What's New in Dentistry

Association between coronary artery disease and periodontitis. Atherosclerosis remains the leading cause of morbidity and mortality in developed countries. Periodontal disease is one of the most frequent chronic infections in humans. In recent years, there has been an increasing interest in the impact of oral health on atherosclerosis and subsequent cardiovascular disease. But is there any relationship between these two disease entities? A study published in the Journal of Periodontology (2009;80:378–388), investigated the association between chronic periodontitis and cardiovascular risk markers. The sample consisted of 40 patients with periodontitis and 40 healthy gender-, body mass index-, and age-matched individuals who were compared by measuring their total cholesterol, high-density lipoprotein, low-density lipoprotein, triglycerides, levels of cytokines, antibodies against oxidized low-density lipoprotein, and total and differential white blood cell counts. The results of these comparisons between these two groups of individuals showed that the levels of triglycerides and high-density lipoprotein in patients with periodontitis were significantly higher and lower, respectively, compared with controls. Total cholesterol, low-density lipoprotein, and lipid peroxide levels were the same in both groups. Interleukin-6 antibodies against oxidized low-density lipoprotein and leukocyte and neutrophil counts were significantly higher in patients with periodontitis. Although these observations may sound very confusing and complicated, the authors state that these results confirm and further strengthen the suggested association between coronary artery disease and periodontitis.

Continuous vs discontinuous distraction osteogenesis. Distraction osteogenesis has been used regularly in oral and maxillofacial surgery in recent years. The technique is based on the regenerative properties of bone. In order to elongate hypoplastic bone, the bone needs to be osteotomized, after which the bone segments are gradually pulled apart. The callus in the resulting gap between the bone segments is eventually replaced with calcifying tissue. Many studies have been conducted to find the optimal distraction rhythm. There are basically two options: continuous and discontinuous. The most typical type of activation is discontinuous, where activations are made once or twice a day. However, clinicians have proposed that an automated continuous activation could be better at creating a more favorable osteogenic response. But is this assumption true? A study published in the Journal of Oral and Maxillofacial Surgery (2009;67:818–826) compared these two different rhythms of distraction activation. The sample for this study consisted of experimental animals that were subjected to distraction of the nasal bones. A custom-made continuous distractor was used to perform automatic nonstop distraction in one group of animals. In the other group, traditional discontinuous distraction of the bones was performed. The authors then compared the differences between these two techniques using radiography, ultrasonography, and microcomputed tomography. The results of the ultrasonographic bone-fill scores correlated significantly to actual bone volume in contrast to radiographic bone-fill scores. Bone volume was significantly higher in the continuous distraction group compared with the discontinuous distraction group. The authors conclude the continuous distraction results in accelerated osteogenesis compared with discontinuous distraction.

Specific antibiotics are effective in treating periodontal disease. Traditional nonsurgical periodontal therapy consists of scaling and root planing followed by introduction of proper oral hygiene techniques. Using this approach, the teeth are typically treated in quadrants in a step-wise approach over several appointments. However, it has been suggested that this type of approach could carry the risk for recontamination of already-treated areas from untreated sites that still contain large amounts of periodontal pathogens. Therefore, a full-mouth approach consisting of complete scaling of all areas of the mouth followed by disinfection with antibiotics could perhaps improve the outcome of nonsurgical periodontal therapy. That hypothesis was tested in a double-masked, placebo-controlled, randomized longitudinal study that was published in the Journal of Periodontology (2009;80:364–371). The sample consisted of 50 patients with moderate periodontal disease. The sample was randomly divided into two groups. Both groups received complete-mouth root planing and scaling performed within 48 hours. Then, half of the subjects received metronidazole and amoxicillin three times a day for 7 days. The other group received a placebo over the same time interval. The patients in both groups were reevaluated after 6 months. At this follow-up interval, the overall mean probing depth decreased in both groups by a similar amount. However, the antibiotic group had a significantly lower mean number of persisting pockets and bleeding upon probing compared with the placebo group. In addition, 6 months after the beginning of the experiment, only 0.4 persisting pockets were still present in the antibiotic group, while 3.0 persisting pockets were still present in the placebo group. The authors conclude that systemic metronidazole and amoxicillin along with full-mouth nonsurgical periodontal debridement significantly reduce the need for additional periodontal therapy.

Short implants are successful in restoring posterior occlusion. Although implants come in a variety of lengths, it has been reported in the past that implants less than 10 mm in length in the posterior part of the mouth generally have a lower success rate than longer implants. However, placement of posterior implants is often subject to anatomic limitations such as the inferior alveolar nerve. Methods to increase the vertical height of the posterior mandible, such as autogenous bone augmentation have shown high levels of morbidity and low success rates. Another option would be to simply place shorter implants when the anatomy prevents placement of a longer implant. But would these be successful? That question was answered in a study that was published in the Journal of Oral and Maxillofacial Surgery (2009;67:713–717). The sample consisted of 124 patients who had 335 implants placed that were 8-mm in length. The sample consisted of 35 male and 89 female patients with a median age of 56 years and an age range of 18 to 80 years at the time of implant placement. All of the implants were restored with fixed prostheses. Of these restorations, 245 were splinted together, whereas 75 were restored individually. These patients were reevaluated after restoration to determine the survival rate. The authors found that 331 of 335 implants integrated successfully. In the two cases that failed, the sites were grafted and short implants were replaced 5 months later and eventually restored. Based upon these findings, the authors calculated the survival rate for the 8-mm implants placed in the posterior mandible was 99% from initial placement to functional prosthesis for up to 2 years. The authors conclude that placement of short dental implants is a predictable treatment method for patients with decreased posterior mandibular bone height.

Tissue engineering can be used to reconstruct the mandible. Reconstructing large defects in the craniomaxillofacial skeleton is extremely difficult, despite continued improvement in reparative materials and surgical techniques. Jaw reconstructions are particularly difficult because both bone and a functional dentition must be restored. Currently jaw defects require autologous bone grafts, followed by placement of titanium dental implants. However, these surgeries have significant drawbacks including limitations on the quantity of bone as well as difficulties in managing the placement of the dental implant. It would be ideal if surgeons could incorporate tooth buds into the bone graft, so that the grafted bone would be maintained, and teeth would be available to provide function for the patient. A study published in the Journal of Oral and Maxillofacial Surgery (2009;67:335–347) tested whether this hypothesis is feasible. These researchers investigated simultaneous mandibular bone and tooth reconstruction using a minipig as the experimental model. The authors created both tooth and bone constructs from third molar tooth tissue and iliac-crest bone marrow-derived osteoblasts isolated from the minipigs. These constructs were grown in the laboratory and then reimplanted back into the same pig as an autologous reconstruction. Then, these implanted bone and tooth constructs were reevaluated after 12 and 20 weeks using radiography, ultrahigh-resolution volume computed tomography, histology, and immunohistochemical analyses. The results of this study showed that small tooth structures were identified in the grafted material and consisted of organized dentin, enamel, pulp, and periodontal ligament tissues surrounded by new bone. No dental tissues formed in the implants without tooth-bud cells. In this pilot study, the authors conclude that the feasibility of tissue engineering approaches for coordinated tooth and mandibular reconstruction may someday be possible in humans.