Ex-vivo analysis of demineralisation on irradiated teeth using optical coherence tomography.

Head and neck cancer patients are prone to dental caries after radiotherapy. An ex-vivo study was conducted to assess the feasibility of optical coherence tomography (OCT) to detect tooth demineralization due to caries in irradiated teeth. Thirty-nine human molar teeth were subjected to caries lesion induction through irradiation (Group 1), pH cycling (Group 2-1), and both (Group 2-2). The OCT signal attenuation coefficient, µR was assessed and validated against microhardness test and scanning electron microscope (SEM). The µR for Group 1 increased from 10 Gy to 40 Gy, and subsequently decreased after irradiated to 50 Gy and 60 Gy due to damaged enamel microstructure. In Group 2-1, the µR decreased with duration of pH cycling from day 1 to day 14 due to the increase of porosity in enamel layer. However, the µR showed decreasing trend from day 14 to day 28 of pH cycling, resulted from mineral deposition in the enamel layer. Although no significant difference was found in the µR between Group 2-1 and 2-2, SEM of Group 2-2 demonstrated visually higher porosity and larger gaps between microstructures. Irradiation may accelerate caries damage to tooth microstructure by increasing its porosity and brittleness, but larger sample size may be needed to further prove the effect. OCT could potentially be used for early detection of tooth demineralization in vivo based on the measurable µR changes for all groups which are shown negatively correlated with microhardness value (p < 0.05).

Assessment of demineralized tooth lesions using optical coherence tomography and other state-of-the-art technologies: a review.

Tooth demineralization is one of the most common intraoral diseases, encompassing (1) caries caused by acid-producing bacteria and (2) erosion induced by acid of non-bacterial origin from intrinsic sources (e.g. stomach acid reflux) and extrinsic sources (e.g. carbonated drinks). Current clinical assessment based on visual-tactile examination and standardized scoring systems is insufficient for early detection. A combination of clinical examination and technology is therefore increasingly adapted. This paper reviews various procedures and technologies that have been invented to diagnose and assess the severity of tooth demineralization, with focus on optical coherence tomography (OCT). As a micron-resolution non-invasive 3D imaging modality, variants of OCT are now available, offering many advantages under different working principles for detailed analytical assessment of tooth demineralization. The roles, capabilities and impact of OCT against other state-of-the-art technologies in both clinical and research settings are described. (139 words).

Sorptivity of water in enamel for categorizing caries lesions.

OBJECTIVE: The aim of this research was to determine the association between sorptivity of water and the state of mineralization in carious enamel of different stages of severity. METHODS: As a preliminary work, water droplets of 1.5 µL were placed on the surfaces of hydroxyapatite (HA) discs of different densities. The water droplet profile was dynamically recorded every second over a period of 10 s using a contact angle meter to determine the relationship between sorptivity and density. To measure and calculate sorptivity on enamel surfaces, varnish was painted on the labial surface of 96 extracted caries-free human teeth, leaving two 1.4 ± 0.1 mm diameter circular exposed test sites. The specimens were randomly divided into 6 groups (n = 16) and subjected to 0(G0), 7(G7), 14(G14), 21(G21), 28(G28) and 35(G35) days of pH cycling, respectively. A 0.7 µL water droplet was placed on each exposed site and Optical Coherence Tomography was used to measure its height every 10 seconds for 2 min. Sorptivity was computed by considering sorption equations and Washburn's analysis of capillary kinetics and correction for evaporation was also performed. Micro-Computed Tomography scans of the specimens were obtained and delta Z (ΔZ) is the parameter used to measure mineral loss. ΔZ at 10 µm (ΔZ10) and 50 µm (ΔZ50) from the surface were calculated. One-way ANOVA and Post-hoc Tukey tests were used to compare sorptivity between groups and bivariate correlations were used to analyze the association between sorptivity and ΔZ. RESULTS: Sorptivity was found to be inversely and linearly correlated with HA density with R2 value of 0.95. With enamel, there is a general trend of increase in mean sorptivity from G0 to G35, except for a decrease in G21. The same trends were observed for both ΔZ10 and ΔZ50. The decrease in sorptivity in G21 coincided with the presence of a surface hypermineralized layer in G21 samples. Post-hoc Tukey showed significant differences in mean sorptivity between G0 and G14, G0 and G21 as well as G14 and G21. Post-hoc Dunnett's T3 showed significant differences for ΔZ10 between G0 and G14 as well as G14 and G21. Significant correlation between mean sorptivity and ΔZ10 was detected with Pearson correlation coefficient of 0.461. For ΔZ50, post-hoc Tukey showed significant differences between G0 and G14 but no significant difference was detected between G14 and G21. No correlations were detected between mean sorptivity and ΔZ50. SIGNIFICANCE: Sorptivity was found to be inversely and linearly correlated with HA density with R2 value of 0.95. With enamel, there is a general trend of increase in mean sorptivity from G0 to G35, except for a decrease in G21. The same trends were observed for both ΔZ10 and ΔZ50. The decrease in sorptivity in G21 coincided with the presence of a surface hypermineralized layer in G21 samples.

Preliminary study assessing remineralisation of early caries on posterior teeth using SoproLife®.

PURPOSE: The aim of this study was to assess the effectiveness of minimal intervention via fluoride therapy in management of early caries lesion with the aid of SoproLife®. MATERIALS AND METHODS: A total of 40 patients were recruited, (mean age = 23 years) and were assigned to low and moderate caries risk groups (n = 20). Eighty occlusal surfaces of posterior teeth were examined for early caries lesion visually and using SoproLife® at baseline and at a recall visit six months later. At baseline visit, patients were given oral hygiene education, fluoridated toothpaste for homecare and topical fluoride application. SoproLife® images acquired were analysed using Image J software version 1.50. Difference in the mean value of intensity of the red wavelength spectrum between baseline and recall visits, (ΔI), were analysed for both risk groups. ΔI for upper and lower first molar teeth were also analysed. RESULTS: Results show no statistical difference for ΔI between low and moderate risk groups (p = 0.13). There is no statistical difference in ΔI within the low caries risk group (p = 0.42) but there is significant difference in the moderate risk group (p = 0.02). No statistically significant difference in ΔI value between upper first molars (UFM) (p = 0.80) and lower first molars (LFM) (p = 0.07) were detected. There was also no statistically significant difference in ΔI value within the upper and lower first molars (UFM: p = 0.31, LFM: p = 0.27). CONCLUSION: SoproLife® generated images did not show significant differences in remineralisation of early caries between low and moderate caries risk patients and between the upper first and lower first permanent molars in these patients.

Dental age estimation employing CBCT scans enhanced with Mimics software: Comparison of two different approaches using pulp/tooth volumetric analysis.

The methods of dental age estimation and identification of unknown deceased individuals are evolving with the introduction of advanced innovative imaging technologies in forensic investigations. However, assessing small structures like root canal volumes can be challenging in spite of using highly advanced technology. The aim of the study was to investigate which amongst the two methods of volumetric analysis of maxillary central incisors displayed higher strength of correlation between chronological age and pulp/tooth volume ratio for Malaysian adults. Volumetric analysis of pulp cavity/tooth ratio was employed in Method 1 and pulp chamber/crown ratio (up to cemento-enamel junction) was analysed in Method 2. The images were acquired employing CBCT scans and enhanced by manipulating them with the Mimics software. These scans belonged to 56 males and 54 females and their ages ranged from 16 to 65 years. Pearson correlation and regression analysis indicated that both methods used for volumetric measurements had strong correlation between chronological age and pulp/tooth volume ratio. However, Method 2 gave higher coefficient of determination value (R2 = 0.78) when compared to Method 1 (R2 = 0.64). Moreover, manipulation in Method 2 was less time consuming and revealed higher inter-examiner reliability (0.982) as no manual intervention during 'multiple slice editing phase' of the software was required. In conclusion, this study showed that volumetric analysis of pulp cavity/tooth ratio is a valuable gender independent technique and the Method 2 regression equation should be recommended for dental age estimation.

Homeobox genes and tooth development: Understanding the biological pathways and applications in regenerative dental science.

OBJECTIVES: Homeobox genes are a group of conserved class of transcription factors that function as key regulators during the embryonic developmental processes. They act as master regulator for developmental genes, which involves coordinated actions of various auto and cross-regulatory mechanisms. In this review, we summarize the expression pattern of homeobox genes in relation to the tooth development and various signaling pathways or molecules contributing to the specific actions of these genes in the regulation of odontogenesis. MATERIALS AND METHODS: An electronic search was undertaken using combination of keywords e.g. Homeobox genes, tooth development, dental diseases, stem cells, induced pluripotent stem cells, gene control region was used as search terms in PubMed and Web of Science and relevant full text articles and abstract were retrieved that were written in English. A manual hand search in text books were also carried out. Articles related to homeobox genes in dentistry and tissue engineering and regenerative medicine of odontogenesis were selected. RESULTS: The possible perspective of stem cells technology in odontogenesis and subsequent analysis of gene correction pertaining to dental disorders through the possibility of induced pluripotent stem cells technology is also inferred. CONCLUSIONS: We demonstrate the promising role of tissue engineering and regenerative medicine on odontogenesis, which can generate a new ray of hope in the field of dental science.

Two-piece obturator using "lock-and-key" mechanism.

This paper describes a method used for the fabrication of a two-piece denture obturator for a patient who had surgical removal of the premaxilla due to squamous cell carcinoma. The patient had been wearing a two-piece obturator but encountered difficulty in inserting the prosthesis. In this case report, a lock-and-key mechanism was used to easily assemble the two-piece prosthesis intraorally. A keyhole was designed on the obturator to act as the lock while the denture was used as the key that fitted into the keyhole. This mechanism facilitated insertion and provided retention for the prosthesis. Heat-cured resilient acrylic material (Molloplast B®), which was used to fabricate the obturator, was a nonirritant, nontoxic, tissue-compatible material. It also did not contain plasticizers, therefore eliminating the problems associated with leaching out of plasticizers. The use of this flexible and resilient material allowed the obturator to engage in the undercuts without causing trauma and irritation to the soft tissues in the region of the defect. To conclude, the "lock-and-key" mechanism used in the fabrication of the two-piece denture obturator provided the patient with a lightweight, comfortable, and user-friendly form of prostheses.

Shear bond strength of orthodontic buccal tubes to porcelain.

BACKGROUND: Bonding of molar tubes is becoming more popular in orthodontics. Occasionally, these bonding are done on posterior porcelain crowns or bridges. The purpose of this study was to evaluate the shear bond strength of buccal tubes on feldspathic porcelain crowns with two different methods. MATERIALS AND METHODS: Forty porcelain right molar crowns were fabricated for this study. The crowns were randomly divided into two groups. In group 1, the crowns were etched with 9.6% hydrofluoric acid, silane coupling agent applied, coated with bonding primer and bonded with Transbond XT (3M Unitek, Monrovia, Calif). In group 2, the crowns were etched with phosphoric acid 37%, silane coupling agent applied, coated with bonding primer and bonded with Transbond XT. All the crowns were stored for 24 hours at 37°C and thermo-cycled before the shear bond test. The analysis of variance (ANOVA) was used to determine whether significant difference were present between the groups. RESULTS: The results of the analysis of variance (F = 0.23) indicated the shear bond strength of group 1 (3.57 ± 0.87 MPa) was not significantly different (P > 0.05) from group 2 (3.46 ± 0.65 Mpa). Fisher's exact test for the adhesive remnant index (ARI) revealed significant difference between both groups (P < 0.05). Eighty percent of group 1 buccal tubes failed at buccal tube/resin interface and eighty percent of group 2 mostly failed at porcelain/resin interface. CONCLUSION: Etching with phosphoric acid with the use of silane coupling agent would be safer and should make it easier for clinicians to clean the adhesive on the porcelain surface after debonding.

Shear bond strengths of buccal tubes.

AIMS: To investigate the shear bond strengths of buccal tubes and to determine the sites of failure. METHOD: Four orthodontic buccal tubes were selected: A, American Orthodontics; B, 3M Unitek - small base; C, 3M Unitek--large base; D, Hangzhou Dentop. Twenty buccal tubes from each group were bonded to the buccal surfaces of lower right first molars with the same light-cured composite resin. The buccal tubes were debonded with a universal testing machine and the data analysed. The amount of adhesive remaining on the teeth after debonding was classified with the modified adhesive remnant index (ARI). RESULTS: The groups ranked from the highest to lowest bond strength (MPa) were: B, A, D and C. The bond strengths of the buccal tubes, except Groups A and B, were significantly different (p < 0.05). The majority of the buccal tubes (63 per cent) had modified ARI scores of 1 and 2 and 25 per cent of the tubes had scores of 4 and 5. After debonding, no adhesive remained on 40 per cent of the teeth in Groups B and D. CONCLUSIONS: The shear bond strengths of the buccal tubes fell below the value considered to be clinically acceptable. There were no differences between the shear bond strengths of the buccal tubes with photoetched and microetched bases. The buccal tubes with the largest base failed prematurely, possibly because the unsupported bonding pad flexed during debonding.