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Biomedical subjects

H Stich

Publications and source records attributed to H Stich.

At least 19 recordsLinked to original sources
PubMed2006

Detection of approximal caries with a new laser fluorescence device.

The laser device DIAGNOdent developed for the detection of occlusal caries has limited value on approximal surfaces. The aim of this study was to develop and to test a new laser fluorescence (LF) device for the detection of approximal caries. Light with a wavelength of 655 nm was transported to the approximal surface using two different sapphire fibre tips. Seventy-five teeth were selected from a pool of extracted permanent human molars, frozen at -20 degrees C until use. Before being measured, they were defrosted, cleaned and calculus was removed with a scaler. The molars were set in blocks simulating the contact area of adults. Bitewing radiographs were obtained using Kodak Insight films. After two independent assessments with the new LF device, the teeth were histologically prepared, and assessed for caries extension. Using the laser, specificity values for D1 threshold (outer half of enamel), D2 threshold (inner half of enamel), D3 threshold (dentine) ranged between 0.81 and 0.93, sensitivity between 0.84 and 0.92 with no difference between the two tips. Bitewing radiography showed an inferior performance compared to LF (p<0.05). Intraex aminer reproducibility was high (kappa>.74). The new LF system might be a useful additional tool in detecting approximal caries. Because of its good reproducibility, it could be used to monitor caries regression or progression on approximal surfaces.

Adult↗
PubMed2005

Observations of the periodontal ligament and cementum in cats with dental resorptive lesions.

The etiology of feline dental resorptive lesions is unknown, but some evidence suggests that interactions between components of the periodontium may be initiating factors in the development of these lesions. In the present study, 22 clinically normal teeth were harvested from 7 cats. The teeth and periodontium were radiographed and examined histologically. In addition, 14 of the 22 teeth were examined histometrically. Two teeth were histologically normal with an open apical foramen and two were normal with a closed apical foramen. Histological evidence of periodontal ligament degeneration without cementum resorption was observed in 8 teeth, and varying degrees of cementum resorption were observed in 10 teeth. Mandibular molar and premolar teeth had distal drift, and mandibular canine teeth had mesial drift. Alterations in the periodontal ligament may represent a preclinical stage of dental resorption.

Animals↗
PubMed2003

Degradation of hydroxyapatite coating on a well-functioning femoral component.

We carried out a histological study of a proximally hydroxyapatite (HA)-coated femoral component, retrieved after 9.5 years of good function. The HA coating had completely degraded. Bone was in direct contact with the titanium surface in all the areas which had been coated, with no interposing fibrous tissue. There were no signs of particles, third-body wear, adverse tissue reactions or osteolysis. Bone remodelling was evident by the presence of resorption lacunae; tetracycline labelling showed bone laid down six years after implantation. The loss of the HA-coating had no negative effect on the osseo-integration of the stem. We conclude that the HA coating contributes to the fixation of the implant and that its degradation does not adversely affect the long-term fixation.

Arthroplasty, Replacement, Hip↗
PubMed1999

Obturation of root canals with different sealers using non-instrumentation technology.

AIM: To evaluate and compare the sealing quality of hand- or vacuum-obturated root canals after hand preparation or hydrodynamic cleansing of root canals, respectively. METHODOLOGY: After assessing root curvature, 96 single-rooted deep-frozen teeth were divided into eight comparable groups. The root canals of four groups were instrumented with the balanced force technique. The remaining uninstrumented teeth were connected to a reduced-pressure device (NIT) and the root-canal system perfused with 2.5% NaOCl under alternating pressure fields. This dissolved the pulpal tissues and removed debris from the root-canal system. The canals of the hand-instrumented groups were obturated using the cold lateral condensation method with guttapercha and one of four different sealers (AH26, AH Plus, Apexit and Pulp Canal Sealer EWT). The teeth treated with the alternating pressure device (NIT) were obturated by a vacuum obturation method (NIT) with the same four sealers. The quality of the coronal seal was assessed using a dye penetration method. In order to minimize errors the roots were perfused with water before exposure to the dye, under vacuum. The teeth were then rendered transparent and the depth of penetration of the dye between the wall of the canal and the obturating material was measured with a stereomicroscope. RESULTS: The canals cleaned and filled by NIT showed statistically significantly less dye penetration than those obturated by lateral condensation (P < 0.05). Within the NIT group, Pulp Canal Sealer EWT exhibited significantly more dye penetration than Apexit. Amongst the control lateral condensation groups no significant differences were found between the various sealers. CONCLUSIONS: The present investigation demonstrated the validity of the NIT obturation method in combination with commonly used root-canal sealers.

Bismuth↗
PubMed1999

A retrospective study of dental conditions of captive brown bears (Ursus arctos spp.) compared with free-ranging Alaskan grizzlies (Ursus arctos horribilis).

The teeth of 63 skulls of brown bears (Ursus arctos spp.) that had lived in the Bernese bear pit between 1850 and 1995 were examined and radiographed for occlusion, loss of teeth, calcified dental plaque and calculus, attrition, and caries. Dental pathology and periodontal status were evaluated with respect to age and location in the dentition. Further techniques such as computed tomography, microhardness testing, histologic sectioning, and scanning electron microscopy were used in selected cases to verify the macroscopic and radiographic diagnoses. Fourteen skulls originating from free-ranging wild Alaskan brown bears (Ursus arctos horribilis) were examined as a control group. For zoo bears over 10 yr old, severe enamel and dentinal attrition has been observed in canine teeth, with exposed pulp and proximal lesions in molar teeth. Deposits of calcified dental calculus were found in various locations and increased with age. A much lower degree of calculus deposition was found in the Alaskan grizzlies, whose average caries frequency was higher but with large individual variation and different locations in canine teeth and occlusal lesions in molar and premolar teeth. Radiographic evaluation of perialveolar osteolytic processes revealed a greater frequency of apical and combined apical-marginal lesions of the alveoli in zoo bears over 10 yr old. Stereotypical behavior like cage chewing is a suspected cause of canine tooth and secondary alveolar lesions, whereas a nutritionally inappropriate diet and inadequate opportunities for tooth-cleaning activities are responsible for the lack of natural cleaning and the extensive calculus formation that results. The methods used in this study are useful in assessing and comparing the dental health status of free-ranging bears, and those living in zoological gardens, by evaluating anesthetized bears or bear skull collections representing both groups.

Age Factors↗
PubMed1998

[Diagnosis and therapy of the rupture of both cruciate ligaments, the medial collateral ligament and abscission of both menisci in a ram. A case report].

This report describes the case history of a 1.5-year-old ram admitted to the Clinic for Food Animals and Horses, University of Berne, Switzerland, because of an acute severe lameness of the left rear limb. Clinical and radiographic examination revealed disruption of the stifle joint with rupture of both cruciate ligaments, the medial collateral ligament, and disruption of both menisci from their attachments. The ruptured ligaments were replaced by synthetic ligament prostheses. Long-term examination at 12 months after implantation revealed slight instability of the stifle joint, caused by degeneration of the medial meniscus, and signs of arthrosis deformans. The new formed periarticular connective tissue contributed to the stability of the stifle joint, so that a good functional result was achieved. Necropsy findings at 14 months after implantation confirmed that the synthetic ligament prostheses were intact and the medial meniscus was detached from its insertion and incorporated into the joint capsule. At microscopic examination of the synthetic band prosthesis, ingrowth of collagen and fibrous tissue was evident.

Animals↗
PubMed1996

[Differential diagnosis of resorptive tooth diseases and caries].

Feline Odontoclastic Resorptive Lesions (FORL, previously known as "neck lesions") on cat teeth are compared to caries and differentiated with the use of new methods. Radiological examination reveals typical odontoclastic resorptive processes, which take place at the dental root and at the periodontium. These lesions demonstrate the destruction on the desmodontium and the following ankylosing reaction. The rhodamine B stain which is selective for caries, stains regions which are softened by caries in a dark red way. Fuchsin/Acetic-Light Green stained histological preparations demonstrate the resorptive lacunae, resorptive lagoons and resorptive canals. Giant cells with multiple nuclei and reparative cementum can also be shown with the same stain. Hardness measurements using a Knoop diamond (KHN Knoop hardness number) give information about the degree of hardness of the different tissues. Electron microscopic investigations are performed to show the dentinal tubules and allowing the differentiation between FORL and caries. Since FORL also has been found in wild cats we deduced that alimentation has no effect on the pathogenesis of the disease.

Animals↗
PubMed1995

Bone apposition onto oral implants in the sinus area filled with different grafting materials. A histological study in beagle dogs.

The placement of oral implants into jaw bone has a high predictability provided an adequate bone volume surrounding the implant is present to ensure primary stability and resistance to functional loading forces after completion of osseointegration. In the distal area of the maxilla, an adequate bone volume is often lacking because of the proximity of the sinus cavities. The aim of this study was to evaluate histologically the simultaneous placement of endosseous implants into the sinus cavity and the surgical elevation of the sinus floor including filling the cavity with different grafting materials. In 9 sinus areas of 5 beagle dogs, 9 titanium implants (ITI Dental Implant System) were placed, and the void space of the sinus cavity was filled simultaneously with either demineralized freeze-dried human cortical bone (Musculoskeletal Transplant Foundation), resorbable hydroxyapatite (Osteogen) or natural cancelleous bovine bone mineral (Bio-Oss). To study bone formation, fluorochrome markers (tetracycline HCl and calcein green) were used at 2 and 8 weeks. Clinically, all implants healed uneventfully, and 5 months after implant placement the dogs were killed for histologic evaluation. All implants exhibited osseointegration within the pre-existing cortical bone of the sinus floor. The implants surrounded by freeze-dried bone xenografts yielded no formation of new bone, whereas the sites with hydroxyapatite or natural bovine bone mineral demonstrated newly formed bone with direct contact at the implant surface. The average extent of bone to implant contact was 25% (SD = 10.6%) and 27% (SD = 8.8%), respectively in relation to the length of the originally denuded implant surface.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

In vivo diagnosis of fissure caries using a new electrical resistance monitor.

The aim of this investigation was to study the accuracy of a newly developed electrical resistance monitor in diagnosing occlusal fissure caries in vivo in teeth without cavitation. The electrical resistance was measured in vivo on human third molars without existing restorations and without any macroscopic carious cavitation. Data from 41 sites on 26 occlusal surfaces were obtained. After measurement, the teeth were extracted, histologically prepared, and serially sectioned perpendicular to the occlusal surface and examined for the presence of caries. Nineteen sites had no caries, 7 had enamel caries, and 15 sites showed dentinal caries, 4 of which deep dentinal caries. For the diagnosis of occlusal caries with the electrical resistance monitor, the specificity was 0.77, the sensitivity 0.93, and the accuracy 0.83. Likelihood ratios for four diagnostic levels (no caries, enamel caries, dentinal caries, and deep dentinal caries) were 0.09, 0, 3.47, and 4.16, respectively. Diagnosis of occlusal caries using conventional bite-wing radiographs showed a specificity of 0.77, a sensitivity of 0.62, and an accuracy of 0.71. The electrical resistance monitor was well suited to detect in vivo occlusal caries under clinically intact fissures. The rather high value (0.23) of false-positive ratings, however, might lead to a substantial number of sound teeth being restored unnecessarily. Substantial improvement of occlusal, caries diagnosis may be achieved by combining this method with others.

Adult↗
PubMed1995

[Biocem--a new material for retrograde root filling. The 5-year clinical results].

This paper describes the application of a new material, Biocem, for retrograde root canal filling. A total of 234 roots in 222 teeth were treated during the period 1987-1992. Biocem consists of two components and once mixed, the autopolymerisation results in a three-dimensional structure. The biomechanical and histologic properties and a clinical longterm follow-up confirm the optimal qualities of this material. It fulfills the requirements in regard to biocompatibility, watertight sealing and application. The material proved superior in comparison to conventional materials and ceramics. The evaluation of the results are most encouraging.

Adolescent↗
PubMed1994

Histologic probe penetration in healthy and inflamed peri-implant tissues.

Periodontal probing is commonly used for assessing both the status of gingival health and the connective tissue attachment level around teeth. The role of probing around endosseous implants still remains unclear. The purpose of this study was to determine the histological level of probe penetration in healthy and inflamed mucosal tissues around implants. Five beagle dogs were used and a total of 30 one-stage, Titanium Plasma Spary (TPS)-coated implants of the ITI type were placed in the mandibles. After the healing period with meticulous oral hygiene, the dogs were divided into 3 groups: 1) clinical healthy mucosal tissues; 2) experimental mucositis (3 dogs); and 3) experimental ligature-induced peri-implantitis (2 dogs). Four months after implant placement, respectively 6 months in the third group, 60 probes were placed with a standardized force of 0.2 N and fixed at the mesial and distal aspects of the implants. Probing depth, clinical attachment level (CAL), Plaque Index (PlI) and Gingival Index (GI) were assessed throughout the study. Tissue sections were obtained for histometrical analysis. In the healthy group, the mean PII was 0.47, the GI 0.06 and the clinical probing depth (CPD) 2.12 mm. In the mucositis group the PlI was 1.61, the GI 1.61 and the CPD 1.87 mm. In the peri-implantitis group the PlI was 1.96, the GI 2.05 and the CPD 3.73 mm. The histologic results show that the probes were able to identify the connective tissue adhesion level in the healthy group with a mean error of -0.05 mm (mean histologic probing depth (HPD): 1.75 mm) and, in the mucositis group, with -0.02 mm (mean HPD: 1.62 mm). Probe penetration increased with the degree of inflammation and in the peri-implantitis group the probe exceeded the connective tissue level by a mean 0.52 mm (mean HPD: 3.8 mm). Therefore, probing around implants represents a good technique for assessing the status of peri-implant mucosal health or disease.

Animals↗
PubMed1992

Effectiveness of three cavity varnishes in reducing marginal microleakage of amalgam restorations: an in vitro study.

Dentin Adhesit, Cavi-Line and Kavite Lak cavity varnishes were applied to the walls of prepared Class V cavities in fifty-two caries free extracted molar teeth before placing amalgam fillings. Tests with Methylene Blue dye after thermocycling showed that all cavity varnishes showed significantly lesser marginal leakage when compared with the control group without any cavity varnish.

Dental Amalgam↗
PubMed1991

Influence of surface characteristics on bone integration of titanium implants. A histomorphometric study in miniature pigs.

The purpose of the present study was to evaluate the influence of different surface characteristics on bone integration of titanium implants. Hollow-cylinder implants with six different surfaces were placed in the metaphyses of the tibia and femur in six miniature pigs. After 3 and 6 weeks, the implants with surrounding bone were removed and analyzed in undecalcified transverse sections. The histologic examination revealed direct bone-implant contact for all implants. However, the morphometric analyses demonstrated significant differences in the percentage of bone-implant contact, when measured in cancellous bone. Electropolished as well as the sandblasted and acid pickled (medium grit; HF/HNO3) implant surfaces had the lowest percentage of bone contact with mean values ranging between 20 and 25%. Sandblasted implants with a large grit and titanium plasma-sprayed implants demonstrated 30-40% mean bone contact. The highest extent of bone-implant interface was observed in sandblasted and acid attacked surfaces (large grit; HCl/H2SO4) with mean values of 50-60%, and hydroxylapatite (HA)-coated implants with 60-70%. However, the HA coating consistently revealed signs of resorption. It can be concluded that the extent of bone-implant interface is positively correlated with an increasing roughness of the implant surface.

Animals↗
PubMed1991

Comparison of the sealing ability of four cavity varnishes: an in vitro study.

The purpose of this study was to test and to compare, in vitro, the sealing ability of four different cavity varnishes used to minimize the marginal leakage of amalgam fillings. For this purpose, a model was developed in order to avoid quality-deteriorating effects (such as condensation forces used during placement of amalgam) and temperature changes. In this model, raw ceramic disks were used instead of dentin. The four varnishes showed significant reducing effect on the penetration of the dye (Methylene Blue) compared with the control. There was no cavity varnish with optimal sealing.

Analysis of Variance↗
PubMed1991

Effects of the platelet-derived growth factor/insulin-like growth factor-I combination on bone regeneration around titanium dental implants. Results of a pilot study in beagle dogs.

The purpose of this study was to evaluate the early wound healing events of bone around press-fit titanium implants inserted with and without the concurrent application of a combination of platelet-derived growth factor (PDGF) and insulin-like growth factor (IGF-I). Nine months prior to implant placement all mandibular premolar teeth were extracted in 8 beagle dogs. Subsequently, 40 specially manufactured titanium implants with 2 transverse holes in the apical section were press fit into precise recipient sites in the dogs' mandibles. The dogs were sacrificed at 7 and 21 days following implant placement yielding 12 PDGF-B/IGF-I treated and 8 control (placebo gel or non-treated) implants for each observation period. Coded undecalcified sections were analyzed for: 1) percentage of implant surface in contact with new bone; 2) percentage of peri-implant space filled with new bone; and 3) percentage of implant hole filled with new bone. An analysis of variance was used to determine significant differences among the treatment groups. At 7 days, the percentage of bone fill in the peri-implant spaces and the percentage of implant surface in contact with new bone were both significantly increased in PDGF-B/IGF-I treated sites (P less than 0.01 for both groups). There was less than 1.5% fill of the implant holes in both treated and control sites (no significant differences). At 21 days the percentage of bone fill in the peri-implant spaces was significantly increased in the PDGF-B/IGF-I treated sites (P less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of Variance↗
PubMed1990

Titanium implants with a true periodontal ligament: an alternative to osseointegrated implants?

The purpose of the present study was to experimentally determine if cementum formation with inserting collagen fibers can be accomplished on dental implants. Titanium implants were placed in the mandible of monkeys, where apical root portions were retained. The histologic examination of undecalcified sections revealed that a cementum layer on the implant surface with inserting collagen fibers was achieved around implants placed in close relationship to retained roots; however, implants without contact to retained roots demonstrated the typical findings of osseointegration. These results demonstrate that dental implants with a true periodontal ligament can be accomplished.

Animals↗