Biochemical comparison of plaque fluid on tooth and acrylic surfaces during a sucrose challenge.

Previous studies have investigated variations in dental plaque fluid composition within a single mouth after a sucrose exposure. The purpose of this study was to determine a potential source of calcium and phosphorus in plaque by comparing the pH, calcium and phosphorus concentrations in plaque fluid obtained from an acrylic appliance with samples taken from supragingival tooth surfaces within the same individual after a sucrose challenge. Separate plaque samples from 14 individuals were collected from an acrylic appliance or tooth surfaces within same individual before and 15 min after a 20% sucrose rinse. Each plaque sample was centrifuged and nanolitre samples of plaque fluid were analysed for pH with a pH microelectrode, for total calcium concentration by atomic absorption in a graphite furnace, and for phosphorus concentration by spectrophotometry. There was an increase in the calcium and phosphorus concentration in the plaque after the sucrose challenge and a significant increase in calcium and phosphorus concentrations in the plaque taken from the teeth compared to the acrylic surfaces. The results indicate that the increased total calcium and phosphorus in plaque during a sucrose challenge is probably derived from the demineralization of enamel or extracellular demineralized components.

Reduction of caries and of demineralization around orthodontic brackets: effect of a fluoride-releasing resin in the rat model.

The effectiveness of fluoride in reduction of caries is well known. This study examined the ability of a fluoride-releasing resin to reduce caries, as well as demineralization around orthodontic brackets, by using the Sprague-Dawley rat as a model. Eighteen-day-old rats were infected with cariogenic Streptococcus sobrinus 6715. After infection was confirmed, standard orthodontic techniques were used to bond miniature orthodontic brackets to the lingual surfaces of maxillary first molars, with either a fluoride-releasing resin (group I) or a conventional resin (group II). A control group was infected but not bonded (group III). Bonding was done at age 34 days. Rats were fed a cariogenic diet and were killed at age 72 days. Lingual surfaces of maxillary first molars were evaluated for area of demineralization, and mandibular molars were scored for caries. Mean percent area of demineralization for group I was 4.7%, for group II 35.7%, and for group III 0%. The difference between groups I and II was statistically significant (p < 0.01). Mean mandibular molar enamel carious lesion unit count for group I was 9.8, for group II 16.3, and for group III 13.7. Group I had significantly fewer lesions than groups II and III (p < 0.01), and group II had significantly more lesions than group III (p < 0.01). These results indicate that a fluoride-releasing resin reduces demineralization at the site of application and reduces caries at distant sites in the experimental rat model.

Orthodontic treatment in the mixed dentition for the general dentist.

Mixed dentition treatment is an important subject because early treatment could not only correct the occlusion but also may ensure normal development of the teeth. Proper arch form and dental relationships in the mixed dentition lessen the need for additional orthodontic treatment. The objectives in mixed dentition orthodontic therapy are to correct dental arch irregularities, occlusal and jaw relation abnormalities, and to eliminate functional interferences.

Comparison of electrosurgery with conventional fiberotomies on rotational relapse and gingival tissue in the dog.

The relapse tendency of orthodontically rotated teeth after electrosurgical circumferential fiberotomies and after conventional scalpel blade surgical procedures was demonstrated with a split-mouth procedure involving the maxillary second incisors of five mongrel dogs. The second incisors were rotated orthodontically an average of 63.5 degrees over a 4-month period. Electrosurgical circumferential fiberotomies were performed on the designated second incisors, and circumferential fiberotomies with a scalpel blade were performed on the contralateral incisors. The teeth were retained for 1 month and relapse was measured 2 months postretention. Wound healing was demonstrated by measurement of sulcus depths and facial gingival recession preoperatively and at 1, 2, 3, 4, and 9 weeks after surgery. In both groups, the sulcus depths had decreased about 2 mm and the facial gingiva had receded 0.3 mm 9 weeks after surgery. Two months postretention there was an average 25% relapse in the teeth treated by means of a circumferential fiberotomy with a scalpel blade compared to an average 23% relapse in those treated by means of a circumferential fiberotomy with electrosurgery. No significant difference was seen between the two techniques.

Plaque fluid pH, calcium and phosphorus responses to calcium food additives in a chewable candy.

Fourteen subjects between 7 and 17 years of age with an equal distribution of low and high caries activity were given: (1) a 10% sucrose rinse, (2) a reference candy, (3) a reference candy with 3% dicalcium phosphate dihydrate, and (4) a reference candy with 0.75% calcium lactate on four different occasions. Plaque samples were collected before and at 15-min intervals after the sucrose rinse or food challenge for a period of 1 h on each occasion. Plaque samples were centrifuged and the extracellular plaque fluid analysed by a microtechnique for pH, total calcium and inorganic phosphorus concentration. There was no significant increase in calcium and phosphorus in plaque fluid for the group using candy with added calcium compared to the reference candy or sucrose rinse. There was no significant difference between the measurements in subjects grouped as caries active or inactive. The results suggest no benefit can be expected from adding dicalcium phosphate dihydrate and calcium lactate to candy to decrease demineralization during a cariogenic challenge.

Micro-analytical determination of pH, calcium, and phosphate in plaque fluid.

Micro-analytical techniques for the determination of calcium, phosphate, and pH in a small volume (less than 0.25 microliter) of plaque fluid are described and evaluated. The accuracy and the precision of the techniques were compared with those for standard macrotechniques applied to a large pooled plaque fluid sample. The results obtained for the micro-analysis of pooled plaque fluid were in excellent agreement with those obtained by macromethods. The described techniques were also used to analyze plaque fluid obtained from single quadrants of the oral cavities of five individuals. In this fashion, it was determined that, although a significant variation in plaque fluid composition exists between the quadrants, a greater variation exists between subjects. Analyses of plaque fluid obtained from six individuals, following sucrose exposure, were also conducted. The pH value of the fluid changed with time, following a typical Stephan curve, with a minimum value occurring between 15 and 30 minutes; following this, the pH increased to a value near that for resting plaque. An inverse relationship between pH and calcium and phosphorus concentrations was observed. It is noted that the described techniques are sensitive enough to carry out the above analyses both accurately and precisely using plaque obtained from a single quadrant.