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Biomedical subjects

J W Robbins

Publications and source records attributed to J W Robbins.

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

Clinical crown length changes from age 12-19 years: a longitudinal study.

OBJECTIVE: The objective of this study was to investigate the relationship between age, gender and clinical crown length using a longitudinal study design. METHOD: Four hundred and fifty-six sets of study models initially obtained for a large prospective longitudinal cohort study of orthodontic needs were examined. Each set of models corresponded to subjects at three different ages: 11-12, 14-15 and 18-19years old. The clinical crown height of the maxillary right central incisor (11), maxillary right canine (13), maxillary left lateral incisor (22) and mandibular left central incisor (31) was measured from gingival crest to the incisal edge using digital calipers. RESULTS: Analysis revealed a significant (p<0.0001) age effect on crown length for all four teeth investigated. A significant gender effect was found in relation to the maxillary right canine, maxillary right central incisor and maxillary left lateral incisor. Pairwise comparisons of the means for each age group for the maxillary right canine, maxillary right central incisor and maxillary left lateral incisor revealed significant (p<0. 0001) increases in clinical crown length between each assessment period. CONCLUSION: The findings of the present study indicate that, the process of passive eruption, resulting in increased clinical crown length appears to continue throughout the teenage years. This finding is considered to be of importance to the clinician making treatment decisions for teenagers and young adults requiring treatment in the anterior segments of the mouth.

Adolescent↗
PubMed2000

Esthetic gingival recontouring--a plea for honesty.

There continues to be a tremendous amount of confusion in the dental literature and among practitioners regarding the diagnosis and treatment of gingival discontinuities. The purpose of this article is to present a rationale for gingival recontouring, illustrated by a case report. A patient requested gingival recontouring. Because the preoperative evaluation was inadequate, a simple gingivectomy procedure was performed. After healing, the tissue had rebounded to its preoperative levels. The patient was then evaluated more comprehensively, and gingival recontouring was accomplished with a mucoperiosteal flap and osseous recontouring. The tissue subsequently healed at the correct position and remained stable. To reliably perform gingival recontouring procedures, the dentist must have a clear understanding of the biologic width. By using diagnostic bone sounding, the practitioner can determine the appropriate surgical procedure that will ensure an esthetic and stable postoperative result.

Adult↗
PubMed1999

Differential diagnosis and treatment of excess gingival display.

Excess gingival display, commonly described as the "gummy smile," has received increased emphasis in the dental literature in recent years. There are several etiologies for this condition, including lip length and activity, clinical crown length, dentoalveolar extrusion, and vertical maxillary excess. For this reason, it is essential that a differential diagnosis be developed so that a specific therapy or group of treatments can be developed for a patient. It is the purpose of this article to describe a differential diagnosis for excess gingival display as well as recommendations for treatment.

Adult↗
PubMed1997

Altered passive eruption: an etiology of short clinical crowns.

The gingival complex plays a vital role in the overall beauty of a smile. To predictably achieve a successful esthetic and functional result, the dentist must be able to precisely predict the treatment outcome based on biologic determinants. In this article, the biologic requirements for gingival health are discussed. In addition, a differential diagnosis for excess gingival display and treatment options for this condition are discussed.

Adolescent↗
PubMed1994

The clinical performance of a new adhesive resin system in class V and IV restorations.

A clinical trial was initiated to examine a new adhesive system introduced for dentin and enamel bonding of composite resins. Restorations were placed in patients in need of Class V and Class IV restorations. The clinical study was designed to examine the adhesive system in restorations involving mostly dentin surfaces (Class V) and in a population of restorations mostly involving enamel surfaces (Class IV). At the 1-year recall period, the adhesive system had demonstrated excellent adhesive qualities in both types of cavities. Initial results also showed improvement over previous adhesive systems with regard to moisture sensitivity and variation in dentin composition.

Acid Etching, Dental↗
PubMed1993

Fracture resistance of endodontically-treated cuspids.

The purpose of this in vitro study was to determine the optimum method for treating an endodontically treated cuspid prior to placement of a crown. Sixty extracted human maxillary and mandibular cuspid teeth were divided into groups of 10. In groups A and B, the crowns were removed at the CEJ and post amalgam cores were placed with #5 Paraposts (Group A) and #120 tapered Ticonium Endowels (Group B). The remaining groups received the following treatments: Group C--gutta percha endodontic fillings, Group D--bonded composite (Fluoro-Core) in the access preparations, Group E--#100 Ticonium Endowels, and Group F--untreated control group. All teeth were prepared for and received cemented gold crowns, were mounted in methyl methacrylate and were stressed at 45 degrees to failure in an Instron machine. Mean fracture strengths (Newtons) were: Group A--500, Group B--530, Group C--520, Group D--510, Group E--680, Group F--580. Results indicated that when the coronal tooth structure was removed, there was no statistical difference (P < 0.05) between the Parapost and Endowel core buildup groups. Although Group E (intact crowns+Endowel posts) displayed higher mean fracture resistance than all other groups, there was no statistical difference (P < 0.05) due to the large range.

Analysis of Variance↗
PubMed1992

Effect of the levels of dissolved oxygen on the expression of recombinant proteins in four recombinant Escherichia coli strains.

Four recombinant strains of Escherichia coli were examined for the effects of the dissolved oxygen level on the level of biomass, the plasmid content, and the level of recombinant protein at the stationary phase of batch growth. Strains JM101/pYEJ001, and TB-1/pYEJ001 (encoding chloramphenicol acetyltransferase), and strain TB-1/p1034, and TB-1/pUC19 (encoding beta-galactosidase) were grown at the constant dissolved oxygen levels of 0, 50, and 100% air saturation, as well as in the absence of dissolved oxygen control. The biomass of all strains under constant aerobic conditions was 12-36 times higher than that under anaerobic conditions, but was the same as or slightly higher than that without dissolved oxygen control. The plasmid content in all strains under aerobic conditions was 2.9-11.7 times higher than that under aerobic conditions. The optimal dissolved oxygen concentration for the specific activity of recombinant proteins was dependent upon the strain. In no strain were constant aerobic conditions optimal. However, because of the effect on biomass, controlled aerobic conditions were optimal for the volumetric activity of recombinant protein in all but one strain.

Aerobiosis↗
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↗
PubMed1991

Color characterization of porcelain veneers.

Porcelain veneers have become a popular treatment modality in recent years. A common problem associated with these restorations is the inability of the dentist to reproduce the polychromatic appearance of a natural tooth with a porcelain veneer. It is the purpose of this article to describe several methods that may be used to transform a monochromatic porcelain veneer into a polychromatic restoration that approaches the beauty of a natural tooth.

Color↗
PubMed1991

Clinical evaluation of a dentinal adhesive system: three-year results.

The dentinal adhesive Scotchbond 2 was evaluated with the microfilled composite resin Silux in cervical and root caries lesions for up to 3 years. Clinical criteria evaluated included retention, marginal integrity, marginal discoloration, color match, anatomic form, recurrent caries, gingival response, and postoperative sensitivity. Overall, the adhesive demonstrated improved performance over earlier dentinal adhesive systems. Retention was greatest at 3 years when available enamel margins had been etched (93%) and when root caries lesions (97%) had been restored. Other criteria were reported as generally favorable. Early findings suggest that the level of development of sclerotic dentin may influence behavior of the adhesive. The greatest difficulty was noted in lesions presenting with heavy sclerotic dentin.

Acid Etching, Dental↗
PubMed1990

Dimensional stability of glass ionomer used as a core material.

This laboratory study evaluated the dimensional stability of two reinforced glass ionomers (Ketac-Silver and Fuji Miracle Mix) in comparison with amalgam. Ten core build-ups were prepared with each material on extracted human teeth. Four Minim pins were placed in each tooth for retention. A gold casting was made for each core build-up. The specimens were placed in a distilled water and the distance between the casting and the tooth was measured at 1 hour, 6 hours, and then every 24 hours for 7 days. After 7 days, the measured changes were small, ranging from 1 to 63 microns. The reinforced glass ionomers were found to be dimensionally stable in moisture over a period of 7 days.

Analysis of Variance↗
PubMed1990

Guidelines for the restoration of endodontically treated teeth.

Much confusion exists in the dental community regarding the restoration of endodontically treated teeth; few review articles present succinct guidelines for the restoration of these teeth. This article reviews the literature and presents guidelines for restoration of endodontically treated teeth.

Crowns↗
PubMed1989

Tensile bond strength of dental adhesives to dentin and enamel.

This study compared the tensile bond strengths of an unfilled resin bonding agent and four proprietary dentin bonding agents to dentin and acid-etched enamel. Forty-eight hours after bonding, 10 dentin-bonded teeth and 10 enamel-bonded teeth for each material were loaded in tension in an Instron Universal Testing Machine until bond failure. The remaining specimens were stored in a water bath for six months and then tested in a similar manner. At the end of six months, Universal Bond and Tenure (3-step) had bond strengths significantly greater than those of the other agents. All bonding agents, except Tenure (3-step), showed a significant decrease in tensile bond strength to both dentin and enamel after six months (p less than 0.0001).

Composite Resins↗
PubMed1989

Retention and resistance features for complex amalgam restorations.

Although not absolute, there are indications for each of the retention and resistance features described. Amalgapins and circumferential slots have their greatest indication in teeth with short clinical crowns and in cusps that have been reduced 2-3 mm for coverage with amalgam. In these situations, slots provide more resistance than amalgapins and amalgam inserts. When amalgapins or slots are used as the only retention and resistance features, the restoration is susceptible to early fracture during matrix removal. When the technical requirements for placement of vertical pins can be met, they provide excellent retention and resistance form. Vertical pins should be placed at least 0.5 mm inside the dentinoenamel junction, at a depth of approximately 2 mm, and should protrude from the tooth approximately 2 mm. However, there are inherent risks involved with pin placement; these include crazing of tooth structure, perforation into the pulp or periodontium, and weakening of the amalgam restoration over the pins. The use of both vertical and horizontal pins may be limited by inadequate access; in these cases, alternate devices should be used. When a cusp has been reduced and increased resistance is needed, a ledge or peripheral step may be indicated. It must be remembered that this feature will result in a greater display of amalgam and may be esthetically unacceptable on a facial cusp. If esthetic appearance is a factor, horizontal pins may be used to reinforce a remaining facial cusp. Horizontal pins may also be used to splint or tie a remaining cusp to the restoration.(ABSTRACT TRUNCATED AT 250 WORDS)

Dental Amalgam↗
PubMed1989

Repair bond strength of glass-ionomer restoratives.

The repair bond strength of three different brands of glass-ionomer restorative was tested over time. In this laboratory study, immediate repair of glass ionomer was possible with all three brands; however, over time the repair bond strengths decreased at different rates for the different materials.

Dental Bonding↗