Application of interdental distraction osteogenesis to unilateral cleft lip and palate patients

Distraction osteogenesis is widely used for the treatment of craniofacial deformities. In patients with cleft lip and palate, distraction osteogenesis can be employed to repair the alveolar cleft. In this report, we describe the management of three cases of unilateral cleft lip and palate by interdental distraction osteogenesis. Interdental distraction osteogenesis of the maxillary bone was performed to reduce the width of the alveolar cleft in these patients in conjunction with orthodontic treatment. Tooth-tooth type distraction devices were fabricated and delivered at the same time as osteotomy. Distraction was continued until the midline of the dentition coincided with the facial midline, and until the width of the alveolar cleft was reduced to the width of lateral incisor or had closed. One month after distraction was complete, orthodontic treatment with an edgewise appliance was initiated, and neighboring teeth were moved into the newly created bone. A favorable treatment outcome was achieved in all three cases.     

A vacuum technique to increase anterior thickness of athletic mouthguards to achieve a full-balanced occlusion.

A full-balanced occlusion is essential for mouthguards. It has been reported that a balanced occlusion for upper and lower anterior teeth is essential for prevention of injuries occurring to the maxillary anterior teeth and alveolar bone caused by horizontal direct impact. The support of the mandibular teeth through the mouthguard is critical to prevent maxillary front tooth injury from a direct impact force. However, some vacuum mouthguard designs may not achieve a full-balanced occlusion. For example, when a player has a malocclusion, an elongated molar or premolar tooth, an open bite, a large over jet or a maxillary protrusion. An improved vacuum fabrication method is necessary to obtain full balanced occlusion in these cases as opposed to conventional vacuum type single-layer mouthguard technique.     

Calbindin D-28k distribution in odontoblasts underneath tertiary dentine in human carious teeth

OBJECTIVE: The aim of this study was to examine the calbindin D-28k immunoreactivity in carious teeth to know whether this protein may have a function in tertiary dentine formation. METHODS: Human extracted teeth with or without carious lesions were immersion-fixed with Zamboni fixative, demineralized in 4.13% EDTA solution (pH 7.4), frozen-sectioned, and processed for calbindin immunoreactivity and hematoxylin-eosin stain. The intensity of the immunostaining was evaluated by quantitative densitometry. RESULTS: In intact teeth, numerous odontoblasts were aligned underneath the secondary dentine and their cell bodies showed the immunoreactivity. In carious teeth, tertiary dentine had poor- or rich tubular patterns under the carious lesion. Underneath the tubule-poor tertiary dentine, distinct odontoblasts could not be seen at the central site. However, some cells with a flat appearance were located at this site and were immunonegative for calbindin D-28k. On the other hand, columnar odontoblasts were seen at the peripheral site, and their cell bodies and processes showed strong immunoreactivity. Underneath the tubule-rich tertiary dentine, columnar odontoblasts were abundantly distributed, and the strong immunoreactivity was observed in their cell bodies and processes. The immunoreactivity in odontoblasts underneath the tertiary dentine with poor or rich tubular pattern was more intense than that for the secondary dentine in intact teeth (P<0.05). On the other hand, the intensity of the immunoreactivity in odontoblasts was similar underneath the secondary dentine in intact and carious teeth. CONCLUSIONS: The present study demonstrated that calbidin D-28k was actively synthesised by odontoblasts under the carious lesion. These findings may suggest that this protein plays an important role in the tertiary dentine formation.     

Effect of two-step adhesive systems on inhibition of secondary caries around fluoride-releasing resin composite restorations in root dentine

OBJECTIVE: The purpose of this study was to investigate the effect of two-step adhesive systems on secondary caries inhibition around fluoride-releasing materials in vitro. METHODS: Two self-etching primer systems, Clearfil SE Bond (SE) and UniFil Bond (UB), and two one-bottle systems with a total-etch wet-bonding technique, Single Bond (SB) and One-Step (OS), were used prior to placement of resin composites either with (Reactmer) or without (Z100) fluoride release. Class V cavities prepared in extracted human premolars were restored with various combinations of materials: Reactmer/SE, Reactmer/UB, Reactmer/SB, Reactmer/OS, Z100/SE, Z100/UB, Z100/SB and Z100/OS. After storage for 14 days, the restored teeth were incubated in bacterial medium containing sucrose with Streptoccus mutans for 2 weeks. Water sorption and desorption of the adhesives and fluoride release from the resins either coated with adhesive or uncoated were also determined. RESULTS: The one-bottle groups showed higher water sorption and desorption than the self-etching primer groups. Although fluoride release from the Reactmer specimens was suppressed by the adhesive coating, the one-bottle groups allowed significantly higher fluoride release than the self-etching primer groups. On microradiographs, the radio-opaque layers adjacent to the Reactmer restorations were thick and clear, while the layers adjacent to the Z100 restorations were thin and unclear. For the Reactmer restorations, the radio-opaque layers associated with the one-bottle groups were significantly thicker than for the self-etching primer groups. CONCLUSIONS: These results indicated that the use of one-bottle wet-bonding systems for bonding of fluoride-releasing resin composites to dentine may contribute to inhibit secondary caries compared to self-etching primer systems.     

Bonding of self-etch and total-etch adhesives to carious dentin

Carious dentin is partially demineralized and contains mineral crystals in the tubules. This may permit the deeper etching of intertubular dentin but prevent resin tag formation during bonding. We hypothesize that resin adhesives will produce lower bond strengths to caries-infected and caries-affected dentin compared with normal dentin. We tested this by measuring the microtensile bond strength of a total-etch adhesive and an experimental self-etching adhesive (ABF) to caries-infected, caries-affected, and sound dentin and by correlating those results with ultrastructural observations. The bond strengths of both adhesives to sound dentin were significantly (p < 0.05) higher than those to caries-affected dentin, which, in turn were significantly (p < 0.05) higher than those to caries-infected dentin. For both adhesives, hybrid layers in caries-affected dentin were thicker but more porous than those in sound dentin. The lower bond strengths may be due to the lower tensile strength of caries-affected dentin. Clinically, this may not be a problem, since such lesions are normally surrounded by normal dentin or enamel.     

Mandibular-position sensation during sedation by administration of nitrous-oxide (N2O) gas

Our aim was to confirm the influence of N2O gas on mandibular-position sensation. The subjects in this study were eight healthy adults. Each subject was asked to hold the reference stick for five seconds between the central tooth in his or her upper and lower jaws. Then, the reference stick was replaced by the test sticks with different thickness, each of which the subjects were again asked to hold at the same position for five seconds. The subjects were instructed to determine, based on judgement of the interincisal distance, whether the thickness of each test stick was larger or smaller than the reference stick. A series of trials was administered to each subject using all eight sizes of test sticks. We compared the ability of the subjects to discriminate mandibular position both before and after the application of a vibrating stimulus to the masticatory muscles, and before and during the administration of N2O gas. Discrimination ability was significantly decreased after the application of the vibrating stimulus. However, during the administration of N2O gas, no significant difference in discrimination ability was observed between before and after the vibrating stimulus. The results of this study indicated that N2O gas had an inhibitory effect on gamma-motor neuron activity, which is presumed to be mediated to some extent through the higher central nervous system. This is the case because the gamma-motor neurons are generally activated by vibrating stimuli applied to the muscle causing decreased discrimination ability of mandibular position. Thus, we conclude that mandibular-position sensation was influenced by N2O gas during the administration of N2O gas.