Yan-Fang Ren

Classification and prevalence of temporomandibular joint disk displacement in patients and symptom-free volunteers

The purposes of this study were to develop a classification system for disk displacement in the temporomandibular joint (TMJ) and to study the prevalence of the various types of TMJ disk displacement in patients and symptom-free volunteers. The study was based on bilateral MRIs of 243 patients and 57 symptom-free volunteers. Eight different types of disk displacements were identified in addition to the superior disk position and a tenth indeterminate category. Superior disk position was observed bilaterally in 18% of the patients and bilaterally in 70% of the symptom-free volunteers.

Platelet-rich Plasma: A Literature Review

Platelet-rich plasma (PRP) is an autologous concentration of platelets in concentrated plasma, which is extensively used to promote soft and hard tissue healing. The significance behind its use refers to the abundance of growth factors present in a well-prepared PRP concentrate. These growth factors enhance the rate and quality of wound healing by different mechanisms. The objective of this review article is to explain the biological aspect of hard and soft tissue healing by application of PRP in conjunctions with its molecular basis.

Condyle position in the temporomandibular joint: Comparison between asymptomatic volunteers with normal disk position and patients with disk displacement

Though the significance of condyle-fossa relationship in the temporomandibular joint has not yet been clarified and normal condyle position not yet defined, efforts have been made to guide the mandibular condyle into a centric position in the glenoid fossa with the aim of relieving the symptoms in patients with orofacial pain and temporomandibular joint internal derangement. The present study investigated the mandibular condyle position in 34 joints in asymptomatic volunteers with normal disk position as verified by arthrography and compared it with the mandibular condyle position in 85 joints in patients with different stages of internal derangement. The results showed that in the volunteers with normal joints including normal superior disk position, the condyles were almost randomly distributed in anterior, centric, and posterior positions in the glenoid fossa. Of the joints with anterior disk displacement approximately half of the number of joints with reducing disks and two thirds of the joints with nonreducing disks appeared to have posterior condyle position. Posterior condyle position cannot, however, be used to diagnose internal derangement because the condyle was found to be either in anterior or centric position in many joints with a displaced disk. The variety in condyle position in the healthy joints ought to be taken into consideration if treatment is chosen to normalize the mandibular condyle position by bringing it into a centric position in the glenoid fossa.

Effects of tooth whitening and orange juice on surface properties of dental enamel

OBJECTIVE To study the effects of 6% H2O2 activated with LED light on surface enamel as compared to orange juice challenges in vitro. METHODS A total of 40 human enamel discs were incubated in saliva overnight to allow pellicle formation and then divided into three groups: 15 for whitening treatments, 15 for orange juice immersions and 10 for normal saline controls. Baseline microhardness was measured with a microhardness Knoop indenter (50g, 10s) and surface topography was evaluated with a focus-variation 3D scanning microscopy. Enamel discs were treated with H2O2 or orange juice for 20 min each cycle for five cycles to simulate daily treatment with the products for 5 days. The discs were stored in saliva between treatment cycles. Microhardness and surface topography were evaluated again after treatments. Changes in microhardness and in surface area roughness (Sa), mean maximum peak-to-valley distance (Sz) and the developed surface area ratio (Sdr) were compared before and after treatments (t-test) and among groups (ANOVA). RESULTS Enamel surface hardness decreased by 84% after orange juice immersion but no statistically significant changes were observed in the whitening and control groups. Surface topography changed significantly only in the orange juice group as shown by increased Sa (1.2 microm vs. 2.0 microm), Sz (7.7 microm vs. 10.2 microm) and Sdr (2.8% vs. 6.0%). No such changes were observed in the whitening and control groups. CONCLUSION In comparison to orange juice challenges, the effects of 6% H2O2 on surface enamel are insignificant. Orange juice erosion markedly decreased hardness and increased roughness of enamel.

Tinnitus in Patients with Temporomandibular Joint Internal Derangement

Tinnitus has commonly been reported in patients with temporomandibular joint (TMJ) disorders. The aim of this study was to determine if there was any correlation between arthographically verified disk displacement of the TMJ and ear symptoms related to tinnitus. Fifty-three patients with unilateral tinnitus and disk displacement and 82 individuals with disk displacement, but no tinnitus, were analyzed. Disk displacement was found to be present in the ipsilateral joint in all 53 patients with unilateral tinnitus, while the contralateral joint was asymptomatic in 50 (94.3%) of them. Patients with tinnitus suffered more extensive and intense pain in the oro-facial area compared to patients without tinnitus. The results of this study revealed a significant correlation between internal derangement of the TMJ and tinnitus.

Steepness of the articular eminence in the temporomandibular joint: Tomographic comparison between asymptomatic volunteers with normal disk position and patients with disk displacement

OBJECTIVE A steep articular eminence has been proposed as one etiologic factor for the development of TMJ disk displacement. The purpose of this study was to determine the steepness of the articular eminence in asymptomatic volunteers with superior disk position and to compare it with the articular eminence in patients with internal derangement. STUDY DESIGN We investigated 34 asymptomatic volunteers and 71 patients. The steepness of the articular eminence was determined on sagittally corrected tomograms, and disk position was diagnosed by dual space arthrotomography. RESULTS The results showed that the articular eminence was on the average steeper in the asymptomatic volunteers in the lateral (64.9 degrees), central (64.4 degrees), and medial (65.4 degrees) sections of the joint than in the patients (56.1 degrees, 60.2 degrees, 58.9 degrees, respectively). When the comparison of the steepness of the eminence was based on the presence or absence of osseous changes in the form of remodeling or osteoarthrosis, no difference was found between the asymptomatic volunteers and the patients with disk displacement but without such changes. The largest difference in the steepness of the eminence was found between the persons with osseous changes and those without. CONCLUSION These findings contradict earlier studies that have indicated a steep articular eminence to be one etiologic factor for the development of disk displacement. The results of this study showed that the steepness of the articular eminence is decreased in the patients as a result of remodeling or degenerative changes of the bone that are a result of the internal derangement.

Effects of common beverage colorants on color stability of dental composite resins: The utility of a thermocycling stain challenge model in vitro

OBJECTIVES To study the color stability of dental composite resins using a thermocycling stain challenge model accounting for the complex effects of oral environment and tooth brushing. METHODS Composite resin discs were made from Filtek Supreme Ultra (FiltekSU), TPH3 and Renamel, and subjected to thermocycling challenges in warm coffee (55 °C/pH 5.2) and a cold tea and fruit juice mixtures (5 °C/pH 3.6) for a total of 1000 cycles with 30 seconds dwell time in each solution per cycle. Color was assessed in the CIELAB color space using a Crystaleye dental spectrophotometer before and after thermocycling, and after brushing vigorously for 3 min. The thermocycling stain challenge was repeated for a second 1000 cycles and the discs were brushed again. Color changes were compared among the 3 groups using Kruskal-Wallis test. RESULTS All 3 groups showed statistically significant color changes after stain challenge, with ΔE* as 5.74 for FiltekSU, 3.21 for TPH3 and 2.52 for Renamel. Color change was more significant in FiltekSU than in TPH3 and Renamel (p<0.05). After brushing, color recovered mostly to its original CIELAB values in TPH3 and Renamel but less so in FiltekSU. The second round of thermocycling stain challenge resulted in color changes in FiltekSU that largely could not be removed by vigorous brushing. CONCLUSIONS Color stability of FiltekSU is inferior to that of TPH3 and Renamel. The thermocycling stain challenge model can potentially differentiate surface staining that can be removed by brushing from true discoloration of the material that is refractory to oral hygiene procedures.

Platelet-rich plasma in sinus augmentation procedures: a systematic literature review: Part II.

Background:Although platelet-rich plasma (PRP) has been extensively studied for over a decade, there are no definitive reports, which prove the benefit of using PRP in sinus augmentation procedures. In addition, no systematic literature review has been done to report the benefit of treatment outcome in patients who received PRP in conjunction with bone/bone substitutes in maxillary sinus augmentation procedures. Therefore, it can be rightly stated that evidence for an adjunctive benefit of using PRP with bone grafts in sinus augmentation procedures is equivocal and inconclusive. Aim:The objective of this systematic literature review was to examine this literature in determining whether PRP with bone and bone substitutes leads to more rapid and effective bone regeneration clinically, radiographically, and histologically with sinus augmentation procedures and was there any clinical data parallel to animal experiments providing clinical evidence in sinus augmentation procedures? Methods:A systematic review of randomized clinical trials of at least 6 months duration was conducted comparing PRP and bone/bone substitutes (test group) to bone/bone substitutes (control group) alone. Electronic databases such as MEDLINE and CENTRAL (Cochrane central register of controlled clinical trials) were searched for relevant articles. The reference list of all included articles was searched along with unpublished clinical trials whose abstracts were available. Results:Although, there is a lack of human studies, which show benefit of using PRP in conjunction with bone grafting materials, it can be stated that use of PRP does lead to early regeneration and reduction in healing time of soft and hard tissues. However, no significant statistical or clinical benefit was reported from studies that would satisfy the inclusion criteria. This study answers the question very clearly that at this point of time, there is no human study that strongly supports the benefit of using PRP in sinus augmentation procedures. Conclusion:There is a paucity of clinically controlled trials regarding benefits of PRP in sinus augmentation procedures. Theoretically, it seems to have significant beneficial effects on the soft and hard tissue healing; however, the disparity in study design, surgical techniques, and different outcome assessment variables used, makes it difficult to assess the practical benefit of its clinical use. Although no obvious positive effects of PRP on healing of bone graft material in maxillary sinus augmentation procedures were noted, the handling of the particulate bone grafts was improved.

Assessing fluoride treatment and resistance of dental enamel to soft drink erosion in vitro: Applications of focus variation 3D scanning microscopy and stylus profilometry

OBJECTIVES This study assesses the application of the focus variation 3D microscopy for the evaluation of dental erosion and fluoride treatment for prevention of enamel erosion in vitro. METHODS Human dental enamel disks were treated with Prevident 5000 (PV, n=15) for 1 week and compared with a reference group (PN, n=15) after orange juice erosion in vitro. A focus variation 3D scanning microscope (IFM) and a stylus type profilometer (SSP) were used to evaluate the erosion depths on enamel. 3D topographic images were taken with vertical resolutions of 0.1 and 0.02 microm. Scratch marks depths from SSP were measured on IFM images. Measurements were compared between the SSP and IFM and between the two study groups. RESULTS The SSP and IFM measurements of eroded enamel surfaces showed similar trends between the two methods and between the two study groups. The SSP and the IFM measurements were statistically significantly different but correlated with each other. PV group showed consistently lower erosion depth than PN in all profile measures using both SSP and IFM. The stylus tip created scratch marks that were significantly different in depths between the eroded and the reference surfaces in both groups. CONCLUSIONS The focus variation 3D microscopy is a powerful tool in evaluating surface topography associated with enamel erosion and in assessing the treatment effects of anti-erosive therapies. Topical treatment with Prevident 5000 significantly increased enamel resistance to erosion by orange juice and should be considered as a treatment choice in patients susceptible to acidic dental erosion.

Patient satisfaction and masticatory efficiency of single implant-retained mandibular overdentures using the stud and magnetic attachments

OBJECTIVES To study patient satisfaction and masticatory efficiency of single implant-retained mandibular overdentures using the stud and magnetic attachments in a randomized clinical trial with a crossover design. METHODS Patients received a single implant placed in the midline of the mandible and either a stud (Locator) or a magnetic (Magfit) attachment, assigned at random. Patient satisfaction, including patient comfort, speech, chewing ability and retention, and masticatory efficiency measured by chewing peanuts, were assessed before and 3 months after attachment insertion. Patient satisfaction and masticatory efficiency were evaluated again 3 months after insertion of the alternate attachment bodies. The outcomes were compared before and after insertion of the attachments and between the two types of attachments using Wilcoxon signed rank tests. RESULTS Patient overall satisfaction, comfort, speech, chewing ability, and retention improved significantly after insertion of both types of attachment bodies (p<0.05). Masticatory efficiencies also increased in both the Locator and the Magfit groups (p<0.05). There were no statistically significant differences in patient overall satisfaction, comfort, speech, and retention between the two types of attachments (p>0.05). The Locator attachments performed better in perceived chewing ability than the Magfit (p<0.05), but there was no statistically significant difference in masticatory efficiency between the two attachment types (p>0.05). CONCLUSIONS Clinical outcomes were significantly improved in single implant-retained mandibular overdentures using either the Locator or the Magfit magnetic attachments. There was no difference in masticatory efficiency between the two attachment types.