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At least 1,765 records · Page 98Linked to original sources
PubMed1994

Fracture resistance in conservative Class II cavity preparation: box vs tunnel.

A total of 40 extracted human maxillary premolar teeth were used in this study. Teeth were randomly distributed between two main groups. In group A conservative class II Box preparations were cut in each tooth. In group B the proximal cavity was prepared through the occlusal surface and the proximal marginal ridge was left intact (tunnel preparation). Group A and group B were randomly subdivided into two subgroups (a & b). In groups Aa and Bb a posterior composite resin material was used to restore the prepared cavities (no base was used). While in groups Aa & Bb the posterior composite resin was used with a glass ionomer cement base. The teeth were tested on an Instron testing machine for their resistance to fracture, force being applied equally to buccal and lingual cusps. Mean fractures values were: Gp. Aa 285 LB.: Gr. Bb 245 lb. Bb 240 lb. One way analysis of variance showed no statistical difference between the four groups. The tunnel preparation did not increase the resistance to fracture of the restored tooth compared to a box preparation.

Bicuspid↗
PubMedDate not supplied

A histological study of tooth allografts transplanted to untreated and immunologically prepared mice.

Ten-day-old mouse teeth were grafted subcutaneously into adults of an unrelated strain which were either untreated or had rejected a skin graft from the same strain as the tooth donors. First set allografts degenerated rapidly after grafting and were only sparsely repopulated subsequently. No cell-mediated immune response was observed. In contrast, second set allografts were heavily infiltrated with mononuclear leukocytes which persisted throughout the study, although the coronal pulp was never involved. It was suggested that first set allografts did not suffer a cell-mediated response because rapid degeneration of the cellular components removed the immunogenic target tissue before the host response could be effected.

Animals↗
PubMed2001

Predictable success with resin bonded fixed partial dentures.

The conservative nature of the resin bonded fixed partial denture is the reason it is used. The ability to replace a missing tooth while avoiding aggressive preparation of the abutment teeth is a desirable concept. The use of conservative preparation forms will aid in the long term predictable success of the resin bonded fixed partial denture.

Denture Design↗
PubMed2005

Selected characteristics of a new polyvinyl siloxane impression material--a randomized clinical trial.

OBJECTIVES: This study evaluated the ability of a new polyvinyl siloxane impression material (Affinis, Coltène/Whaledent, material A) to obtain final impressions free of bubbles and voids for indirect fixed cuspal-coverage restorations. The results were compared to a control polyvinyl siloxane impression material (material B). Both materials were handled by inexperienced clinicians (undergraduate dental students) in student clinics. METHOD AND MATERIALS: One-hundred and thirty patients who were treated in the Louisiana State University School of Dentistry Junior Student Clinic for indirect fixed cuspal-coverage restorations and who met the inclusion criteria were randomly assigned to either one of two treatment groups, group A (n = 65) or group B (n = 65). Two calibrated examiners evaluated the first impression of prepared posterior teeth at a magnification of 10x for acceptability (no voids or bubbles). Position of tooth, type of preparation, preparation finish line (Class I-V), and gingival bleeding scores were recorded. All statistical tests were performed with the level of significance set at .05. RESULTS: The Fisher-Freeman-Halton test did not reveal significant associations between material and gingival bleeding score (P = .492). Significant differences in the location of the preparation finish line between materials were observed (P = .0096); material A was more frequently used in cases where the preparation finish line was located at least 2 mm subgingivally. Logistic regression was used to assess the effect of the material on the success of the impression (acceptable/ unacceptable). Material was highly significant in the logistic model (P < .001) with an odds in favor of an acceptable impression being eight times higher with material A than with material B (odds ratio = 8.00; 95% confidence index for odds ratio: 2.832, 22.601). The 60/65 (92.3%) impressions made with material A and 39/65 (60%) impressions made with material B were rated "acceptable." CONCLUSION: The new polyvinyl siloxane impression material provided a significantly higher proportion of impressions free of bubbles and voids than the control polyvinyl siloxane material.

Chi-Square Distribution↗
PubMed1992

Effect of precurving on the performance of endosonic K files.

This study compared the performance of precurved and straight endosonic files. Size 15, 20, and 25 endosonic K files were precurved to different degrees (20 to 90 degrees) and the resultant oscillatory pattern showed no significant difference compared with corresponding straight files. Endovue blocks were prepared with either a #15, 20, or 25 endosonic file which was either straight or precurved. Those blocks prepared with precurved files had a continuous taper while blocks prepared with straight files had constrictions along their lengths. Finally, a curved root of a human natural tooth had windows prepared along its length so that the oscillatory pattern of the file could be observed. The precurved file oscillated more freely than a straight file as observed by the presence of antinodes along the file and the accumulation of dentin chips within the canal. The results of this study suggest that it is advantageous to precurve endosonic files before using them in curved canals.

Dental Cavity Preparation↗
PubMed2003

A prospective clinical trial comparing preformed metal crowns and cast restorations for defective first permanent molars.

AIM: This study investigated two methods for the restoration of permanent molars affected by amelogenesis imperfecta (AI) or severe enamel defects. METHODS: A prospective clinical trial was carried out on 17 subjects affected by AI or severe enamel defects of first permanent molars. A split mouth design was used so that each right or left permanent molar in both jaws was restored using either a preformed metal crown (SSC) or a cast adhesive coping (CAC). Subjects were followed for up to 24 months and assessed for longevity and quality of the restorations. Sequential analysis was used to compare longevity. RESULTS: Records for 42 restorations (19 SSC; 23 CAC) were kept. The split mouth design was possible on 24 occasions (right versus left=14; maxilla versus mandible=10). Three restorations, one SSC (at 6 months) and two CAC (at 2 and 19 months) failed and required replacement. There was no significant statistical difference between the two types of restorations. CONCLUSION: While there was no difference between the two restorations for quality and longevity, the SSC was considerably cheaper to use and needed only one visit, but more tooth tissue was lost in preparation and fitting. The CAC was significantly more expensive but left nearly all of the tooth crown intact. The choice of which restoration to use is indicated by the immediate and long-term needs of each individual patient.

Adolescent↗
PubMed1995

Effect of restorative materials on cuspal flexure.

The purposes of this study were (1) to establish a methodology for determining surface strains in two locations of the same tooth under intact, prepared, and restored conditions and (2) to compare the effects on stiffness of different restorative materials in a tooth subjected to cuspal loading. Two linear strain gauges were mounted on each of 30 extracted maxillary premolar teeth. Teeth were mounted in poly(methyl methacrylate) resin and randomly assigned to one of three study groups according to the restorative material and application technique to be used. Statistical analysis indicated a statistically significant interaction between restorative material and tooth condition at both proximal and buccal sites and a statistically significant difference in stiffness between teeth restored with Tenure/Marathon V and those restored with either amalgam or Scotchbond 2/P-50 at the proximal site. Results suggest that the methods employed provide a useful, nondestructive means of testing the same tooth under various conditions.

Analysis of Variance↗
PubMed1996

Variation in phosphoric acid concentration and treatment time and HEMA diffusion through dentin.

PURPOSE: The effects of phosphoric acid concentration and time of dentin treatment on the movement of 2-hydroxyethylmethacrylate (HEMA) from a bonding resin-resin composite combination through dentin were investigated in vitro. MATERIALS AND METHODS: Freshly extracted human third molar teeth were divided into seven groups each of 10 teeth. A closed chamber was attached to the CEJ of each tooth to contain 1 ml distilled water. An occlusal cavity of 6 mm diameter and remaining dentin thickness of 1.0-1.5 mm was prepared in each tooth. Dentin was treated with either 10% phosphoric acid for 15, 30 or 60 seconds or with 37% phosphoric acid for 15, 30 or 60 seconds. A control group not treated with acid was also prepared. The cavities were rinsed, dried and then treated with the HEMA-containing Scotchbond Multi-Purpose bonding resin which was light-cured for 10 seconds. The cavities were then restored with Z100 and light-cured for 30 seconds. Water samples were retrieved from the chambers over a time course (4.32, 14.4, 43.2, 144 & 432 minutes; 1, 3 and 10 days) and analyzed by high performance liquid chromatography. RESULTS: HEMA was detected in the pulp chambers of all teeth from 4.32 minutes after resin placement. Mean total (cumulative) release at 10 days for all groups was in the 2-4 mumol range. The highest HEMA diffusion rate was 4.32 minutes after placement and were in the range 6-13 times greater than control in the 10%-15 seconds, 10%-30 seconds, 10%-60 seconds, 37%-15 seconds, and 37%-30 seconds groups. Unexpectedly, by far the lowest early rate at 4.32 minutes was in the 37%-60 seconds group (0.6 times of no-acid control).

Acid Etching, Dental↗
PubMed2004

The milled surface as a precision attachment.

The creation of paralleled, milled surfaces in natural or restored abutment teeth, coupled with removable partial denture castings that have optimal contact with these preparations, results in a path of insertion and removal that is controlled in a manner similar to one using conventional precision attachments. Because the milled surfaces are primarily extracoronal, little if any, additional tooth reduction is required for adequate mouth preparation. Avoiding additional tooth reduction minimizes later abutment fracture. The great increase in stability and resistance to rotational movements, when combined with conventional posterior clasping, provides a reasonable alternative to the precision attachment in providing maximal esthetics for the partially edentulous patients.

Dental Abutments↗
PubMed1977

Influence of local insults on sympathetic vasoconstrictor control in feline dental pulp.

The present investigation was undertaken to ascertain whether local insults can affect the sympathetic vasoconstrictor regulation of pulpal blood flow. The rate of disapperance (k-value) of iodide from dentinal cavities was measured in anaesthetized cats. Changes in k-value reflected changes in blood flow. It has previously been shown that stimulation of sympathetic vasoconstrictor nerve fibres generally causes a clearcut decrease in the k-value. Deep cavity preparation was found to inhibit the vasoconstrictor response in a few cases in experiments on mature cats. Heating or cooling the tooth during cavity preparation induced a more frequent inhibition, which proved to be reversible within a few hours. Compound 48/80 applied locally to the cavity was also found to induce inhibition of the vasoconstrictor effect, but in this case no sign of reversibility was observed. Chronic insults were produced by exposing the cavity to oral microorganisms during 1-4 weeks before the experimental procedure. In this case, the sympathetic vasoconstrictor response was not inhibited. A histological study was performed to examine the pulp tissue after cavity preparation and the application of insults. It was found that cavity preparation and acute insults caused little or no disturbance, while chronic insults resulted in severe damage to the pulpal tissue.

Administration, Topical↗
PubMed2006

Influence of cavity type and size of composite restorations on cuspal flexure.

OBJECTIVES: The present study examines the influence of cavity type, and size of composite restorations on cuspal flexure due to polymerization shrinkage. METHODS: Thirty healthy premolars were selected and divided into two experimental groups. Group 1: Mesial, mesio-distal, and MOD cavities were successively prepared in each tooth by means of the SONICSYS approx system (KaVo) using a n 2 (small) diamond tip. Group 2: The same cavity preparation sequence was followed but a n 3 (medium) tip was used. Cavity preparations were performed and afterwards restored using the same adhesive system and resin composite. Cuspal displacement was measured 15 min after completion of each type of restoration. RESULTS: Under the experimental conditions used, polymerization shrinkage of composite restorations resulted in an inward deflection of the cusps in all the situations evaluated. The Friedman global test found significant differences according to the cavity type and size (p<0.05). The Wilcoxon test revealed that deflection was significantly affected by the amount of dental tissue lost, since practically no movement was observed in the case of mesial cavities but extensive displacements were recorded for MOD restorations (p<0.05). However, no influence of bucco-lingual width on cuspal flexure was detected by the Student s t test (p>0.05). CONCLUSIONS: The present study demonstrates that significantly higher cuspal deflection is observed in MOD restorations, showing that the degree of dental removal influences the cuspal flexure from polymerization shrinkage of composite restorations.

Composite Resins↗
PubMed1993

Dentin pretreatment and caries inhibition by a fluoride-releasing resin.

The purpose of this study was to examine the effect that phosphoric acid etchant, used to remove the smear layer, may have on dentin demineralization inhibition. Fifteen molars had Class V preparations placed on the mesial and distal surfaces, the gingival seat being placed 1 mm below the cementoenamel junction. Randomly, one preparation of each tooth had etchant placed carefully on only enamel for 30 seconds. Etchant was placed on the gingival seat dentin of the remaining preparations, as well as the enamel for 30 seconds. A HEMA dentin primer containing maleic acid was placed and allowed to dry on the unetched dentin, then a Bis-GMA resin with tetrabutyl ammonium tetrafluoroborate was placed. Only the fluoridated resin was placed over the dentin that had been etched. All teeth were then restored with resin composite and subjected to an artificial caries challenge (pH 4.4) for 7 days. Sections 100 microns were obtained, photographed under polarized light microscopy and demineralized areas were digitized. Results demonstrated the mean area (mm2 +/- S.D.) demineralization 0.5 mm from the gingival margin to be: etched dentin (0.77 +/- 0.36); non-etched dentin (1.52 +/- 0.98). A t-test indicated that there was significantly less demineralization when the fluoridated resin came in direct contact with dentin that had the smear layer removed (P < 0.05).

Acid Etching, Dental↗
PubMed1992

An ultrastructural and autoradiographic analysis of primary and replacement odontoblasts following cavity preparation and wound healing in the rat molar.

Numerous studies using various animal and human models have reported changes in the morphology and metabolic activity of primary odontoblasts in the mature tooth pulp after perturbations of the tooth including cavity preparation and restoration, pulpal exposures and pulp capping with various capping agents. The first part of this study investigated changes in primary and replacement odontoblast activity after cavity preparation or pulpal exposure. Two groups of rats were used in this investigation. One group of rats had Class V cavities prepared to the DEJ of the first maxillary molars. These rats were immediately injected with 3H-proline and killed 15, 30 or 60 minutes later. Rats killed at day 1, 3, 5, 7, 10 or 14 were injected one hour prior to sacrifice. The second group of rats each had a pulp exposure that was capped with a calcium hydroxide containing material and restored with a composite resin. Rats were sacrificed as previously described. Tissue was processed routinely for ultrastructural analysis and E.M. autoradiography. The second part of this study consisted of an injection of 125I-fibrinogen one hour prior to a class V cavity preparation 1/2 the distance through dentin thickness. Rats were sacrificed at 5, 10, 15 and 30 minutes postsurgery. Differences in the location and distribution of the reduced silver halide grains were recorded as well as differences in the amount and distribution of the various organelles measured between primary and replacement odontoblasts. The results of this study suggests that primary and replacement odontoblasts were morphologically and physiologically dissimilar at the time periods tested in this study. 125I-fibrinogen was demonstrated within the dentinal tubules and in the floor of the cavity preparation as early as 5 minutes after completion of the cavity preparation. The preliminary results of the 125I-fibrinogen suggest that operative trauma can effect very rapid changes to the dental pulp leading to leakage of plasma proteins from the circulation, between odontoblasts, out of the tubules to the cut dentin surface.

Animals↗
PubMed2005

A resin impression SEM technique for examining the glass-ionomer cement chemical fusion zone.

Examination of the auto-cure glass-ionomer cement (GIC)-tooth interface using conventional SEM techniques causes severe dehydration and subsequent fracturing of the GIC, hampering accurate assessment of the GIC-tooth interface. A simple, accurate impression technique was developed to examine the GIC chemical fusion zone. Samples of GIC were bonded to prepared cavities and tooth surfaces that had been conditioned with 10% polyacrylic acid for 10 s and allowed to mature for 24 h in neutral buffered saline, sectioned under water and then acid etched with 37% phosphoric acid for 30 s to remove sectioning smear layer and to highlight surface morphology, rinsed and gently dried. Optibond Solo Plus was then applied and photo-polymerized. Increments of posterior hybrid composite were then bonded onto the Optibond and photo-polymerized. The tooth sections with attached GIC were then dissolved off the bonded composite with 18% HCl for 4 days. Subsequent SEM examination of the resin impressions created with this technique provided high-quality, detailed images of the GIC chemical fusion zone, without the development of the fracture artefacts associated with the desiccation of GIC. The resin impression technique described proved to be a simple and successful method for providing accurate SEM images of the GIC-tooth chemical fusion.

Composite Resins↗
PubMedDate not supplied

The aesthetic composite bridge.

New developments are constantly introduced in the search for the optimal treatment modality to restore a single anterior tooth. The patient attention has shifted to aesthetics of the restoration, biocompatibility of the dental materials utilized, conservative preparation of the teeth to be restored, and the retention of intact adjacent dentition. The learning objective of this article is to review the methods currently utilized and to present a recently introduced treatment modality--the two-component bridge, which combines the strength and resiliency of composite resin with the aesthetic advantages of porcelain. The technology of the material is reviewed, the predominantly lingual tooth preparation procedures are outlined, and the bridge try-in is described. The advantages of the two-component bridge are presented along with the contraindications and suggestions of careful case selection. Three cases with congenitally missing maxillary lateral incisors in youthful patients are presented to supplement the theoretical outline and to describe and illustrate the clinical procedure.

Adolescent↗
PubMed2006

90Sr concentration in cow teeth from South Ural region, Russia, using Monte Carlo simulation.

The Imaging Plate (IP) technique which uses the Monte Carlo code, MCNP, to convert IP response to 90Sr concentration with varied thickness of the standard source has been proposed in this study. In order to verify the validity of simulation calculation in the proposed method, the radial distribution of IP signal has been compared between calculation and experiment. The result is, they are in good agreement. The proposed method has been applied to a cow tooth from the territory contaminated by radioactivity after the accident in the Mayak facility in the South Ural, Russia. Two samples have been prepared from the tooth, i.e., a thin sample of 1.2+/-0.2 mm in thickness and a thick sample which is a half of the tooth. The IP response has been evaluated for the thick sample using experimentally made standard sources, and multiplied by a modification factor to decide that for the thin sample. The modification factor has been determined with MCNP to be 0.83+/-0.08 for a thickness of 1.2+/-0.2 mm. Using these values, 90Sr concentration has been estimated to be 0.11 Bq/g for the thin sample and 0.12 Bq/g for the thick sample, hence they are in good agreement.

Animals↗