Errors in radiographic assessment of marginal bone height around osseointegrated implants

Radiographic assessment of marginal bone height is included in longitudinal control of osseointegrated implants. Previous studies have revealed a mean annual loss of less than 0.1 mm. The purpose of the present study was by means of an experimental model to analyze the influence upon alveolar bone height measures around osseointegrated implants of buccolingual bone dimensions as well as angulations of fixture axis to central X-ray beam. Br?nemark titanium implants were inserted into acrylic test blocks simulating alveolar ridges of various widths. 0.2 mm steel wires visualized buccal and lingual bone margins. Standardized radiographs were obtained by stepwise variation of projection angles. Separation of the wire images varied from 0.1 mm (buccolingual width 5 mm and 1 degree angulation) to 4.8 mm (width 13 mm and angulation 20 degrees). In clinical cases distortion of buccal and lingual bone margins may result in overestimation of bone heights. The degree of overestimation is influenced by the buccolingual position of the fixture. Strict parallelism between fixture axes and film plane is essential to obtain valid results using single films.     

Estimating the validity of radiographic measurements of marginal bone height changes around osseointegrated implants.

The accuracy of determining marginal bone height changes around osseointegrated implants depends on the validity of comparing serial films and the reliability of the measurements. X-ray beam orientation changes can alter the validity of serial films. A human dry mandible containing a Br?nemark implant was irradiated +/- 12 degrees in the vertical plane at 1-degree intervals to the perpendicular to the long axis of the fixture. The thread width was recorded on both sides of each fixture image using a computer. Twenty-five randomized unclassified images were remeasured and the vertical angle of the x-ray beam was estimated from the previous measurements to test for validity of comparing images. The reliability of measurements with altered image magnification and penumbra were calculated. The reliability of 24 repeated thread width measurements was a SD of 0.01 mm. Of the 25 unknown beam angulations, 32 percent matched correctly, 20 percent +/- 1 degree, 16 percent +/- 2 degrees, or 68 percent < or = +/- 2 degrees. Alteration from a short to a long cone technique was estimated to produce magnification errors similar to the reliability SD of 0.01 mm. Similarly the penumbra varied from 0.057 mm to 0.032 mm with short to long cones using a 1.0-mm focal spot. With a 0.6-mm focal spot, the smallest penumbra of 0.19 mm was twice the measurement reliability. This method demonstrated x-ray beam angulation and validity for comparing serial films can be estimated for the extreme variations but not accurately for +9 to -6 degrees from a tangent to the fixture.(ABSTRACT TRUNCATED AT 250 WORDS)     

Method for radiographic assessment of alveolar bone level at endosseous implants and abutment teeth

Abstract— A radiographic method expressing the alveolar bone level in absolute figures is presented. By means of a calibrated measuring radiographic film fixed to a magnifying viewer, alveolar bone levels were determined directly on intraoral periodic "identical" radiographs. A polyether impression was made for fixation of the filmholder in order to obtain reproducible radiographs. The method was applied to assess changes in the alveolar bone level at endosseous implants and abutment teeth. Radiographs af 23 endosseous implants and 21 abutment teeth from nine patients were examined and measurements of the alveolar bone level were perfarmed. The mean difference between double observations on the same exposure as well as on repeated exposures was about 0.2 mm (s.d. 0,17–0.32 mm). The uncertainty of the present radiographic method was mainly due to the measurement procedure, as the radiographic technique showed a high degree of reproducibility. The method is a simple and reliable technique for longitudinal investigations of changes in the alveolar bone level at endasseous implant and tooth abutments.     

A radiographic assessment of progressive loading on bone around single osseointegrated implants in the posterior maxilla

OBJECTIVES: The aim of this clinical study was to determine the effectiveness of progressive loading procedures on preserving crestal bone height and improving peri-implant bone density around maxillary implants restored with single premolar crowns by an accurate longitudinal radiographic assessment technique. MATERIALS AND METHODS: Twenty-three HA-coated, endosseous dental implants were placed in 20 subjects and permitted to heal for 5 months before surgical uncovering. The implants were randomly assigned to either an experimental or control group. Following a conventional healing period, the control group implants were restored with a metal ceramic crown and the experimental group implants underwent a progressive loading protocol. The experimental group was progressively loaded by increasing the height of the occlusal table in increments from a state of infraocclusion to full occlusion by adding acrylic resin to a heat-processed acrylic crown. The progressively loaded crowns were placed in infraocclusion for the first 2 months, light occlusion for the second 2 months, and full occlusion for the third 2 months. At this point, a metal ceramic crown replaced the acrylic crown. Standardized radiographs of each implant were made at the time of restoration, then after 2, 4, 6, 9, and 12 months of function. Digital image analysis and digital subtraction radiography were used to measure changes in crestal bone height and peri-implant bone density. RESULTS: The mean values of crestal bone height loss at 12 months were 0.2+/-0.27 mm for the progressively loaded implants and 0.59+/-0.27 for the conventionally loaded implants, and when tested with repeated-measure ANOVA across the time periods, the differences were statistically significant (P< or =0.05). The progressively loaded group showed a trend for higher bone density gain in the crestal area than the conventionally loaded group, but the conventionally loaded group showed a trend for higher bone density gain at the apex of the implants. CONCLUSION: The peri-implant bone around progressively loaded implants demonstrates less crestal bone loss than the bone around implants placed conventionally into full function. The peri-implant density measurements of the progressively loaded implants show continuous increase in peri-implant bone density by time.     

Radiographic control of fixture-abutment connection in Brånemark implant technique

Abstract— In the treatment with osseointegrated implants ad modum Brånemark a radiographic control of the fixture-abutment connection is recommended. The purpose of the present study was to analyze the possibilities of detecting incomplete connection by radiography using the recommended technique. In an experimental model the influence of film density, orientation of the fixture hexagon, angulation between film plane and fixture axis, leakage width, and partial connection were analyzed. Slits of 0.05 mm were detectable under optimum projection conditions. On the other hand, slits of 0.1 mm were obscured even at deviations of 5°. A number of factors, e.g. low density level and "unfavorable" orientation of the hexagon in relation to the X-ray beam, reduce the possibilities of detecting slits. It is concluded that in clinical cases a demonstration of incomplete fixture-abutment connection by the use of the recommended radiographic technique radiography to some extent is fortuitous, and that radiographic control has certain limitations.     

Effects of magnesium intake deficiency on bone metabolism and bone tissue around osseointegrated implants

Objectives: This study evaluated the effect of magnesium dietary deficiency on bone metabolism and bone tissue around implants with established osseointegration. Materials and methods: For this, 30 rats received an implant in the right tibial metaphysis. After 60 days for healing of the implants, the animals were divided into groups according to the diet received. Control group (CTL) received a standard diet with adequate magnesium content, while test group (Mg) received the same diet except for a 90% reduction of magnesium. The animals were sacrificed after 90 days for evaluation of calcium, magnesium, osteocalcin and parathyroid hormone (PTH) serum levels and the deoxypyridinoline (DPD) level in the urine. The effect of magnesium deficiency on skeletal bone tissue was evaluated by densitometry of the lumbar vertebrae, while the effect of bone tissue around titanium implants was evaluated by radiographic measurement of cortical bone thickness and bone density. The effect on biomechanical characteristics was verified by implant removal torque testing. Results: Magnesium dietary deficiency resulted in a decrease of the magnesium serum level and an increase of PTH and DPD levels (P≤0.05). The Mg group also presented a loss of systemic bone mass, decreased cortical bone thickness and lower values of removal torque of the implants (P≤0.01). Conclusions: The present study concluded that magnesium‐deficient diet had a negative influence on bone metabolism as well as on the bone tissue around the implants. To cite this article:
Belluci MM, Giro G, del Barrio RAL, Pereira RMR, Marcantonio E Jr, Orrico SRP. Effects of magnesium intake deficiency on bone metabolism and bone tissue around osseointegrated implants.

Clin. Oral Impl. Res. 22 , 2011; 716–721
doi: 10.1111/j.1600‐0501.2010.02046.x     

A comparison of methods to assess marginal bone height around endosseous implants

Abstract 3 methods of measurements of marginal bone level on intra-oral radiographs of endosseous implants are described: measurements with a computerized image analysis system, with a magnifying-glass and with a digital sliding gauge. The accuracy of each of these methods was investigated and compared. The intra- and inter-observer error analysis showed that determining the precise bone height on the image is responsible for a large standard deviation for each method. It is concluded that measurements with a digital sliding gauge are preferable because it is easy to put into practice, and in addition, accuracy matches the accuracy of the other methods.     

Marginal bone level around implants assessed in digital and film radiographs: in vivo study in the dog

Background: One of the objectives of postoperative radiographic examinations of implants is to evaluate the marginal bone height and its changes over time. Purpose: The purpose of this study was to assess the influence of digital image processing on measurements of the marginal bone level around implants. Material and Methods: Implants in beagle dogs, used to study the development of peri‐implantitis and subsequent healing following treatment, were monitored with conventional radiography and a digital image plate system. Five observers measured the distance between a reference point and the bone level. Measurements in conventional radiographs were made with the use of an x‐ray viewer (2X) and a magnifying lens (7X). For the digital images, the system's built‐in measuring function was used together with five image processing techniques: edge enhancement (matrixes set on 5 and 25), inverted grey scale, single color highlight, and color intensity mapping together with the brightness and contrast control. From the time of maximum breakdown and the end of the experiment, histologic values were available. Results: Differences between techniques and observers increased toward the end of the healing period. Measurements made at maximum breakdown did not differ significantly from the histologic value. Measurements made after healing all methods, except that using edge enhancement and a 25 × 25 kernel, differed significantly from the histologic value by underestimating the bone level. Conclusions: Measurements of bone level around implants from digital radiographs are as accurate and precise as those from film images. In particular cases, the use of specific image processing algorithms may improve both accuracy and precision. After healing, the histologic specimens showed an incomplete bone fill in the crater with a remaining thin layer of connective tissue in contact with the fixture, and in such situations, the morphology of the bone will give a more complicated diagnostic task.     

The effect of oestrogen and alendronate therapies on postmenopausal bone loss around osseointegrated titanium implants

Objectives: This study evaluated the influence of oestrogen deficiency and its therapies on bone tissue around osseointegrated implants. Methods: Implants were placed in 66 female rats tibiae. The animals were assigned into five groups: control (CTL), sham, ovariectomy (OVX), oestrogen (EST), and alendronate (ALE). While CTL was sacrificed 60 days after implant placement, other groups were subjected to ovariectomy or sham surgery according to group and euthanized after 90 days. Blood and urine samples were collected at sacrifice day for osteocalcin (OCN) and deoxypyridinoline (DPD) quantification. Densitometry of femur and lumbar vertebrae was performed in order to evaluate rats' skeletal impairment. Non‐decalcified sections were referred to fluorescent and light microscopy for analyses of mineral apposition rate (MAR), eroded and osteoclastic surfaces, bone‐to‐implant contact (BIC), and bone area fraction occupancy (BAFO). Results: Results from the OVX group showed significantly lower bone mineral density (BMD), BIC, BAFO, and MAR, while OCN, deoxipiridinoline, eroded surface and ostecoclastic surface were increased compared with the other groups of the study. ALE reduced OCN and DPD concentrations, MAR, osteoclastic and eroded surfaces, and no difference was in BIC and BAFO relative to SHAM. EST and CTL showed similar results to SHAM for measurements. Conclusions: Oestrogen deficiency exerted a negative influence on bone tissue around implants, while oestrogen replacement therapy and alendronate were effective against its effects. Although alendronate therapy maintained the quantity of bone around implants, studies evaluating bone turnover kinetics are warranted. To cite this article:
Giro G, Coelho PG, Pereira RMR, Jorgetti V, Marcantonio E Jr, Orrico SRP. The effect of oestrogen and alendronate therapies on postmenopausal bone loss around osseointegrated titanium implants.
Clin. Oral Impl. Res. 22 , 2011; 259–264.
doi: 10.1111/j.1600‐0501.2010.01989.x     

Impact of particulate deproteinized bovine bone mineral and porous titanium granules on early stability and osseointegration of dental implants in narrow marginal circumferential bone defects

The use of two particulate bone graft substitute materials in experimental narrow marginal peri-implant bone defects was investigated with respect to early bone healing and implant stability. Porous titanium granules, oxidized white porous titanium granules (WPTG), and demineralized bovine bone mineral (DBBM) were characterized in vitro, after which the two latter materials were tested in experimental peri-implant bone defects in six minipigs, with empty defects as control. After mandibular premolar extraction, the top 5 mm of the alveoli were widened to 6 mm in diameter, followed by the placement of six implants, three on each side, in each pig. Six weeks of healing was allowed. The WPTG showed better mechanical properties. No significant differences in resonance frequency analysis were found directly after compacting or healing, and similar quantities of defect bone formation were observed on micro-computed tomography for all groups. Histomorphometric analysis demonstrated a more coronal bone-to-implant contact in the DBBM group, which also displayed more defect bone fill as compared to the WPTG group. The better mechanical properties observed for WPTG appear of negligible relevance for the early stability and osseointegration of implants.     

Inter‐ and intraobserver variability in radiographic bone level assessment at Brånemark fixtures

The aim was to determine inter‐ and intraobserver variability in radiographic bone level assessments at Brånemark fixtures and to study the influence of various factors (radiographic density; projection geometry; jaw in which the fixtures were inserted; degree of bone loss; time after fixture loading; and number of radiographs of each fixture) on the variability. Intraoral radiographs from bridge connection and 1‐ and 3‐year check‐ups from 15 upper and 15 lower jaws (172 fixtures) were assessed by 6 observers. Measurements were taken from a reference point on the fixture to the marginal bone level, and some were repeated by all observers after 1 month. Results showed a small interobserver variation (0.14 mm) with the intraobserver variation (0.08 mm) as its largest component. The radiographic density and the degree of bone loss showed the strongest influence on the interobserver variation. The only variable with a significant effect on the intraobserver variation was the number of radiographs of each fixture. Calculated confidence values showed that measurement reliability can be improved by letting one observer or preferably more make several, independent readings, allowing for the demonstration of minor differences in bone height over time or between implant systems.     

Clinical probing and radiographic assessment in relation to the histologic bone level at oral implants in monkeys

Clinical probing level and radiographic bone level were compared to histologic bone level around screw type oral implants in 4 monkeys (Mucaca Fasciculavis). Two implants in each monkey retained a fixed partial prosthesis in supra‐occlusal contact with an antagonizing splint. These implants were brushed 1 x a week and subgingival cleaning was performed 1 x a month. Unloaded implants in the same monkeys were never cleaned and, additionally, a cotton cord was placed around these to promote plaque accumulation. After 18 months, intraoral radiographs of the implants were obtained and probing levels were recorded with a metal probe using a standardized force of 0.2 N (Vivacare TPS Probe) and again using a moderate, unstandardized pressure. Immediately afterwards the animals were sacrificed. Sections, approximately 50 fl thick, of the implants and surrounding tissue were cut. The average probing levels with unstandardized pressure were 1.1 mm and 3.9 mm coronal to the histologic bone levels for implants with plaque accumulation or excessive occlusal load, respectively. With standardized probing force, the difference between the probing levels and histologic bone levels were even larger. The radiographic bone levels were on average only 0.5 mm and 0.1 mm short of the histologic bone levels for the two groups of implants. Only the radiographic bone level revealed a statistically significant correlation with the histologic assessment.     

Factors affecting late fixture loss and marginal bone loss around teeth and dental implants

Background: The predictability and high success rate of implant treatment have averted attention from factors affecting fixture loss and bone loss around implants. Purpose: The goal of this study was to retrospectively evaluate late fixture loss and marginal bone loss around implants that have been in function for 5 years and to relate these findings to bone loss in the natural dentition. Materials and Methods: One hundred and forty‐three consecutively treated patients who had received an implantanchored fixed prosthesis and completed a 5‐year follow‐up were selected. Intraoral and panoramic radiographs were used to assess bone loss. Results: The bone loss was greater around remaining implants in patients who had lost implants after loading. No correlation was found between bone loss around implants and that around teeth. Only 2% of the fixtures were lost during 5 years of functional load. Most fixture losses occurred in the edentulous maxilla. Seven of the nine patients who lost fixtures were smokers. Conclusion: These findings show that patients who lost implants also lost more bone around the remaining implants. There was no correlation between bone loss around implants and that around teeth, indicating that different interacting mechanisms are involved.     

The effect of internal versus external abutment connection modes on crestal bone changes around dental implants: a radiographic analysis

Background: To the best of our knowledge, the influence of external versus internal implant–abutment connections on crestal bone remodeling has not been reported. The aim of the present study is to investigate the influence of the abutment connection on peri‐implant crestal bone levels (CBLs) using radiographic recordings. Methods: Radiographic recordings from 40 single‐tooth implants (20 external and 20 internal octagonal connections; one implant/patient) in 40 patients (15 males and 25 females; mean age: 54.3 years) were selected for analyses. The radiographic evaluation included the following: 1) linear bone change (LBC); 2) dimensional change (DC); and 3) angle between the implant and adjacent bone (AIB). Differences in LBC, DC, and AIB between implant placement and 1 year after loading for each system were evaluated using a paired t test. Comparison of LBC, DC, and AIB between systems at 1 year after loading was done using analysis of covariance. The significance level was set at P ≤0.05. Results: Radiographic CBLs (LBCs) were reduced at 1 year after loading compared to those at implant placement to reach statistical significance for the external connection (P = 0.000) but not the internal connection (P = 0.939). CBL changes were significantly greater for the external compared to the internal connection (P = 0.000). Similarly, the DC for the external connection was significantly greater compared to that for the internal connection (P = 0.004). Conclusion: Within the limitations of this study, the implant–abutment connection technology appears to have a significant impact on peri‐implant CBLs, with the external connection paralleled by a significant reduction of CBLs.     

Comparison of bone resorption at one-step and two-step mandibular endosseous implants in dogs

Abstract – Endosseous dental implants have been inserted into dog jaw bone following two different implantation principles. Using the two-step procedure, the implant is left submerged, covered by the mucoperiosteum for a healing period, before communication with the oral cavity is established. According to the one-step procedure, this communication is established peroperativcly. In order to estimate radiographically the degree of bone resorption following the two-step as compared to the one-step procedure, the former was used on the right and the latter on the left side of the mandible in two dogs. Periodic identical intraoral radiographs revealed bone resorption in the neck area of all implants. After a 1-yr period with bilateral bridges, the vertical resorption varied between 3 and 5 mm. No difference was found between the two methods concerning this bone resorption. The observation seems to be contrary to the general opinion on the matter, and pertinent investigations with the present model will be performed in a human material.