Biomedical subjects

Manfred Wichmann

Publications and source records attributed to Manfred Wichmann.

At least 19 recordsLinked to original sources

PubMed2007

Influence of impression material and time on the 3-dimensional accuracy of implant impressions.

OBJECTIVE: To investigate, in vitro, the effect of time on the 3-dimensional accuracy of open-tray implant impression copings made of polyvinyl siloxane and polyether impression materials. METHOD AND MATERIALS: Reference models with 4 internal connection implants were fabricated. Four sets of 71 direct impressions were made with square impression copings using an open-tray technique. One set of impressions was made with polyether material (material A) and each of 3 polyvinyl siloxane materials (materials B, C, and D). Three-dimensional changes in spatial orientation of the implant analogs were measured over 48 hours using an optical measurement device. Deviation values were summed over 4 points and averaged per impression. Global differences were tested with a nonparametric Kruskal-Wallis test followed by pairwise comparisons using the Mann-Whitney U test. RESULTS: The mean dimensional accuracy of implant impressions significantly differed over time (P < .001). Materials A and B were found to produce comparable results, For materials C and D there was a significant increase in deviations, with a maximum increase at 2 hours. Deviations for material C were comparable to materials A and B at 48 hours. Baseline values were not maintained by any material. CONCLUSIONS: Within the limits of this in vitro study, it can be concluded that time cannot be neglected as a factor affecting the accuracy of implant master casts.

Dental Implants↗

PubMed2006

Evaluation of two different teaching concepts in dentistry using computer technology.

The common teaching goal of two different phantom head courses was to enable the students to provide an all-ceramic restoration by the means of computer technology. The aim of this study was to compare these two courses with regard to the different educational methods using identical computer software. Undergraduate dental students from a single year were randomly assigned to two different courses. One course was a conventional teacher-centred course [TRAD]. The other course contained problem-based learning (PBL) oriented structured modules [HYBRID]. The students completed an evaluation based on a 25 item seven-point Likert scale. Two independent evaluators assessed the practical work. Differences between TRAD and HYBRID were tested for significance using the Mann-Whitney U-test (at p < or = 0.05). Both courses were rated as demanding. The HYBRID group rated those items significantly better, which focused on course atmosphere and student-teacher relationship. The TRAD group felt that their course was more satisfying. Practical results of the two groups did not differ significantly. Within the limits of the study it was revealed, that the HYBRID group was less satisfied with the own success although the learning conditions were rated better. This could be interpreted in two ways: (1) the PBL oriented course lead the students to more self skepticism to their own work or (2) due to increased intellectual demands and the lack of detailed guidelines the course was felt as more burdening.

Attitude of Health Personnel↗

PubMed2006

Enhanced sympathetic cardiac modulation in bruxism patients.

Sleep bruxism, an oral parafunction including teeth clenching and grinding, might be related to increased stress. To evaluate sympathetic cardiac activity in bruxism patients, we monitored cardiac autonomic modulation using spectral analysis of heart rate variability and compared results to those of age-matched healthy volunteers. In bruxism patients, sympathetic cardiac activity was higher than in volunteers. The increased sympathetic tone suggests increased stress and might be related to occlusal disharmonies.

Adult↗

PubMed2006

Application of interim fixed reference points to maintain the occlusal vertical dimension: a technique for immediate loading protocols in the edentulous mandible.

This article describes a technique for the clinical insertion and use of specially designed screws as fixed intraoral reference and attachment points in implant dentistry. After insertion, these screws serve to stabilize radiographic and surgical templates in the completely edentulous patient. This approach provides the advantage of guiding maintenance of the correct occlusal vertical dimension and ensuring accuracy and stability during subsequent phases of treatment.

Acrylic Resins↗

PubMed2006

Rapid induction of hypnosis by finger elongation: a brief communication.

This clinical pilot study on finger elongation for induction of hypnosis attempts to determine whether the observed response is a hypnotic phenomenon or a simple physiologic reaction. Sixteen volunteers participated in the 5-phase study, which measured relative and absolute changes in the length of each finger prior to and after each phase. A distinctive elongation was statistically significant for the hypnosis condition. In addition, findings suggest changes in the metacarpus. Further investigation is indicated to shed light on this apparent phenomenon.

Fingers↗

PubMed2006

Neurophysiologic and long-term effects of clinical hypnosis in oral and maxillofacial treatment--a comparative interdisciplinary clinical study.

This prospective comparative clinical study evaluated the effectiveness of clinical hypnosis and its long-term effect in oral and maxillofacial treatment. A total of 45 highly anxious and nonanxious subjects were evaluated by subjective experience and objective parameters. Parameters were EEG, ECG, heart rate, blood pressure, blood oxygen saturation, respiration rate, salivary cortisol concentration, and body temperature. During and subsequent to the operative treatment, hypnosis led to a significant reduction of systolic blood pressure, and respiration rate and to significant changes in the EEG. The subjective values of the parameters evaluated existing anxiety mechanisms and patterns and possible strategies to control them, whereas the objective parameters proved the effectiveness of hypnosis and its long-term effect.

Anxiety↗

PubMed2005

Dentist-time expenditure for two different adhesive all-ceramic systems.

OBJECTIVES: The purpose of this clinical investigation was to compare a chair-side adhesive all-ceramic system to a laboratory processed adhesive all-ceramic system with respect to quality and time expenditure for the dentist. METHODS: The same dentist treated 10 patients, who were each to receive two large posterior single tooth restorations of similar location and extent. One restoration was made in the laboratory by using the IPS Empress system [LAB], the other one was done chair-side by utilizing the Cerec system [CHAIR]. The time expenditure was measured for [LAB] and [CHAIR] and compared by the Wilcoxon signed rank test. The restorations were also evaluated according to the USPHS criteria. RESULTS: The mean time expenditure for the dentist with low-level assistance was 111:03 min [S.D.+/-24:09 min] for [LAB] and 115:31 min [S.D.+/-15:54 min] for [CHAIR]. Time expenditure with medium level assistance for the operator was 100:53 min [S.D.+/-23:59] for [LAB] and 105:50 [S.D.+/-15:28] for [CHAIR]. Assuming a high level of assistance, the mean time values were 53:11 min [S.D.+/-14:29] for [LAB] and 54:29 min [S.D.+/-09:21] for [CHAIR]. The baseline investigation according to the modified USPHS criteria did not reveal any differences between [CHAIR] and [LAB]. CONCLUSION: There were no statistical significant differences with respect to time expenditure or quality between [LAB] and [CHAIR] in this study.

Aluminum Silicates↗

PubMed2005

Effect of surface treatment on the shear bond strength of three resin cements to a machinable feldspatic ceramic.

The aim of this study was to evaluate the shear bond strength of three resin cements to Vita Mark II ceramics under different pretreatments of the ceramic surface and to examine whether simplified pretreatment procedures would result in satisfying results compared to the state of the art. RelyX Unicem (RXU), Calibra (CAL), and Variolink II (VAR) were used as resin cements and bonded to machine milled feldspatic disks, pretreated in five different ways. (1) no pretreatment of the ceramic surface; (2) surface etched with hydrofluoric acid (HF); (3) ceramic surface silanized; (4) ceramic surface etched (HF) and silanized, (5) ceramic surface etched (HF), silanized, and covered with Heliobond. The shear bond strengths were measured initially, after 5000 and 10,000 thermocycles (TC). After 10,000 TC for CAL only procedure 5 resulted in a reliable adhesion median value of 10.7 MPa. VAR showed median values of 24.6, 17.2, and 18.1 MPa for pretreatments 5, 3, and 4, respectively. RXU performed 25.9, 22.0, and 11.0 MPa for procedures 5, 4, and 3, respectively. For procedure 2, RXU revealed the significantly highest value with 15.4 MPa (U-test, p = 0.05). Only RXU-luted specimens of procedure 1 survived the 10,000 thermocycles. The results revealed that a simplification of the ceramic pretreatment for VAR and RXU might be possible.

Adhesives↗

PubMed2005

Prosthodontic considerations for predictable single-implant esthetics in the anterior maxilla.

Long-term functional and esthetic success with implant-supported single-tooth restorations requires a comprehensive and interdisciplinary treatment approach. Important parameters include the initial clinical situation, the surgical approach, the provisional phase, and the choice of abutment material and design as well as the definitive restoration. This article presents the main aspects of current treatment protocols and discusses material options and clinical techniques to achieve predictable outcomes.

Adult↗

PubMed2005

"Hypnopuncture"--a dental-emergency treatment concept for patients with a distinctive gag reflex.

The present case report describes a newly developed dental treatment concept for patients with a distinctive gag reflex. "Hypnopuncture" is a combination therapy of hypnosis and acupuncture. Its simple, fast, and effective application autonomous of the cause makes it a valuable tool for dental-emergency treatment procedures. Physiologic and psychological aspects of gagging are influenced at the same time. The protocol is illustrated in the case of a 76-year-old patient with a severe gag reflex who was successfully treated by this combination approach. Necessary and effective therapeutic measures from both acupuncture and hypnosis are portrayed.

Acupuncture Therapy↗

PubMed2005

A long-term therapeutic treatment for patients with a severe gag reflex.

"Hypnopuncture," a combination treatment of hypnosis and acupuncture, provides a therapeutic treatment plan for long-term therapy for patients with a distinctive gag reflex. The treatment is applied independently of the cause. In cases of emergency treatment in dentistry, the immediate compliance of a patient is of utmost importance. The long-term goal of any therapeutic measure is control of the gag reflex. A new treatment protocol is illustrated in the case of a 50-year-old patient with a severe gag reflex. After only 5 visits, dental treatment could be conducted without any auxiliary means. Hypnosis is applied in the form of hypnosedation (not as psychotherapy), while stereognosis occupies a central position for desensitization.

Acupuncture Therapy↗

PubMed2005

Clinical fit of all-ceramic three-unit fixed partial dentures, generated with three different CAD/CAM systems.

In this study, the hypothesis was tested that the marginal and internal fit of CAD/CAM fabricated all-ceramic three-unit fixed partial dentures (FPDs) can be as good as in metal-ceramic FPDs. Twenty-four all-ceramic FPDs were fabricated and randomly subdivided into three equally sized groups. Eight frameworks were fabricated using the Digident CAD/CAM system (DIGI), another eight frameworks using the Cerec Inlab system (INLA). Vita Inceram Zirkonia blanks were used for both groups. In a third group frameworks were milled from yttrium-stabilized Zirconium blanks using the Lava system (LAVA). All frameworks were layered with ceramic veneering material. In addition, six three-unit metal-ceramic FPDs served as control group. All FPDs were evaluated using a replica technique with a light body silicone stabilized with a heavy body material. The replica samples were examined under microscope. The medians of marginal gaps were 75 microm for DIGI, 65 microm for LAVA and INLA and 54 microm for the conventional FPDs. Only the DIGI data differed significantly from those of the conventional FPDs. Within the limits of this study, the results suggest that the accuracy of CAD/CAM generated three-unit FPDs is satisfactory for clinical use.

Aluminum Oxide↗

PubMed2005

Implant-supported prosthetic treatment in cases with hard- and soft-tissue defects.

Tooth loss due to trauma or periodontal disease is often associated with extensive deficiencies of the supporting hard and soft tissues and atrophy of the alveolar ridges. The functional and esthetic predictability of an implant-supported prosthetic restoration in patients with extensive tissue augmentation is guarded, even when lost tissues were restored at an early stage by local ridge augmentation. The prosthetic reconstruction of major tissue defects is especially difficult, as lost structures of the alveolar ridge must be replaced by the restoration, which is expected to provide optimal function and esthetics, yet allow for optimal oral hygiene. This article presents prosthetic solutions for replacing missing hard and soft tissues with implant-supported fixed and removable restorations in cases of severe tissue deficiencies.

Dental Prosthesis, Implant-Supported↗

PubMed2004

Mechanical properties and three-body wear of veneering composites and their matrices.

Fatigue as one of the major factors affecting three-body wear of resin composites is influenced by mechanical properties of the resin matrix. The aim of this in vitro study was to determine three-body wear (ACTA methodology), fracture strength, and Young's modulus of four veneering composites (Artglass old and new formula, Vita Zeta LC Composite, Targis) and one direct restorative composite (Z 100). Furthermore, three-body wear of the pure matrices of the materials was tested. The wear results were compared to Amalgam as reference material. It should be computed whether there exists a correlation between the wear results of resin composite and matrix alone. Wear of the veneering composites was significantly higher than of Z100 (13 microm) and Amalgam (14 microm; p < 0.01, Mann-Whitney U-test). Mean fracture strengths of indirect composites ranged from 127.5 MPa (Targis) to 71.6 MPa (Vita Zeta LC). The elastic moduli of the composites were between 2.9 and 12.8 GPa. The matrix wear rates did not differ significantly. Three-body wear results of complex resin composites are highly influenced by their filler content, filler particle size distribution, kind of filler particles, shape, and their silanization to the matrix. Due to this fact, three-body wear testing is an essential testing method and cannot be replaced by testing single material components.

Composite Resins↗

PubMed2004

Clinical application of surgical fixation screws in implant prosthodontics--Part I: positioning of radiographic and surgical templates.

Proper implant position and angulation are fundamental for functional and optimal esthetic implant rehabilitation. This article describes the clinical application of surgical microfixation screws for stabilization and support of radiographic and surgical templates in edentulous patients. These screws provide fixed reference points for exact positioning of a diagnostic device.

Bone Screws↗

PubMed2004

Clinical application of surgical fixation screws in implant prosthodontics--Part II: Indexing implant position.

The accurate transfer of intraoral implant position to the definitive cast in situations of immediate implant loading in completely edentulous patients is an important step and may be difficult to achieve with common transfer and impression methods. Intraoral fixed points of reference accurately transferred to the definitive cast are necessary to provide precise and stable placement of radiographic and surgical templates during the presurgical diagnostic phase, during implant placement, and during fabrication of an immediate provisional restoration. This article describes a technique using surgical microfixation screws to provide fixed reference points and transfer the position of the conventional implants to the definitive cast.

Acrylic Resins↗

PubMed2004

Clinical performance of large, all-ceramic CAD/CAM-generated restorations after three years: a pilot study.

BACKGROUND: Adhesively luted all-ceramic restorations preserve and stabilize weakened tooth structure, but there is little published information about the clinical performance of large, all-ceramic restorations. METHODS: In this pilot study, the authors placed 58 large, single-tooth, all-ceramic restorations in 26 patients using a computer-aided design/computer-aided manufacturing, or CAD/CAM, system (CEREC 2, Sirona Dental Systems GmbH, Bensheim, Germany). They documented the maximum height of the restoration and remaining cementoenamel junction, or CEJ. In 21 cases, rubber dam isolation was not possible during adhesive luting. They re-evaluated the restorations after three years according to the U.S. Public Health Service criteria. RESULTS: After three years, the authors rated 56 (97 percent) of the 58 restorations as Bravo or better in regard to marginal integrity, secondary caries (four could not be rated), discoloration and anatomical form. One restoration was rated as Charlie because of poor marginal integrity, and one restoration had to be replaced owing to a bulk fracture. The authors rated the adequacy of proximal contact and occlusal relationships as acceptable-to-good for all restorations. Neither the extent of the remaining enamel at the cavity margin nor application of a rubber dam had any statistically significant influence (chi2 test, P > .05) on the clinical performance of the restorations after three years. CONCLUSIONS: At the three-year recall appointment, the authors found that the adhesively luted all-ceramic restorations had successfully repaired large coronal defects, irrespective of the cavity margin location (that is, coronal or apical to the CEJ). CLINICAL IMPLICATIONS: Tooth-colored, all-ceramic CAD/CAM-generated restorations are an alternative to conventional restorations if large coronal defects need to be treated.

Adolescent↗

PubMed2003

Imaging of periimplant bone levels of implants with buccal bone defects.

The aim of the present study was to use four different methods to evaluate three radiographic techniques for their accuracy in assessing the marginal periimplant bone levels at implants with buccal bone defects in an experimental setting. Twenty-four implants were placed in the mandibles of six adult beagle dogs with substantial buccal bone defects, which were augmented by bone particles with and without resorbable membranes. After healing for 5 months, (1) periapical radiographs, (2, 3) reformatted images in (2) sagittal and (3) coronal planes from axial computer tomography (CT) scans and (4) direct magnification images (DIMA) were made and compared with histometric analysis of bone levels. Two values were used for comparison: (i) the lingual bone level and (ii) the true bone level calculated as a mean value from the lingual and the buccal bone levels of all histologic sections of each implant. Metric evaluation of periapical radiographs, sagittal reformation of CT scans and DIMA showed that the results were close to the histometrically assessed lingual bone level, while the true bone level was significantly lower and not reflected by any of the imaging modalities. Coronal reformation showed that there was significant overestimation of the lingual and underestimation of the buccal bone level when compared with histometric values. It is concluded that assessment of bone level and bone regeneration in implants with buccal bone defects remains problematic, and data from periapical radiograms tend considerably to overestimate the bone anchorage of these implants.

Absorbable Implants↗