Biomedical subjects

Thomas Bernhart

Publications and source records attributed to Thomas Bernhart.

9 recordsLinked to original sources

PubMed2006

Ninety percent success in palatal implants loaded 1 week after placement: a clinical evaluation by resonance frequency analysis.

To investigate the behaviour of early loaded palatal implants when observed with resonance frequency analysis (RFA). Twenty patients (seven males and 13 females, mean age 26.4 years) received one palatal implant each (length: 4 mm, diameter: 3.3 mm; Orthosystem) for maximum orthodontic anchorage. The implants' stability was observed by RFA. Measurements were carried out at the time of surgery, after first orthodontic loading and subsequently once a week over a period of 12 weeks. Two palatal implants were lost. The other 18 remained stable. The average period from insertion to first loading was 6.7+/-0.8 days. The mean orthodontic force applied was 272.2+/-73.2 cN. The implant stability quotient (ISQ) value at the time of surgery averaged 69.4+/-3.9. The mean ISQ value 6.7 days after insertion was 69.8+/-3.6. Twelve weeks post-surgery the mean ISQ value was 69.8+/-3.5. A statistically significant decrease in stability was observed after 2 and 3 weeks post-surgery (P=0.005 and 0.04). The behaviour of early loaded palatal implants showed an initial decrease of the ISQ values. From 6 weeks post-surgery onward the ISQ values increased. Within the limitations of this study, the results suggest that the healing time of palatal implants reported in the literature (12 weeks) should be discussed. An orthodontic loading of palatal implants 6 weeks post-surgery with a force up to 400 cN seems to be justified. Yet further investigations are necessary to evaluate the behaviour of early loaded palatal implants considering observation periods of over 12 weeks.

Adolescent↗

PubMed2006

Clinical study of horizontal alveolar distraction with modified micro bone screws and subsequent implant placement.

The aim of this study was to evaluate the clinical relevance of horizontal distraction osteogenesis (DO) with bone micro screws for reconstructing knife-edge alveolar crests before implant placement. Horizontal DO was performed in upper and lower alveolar crests of seven patients with resorption class IV according to Cawood and Howell. After osteotomy and a 1-week latency period, micro bone screws were reset daily for horizontal expansions by 0.5 mm. Dental implants were placed in the distracted area following a consolidation period of 12 weeks. Computer tomography was performed before DO and implant placement. Morphometric analysis showed a mean gain of 34.01 mm(2) (95% confidence interval [CI]: 10.55-57.48) in bone area and of 3.06 mm (95% CI: 1.81-4.31) in horizontal width, i.e. the horizontal dimension of the alveolus was approximately doubled within the first 5 mm of height. All 12 implants placed into the distracted area fulfilled the success criteria of stable osseointegration after 1 year of functional loading according to Albrektsson and colleagues. Despite the limited number of patients treated, data from the clinical study of horizontal DO with bone micro screws suggest that the generation of sufficient hard tissue in previously knife-edge alveolar crests for subsequent implant placement was possible.

Adult↗

PubMed2005

An innovative adhesive procedure for connecting transpalatal arches with palatal implants.

The aim of this presentation is to describe an innovative adhesive procedure for connecting palatal implants with transpalatal arches (TPAs). The steps required for completing the procedure, the costs involved and the requisite time were reviewed and compared with those of two alternative procedures reported in the literature. To establish the stability and reliability of the procedure in vitro, tensile stress tests were performed. The results were evaluated in view of a potential loss of anchorage and compared with reported data. The innovative adhesive procedure ensured a stable and precise connection between TPAs and palatal implants during a single visit in a chair-side time of 42 minutes. The costs incurred were euro 12.33. The composite-connected component parts resisted breakage up to a mean force of 3323.16 cN. Absolute stability of the TPA-palatal implant connection in terms of maximal anchorage was limited to a mean force of 408.05 cN at a wire strength of 0.036 inches.

Composite Resins↗

PubMed2004

Age-dependent changes of the periodontal ligament in rats.

Even after the end of the natural tooth eruption, there is a continuous renewal of the periodontal collagenous fiber system, depending on functional demands. The aim of this study was to analyse the age-dependent changes and regional differences of the collagen renewal rate of the periodontal ligament in healthy rats. The study was performed by autoradiography of the molars of rats aged 1, 8, and 18 months, where collagen was labelled by intravenously applied 3H-proline. After an 8-hour incorporation period, the animals were killed. For comparative examinations, molar roots were subdivided into cervical, middle, and apical thirds. Structural and quantitative analyses were performed by light microscopy and autoradiography, using an image-analysing computer-assisted operating unit that determined the 3H-proline-labelled collagen by photometry based on extinction measurement. With increasing age of the animals, the number of silver grains (3H-proline-blackened collagen) was reduced and the quantitative evaluation indicated a reduction of 3H-proline in the periodontal ligament. The lowest level of 3H-proline activities was observed in the middle, and the highest level in the apical root third, independent of age. All preparations revealed condensations of silver grains, which were located in the region of the periodontal ligament adjacent to the alveolar bone, but did not reveal any preferred position with regard to the dental topography. With progressive age, the uptake of 3H-proline in the periodontal ligament was reduced by about 20 to 30%, a result that corresponds to a decrease in collagenous fiber production. Collagen was mainly formed in the apical and cervical root third, starting from the alveolar bone side, presumably in response to functional strain.

Aging↗

PubMed2003

Representative marketing-oriented study on implants in the Austrian population. II. Implant acceptance, patient-perceived cost and patient satisfaction.

Oral implantology is an established subspecialty of restorative dental and oral surgery. While an extensive body of evidence on the fundamentals of osseointegration and associated factors has been published, marketing-oriented analyses based on representative public opinion polls of implant acceptance, patient-perceived cost and patient satisfaction are scarce. In this study, an attempt was made to address these points by questioning a representative sample of 1000 adults in the household setting. The interviewees were presented with 14 questions. Of those familiar with implants as one of the treatment alternatives, 61% reported they would accept implants if the need arose. Implant acceptance was highest among males and interviewees below the age of 30 years. The interest in implants increased with increasing family incomes. Four percent of those questioned already had implants. Twenty-five percent knew someone who had undergone implant treatment. All those questioned found implant-supported rehabilitation to be very expensive. Many of them blamed the dentists for the high cost. One detail was particularly evident: satisfaction among implanted patients was clearly higher than satisfaction rates perceived by them from what they were told about implants by others. First-hand experiences with implants proved to be less biased than reported second-hand information.

Adolescent↗

PubMed2002

Rectangular loops in inconsistent force systems: a laboratory investigation.

MATERIAL AND METHOD: [corrected] The force system delivered by the rectangular loop (R-loop) was the subject of this in-vitro investigation. The correction of a first-order irregularity was simulated in an inconsistent force system. Three types of R-loop made of 0.017" x 0.025" TMA wire but differing in length and insertion system were tested in a 3D strain gauge (Hottinger, Darmstadt, Germany). The buccal segment consisted of one molar and two bicuspids, with the first bicuspid as an active unit scheduled to be moved buccally into the dental arch. RESULTS: The first R-loop tested revealed too high a force magnitude to be recommended for clinical use. A loop connecting only two teeth and bypassing the second premolar delivered a favorable initial force of 85 cN with a drop of 20 cN per 1 mm deactivation. In order to achieve a translatory tooth movement, a buccal root torque must be bent in addition into the short horizontal leg of the R-loop. The use of a transpalatal arch is indispensable if adverse side effects are to be avoided.

Biomechanical Phenomena↗

PubMed2002

Chair-side procedure for connecting transpalatal arches with palatal implants.

The present investigation examined a chair-side procedure for connecting a transpalatal arch (TPA) with palatal implants, which does not involve any laboratory work. This new technique was compared with the standard procedure in terms of the number of steps, the time required, and the cost. The total chair-side time needed with the standard procedure was 38 minutes, with the material costs amounting to [symbol: see text] 159.6. With the chair-side procedure the total time required was 55 minutes, and the cost of the material totalled [symbol: see text] 34.1. The chair-side procedure was derived from orthodontic treatment concepts and is independent of laboratory input. Its major advantage is that it does not require transfers, which necessitate additional steps. These steps, which are inevitable with the standard procedure, resulted in an unexpectedly high cost level and increased the total cost. The difference in the cost of the material between the two procedures amounted to [symbol: see text] 125.5 and timewise the difference was 17 minutes. Whilst TPA-implant connections can be made with both the standard and chair-side procedures, the standard procedure, although taking considerably less chair-side time, was four times more expensive than the chair-side procedure.

Costs and Cost Analysis↗

PubMedDate not supplied

Influence of platelet-rich plasma on osseous healing of dental implants: a histologic and histomorphometric study in minipigs.

PURPOSE: In the present study the time course of local bone formation following the application of PRP during implant placement was evaluated histomorphometrically and histologically. MATERIALS AND METHODS: The mandibular premolars of 12 adult minipigs were removed surgically and 72 sites were prepared for implant placement. Before the implants (MK III, Replace, and MK III TiUnite) were placed, autogenous PRP (8 x 10(5) to 10 x 10(5) platelets/microL) was instilled into the host sites on the left side. The animals were sacrificed at 3, 6, and 12 weeks, and undecalcified ground sections were prepared. RESULTS: The histomorphometric evaluation showed significantly more bone-to-implant contact after topical PRP application in the early healing phase (6 weeks), which varied as a function of the distance from the implant surface (controls = 24.2% versus PRP = 44.21%; P = .013). At 12 weeks, the extent of osteoneogenesis was comparable in the 2 groups (controls = 51.3% versus PRP = 44.2%; P = .251). Statistical analysis revealed no significant interaction between implant surface type and PRP. DISCUSSION: Topical PRP application significantly increased the activity of bone regeneration at implant host sites during early healing. CONCLUSION: In the present study PRP was found to have a time- and site-dependent effect on peri-implant bone healing.

Analysis of Variance↗

PubMedDate not supplied

Nasal cavity perforation by palatal implants: false-positive records on the lateral cephalogram.

PURPOSE: Lateral cephalometric films were examined for their validity as a tool for the postoperative evaluation of palatal implant placement. MATERIALS AND METHODS: Cephalometric and histometric data of 20 partially edentulous human cadaveric maxillae were compared. Lateral cephalograms of the specimens were made, and the palatal complex was pencil traced. In addition, low-dose dental computerized tomography (CT) scans were obtained from every specimen. Based on the CT data, palatal implants (Orthosystem; Institut Straumann, Waldenburg, Switzerland) were placed. Postimplantation, another lateral cephalometric film was recorded. The specimens were prepared for histologic examination. The preoperative tracings were superimposed on the postoperative cephalometric films. RESULTS: Of 20 implants placed, 12 were 4 mm long and 8 were 6 mm long. The distance between the cranial end of the implants and the nasal floor on microscopy ranged from 0.3 to 9.3 mm. Perforation of the nasal floor was absent throughout on intraoperative probing, while 2 implants projected beyond the nasal floor on histologic analysis of the specimens. An analysis of the superimposed pre- and postoperative cephalograms showed 5 implants projecting beyond the nasal floor. Histologically, only 1 of these projecting implants had actually caused perforation of the palatal complex. A comparison between the histometric and the cephalometric data showed that cephalometry, on average, imaged the palatal complex 0.8 mm below the actual anatomic site. DISCUSSION AND CONCLUSIONS: Twenty percent of palatal implants projecting beyond the nasal floor were false-positive records on the postoperative lateral cephalograms. Despite CT scans, 10% of the implants placed caused fenestration of the nasal cavity by histologic evidence. If the palatal complex was perforated, intraoperative probing with a periodontal probe did not confirm the perforation. Bone perforations up to 1.3 mm did not necessarily result in frank perforation of the nasal mucosa. Two-dimensional images could not be related to actual penetrations into the nasal cavity.

Adult↗