What's New in Dentistry

Although implants have been used for many years to replace missing teeth, it has been suggested that the success rate for implants placed in the posterior region of both the maxilla and mandible is lower than that for implants placed in the anterior region. Anatomic features, masticatory dynamics, and adequate implant selection could be significant determinants in long-term implant prognosis in the molar region. Reduced bone height frequently presents a challenge for implant placement in partially edentulous patients. To determine whether these factors affect implant success rates, researchers evaluated a consecutive group of 81 patients, each of whom had received implants to replace a single molar. The results of this study were published in the Journal of Periodontology (2006;77: 1528–1532). Inclusion criteria for patients were the presence of an implant replacing a molar between 2 natural teeth and follow-up data of at least 6 months (up to 125 months, with an average of 36 months). Smoking was reported by 18% of the patients. The replacement of a molar in the mandible was more frequent (87%), with 25% placed immediately after tooth extraction. Two implants were used to replace a single molar in 7 patients. The failure rate for this sample was 7.4% (6 implants). Of these, 3 of the failed implants had broken parts, and the other 3 failed because of infection or bone loss. No relationships were found among failure, complications, timing of implant placement, and smoking habits. The authors conclude that replacement of single maxillary and mandibular molars with an implant can serve as a good long-term and predictable treatment modality with low complication and failure rates.

The epidemic of AIDS has been recognized for about 25 years, and concern about the transmission of human immunodeficiency virus (HIV) is not new. Viruses can be transmitted in health-care settings, including dentistry, especially when standard infection control measures are not implemented. The transmission of HIV to health-care professionals can occur, but the risk of transmission is low, with a seroconversion rate of 0.1% after percutaneous exposure and 0.63% after mucous membrane contamination. An article published in the Journal of Dental Research (2006;85:794–800) assessed the current status of HIV infection in dentistry up to the end of 2005. In the United States, the Centers for Disease Control and Prevention had reported 57 occupational HIV infections in health-care personnel, mainly via percutaneous injuries from needle sticks or sharps. Of these, none were reported to be in dental health-care workers. In addition, 139 other cases of HIV infection or AIDS have been recorded among health-care personnel who have not reported other risk factors for HIV infection but who reported a history of occupational exposure to HIV-infected blood or laboratory material. Six of these cases have been in dental health-care personnel. Each of these had a history of percutaneous or mucous membrane exposure to HIV-infected body fluids. Worldwide, there are more than 300 reports (109 confirmed) of occupational transmission to health-care personnel, including up to 9 dental personnel. Researchers calculate a reported exposure to HIV by dentists of 0.5% per year. The authors emphasize that, with the use of standard infection-control measures, appropriate clinical and instrument-handling procedures, and safety equipment and safety needles, breaches in infection control will become vanishingly small.

It has been well established that the application of fluoride to newly formed enamel white spot lesions will promote remineralization. The most commonly employed fluoride-containing formulations, such as dentifrices, contain sodium fluoride. However, all past clinical trials have used newly formed incipient white spot lesions. The effect of fluorides on long-standing white spot lesions is questionable. However, a study published in Acta Odontologica Scandinavica (2006;64:115–122) used an examiner-blind protocol to observe long-standing white spot lesions over a period of 6 months to evaluate the effectiveness of fluoridated toothpastes on these lesions. A total of 39 subjects with at least 1 lesion participated in the study. They were randomly divided into 2 groups and were instructed to brush their teeth with toothpaste containing either sodium fluoride or amine fluoride. Lesions were measured with quantitative light-induced fluorescence, and alterations were quantified over the lesion area. The results indicated no significant differences in the influence of the fluoridated toothpastes. The authors concluded that fluoride did not seem to have any effect on long-standing white spot lesions.

Periodontal disease is characterized by loss of connective tissue attachment and alveolar bone and implies a loss of collagen fibers in the periodontal ligament subjacent to the pocket epithelium. Because support for the tooth root is lost, masticatory functions, such as food holding, biting, and chewing, may be affected. A study published in the Journal of Periodontology (2006;77:1491–1497) evaluated the effect of reduced periodontal support following periodontitis on masticatory behavior. The sample consisted of 11 subjects with reduced periodontal tissue support that resulted in 30% to 70% alveolar bone loss for at least 1 pair of opposing incisors. The researchers recorded the forces exerted when subjects used their affected incisors to hold and split various types of food. Age- and gender-matched healthy subjects served as a control group. None of the participants showed acute oral symptoms or severe periodontal inflammation. The test group used greater force when holding food between the teeth compared to the control group. The increase in bite force applied to split the food was slower and more hesitant for subjects in the test group compared to the control group. The authors concluded that reduced periodontal tissue support accompanied impaired regulation of masticatory forces because of faulty mechanoreceptive innervation of the periodontal ligament.

Bone loss around implants generally occurs during the remodeling process soon after implant placement and results in apical migration of the bone to the level of the first thread on the implant. Over time, this bone level remains relatively stable in most individuals. However, in some patients, bone loss is more pronounced. This additional loss of osseous attachment may be caused by peri-implantitis, occlusal stress, or both. A study published in the Journal of Dental Research (2006;85:711–716) evaluated a study group that consisted of 28 edentulous patients with interforaminal implants in place for an average of slightly more than 10 years. A total of 80 implants were monitored during the observation period. The objective was to determine the impact of biomechanical stress and inflammation on the implants in situ. Two stress groups with 14 patients each were established. One group was a low-stress situation with single implants, and the other group consisted of an increased-stress situation with splinted implants. The degree of inflammation was categorized using an index with 4 inflammatory parameters. Peri-implant bone loss was calculated from digital panoramic radiographs. A clear difference was seen between single-standing and splinted implants, with splinted implants showing higher inflammation scores. The authors showed that, whereas stress and inflammation alone may not necessarily be detrimental factors, the presence of stress heightens peri-implant bone loss significantly as inflammation increases.