New techniques for producing aesthetic, direct full-crown composite resin restorations for primary molars: a 24-month follow-up study of eight cases.

AIM: Although the demand for aesthetic restoration of primary molars has increased, techniques for producing aesthetic, direct full-crown restorations using light-cured composite resin for primary molars and the associated clinical outcome are not well established. The aim of this study was to describe the use of new techniques to produce aesthetic, direct full-crown restorations using light-cured composite resin for primary molars. The authors evaluate the clinical outcomes of the restoration method and investigate whether this technique could be used as an alternative to conventional methods. MATERIALS AND METHODS: Two new techniques, the resin block and the clear matrix, were studied by treating 8 teeth. The occlusal surface of stainless steel crowns was used for impression-taking to facilitate accurate reproduction of the anatomic structure, and the aesthetic restoration was obtained simply and consistently. RESULTS: At the 24-month follow-up evaluation, these new direct techniques were completely satisfactory. Marginal discoloration was observed in one tooth treated with the clear matrix technique, and a small partial wear was observed in another tooth treated with the resin block. CONCLUSION: The new techniques for restoration resulted in functional and aesthetic reproduction of occlusal morphology. Therefore, these techniques could be considered a practical alternative to conventional methods.

Noninvasive cross-sectional imaging of incomplete crown fractures (cracks) using swept-source optical coherence tomography.

AIM: To investigate the ability of swept-source optical coherence tomography (SS-OCT) to detect incomplete crown fractures (cracks) in extracted teeth. METHODOLOGY: Cracks were created by subjecting 30 porcine premolars to impaction by a steel rod plunging from the occlusal tip. SS-OCT images and stereomicroscopic photographs of the surface were acquired for each specimen before and after impaction. For evaluation, the focused light beam of SS-OCT was projected from three directions on the same plane: buccal or lingual, 45° to the mesial, and 45° to the distal. Histological sections were prepared after impaction, and length and width of cracks and lamellae were evaluated using the corresponding SS-OCT image. The values were analysed using Pearson's correlation coefficient. RESULTS: Through SS-OCT, cracks and lamellae were clearly detected as intensified scattering signals at the same position on the corresponding microphotographs and histological sections. Amongst the three scanning angles, the greatest lengths and widths were considered the corresponding values of SS-OCT and were used for analysis. Significant correlations regarding line length and width were observed between SS-OCT and histological sections (length: r = 0.65, P < 0.001; width: r = 0.60, P < 0.001). CONCLUSIONS: SS-OCT can clearly discriminate cracks, which appear as highlighted lines due to the scattering of light. The results obtained from the three scanning directions were correlated well with those of the histological sections.

Delivery of RANKL-Binding Peptide OP3-4 Promotes BMP-2-Induced Maxillary Bone Regeneration.

Although bone morphogenetic protein 2 (BMP-2) is known to stimulate osteogenesis, there is evidence that high doses of BMP-2 can lead to side effects, including inflammation and carcinogenesis. The supplementation of other bone-augmenting agents is considered helpful in preventing such side effects by reducing the amount of BMP-2 required to obtain a sufficient amount of bone. We recently showed that a receptor activator of nuclear factor κB ligand (RANKL)-binding peptide promotes osteoblast differentiation. In the present study, we aimed to investigate whether OP3-4, a RANKL-binding peptide, promotes BMP-2-induced bone formation in the murine maxilla using an injectable gelatin hydrogel (GH) carrier. A GH carrier containing OP3-4 with BMP-2 was subperiosteally injected into the murine maxillary right diastema between the incisor and the first molar. The mice were sacrificed 28 d after the injections. The local bone formation in the OP3-4-BMP-2-injected group was analyzed in comparison to the carrier-injected, BMP-2-injected, and control-peptide-BMP-2-injected groups. The GH carrier containing OP3-4 with BMP-2 enlarged the radio-opaque area and increased the bone mineral content and density in the radiological analyses in comparison to the other experimental groups. Interestingly, fluorescence-based histological analyses revealed that the mineralization had started from the outside, then proceeded inward, suggesting that the size of the newly formed bone had already been set before calcification started and that the effects of OP3-4 might be involved in accelerating the early steps of osteogenesis. Actually, OP3-4 enhanced the BMP-2-induced 5-bromo-2'-deoxyuridine (BrdU)-positive cell numbers at the injected site on day 7 and the expression of Runx2 and Col1a1, which are early osteogenic cell markers, on day 10 after the subperiosteal injections. In summary, we demonstrated, for the first time, that the application of OP3-4 by subperiosteal injection promoted BMP-2-induced bone formation, which could lead to the development of an easy and noninvasive means of promoting alveolar ridge formation.

[A case of injured unerupted permanent tooth in a child].

Children with trauma visit frequently the department of oral and maxillofacial surgery. The treatment for injured permanent teeth is different from that for injured deciduous teeth. We have experienced a case of a 9-year-old boy with an injured unerupted immature permanent tooth with tooth crown fracture. When the tooth erupted gradually, fractured pieces were removed three times, and indirect pulp capping was performed. Three years after the injury eruption was almost completed and pulp was alive, even though the dental roentgenograph showed obliteration of the crown pulp cavity.

[A newly developed method for taking pictures of tooth crown cracks for clinical records].

It is very important to examine fine cracks on the crown surface of traumatized tooth in the dental clinic because the presence of these cracks may cause discomfort or hypersensitivity of the tooth. By the emission of routinely used light, it is difficult to illuminate cracks, and the usual intraoral photography using strobe light emission is not useful to make records of cracks in most cases. In the present study, a method for taking pictures to record tooth crown cracks was newly developed using LED as a light source, and applied to patients with traumatized teeth in the dental clinic. The results were as follows: 1. Cracks on the tooth surface could be confirmed with the LEDs of all the colors used in this study. However, the blue LED enabled cracks in the incisal edge part to be more easily confirmed, and the white LED enabled cracks in the cervical part to be more easily confirmed. 2. Cracks of multiple modalities on the tooth surface was illuminated more often when the LED light was emitted at 45 degrees to the axis of the tooth than 90 degrees. 3. The light exposure field became wider by the use of the LED of diameter 5 mm than that of diameter 3 mm. However, the LED of diameter 3 mm was more favorable than that of diameter 5 mm for the observation of the cracks because the former could more easily change the direction of light emission.

Tissue reactions after experimental luxation injuries in immature rat teeth.

Immature permanent teeth often develop complications after luxation injuries. The pathology and the degenerative processes of the complications, however, are not well understood. In this study, we histologically examined the long-term reactions of immature rat teeth after standardized luxation injuries delivered in our previously developed experimental model. The upper first molars of 3-week-old male Wistar rats weighing 50-60 g were pushed horizontally toward the palate to cause a constant amount of dislocation. The follow-up changes of the luxated molars were studied up to 56 days after the trauma. Soon after the trauma, the periodontium had irregular fibers, degenerated cells, hemorrhage and edema in various places. After 12 h, a cell free area appeared in the palatal periodontium. In the alveolar bone and on the surface of the root, resorption occurred one day and 5-7 days after injury respectively. Although the damage in the periodontium and alveolar bone was gradually repaired, the root resorption, especially in the palatal cervical region, continued throughout the experimental period. In the most cases, the dental pulp did not seem to be damaged immediately after the trauma. By the 3rd day after injury, however, displacement of odontoblasts into the dentinal tubules was observed in many teeth. Moreover, formation of irregular dentin was observed in some teeth after 7 days. These changes of the pulp tended to disappear in the later stages of the experiment.

[A clinical study of traumatic injuries to deciduous teeth. (3). The influence on their permanent successors].

To study the influence of traumatic injuries to deciduous teeth on their permanent successors, we investigated 126 traumatized deciduous incisors of 66 children who had visited our clinic regularly after traumatic injuries, and whose permanent successors had erupted. The results are summarized as follows. 1) Some developmental disturbances on permanent successors, such as concerning their eruption, or crowns, roots and pulp, were found in 72 teeth. Among these, influences on crown formation and calcification were most often found, and white discoloration in the enamel was recorded in 55 teeth, yellow discoloration in 4 teeth and hypoplasia in 11 teeth. 2) One successor erupted one and a half years after the eruption of its opposite, and two teeth erupted in torsiversion. Three successors had root angulation, while arrest of root formation was found in one tooth. Pulp canal obliteration appeared in two teeth before their eruption. 3) Developmental disturbances of the crowns tended to be more severe and had a higher ratio when traumatic injuries occurred at a younger age. The range of the ages of the children at the time of injury was limited in cases of hypoplasia and yellow discoloration. 4) According to the diagnoses at the first visit, the severity of periodontal injury and the dislocational directions of deciduous incisors might relate to the disturbances of crown formation and calcification of successors. 5) According to the type of treatment, enamel hypoplasia was observed more frequently in the observation group and the extraction group. Yellow and relatively large white discolorations were found more frequently in the reposition group than in the fixation group. 6) In the endodontic therapy group, only relatively small white discolorations were found, but white discoloration was observed more frequently in the extraction after endodontic therapy group than in the extraction without endodontic therapy group after first visit. 7) White discoloration in the enamel was most often located in the both upper and lower teeth at the incisal third position on the labial surface.