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Biomedical subjects

J B Summitt

Publications and source records attributed to J B Summitt.

51 records · Page 3Linked to original sources
PubMedDate not supplied

Effect of grooves on resistance form of conservative Class 2 amalgams.

This study evaluated several means of providing retention for the approximal box in very conservative class 2 preparations (occlusal isthmus width 0.7 mm). Sixty class 2 mesio-occlusal cavities were prepared in sound human maxillary premolar teeth. Four types of retention grooves, 0.3-0.5 mm deep, were prepared at the axiofacial and axiolingual line angles and/or occlusal to those line angles. Specimens were loaded at an angle of 13.5 degrees from vertical in an Instron Universal Testing Machine until the restoration failed. Results indicate that grooves located occlusal to the axiopulpal line angle provided more resistance than conventional grooves (gingival to the axiopulpal line angle) or no grooves. The use of a short retention groove or retention point located occlusal to the axiopulpal line angle, but not extending to the occlusal cavosurface margin, provided greater retention while removing minimal tooth structure.

Analysis of Variance↗
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Support of occlusal enamel provided by bonded restorations.

In this in vitro study, the resistance to fracture of occlusal enamel supported by a bonded tooth-colored restorative material was compared to unsupported enamel and enamel supported by sound dentin. Eighty extracted human lower molars were sorted into five groups of 16 teeth each. Lingual cusps were removed. In Groups 2-5, dentin was removed from the facial cusps, leaving a shell of enamel. In Group 1, dentin was not removed. Group 2 remained unrestored. The groups in which a restorative material was inserted to replace missing dentin were as follows: composite (Scotchbond MP/Filtek Z250 [A2] in capsules, 3M); Group 4-resin-modified glass-ionomer (Fuji II LC [A2] in capsules, GC); Group 5-conventional glass ionomer (Fuji IX [A2] in capsules, GC). Specimens were thermocycled (1500 cycles, 6 degrees-60 degrees C, dwell 30 seconds), then mounted in die stone with lingual inclines of facial cusps approximately horizontal. The cusp ridges of the lingual inclines were flattened slightly using a horizontally mounted separating disk. Specimens were loaded evenly on flattened inclines in an Instron with a flat rectangular rod at a crosshead speed of 5 mm/minute. Data analysis was with one-way ANOVA and Student-Newman-Keul's test (F = 50.30, p < 0.0001). The bonded restorations provided significantly less enamel support than natural dentin and significantly more than when the enamel was left without support by dentin or a restorative material. There was no difference in support provided by the three restorative materials.

Analysis of Variance↗
PubMedDate not supplied

Root caries.

Explore the source record for details and available documents.

Dental Caries Susceptibility↗
PubMedDate not supplied

Retention and resistance provided by nine self-threading pins.

Extracted molar teeth, reduced to a flat surface approximately 3 mm coronal to the cementoenamel junction, were notched and embedded in acrylic. Nine types of pins were tested for retention in dentin and for resistance provided to complex amalgam restorations. Pins of each type were inserted into dentin and removed in tension with a constant load applied by an Instron Testing Machine (six pins per tooth). Minim and PPS pins provided significantly better retention in dentin than the other pins. Pins of each type were inserted into flattened teeth. Amalgam was condensed around the pins, allowed to set, and loaded in compression at 45 degrees. Pure titanium pins and heat-softened stainless steel pins provided significantly less resistance than titanium alloy or stainless steel pins.

Analysis of Variance↗
PubMedDate not supplied

Penetration of gel and solution etchants in occlusal fissures.

The major clinical advantage of a phosphoric acid gel etchant is its superior control during placement. However, its viscosity can impede penetration into occlusal fissures, resulting in adequate etching and decreased pit-and-fissure sealant retention. This study examined the penetration of gel and liquid phosphoric acid etchants in occlusal fissures. The depth of fissure penetration of the acids was investigated using paired, sectioned samples and evaluated with a scanning electron microscope. The etch pattern was measured from the base of the fissure to the first demonstrable evidence of etched enamel. A variable pattern of etched enamel was present at the base of the fissure to no pattern observable at distances of 15 microns from the base. A frequent finding was that debris partially or totally blocked the fissure orifice, preventing acid penetration. Utilizing a paired t-test, no statistically significant difference (0.5 less than p less than 0.8) in the fissure penetration of gel or liquid phosphoric acid etchants could be shown.

Acid Etching, Dental↗
PubMedDate not supplied

Effect of distribution of resistance features in complex amalgam restorations.

This study measured fracture resistance of complex amalgam restorations when pins or amalgapins were either distributed around the preparation or concentrated in one area of the preparation. The occlusal surfaces of 80 extracted molars were ground flat to 2 mm occlusal to the cementoenamel junction (CEJ). Roots were notched and embedded. Teeth were sized and distributed equally into eight groups (n = 10). Resistance features, four TMS stainless steel Regular pins or four amalgapin channels, were inserted into each molar. Resistance features were either distributed at the four line angles of each molar or clustered at two line angles. Matrices were applied, and amalgam was mechanically condensed into the matrices. Restorations were adjusted to a 4 mm vertical height and flat occlusal surfaces. A load was applied to each restoration at either a 45 degrees or a 90 degrees angle to the long axis of the tooth. Distributed pins provided significantly more resistance than clustered pins in groups tested at 90 degrees. Resistance to fracture in all groups loaded at 45 degrees and in amalgapin groups was not significantly affected by distribution of resistance features. Pins provided significantly more resistance than amalgapins at both angles of testing.

Analysis of Variance↗
PubMedDate not supplied

Effect of grooves on resistance/retention form of Class 2 approximal slot amalgam restorations.

This study evaluated in vitro the effectiveness of resistance/retention grooves in box-only (approximal slot) class 2 preparations. Forty-eight sound, caries-free maxillary premolars were distributed equally into four groups of 12 teeth based on faciolingual dimensions. Teeth were mounted vertically, and class 2 mesio-occlusal slot preparations were cut in each tooth. Resistance/retention grooves were placed in three of the four groups with a #1/4 round bur to a depth of 0.3-0.5 mm. Teeth were restored with amalgam and positioned 13.5 degrees from vertical; an area was flattened on each amalgam marginal ridge, and the flattened areas were loaded to failure using an Instron with a rectangular flat-ended rod at a cross-head speed of 1 mm/min. Mean load (SD) to failure of the group using "conventional" grooves extending in dentin from the gingival floor occlusally to near the occlusal DEJ was 196N (46N). For long grooves extending from the gingival floor to the occlusal surface, the mean failure load was 169N (58N). Slot restorations with short resistance/retention grooves or points (0.5-1.0 mm) just gingival to the occlusal DEJ had a mean failure load of 132N (44N). Slot restorations with no grooves had a mean failure load of 69N (46N). ANOVA and Student-Newman-Keuls tests were used for analysis. The no-groove group provided significantly less (P < 0.01) resistance than any group with grooves. Approximal slot restorations with "conventional" grooves were significantly more resistant (P < 0.01) than those with short grooves but were not significantly more resistant than those with long grooves.

Analysis of Variance↗
PubMedDate not supplied

Effect of rinse time on microleakage between composite and etched enamel.

This study compared microleakage of composite bonded to etched flattened enamel in seven groups of five extracted maxillary molars. The facial enamel of the molars was ground flat and etched for 20 seconds with 37% phosphoric acid gel. In one group, etching gel was not rinsed but dried only. In four groups, gel was rinsed with an air/water spray for varying amounts of time. In the other two groups, gel was rinsed with water only for two different amounts of time. Etched surfaces were dried, and a liquid resin was applied and polymerized; a button of composite resin was polymerized to the flattened surface. Specimens were thermocycled, stained, then sectioned longitudinally. Microleakage was measured at the occlusal and gingival enamel margins and expressed as a percentage of the total length of interface. A mean (SD) percentage microleakage was determined at the occlusal and at the gingival margins for each group as follows: no rinse--89.60 (14.34); one second--water 0 (0), air/water 0 (0); three seconds--water 0.98 (1.34), air/water 0 (0); five seconds--air/water 0 (0); 20 seconds--air/water 0 (0). Because of abnormal distribution, data were analyzed using Wilcoxon two-sample tests. The no-rinse group had significantly more microleakage than any of the other groups (P = 0.0067), which were not significantly different from each other (P = 0.18). A one-second rinse with either water or air/water spray was as effective as a 20-second rinse with air/water spray in preventing microleakage at the resin-enamel interface.

Acid Etching, Dental↗
PubMedDate not supplied

Effect of grooves on resistance form of Class 2 amalgams with wide occlusal preparations.

This study evaluated in vitro the necessity of retention grooves in approximal boxes in class 2 preparations with faciolingually wide occlusal extensions (occlusal isthmus width 1.8 mm). Thirty-six class 2 mesio-occlusal cavities were prepared in sound human maxillary premolar teeth and divided into three groups of 12. In one group, the preparations had no retention grooves. In another group, retention grooves 0.3-0.5 mm deep were prepared at the axioproximal line angles and extended from the gingival floor occlusally to just gingival to the occlusal dentinoenamel junction. In the third group, a 1 mm-long groove was prepared extending from the axiopulpal line angle occlusally to just gingival to the occlusal dentinoenamel junction. The marginal ridges of the amalgam were loaded at an angle of 13.5 degrees from vertical in an Instron Testing Machine until the restorations failed. Results indicated no significant difference in load to cause failure in any of the three groups. Restorations without approximal retention grooves possessed as much resistance to failure as those with grooves.

Analysis of Variance↗
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Retention of Class 3 composite restorations: retention grooves versus enamel bonding.

This study compared the tensile loads required to dislodge class 3 composite restorations with and without retention grooves. Thirty extracted human maxillary central incisors were divided into two groups of 15 teeth each. A C-shaped class 3 preparation with lingual access was cut into one approximal surface of each incisor to standardized dimensions using a #329 bur. A 0.5-1.0 mm 45 degrees bevel was prepared on the lingual and gingival enamel margins. In one group, an incisal retention point and a gingival retention groove were prepared with a #1/4 round bur to a depth of 0.25-0.5 mm; the other group had no retention grooves/points. A nonretentive 2 mm round "well" with diverging walls was cut 0.5-1.0 mm into the axial dentin to accommodate the head of a pin that was inserted prior to composite restoration. Each pin shaft extended approximally from its incisor. A bonding agent (Universal Bond 3 Primer and Adhesive, L D Caulk) was applied to each preparation, and composite resin (Prisma APH, L D Caulk) was inserted incrementally. Each increment was exposed to 40 seconds of polymerization light. Restoration surfaces were finished and polished with Sof-Lex disks (3M Dental Products). Specimens were thermocycled 6 to 60 degrees C, for 500 cycles, with a 30-second dwell time. They were then positioned in an aligning device, and pins were loaded in tension in an Instron Testing Machine at a head speed of 2 mm/minute to restoration failure. Mean (SD) failure loads in Newtons were: no grooves 83.6 (19.8); grooves 69.6 (18.1).(ABSTRACT TRUNCATED AT 250 WORDS)

Composite Resins↗
PubMedDate not supplied

Mechanical properties and clinical performance of a gallium restorative material.

In a combination clinical/laboratory evaluation, a gallium restorative alloy (Galloy) was assessed for six mechanical properties: compressive strength, diametral tensile strength, creep, hardness, wear, and dimensional change. Laboratory tests indicated that the gallium alloy was similar to either Tytin or Dispersalloy in most respects, with the exception of lower wear and higher 7-day diametral tensile strength. In the clinical trial, all Galloy restorations were lined with a resin to prevent moisture contacting the material during the first hours after placement. All gallium restorations--class 1's only--were intact, and no teeth were fractured at the end of 1 year. There was little difference found at the 1-year evaluation compared to the 6-month results. The surface of the gallium alloy was generally rough, and many restorations exhibited some tarnish on the surface. It should be pointed out that this product has not been FDA approved at the present time and is not on the market.

Dental Alloys↗
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Fracture resistance of complex amalgam restorations.

This study evaluated fracture resistance provided to complex amalgam restorations by adhesive and mechanical resistance features. The occlusal surfaces of 30 extracted molar teeth of similar size were ground flat to approximately 2 mm coronal to the CEJ. The teeth were divided into three groups. Roots were notched and embedded in acrylic resin. In two groups, four TMS Minim stainless steel pins were placed into dentin at the line angles. A copper band matrix was applied to each specimen and reinforced with compound. After applying either Copalite or Amalgambond Plus, Tytin amalgam was condensed into the matrix. The bands and excess amalgam were removed 10 minutes later, and each amalgam occlusal surface was ground flat to give the amalgam restoration a 4 mm occlusal height. Specimens were thermocycled for 2500 cycles at 6-60 degrees C with a 30-second dwell time. They were then stored in deionized water for 1 month at room temperature. A 1 mm 45 degrees bevel was placed on the facio-occlusal angle of the amalgam. Each specimen was loaded to failure in compression at 45 degrees in an Instron Testing Machine at a crosshead speed of 5 mm/min. The groups were: Group 1, four Minim pins and Copalite; Group 2, four Minim pins and Amalgambond Plus; and Group 3, Amalgambond Plus only. The data were analyzed using a one-factor ANOVA and a Tukey B post hoc test. There was no significant difference between Groups 1 and 3. The Amalgambond Plus combined with pins provided significantly greater resistance to fracture than pins or Amalgambond Plus alone (P < 0.05).

Analysis of Variance↗