Biomedical subjects

N P Lang

Publications and source records attributed to N P Lang.

At least 19 recordsLinked to original sources

PubMed1997

Immunochemical, 32P-postlabeling, and GC/MS detection of 4-aminobiphenyl-DNA adducts in human peripheral lung in relation to metabolic activation pathways involving pulmonary N-oxidation, conjugation, and peroxidation.

4-Aminobiphenyl (ABP) is a recognized human bladder carcinogen, whose presence in cigarette smoke results in DNA adduct formation in the human urothelium. Since preliminary studies indicated that even higher levels of ABP-DNA adducts may be present in human peripheral lung, we utilized a sensitive immunochemical assay, in combination with 32P-postlabeling, to quantify the major 4-aminobiphenyl (ABP)-DNA adduct, N-(guan-8-yl)-ABP, in surgical samples of peripheral lung tissue from smokers and ex-smokers. No differences in adduct levels were detected between smokers and ex-smokers by immunoassay. In contrast, the 32P-postlabeling method showed statistically significant differences between adduct levels in smokers and ex-smokers; however, a relatively high background of smoking-related adducts chromatograph near the major ABP adducts and may compromise estimation of the level of ABP-DNA adducts in smokers. Furthermore, the levels measured by 32P-postlabeling were 20- to 60-fold lower than that measured by immunoassay. Since 32P-postlabeling may underestimate and immunochemical assays may overestimate adduct levels in the lung, selected samples were also evaluated by GC/MS. The immunochemical and GC/MS data were concordant, leading us to conclude that N-(guan-8-yl)-ABP adducts were not related to smoking status. Since ABP-DNA adduct levels in human lung did not correlate with smoking status as measured by immunoassay and GC/MS, the metabolic activation capacity of human lung microsomes and cytosols was examined to determine if another exposure (e.g., 4-nitrobiphenyl) might be responsible for the adduct. The rates of microsomal ABP N-oxidation were below the limit of detection, which was consistent with a lack of detectable cytochrome P4501A2 in human lung. N-Hydroxy-ABP O-acetyltransferase (but not sulfotransferase) activity was detected in cytosols and comparative measurements of N-acetyltransferase (NAT) using p-aminobenzoic acid and sulfamethazine indicated that NAT1 and NAT2 contributed to this activity. 4-Nitrobiphenyl reductase activity was found in lung microsomes and cytosols, with the reaction yielding ABP and N-hydroxy-ABP. Lung microsomes also demonstrated high peroxidative activation of ABP, benzidine, 4,4'-methylene-bis(2-chloroaniline), 2-aminofluorene, and 2-naphthylamine. The preferred co-oxidant was hydrogen peroxide and the reaction was strongly inhibited by sodium azide but not by indomethacin or eicosatetraynoic acid, which suggested the primary involvement of myeloperoxidase rather than prostaglandin H synthase or lipoxygenase. This was confirmed by immunoinhibition and immunoprecipitation studies using solubilized human lung microsomes and antisera specific for myeloperoxidase. These data suggest that ABP-DNA adducts in human lung result from some environmental exposure to 4-nitrobiphenyl. The bioactivation pathways appear to involve: (1) metabolic reduction to N-hydroxy-ABP and subsequent O-acetylation by NAT1 and/or NAT2; and (2) metabolic reduction to ABP and subsequent peroxidation by myeloperoxidase. The myeloperoxidase activity appears to be the highest peroxidase activity measured in mammalian tissue and is consistent with the presence of neutrophils and polymorphonuclear leukocytes surrounding particulate matter derived from cigarette smoking.

Acyltransferases↗

PubMed1997

Chemoprotection against the formation of colon DNA adducts from the food-borne carcinogen 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) in the rat.

The mutagenic heterocyclic aromatic amine, 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), is a pyrolysis product in cooked foods that has been shown to be a rat colon carcinogen and has been implicated in the etiology of human colon cancer. In order to identify chemoprotection strategies that could be carried out in humans, a pilot study was conducted in which PhIP-DNA-adduct levels were quantified in the colons of male F344 rats that had been subjected to 16 different putative chemoprotection regimens, followed by a gavage of PhIP (50 mg/kg) and sacrifice 24 h later. The 16 treatments (Oltipraz, benzylisothiocyanate, diallyl sulfide, garlic powder, ethoxyquin, butylated hydroxyanisole, glutathione, indole-3-carbinol, alpha-angelicalactone, kahweol/cafestol palmitates, quercetin, green tea, black tea, tannic acid, amylase-resistant starch, and physical exercise) comprised sulfur-containing compounds, antioxidants, flavonoids, diterpenes, polyphenols, high dietary fiber, etc. The strongest inhibition of PhIP-DNA adduct formation in the colon was observed upon pretreatment with black tea, benzylisothiocyanate, and a mixture (1:1) of kahweol:cafestol palmitates, which resulted in 67, 66, and 54% decreases in colon PhIP-DNA adduct levels, as compared with controls. Preliminary studies on their mechanism of action indicated that only kahweol:cafestol caused a substantial induction of glutathione S-transferase isozymes (GSTs) that are thought to be important in the detoxification of PhIP. Notably, this induction occurred in the liver rather than in the colon.

Animals↗

PubMed1997

Polymorphisms of CYP1A1 and GSTM1 influence the in vivo function of CYP1A2.

Differences in human cancer susceptibility have been attributed to polymorphisms of carcinogen metabolizing enzymes. Our efforts have focused on the systems responsible for metabolism of aromatic and heterocyclic amines found in cigarette smoke and in cooked foods. Cytochrome P4501A2 (CYP1A2), which catalyzes aromatic and heterocyclic amine N-oxidation, has been implicated as a risk factor in both urinary bladder and colorectal cancer. In the present study we used the results of caffeine phenotyping experiments to measure the effects of cigarette smoke and compounds present in meat cooked at high temperature on CYP1A2 activity. Subjects in the smoking cessation study had mean CYP1A2 activity of 17.8 (expressed as the urinary molar ratio of [17X + 17U]/137X) while smoking: however, this activity decreased to 10.9 three weeks after cessation of smoking. Subjects in the cooked meat feeding study had mean CYP1A2 activity of 9.01 after 1 week of consuming meat cooked at low temperature, but this value increased to 12.7 after 1 week of consuming meat cooked at high temperature. Because no association has been identified between differences in CYP1A2 activity and variations in the CYP1A2 structural gene, we sought to determine whether the activities of other carcinogen metabolizing enzymes are involved in the regulation of CYP1A2 activity. CYP1A2 activity was higher in individuals who express the GSTM1 null allele compared to those expressing the GSTM1*A,B allele, 10.2 vs. 8.5 for unexposed conditions and 15.0 vs. 12.3 for exposed conditions. CYP1A1 genotyping demonstrated that individuals possessing the Ile/Ile CYP1A1 genotype had greater mean CYP1A2 activity than those who had the heterozygous Ile/Val allelic variant of the CYP1A1 gene. However, upon exposure to cigarette smoke or high-temperature cooked meat, individuals possessing the heterozygous form of the CYP1A1 gene had significantly increased CYP1A2 activity (18.1) compared to those with the more common Ile/Ile CYP1A1 genotype (13.3). These results indicate that CYP1A2, CYP1A1, and GSTM1 gene-gene interactions could be important confounders in the interpretation of molecular epidemiology studies.

Arylamine N-Acetyltransferase↗

PubMed1997

Who should teach medical students surgery?

BACKGROUND: Medical schools are undergoing major curricular reform, partly in attempts to increase the number of graduates pursuing careers in the generalist disciplines. These reforms have often resulted in a shortening of the surgery clerkship, decreasing students' experiences in several domains important to the generalist. METHODS: A seven-question survey of clerkship directors of US medical schools was administered to measure the magnitude of curriculum change during the past 5 years affecting the surgery and family practice clerkships. The survey also addressed attitudes about the purpose of the surgery clerkship. RESULTS: There was an 80% (103 of 129) response rate. Between 1989 and 1994, surgery clerkships decreased on average from 11 to 10.2 weeks (P <0.05) while family practice clerkships increased from 4.2 to 6.8 weeks (P <0.05). Ninety-one percent of clerkship directors felt the primary goal of the clerkship should be to train generalists. CONCLUSIONS: The length of the surgery clerkship has decreased at several institutions. In order to ensure an appropriate educational experience for medical students, surgeons must participate actively in curriculum reform within medical schools and highlight their unique role in training generalists.

Clinical Clerkship↗

PubMed1997

Metabolic activation of aromatic amines by human pancreas.

Epidemiologic studies have suggested that aromatic amines (and nitroaromatic hydrocarbons) may be carcinogenic for human pancreas. Pancreatic tissues from 29 organ donors (13 smokers, 16 non-smokers) were examined for their ability to metabolize aromatic amines and other carcinogens. Microsomes showed no activity for cytochrome P450 (P450) 1A2-dependent N-oxidation of 4-aminobiphenyl (ABP) or for the following activities (and associated P450s): aminopyrine N-demethylation and ethylmorphine N-demethylation (P450 3A4); ethoxyresorufin O-deethylation (P450 1A1) and pentoxyresorufin O-dealkylation (P450 2B6); p-nitrophenol hydroxylation and N-nitrosodimethyl-amine N-demethylation (P450 2E1); lauric acid omega-hydroxylation (P450 4A1); and 4-(methylnitrosamino)-1-(3-pyridyl-1-butanol) (NNAL) and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) alpha-oxidation (P450 1A2, 2A6, 2D6). Antibodies were used to examine microsomal levels of P450 1A2, 2A6, 2C8/9/18/19, 2E1, 2D6, and 3A3/4/5/7 and epoxide hydrolase. Immunoblots detected only epoxide hydrolase at low levels; P450 levels were <1% of liver. Microsomal benzidine/prostaglandin hydroperoxidation activity was low. In pancreatic cytosols and microsomes, 4-nitrobiphenyl reductase activities were present at levels comparable to human liver. The O-acetyltransferase activity (AcCoA-dependent DNA-binding of [3H]N-hydroxy-ABP) of pancreatic cytosols was high, about twothirds the levels measured in human colon. Cytosols showed high activity for N-acetylation of p-aminobenzoic acid, but not of sulfamethazine, indicating that acetyltransferase-1 (NAT1) is predominantly expressed in this tissue. Cytosolic sulfotransferase was detected at low levels. Using 32P-post-labeling enhanced by butanol extraction, putative arylamine-DNA adducts were detected in most samples. Moreover, in eight of 29 DNA samples, a major adduct was observed that was chromatographically identical to the predominant ABP-DNA adduct, N-(deoxyguanosin-8-yl)-ABP. These results are consistent with a hypothesis that aromatic amines and nitroaromatic hydrocarbons may be involved in the etiology of human pancreatic cancer.

Acetyltransferases↗

PubMed1997

Clinical response to local delivery of tetracycline in relation to overall and local periodontal conditions.

The purpose of this study was to determine the clinical response to local delivery of tetracycline in relation to clinical and microbiological conditions of the other teeth. 4 deep pockets were monitored in 19 subjects with multiple deep periodontal lesions and high counts of P. gingivalis. In 9 patients (LT) only 2 of the selected lesions were treated by placement of tetracycline fibers (Actisite), while the rest of the dentition was left untreated. In the other 10 patients, all teeth were supragingivally scaled and then treated by application of polymeric tetracycline HCl containing fibers, the whole dentition was subject to full mouth scaling and root planing, and the patients rinsed with 0.2% chlorhexidine (FT). A significant reduction in mean PPD was observed in all treated sites after two months. This reduction was maintained over the following 4 months. The magnitude of the effect was significantly greater in the FT group (1.74 mm) than in the LT group (0.88 mm). The mean attachment level changes were similar after 2 months in locally and fully treated subjects. A tendency of relapse was noted for treated sites in LT patients from month 2 to 6. A level of statistical significance was not reached for this effect. Data from measurements recorded at 6 sites around all teeth in the full mouth treated patients were analyzed using multiple linear regression. This analysis showed local changes in PPD and AL were significantly and strongly correlated with the baseline value of the respective parameter at the same site. In addition, more pocket depth reduction was noted if a site was not bleeding on probing at 6 months, if the location of a site was not approximal and if the tooth was not a second molar. Sites located on second molars showed also less AL gain than sites located on other teeth. Smokers showed significantly less reduction in PPD and significantly less AL gain. Furthermore, if subjects had a high % of pockets deeper than 4 mm at baseline they showed significantly less attachment gain.

Adult↗

PubMed1997

Monocytic TNF alpha secretion patterns in IDDM patients with periodontal diseases.

The aim of the present study was to identify whether monocytic TNF alpha secretion patterns could serve as a potential phenotypic discriminator for periodontal disease susceptibility within insulin-dependent diabetes mellitus (IDDM) patients. In 32 IDDM individuals the lipopolysaccharide (LPS) stimulated monocytic TNF alpha secretion dose-response characteristics were analyzed and related to two different periodontal status categories. Diabetics were divided into group A (gingivitis or mild periodontal disease) and group B (moderate to severe periodontal disease). In addition, 17 non-diabetic individuals with various degrees of periodontal disease served as control patients. Diabetics as a group had a significantly higher monocytic TNF alpha production in response to increasing Porphyromonas gingivalis A 7436 lipopolysaccharide concentrations (0, 0.003, 0.03, 0.3 and 3.0 micrograms/ml) as compared to non-diabetic patients with gingivitis or adult periodontitis (p < 0.05). A significant difference in the dose response was also noted in the level of TNF alpha secreted as a function of P. gingivalis LPS concentrations between group A and B diabetics, as determined by two-way repeated measurements ANOVA (p < 0.05). Furthermore, there was no significant difference in the mean HbA1C between the two diabetic groups, and the TNF alpha level was not significantly associated with the HbA1C level within diabetic patients. These data suggest that the diabetic state results in an upregulated monocytic TNF alpha secretion phenotype (4.6-fold increase) which, in the presence of Gram-negative bacterial challenge, is associated with a more severe periodontal disease expression. In addition, approximately 40% (10 of 24) IDDM periodontitis patients in group B demonstrated a 62-fold elevation in TNF alpha secretion relative to non-diabetic gingivitis or periodontitis patients and a 13.5-fold increase relative to IDDM group A (gingivitis or mild periodontitis) patients.

Adult↗

PubMed1997

Acetylation as an indicator of risk.

Aromatic amine acetylation has been recognized for many years as an important metabolic polymorphism in humans because of its relationship to disease. This system serves as a model in risk assessment because of its role in drug and carcinogen activation and detoxification and because of the case with which it is measured. However, possible interactions of NAT1-NAT2 phenotypes or genotypes illustrate the complexity of xenobiotic metabolism pathways. Moreover, the use of such information for risk assessment is further complicated by the association of the rapid phenotype with increased risk in colon cancer and the slow phenotype with increased risk in urinary bladder cancer. Before this biomarker can be effectively utilized as a significant predictor of individual risk, it will be necessary to identify specific sources of aromatic amine exposure and to characterize further the substrate specificity of NAT1 and NAT2 in relation to the multiplicity of enzyme variants occurring in human populations.

Acetylation↗

PubMed1997

Clinical trials on therapies for peri-implant infections.

Peri-implant infections are pathological conditions which are normally localized in the soft tissues surrounding an oral implant. They may range from a rather localized mucositis lesion reflecting the host response to a bacterial challenge to a more advanced lesion "termed peri-implantitis" when previously osseointegrated oral implants have been partially disintegrated; i.e. have lost alveolar bone around the implant. Usually these lesions start as a result of plaque accumulation and show similar progression as observed around teeth. Muscositis seems to be a prerequisite for the following peri-implantitis. However, the factors involving the transition to a more advanced lesion are still not known. Logically, the therapy for peri-implant infection has to be related to antibacterial treatment prior to the attempt to surgically regenerate peri-implant alveolar bone lost as a result of the infection. In order to diagnose these lesions at an early stage frequent assessments of clinical parameters are needed during maintenance therapy. The anti-infective treatment may intercept the development of the lesion. Following mechanical debridement of plaque deposits the application of efficacious antiseptics (chlorhexidine) is a necessity. Following this, antibiotics may cumulatively be applied to control the infection. Only a few longitudinal studies have documented the efficacy of such treatment regimens, and controls have generally not been available for ethical reasons. In regenerating the lost jaw bone only case reports are available today. Controlled animal studies will have to be performed to document the possibility of re-osseointegration and the factors influencing predictability.

Animals↗

PubMed1996

The significance of bone in periodontal disease.

Although the connective tissue attachment represents the key issue in periodontal health or disease and in periodontal therapy, the assessment of alveolar bone changes renders valuable indirect evidence for periodontal stability, progression of disease, or repair mechanisms. In periodontal disease bacterial products trigger host cells to release mediators, which may imbalance the steady state between resorption of bone and apposition of osteoid. Modulation of the hosts prostaglandin or interleukin-I synthesis by drug therapy could support the antimicrobial concept of periodontal therapy. Cross-sectional and long-term assessments of alveolar bone have been used to estimate the progression rate of periodontal disease. Inherent limitations of bone assessments in radiographs have to be considered when drawing conclusions from measurements that represent remodeling in periodontal lesions after therapy. Both bone quantity and quality seem to be of secondary importance with respect to the progression of disease, as well as response to therapy. Other risk factors that affect the microbial ecology and/or the hosts immune system seem to be the primary determinants for the periodontal health status.

Alveolar Bone Loss↗

PubMed1996

A novel model system for the study of experimental guided bone formation in humans.

The aim of the present experiment was to test a novel model system, designed to obtain human specimens of regenerated and also newly regenerated jaw bone, for the study of the biological events under a variety of conditions. Following information and disclosure of possible risks associated with a minor oral surgical procedure, 9 systemically healthy subjects (5 men, 4 women, mean age 31.7 years) signed consent forms and volunteered to participate in this study. Hollow test cylinders with an outer diameter of 3.5 mm, an inner diameter of 2.5 mm, and 4 mm in height were used. They were manufactured from commercially pure titanium and exhibited a highly polished inner surface and a titanium plasma sprayed outer rough surface. A mucoperiosteal flap was raised in the retromolar area of the mandible corresponding to standard retrained third molar surgery. Following flap reflection a standardized hole was drilled through the cortical bone into the bone marrow using round burs. The congruent test cylinders were firmly placed into the prepared bony bed yielding primary stability. One-and-a-half to 2 mm of the test device were submerged below the level of the surrounding bone, while the remainder surpassed the level of the bone surface. The bone-facing end of the cylinder was left open, while the coronal soft tissue facing end was closed by an ePTFE-membrane. The flap was sutured to obtain primary wound closure. In order to prevent infection, penicillin was prescribed systemically and oral rinses of chlorhexidine were administered. After 2, 7, and 12 weeks one test device including the regenerated tissue was surgically harvested, while after 16, 24 and 36 weeks respectively, 2 devices were harvested and processed for soft or hard tissue histology or histochemistry. The two surgical procedures and the presence of the test cylinders during the time of healing were well tolerated by the volunteers. In all 9 subjects generated tissue could successfully be harvested. The tissue generated after 2 and 7 weeks presented with a cylindrical shape, whereas the specimens harvested at 12 weeks and thereafter resembled the form of an hourglass. Specimens of 12 weeks and less regeneration time were almost entirely comprised of soft tissue, while specimens with regeneration time of 4 months and more were composed of both soft and increasing amounts of mineralized tissue. It is concluded that the presented model system is suitable to study temporal dynamics and tissue physiology of bone regeneration in humans with minimal risk for complications or adverse effects to the volunteers.

Adult↗

PubMed1996

Thresholds for tactile sensitivity perceived with dental implants remain unchanged during a healing phase of 3 months.

The aim of the present study was to determine the tactile pressure thresholds perceived with dental implants during a three-month healing phase following implant placement (osseointegration phase). The absolute threshold of tactile perception was measured in a group of patients 1 week, 1, 2 and 3 months following implant placement (ITI Dental Implant System, Straumann AG, Waldenburg, Switzerland). Contralateral and neighbouring teeth were measured at the same time. For determination of the axial forces exerted on the implants and teeth, and electronic device with semi-conductor strain gauges was used (Hämmerle et al. 1995). The results demonstrated mean thresholds of tactile perception for the implants of 160.2 g (SD 61.7 g, range 77 approximately 283 g) at 1 week, 133.4 g (SD 51.9 g, range 32 approximately 239 g) at 1 month, 147.9 g (SD 53.5 g, range 70 approximately 257 g) at 2 months, and 146.9 g (SD 57.4 g, range 77 approximately 248 g) at 3 months. Statistical analysis using Student's paired t-test revealed no significant differences between the values over time. The control teeth exhibited mean values for tactile perception of 13.1 g (SD 9.6 g, range 5 approximately 47 g) at 1 week, 10.2 g (SD 6.4 g, range 4 approximately 29 g) at 1 month, 14.8 g (SD 15.9 g, range 2 approximately 58 g) at 2 months, and 15.4 g (SD 12.2 g, range 3 approximately 36 g) at 3 months. Again, these values did not differ significantly from each other and indicated the absence of systemic alterations in perceived pressure threshold over the observation period. The mean perceived pressure threshold was more than 10 times higher for implants than for natural teeth (P < 0.001) at all observation times. It is concluded that the absolute threshold of tactile perception with dental implants during the phase of osseointegration is not affected by bone and soft tissue healing taking place during the time period.

Adult↗

PubMed1996

Maintenance of implants: an in vitro study of titanium implant surface modifications subsequent to the application of different prophylaxis procedures.

The aim of the present study was to evaluate surface alterations on titanium implant necks subsequent to different prophylaxis procedures. Fifty ITI implants were utilized. Forty implants were treated with 10 different prophylaxis procedures (ultrasonic scaler, plastic tip ultrasonic scaler, stainless steel curette, titanium curette, teflon curette, air powered system, abrasive rubber cups, polishing rubber cup and brush), and 10 implants were left as untreated controls. Surface alterations were studied on an area of 1 mm x 0.9 mm and quantified using optical microscopic, SEM and laser prophylometer analysis. The use of laser prophylometer provided an objective criterion for evaluation, expressing implant neck surface alterations in numeric values in terms of two roughness indexes, Ra and Rz. The results showed that, in comparison with the controls (Ra = 0.50; Rz = 3.98) the procedures investigated could be divided into 3 main groups: 1) Methods which altered the implant neck surface producing increased roughness (Ra = 0.68-2.08; Rz = 4.68-11.92); 2) Methods which left the implant neck surface unaltered (Ra = 0.44-0.57; Rz = 0.42-3.46); 3) Methods resulting in a smoothening of the implant neck surface (Ra = 0.36; Rz = 2.15). Group 1 included procedures that should be avoided. However, it appeared safe to apply the procedures of groups 2 and 3. To confirm these results, it will be necessary to evaluate the plaque- and calculus-removing efficacy from titanium neck implant surfaces in vivo.

Air↗

PubMed1996

The effect of subcrestal placement of the polished surface of ITI implants on marginal soft and hard tissues.

In order to achieve esthetically more satisfying results, it has been proposed to place ITI implants with their border between the rough and smooth surfaces below the level of the alveolar crest, thereby obtaining a submucosally located implant shoulder following healing. The aim of the present experimental study was to clinically and radiographically evaluate the tissue response to the placement of one-stage transmucosal implants with the border between the rough and the smooth surfaces sunk by 1 mm into a subcrestal location. 11 patients underwent comprehensive dental care including the placement of 2 implants of the ITI Dental Implant System in the same quadrant (test and control). Randomly assigned control implants were placed according to the manufacturer's instructions, i.e. the border between the rough titanium plasma-sprayed and the smooth polished surfaces precisely at the alveolar crest. At the test implant the apical border of the polished surface was placed approximately 1 mm below the alveolar crest. Probing bone levels were assessed at implant placement (baseline), 4 and 12 months later. Modified plaque and modified gingival indices were recorded at 1, 2, 3, 4 and 12 months. Clinical probing depth and "attachment" levels were measured at 4 and 12 months. All parameters were assessed at 6 sites around each implant. The mean for each implant was calculated and used for analysis. The Wilcoxon matched pairs signed rank test and the Student t-test were applied to detect differences over time and between the test and control implants. At baseline, a mean difference in probing bone level of -0.86 mm (SD 0.43 mm, p < 0.05) was found between test and control implants with the test implants being placed more deeply. Both test and control implants lost a significant amount of clinical bone height during the first 4 months (test 1.16 mm, p < 0.05; control 0.58 mm, p < 0.05). However, only the test implants significantly lost clinical bone height from 4-12 months (test 1.04 mm, p < 0.05; control 0.45 mm, p = 0.08). Overall, the test implants lost 2.26 mm and the control implants 1.02 mm of bone height during the first year of service. On the average, the test implants demonstrated a bone level of 0.38 mm lower than the controls at 12 months. Except for the modified gingival index at 4 months (mean difference 0.21, SD 0.19, p < 0.05), no clinical parameters yielded significant differences between test and control implants at any time. It is concluded that in addition to the crestal bone resorption occurring at implants placed under standard conditions, the bone adjacent to the polished surface of more deeply placed ITI implants is also lost over time. From a biological point of view, the placement of the border between the rough and the smooth surfaces into a subcrestal location should not be recommended.

Adult↗

PubMed1996

Long-term stability of osseointegrated implants in bone regenerated with the membrane technique. 5-year results of a prospective study with 12 implants.

The purpose of the present clinical study was to evaluate the 5-year results of the first 12 implants inserted at the University of Berne in regenerated bone following successful ridge augmentation with the membrane technique. The patients were recalled and examined with clinical and radiographic parameters routinely utilized in prospective studies with standard implants in non-regenerated bone. Based on clinical and radiographic findings, all 12 implants were considered successfully integrated according to strict criteria of success. The detailed analysis of clinical parameters revealed no differences to results of prospective studies on standard implants in non-regenerated bone. All implants demonstrated ankylotic stability which was confirmed by a mean Periotest value of -2.08. The radiographic analysis showed stable bone crest levels with a mean bone loss between the 1- and 5-year examination of 0.30 mm. However, 2 implants exhibited a bone loss of more than 1 mm between the 1- and 5-year examination. Therefore, the prognosis of these 2 implants seems questionable at the present time. It can be concluded that bone regenerated with the membrane technique reacts to implant placement like non-regenerated bone, since all 12 implants achieved successful tissue integration with functional ankylosis. Furthermore, this bone is also load-bearing, since all 12 implants maintained osseointegration over a 5-year period.

Alveolar Bone Loss↗

PubMed1996

Correlations between radiographic, clinical and mobility parameters after loading of oral implants with fixed partial dentures. A 2-year longitudinal study.

The aim of present study was to correlate the changes in the peri-implant tissues occurring after functional loading of non-submerged titanium implants and assessed by radiographic, clinical and mobility measurements. 11 patients with distal extension situations received 18 implants of the ITI Dental Implant System. After a healing period of 3 months, the suprastructures were fabricated and seated 5 months post-surgically. For the assessment of peri-implant bone changes, standardized vertical bitewing radiographs with reproducible exposure geometry were evaluated using computer assisted densitometric image analyses (CADIA) and bone height measurements. Since the radiographic evaluations were performed at mesial and distal sites only, the clinical parameters from these implant aspects were included in the analysis. Clinical periodontal parameters modified for the use around implants were obtained, damping characteristics were expressed as Periotest readings and standardized radiographs were obtained at 1, 3, 6, 12 and 24 months after loading. In addition, radiographs were also taken at the start of functional loading. The data obtained from this small sample of implants demonstrated a wide range of different tissue alterations when using radiographic, clinical and mobility assessments. The parameters of probing attachment level (PAL) in combination with radiographic parameters obtained at 1, 3, and 6 months after loading were good predictors for the peri-implant tissue status at 2 years. This was shown by means of multiple stepwise regression analyses. Mobility measurements did not reveal valuable predictive information with the statistical models applied. Assessments of probing attachment levels using periodontal probes rendered information on peri-implant tissue alterations, which were closely correlated to the radiographically measurable peri-implant bone changes.

Adolescent↗

PubMed1996

Immediate transmucosal implants using the principle of guided tissue regeneration (II). A cross-sectional study comparing the clinical outcome 1 year after immediate to standard implant placement.

The aim of the present study was to compare the peri-implant mucosal conditions 1 year after immediate transmucosal implant placement without or in combination with guided tissue regeneration with the situation after regular placement of transmucosal 1-stage procedure implants in partially edentulous patients. The test group consisted of 15 patients who required the immediate replacement of 20 teeth with oral implants in combination with guided tissue regeneration. The control group 1 consisted of 6 patients who received 8 immediate implants, without concomitant bone regeneration procedure due to the small size of the extracted roots in comparison with diameter of the implants. The 20 patients of the control group 2 were randomly chosen from over 150 partially edentulous patients who received implants of the ITI Dental Implant System according to the standard procedure. Similar favorable clinical parameters were found around the implants of all the 3 groups with low plaque and mucosal indices, similar amounts of recession, pocket probing depths and clinical attachment levels. The immediate implants demonstrated lower frequencies of sites bleeding on probing. The study has established that immediate oral implants are a feasible treatment modality with high predictability.

Bone Regeneration↗

PubMed1996

Transversal fixation of restorations in combination with the Octa abutment of the ITI Dental Implant System.

In aesthetically demanding locations of the dentition, the replacement of a single tooth by means of an oral implant is often difficult because of technical limitations of the abutments systems used. The transversal Fixation System in combination with the Octa abutment of the ITI Dental Implant System presents a novel development to overcome these limitations. The report describes the engineering and design of this technical development.

Dental Abutments↗