Effect of bone to implant contact percentage on bone remodelling surrounding a dental implant

Dental implants are an effective, safe and predictable solution for patients suffering from tooth loss, but implant placement changes the normal mechanical environment of the jawbone leading to bone density redistribution and ‘remodelling’, in order to adapt to the new environment. Many bone remodelling theories assume the presence of 100% contact between bone and implant, which is inconsistent with clinical reality. About 50–80% bone–implant contact is commonly seen with clinically successful implants. The influence of different percentages of bone–implant contact on bone remodelling has not been investigated adequately. This study aims to evaluate this influence using a newly proposed remodelling algorithm through a 2D finite element model. Four different degrees of bone–implant contact (25, 50, 75 and 100%) are considered and their influences on the density distribution of the jawbone are evaluated. The predicted results indicate that no matter what the initial percentage of bone–implant contact (25–100%), the final outcome is about 58–60% contact when an equilibrium state is reached by bone remodelling. The results are consistent with clinical observations and findings.     

Histologic comparison of a thermal dual-etched implant surface to machined,TPS, and HA surfaces: bone contact in vivo in rabbits

PURPOSE: To evaluate the bone contact percentage around a proprietary high-temperature dual-etched (DE) implant surface (Osseotite) versus implants with machined, hydroxyapatite (HA), and titanium plasma-sprayed (TPS) surfaces. MATERIALS AND METHODS: Each implant type was placed in rabbit tibiae of the same animal and assessed at 1 to 8 weeks. Histologic sections were prepared and analyzed histomorphometrically. RESULTS: The DE implant surface achieved higher levels of bone contact percentage than the other surfaces. This enhanced contact level was apparent by 3 weeks and seen at all time intervals except 2 weeks, at which machined exceeded the DE mean. In evaluating which surface outscored the others in each individual rabbit, there was a statistically significant confidence for the DE surface (P < .001). The other 3 surfaces failed to show significance, although the numeric scores for the TPS surfaces were below random expectations and the machined scores were slightly above. There was no correlation between degree of roughness and bone contact percentage. DISCUSSION: Arbitrarily roughening the implant surface may not result in a large change in bone conductivity. The specific texture of the DE process yielded more contact, possibly as the result of better fibrin clot retention and growth factor enhancement. CONCLUSIONS: There was no advantage demonstrated in this model to an HA surface over titanium. The bone contact to the rough HA surface scored similarly to that for the TPS surface of similar roughness, and well below that for the DE titanium surface. The DE surface appeared to have an advantage in bone contact percentage, particularly in early healing in a rabbit tibia model.     

Bone-implant contact and bone quality: evaluation of expected and actual bone contact on machined and osseotite implant surfaces

This article introduces a new technique using histomorphometrics to estimate the extent of bone-to-implant contact that might be expected on an implant surface in relation to the quality of the surrounding bone. Two implant surfaces, one machined and one Osseotite, were compared on the same implant in the same patient Eleven of these custom-made 2-mm-diameter implants were placed in the posterior maxilla and allowed to integrate. After 6 months of nonloaded healing, implants were trephined with surrounding bone tissue and prepared into histologic sections. Digitized images were analyzed at 50x magnification with image-analysis software. Bone surface area was calculated over the entire microscopic field, and the actual bone-to-implant contact for each implant surface was measured. The expected bone-to-implant contact was calculated by superimposing the profile of the implant threads on the bone image a small increment (0.15, 0.5, or 1.0 mm) from the actual implant site and counting the linear amount of bone that would be in contact with the implant surface. The actual bone-to-implant contact for Osseotite was greater than its expected bone-to-implant contact, whereas the actual bone-to-implant contact for the machined surface was mostly lower than the expected values. Thus, the Osseotite surface appears to exert a positive effect on the amount of bone approaching the implant surface and can be described as conductive, while the machined surface is nonconductive. This technique may serve to predict the clinical success that the Osseotite surface will demonstrate in poor-quality bone.     

Vertical mandibular alveolar bone distraction and dental implant placement: a case report

Extensive bone defects complicate the adequate placement of dental implants and the required angulation. In such cases, alveolar-ridge augmentation techniques such as guided bone regeneration, particulate or block grafting, and alveolar bone distraction are needed. The present study describes a case in which a large vertical bone defect in the anterior mandibular zone was corrected via vertical alveolar bone distraction. Six dental implants were posteriorly placed for implant-supported restoration of the mandible, with early implant loading. The clinical and radiologic control showed good implant and soft tissue conditions 12 months later.     

The primary stability of two dental implant systems in low-density bone

Primary stability in low-density bone is crucial for the long-term success of implants. Tapered implants have shown particularly favourable properties under such conditions. The aim of this study was to compare the primary stability of tapered titanium and novel cylindrical zirconia dental implant systems in low-density bone. Fifty implants (25 tapered, 25 cylindrical) were placed in the anterior maxillary bone of cadavers meeting the criteria of low-density bone. The maximum insertion (ITV) and removal (RTV) torque values were recorded, and the implant stability quotients (ISQ) determined. To establish the isolated influence of cancellous bone on primary stability, the implantation procedure was performed in standardized low-density polyurethane foam bone blocks (cancellous bone model) using the same procedure. The primary stability parameters of both implant types showed significant positive correlations with bone density (Hounsfield units) and cortical thickness. In the cadaver, the cylindrical zirconia implants showed a significantly higher mean ISQ when compared to the tapered titanium implants (50.58 vs 37.26; P < 0.001). Pearson analysis showed significant positive correlations between ITV and ISQ (P = 0.016) and between RTV and ISQ (P = 0.035) for the cylindrical zirconia implants; no such correlations were observed for the tapered titanium implants. Within the limitations of this study, the results indicate that cylindrical zirconia implants represent a comparable viable treatment option to tapered titanium implants in terms of primary implant stability in low-density human bone.     

Force required to luxate a newly placed dental implant in bone: an in vitro pilot study

Immediate loading of newly placed dental implants is a consideration when attempting to meet patients' demands. However, immediate loading may induce implant failure to osseointegrate, particularly in the case of a patient who can generate a biting force that can reach approximately 1300 Newtons (N) in the posterior jaws. The range of biting forces that prevent osseointegration of newly placed implants is currently unknown. However, it is suspected that osseointegration may fail if an implant is luxated in bone more than 50 microm, in which case fibrous tissue will be formed instead of bone. This pilot study was focused on finding the amount of horizontal off-axial force required to move a nonosseointegrated 4.3 x 13-mm implant 50 microm. The initial data show that the amount of horizontal force required to displace such an implant by 50 microm was on the order of 150 N. Assuming that the angle between the direction of the biting force and the vertical lies between 0 degrees and 20 degrees, our data show that a 4.3 x 13-mm implant may fail to osseointegrate for biting forces that are as low as 440 N. One implication of our study is that implants having smaller diameters may move and fail to osseointegrate for even lower biting forces.     

Focal osteoporotic hematopoietic bone marrow defect formation around a dental implant: a case report

Focal osteoporotic bone marrow defects usually appear as asymptomatic radioluencies in the edentulous posterior mandible of middle-aged women. The exact causative factor in the majority of focal osteoporotic bone marrow defects is still unknown. Because of their radiological similarity with many intraosseous lesions, accurate diagnosis is possible only with histopathological examination. A focal osteoporotic bone marrow defect that occurred 2 years postoperatively apical to an implant is presented with clinical, radiographic, and histopathologic features. According to the literature scan, this is the first case report of this phenomenon caused by a dental implant. Int J Oral Maxillofac Implants 2011;26:e1-e4.     

Increased bone contact to a calcium-incorporated oxidized commercially pure titanium implant: an in-vivo study in rabbits

The aim of this study was to evaluate the bone response to an oxidized titanium implant (Ox) and a calcium-incorporated oxidized titanium implant (Ca). A blasted titanium implant (Bl) was used as control. The implants were topographically characterized using an optical interferometer and placed: one in each distal femoral metaphysis and two in each proximal tibial metaphysis in rabbits. The rabbits were killed 12 weeks after implant insertion, and the implants and their surrounding tissues were removed en bloc for histomorphometrical evaluations. Topographical evaluation revealed three different surfaces: average height deviation (S(a), microm) values for Ca:Ox:Bl implants were 0.3:0.6:0.9, developed surface area ratios (%) 17:44:31, number of summits per microm(2) 208:136:118, and core fluid retention index values 1.33:1.33:1.38. The mean percentages of bone contact to the implants placed in the tibia (Ca:Ox:Bl) were 47:30:34 and to the implants placed in the femur (Ca:Ox) 32:20. The mean percentages of surrounding bone area for the implants placed in the tibia were 40:47:37 and for the implants placed in the femur 43:46. A significant increase in bone contact was found for smooth (S(a) <0.5 microm) but more densely peaked calcium-incorporated oxidized implants when compared to slightly rougher (S(a)=0.5-1.0 microm) oxidized or blasted implants.     

Microbial community composition on modified dental implant surfaces: an in vivo study

Purpose: The aim of the present in vivo study was to examine alterations of the microbial community structure in biofilms on different dental implant surfaces over the time. Materials and Methods: Zirconium nitride-coated glass (ZrN-glass) and ZrN-coated polished titanium (ZrN-Ti) disks were used as substrates and polished titanium (Ti-pol) was used as a control. The specimens were mounted on removable intraoral splints in one adult. After 24 hours and 14 days of intraoral exposure, the microbial biofilms were analyzed by generating 16S rRNA gene clone libraries. Results: ZrN coating of a Ti surface altered the microbial composition early on (24 hours), with a tendency to augment Lactobacillus-related phylotypes later. Long-term exposure (14 days) of dental implant surfaces to microbes resulted in a significantly different composition of the biofilm on all three tested surfaces. Conclusions: This preliminary study showed that a ZrN-Ti disk surface harbors a significantly different microbial composition from a polished Ti surface. Further improvement of ZrN physical vapor deposition coatings might help to influence the adhesion of bacteria that are less pathogenic, thereby reducing the risk of peri-implantitis.     

Trauma to an osseointegrated anterior dental implant: a case report

Abstract –  Single tooth implant systems have been shown to offer a safe and highly predictable option for the replacement of anterior teeth. There is however, a paucity of evidence on the result of trauma to single tooth implant systems, particularly in the vulnerable anterior maxillary area. This article presents a report on the outcome of a traumatic incident to an osseointegrated single tooth implant.     

Augmentation in two stages of atrophic alveolar bone prior to dental rehabilitation: a case report

AIM: The aim of this report is to describe a significantly deficient case of alveolar bone that was managed by alveolar bone augmentation using a technique of distraction osteogensis and onlay bone grafting prior to dental implant placement. BACKGROUND: Injury to the teeth and alveolar ridge of the maxillary anterior region can cause a severe alveolar ridge deficiency resulting in ridge atrophy and maxillary retrognathism. The loss of these teeth and alveolar bone together with fibrotic scar formation can result in adverse changes of the interarch space, occlusal plane, arch relationship, and arch form which complicates rehabilitation and can compromise the esthetic outcome. While implant dentistry has become a new paradigm in oral reconstruction and replacement of missing teeth, ideal implant positioning can be compromised by inadequate alveolar bone in terms of bone height, width, and quality of the bone itself. Correction of osseous deficiencies with ridge augmentation allows ideal implant placement and creates a more natural soft tissue profile which influences crown anatomy and esthetics. REPORT: A 20-year-old female presented with a complaint of poor esthetics resulting from oral injuries incurred in a traffic accident six years previously. In addition to a mandibular parasymphyseal fracture, five maxillary anterior teeth and the most of the alveolar ridge were lost. Clinical examination revealed severe loss of bone in the maxillary anterior region, an absence of a labial sulcus, loss of upper lip support, and a slight over eruption of the mandibular anterior teeth. In preparation for dental implants a distraction osteogenesis surgical procedure was done to lengthen the height of the alveolar ridge. After a three-month healing period, the width of the residual ridge was found to be insufficient for implant placement. To correct this deficiency, a bone graft of a cortiocancellous block was harvested from the chin and fixed to the labial aspect of the ridge. To facilitate revascularization, small perforations were made in the cortical bone of the alveolar ridge at the recipient site before cancellous bone retrieved from the donor site was gently placed between the bone block and the ridge. The patient was then appropriately medicated and healing was uneventful. After three months, the width of the residual ridge was assessed to be adequate for endosseous implants. SUMMARY: The clinical result reported here has shown several procedures may be necessary for the rehabilitation of a trauma patient. Distraction osteogenesis per se may not always satisfactorily improve the anatomical alveolar anatomy but it has advantages over other methods of augmentation. It can improve the height and also expand the soft tissue for further bone grafting. Augmentation of the alveolar bone with an onlay bone graft often provides the desired gain of bone, allows for the ideal placement of dental implants, and improves any discrepancy between the upper and lower arches.     

Loading of a single implant in simulated bone

This study investigated the effect of occlusal design on the strain developed in simulated bone of implant-supported single crown models. Triaxial strain gauges were attached at the cervical area of each model. Occlusal design, load location, and magnitude were examined to determine the maximum axial principal strains (Μó) of four occlusal designs: 30-degree cusp inclination with 4- and 6-mm occlusal table dimensions and a 10-degree cusp inclination with 4- and 6-mm occlusal table dimensions. Statistical differences were found for peak average maximum principal strains between each occlusal design when the applied load was directed along the central fossa and 2 mm buccal to the central fossa along the inclined plane, with strain gauges attached at the cervicobuccal (P < .001) and cervicolingual (P ? .001) aspects. In all loading conditions, the 30-degree cusp inclination and 6-mm occlusal table dimension consistently presented the largest strains compared with the other occlusal designs. A reduced cusp inclination and occlusal table dimension effectively reduced experimental bone strain on implant-supported single crowns. The occlusal table dimension appeared to have a relatively more important role than cusp inclination.     

Experimental study of bone growth around a dental implant after Surgibone grafting

Histologic and histomorphometric results of bone growth around titanium alloy screw-type implants after Surgibone grafting in New Zealand white rabbits are presented. At 21 days, new bone was formed along the surface of the implant. At 84 days, newly formed bone replaced almost all of the trabecular bone of the graft and reached the shoulder level of the implant. There was a higher percentage of host bone area at 84 days than at any of the earlier experimental periods (P < .01). The average mineral apposition rates ranged from 1.82 to 2.35 microns/day in original bone and 2.55 to 2.80 microns/day in newly formed bone. The results suggest that Surgibone grafting in combination with dental implants can be used to increase the height of the recipient bone and therefore aid in the fixation of the implant in this animal model.