITI dental implants in the posterior maxilla using the osteotome technique. MATERIAL AND METHODS: All implants were placed following a one-stage protocol (elevating the sinus floor and placing the implant at the same time). Five hundred and eighty-eight implants were placed in 323 consecutive patients with a residual vertical height of bone under the sinus ranging from 6 to 9 mm. The mean observation follow-up period was 59.7 months (with a range of 12-144 months). This prospective study not only calculated the 12-year cumulative survival and success rates for 588 implants by life-table analysis but also the cumulative success rates for implant subgroups divided per implant length and the percentage of sinus membrane perforation were evaluated. RESULTS: The 12-year cumulative survival and success rates were 94.8% and 90.8%, respectively. The analysis of implant subgroups showed slightly more favourable cumulative success rates for 12 mm long implants (93.4%) compared with 10 and 8 mm long implants (90.5% and 88.9%, respectively). During the study period, only 13 perforations of the Schneiderian membrane were detected with a perforation rate of 2.2% (13 perforations/601 treated sites). Ten perforations out of 13 were caused during the first half of the study period and of these, seven were detected during the first 3 years of this prospective study. CONCLUSION: Based on the results and within the limits of the present study, it can be concluded that ITI implant placement in conjunction with osteotome sinus floor elevation represents a safe modality of treating the posterior maxilla in areas with reduced bone height subjacent to the sinus as survival and success rates were maintained above 90% for a mean observation period of approximately 60 months. Shorter implants (8 mm implants) did not significantly fail more than longer ones (10 and 12 mm implants): the differences were small compared with the number of events; hence, no statistical conclusion could be drawn. But, from the clinical point of view, the predictable use of short implants in conjunction with osteotome sinus floor elevation may reduce the indication for complex invasive procedures like sinus lift and bone grafting procedures.

Adult↗
PubMed1996

Evaluation of the surface integrity of hydroxyapatite-coated threaded dental implants after insertion.

The surface characteristics and changes of hydroxyapatite-coated threaded dental implants after insertion into bone (veal calf ribs) with similar cortical and medullary characteristics to the human maxilla and posterior mandible (type III or IV bone) were studied. Hydroxyapatite-coated threaded implants from six vendors were coded A, B, C, D, E, and F. Four implants from each vendor were subjected to conventional placement following the manufacturer's instructions, placement without tapping of the osteotomy site, or evaluated as controls. The implants were recovered atraumatically and examined by scanning electron microscopy at x 35 and x 100 magnification. Photomicrographs were examined and graded by two independent examiners. Statistically significant differences were found using Kruskal-Wallis ANOVA and Wilcoxon Signed Ranks tests in surface integrity between conventional and nontapped treatment for groups C and D; between conventional placement and controls for groups A, B, and F; between nontapped placement and controls for groups A, B, C, D, and E; and among the manufacturers with respect to conventional placement for groups A, B, and E as compared with the other groups (P < 0.05). These findings suggest that surface changes of hydroxyapatite-coated threaded implants may occur during placement, particularly in undersized and untapped osteotomy sites. The changes could result in differences in integration and performance of some implant systems.

Analysis of Variance↗
PubMed2003

On the effects of cyclic transversal forces on osseointegrated dental implants: experimental and finite element shakedown analyses.

This paper is concerned with the mechanical strength of fixed osseointegrated dental implants subjected to cyclic external loads, applied mainly in a direction orthogonal to their axis. Such a loading condition, seen as a basic design action for the implant, has been given little attention so far. Experimental results and numerical simulations, performed on two- and three-dimensional Finite Element models, are discussed. The shakedown theory is used to show that a common implant design (threaded fixture-abutment-connection screw) is susceptible of low-cycle fatigue failure under loading conditions well within the working range, even if the same design is able to withstand loading of the same type, but applied monotonically, much in excess of the working values. The shakedown analyses give an indication of several possible failure modalities: the low-cycle fatigue either of the implant or of the connection screw, or the loosening of the connection screw itself. Experimental and numerical results are in good qualitative agreement, and both suggest that the issue of transversal cyclic loading on fixed dental implants should be carefully reconsidered in the design phase.

Bone Screws↗