Silver diamine fluoride and glass ionomer differentially remineralize early caries lesions,in situ

Objectives

The aim of the present study was to evaluate the percent mean mineral density (MD) change of early caries lesions after the application of silver diamine fluoride (SDF) or glass ionomer cement (GIC).

Materials and methods

This double-blind, crossover study involved two experimental phases of 28 days each. Thirty-two pairs of enamel slabs were created from the proximal surfaces of 16 premolars. Each pair of artificial carious slabs was randomly divided into the control or test group (38 % SDF or GIC). The slabs were attached to orthodontic brackets and bonded to the maxillary first permanent molars of 16 subjects for 28 days. After a 7-day washout period between phases, the subjects received the other material for the second phase. The mean MD of the lesions was measured by microcomputed tomography.

Results

SDF yielded a percent mean MD increase at a depth of 0–84 μm, although increase in the GIC group was observed at a depth of 24–108 μm. The percent mean MD changes of the SDF and GIC groups were similar (p?=?0.100) and significantly higher than in control (p?<?0.001, p?=?0.003, respectively).

Conclusions

The two materials increased the percent mean MD change of early proximal caries lesions to a similar extent, but with different spatial patterns.

Clinical relevance

Due to deeper level of GIC remineralization, the refractive index of the GIC applied enamel might be closer to sound enamel. Hence, GIC is recommended for remineralization of anterior teeth. SDF staining makes it unsuitable for use in anterior teeth; thus, it is reserved for use in posterior teeth.

     

A Novel Alveolar Distractor Incorporating Nickel–Titanium Alloy Springs: A Preliminary In Vitro Study

A new design of an alveolar distractor using nickel–titanium (NiTi) open-coil springs was developed and investigated to produce distraction forces against the tensile forces of porcine attached gingiva to simulate human gingiva. We subjected 15 mm long NiTi open-coil springs (Highland and ORMCO) with three levels of forces (light, medium and heavy) to mechanical testing in a 37 ± 1 °C water bath. Ten strips of porcine mandibular attached gingiva were subjected to tensile tests to determine the resistance force. The forces from the springs were compared with the tensile forces from the porcine attached gingiva. Data between groups were analyzed with independent-samples T-tests (p-value < 0.05). The tensile strength and the Young modulus were greater in buccal compared to lingual porcine attached gingiva. Compared to other spring dimensions and companies, forces generated from 0.014 × 0.036″ ORMCO springs were the highest and could overcome the tensile resistance from porcine attached gingiva over the longest distraction range of 1.6 mm. This preliminary in vitro study introduced a new design of an alveolar distractor incorporated with NiTi open-coil springs that could generate light and continuous forces to overcome the resistance from porcine attached gingiva.     

Reinforcement of Simulated Immature Permanent Teeth after Mineral Trioxide Aggregate Apexification

Objectives

The objectives of this study were to compare the fracture resistance of simulated human immature teeth that have undergone mineral trioxide aggregate (MTA) apexification and have been root-filled with fiber post, composite resin, MTA, or gutta-percha.

Growth-associated protein-43 immunohistochemical and ultrastructural changes in jaw muscle spindles of the rat following loss of occlusion

The effects of complete loss of occlusion on the structural and functional status of these muscle spindles were investigated by immunohistochemistry either for protein gene product 9.5 (PGP 9.5) or growth-associated protein-43 (GAP-43) by light and electron microscopy. All the upper molars of 4-week-old Wistar rats were extracted and the erupted portions of the upper and lower incisors of the same animals were cut-off at the level of the interdental papilla every other day. In a control group, immunoreactivity for GAP-43 was positive in the developing annulospiral endings of 2-week-old rats, but was not detected in any of the muscle spindles after 3 weeks of age. At 4 weeks of age, the PGP 9.5 immunostained spindles had well-differentiated annulospiral endings. Ultrastructurally, these afferent endings showed lenticular or circular profiles in cross-sections, and were differentially indented into the intrafusal-fibres. The inner surfaces of the terminals formed rather smooth myoneural junctions, while the outer surfaces were covered only by basal lamina continuous with that of the underlying intrafusal muscle fibres. After the experimental elimination of occlusal contact, GAP-43 immunoreactivity reappeared in some nerve endings of muscle spindles by 3 days, and persisted for at least 28 days. During this period, the afferent-terminals exhibited various fine structural abnormalities such as irregular outlines and invaginated neuromuscular interfaces. Some sensory-terminal (ST) profiles were completely engulfed by intrafusal-fibres. However, GAP-43 expression and ultrastructural alterations became undetectable within a week of the end of incisal cutting and the recovery of incisal-contact. These data indicate that remodelling of nerve terminals in muscle spindles, as assessed by GAP-43 expression and ultrastructural changes, occurs soon after a loss of occlusion, and ceases if incisal-contact is restored. It is concluded that possible changes in jaw muscle function, as well as a sudden loss of proprioceptive sensory input from the periodontal mechanoreceptors of molars and incisors, induce the structural reorganisation of nerve terminations in jaw muscle spindles that is associated with the appearance and disappearance of GAP-43 immunoreactivity.     

The Effects of Temperature and Time of Heat Treatment on Thermo-Mechanical Properties of Custom-Made NiTi Orthodontic Closed Coil Springs

Nickel-Titanium (NiTi) springs have been increasingly used in orthodontics; however, no optimum condition of heat treatment has been reported. Therefore, this research was conducted to determine the optimum heat-treatment temperature and duration for the fabrication of NiTi-closed coil springs by investigating their effects on thermo-mechanical properties. As-drawn straight NiTi wires of 0.2 mm diameter were used to fabricate closed coil springs of 0.9 mm lumen diameter. The springs were heat-treated at three different temperatures (400, 450, and 500 °C) with three different durations (20, 40, and 60 min). Electron Probe Micro-Analysis (EPMA) and Differential Scanning Calorimetry (DSC) were used to investigate element composition and thermo-mechanical properties, respectively. Custom-made NiTi closed coil springs composed of 49.41%-Ti and 50.57%-Ni by atomic weight, where their DSC curves of 500 °C presented the obvious endothermic and exothermic peaks, and the austenite finish temperature (A_f) were approximately 25 °C. With increasing temperature, deactivation curves presented decreased plateau slopes generating higher superelastic ratios (SE ratios). At 500 °C, closed coil springs showed superelastic tendency with lower stress hysteresis. The thermo-mechanical properties were significantly influenced by heat-treatment temperature rather than duration. The optimum parameter appeared to be 500 °C for 40 min to produce appropriate force delivery levels, relatively low plateau slope, and lower hysteresis for orthodontic use.     

Development and terminal differentiation of pulp and periodontal nerve elements in subcutaneous transplants of molar tooth germs and incisors of the rat

Ectopic tooth transplants are known to receive rich innervation of local neurons, but the precise location and structural features of neurites in the pulp and periodontal ligament (PDL) of such transplants are unclear. In this experiment, the molar tooth germs of rat embryos and incisors of young rats were subcutaneously transplanted into the dorsal regions of rats and processed, at various time intervals, for immunohistochemical demonstration of neural elements. Teeth with periodontal tissue elements developed in most of the molar transplants in 6 or 8 wk and received rich innervation, including some autonomic fibres, in the pulp. Nerve elements were also confirmed to be present in the PDL of these transplants, including specialized nerve ending-like structures reminiscent of the periodontal Ruffini endings. Mechanoreceptor-like structures were also induced in the regenerated PDL of similarly transplanted incisors, although the success rate was low. We conclude that rich and highly ordered innervation of the pulp, and occasional development of mechanoreceptors in the regenerated PDL of ectopic dental transplants, imply a high probability of successful induction of teeth with both nociceptive and mechanical sensations in the ectopic tooth and/or tooth germ transplant systems, although differentiation of mechanoreceptor-like nerve endings occured in only a few rare cases.     

Prevalence of ocular demodicosis among patients at Tertiary Care Center, Bangkok, Thailand

AIM: To determine the prevalence of ocular demodicosis by both microscopic examination and molecular detection among patients at King Chulalongkorn Memorial Hospital, Thai Red Cross Society, Bangkok. METHODS: One hundred individuals were enrolled in the study and were divided into five age groups. The meibomian gland dysfunction (MGD) score and qualities of cylindrical dandruff (CD) were also determined. Demodex mite infestations of eyelash samples were screened by both microscopic examination and semi-nested polymerase chain reaction (PCR). RESULTS: The prevalence of ocular demodicosis as determined by microscopic examination was 42% [Demodex folliculorum (D. folliculorum) 41% and Demodex brevis (D. brevis) 1%]. Among patients who had ocular Demodex infestation, 69% have CD and had an average MGD score of 4; in patients without demodicosis, 15.5% had CD and had an average MGD score of 4.12. Prevalence of ocular demodicosis as determined by semi-nested PCR was 79% (D. folliculorum 78% and D. brevis 1%). CONCLUSION: This is the first report on the prevalence of ocular demodicosis in Thailand. Patients with CD also had Demodex mites present. Semi-nested PCR is better than microscopy for Demodex infestation detection. An extensive survey with more representative samples is required to determine the prevalence in the country.