What's New in Dentistry

Some individuals have offensive breath odor. Many different types of mouth rinses have been developed in the past to combat this problem, and the effectiveness of these agents has been variable. However, a recent study published in the Journal of Periodontology (2001;72:1183–1191), suggests that the addition of chlorhexidine to mouth rinse is more effective than the traditional products. The sample for this study consisted of 12 healthy medical students. They were not allowed to brush their teeth or use dental floss for a period of 12 days. During this time, the participants were only allowed to rinse with one of three types of mouth rinses twice each day. These mouth rinses contained either: chlorhexidine with alcohol, chlorhexidine with sodium fluoride, or chlorhexidine with cetylpyridinium chloride and zinc lactate. After the twelve-day interval, the breath odor of each individual was measured with a sulfide monitor to determine the amount of sulfides. The tongue coating was also scraped to determine the numbers of bacteria present. The results of this study showed that all three mouth rinses containing chlorhexidine were effective at reducing mouth odor. But the mode of action of these materials was not clear. The most effective mixture was chlorhexidine combined with cetylpyridinium chloride and zinc lactate. The authors believe that the effectiveness was probably due to the neutralizing of the sulfide-containing volatiles by the combination of these chemicals.

Bruxism often occurs at night when an individual is asleep. A recent study published in the Journal of Dental Research (2001;80:1940-1944), evaluated the relationship between bruxing and the levels of sleep in subjects with a history of sleep bruxism. The sample for this study consisted of 20 subjects. Ten of these individuals were confirmed “sleep bruxers”. They were matched with 10 normal subjects who did not brux their teeth. All individuals spent two consecutive nights in a sleep laboratory. The first night was used for subjects to become acclimated and accustomed to sleeping in the facility. During the second night, the amount of bruxing, muscle activity, and the level of sleep were evaluated and compared among the subjects. The results showed that microarousal is a primary factor in the initiation of masticatory muscle activity during sleep. The authors believe that sleep bruxism should be considered an oromotor activity secondary to microarousal. In the study, the authors demonstrated that about 70 to 80% of masticatory muscle activity episodes are preceded by activity in the suprahyoid muscles. The activation of these muscles is a classic EMG sign of sleep arousal.

For several years, researchers have known that the pH of plaque decreases and becomes more acidic after meals. It is also known that chewing gum increases saliva flow and buffers the plaque. Would chewing sugar-free chewing gum reduce caries if it were used after meals in a controlled study? That question was addressed in an article that was published in the Journal of Dental Research (2001;80:1725–1729). In this study, 583 volunteers from the third, fourth, and fifth grades in a public school in Budapest, Hungary, were enlisted to participate. The sample was divided into two subgroups. One group was asked to chew sorbitol-containing gum for 20 minutes after each meal for two years. The other group did not chew any gum. The number of decayed, missing, and filled teeth was evaluated before the experiment, after one year, and after two years. The results showed that the gum-chewing group exhibited 41.7% reduction in incremental caries compared with the control group after one year, and a 33.1% reduction after two years. This study conclusively demonstrates that chewing of sorbitol-containing gum for 20 minutes after meals has a significant affect on reducing dental caries in children and adolescents, by increasing the saliva flow, which buffers the plaque, and reduces the acidic effect of the plaque.

When maxillary or mandibular surgery is performed on patients, the vertical dimension of the face may be altered. Could this vertical alteration cause a concomitant change in maximum bite-force after surgery? This question was addressed in a study that was published in the Journal of Oral and Maxillofacial Surgery (2001;59:620–627). The sample for the study consisted of 104 adult patients who had received one of eight different types of orthognathic surgical procedures. In order to determine maximum bite-force, unilateral isometric bite-force measurements were made using a bite-force transducer. These measurements were made before surgery, and at six months, and one, two, and three years after surgery. The pre- and posttreatment cephalometric variables were correlated with the changes in bite force. The results showed that most of the variables showed no consistent correlations between their values before surgery and maximum bite forces after surgery. In spite of average increases in maximum bite force of more than 50% after surgery, none of the surgical changes in the selected variables were significantly correlated with the changes in maximum bite force. In conclusion, improvement in bite force after orthognathic surgery is not related to the surgically induced changes in skeletal morphology.

Children may traumatize their maxillary incisors occasionally resulting in avulsion of a maxillary central incisor. When the tooth is replanted, the long-term success depends on whether inflammatory root resorption can be minimized. A recent study published in Dental Traumatology (2001;17:254–259), suggests that the type of intracanal medicament plays a role in the success of re-implantation procedures. The sample for the study consisted of eight Macaca fascicularis monkeys who were about three to five years of age. In each animal, four maxillary incisors were gently extracted. After 15 minutes, the teeth were carefully reimplanted in their sockets in the original position. After 11 days, the root canals were opened and the pulps were removed. In one canal, calcium hydroxide paste was placed. In the other canal, a corticosteroid-antibiotic paste was placed. The teeth were evaluated histologically eight weeks after canal medication. The results showed that the periodontal healing and the amount of inflammatory resorption were reduced by both the calcium hydroxide and the corticosteroid pastes, compared to the control animals with no medicaments. The amount of replacement resorption was slightly less in the corticosteroid group. In addition, the corticosteroid was slightly more effective than the calcium hydroxide at promoting periodontal healing. In conclusion, it is important that medicaments be placed in the root canals of avulsed and reimplanted teeth to avoid inflammatory root resorption.