Michael Buonocore and the Eastman Dental Center: a historic perspective on sealants.

Dr. Michael Buonocore is known for his innovative research on the preparation of the enamel surface with a weak acid to enhance adhesion of an organic plastic chemical sealant and the polymerization in situ of a sealant with ultraviolet light. His co-workers at Eastman Dental Center aided and extended his research findings. The purpose of his original research was the development of a sealant to prevent occlusal caries on posterior teeth. However, the major impact of his work has been the development of adhesive restorative techniques. Although it has been demonstrated that (i) bacteria tend to die out and caries does not progress if early caries lesions are inadvertently sealed, (ii) sealant retention rates are favorable, and (iii) sealants are cost-effective, the use of sealants by the profession is still far short of early expectations.

Mercury release from dental amalgams: an in vitro study under controlled chewing and brushing in an artificial mouth.

The release of mercury vapor from class I amalgam restorations prepared in human molar teeth was studied during chewing simulations in an artificial mouth of a bi-axial servo-hydraulic mechanical test system. So that the total mercury released from the restoration over a fixed time could be determined, a closed chamber surrounded the envelope of chewing motion. In addition, the influence of sampling frequency on mercury release was corrected by the use of different sampling frequencies over a fixed time interval of mercury release measurement and extrapolation to zero sampling time. Thus, a combination of a closed environment and an extrapolation method to determine the mercury release under continuous sampling was used to determine the mercury released under normal breathing conditions. The measured mercury release rate data were used to calculate the potential daily mercury dose in a patient due to a single amalgam restoration, following the method previously outlined by Berglund. The mercury release from both a conventional and a high-copper amalgam was evaluated at different age intervals after the restoration was placed in the teeth. The results show that while the age of the amalgam and the amalgam type influence the extent of mercury release during the initial non-steady-state conditions, the steady-state value of mercury daily dose due to a single amalgam filling is 0.03 micrograms/day, which is well below the calculated threshold-limiting value (TLV) of 82.29 micrograms/day considered dangerous for occupational exposure in the United States.

A clinical evaluation of a radiopaque material in the restoration of anterior and posterior teeth.

The clinical performances of Adaptic and Radiopaque Adaptic restorative materials are compared according to their properties of retention, marginal integrity, and color change. The advantage of radiopacity in Class I and Class IV restorations of anterior and posterior teeth is discussed.

Occlusal composite restorations: 4-year results.

A study was performed to determine the success of a conservative cavity preparation using the principle of sealing for prevention rather than cavity extension for prevention. A total of 332 restorations were placed in 240 teeth of 110 subjects, aged 6 to 14, with a mean age of 8 years. After 4 years, 205 restorations were examined. Caries appeared in 13 teeth and sealant wear occurred in 14 restorations. Complete sealant loss was observed in eight restorations and partial loss in 38, leaving 156 restorations with complete retention of the sealant. These preliminary results show that conservative cavity preparation with sealing for prevention is a successful technique that conserves valuable tooth structure.

Microscopic appearance of enamel white-spot lesions after acid etching.

Ultrastructural changes in surface characteristics of enamel white-spot lesions were compared with changes in the adjacent clinically sound enamel after they were etched with 30% phosphoric acid. Ten human permanent first molars exhibiting natural white-spot lesions were used as study specimens. The lesion surfaces and their adjacent sound enamel were etched with 30% phosphoric acid for 60 seconds. Specimens were then evaluated by polarized light microscopy, scanning electron microscopy, and energy-dispersive spectroscopy. The acid etching produced a porous surface on both the white-spot lesion and the surrounding sound enamel. However, the lesion surface appeared to be more resistant to acid and dissolved less than adjacent enamel. This difference in acid solubility produced a steplike appearance between a white-spot lesion and its adjacent enamel surface. Energy-dispersive spectroscopy demonstrated no difference in relative calcium-phosphorus ratios among the acid-etched white-spot lesion, acid-etched sound enamel, and unetched sound enamel.

Milk and egg albumen are superior to human saliva in preserving human skin fibroblasts.

The purpose of this in vitro study was to compare egg albumen, whole bovine milk, human saliva, and tissue culture medium (MEM) for effect on the viability of human skin fibroblasts and their osmolalities. Confluent monolayers of fibroblasts were grown. Growth medium was poured off and dishes were divided into five groups, 15 dishes each of: 1) chick egg albumen; 2) fresh whole milk; 3) human saliva; 4) tissue culture medium; and 5) bench-dried storage without any media. After 15, 45, and 90 min the average number of vital cells was measured using the trypan blue dye exclusion test. Tissue culture medium represented the best preservation media for human skin fibroblast cells (92.8% at 45 min, 87.6% at 90 min). No significant differences were observed between milk and albumen, with a majority of the cells surviving after 90 min (67.6% and 70.2%, respectively). Human saliva, due to its hypotonicity, markedly swelled the cells, causing decreased cell viability (27.4% at 90 min). Bench-dried cells, as expected, showed no viable cells as early as 15 min. The osmolality of the MEM, milk and egg albumen ranged between 251-298 mOsm/kg, whereas the saliva was hypotonic, with an osmolality of 73 mOsm/kg.

Fluoride exchange from glass ionomer preventive resin restorations.

The purposes of this in vivo study were to determine if placing a sealant over a glass ionomer restoration modifies its fluoride release, and to examine the effect on glass ionomer of a 4-min application of topical fluoride. Fluoride release from glass ionomer preventive resin restorations placed in 21 bovine teeth was measured before and after removing their sealants. Fuji II, Ketac Silver, and Fuji LC were evaluated, representing the three generations of glass ionomers. Fluoride was extracted from the restorations by incubating the specimens in 5 ml deionized water and was measured by specific ion electrodes at 1 and 2 days, then once weekly for 7 weeks. The results indicated that fluoride release was not significantly different in pattern or quantity in the three types of ionomer (P > 0.05). A significant reduction in fluoride release occurred when the restorations were covered with a sealant when compared with control restorations of the same materials (P < 0.001). After removing the sealant from the glass ionomer preventive resin restorations, a significant release of fluoride occurred when compared with sealed restorations (P < 0.001). After 63 days in water, the unsealed restorations were subjected to a 4-min topical APF treatment and reimmersed in water for an additional 27 days to examine the ability of the various materials to absorb fluoride. The fluoride-depleted restorations treated with fluoride released significantly more fluoride than fresh, untreated ionomer restorations (P < 0.001) or amalgam restorations. As a result of fluoride release, the glass ionomer preventive resin restoration may afford chemical protection to the tooth if sealant loss occurs.

Oral soft tissue manifestations and CD4 lymphocyte counts in HIV-infected children.

This study investigated the prevalence of oral soft tissue lesions in children infected with HIV and the relationship of CD4 lymphocyte levels with the prevalence of those lesions. Sixty HIV-positive children enrolled in the Children's Hospital AIDS Program (age 5.8 +/- 3 years) were selected for study. Only five subjects (8%) had healthy gingiva and a low mean plaque index (22%). The remainder had gingivitis or periodontitis with relatively high plaque indices (47, 55, and 94%, respectively). A declining CD4 lymphocyte count (1357 to 35) was associated with an increasing severity of gingival disease.

Fluoride uptake by proximal surfaces from professionally applied fluorides: an in vitro study.

This study was performed to examine the uptake of fluoride by mesial enamel surfaces of extracted teeth from different types of topical fluoride. Forty-eight extracted human molars and twelve premolars were randomly divided into four groups and mounted in twelve wax blocks with five teeth in proximal contact in each block. Each group was treated for four minutes with either 1.23 percent acidulated phosphofluoride conventional gel, thixotropic gel, or foam in lined trays, or 2 percent neutral sodium fluoride solution applied with a cotton tip applicator. Acid-etch biopsies were performed three times to indicate the amount of fluoride uptake at three different depths. The results demonstrated that there was a statistically significant increase in fluoride uptake in the surface layer with both gels and foam (1150, 1058 and 1120 ppm F), whereas there was an insignificant increase with the fluoride solution (27 ppm F). In the deepest layer, the thixotropic fluoride produced the greatest fluoride uptake (919 ppm F) in comparison with the uptake from conventional gel (383 ppm F), foam (297 ppm F), or solution (118 ppm F).

Occlusal restoration using fissure sealant instead of "extension for prevention".

This study was conducted to determine the success of a conservative cavity preparation using the principle of "sealing for prevention" rather than cavity "extension for prevention". Three hundred and twenty one restorations were placed in 234 teeth of 110 subjects, ages six to fourteen, with a mean age of eight years. After three years, 273 restorations were examined. Caries appeared in ten teeth and sealant wear occurred in sixteen restorations. Complete sealant loss was observed in two restorations and partial loss in thirty-nine, leaving 224 restorations with complete retention of the sealant. These preliminary results demonstrate that conservative cavity preparation with sealing for prevention is a successful technique which conserves valuable tooth structure.