Latest Research Reports from the Dental Literature

Low-energy shock waves disrupt oral bacteria. Low-energy (extracorporeal) shock waves are characterized by alternating positive and negative pressures. These pressure waves travel through fluid and soft tissues, and their physical effects occur at interface surfaces. Extracorporeal shock-wave therapy (ESWT) has numerous applications in medicine and has been used to break up calcium deposits in the kidney (lithotripsy), as well as to disintegrate calcium deposits in the pancreas and gallbladder. To date, no studies have been performed to determine whether low-energy shock waves could have an effect on bacteria. However, this was the topic of a research project published in the Journal of Dental Research (2008;87: 928–931). The purpose of this study was to examine the effects of low-energy ESWT on specific Gram-positive and Gram-negative bacteria that are associated with dental plaque. This was a laboratory study. Several different oral bacteria found in dental plaque were cultured and were placed on the surfaces of surgical gloves to simulate the interaction between these bacteria and soft tissue surfaces. Low-energy shock waves were generated with a pressure waveform unit. Various numbers of pulses were tested and compared. Then the authors calculated whether the low-energy shock waves could effectively decrease the viable counts of bacteria. Results of this study show that low-energy shock waves are capable of disaggregating the Gram-positive and Gram-negative bacteria that are important in biofilm formation and of selectively killing two of the primary pathogens associated with oral and systemic infection. Future studies by these authors will focus on the application of this technology to complex biofilm formation on solid surfaces.

Prefabricated occlusal appliances are effective in the short term for treating myofascial pain. A common treatment for myofascial pain is to place a maxillary stabilizing splint that evenly contacts all maxillary and mandibular teeth. However, prefabricated splints (the Nociceptive Trigeminal Inhibition [NTI] Appliance and the Relax Appliance, Unident AT, Falkenberg, Sweden) also have been proposed to treat muscle pain. These prefabricated appliances cover the maxillary incisors and therefore provide no posterior occlusal contact. If worn for prolonged periods, these appliances produce negative effects on posterior occlusion. However, short-term wear should not produce any negative occlusal effects. Can these prefabricated appliances provide pain relief if used only on a short-term basis? This question was answered in a randomized prospective clinical trial published in the Journal of Orofacial Pain (2008;22:209–218). The sample for this study consisted of 65 patients who had experienced myofascial pain for 3 months to 40 years. Subjects were randomly assigned to one of two treatment groups. In group S, subjects were given a custom-made stabilization splint, which covered all maxillary teeth and contacted all mandibular teeth. Subjects in group R received a prefabricated Relax appliance, which covers the anterior maxilla from canine to canine and provides no posterior contact. These appliances were worn only at night. Comfort, patient acceptance, daily pain intensity, and function of the appliance were recorded after 6 and 10 weeks. Results of this study show that there was no statistically significant difference in response between these two appliances. The authors conclude that from a short-term perspective, a prefabricated occlusal appliance seems to be as effective as a stabilization appliance and could be recommended for nighttime use as a short-term treatment for adult patients with myofascial pain.

Altering the gag reflex using a palm pressure point. A common problem in dentistry involves performing dental procedures on patients who have a prominent gag reflex. Tactile stimulation within specific trigger zones, including the base of the tongue, the palate, the uvula, and the posterior pharyngeal wall, will elicit the gag reflex. In some patients, this problem can be severe. However, a study published in the Journal of the American Dental Association (2008;139: 1365–1372) evaluated the effect of applying pressure to the center of the palm of a patient's hand to alter the gag reflex. A hand pressure device was designed to apply 2 pounds of force to the center of the palm of the hand. A gag response sensor probe was developed to record the amount of pressure needed to elicit a gag response in various parts of the palate. Forty-one adults participated in this study. Subjects were divided into two groups—hypersensitive and control groups. Initially, one gag reflex was initiated on the right side and the left side of each subject's palate. The amount of pressure and the location of the gag trigger point were identified. Then, pressure was applied to the center of the palm of the hand, and the gag trigger point was stimulated again to determine whether there were any differences in perception of the gag reflex. It is interesting to note that the authors found that all subjects demonstrated a change in the location of the trigger of the gag reflex. For all subjects in both groups, the gag reflex moved posteriorly toward the pharyngeal wall after pressure was applied to the center of the palm of the hand. The authors conclude that changing the trigger point of the gag reflex via palm pressure in the hypersensitive group would decrease the likelihood that a gag reflex may be triggered during dental procedures.

Prevalence of treatment need for temporomandibular disorders in adults. As orthodontists, we encounter adults who have temporomandibular symptoms such as pain, joint noise, limited mouth opening, and so forth. However, not all of these symptoms require intervention or treatment. What percentage of the general nonpatient population would have temporomandibular symptoms that do require some sort of treatment? This information would be of value to anyone who provides health care. A meta-analysis published in the Journal of Orofacial Pain (2008;22:97– 107) evaluated the prevalence of treatment need for temporomandibular disorder (TMD) in adults. Researchers identified strict inclusion criteria for their systematic literature review. After conducting a thorough review of the existing literature, they identified more than 650 potential articles. However, a vast majority of these articles were excluded because they did not fulfill the inclusion criteria. The authors established a sample of 17 studies that met their strict criteria. On the basis of their analysis, the prevalence of treatment need for TMD in adults was estimated to be around 16%. Many more subjects than this may have had TMD symptoms, but they could have been mild symptoms that did not require treatment. In general, the prevalence of treatment need for younger subjects (19 to 45 years) was higher than for older subjects (46+ years). This information regarding prevalence is important for those who plan the curriculum for dental education or who allocate health care resources for the treatment of patients with these types of problems.

Risk factors for developing dry socket after tooth extraction. Dry socket refers to postoperative pain in and around an extraction site that increases in severity at any time between the first and the third day after a dental extraction, accompanied by partially or totally disintegrated blood clot within the alveolar socket. Dry socket is extremely rare after extraction of deciduous teeth, is more common in females, and is more prevalent in posterior and mandibular teeth than in maxillary teeth. The prevalence may vary and usually does not exceed 4%. But are there risk factors that will increase the incidence of dry socket? This question was explored in a study that was published in the Journal of Oral and Maxillofacial Surgery (2008;66: 2290–2295). The sample consisted of all patients who presented for dry socket at an oral surgery clinic in a teaching hospital over an 18-month period. The authors gathered biographical data and information on preoperative diagnoses, extracted teeth, oral hygiene status, and history relevant to the extractions. This search produced a sample of 65 patients (46 females and 19 males) with dry socket. The mean age was 33 years. The reason for extraction was acute apical periodontitis secondary to carious lesions, chronic apical periodontitis, or chronic pulpitis. After carefully analyzing the data, the authors concluded that posterior mandibular teeth with a previous infection extracted in a male patient with poor or fair oral hygiene substantially increased the risk of dry socket. With females, if the tooth was extracted on days 1 to 22 of the menstrual cycle, with or without good oral hygiene, dry socket was more prevalent. So, the authors recommend that control of preoperative infection, insistence on good oral hygiene, avoidance of trauma, and avoidance of surgery on days 1 to 22 of the menstrual cycle in nonmenopausal women may considerably diminish the incidence of dry socket.