What's New in Dentistry

Professionally applied fluoride has little benefit in low-caries children. Regular professional application of fluoride gel is a strategy for reducing initial pit and fissure caries in children. However, some children should have a lower susceptibility to caries simply because they regularly use a dentifrice containing fluoride. Is there an added benefit of professional application of fluoride gel in children who are already exposed to fluoride toothpaste? That question was answered in a study that was published in the Journal of Dental Research (2005;84:418–421). In their investigation, the authors evaluated over 500 children between the ages of 9.5 to 11.5 years of age who were being followed in three large pediatric dental clinics. The drinking water in the communities involved in this study was not fluoridated. All subjects used fluoride toothpaste for their at-home oral hygiene procedures. Every six months for four years, each of the subjects in the sample received the professional application of a gel to their teeth. Half of the sample received a fluoride gel and the other half received a placebo gel with no fluoride. Then after four years, the authors evaluated the incidence of caries in this population. The results of this study showed that the number of tooth surfaces saved from caries development by a fluoride gel application after four years was very low. The authors concluded that professionally applied fluoride gel showed no statistically significant effect on the incidence of dental decay in low-caries children who were routinely using toothpaste that contained fluoride.

Immediate loading of posterior maxillary implants decreases implant stability. Immediate loading of single-tooth implants has become more common in the past five years. Early loading of multiple splinted implants in the mandible has been studied clinically and has resulted in relatively high success rates. However, immediate or early functional loading of implants placed in the posterior maxilla has not been evaluated experimentally. In a recent study published in the International Journal of Oral and Maxillofacial Implants (2005;20:39–47), researchers assessed the stability of implants placed in the posterior maxillae of experimental animals and functionally loaded at various time intervals after initial placement. In this investigation, the authors used a sample of nine minipigs to test their hypotheses. Initially, the posterior teeth in each animal were extracted, and the sites were allowed to heal for three months. Then, six implants were placed on each side of the posterior maxilla using standard clinical techniques. The implants were restored with fixed provisional prostheses immediately after placement or after healing periods of 1, 2, 3, 4 and 5 months respectively. At placement and at the time of restoration, implant stability was assessed. Then the animals were allowed to function for six months, and the implants were again assessed to determine their stability. The results of this study showed that implant stability was significantly influenced by the healing period. Implant stability decreased after 1 to 3 months of healing and increased after a loading period of four months. A total of 13 out of 24 immediately loaded implants were lost. When implants were loaded after healing period of from 1 to 3 months, 30 out of 48 implants were lost. However, when implants were loaded after 4 or 5 months, only 3 out of 36 implants were unsuccessful. In conclusion, the authors showed that in the posterior maxilla, implant loading after healing periods of 1 to 3 months did not improve implant survival. Implant stability did not begin to increase until after a healing period of four months. The authors suggest caution when considering immediate or early loading of implants in the posterior maxilla.

Ultrasound does not stimulate osteoconduction. Osteoconduction refers to bone formed by guided tissue regeneration. This process is made possible by using osteoconductive membranes that cover a bone defect, preventing soft tissue in growth into the defect. In this way, a confined space is obtained into which bone cells are allowed to migrate in order to fill-in the osseous defect. Osteoconduction has been used extensively in periodontology to regenerate periodontal defects. However, the process of osteoconduction takes a substantial amount of time. In order to enhance the response, ultrasound has been used to attempt to stimulate the bone healing process. Ultrasound is a mechanical pressure wave with a frequency above the threshold of human hearing. It has been used in orthopedics in certain cases of delayed or non-union of bone with high success rates. In a study published in the International Journal of Oral and Maxillofacial Implants (2005;20:181–186), researchers tested whether ultrasound could accelerate the osteoconduction that occurs during the process of guided tissue regeneration. This study was performed in a sample of 64 rats. Initially, a 5-millimeter diameter circular hole was created bilaterally in the mandibles of all animals. Both defects were covered with a membrane to encourage osteoconduction and prevent soft tissue in-growth. During the healing period, ultrasound treatment was applied to half of the defects, and a placebo treatment was applied to the other half at two and four weeks, respectively. The remaining defect area was measured using microradiographs in both groups. The results showed that there was no significant difference in the percentage of defect closure between the groups. The authors concluded that there is no evidence that low-intensity pulsed ultrasound stimulates osteoconduction in bone defects in rat mandibles.

Implants can be successful in patients with chronic periodontitis. Patients with generalized aggressive or chronic periodontal disease often lose teeth due to significant bone loss and require replacement of these teeth to improve either esthetics or function or both. A concern in the past has been that placing implants in patients who are susceptible to periodontal pathogens would be a risky procedure and could result in eventual failure of the implants due to attachment loss. However a study published in the Journal of Periodontology (2005;76:534–543), has shown that implants can be successful in patients with generalized chronic or aggressive periodontal disease. The sample for this study consisted of 39 partially edentulous patients who had a total of 150 implants placed to restore their open spaces. The sample was divided into three subgroups: 15 subjects who were being treated for generalized aggressive periodontitis; 12 patients who were being treated for generalized chronic periodontitis; and 12 periodontally healthy patients. The subjects were examined initially, and then at three month intervals up to three years after their implants had been restored. The usual periodontal clinical parameters were assessed, including probing depth, gingival recession, attachment level, gingival index, and plaque index, as well as sampling and identification of the composition of the bacteria present around teeth and implants. After three years, the authors found that implant success rates were relatively high for all groups. Implant success rates were 100% in the periodontally healthy and generalized chronic periodontal patients, and 95.7% in the maxillae and 100% in the mandibles of the generalized aggressive periodontal patients. Bone loss was slightly greater after three years at implants and teeth in the generalized aggressive periodontal patients than in the other two groups. The results of this study show that oral rehabilitation can be performed successfully in patients with generalized aggressive and chronic forms of periodontal disease.

Fluoride does not penetrate plaque biofilms. Fluoride rinses are a common way to deliver the fluoride effect to tooth enamel. However, in some mouths areas of plaque may still remain on the teeth, when the fluoride rinse is being used. Does fluoride penetrate a plaque biofilm in order to reach the enamel surface beneath? That question was addressed in a study published in the Journal of Dental Research (2005;84: 451–455). In this study, a group of adults wore a bonded attachment on their posterior teeth for a seven-day period. They were instructed to perform their usual oral hygiene techniques during that time interval. However, the construction of the bonded attachment permitted plaque to be retained on this intraoral device. Then after seven days, the bonded attachment was removed, and the plaque biofilms that remained on the attachments were tested in the laboratory by immersing these attachments in sodium fluoride solution for 30 to 120 seconds (equivalent to tooth brushing). Then the plaque biofilms were sectioned throughout their depth, and the fluoride content of each section was determined with the use of a fluoride electrode. The results showed that exposure to sodium fluoride for 30 to 120 seconds increased plaque fluoride concentrations near the saliva interface; however, the fluoride concentrations near the enamel surface remained low. The authors concluded that penetration of fluoride into plaque biofilms during brief topical exposure is restricted and therefore limits any anti-caries effect in these areas of the tooth.