Influence of Surface Conditioning on the Repair Strength of Bioactive Restorative Material.

OBJECTIVE: To evaluate the effects of surface treatment and repair material on the repair shear bond strength (SBS) of the bioactive restorative material. METHODS: A total of 240 Activa BioActive Restorative (Activa) discs were prepared, aged, and polished, and divided randomly into eight groups (n = 30). Groups 1-4 discs were repaired with bulk-fill flowable resin-based composite (Bulk-RBC), and Groups 5-8 discs with Activa. Surface treatment used for each repair material type were air abrasion with silica-coated 30-m Al2O3 particles (air abrasion) (Groups 2 & 6), Air abrasion with universal primer (Groups 3 & 7), and Air abrasion with universal adhesive (Groups 4 & 8). Groups 1 and 5 were controls without surface treatment. SBS test was performed, and the failure mode and surface topography were assessed. RESULTS: Surface treatment with air abrasion significantly improved the SBS for repair using both Activa and Bulk-RBC. Repair SBS using Activa was significantly higher compared with Bulk-RBC. Cohesive failure in substrate and mixed failures were most common in the surface-treated groups (2-4, 6-8). Air abrasion produced prominent surface topography changes compared with polishing. CONCLUSION: Air abrasion enhances the repair SBS of aged bioactive restorative material. The use of the same material (Activa) for repair affords a higher bond strength compared with the use bulk-RBC.

Brain activation patterns during unilateral premolar occlusion.

OBJECTIVE: To observe the characteristics of brain activation during unilateral premolar occlusion. METHODS: Functional magnetic resonance imaging was collected from 10 healthy volunteers during occlusion of the left first premolar (L1), left second premolar (L2), and right first premolar (R1). The brain activation patterns were analyzed, and the primary sensorimotor cortex, supplementary motor area, insula, thalamus, and prefrontal cortex were chosen as regions of interest. RESULTS: Single premolar occlusion activated the precentral gyrus, postcentral gyrus, cerebellum, thalamus, frontal lobe, hippocampus, cingulate gyrus, and parietal lobe. The brain areas showing activation during single premolar occlusion were similar to those activated by chewing. The activation pattern of L1 was more similar to that of L2 than R1. No significant left and right hemisphere differences in signal intensity were detected within the regions of interest. CONCLUSION: Brain activation patterns from two ipsilateral premolars were more similar than the pattern from a contralateral premolar.

Comprehensive gene expression analysis in human periodontal ligaments of the mandibular third molars performing vertical movement and the maxillary second premolars with occlusal contact.

OBJECTIVES: The periodontal ligament (PDL) is thought to be an important tissue in vertical movement during tooth eruption, but the precise molecular mechanism is not known. Thereto, comprehensive gene expression was analyzed in human PDL of mandibular third molars performing vertical movement and maxillary second premolars with occlusal contact. DESIGN: The expression profile of 9,243 genes in the PDL of one subject was compared between vertically moving third molars and second premolars with occlusal contact by DNA microarray. RESULTS: The expression of 27 genes showed more than a 10-fold difference between third molars and second premolars. The expression of CALB1 (encoding calbindin 1), CYP26A1 (encoding cytochrome P450, family 26, subfamily A, polypeptide 1), SPOCK3 (encoding testican-3), CCK (encoding cholecystokinin) and SCRG1 (encoding scrapie responsive protein 1) was more than 30-fold higher in PDLs of the third molars than the second premolars. CALB1 is reported to increase at the pressure side of PDL during experimental orthodontic tooth movement in rats. Interestingly, in this study, CALB1 expression showed the largest difference. In contrast, CRCT1 (encoding cysteine-rich C-terminal 1), SPRP3 (encoding small proline-rich protein 3), IL8 (encoding interleukin 8) and MMP12 (encoding matrix metalloproteinase 12) showed more than 100-fold higher expression in PDLs of the second premolars than the third molars. CONCLUSION: The present comprehensive gene expression in PDLs provides new insights into the molecular mechanism during the vertical tooth movement.

Casos clínicos tratados con el sistema Invisalign / Clinical cases treated with Invisalign® technique

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Increased blood flow and nerve firing in the cat canine tooth in response to stimulation of the second premolar pulp.

Mustard oil or mechanical stimulation was applied to maxillary second premolar tooth pulps and pulpal blood flow and or intradental nerve activity in the ipsilateral canine tooth were recorded in the cat. Mustard oil application to the second premolar pulp significantly increased blood flow in the canine tooth pulp to 162.0+/-65.8% (n = 16) of the prestimulation flow compared to control data obtained with application of mineral oil (107.0+/-5.1%, n = 6) (Mann-Whitney U-test, p = 0.0009). Sectioning of the infraorbital nerve and its branches on the experimental side (n = 4) did not affect this increase in pulpal blood flow. The paraperiosteal injection of 2% lidocaine (1.0 ml) without vasoconstrictor significantly inhibited the increase in canine pulpal blood flow induced by mustard oil application to the second premolar pulp (109.8+/-6.8% of the prestimulation level, n = 7) (Mann-Whitney U-test, p = 0.0013). Sporadic firing or sometimes bursts of action potentials in the canine pulp nerves were recorded during and/or after the mustard oil application to the second premolar pulp in three of 16 cases. Four single pulp nerve units firing in synchrony with the mechanical stimulation of the second premolar pulp were recorded in two of eight canines, which substantiated the existence of branched afferents innervating both teeth. These findings suggest that stimulation of the second premolar pulp may induce axon reflex-related vasodilation and intradental nerve firing in the canine pulp via branched afferent fibres innervating both the second premolar and canine teeth.

Effect of transcutaneous electrical nerve stimulation on pain perception threshold of human teeth: a double-blind, placebo-controlled study.

In this double-blind, placebo-controlled study, we studied the effect of three different transcutaneous electrical nerve stimulation (TENS) devices with extra- and intraoral electrodes on the pain perception thresholds of 234 unrestored, caries-free human teeth of 66 healthy individuals subjected to stimulation with an electric pulp tester. A placebo control collective of 64 healthy subjects received no electrical stimulation, since an inactive TENS device was used. In all tooth types tested (maxillary and mandibular incisors and premolars), the use of the active TENS devices resulted in an increase of 16.3-32.5% versus baseline in the pain perception threshold. The differences between active TENS and baseline were statistically significant for both TENS devices using extraoral electrodes (P < 0.05). No statistically significant differences were found between the different devices tested (P > 0.05). In the placebo collective, the increase in the pain perception threshold ranged between 6.4% and 10.3% versus baseline. There were no significant differences between placebo TENS and baseline on the one hand and between placebo TENS and the active TENS devices on the other hand (P > 0.05). The findings suggest that, as an alternative to local anesthetics, TENS seems not to be useful in the case of painful dental interventions, since it offered only minor advantages over a placebo.

Oral pressure receptors mediate a series of inhibitory and excitatory periods in the masseteric poststimulus EMG complex following tapping of a tooth in man.

Poststimulus EMG complexes (PSECs), consisting of a series of inhibitory and excitatory waves in full-wave rectified and averaged electromyogram (EMG), were elicited in the masseter muscles of 7 subjects following controlled tapping of a tooth, at a controlled clenching level. Applying local anaesthesia to this tooth decreased the total surface of the waves, on average by 89%. The excitatory and the inhibitory waves were similarly affected, indicating that mainly pressure receptors in the periodontium mediate the entire PSEC. In 4 subjects, who were exposed to acoustic noise to exclude a contribution of acoustic receptors, the recovery of the PSEC waves from local anaesthesia was tracked. In 3 subjects, one wave (the first inhibitory or the first excitatory one, respectively) recovered differently from the other waves, indicating that they are not necessarily mediated by one type of afferent axons. The evidence, nevertheless, suggests that the different PSEC waves in man reflect the projection of the periodontal afferents upon several brain structures, involved in the control of the activity of the masseteric motorneurones, as: inhibitory and excitatory control requires different groups of interneurones; and a mediation of the first inhibitory wave by slower conducting axons than the second inhibitory wave, or a mediation of both waves by axons of similar type, is not compatible with common interneurones.

Remineralization in human premolars of different posteruptive age.

In human premolars with posteruptive ages varying from 6 months to 4 years demineralized enamel was remineralized for 3 days at 37 degrees C in a recalcifying medium containing 2 mM Ca2+, 1.2 mM phosphate, 0.05 mMF- and 150 mM NaCl (pH = 7). The Ca, P and Ca/P molar ratio of the mineral gained were determined at various distances from the enamel surface. Whereas, particularly at 30 micrometers from the surface remineralization was higher and more extensive in young demineralized enamel, no difference could be found in Ca/P molar ratio, suggesting precipitation of an apatitic mineral in both young and old demineralized human enamel. The probable nature of the precipitate is that of a fluoridated hydroxyapatite.