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Biomedical subjects

N Funduk

Publications and source records attributed to N Funduk.

16 recordsLinked to original sources
PubMed1991

Proton NMR spin grouping and exchange in dentin.

The nuclear magnetic resonance spin-grouping technique has been applied to dentin from human donors of different ages. The apparent T2, T1, and T1 rho have been determined for natural dentin, for dentin which has been dried in vacuum, and for dried dentin which has been rehydrated in an atmosphere with 75% relative humidity. All apparent spin relaxation has been analyzed for exchange between the spin groups in which the dentin protons exist; the analyses incorporate the results of selective inversion recovery T1 measurements which better probe the effects of exchange. The exchange analyses of the high fields and rotating frame spin-lattice relaxation have also been correlated to determine uniquely the inherent relaxation parameters of the proton spin groups constituting the dentin magnetization. The natural dentin contains protons on water, protein, and hydroxy apatite; these spins contribute 50%, 45%, and 5% to the total dentin proton magnetization, respectively. The water exists in three distinct environments, the dynamics of each environment has been modeled. In the natural dentin 30% of the water undergoes uni-axial reorientation. 52% of the water has similar relaxation characteristics to bound water hydrating a large molecule, and the majority of the remaining water acts as bulk water undergoing isotropic reorientation. The results are independent of the age of the donor.

Adult↗
PubMed1990

[Critical evaluation of an acrylic partial denture].

Removable partial denture with a rigid metal construction meets the three main requirements of the up-to-date prosthodontics, i.e. properly directed chewing forces through accurate proprioceptive control of the masticatory muscles and preservation of the healthy periodontal tissues. Because of its flexibility the acrylic partial denture does not fulfill the above mentioned criteria so it can be, except in particular clinical indications, considered as a temporary and transitional prosthodontic treatment.

Acrylic Resins↗
PubMed1990

[Partial denture components and principles of their design].

In comparison between acrylic and metal framework partial denture minor and reduced major connectors represent the main structural difference. Basic principles of design consider: an examination of the partially edentolous mouth, surveying of abutment teeth and analysing of forces, which act on the denture during its function. In the literature above all chewing (positive) forces and their leverage action upon partial denture are described. Beside positive, the article analyses also the problem of dislodging (negative) forces upon partial denture and design of stabilizing elements.

Dental Stress Analysis↗
PubMed1990

[Direct retention of the partial denture].

Direct retainers or clasps are the most demanding structural elements of the partial denture. Numerous clasps which are presented in the literature are divided into two main groups according to their design and function: clasps with occlusal approach (circumferential clasps) and clasps with gingival approach (vertical projection clasps). Number of clasps described in the article are satisfactory for creative design of all removable dentures in the partially edentolous mouth.

Denture Design↗
PubMed1990

[Designing of partial dentures with free end saddles].

Partial dentures with free end saddles, classified as K I and II present special design problems because of the different properties of tooth support and mucosa support. The main principle is that strait saddles are designed as tooth-born, however in curved saddles tooth and mucosa-born dentures are preferred. The article describes so called "altered cast" clinical and laboratory procedure which prevents rocking of the denture around the fulcrum line in patients with resilient alveolar ridge mucosa. Besides that some typical designs of partial dentures are presented.

Denture Design↗
PubMed1984

Composition and relaxation of the proton magnetization of human enamel and its contribution to the tooth NMR image.

The spin-spin, T2, and spin-lattice, T1, relaxation times and the magnetization of protons were measured in human enamel. The proton free induction decay was analyzed into solid-like interstitial water, enamel apatite, and semiliquid-like water components. The solid-like interstitial water was evaluated to be approximately 5 wt% and the semiliquid-like water to be approximately 1 to 2%. Neither in wet nor in dry natural enamel does the solid water exchange upon deuteration nor can it be extracted in vacuum. The semiliquid natural water, which is in the closed pores of the structure in the two samples above also remains unexchanged upon an 8 hr deuteration and cannot be extracted in a vacuum. With the lineshape-relaxation correlation NMR the free induction decays from heads and tails of the enamel rods were resolved. The solid-like water with T2 of approximately 14 microseconds and the apatite with a T2 of approximately 61 microseconds have T2's too short to be observed in an NMR zeugmatogram. Therefore only the semiliquid water component having an apparent T*2 of about 240 microseconds would contribute to the NMR image of human enamel. Since the relative intensity of this proton magnetization component in tooth is quite small the NMR image of tooth would show primarily the dentin and liquids within the tooth and on its surface.

Adult↗