Right dorsal colon ultrasonography in normal adult ponies and miniature horses.

The aim of this study was to determine the normal location, wall thickness and motility of the right dorsal colon in adult ponies and miniature horses. The abdominal ultrasonography examination was performed in a study group consisting of 23 ponies and miniature horses and in a control group comprising ten Thoroughbred horses. The procedure was performed in unsedated standing animals. The location and the thickness of the right dorsal colonic wall was examined on the right side of the abdomen between the 10th and the 14th intercostal space. The contractility was recorded in the 12th intercostal space. A comparative analysis between the study group and control group was carried out using the Student's t-test. Pearson's linear correlation coefficient was used to calculate the correlation between the thickness of the colonic wall as well as the number of peristaltic movements and age, wither height and body mass of the animals. The right dorsal colon was identified in all the horses in the 12th intercostal space. In all the intercostal spaces the mean ± standard deviation (SD) wall thickness of the right dorsal colon was 0.27 ± 0.03 cm in the horses from the study group and 0.37 ± 0.03 cm in the control horses. The mean number of peristaltic contractions was 4.05 ± 1.07 per minute in the animals from the study group and 1.7 ± 0.46 contractions per minute in the control group. The values of the ultrasonographic wall thickness and peristaltic motility in small breed horses in the present study were different from the values obtained for large breed horses. The study also found that the right dorsal colon in small breed horses is physiologically located in the 12th intercostal space. This suggests that different reference values should be used in small horse breeds when performing an ultrasound examination.

Implementing systematic review techniques in chemical risk assessment: Challenges, opportunities and recommendations.

Systematic review (SR) is a rigorous, protocol-driven approach designed to minimise error and bias when summarising the body of research evidence relevant to a specific scientific question. Taking as a comparator the use of SR in synthesising research in healthcare, we argue that SR methods could also pave the way for a "step change" in the transparency, objectivity and communication of chemical risk assessments (CRA) in Europe and elsewhere. We suggest that current controversies around the safety of certain chemicals are partly due to limitations in current CRA procedures which have contributed to ambiguity about the health risks posed by these substances. We present an overview of how SR methods can be applied to the assessment of risks from chemicals, and indicate how challenges in adapting SR methods from healthcare research to the CRA context might be overcome. Regarding the latter, we report the outcomes from a workshop exploring how to increase uptake of SR methods, attended by experts representing a wide range of fields related to chemical toxicology, risk analysis and SR. Priorities which were identified include: the conduct of CRA-focused prototype SRs; the development of a recognised standard of reporting and conduct for SRs in toxicology and CRA; and establishing a network to facilitate research, communication and training in SR methods. We see this paper as a milestone in the creation of a research climate that fosters communication between experts in CRA and SR and facilitates wider uptake of SR methods into CRA.

Meta-analysis on occupational exposure to pesticides--neurobehavioral impact and dose-response relationships.

While the health impact of high exposures to pesticides is acknowledged, the impact of chronic exposures in the absence of acute poisonings is controversial. A systematic analysis of dose-response relationships is still missing. Its absence may provoke alternative explanations for altered performances. Consequently, opportunities for health prevention in the occupational and environmental field may be missed. Objectives were (1) quantification of the neurotoxic impact of pesticides by an analysis of functional alterations in workers measured by neuropsychological performance tests, (2) estimates of dose-response relationships on the basis of exposure duration, and (3) exploration of susceptible subgroups. The meta-analysis employed a random effects model to obtain overall effects for individual performance tests. Twenty-two studies with a total of 1758 exposed and 1260 reference individuals met the inclusion criteria. At least three independent outcomes were available for twenty-six performance variables. Significant performance effects were shown in adults and referred to both cognitive and motor performances. Effect sizes ranging from dRE=-0.14 to dRE=-0.67 showed consistent outcomes for memory and attention. Relationships between effect sizes and exposure duration were indicated for individual performance variables and the total of measured performances. Studies on adolescents had to be analyzed separately due to numerous outliers. The large variation among outcomes hampered the analysis of the susceptibility in this group, while data on female workers was too scant for the analysis. Relationships exist between the impact of pesticides on performances and exposure duration. A change in test paradigms would help to decipher the impact more specifically. The use of biomarkers appropriate for lower exposures would allow a better prevention of neurotoxic effects due to occupational and environmental exposure. Intervention studies in adolescents seem warranted to specify their risk.

Toward better research practice--shortcomings decreasing the significance of epidemiological studies in the toxicological field.

Neurobehavioral studies do not always gain the impact they should have, neither in the scientific nor in the regulatory field of neurotoxicology. Among others, shortcomings and inconsistencies across epidemiological studies may contribute to this situation. Examples were compiled to increase awareness of obstacles for conclusions. Meta-analyses were exploited since they sometimes allow the detection of deficits that are not obvious from individual studies. Exposure assessment, performance measures, and confounding were scrutinized among 98 primary studies included in meta-analyses on mercury, solvents, manganese and pesticides. Inconsistent and hardly comparable markers of exposure were found; figures, units or sampling periods were not always provided. The contribution of test materials to differences in test outcomes across studies could sometimes not be evaluated due to the insufficient description of the employed tests. Hypotheses for the selection of performance variables often remained undisclosed. Matching procedures prevailed with respect to the confounder age; the comparability of groups with respect to intelligence and gender remained more elusive. 8% and 16% of the studies did not even mention confounding from intelligence and gender, respectively. Only one third of the studies provided adjusted means for group comparisons; the proportion was slightly larger for studies published 2000-2010. While 50% of the studies considered confounders for their dose-response assessment, only 29% reported results for the total of test variables. The outlined deficits impede, among others, the assessment of exposure-effect relationships and confounding across studies; thereby they limit the use of the studies for toxicological risk assessment and future prevention. Some shortcomings also impede a deeper insight into the mechanisms of toxicity: tests like the Digit Symbol show that something is affected, but not what is affected. Thorough description of measures employed is among the first consequences from the data. The consideration of mechanistic insights from research on animals and neurobiology may further help to increase the significance of epidemiological studies.

The neurobehavioral impact of manganese: results and challenges obtained by a meta-analysis of individual participant data.

Results from a meta-analysis of aggregated data provoked a new analysis using individual data on the neuropsychological performance of occupationally exposed workers. Data from eight studies examining 579 exposed and 433 reference participants were included, 28 performance variables analyzed. The performance scores were adjusted for well-known individual-level covariates; the influence of possible, but unknown study-level covariates was attenuated by means of a z-normalization. Associations between performance and exposure were estimated by ANOVAs and ANCOVAs, the latter representing multi-level models. Four cognitive and motor performance variables each indicated significantly lower performances of exposed individuals when confounding was considered; slowed motor performances and deficits in attention and short-term memory were found. Performance on a single test was significantly related to the biomarker manganese in blood. The outcomes on susceptibility were weak. The slowing of responses was the most distinct feature of performances of exposed workers. It remains unclear, whether this result is related to the employed tests or provides important information about early stages of the neurotoxic impairment. More specific cognitive tests need to be employed to answer this question. The lack of dose-response relationships was related to features of the biomarker: it does not reflect the Mn in brain responsible for changes in performances.

Occupational exposure to neurotoxic substances in Asian countries - challenges and approaches.

The fact that a conference on neurotoxicity was held in China triggered the idea to provide an insight into occupational diseases, their development and the approaches to investigate them in Asian countries. A historical review, a meta-analysis, and studies on humans and animals provide impressions on past and current problems. The Korean example showed that each newly introduced industry is accompanied by its own problems as regards occupational diseases. Mercury and carbon disulfide were of importance in the beginning, whereas solvents and manganese became important later. Outbreaks of diseases were important reasons to guide both the public and the governmental attention to prevention and allowed within a relatively short time considerable progress. As the example on the replacement of 2-bromopropane by 1-bromopropane showed, also the introduction of chemicals that are more beneficial for the environment may result in additional occupational risks. A lower mutagenicity of 1-bromopopane was shown to be associated with a greater neurotoxicity in Japanese studies. Although occupational health and diseases are commonly related to adults, child workers exposed to solvents were examined in a Lebanese study. The study started outlining the health hazards in young workers because they might be at a much greater risk due to the not yet completed maturation of their nervous system. That some occupational diseases are not yet a focus of prevention was shown by the study on pesticides. If at all, the serious health consequences resulting from excessive exposure were investigated. Research enabling precautionary actions was not available from the international literature. Despite globalization the knowledge on occupational diseases is not yet "globalized" and each country obviously undergoes its own development triggered by local experiences. Economic development that requires a healthy workforce, but also public interest that challenges governmental regulations further efforts on the prevention of occupational diseases. The paper reflects a summary of the talks presented at the symposium "Occupational Neurotoxicities in Asian Countries" as part of the 11th International Symposium on Neurobehavioral Methods and Effects in Occupational and Environmental Health.

Statistical means to enhance the comparability of data within a pooled analysis of individual data in neurobehavioral toxicology.

Meta-analyses of individual participant data (IPD) provide important contributions to toxicological risk assessments. However, comparability of individual data cannot be taken for granted when information from different studies has to be summarized. By means of statistical standardization approaches the comparability of data might be increased. An analysis of individual data on the neurobehavioral impact of manganese (Mn) exemplifies challenges and effects of a multilevel statistical procedure. Confounding from individual-level and study-level covariates was shown by analyses of variance, but could be reduced by linear regressions and z-normalization using data of the respective control groups. Fixed models that were used to estimate the impact of the neurotoxic exposure, provided evidence that the employed procedures, especially the z-normalization, effectively reduced variance that was unrelated to the neurotoxic exposure. Even after this statistical treatment the fixed effect models revealed differences among studies that did not seem to be exhaustively explicable by concentration differences obvious from the Mn biomarker at hand. IPD studies using confounded endpoints as effects markers can be reasonably summarized when appropriate statistical operations are employed. For the data at hand the proposed normalization allowed new insights into exposure-effect relationships, in general it appears appropriate to investigate the effect of the independent variable more closely.

Performance alterations associated with occupational exposure to manganese--a meta-analysis.

The review aimed at quantifying the evidence of performance effects resulting from occupational exposure to manganese. Epidemiological studies published between 1987 and 2008 were analyzed. The approach was based on the meta-analytical method of effect size estimates and sought to contribute to the following issues: (1) identification of the affected functions; (2) identification of sensitive neuropsychological tests; (3) analyses of exposure-effect relationships. Thirteen studies examining 958 exposed and 815 unexposed workers were included in the meta-analysis. Mean concentrations of inhalable manganese ranged from 0.05 to 1.59 mg/m(3), mean concentrations of manganese in whole blood ranged from 8.1 to 48.4 microg/L. Nineteen neuropsychological performance variables were analyzed as they were included in at least three of the identified studies. Apart from two outcomes, the overall effects displayed a negative impact of manganese on performance. Significant overall effects were obtained for six test variables; their size ranged from d=-0.23 to -0.36. Four of the variables measured motor speed and two of them speed of information processing. The analysis of exposure-effect relationships showed that larger effect sizes were more consistently associated with higher concentrations of inhalable manganese than with manganese in blood. The evidence of cognitive and motor performance effects is in accordance with the knowledge about accumulation of manganese in the basal ganglia and the effect of manganese on the neurotransmitter dopamine. Inconsistencies in the relationship between effect sizes and the biomarker manganese in blood were discussed in the context of results indicating that the biomarker might not be sufficiently meaningful for the neurobehavioral alterations. Simple motor performance tests with a distinct speed component seem to be highly recommendable for further studies, because they seem to be appropriate for measuring manganese-related changes, seem to provide homogenous results and their outcomes show consistent relations to exposure. The rigorous quantitative approach was especially appropriate for revealing exposure-effect relationships, but information about individual cumulative exposure would enhance the potential for risk assessment of manganese.

The impact of solvent mixtures on neurobehavioral performance: conclusions from epidemiological data.

The review of epidemiological studies investigating the neurobehavioral effects of occupational exposure to solvent mixtures sought to contribute to the following issues: (1) Identification of affected cognitive and motor functions. (2) Identification of sensitive neuropsychological tests. (3) Analysis of exposure-effect relationships. The approach was based on the meta-analytical method of effect size estimates. Fifty-three groups from occupational studies were included in the meta-analysis. Forty-eight neuropsychological performance variables could be analyzed as they were included in at least three studies. Seventeen articles provided detailed information on the constituents of mixtures, thereby enabling the computation of an exposure index that allowed the comparison of different mixtures. Significant negative effect sizes were obtained for 12 test variables measuring attention, memory, motor performance and constructional abilities. The greatest proportion of lower performance scores in the exposed groups was shown by different tests of attention: significant effect sizes between d=-0.16 and -0.46 were calculated. Tests of cognitive processing speed, response alternation and inhibition seemed to be sensitive tools for the detection of poorer performance. Exposure-effect relationships were mainly characterized by inconsistent patterns. Crude and inappropriately calculated exposure measures were blamed for this outcome. A healthy worker effect was suggested more consistently: studies examining groups with longer exposure duration obtained smaller effect sizes. Indications of confounding were observed; however, they did not seem sufficient to question consistent effect size patterns. Paying greater attention to the measurement of exposure and including measures of confounding is advisable for future studies and would enhance the explanatory power of cross-sectional studies and meta-analyses.

Occupational aluminum exposure: evidence in support of its neurobehavioral impact.

Aluminum is a metal with known neurotoxic properties which are linked to encephalopathy and neurodegenerative diseases. The objectives of the current meta-analysis study were: (1) to summarize neurobehavioral data obtained by epidemiological studies in occupational settings and (2) to analyze confounding within these data. The meta-analysis was based on estimates of effect sizes. Overall effect sizes were obtained by application of a random effects model. The final sample consisted of nine studies examining 449 exposed and 315 control subjects. The mean urinary aluminum concentrations in the exposed groups ranged from 13 to 133 microg/l. Six neuropsychological tests, which yielded 10 performance variables, were analyzed. Nine overall effect sizes indicated an inferior performance for the exposed group. A significant overall effect size (d(RE)=-0.43) was obtained for the digit symbol test measuring speed-related components of cognitive and motor performance. Moreover, the individual effect sizes obtained for this test suggested an exposure-response relationship. Results obtained from either raw or adjusted mean scores revealed that confounding in the data could not be excluded. The results were compared to studies not included here due to a shortage of required data. Similarities were discussed in terms of sensitivity of the tests for detecting aluminum-related changes in brain function. There was concurring evidence from different studies that urinary Al concentrations below 135 microg/l have an impact on cognitive performance. The significant effect for the digit symbol might be related to its multifaceted character which requires functioning in different components of cognitive and motor performance. This feature could possibly turn the test into a screening instrument for neurobehavioral effects. However, additional studies are necessary to verify and to differentiate the effect of aluminum on cognitive performance. From a neuropsychological perspective, implicit and explicit memory, visuo-spatial and central odor processing should be examined. A measure of verbal intelligence should be included in order to address the influence of confounding. Internationally standardized exposure measures would enhance the comparability of studies.

Soluble RANKL in crevicular fluid of dental implants: a pilot study.

BACKGROUND: Receptor activator of NF-kappaB ligand (RANKL), a member of the tumor necrosis factor superfamily, is a key mediator of osteoclast formation, activation, and survival. Thus, it is reasonable to hypothesize that there might be a functional relationship between RANKL expression and peri-implantitis. PURPOSE: This pilot study was performed to determine the reference levels for soluble RANKL (sRANKL) in peri-implant crevicular fluid and to correlate them with the clinical parameters associated with inflammatory reactions and bone destruction. MATERIALS AND METHODS: The clinical parameters probing depth (PD), modified bleeding index (MBI), and modified plaque index (MPI) served as indicators for bone resorption and inflammation. Exclusion criteria for calculations were the detection limit of the immunoassay and the minimum acceptable crevicular volume for measurement. From the 84 collected samples of 16 patients, 30-84 years of age, with a total of 19 implants, 29 met these criteria. The absolute amount of sRANKL within crevicular fluid adsorbed to filter strips was a median of 0.18 femtomol (fmol; range, 0.08-0.53) and 0.26 nM (range, 0.09-1.21) when normalized by volume. PD was 4 mm in median and varied within a range between 2 and 12 mm. RESULTS: Absolute amounts of sRANKL showed no correlation with the adsorbed volume and the clinical parameters PD, MBI, and MPI. When sRANKL was normalized by volume, no correlation with the clinical parameters PD, MBI, and MPI was observed either. The patients' age was not associated with total sRANKL and the concentration of RANKL within crevicular fluid. Absolute levels of sRANKL and sRANKL concentration did not show any differences based on the sampling sites buccal and lingual, or on the patients' gender. A significant difference in sRANKL concentration was detectable when samples from maxillary implants (0.31 nM median; range, 0.12-1.21) were compared with samples from mandibular implants (0.21 nM median; range, 0.09-0.6) (p=.03). Absolute levels of sRANKL were not different between the maxilla and the mandible. CONCLUSION: Given the limited sample size, our data provide a basis for future prospective longitudinal studies on the possible relevance of sRANKL as a prognostic marker in peri-implantitis, and for an understanding of the pathophysiologic process of the disease as a prerequisite for the design of treatment strategies.

Peri-implant bone loss as a function of tooth-implant distance.

PURPOSE: In a retrospective study, the radiographs of 39 patients with Applegate-Kennedy Class I or II in the posterior mandible who had been treated with screw-anchored fixed partial dentures supported by IMZ implants and natural teeth were examined for the presence of radiologically detectable peri-implant bone loss. Furthermore, the results were correlated with a mathematical model. MATERIALS AND METHODS: The radiographs of the implants were digitized, and the areas of bone atrophy mesial and distal to the implants were determined semi-automatically. The data obtained were correlated with the distance between the implant and the abutment tooth. The connection between the tooth-supported crown and the implant-supported denture was made with a vertical screw-lock precision attachment. In a mathematical analysis it was assumed that the fixed partial prosthesis was a rigid beam with 3 elastically embedded supports. RESULTS: The mean distance between the tooth and the first implant was 11.02 mm (SD: 4.24), and between the tooth and the second implant was 20.25 mm (SD: 5.16). Peri-implant bone loss significantly followed a rational function (mesial implant: P = .03, distal implant: P = .02), meaning that, as the tooth-implant distance increased, the area of atrophy became rapidly larger and then diminished gradually. Distances of 8 to 14 mm between the tooth and the first implant and of 17 to 21 mm between the tooth and the second implant were associated with a more pronounced bone loss. These results were also confirmed mathematically. CONCLUSION: A tooth-implant distance of 8 to 14 mm for the first implant and 17 to 21 mm for the second implant should be avoided for implant placement if prosthetic rehabilitation is planned using a fixed partial denture supported by a premolar and 2 IMZ implants in the mandible. Although this investigation was done on IMZ implants only, the results were confirmed by a mathematical model, which indicated that the observed bone loss may be the same in other types of implants placed in the same positions.

Proliferation and osteogenic differentiation of cells from cortical bone cylinders, bone particles from mill, and drilling dust.

PURPOSE: The osteogenic potential of a graft is based on the parallel lines ability of cells to survive transplantation and to respond to local factors that stimulate new bone formation. Here we investigated the potential of cells that had grown out of porcine cortical bone grafts obtained by 3 preparation techniques to respond to mitogenic and osteogenic stimuli. MATERIALS AND METHODS: Bone grafts were harvested from 2 pigs. Cortical bone was taken in cylindrical form and ground in a bone mill or harvested via drilling and aspiration. RESULTS: Cell outgrowth was observed in all cortical bone cylinders, bone cylinders homogenized by mill, and 5 of 10 explants of bone dust collected upon drilling. After a 2-week culture period, the number of outgrown cells did not significantly differ among the 3 preparations. Bone cells showed increased proliferation in response to platelet-released supernatants as determined by 3 [H]-thymidine incorporation assay. When cultured under conditions that favor the expression of an osteogenic phenotype, the outgrown cells expressed alkaline phosphatase activity and transcripts of the osteoblast-specific marker osteocalcin. Individual cell preparations showed accumulation of mineral salts in their extracellular matrix. Bone cells also increased alkaline phosphatase activity in response to bone morphogenetic protein (BMP)-2, BMP-6, and BMP-7. The mitogenic and osteogenic response was obtained with cells from the mandible as well as from the maxilla, irrespective of the preparation technique. CONCLUSION: These data show that cortical bone grafts contain cells that have the ability to proliferate and differentiate into the osteogenic lineage, suggesting that these cells can contribute to bone regeneration following transplantation.

A meta-analytical approach to neurobehavioural effects of occupational toluene exposure.

Twenty-two studies investigating neurobehavioural effects of toluene were reviewed. Repeatedly applied neuropsychological performance tests and appropriately documented results allowed to include 10 of the studies into a meta-analysis based on effect sizes. Mean exposure level of the studies was 57ppm (range 20-117ppm) toluene. Five of the six analyses of neuropsychological tests obtained effect sizes suggesting a negative impact of toluene, but for none of the analyses a significant effect size was estimated at averaged exposure levels between 33 and 89ppm. The tests represented the psychological domains of attention and constructional performance. Additionally, the relation between exposure conditions (level of exposure, length of exposure), potential confounders (age, verbal intelligence), and effect sizes was analysed. Only pre-exposure intellectual capacity showed a consistent relation to effect sizes. The study suggests that homogenisation of study groups with respect to intelligence, cultural background and practice trials is important when investigating low-level exposure. Efforts to homogenize studies should be completed by a thorough documentation of feasible influences.

Impairments of colour vision induced by organic solvents: a meta-analysis study.

The impairment of colour discrimination induced by occupational exposure to toluene, styrene and mixtures of organic solvents is reviewed and analysed using a meta-analytical approach. Thirty-nine studies were surveyed covering a wide range of exposure conditions. Those studies using the Lanthony Panel D-15 desaturated test (D-15d) were further considered. From these for 15 samples data on colour discrimination ability (Colour Confusion Index, CCI) and exposure levels were provided, required for the meta-analysis. In accordance with previously reported higher CCI values for the exposed groups, the computations yielded positive effect sizes for 13 of the 15 samples, indicating that in the great majority of the studies the exposed groups showed inferior colour discrimination. However, the meta-analysis showed great variation in effect sizes across the studies. Possible reasons for inconsistency among the reported findings are discussed. These pertain to exposure-related parameters, as well as to confounders such as conditions of test administration and characteristics of subject samples. Those factors vary considerably among the studies and might have greatly contributed to divergence in measured colour vision capacity, thereby obscuring consistent effects of organic solvents on colour discrimination.

Implants in an HIV-positive patient: a case report.

Human immunodeficiency virus (HIV) causes an immune incompetence that weakens the body's defense against pathogens. It has been supposed that HIV-positive patients are more likely to develop both early and late postoperative complications, such as septicemia and poor wound healing. This has not been corroborated by more recent studies but seems to depend on the patient's level of CD4 cells and his or her general condition. As the life expectancy of HIV-positive individuals increases and the condition becomes increasingly controllable, esthetic dental treatment becomes more significant and implant-supported prostheses may be considered as an alternative to removable dentures. Except for a single case report on the immediate placement of a single-tooth implant, no reports are available on implant dentistry in HIV-positive patients. This case report concerns implant placement in the maxilla and mandible of an HIV-positive individual and complete dental and implant rehabilitation. Two years after implant placement, the prosthesis is functioning well.

Neurobehavioural test results and exposure to inorganic mercury: in search of dose-response relations.

The aim of the analysis was, in general, to find a way to summarise results of studies in search of exposure-response relationships and, in particular, to ask whether an exposure-response relationship can be ascertained for neurobehavioural studies on occupational mercury exposure. Eighteen studies dealing with human mercury exposure and examining 1,106 exposed and 1,105 control subjects were included in the analysis. Effect sizes were calculated for each of the single neuropsychological test results on cognitive and motor performance and were considered in relation to mean current concentrations of exposure. The total of effect sizes demonstrated a correlation to exposure in the range of r=0.50. Additional analyses showed that the influence of mercury on psychological functions was different and that results on motor performance compared with memory and attention revealed the greatest impairment in mercury-exposed workers. Implications for the reversibility of impairments could be discussed because three of the studies examined subjects whose exposure had ceased. Besides the usefulness of the approach, it became obvious that the available 18 studies are a small sample, even when non-dimensional effect-sizes are used; hence, not all psychological domains covered by tests could be analysed.

Porous hydroxyapatite for grafting the maxillary sinus in sheep: comparative pullout study of dental implants.

PURPOSE: In this experimental study, dental implants placed after maxillary sinus grafting with either porous hydroxyapatite (HA) (Interpore 200) or autogenous bone were examined for their mechanical stress tolerance. MATERIALS AND METHODS: A total of 54 titanium plasma flame-sprayed cylindric implants were placed in the lateral sinus wall bilaterally of 27 mountain sheep. The bony sinuses were opened through an extraoral approach. Eighteen sinuses were grafted with porous HA, and another 18 were grafted with cancellous bone from the iliac crest. Eighteen non-grafted sinuses were used as controls. In the same operation, 2 cylindric implants were placed in each of the sinuses. One implant of each sinus was tested for mechanical strength of the bone-implant interface at 12, 16, and 26 weeks using pullout force. RESULTS: The mean pullout force was 259.3 N in the control group, 356.7 N in the autogenous bone group, and 376 N in the HA group. Pooled data for the grafted sites showed the pullout force to be significantly higher than in the empty control sites (P = .02). The pullout force increased significantly with ongoing healing time (P = .02), but there was considerable variation within the groups. While the force remained more or less constant throughout the follow-up time in the controls (248 N at week 12 to 276 N at week 26), it increased dramatically in the group augmented with autogenous bone (223.8 N at week 12 to 523.16 N at week 26). The pullout force was initially highest in the HA group (302.3 N at week 12) and increased to 423.5 N at 26 weeks, but it did not reach the levels recorded in the autografted group. DISCUSSION AND CONCLUSION: Mechanical tests of bone-to-implant contact in a sheep model showed that HA for 1-stage sinus floor elevation significantly increased the pullout force versus ungrafted sinuses, although it was less than that found with autogenous bone after 26 weeks.

A preliminary study of monocortical bone grafts for oroantral fistula closure.

Sinus floor elevation has become a standard procedure in patients affected by severe maxillary atrophy, before implant placement, provided that the maxillary sinus is intact and uninfected. In the case of an oroantral fistula, simple soft tissue closure may interfere with the process of elevating the Schneiderian membrane. Total regeneration of the bony sinus floor is necessary to prevent disruption of the sinus membrane. In this study, 5 patients with oroantral fistulae of different causes were treated with autogenous monocortical bone blocks harvested from the chin. Press-fit closure for bony repair of the basal maxilla was sufficient in 3 of them. Two patients needed additional internal graft fixation. In the meantime, the 3 aforementioned patients underwent a successful sinus lift procedure. The use of a monocortical bone block for the closure of an oroantral fistula is recommended before internal sinus augmentation.

Porous hydroxyapatite for grafting the maxillary sinus: a comparative histomorphometric study in sheep.

PURPOSE: This experimental study in adult female sheep examined the value of nonresorbable porous hydroxyapatite (HA) as a grafting material in a single-stage sinus-lift procedure. MATERIALS AND METHODS: Two titanium plasma-flame-sprayed cylindric implants were placed bilaterally in each of 54 sinuses in 27 adult female sheep. In 2 groups of 18 sinuses each, the subantral hollow space was filled with porous HA or autogenous cancellous bone harvested from the iliac crest, respectively. Eighteen sinuses were not augmented and served as controls. The time course of new bone formation and bone remodeling was evaluated by sequential polyfluorochrome labeling. Observation periods were 12, 16, and 26 weeks after the surgical procedure. Six sinuses per observation period and test group were available for histologic evaluation. RESULTS: All implants were osseointegrated in the local host bone. New bone formation was observed in a triangular area bounded by the implant surface, local buccal antral wall, and submucous connective tissue around all implants. The mean length of bone-implant contact was 3.9 +/- 0.3 mm in the control group, 5.7 +/- 0.3 mm in the autogenous bone group, and 5.9 +/- 0.3 mm in the group augmented with porous HA. During the observation period, the relative length of direct bone-implant contact increased from 20% to 25.1% in the control group, from 30.4% to 35.5% in the autogenous bone group, and from 29.8% to 41.7% in the HA group. At a distance of 1 mm from the implant, the mean bone volume was 29.7 +/- 15.7% in the autogenous bone group. In the group augmented with HA the mean bone volume was 11.2 +/- 13.0%. DISCUSSION: There was no significant difference between HA and autogenous bone regarding bone-implant contact (P = .89). CONCLUSIONS: Both groups showed a significantly greater bone-implant contact (HA: P = .002; autogenous bone: P = .0005) than the empty control group. However, since the results varied widely, the use of HA alone for sinus grafting should be used with discretion in sinus-lift procedures.