bluuebunny/crossref_metadata_2025_split huggingface dataset:
Some properties of dental ceramics
Authors: JONES DEREK W. , WILSON H. J. 
Published: June 2007

SummaryThe rather exacting aesthetic requirements of dental restorations has largely dictated the composition of dental ceramic materials. The so‐called dental porcelains have evolved from the traditional whiteware formula of feldspar, clay and quartz. One of the first variables which might be considered is that of chemical composition. It is, however, generally accepted that for ceramic materials small variations in composition are not critical. Since the early work of Watts in 1918, little interest has been expressed in the chemical composition of dental porcelain.The composition of traditional dental porcelains has evolved over a period of many years by practical trial and error, as discussed by Jones (1971). The development of dental porcelains advanced to the point where any major improvements in physical properties could only be achieved by major changes in composition and technique as advocated by McLean & Hughes (1965). The resulting alumina/glass composites which have been developed use a technique which involves the build up of an inner core which contains a high proportion of crystalline alumina (45–50 %) embedded in a glass matrix surrounded by a transparent outer veneer.This work compares the effect of such inter‐related variables as composition, inclusion of filler, viscosity, texture, hardness, and strength of the fired product.
A two‐year clinical study comparing the effect of dentifrices on selected dental materials
Authors: SCHIFF THOMAS , VOLPE ANTHONY R. 
Published: June 2007

Summary

A two‐year double‐blind human clinical study has been conducted to determine the comparative effect of two commercially available dentifrices on selected dental materials.
Forty‐three adult subjects were selected to participate. They received either acrylic resin or silicate restorations in their anterior teeth, or a full cast gold veneer crown with an acrylic surface.
The subjects were randomly assigned to either one of the two dentifrices and utilized the dentifrice in their normal manner at least 3 times per day.
The dental restorations were clinically evaluated in reference to their surface characteristics immediately after placement, and after 3, 6, 12 and 24 months' use of the dentifrices. The acrylic surfaces of the veneer crowns were also evaluated at these same time periods; however, in this case an in vivo tooth surface reflectance measurement technique was also utilized.
The results of this clinical study provide the following conclusion after 24 months use of the two dentifrices: There was no difference between the two dentifrices in that neither dentifrice produced any abnormal or unusual effect on the surface characteristics of either the acrylic or silicate anterior restorations, or the acrylic surfaces of the veneer crowns.
Utilization of electrical conductivity as an alternative method of assessing marginal leakage of pit and fissure sealants
Authors: MARTINEZ C. R. , GREENER E. H. 
Published: June 2007

SummaryThe electrical conductivity readings of extracted human teeth were taken: prior to placement of pit and fissure sealants; immediately after placement of the pit and fissure sealants; 2 weeks after immersion of the specimens in distilled water at 37°C; and after 7200 strokes on a toothbrushing machine. The specimens were then immersed in dye for 24 h, sectioned and evaluated for evidence of dye penetration.The electrical conductivity readings were then compared to dye penetration results to determine if a correlation existed.A positive correlation existed between the electrical conductivity readings and dye penetration. Threshold values of electrical conductivity existed (which varied for each sealant)—readings above these threshold values indicated sealant failure or leakage.The possibility of using electrical conductivity as a diagnostic tool is definitely worthy of further research—particularly its potential as an in vivo method of assessing leakage.
Lateral displacement of the mandible in Rhesus monkeys
Authors: BLANKENSHIP JOHN R. , RAMFJORD SIGURD P. 
Published: June 2007

SummaryLateral displacement of the mandible was induced experimentally in five adult male Rhesus monkeys. Following from 2½2 weeks to 19 months, the animals were sacrificed and examined histologically. Two of the monkeys received H3 proline 4 months prior to sacrifice and radioautographs were prepared. The lateral displacement apparently caused great discomfort because the monkeys refused to eat and lost weight rapidly for a few months. After about 12 months, the monkeys could again eat their normal diet to the extent they started to gain weight slowly.The histological and radio‐autographic findings indicated almost no changes of the articular surfaces of the temporomandibular joints. However, extensive reorganization of the neck of the condyles was observed. Severe periodontal trauma and extensive movements of the teeth occurred in spite of the fact that the teeth in each jaw were splinted firmly together.
Quantitative changes in dental plaque formation related to removable partial dentures
Authors: EL GHAMRAWY ESSAM 
Published: June 2007

SummaryPlaque formation on forty‐four teeth acting as abutments for removable partial dentures was studied while the patients were wearing their dentures and while they were not. The amount of plaque was assessed according to Quigley & Hein (1962), modified by Kardel & Bay (1967). In addition, that formed occlusally was evaluated by an occlusal plaque scoring index designed for the present study.It was found that the wearing of partial dentures increased the formation of plaque on all tooth surfaces under investigation.
In vitro attachment of Streptococcus sanguis to dental crown and bridge cements
Authors: ØRSTAVIK DAG , ØRSTAVIK JON 
Published: June 2007

SummaryThe ability of a common dental plaque bacterium, Streptococcus sanguis, to adhere to dental crown and bridge cements in vitro was investigated. Cylindrical blocks of five different commercial brands of cement, with and without acquired pellicles, were incubated with buffer suspensions of S. sanguis for 1 h. Attached bacteria were counted under the microscope. S. sanguis had particularly high affinity for uncoated resin cement. In contrast, the carboxylate cement tested was a poor substrate for the adherence of this bacterium. The other cement types (zinc phosphate, zinc oxide and silico‐phosphate) had intermediary qualities as adhering surfaces.The presence of an acquired pellicle, obtained by pretreatment with saliva, influenced the initial adherence of bacteria to cement in vitro. On the resin cement a salivary pellicle strongly suppressed the bacterial adhesion. For the zinc phosphate, zinc oxide and silico‐phosphate cements a pellicle slightly enhanced the attachment of S. sanguis. On the carboxylate cement only few organisms attached also after pretreatment with saliva.
Linear dimensional changes during setting of two polycarboxylate cements
Authors: ØILO GUDBRAND 
Published: June 2007

SummaryThe linear dimensional changes of two polycarboxylate cements have been studied. The measurements were performed on specimens placed on a mercury bath, and were started 3 min after commencing the mix. The specimens were allowed to set at 37°C under various environmental humidity.Specimens from one of the polycarboxylate cements (Durelon®), were made using both the universal liquid and the thin liquid meant for cementation. The powder/ liquid ratios (P/L) were either 2.5 or 1.5.Specimens from the second cement (Poly‐C®), were made using the liquid meant for cementation only with a P/L of 1.5.The dimensional changes of Durelon were dependent on the powder/liquid ratio and the environmental humidity during setting. Under dry conditions this cement showed a maximum contraction of 4.60% after 14 days when a high P/L was used and 6.10% when a low P/L was used. After 1 day under wet conditions no significant differences between cements with high and low P/L were registered, and the mean contraction was 1.10%.The dimensional changes of Poly‐C were dependent on the environmental humidity, and after 14 days under dry conditions a maximum contraction of 5.50% was registered and after 1 day under wet conditions a contraction of 0.60%.The contraction of the polycarboxylate cements tested in this study started earlier and were in general more pronounced than that observed for a zinc phosphate cement (Øilo, 1975).
Periodontal conditions in patients 5 years following insertion of fixed prostheses
Authors: VALDERHAUGW J. , BIRKELAND J.M. 
Published: June 2007

SummaryThe oral hygiene, gingival condition, pocket depth and loss of attachment were studied during a period of 5 years in a group of patients (114) who had been treated with fixed dental protheses. Eighty‐four per cent of the subjects had received periodontal therapy prior to the prosthetic treatment. During the study the subjects participated in an oral hygiene programme.Crown margins were located sub‐gingivally, at the gingiva, and supra‐gingivally. Initially 65% of the crown margins were sub‐gingival compared to 41% 5 years later. When the crown margins were located sub‐gingivally there was an increase in Gingival Index scores 2 and 3, in pocket depth, and in loss of attachment compared to a supra‐gingival placement. However, most of the alterations were small.
The use of root abutments in the support of complete dentures
Authors: RALPH J. P. , MURRAY F. D. 
Published: June 2007

SummaryA clinical study of the use of root abutments as an aid to the support of complete dentures is presented. This technique offers a realistic alternative for patients who are reluctant to face the loss of their remaining natural teeth and the wearing of complete dentures. The abutments enhance the support and stability of the dentures and appear to slow the rate of alveolar resorption. The clinical procedures are straightforward and can be readily applied in general dental practice.
The effect of anodic polarization on the tensile strength of dental amalgam
Authors: WANG CHEN C. P. , GREENER E. H. 
Published: June 2007

SummaryThe effect of corrosion upon dental amalgam was studied by measuring the effect of anodic polarization on its tensile strength. A conventional tensile testing method using dumb‐bell shaped specimens deformed along the long axis was employed. The results showed a significant reduction (27%) in the mean tensile strength, due to the anodic polarization of conventional amalgam, whereas the strength of the high Cu‐containing Dispersalloy amalgam was unaffected by polarization. When the diametral tensile strengths of polarized and unpolarized conventional amalgam and Dispersalloy specimens were compared (ADA Specification No. 1), no significant difference in strength was observed.These results indicate that the anodic corrosion of γ2 phase network in the conventional amalgam fillings can be directly attributed to a reduction of tensile strength which would be manifested clinically as marginal breakdown. It appears also that the diametral tensile test is not sufficiently discriminating to allow for an in vitro simulation of clinical properties.
Cytotoxicity of temporary crown and bridge materials
Authors: DAHL BJøRN L. , øRSTAVIK JON 
Published: June 2007

Summary In vitro cytotoxicity of freshly prepared temporary crown and bridge materials was studied using mouse fibroblasts prelabelled with 3H‐thymidine grown in shake flask cultures. Cytotoxicity was measured as (1) lack of cell multiplication, (2) stainability with Trypan blue and (3) release of 3H‐labelled material to the culture medium. All the materials tested (zinc oxide‐eugenol cement (ZOE), Scutan® and Sevriton®) were cytotoxic in this system, ZOE most strongly. This finding favours the view that the in vitro cytotoxicity of dental materials should not be used alone as a screening test for their biological compatibility under clinical conditions since clinical experience and previous in vivo findings have established that ZOE is biologically well tolerated by the dental tissues.
The effect of the bite plane splint on the electromyographic silent period duration
Authors: BEEMSTERBOER P. L. , McNAMARA D. C. , HOLDEN S. , ASH M. M. 
Published: June 2007

SummaryAn electromyographic study of the masseter and anterior part of the temporalis muscles was performed on ten patients presenting temporomandibular joint dysfunction symptoms. The EMG silent periods (SP) produced in the open‐close‐clench cycle and jaw‐jerk reflex were compared for duration before and after treatment with an occlusal bite splint. Following use of the splint, there was a shortening of SP indicating the possible use of the duration of SP as a diagnostic measurement, and also as an indication of treatment effectiveness.
Microstructural changes of dental amalgam by copper additions
Authors: MARSHALL G. W. , FINKELSTEIN G. F. , MARSHALL S. J. , GREENER E. H. 
Published: June 2007

SummaryThe γ2 (Sn7–8Hg) phase of the amalgam structure has been established as the most corrosion prone of conventional dental amalgam. Cu rich amalgams are currently of interest because some formulations appear to reduce or eliminate the γ2 phase. This investigation compares the microstructures of conventional amalgam to Cu rich amalgams prepared by various methods, i.e. a commercial alloy (Dispersalloy), an admixture of Cu amalgam with conventional amalgam, and admixtures of 30% Cu‐Ag‐Sn ternary alloy with conventional amalgam.These variations in amalgam formulation resulted in marked reduction or elimination of the γ2 phase in the Cu rich amalgam microstructures. The matrix or γ1 (Ag2Hg3) phase was common to all formulations. Other phases and their proportions changed dramatically with different methods of introducing the Cu.The saline corrosion resistance, determined by potentiostatic anodic polarization in Ringer's solution, was enhanced for the Cu rich amalgams as a result of the elimination of the γ2 phase. This study suggests there are a variety of methods to introduce copper into amalgams and that these methods generally serve to eliminate γ2 phase and increase saline corrosion resistance.
A galvanic study of different amalgams
Authors: CHEN C. P. WANG , GREENER E. H. 
Published: June 2007

SummaryDue to the difference in open circuit potential (OCP) versus SCE for Aristaloy* amalgam (‐969 mV) and Dispersalloy† amalgam (‐549 mV) in Ringer's solution at 25°C, a galvanic cell was created with Dispersalloy amalgam as cathode and Aristaloy amalgam as anode.The galvanic corrosion current was studied as a function of time for the above cell as well as for a cell of type III dental gold‡ (OCP is +0·5 mV) versus Aristaloy amalgam. The initial corrosion current of the latter cell (105 μA) is about twice that for the cell of aristaloy amalgam versus Dispersalloy amalgam (54 μA), however, their passivating behaviour is quite similar.Also, an interrupted galvanic corrosion test simulating the oral ‘make and break’ situation was performed. A much higher corrosion current than the steady state was found when the two electrodes resumed contact.
Reconstruction of alveolar ridge and jaw defects resulting from gunshot wounds
Authors: SANDERS BRUCE 
Published: June 2007

SummaryReconstruction and rehabilitation of acquired defects of the oral cavity is an important dental service. Severe deformities of the jaws may result secondary to gunshot wounds of the oral‐facial region. New advaces in soft and hard tissue surgical reconstruction can be of great benefit to the patient when coupled with prosthetic rehabilitation.In recent years there has been a significant increase in the incidence of gunshot wounds in the civilian population in the United States, and those of the mouth and jaws are relatively common‐place.Gunshot wounds to the face and jaws may cause gross destruction of tissues. Although immediate definitive treatment of wounds reduces the mutilating effect, a significant number of patients require extensive reconstructive procedures. In addition, prosthetic rehabilitation is almost always needed.The purpose of this paper is to briefly review some recent advances in reconstruction of the maxilla and mandible following gunshot injuries.
An application of potentiostatic current ‐time transients to study the corrosion of dental amalgams*
Authors: SARKAR N.K. , GREENER E. H. 
Published: June 2007

AbstractPotentiostatic current‐time transients obtained during anodic polarization of a conventional dental amalgam and its component phases have been analysed to characterize the possibel electrochemical reactions involved in amalgam corrosion. These reactions involve such surface phenomena as adsorption, anodic film formation, film dissolution, etc. which are well reflected in current time transients. The analysis of these transients from the standpoint of thermodynamics, suggests that the saline corrosion of dental amalgam may occur through the dissolution of the passive anodic films on Sn7Hg (γ2) and Cu6Sn5 (η′) and the dissolution reaction appears to be the formation of tin‐oxychloride.
Bruxism and its effect on the teeth
Authors: XHONGA FRIDA A. 
Published: June 2007

SummaryThis study presents the progress of tooth wear and the change in structural morphology on individual teeth of bruxist subjects, compared with non‐bruxers. From the results of this investigation it can be concluded that the tooth wear progressed faster in bruxers than in non‐bruxers. Scanning electron microscope investigations revealed in 10 teeth the same pattern of deep grooves and striations on the wear‐facets of active bruxers.
Aspects of functional improvement after treatment of a pain dysfunction patient
Authors: HONÉE G. L. J. M. , DE VRIES J. H. 
Published: June 2007

SummaryFirst results of an investigation of several aspects of the function of the chewing apparatus by means of optical‐electric movement scanning, EMG and occlusal sound registration on one time base, are presented. Observations made on a patient with pain‐dysfunction syndrome before and after treatment has been compared with observations made on a healthy subject. It has been suggested that the method used, may be of value for objective evaluation of functional improvement and analyses of several aspects of the physiology of the chewing apparatus.
Assessment of the quality of restorations
Authors: ELDERTON R. J. 
Published: June 2007

SummaryMost assessments of the quality of restorations are entirely subjective and involve standard clinical diagnostic equipment. However in recent years there has been an increasing demand for more accurate and reliable methods. Attempts to achieve these have been directed mainly towards the standardization of clinical judgements by the provision of various systems of guidelines of criteria upon which to base them. While these have improved the usefulness of the assessments, they have remained largely subjective. Furthermore, the efficacy of using the particular criteria selected are themselves open to questioning.By the use of more complex methods of examination, often in the field of restorative materials research, assessments have been made of various features of restorations and a body of knowledge concerning factors that might influence or manifest their quality has been built up. However the true significance of much of this knowledge in terms of the clinical behaviour, and thus the finite quality of restorations in service, has yet to be established, for many of the studies have been undertaken in isolation from the dynamic conditions of function in the mouth. Notably, however, a few objective clinical studies have been carried out and objective measurements of some factors affecting the quality of restorations have been reported.
Kinematics of the tooth tapping movement
Authors: WIDMALM SEVEN‐ERIK , HEDEGÅD BJÖRN 
Published: June 2007

SummaryElectrical activity in the masseter muscles and tooth contact vibrations were recorded simultaneously from subjects tapping their teeth slowly into maximal intercuspidation and again with maximal frequency. High speed cinephotography was also used with four of the ten subjects.Three main parts could be distinguished on the obtained graphical representation of the tooth tapping movement: tooth contact phase (TCP), opening phase (OP) and closing phase (CP).Tapping frequency was increased by decreasing the jaw opening degree and the durations of TCP, OP and CP. The jaw velocity immediately before tooth contact, which may be of significance for the reflex response, was however not increased. The average jaw speed was nevertheless increased from 10 to 15 cm/s since the turning from OP to CP was more abrupt in high than in low frequency tapping.The duration of electrical activity after tooth contact was significantly shorter at tapping with high than with low frequency. The teeth maintained contact without detectable rebound between each open‐close cycle. The OP started about 100 ms after the cessation of electrical activity both at low and high tapping freqency. The time between end of electrical activity and the start of a new OP was supposed to be dependent upon the relaxation time of the masseter muscles.
An objective method for measuring the surface morphology of cavities and restorations in vivo
Authors: ELDERTON R. J. 
Published: June 2007

SummaryA method was developed for quantifying morphological characteristics of cavities and restored teeth, in a quest for more knowledge of factors which determine the long term clinical success or failure of restorations, and which may therefore be used in making objective assessments of their quality. The method involved obtaining sequential silicone rubber replicas of teeth in vivo, sectioning them in planned planes, and then making objective linear and angular measurements directly from × 10 photographs of the resulting profiles and from positive models. It would seem that the method could be applied in a variety of clinical investigations.
In vitro polarization of dental amalgam in human saliva
Authors: FINKELSTEIN G. F. , GREENER E. H. 
Published: June 2007

SummaryPotentiostatic anodic polarization techniques in Ringer's solution are commonly used for the evaluation of the corrosion resistance of dental amalgam. This in vitro method strives to simulate the in vivo electrochemical behaviour of amalgam in an electrolyte of natural saliva.Several types of dental amalgam were anodically polarized in natural saliva solutions and supernatant saliva solutions. The anodic polarization profiles are presented, as well as scanning electron micrographs and X‐ray analysis of the corroded amalgam surfaces. These reveal corrosion products consistent with results found with previous artificial salivas as well as deposits possibly related to the organic component of natural saliva.
The surface structure of the human mandibular condyle in health and disease
Authors: JAGGER R. G. , WHITTAKER D. K. 
Published: June 2007

SummarySurface features of the human mandibular condyle have been studied by scanning and electron microscopy. Normal condyles possessed features similar to those in other diarthrodial joints but with certain differences. Two types of erosion and an exostosis were seen in diseased joints and the surface structure is described.