摘要:

The effect of limited drying or removal of the periodontal ligament upon periodontal healing after replantation of incisors was studied in green Vervet monkeys. All teeth were examined histologically either 2-, 4- or 8 weeks after replantation. The drying experiment demonstrated that an area of ankylosis was established after 2 weeks corresponding to the dried portion of the root and was removed by a resorptive process in the majority of cases after 8 weeks. The removal of the periodontal ligament led to development of surface-, inflammatory-and replacement resorption. Furthermore, 1 mm2and 4 mm2lesions on the root surface developed transient ankylosis which disappeared after 8 weeks, while lesions of 9 mm2or 16 mm2in size resulted in an ankylosis which, in most cases, persisted after 8 weeks. Based on these findings, it is postulated that physical removal or extended drying of the periodontal ligament initiates a rapid osteogenesis in the alveolus which establishes an ankylosis. If the damaged area is placed next to a zone on the root surface with a vital periodontal ligament, a later resorptive process is established from this zone, whereby the ankylosis area is gradually resorbed. It is estimated that the extent of this process in this experiment amounted to possibly 1–1.5 mm.

ISSN:0001-6357    

DOI:10.3109/00016358109162253

出版商:Taylor&Francis    

年代:1981

数据来源: Taylor

摘要:

The etiology of root resorption subsequent to replantation of incisors was examined in green Vervet monkeys. Cell damage to the root surface due to the extraction procedure was registered histologically 1 week after replantation. The topographical distribution of cell damage was then related to the development of root resorption in similar replanted teeth with longer observation periods. Histometric analysis showed that surface-, inflammatory-and replacement resorption was significantly related to certain topographical locations on the root surface. These surfaces represented the«corner»surfaces of the root, where the maximum damage presumably would occur during the extraction procedure. A positive and highly significant correlation between cell damage in the cementoblast layer and the presence of surface-, inflammatory-and replacement resorption was found: replacement resorption was associated with the greatest loss of vital cement-oblasts per unit root surface length. Furthermore, the distance from a potential resorption site to the nearest location on the root surface with a normal number of cementoblasts was found to be related to the type of root resorption. Thus, replacement resorption was found to be significantly related to the greatest distance from a site with normal numbers of cementoblasts compared to sites with no resorption or inflammatory resorption. Based on these findings, as well as previous experiments, a theory is presented for the etiology and pathogenesis of external root resorption after immediate replantation of mature teeth.

ISSN:0001-6357    

DOI:10.3109/00016358109162254

出版商:Taylor&Francis    

年代:1981

数据来源: Taylor

摘要:

Oxygen inhibits radical polymerization, and for the present investigation, the thickness of the resulting unpolymerized surface layer on various proprietary dental polymers was measured by a microscopic technique. The inhibition depth of the polymerized resins varied from 7 to 84μm. Resin systems with the tertiary aromatic amine 3, 4-xylyldiethanolamine as the activator had a thinner unpolymerized layer than those with p-tolyldiethanolamine. Increased viscosity also resulted in reduced thickness of the unpolymerized films. UV-light cured resins had thinner inhibited layers than those of comparable viscosity with a peroxide-amine initiator system. However, the thinnest unpolymerized film was seen with a chemically activated resin system containing acetone.This investigation has shown that the thickness of the unpolymerized film on cured dental resins is related to the composition and the initiating system.

ISSN:0001-6357    

DOI:10.3109/00016358109162255

出版商:Taylor&Francis    

年代:1981

数据来源: Taylor

摘要:

The ability of light-bodied elastomeric and reversible hydrocolloid impression materials to spread on a surface was studiedin vitro.The material which most readily coated the surface was a polysulfide, followed by silicone, hydrocolloid, and polyether materials. The influence of surface energy was studied by comparing the spreading of impression materials on high energy (glass) and low energy (PTFE) surfaces. Only for polysulfide and hydrocolloid materials was any effect observed: The glass was more readily coated than PTFE. As a result of an increase in temperature of the elastomeric materials a reduction in the materials' ability to wet the surface was found for silicones and polysulfide, but not for polyether. An addition-polymerized silicone product showed the strongest temperature dependence. A strong negative correlation was found between spreading ability and viscosity of elastomeric materials.

ISSN:0001-6357    

DOI:10.3109/00016358109162256

出版商:Taylor&Francis    

年代:1981

数据来源: Taylor

摘要:

An investigation was conducted to determine the clinical adhesiveness of some commonly used dental materials. Contact angle measurement data, obtained under clinical conditions, were used to calculate thein vivo-critical surface tensions for enamel, gold, stainless steel, and a resin polymer. The results of this study showed that the adhesive properties of the artificial surfaces studied were considerably modified in the oral environment. Thus, after two hours these solids with diverse original surface chemistries were observed to producein vivo-critical surface tensions common to those recorded for enamel. The observed changes were attributed to be adsorbed biofilm (acquired pellicle), which forms on all solid surfaces in the oral cavity.

ISSN:0001-6357    

DOI:10.3109/00016358109162257

出版商:Taylor&Francis    

年代:1981

数据来源: Taylor

摘要:

The clinical adhesiveness as expressed by the critical surface tension and roughness of an acid etched tooth surface was studied as a function of time; from time of acid»conditioning«and at selected time intervals up to seven days.The critical surface tensions of the tooth surface were calculated from clinical contact angle measurements as were values for change in roughness. SEM micrographs of the surfaces were obtained for visual comparisons.The results indicate that the surface of the tooth returns to its orginal state of adhesiveness and roughness in a relatively short period of time as a consequence of the adsorption of a biofilm, the acquired pellicle.

ISSN:0001-6357    

DOI:10.3109/00016358109162258

出版商:Taylor&Francis    

年代:1981

数据来源: Taylor

摘要:

In an attempt to find an explanation for an experimentally found strong connection between the extension of the loaded area and the load required for fracture, an analysis of the diametral compression test was carried out by means of the finite element method. The distribution of the stresses in a quadrant of a circular specimen section was studied for varying contact surface but at a given load distribution within this surface. Below a limit value for the width of the contact surface tensile stresses appeared peripherically outside the contact area, which had a magnitude exceeding those stresses which are centrally located and should normally initiate fracture. For that reason, peripherical fracture initiation must be regarded as a possibility. Only marginal importance could be attached to changes in the extension and magnitude of the central tensile stresses, as compared with the potential impact of the peripherical tensile stresses.

ISSN:0001-6357    

DOI:10.3109/00016358109162259

出版商:Taylor&Francis    

年代:1981

数据来源: Taylor