Biomedical subjects

J O Burgess

Publications and source records attributed to J O Burgess.

At least 19 recordsLinked to original sources

PubMed2001

The performance of bonded vs. pin-retained complex amalgam restorations: a five-year clinical evaluation.

BACKGROUND: The authors compared the clinical performance of complex amalgam restorations, replacing at least one cusp--retained either mechanically with self-threading pins or bonded--with a filled, 4-methacryloxyethyl trimellitate anhydride, or 4-META-based resin designed for amalgam bonding. METHODS: The authors placed 60 amalgam restorations (28 pin-retained and 32 bonded), each restoration replacing at least one cusp. They used self-threading stainless steel pins in the pin-retained group and a filled, 4-META-based bonding resin in the bonded group. For both groups, the authors left in place any retention form remaining after removal of an old restoration but did not enhance it. RESULTS: At four years, six restorations had failed. At five years, of the 40 restorations available for evaluation, three had failed, for a total of nine failed restorations; seven of those were pin-retained and two were bonded. Using the Fisher exact test to compare the groups at five years, the authors found no significant difference in failure rate, marginal adaptation, marginal discoloration, secondary caries, tooth sensitivity or tooth vitality. CONCLUSIONS: At five years, there was no difference in the performance of pin-retained amalgam restorations and bonded amalgam restorations. This study will be continued for at least a sixth year. CLINICAL IMPLICATIONS: Bonding with a filled, 4-META-based bonding resin appears to be a satisfactory method of retaining large amalgam restorations replacing cusps.

Acrylic Resins↗

PubMed2000

Microleakage and adaptation of Class II packable resin-based composites using incremental or bulk filling techniques.

PURPOSE: To compare the ability of three packable resin-based composite (RBC) systems (ALERT, SureFil, and Solitaire), placed and light-cured in either incremental layers or in bulk, to seal the gingival margin of Class II preparations when the gingival margin is placed apical to the cementoenamel junction. MATERIALS AND METHODS: Packable RBCs were used to restore 60 extracted human premolars with Class II preparations using an incremental-cure technique (each layer no greater than 2 mm in thickness when light-cured) or a bulk-cure technique (n=10). Manufacturers' directions were followed; the cure technique was the only variable. After the restorations were completed, the specimens were thermocycled, stained, sectioned, and viewed under a light microscope for microleakage at the gingival margin. RESULTS: All specimens showed leakage at the gingival margin. No statistically significant difference was found between the bulk-cure and incremental-cure techniques for each of the RBC systems evaluated. ALERT had significantly less leakage than SureFil and Solitaire.

Acid Etching, Dental↗

PubMed2000

Shear bond strength to moist and dry dentin of four dentin bonding systems.

PURPOSE: To compare the shear bond strength of four single-bottle adhesive systems (Prime & Bond NT, Single Bond, Gluma Comfort Bond, Gluma Comfort Bond + Desensitizer) bonded to moist and dry dentin. MATERIALS AND METHODS: A column of resin-based composite was bonded to human dentin using the dentin bonding systems following manufacturers' directions (n= 12). For half the specimens, the dentin was dried completely after acid etching (air dried for 10 s). For the remaining specimens, the dentin was left moist (glistening appearance with no puddles) after acid etching. All specimens were thermocycled for 1,000 cycles at 6-60 degrees C, placed in a fixture on an MTS machine and loaded in shear until failure. RESULTS: Statistical analysis revealed that dentin condition (moist or dry) was significant for Prime & Bond NT, Single Bond, and Gluma Comfort Bond. Bonding to moist dentin produced higher bond strengths than bonding to dry dentin. For Gluma Comfort Bond + Desensitizer, no statistical difference was found between bonding to moist vs. dry dentin. Over all, Single Bond and Gluma Comfort Bond bonded to moist dentin produced significantly higher bond strengths than all other groups.

Acid Etching, Dental↗

PubMed1997

Accelerated aging affects color stability of provisional restorative materials.

PURPOSE: The color stability of two shades each of five acrylic resin and seven resin composite provisional restorative materials was evaluated by reflection spectrophotometry following in vitro accelerated aging. MATERIALS AND METHODS: Specimens of provisional restorative materials were polymerized according to manufacturers' instructions and aged in an artificial aging chamber with exposure to a total ultraviolet irradiation of 60 kJ/m2. Color was measured by CIE L*a*b* on a reflection spectrophotometer before and after aging. Color change (delta E*) was calculated and analyzed statistically. RESULTS: Statistically significant changes in color were observed after accelerated aging. Nine of the 12 provisional materials tested showed perceptible color change of at least one of the shades tested. The most color-stable materials were the acrylic, Alike, and the resin composites, Luxatemp and Protemp Garant, which had no perceptible color changes under these conditions. CONCLUSIONS: Some acrylic resin and composite provisional materials change color significantly and perceptibly when exposed to in vitro accelerated aging conditions.

Acrylic Resins↗

PubMed1996

Torsional testing of the Lightspeed nickel-titanium instrument system.

Revolutions to separation and maximum torque at failure of 216 Lightspeed instruments were determined in an instron using a clockwise rotation. After instruments failed, the distance the instrument separated from the tip was measured. Comparison of the results with existing ANSI/ADA specification no. 28 showed that the Lightspeed far exceeded the values of the specification for revolution to failure. On the other hand, torque to failure results showed that instrument sizes 20 and 25 exceeded the specification, whereas instrument sizes 30 through 50 were below the minimum values. Half-size instruments were not compared, because specifications for half-sizes do not exist. Comparison between mean torque values and instrument shaft diameters of the Lightspeed previously reported showed a near linear relationship up to and including instrument size 50, but overall torque to failure increased exponentially when related to shaft diameter (coefficient of determination = 0.9923). Lightspeed instruments separated 2.32 +/- 0.60 mm from the tip, generally within the land area or at the beginning of the shaft. Scanning electron microscopic observation of the Lightspeed instrument fracture site showed two distinct areas. There was a striated concentric area in the periphery of the fracture characteristic of a brittle or cleavage fracture and a corrugated area in the center of the fracture characteristic of a ductile fracture.

American Dental Association↗

PubMed1996

Directly placed esthetic restorative materials--the continuum.

Because new restorative materials have had little clinical testing, it is difficult to make specific material recommendations for the esthetic restoration of carious teeth. Although fluoride-releasing materials have long been used successfully to restore carious teeth, little clinical documentation has been presented to support their use to inhibit recurrent caries, and their use as an effective restorative material may be questioned. Glass ionomers, compomers, and resin-modified glass ionomers are esthetic fluoride-releasing materials designed to restore teeth by bonding to tooth structure. This article describes the continuum of directly placed esthetic dental restorative materials, the efficacy of amalgam replacement restorative materials, and the role that fluoride-releasing materials may play in the inhibition of recurrent caries in vitro and in vivo.

Composite Resins↗

PubMed1995

Comparing the resistance of dentin bonding agents and pins in amalgam restorations.

This in vitro study involving 84 caries-free molar specimens examined the resistance of complex amalgam restorations retained by two dentin bonding agents--Amalgambond and Amalgambond Plus--four regular TMS pins, six regular TMS pins and four pins in conjunction with Amalgambond. Analysis indicated that the Amalgambond restorations were significantly weaker than the other types. Amalgambond Plus restorations were significantly stronger than the Amalgambond restorations but not different from the remaining groups. The authors concluded that complex amalgam restorations should be retained with a combination of adhesive and mechanical retention.

Analysis of Variance↗

PubMed1995

Tooth loss during compulsory dental care.

The traditional model that teeth are lost due to caries early in life and periodontitis later has been challenged by recent studies. Randomly selected Air Force records were reviewed for the reasons for extractions. Between the ages of 20 to 50, the rate of loss due to caries declined from 0.11 to 0.03, whereas the rate due to periodontitis increased from 0 to 0.34. This study supported the traditional model that tooth loss due to caries decreases with age and that periodontitis is the major cause of loss later in life.

Adolescent↗

PubMed1995

Dental materials for the restoration of root surface caries.

Specific material recommendations for the restoration of root surface caries are difficult because of a lack of data on the clinical performance of restorative materials in these situations. Although silver amalgam has been successfully used to restore carious roots, resin composite, glass ionomer, and resin-modified glass ionomers are also used to restore root surfaces since they are esthetic and bond to tooth structure. Fluoride releasing materials may inhibit recurrent caries in restored surfaces; however, clinical documentation of this phenomenon is sparse. This paper describes the efficacy of restorative materials used to restore root surfaces, the dynamic movement of fluoride into and out of restorative materials, and the role that fluoride releasing materials may play in the inhibition of recurrent caries in vitro and in vivo. In addition, classifications are given for low, medium, and high caries risk patients and material recommendations are made for each category of patient.

Composite Resins↗

PubMed1994

The strength of Class II composite resin restorations as affected by preparation design.

This study evaluated the load, applied to the marginal ridge, required to produce failure in Class II posterior composite resin restorations with four different preparation designs. In group 1, the preparation had an extension through the occlusal groove. The other three groups employed a proximal box-only (slot) preparation. Group 2 preparations had facial and lingual retention grooves that extended from the gingival floor to the occlusal surface; group 3 preparations were slots without grooves; and group 4 preparations were slots without grooves and with unsupported proximal enamel. After the restorations were thermocycled, their marginal ridges were flattened and loaded to failure. Mean (SD) failure loads were 438 (73) N in group 1; 383 (52) N in group 2; 297 (72) N in group 3; and 281 (63) N in group 4. Mean failure loads of groups 1 and 2 were not significantly different from each other but were significantly greater than failure loads for groups 3 and 4. Mean failure loads of groups 3 and 4 were not significantly different.

Analysis of Variance↗

PubMed1993

The accuracy of six impression techniques for osseointegrated implants.

PURPOSE: Six impression techniques were evaluated using tapered and square impression copings. MATERIALS AND METHODS: The absolute distortion was measured using a cast metal impression tray with fiduciary reference points external to the impression material. Measurements of the x, y, z coordinates on the master cast and the impressions were directly made with a travelling digitizing microscope. The difference between the coordinates of each of six sites in the impression and the corresponding reference site were compared. RESULTS: There was no significant difference between the techniques for the square copings but that there was a significant loss of accuracy in the z-axis with the tapered copings. CONCLUSIONS: No significant differences were noted.

Analysis of Variance↗

PubMed1993

A comparative study of three glass ionomer base materials.

This study compared the compressive and diametral tensile strength, compressive modulus, shear bond strength to dentin and resin composite, marginal gap between the base and tooth in Class V cavity preparation, and fluoride release of three glass ionomer base materials. In general, visible light-cured (VLC) base materials outperform the autopolymerizing glass ionomer base Ketac-Bond. The compressive modulus is significantly less for the VLC glass ionomer materials Vitrebond and Fuji LC compared to Ketac-Bond. The Fuji LC had greater diametral tensile strength, compressive strength, bond to dentin and bond to resin composite than Vitrebond or Ketac-Bond. The fluoride release of Vitrebond was greater than Ketac-Bond or Fuji LC. The marginal gap at the tooth/base interface was significantly less with the Fuji LC compared to the other two materials.

Analysis of Variance↗

PubMed1992

The advantages of coated titanium implants prepared by radiofrequency sputtering from hydroxyapatite.

The method used to apply hydroxyapatite to implant surfaces may affect the thickness and ultimately the physical properties of the coating. This study investigated and compared the healing rates of bone around commercially pure titanium implants and titanium implants sputter-coated from a hydroxyapatite target. Forty-five sputter-coated implants and an equal number of noncoated titanium implants were placed into 15 partially edentulated dog mandibles. The implants were removed at three time periods and were evaluated mechanically and histologically. A multiple analysis of variance indicated that the interface bond strength was statistically greater (p less than 0.01) for the sputter-coated implants. Histologic analysis of the bone-implant interface demonstrated that coated implants had nearly twice the percentage of direct bone contact compared with noncoated implants. The results indicate that implants sputter-coated from a hydroxyapatite target will accelerate the healing of bone at the implant interface.

Animals↗

PubMed1992

The resistance to tensile, compression, and torsional forces provided by four post systems.

This study measured the force required to displace four different endodontic posts (an experimental, Para-Post, Flexi-Post, and V Lock) when tensile, torsion, or compressive forces were applied. Extracted mandibular premolars were decoronated at the cementoenamel junction, the roots were divided into groups of similar size, and the pulpal tissue was removed. The canals were enlarged, cleaned, and filled with gutta percha. Post preparations were made, and the posts were cut and cemented into the post spaces with resin cement. The roots were notched with a separating disc and lowered into a metal tube filled with acrylic resin. Two Minim pins were placed into the coronal dentin paralleling the post. Composite resin cores were made around the coronal 4 mm of the posts and the two pins for 10 specimens from each group. The specimens were placed into a standardized fixture and a load applied until failure. The tensile load required to pull the experimental post and resin was significantly less than the load required to remove the threaded posts. Flexi-Posts provided the greatest resistance to torsion and tensile loading. The compressive load required to fracture the core over the V-Lock post was significantly greater than the other post systems.

Dental Cements↗

PubMed1992

Evaluation of resins for provisional restorations.

An in vivo study of two resin materials (Barricaid and Caulk Temporary Crown and Bridge Resin) was done to determine the retention, post-operative sensitivity, and fabrication time of provisional restorations made from these materials. Following the placement of these resins in 67 intracoronal cavity preparations of 19 adult patients, a baseline evaluation was made which included a clinical examination and color slides. Twenty-four hours after the temporary restorations were placed, the patients completed evaluations of the post-operative sensitivity experienced. There was no difference in post-operative sensitivity between the teeth restored with Barricaid or Caulk Temporary Crown and Bridge Resin. At the insertion appointment of the final restoration, the interim restoration's success rate was determined. There was no difference between the retention of the two provisional materials. Fabrication time was significantly different with Barricaid restorations requiring less than one-half the fabrication time of the Caulk Temporary Crown and Bridge Resin material.

Chi-Square Distribution↗

PubMed1992

Mechanical properties of dental base materials.

The compressive strengths and compressive moduli of seven base materials (Dycal, VLC Dycal, Time-line, Vitrabond, Ketac Bond, Fuji Lining LC, XR-Ionomer) were measured at 7 minutes, 24 hours, and 90 days using 9 mm by 4 mm cylindrical specimens prepared in hollow Teflon tubes. The 24-hour and 90-day specimens were maintained for 1 hour at 37 degrees C with relative humidity greater than 30%, then placed in distilled water at 37 degrees C until testing. After grinding the ends of the specimens flat, the cylinders of base material were loaded at 1.0 mm/min in an Instron. The compressive strengths of Timeline, a resin based material, at 7 minutes, 24 hours, and 90 days were not significantly different. Timeline had significantly greater compressive strengths of all time periods than the other six materials. The compressive strength of both Dycal and VLC Dycal decreased significantly between the 24-hour and 90-day periods. Of the three photosensitive GI base/liners tested, Fuji Lining LC had significantly higher compressive strengths in all three time periods. At 7 minutes, Timeline demonstrated a significantly higher compressive modulus than any other product. Ketac Bond had a significantly higher compressive modulus at 24 hours and 90 days.

Analysis of Variance↗

PubMed1991

Modification of the resistance form of amalgam coronal-radicular restorations.

Three groups of 10 extracted endodontically treated mandibular molars were mounted in acrylic resin. The occlusal surface was reduced until a 4 mm pulp chamber height remained. A peripheral shelf 2 mm deep and 1.4 mm wide was placed on one group, while four TMS Minim pins were placed 45 degrees to the long axis of the tooth into the facial and lingual walls of the second group. The final group served as the control and had no further treatment. All teeth were then restored with amalgam. An Instron testing machine was used to apply a controlled force to the beveled amalgam at a crosshead speed of 2 mm/min until fracture occurred. A peripheral shelf did not improve the fracture resistance of the coronal-radicular restorations tested. The specimens with semihorizontal pins were significantly stronger than specimens from the other groups. Placement of pins into the pulp chamber is recommended when adequate dentin remains.

Analysis of Variance↗

PubMed1991

Cutting effectiveness of diamond instruments subjected to cyclic sterilization methods.

The effect of repeated sterilization on the cutting effectiveness of one brand of rotary dental diamond cutting instruments was measured. Four groups of five diamond burs were sterilized by four methods: (1) sterilization with a chemical agent (Sporicidin); (2) steam under pressure (autoclave); (3) dry heat (Dri-Clave); or (4) chemical vapor (Chemiclave). Each group of diamond instruments made a timed cut in a ceramic block. This cut and all subsequent cuts were measured and were used to determine a baseline cutting effectiveness. Each group of diamond burs was then ultrasonically cleaned, sterilized, and another cut was made. At the end of 10 cycles there was no difference in cutting efficiency of the dental diamond instruments. However, there are differences in the cutting efficiency of individual diamond instruments. The SEM evaluation made prior to cutting and at the end of the 10 cycles of sterilization demonstrated that diamond wear was similar in all groups and that little diamond particle loss occurred in any group.

Analysis of Variance↗