Papers by Dieter Bosshardt
PubMed, Mar 1, 1989
In the absence of data on the dynamics of cementum apposition, one female Macaca fascicularis mon... more In the absence of data on the dynamics of cementum apposition, one female Macaca fascicularis monkey, born July 1984 and sacrificed July 1985, was sequentially injected with calcein and xylenol orange 10 times, about every 33 days. Following fixation in formalin, the right and left maxillary and mandibular jaw segments were embedded in MMA and serially sectioned in the mesio-distal or bucco-oral directions, adapting the plane of sectioning to the various root axes. A total of 230 ground sections were produced. A selected set of sections then served for estimating the interval distances between the various lines of fluorescence and for calculating the daily rates of apposition of acellular and cellular cementum as well as of crown and root dentine of all deciduous and the first permanent molar teeth, using fluorescence microscopy and morphometric equipment. The resulting data were as follows: Acellular cementum formed at a rate of 0.10 +/- 0.02 microns/day, cellular cementum with initial rates of 0.4 to 3.1 and appositional rates of 0.1 to 0.5 microns/day. In comparison, crown dentine of the first permanent molar formed with a stable rate of about 3.1 microns/day, while the rate of root dentine formation varied from 4.6 to 2.7 microns/day in deciduous teeth, and from 2.2 to 3.2 microns/day in first permanent molars. Roots of deciduous teeth grew with an initial rate of 30 to 35 microns/day and this slowed down further apically to 10 to 14 microns/day. Roots of the first permanent molars formed with initial rates of 10 to 18 microns/day only.
Journal of Periodontology, Nov 1, 2005
Background: Root resorption is a multifactorial process that results in loss of tooth structure. ... more Background: Root resorption is a multifactorial process that results in loss of tooth structure. The causes of root resorption may vary, leading to several types of resorptions. Some factors have been identified and may be categorized into physiological resorption, local factors, systemic conditions, and idiopathic resorptions. The objective of this report was to present a case of a 17-year-old white female with progressive, generalized, apical idiopathic root resorption followed up for 34 months. Methods: Two panoramic radiographs, 14 and 34 months after initial clinical and radiological examinations, showed the rapid progression of apical root resorption. Two molars, teeth #15 and #16, which had to be extracted, and a bone sample from the distal aspect of tooth #15 were processed for histologic analysis. Results: Two millimeters apical to the cementoenamel junction, an abrupt increase in the cementum thickness was noted, amounting to 300 and 800 mm in teeth #15 and #16, respectively. The thickening of the cementum layer was due to an accelerated deposition of cellular intrinsic fiber cementum. An unusually high number of mineralization foci were observed in association with acellular extrinsic fiber cementum, and both free and fused cementicles were seen. In contrast to tooth #16, tooth #15 revealed extensive dentin replacement by a bone-like and a cementum-like tissue. Furthermore, ankylosis was demonstrated in tooth #15 and confirmed in the bone sample. Conclusions: At present, there is no preventive or therapeutic regimen for the type of root resorption seen in this case report. Treatment usually consists of the extraction of teeth with advanced lesions.
Clinical Oral Investigations, Aug 2, 2014
Objectives To histologically evaluate the effectiveness of a porcine derived collagen matrix (CM)... more Objectives To histologically evaluate the effectiveness of a porcine derived collagen matrix (CM) and a subepithelial connective tissue graft (CTG) for coverage of localized gingival recessions. Materials and methods Chronic single Miller Class I-like recessions were created at the buccal at the canines and at the third and fourth premolars in the upper and lower jaws of six beagle dogs. The defects were randomly treated with (1) coronally advanced flap surgery (CAF)+CM, (2) CAF+CTG, or (3) CAF alone. At 12 weeks, histometric measurements were made, e.g., between a reference point (N)and the gingival margin (GM)and the outer contour of the adjacent soft tissue (gingival thickness [GT]). The postoperative healing was uneventful in all animals. No complications such as allergic reactions, abscesses or infections were noted throughout the entire study period. All three treatments resulted in coverage of localized gingival recessions. The histological analysis failed to identify any residues of CM or CTG. The histometric measurements revealed comparable outcomes for N-GM and GT values for all three groups (CAF+CM: 1.04±0.69 mm/0.68±0.33 mm; CAF+CTG: 1.15±1.12 mm/0.76±0.37 mm; CAF: 1.43± 0.45 mm/0.79±0.24 mm). Conclusions In the used defect model, the application of CTG or CM in conjunction with CAF did not have an advantage over the use of CAF alone. Clinical relevance The use of CAF alone is a valuable option for the treatment localized Miller Class I recessions.
Clinical Oral Implants Research, Mar 9, 2015
Objective: To evaluate ridge preservation after ridge splitting with simultaneous implant placeme... more Objective: To evaluate ridge preservation after ridge splitting with simultaneous implant placement and guided bone regeneration (GBR) in a miniature pig model. In miniature pigs, the mandibular premolars and first molars were extracted together with removal of the interdental and buccal bone. Three months later, ridge splitting and expansion of the buccal plate were performed with simultaneous placement of two titanium implants per quadrant. On the test side, access by a mucoperiosteal flap followed by GBR with a biphasic calcium phosphate and a collagen membrane was performed. On the contralateral control side, a mucosal flap (MF), leaving the periosteum attached to the buccal bone, was elevated. After healing periods of 6 and 12 weeks, eight and four animals, respectively, were sacrificed for histological and histometric evaluation.
Clinical Implant Dentistry and Related Research, Apr 9, 2013
Background: Zirconia (ZrO2) has received interest as a dental material; however, little informati... more Background: Zirconia (ZrO2) has received interest as a dental material; however, little information is available on the impact of surface modifications on the osseointegration of zirconia implants.
Clinical Oral Implants Research, Oct 1, 2018
Annals of the Royal Australasian College of Dental Surgeons, Mar 1, 2010
PubMed, Aug 16, 2011
Purpose: This pilot study evaluated the wound healing and tissue response after placement of two ... more Purpose: This pilot study evaluated the wound healing and tissue response after placement of two different skin substitutes in subgingival mucosal pouches in rabbits. Materials and methods: Four rabbits were selected to receive a commercially available skin substitute consisting of a collagen matrix with fibroblasts and an epithelial layer (test membrane 1) and a prototype device consisting of a collagen matrix with fibroblasts only (test membrane 2). In each rabbit, two horizontal incisions were made in the buccal alveolar mucosa of the maxilla bilaterally to create submucosal pouches. Three pouches in each animal were filled with either the test 1 or test 2 membranes, and one pouch was left without a membrane (sham-operated control). All rabbits were sacrificed after a healing period of 4 weeks, and histologic samples were prepared and examined. Results: After a healing period of 1 month, both tested membranes were still visible in the sections. Test membrane 1 was still bilayered, contained inflammatory cells in its center, and was encapsulated by a thick fibrous tissue. Numerous ectopic calcifications were evident in the collagenous part of the membrane and in association with some basal epithelial cells. Test membrane 2 was also encapsulated in fibrous tissue, with inflammatory cells present only between the fibrous encapsulation and the remnants of the membrane. For test membrane 2, no calcifications were visible. Conclusions: Test membrane 1 seemed to be more resistant to degradation, but there was also a more pronounced inflammatory reaction in comparison to test membrane 2, especially in the vicinity of the keratinocytes. The significance of the ectopic calcifications, along with that of the resorption or degradation processes of both tested membranes, must be evaluated in future experimental studies, with different time points after implantation examined.
Elsevier eBooks, 2015
Implant dentistry is an interdisciplinary research field. Progress necessitates a strong relation... more Implant dentistry is an interdisciplinary research field. Progress necessitates a strong relationship between clinicians and basic scientists with an engineering or biology background. The three groups have to communicate to exchange experience, to explore ideas, and to develop research strategies. Fundamental to the communication is that the groups understand each other’s scientific language and basic expertise: the biological principle of osseointegration, implant technology, and surgical protocols. There is a potential demand for therapeutic stem cells and tissue engineering to replace soft tissue autografts for esthetic surgery. Particularly in the esthetic region, recessions of the oral mucosa and the concomitant visibility of the grayish titanium of the implants are treated by soft tissue transplantation. This procedure is also very common in restoring gingiva recessions around teeth. There is room for therapeutic stem cells and tissue engineering in dental implantology; however, it requires careful selection of the clinical indications when these strategies advance from an academic clinic to the general practitioner.
Journal of Anatomy, Nov 25, 2013
Histomorphometric evaluation of the buccal aspects of periodontal tissues in rodents requires rep... more Histomorphometric evaluation of the buccal aspects of periodontal tissues in rodents requires reproducible alignment of maxillae and highly precise sections containing central sections of buccal roots; this is a cumbersome and technically sensitive process due to the small specimen size. The aim of the present report is to describe and analyze a method to transfer virtual sections of micro-computer tomographic (CT)-generated image stacks to the microtome for undecalcified histological processing and to describe the anatomy of the periodontium in rat molars. A total of 84 undecalcified sections of all buccal roots of seven untreated rats was analyzed. The accuracy of section coordinate transfer from virtual micro-CT slice to the histological slice, rightleft side differences and the measurement error for linear and angular measurements on micro-CT and on histological micrographs were calculated using the Bland-Altman method, interclass correlation coefficient and the method of moments estimator. Also, manual alignment of the micro-CT-scanned rat maxilla was compared with multiplanar computer-reconstructed alignment. The supra alveolar rat anatomy is rather similar to human anatomy, whereas the alveolar bone is of compact type and the keratinized gingival epithelium bends apical to join the junctional epithelium. The high methodological standardization presented herein ensures retrieval of histological slices with excellent display of anatomical microstructures, in a reproducible manner, minimizes random errors, and thereby may contribute to the reduction of number of animals needed.
Oral Surgery Oral Medicine Oral Pathology Oral Radiology and Endodontology, Feb 1, 2011
Clinical Oral Implants Research, Oct 31, 2012
Objectives: To histologically assess the effectiveness of a porcine-derived collagen matrix (CM) ... more Objectives: To histologically assess the effectiveness of a porcine-derived collagen matrix (CM) and a subepithelial connective tissue graft (CTG) for the coverage of single mucosal recessions at osseointegrated dental implants. Materials and methods: Chronic-type mucosal Miller Class I-like recessions (mean clinical defect height: 0.67 ± 0.33-1.16 ± 0.19 mm) were established at the buccal aspect of titanium implants with platform switch in six beagle dogs. The defects were randomly allocated to either (1) coronally advanced flap surgery (CAF) + CM, (2) CAF + CTG or (3) CAF alone. At 12 weeks, histomorphometrical measurements were made (e.g.) between the implant shoulder (IS) and the mucosal margin (PM) and Results: All treatment procedures investigated were associated with an almost complete soft tissue coverage of the defect area (i.e. coronal positioning of PM relative to IS). Mean IS-PM and MT values tended to be increased in both CAF + CM (1.04 ± 0.74 mm/0.71 ± 0.55 mm) and CAF + CTG (0.88 ± 1.23 mm/0.62 ± 0.66 mm) groups when compared with CAF (0.16 ± 0.28 mm/ 0.34 ± 0.23 mm) alone. These differences, however, did not reach statistical significance. Conclusions: Within the limits of this pilot study, it was concluded that all treatment procedures investigated were effective in covering soft tissue recessions at titanium implants.
Cells Tissues Organs, 1994
Human premolars extracted for orthodontic reasons were fixed with a mixture of formaldehyde and g... more Human premolars extracted for orthodontic reasons were fixed with a mixture of formaldehyde and glutaraldehyde and processed for light and transmission electron microscopy. About 15% of all available teeth showed signs of superficial root resorption. Quantitatively, the resorption lacunae were more frequent at the apical third of the root, when compared to the mid-root and the cervical levels. Qualitatively, the resorption areas appeared as shallow irregular concavities. The degree of resorption and/or repair varied considerably both within and between sites, ranging from arrested resorption to advanced repair. An about 1- to 2-µm-thick seam of exposed collagen fibrils of the residual dentinal matrix lined the resorbed root surfaces in the arrested stage of resorption. A particular class of mononuclear cells repopulated these surfaces and commenced to attach newly produced collagenous matrix fibrils to the exposed dentinal matrix. Increasing fibril formation and bundling resulted in a collagenous fiber fringe oriented perpendicular to the bottom of Howship’s lacunae. Following the implantation and establishment of this initial fiber fringe, the junctional zone between the two matrices and further portions of the repair matrix became progressively obscured by a fine granular and electron-dense material, indicating the advancing front of mineralization. In addition, the junctional zone later attained a high degree of electron density and basophilia. Subsequently formed matrix derived from cementoblasts was structurally heterogeneous and resembled cellular intrinsic fiber cementum (CIFC). It is suggested that the initially produced matrix along resorbed root surfaces closely resembles that seen during initial formation of acellular extrinsic fiber cementum (AEFC), whereas further apposition results in a tissue with the characteristics of CIFC.
Clinical Oral Implants Research, Aug 1, 2006
Purpose: The purpose of this prospective study on humans were to evaluate (a) the clinical outcom... more Purpose: The purpose of this prospective study on humans were to evaluate (a) the clinical outcome of alveolar distraction osteogenesis for the correction of vertically deficient edentulous mandibular ridges, (b) the clinical outcome of dental implants placed in the distracted areas, and (c) the quality and quantity of the bone that had formed in the distraction gap.Material and methods: Seven patients presenting vertically deficient edentulous ridges were treated by means of distraction osteogenesis with an intraoral alveolar distractor. Approximately 3 months after consolidation of the distracted segments, 20 ITI solid screw SLA implants were placed in the distracted areas. Three to 4 months later, abutments were connected and prosthetic loading of the implants started. During implant site preparation, bone biopsies were taken at the implant sites with trephine burrs for histologic and histometric analyses.Results: The mean follow‐up after the initial prosthetic loading was 18 months (range 12–24 months). The mean bone gain obtained at the end of distraction was 7 mm (range 5–9 mm). The cumulative success rate of implants 2 years after the onset of prosthetic loading was 95%, whereas the survival rate of implants was 100%. The newly formed bone consisted of woven bone reinforced by parallel‐fibered bone with bone marrow spaces between the bone trabeculae. The bone area fraction in the distraction region ranged from 21.6% to 57.8% (38.5±11.7%).Discussion and conclusions: Results from this study showed that (a) distraction osteogenesis is a reliable technique for the correction of vertically deficient edentulous ridges, (b) the regenerated bone withstood the functional demands of implant loading, (c) survival and success rates of implants placed in the distracted areas were consistent with those of implants placed in native bone, and (d) there is sufficient bone volume and maturity in the distracted region for primary stability of the implant.
Clinical Oral Implants Research, Jan 14, 2015
Purpose: The aim of this systematic review was to evaluate clinical, radiological and histologica... more Purpose: The aim of this systematic review was to evaluate clinical, radiological and histological outcomes of the alveolar ridge splitting/expansion technique (ARST) with or without GBR. A screening of two databases MEDLINE (PubMed) and EMBASE (OVID) and hand search of articles were performed. Human and animal studies reporting on dental implants placed with simultaneous ARST up to May 31st 2014 were considered. Quality assessment of selected full-text articles was performed according to the ARRIVE guidelines and the Cochrane collaboration's tool to assess risk of bias. Results: Overall, 18 human and six animal studies (risk of bias: high/unclear) were included in this review. No randomized controlled trials were found. Due to the heterogeneity of study designs, definitions of success criteria, outcome variables, observation times and surgical procedures, no meta-analysis was performed. Reported survival (18 studies) and success (nine studies) rates ranged from 91.7 to 100% and 88.2 to 100%, respectively, with a mean follow-up of 1-10 years. Crestal bone level changes (ΔCBL) in some studies indicate slightly higher bone loss before and after loading. Histologic and histomorphometric data from six animal studies confirm the crestal bone loss, particularly at buccal sites. Conclusions: Within the limitations of this review, ARST seems to be a well-functioning one-stage alternative to extended two-stage horizontal grafting procedures. Data indicate that during healing and first year of loading, increased ΔCBL particularly at buccal sites must be anticipated. Additional horizontal GBR can help to preserve buccal bone height and width.
Journal of Bone and Mineral Research, Mar 1, 1997
Enamel and dentin at the cervical portion of the tooth are frequently covered by a collagen-free ... more Enamel and dentin at the cervical portion of the tooth are frequently covered by a collagen-free matrix referred to as acellular afibrillar cementum (AAC). It is believed that AAC deposition occurs when the enamel organ is displaced or disrupted, and mesenchymal cells from the dental follicle gain access to the tooth surface, differentiate into cementoblasts, and secrete noncollagenous proteins typically found in collagen-based mineralized tissues. A similar thin layer of mineralized matrix is found at the enamel-free area (EFA) of rodent molars, but in this case the matrix is covered by inner enamel epithelium (IEE) throughout development. We have, therefore, used this site as a paradigm to test the hypothesis that typical mesenchymal matrix proteins can also be found in association with epithelial cells. To this end, we have analyzed the presence and distribution of enamel-and cementum-related matrix proteins at the EFA and at the cervical portion of the tooth. Rat mandibular molars were processed for colloidal gold immunolabeling with antibodies to amelogenins, bone sialoprotein (BSP), osteopontin (OPN), osteocalcin (OC), and dentin sialoprotein (DSP), and the plasma proteins ␣ 2 HS-glycoprotein and albumin. The EFA matrix was immunoreactive for amelogenins as well as for BSP, OPN, OC, and ␣ 2 HS-glycoprotein, but not for albumin and DSP. The AAC was, similar to the EFA matrix, labeled for BSP, OPN, OC, and ␣ 2 HSglycoprotein. These data show for the first time that the EFA matrix is comprised of a mixture of enamel-and cementum-related proteins, a situation that parallels the distribution of matrix constituents at the cervical portion of the tooth. Since the EFA matrix is deposited on top of the mineralized dentin, and since the enamel organ seals off the forming matrix, it is concluded that EFA cells are responsible for the production of these proteins. Consistent with previous reports showing that epithelial cells can produce both BSP and OPN in some circumstances, the data also suggest that AAC may be deposited by cells of epithelial origin. Furthermore, they lend support to the possibility that cells derived from Hertwig's epithelial root sheath may likewise be capable of producing cementum matrix proteins. (
Key Engineering Materials, Nov 1, 2007
Alloplastic calcium phosphate (CaP) bone grafting materials, such as hydroxyapatite (HA) and tric... more Alloplastic calcium phosphate (CaP) bone grafting materials, such as hydroxyapatite (HA) and tricalcium phosphate (TCP), have been studied extensively due to their composition, which closely resembles the mineral component of bone [1]. HA has a Ca/P ratio of 1.67, which is identical to the inorganic phase of bone. In general, HA-based bone grafting materials are considered to be slowor even non-resorbable [2]. TCP, on the other hand, has a Ca/P ratio of 1.5, which equals the composition of the amorphous biological precursor to bone. In bone defects with high osteogenic potential, TCP is known to be substituted by newly formed bone at a high rate [2,3]. However, in more demanding defect morphologies, the rate of degradation may be too high to ensure sufficient space keeping capacity of the augmented volume [4]. HA and TCP combined in the same biomaterial is termed biphasic calcium phosphate (BCP) [5]. By changing the HA/TCP ratio, it has been possible to alter the substitution rate and the bioactivity of these materials [6], which has brought them to clinical use in oral and orthopedic surgery [5,7]. Over the years, it has become evident that different biomaterials with the same chemical composition may act very differently in both in vitro and in vivo studies due to differences in crystallinity, crystal size, micro porosity, macro porosity, pore size, and surface roughness [8-12]. Crystallinity is defined as the fraction of CaP engaged in a crystal lattice as opposed to the fraction present in an amorphous phase, and is believed to play an important role in protein adsorption, cell attachment, and dissolution of the biomaterials [13]. The crystal size is normally dependent on the temperature under which the CaP is sintered [11]. A higher sintering temperature creates larger crystals. The shape, size, and distance between the apatite crystals make up the micro porosity of the material (pores < 10 μm), which is important for the penetration and adhesion of macromolecules and tissue fluids [14]. The macro pores (pores > 100 μm), on the other hand, provide a scaffold for ingrowth of new blood vessels and attachment of osteogenic cells, with the prerequisite that these pores are interconnected as seen in native bone [8,15]. The total volume of the micro and macro pores defines the porosity. In synthetic CaP’s the porosity usually does not exceed 50%, because a higher porosity is reported to compromise the mechanical properties of the ceramics [9,16]. However, recent techniques have made it possible to develop materials with internal, interconnected connected porosities of 60-90% [15,17]. Key Engineering Materials Online: 2007-11-20 ISSN: 1662-9795, Vols. 361-363, pp 1241-1244 doi:10.4028/www.scientific.net/KEM.361-363.1241 © 2008 Trans Tech Publications Ltd, Switzerland
PubMed, 1992
As the interest in biological mechanisms of tooth eruption has recently been revived by a new eru... more As the interest in biological mechanisms of tooth eruption has recently been revived by a new eruption theory, the present study was an attempt to contribute new data to this problem. Four male Macaca fascicularis monkeys, two infant (about 13 months old) and two juvenile (about 44 months old), were labeled either by sequential fluorochrome or by single 3H-proline injections and then served for studying the bone apposition patterns around erupting premolars and molars. About 100 microns thick ground sections cut either in the mesiodistal or bucco-oral direction and the corresponding micrographs, microradiographs and autoradiographs, as well as fluorescence micrographs were used. In the multirooted teeth studied, bone apposition was most prominent and fast in the inter-radicular region, while at the fundus of the alveoli, bone apposition was slight or negligible. Around maxillary premolars and molars, bone apposition pointed in the mesial as well as in the axial direction. This was true for the intraosseous and the supraosseous phase of tooth eruption. Using these observations in addition to preliminary data calculated for the rates of bone apposition in the inter-radicular, apical and crestal regions, and for the rate of root elongation, the new eruption hypothesis could be extended. It is suggested that eruption of multirooted teeth, in the presence of corresponding coronal resorption, is entirely explained by forces generated through inter-radicular bone apposition and that their dental follicle is in a stimulating mode inter-radicularly but neutral apically at the bottom of the alveolar fundus.
International Journal of Periodontics & Restorative Dentistry, Nov 1, 2016
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Papers by Dieter Bosshardt