Search PubMed⌕ Search

Biomedical subjects

R F Krejci

Publications and source records attributed to R F Krejci.

At least 19 recordsLinked to original sources
PubMed1989

Fiber optic probe augmented sonic scaling versus conventional sonic scaling.

Several factors, including access and visualization problems, make total deposit removal during scaling and root planing procedures extremely difficult. This study examined the effectiveness of a mode of therapy designed to improve access and visualization for sonic scaling compared to closed sonic instrumentation. Teeth with moderate to deep probing depths in six patients scheduled to receive immediate dentures were divided into three experimental groups: Group I, sonic scaling with access augmented by interdental papilla reflection and fiber optic illumination/transillumination (34 surfaces); Group II, closed sonic scaling (34 surfaces); and Group III, untreated controls (35 surfaces). Immediately after treatment the experimental teeth were extracted, stained with toluidine blue, and interproximal areas evaluated for remaining accretions with a microscope-digitizing pad-computer system. Group I had a significantly lower percentage (P less than 0.01) of remaining subgingival accretion coverage than Group II (1.30 +/- 0.25% vs 6.35 +/- 1.08%), and both Group I and II demonstrated significantly (P less than 0.01) fewer deposits than the control surfaces (46.61 +/- 4.32%). These findings suggest that minimal tissue reflection and fiber optic illumination/transillumination are beneficial adjuncts to deposit removal in moderate to deep periodontal pockets.

Coloring Agents↗
PubMed1988

Self-sterilization of the electrosurgery electrode.

Sterilization of the electrode used in electrosurgery has been assumed to occur at the instant of contact of the energized electrode tip to a grounded source. This study evaluated whether the time of electrode activation or the amount of energy delivered is important in the self-sterilization process. Standard bacteriologic culturing techniques were employed to assess sterility of the electrode tip following activation. Total time of application of the current and the energy used were recorded on audiotape and later tabulated. The data indicate that the time of energizing and the energy units used are critical in the sterilization of the electrode tip. These results confirm that self-sterilization of the electrosurgery electrode tip occurs, but full confidence is not realized with the time intervals commonly employed in clinical practice. The electrode tip must be considered a potential source of bacterial contamination of electrosurgically managed dental procedures.

Electric Conductivity↗
PubMed1987

Determination of plasma catecholamines in dogs after experimental gingival retraction with epinephrine-impregnated cord.

Blood catecholamine levels were determined by high-performance liquid chromatography after placement of the cord around two teeth in a random sequence of the following treatments: (1) untreated cord to intact gingival crevice (C), (2) epinephrine cord to intact crevice (E1), and (3) epinephrine cord to a crevice disrupted with a tapered diamond bur to simulate a subgingival procedure such as in crown preparation (E2). Each cord was left in place for 30 min while blood was drawn from the external jugular vein at 0, 5, 10, 20 and 30 min, and at 10 and 30 min after removal of the cord. Catecholamine values were compared to baseline (time 0) measurements. Treatment C resulted in no significant change in blood catecholamines. Treatment E1 caused a significant increase (p less than 0.01) in blood epinephrine levels, reaching a 641 per cent increase at 30 min. Treatment E2 produced a highly significant increase (p less than 0.001) in blood epinephrine with a greater than 5000 per cent increase 10 min after cord removal. Norepinephrine and dopamine levels were not significantly altered by any of the treatments.

Animals↗
PubMed1987

Histologic evaluation of gingival response to an electrosurgical blade.

Lateral heat production during the use of electrosurgical procedures in the oral cavity causes denaturation of the connective tissue adjacent to the incision line. This study evaluated the denatured zone following electrosurgery incision in dog gingiva with a traditional tungston wire electrode and a no. 15 surgical blade adapted for electrosurgery use. The effects of using a passive electrode during surgical procedures and using an "autosensor" circuit to control power adjustment were also evaluated. It was found that a surgical blade adapted for electrosurgery produces a zone of denatured tissue that is not statistically different from that produced with a wire electrode. Moreover, no differences were noted between incisions produced with manual power adjustment and those with power controlled by the "autosensor" circuit. A significantly wider zone of denatured tissue was produced when incisions were made without a passive electrode in place.

Animals↗
PubMed1987

Electrosurgery--a biological approach.

Electrosurgery has been used in dentistry for more than 50 years. Both opponents and advocates of electrosurgery have presented a variety of clinical studies in favour of their respective opinions, which are discussed in the following review. In some studies, wounds created by electrosurgical techniques were observed through the healing stages, in comparison to those following incision by a surgical blade, with no significant difference being discovered. Other studies reported that the histologic response of oral connective tissue to electrosurgery was adverse in some animal and human models. However, neither of these groups used methods that allowed documentation or control of operating variables. A critical evaluation of controlled clinical studies shows that adverse responses of (connective) tissue, epithelium, bone, cementum, and periodontal attachment are related to an excessive lateral heat production during the procedure. With electrosurgery, the clinician can control the inherent variables. Waveform, frequency, size of the electrode, time of contact and cooling periods are some of those considered to be of importance in the studies. On the basis of the research reports, clinical guidelines have been developed to give practical advice to the clinician using electrosurgery. Providing that these safeguards are adhered to, scientific evidence supports the biological compatibility of electrosurgery for intraoral surgical procedures.

Animals↗
PubMed1983

Lateral heat production secondary to electrosurgical incisions.

Adverse healing responses, including necrosis of soft tissue and sequestration of alveolar bone, have been reported following the use of electrosurgery for intraoral incisions. These responses are usually attributed to excessive heat accumulation during the surgical procedure. The purpose of this investigation was to measure temperature changes in subadjacent connective tissue during intraoral electrosurgical incisions in palatal mucosa of miniature swine. Results indicate that single electrosurgical incisions should be accomplished at a speed of approximately 7 mm. per second and that successive incisions should be separated by a cooling interval of 8 to 10 seconds to avoid generation of heat sufficient to initiate an adverse healing response.

Animals↗
PubMed1983

Subjacent heat production during tissue excision with electrosurgery.

A study was designed to document heat production subjacent to tissue excision by electrosurgery. In Phase I of the study, 20 electrosurgery excisions were made with a loop electrode in the palatal mucosa of miniature swine. Subjacent heat production was measured with implantation thermistors. Temperature measurements adjacent to 20 single incisions made with a needle electrode were used for comparison. Energy used and duration of active electrode contact with the tissue were recorded for each procedure with an electronic measuring device. In Phase II, 20 sets of excisions consisting of three successive excisions were performed. The following intraexcisional cooling periods were used for four sets each: 1 second, 5 seconds, 8 seconds, 10 seconds, and 15 seconds. Results indicate that single electrosurgery excisions with a loop electrode generate more energy than incisions made with a needle electrode. Subjacent heat production, however, is not significantly different. Cooling intervals of at least 15 seconds between successive electrosurgery excisions made with a loop electrode are necessary to prevent heat build-up of a magnitude capable of initiating destructive alveolar changes.

Animals↗
PubMed1983

Epithelial and connective tissue healing following electrosurgical incisions in human gingiva.

Electrosurgery is used for intraoral incisions by many clinicians. Much controversy surrounds the effect of lateral heat produced during the electrosurgical incision upon the healing of adjacent connective tissue. Ten electrosurgical incisions were made in the gingiva in each of five adult male volunteers. The duration of incision and actual energy production for each incision were calculated. Excisional biopsies of the incisions were obtained at 0-504 hours. At the light microscopic level, epithelium, totally degenerated immediately following the electrosurgery incision, showed extensive activity at 24-48 hours and had covered all wounds by 72 hours. Early hour specimens showed a homogenous connective tissue region, adjacent to the wound site, devoid of cells and fibers. This zone of denatured connective tissue gradually diminished until it was no longer present at 396 hours.

Adult↗
PubMed1983

Histometric evaluation of interproximal bone responses to electrosurgical mucoperiosteal incisions in dogs.

The periosteal and endosteal interproximal bone remodeling activity following clinically simulated blade and electrosurgical mucoperiosteal incisions was investigated by histologic and morphometric analyses. Undecalcified histologic sections were prepared and evaluated using standard bone morphometric techniques. Periosteal and endosteal bone surfaces subjacent to incisions were examined and the percentages of forming, resorbing, and quiescent surfaces, and the number of osteoclasts per millimeter of bone surface, were calculated. Based on indices of bone remodeling activity, the potentials for activation of interproximal bone remodeling by clinically appropriate blade and electrosurgery incisions in dogs appear to be similar.

Alveolar Process↗
PubMed1983

Dentin stresses in post-reconstructed teeth with diminishing bone support.

Dentin stresses from simulated functional loads to post-reinforced tooth models with four levels of periodontal support were calculated using finite element analysis. As bone levels diminished, stresses were found to increase dramatically and to concentrate in the small amount of dentin remaining near the post apex.

Alveolar Process↗
PubMed1983

Chronic mucogingival defects in miniature swine.

Controversy surrounds the importance of keratinized gingiva in maintaining periodontal health. A well-defined animal model system is necessary to evaluate longitudinally the role of keratinized gingiva when plaque control is inadequate or where dental procedures (restorative, prosthetic or orthodontic) alter the periodontal environment. Facial gingiva was excised from eight primary incisors in miniature swine. Contralateral teeth were used as controls. The experimental teeth exhibited mucogingival defects at 3 and 6 month observation periods. The secondary teeth erupting into the experimental regions also exhibited recession and chronic mucogingival defects. The marginal tissue in regions devoid of keratinized gingiva demonstrated clinical signs of inflammation. No progressive gingival recession was present. Excision of keratinized gingiva to produce mucogingival defects in swine provides a convenient model system for evaluating the effect of dental procedures on periodontal health where little or no keratinized gingiva is present.

Animals↗
PubMed1983

Effect of inflammation on periodontal attachment levels in miniature swine with mucogingival defects.

Previous authors have postulated that a dense band of keratinized, attached gingiva prevents the spread of inflammation from the gingival margin to the subjacent attachment apparatus. Chronically inflamed mucogingival defects were created over the vestibular surface of 12 central incisors in miniature swine. The untreated contralateral incisors were identified as paired controls. Placement of horizontal reference notches on the tooth surfaces was followed by measurement of Probing Depth (PD) and Probing Attachment Level (PAL) on the vestibular aspect of each experimental and control tooth. No plaque removal was accomplished at any time during the study. One year following the attainment of baseline data, all measurements were repeated. Results show an increase in PD and a loss of PAL in both experimental and control regions. No difference in increase of PD or loss of PAL between the groups could be discerned.

Animals↗