Quintessence International, 09/2000

Recent clinical studies show 2-unit cantilevered resin-bonded fixed partial dentures to be as retentive or more retentive than their fixed-fixed counterparts. The fact that the 2-unit prosthesis is successful adds value to the clinical use of resin-bonded fixed partial dentures because the single-abutment prosthesis is even simpler and more cost effective than fixed-fixed designs. However, there is no evidence-based information relating to design principles for abutment preparation and framework design for the single-abutment, single-retainer prosthesis. The aim of this report is to suggest principles of design for the 2-unit cantilevered fixed partial denture, based on information gained from studies on fixed-fixed designs.

Minimal intervention techniques are generally considered in relation to initial carious lesions. However, it appears logical to apply the same principles to extensive cavities as well as to the replacement of failed existing restorations. As the cavity becomes larger, there is an increasing need to consider protection of remaining cusps because they become seriously weakened by loss of the central core of the crown and therefore become subject to the development of splits at the base. However, it is possible to develop a protective cavity design without undue sacrifice of remaining tooth structure, at the same time that maintenance of occlusal anatomy and correct contact with the opposing arch are ensured. For larger cavities, special consideration needs to be given to the strength of the restorative material. Glass ionomer is relatively brittle and should not be exposed to undue occlusal load. Resin composites cannot be regarded as universal in their physical properties, and placement is time-consuming. A lamination technique is often useful, combining the advantages of both glass ionomer and resin composite. Amalgam should not be entirely discarded as an option because it has greater strength than both glass ionomer and resin composite and is still useful for the restoration of extensive cavities and for protection and retention of weakened cusps. Minimal intervention principles, designed to limit the loss of natural tooth structure, should be applied to all restorative dentistry. None of the available restorative materials is entirely satisfactory in the long term.

Objective: The aim of this investigation was to evaluate the clinical performance of a new compomer restorative system, Dyract AP, placed in combination with Non-Rinse Conditioner and Prime & Bond NT in permanent posterior teeth. Method and materials: Fifty Class II and 41 Class I restorations were placed in 39 patients by 1 dentist. The restorations were evaluated directly, with modified US Public Health Service criteria, and indirectly, with color slides and polyvinyl siloxane impressions, at baseline and 6 months and 1 year after placement. Preoperative and 1-year postoperative bitewing radiographs were also taken. Results: All 82 restorations available for 1-year evaluation were in situ. No postoperative sensitivity or pulpal problems were reported. Four Class II restorations (4.9%) failed because of partial fracture or recurrent caries. The percentages of Alfa score for each criterion were color match, 95.1%; marginal discoloration, 57.3%; marginal integrity, 35.4%; anatomic form, 98.8%; and surface texture, 91.5%. The average wear rate of Dyract AP was low (18.5 ± 11.7 µm at 6 months and 35.7 ± 13.6 µm at 12 months). Conclusion: The excellent handling characteristics, the good clinical performance, and the improved wear resistance suggest that this compomer will provide reliable direct tooth-colored restorations in stress-bearing areas.

A thorough physical examination of the head and neck should be included as part of the evaluation of every dental patient. Although they most often represent a self-limited inflammation, a benign neoplasm, or a congenital anomaly, neck lesions can also be malignant. Because the pathologic lesions that can arise in the neck are varied and diverse, the diagnostic thought process should be orderly and inclusive so that a reasonable differential diagnosis can be established and prompt, effective treatment can be rendered.

This case report describes the oral rehabilitation of a female child with hypohidrotic ectodermal dysplasia over a 6-year time period. It demonstrates the need for periodic modification and replacement of a prosthesis, an orthodontic appliance, and a gingivoplasty. Although the initial treatment plan was considered to be a compromise due to limited cooperation, an improvement was observed in the patient's social behavior as a consequence of her dental treatment. The effects of unavoidable changes in the dental team over 6 years are also discussed.

Objective: This study determined the amount of light energy transmitted through various densities of cured resin composite and human dentin when 2 different light intensities were used. Method and materials: The maximum light energy (mW/cm2) transmitted through disks (0.46 to 5.85 mm thick) of 7 resin composites and human dentin was measured when either a Standard or a Turbo light guide was attached to a curing light. The effects of the 2 light guides, the specimen thickness, and type of specimen dentin on light energy transmission were determined. Results: The mean light energy reading at the surface of the specimens was 682.1 mW/cm2 with the Standard light guide and 1,014 mW/cm2 with the Turbo light guide. For all the specimens, there was an exponential decrease in light energy transmitted as the specimen thickness increased. The analysis of covariance showed that the specimen, thickness, and light guide all had a statistically significant effect. Significantly more light energy (about 42%) was transmitted through the specimens when the Turbo light guide was used. Conclusion: When the Turbo light guide was used, about 42% more light energy was transmitted through the cured composite specimens. There was an exponential decrease in the light energy transmitted through 7 resin composites and dentin as the specimen thickness increased.

Objective: The purpose of this investigation was to evaluate the microleakage of Class V lesions restored with a compomer material (Dyractflow) using 2 single-bottle bonding systems. Method and materials: Sixty-four Class V cavity preparations were made on 32 sound, extracted human premolars, 1 preparation on the facial surface and 1 on the lingual surface. Teeth were then randomly divided into 2 groups. Group 1, which served as the control group, was restored as follows: group 1a, facial surface with PQ1 single-bottle bonding system plus TPH resin composite; group 1b, lingual surface with Prime & Bond NT single-bottle bonding system plus TPH. Group 2 was restored as follows: group 2a, facial surface with PQ1 plus Dyractflow compomer material; group 2b, lingual surface with Prime & Bond NT plus Dyractflow. After 24 hours of storage in water and subsequent thermocycling, each specimen was immersed in 0.2% basic fuchsin dye for 24 hours. The teeth were sectioned longitudinally and horizontally, and dye penetration at enamel and cementum margins was viewed at 330 magnification by 2 independently calibrated evaluators. Specimens were evaluated as either having leaked or not having leaked. Results: No statistically significant differences in microleakage were noted between group 1 and group 2 specimens. Conclusion: Both single-bottle bonding systems, PQ1 and Prime & Bond NT, demonstrated equal effectiveness in reducing microleakage beneath compomer and composite restorations.

For Minnesota dentists with long memories, Dr Jack Echternacht is a legendary figure. He graduated from the University of Minnesota School of Dentistry in 1943. Except for a 3-year enlistment in the Navy during World War II, he has made his home and his professional life in Brainerd, on the edge of Minnesota's lake country. A few years after he started his general practice, reports began to appear about the striking reduction of dental caries in children's teeth when fluoride was placed in the drinking water. Excited by these prospects for better oral health, Dr Echternacht led a Chamber of Commerce initiative in 1954 to introduce fluoride into Brainerd's water supply. What seemed at first an easy victory turned into a 30-year struggle. Dr Echternacht's determination, persistence, and leadership during this fight for fluoridation led to his selection as a moral model in dentistry.