Hardness and surface roughness of differently processed denture base acrylic resins after immersion in simulated gastric acid.

STATEMENT OF PROBLEM: The effect of gastric acid on the surface properties of denture base acrylic resin is unknown. PURPOSE: The purpose of this in vitro study was to evaluate changes in the surface roughness and hardness of denture base acrylic resins after immersion in simulated gastric acid. MATERIAL AND METHODS: Acrylic resin specimens (n=10) were prepared with 3 different processing techniques (compression-molded, injection-molded, and computer-aided design and computer-aided manufacturing [CAD-CAM] milled) and exposed to either gastric acid or artificial saliva (control). Surface roughness and hardness were measured at baseline (T0) and after 24-hour (T24) and 96-hour (T96) immersion in the solutions. The surface roughness and hardness data were analyzed by 3-way ANOVA and the Tukey HSD test (α=.05). RESULTS: At T24, the greatest change in surface hardness was observed for compression-molded specimens in gastric acid (P<.05). At T96, changes in hardness values were higher in compression-molded specimens than those in milled specimens (P<.05). Regarding surface roughness, at T24, compression-molded and injection-molded specimens showed higher values than milled specimens in gastric acid (P<.05). Concerning specimens in artificial saliva, compression-molded specimens showed significantly higher changes in roughness than those of the others (P<.05). At T96, injection-molded specimens had the greatest roughness values (P<.05). Among specimens immersed in artificial saliva, milled specimens showed lower roughness values than the injection-molded or compression-molded specimens (P<.05). CONCLUSIONS: Gastric acid exposure adversely affected the roughness and hardness of all the acrylic resins evaluated. CAD-CAM milled specimens showed better resistance to acid exposure after 24 and 96 hours in terms of roughness and hardness.

Effect of home and over the contour bleaching on stainability of CAD/CAM esthetic restorative materials.

OBJECTIVE: To determine the effect of home and over the counter bleaching on the stainability of CAD/CAM restorative materials, and to correlate the surface roughness with discoloration. MATERIAL AND METHODS: Specimens were fabricated from feldspathic ceramic, an hybrid ceramic, a resin nano-ceramic, and lithium disilicate-reinforced glass ceramic. After baseline surface roughness (Ra1) and color measurement, each material was randomly divided into three groups according to bleaching regimen as Opalescence PF and; Opalescence Go; control. Then, the second color and surface roughness (Ra2) measurements were made. Thereafter, all specimens were immersed in a coffee solution for 12 days and the third color measurement was made. Color and whiteness change (CIELAB- ΔEab , CIEDE2000-ΔE00 , whiteness index-ΔWID ) were calculated after bleaching (ΔE1;ΔE00 1;ΔWID 1) and immersion in the coffee solution (ΔE2;ΔE00 2;ΔWID 2). RESULTS: According to both CIELAB, CIEDE 2000 and WID formulas, the highest mean ΔE1, ΔE2, ΔWID 1, ΔWID 2 values were observed for LAVA Ultimate groups while the lowest values were measured for e.max CAD groups. The findings also showed that there was a positively significant relationship between Ra2, and ΔE2 and ΔWID 2. CONCLUSIONS: Type of restorative materials and bleaching agents had an impact on color change after bleaching and immersion in coffee. CLINICAL SIGNIFICANCE: Home and over-the-counter bleaching agents may cause an increase in susceptibility of restorative materials to staining.

Influence of type of cement on the color and translucency of monolithic zirconia.

STATEMENT OF PROBLEM: With the development of translucent zirconia, questions regarding the influence of cements on the final color of monolithic zirconia restorations have arisen. PURPOSE: The purpose of this in vitro study was to evaluate color changes in terms of the perceptibility and acceptability of monolithic zirconia-and-cement combinations with 2 monolithic zirconia thicknesses and 3 types of cement. The translucency parameters of these combinations were also compared. MATERIAL AND METHODS: Sixty monolithic zirconia ceramic disks were milled with 2 different thicknesses (0.6 mm and 1 mm). A conventional glass ionomer cement, a resin-modified glass ionomer cement, and a resin cement from the same manufacturer were applied to the ceramic surfaces of both thickness disks (n=10). Translucencies and color changes of the monolithic zirconia specimens after cement application were examined by using a spectrophotometer, and translucency parameters (TPs) and color changes (ΔEs) were calculated and statistically analyzed. RESULTS: Colors and TPs of the zirconia disks changed significantly after being cemented to 0.6- and 1-mm-thick disks (P<.05). The lowest ΔE values (3.53 for the 0.6-mm and 2.23 for the 1-mm thick disks) were observed for the zirconia-resin modified glass ionomer combination, whereas the highest ΔE values (5.64 for the 0.6-mm and 5.06 for the 1-mm thick disks) were observed for the zirconia-resin cement combination. The glass ionomer cement most strongly affected the TP values of both of the thicknesses. CONCLUSIONS: Cement types and zirconia thickness affected the colors and translucencies of the monolithic zirconia specimens.

Botulinum toxin for the treatment of bruxism.

AIMS: Botulinum toxin, the most potent biological toxin, has been shown to be effective for a variety of disorders in several medical conditions, when used both therapeutically and cosmetically. In recent years, there has been a rising trend in the use of this pharmacological agent to control bruxing activity, despite its reported adverse effects. The aim of this review was to provide a brief overview to clarify the underlying essential ideas for the use of botulinum toxin in bruxism based on available scientific papers. METHODOLOGY: An electronic literature search was performed to identify publications related to botulinum toxin and its use for bruxism in PubMed. Hand searching of relevant articles was also made to identify additional studies. RESULTS: Of the eleven identified studies, only two were randomized controlled trials, compared with the effectiveness of botulinum toxins on the reduction in the frequency of bruxism events and myofascial pain after injection. The authors of these studies concluded that botulinum toxin could be used as an effective treatment for reducing nocturnal bruxism and myofascial pain in patients with bruxism. CONCLUSION: Evidence-based research was limited on this topic. More randomized controlled studies are needed to confirm that botulinum toxin is safe and reliable for routine clinical use in bruxism.

Phantom bite: a case report and literature review.

OBJECTIVE: Phantom bite is a rare and challenging condition that dentists may encounter in their daily clinical practice. Patients with phantom bite typically present with many failed repeated occlusal treatments, such as full-mouth prosthetic reconstructions and orthodontic treatments, to overcome their distressing symptoms. METHOD AND RESULT: A 55-year-old female with no history of medical problems presented with bite discomfort. She complained of discomfort from a "bite" and pressure-like feeling in her right upper three maxillary posterior teeth. Examination revealed no temporomandibular disorder (TMD) abnormalities. A thorough evaluation of her oral structures revealed no dental, periodontal, or mucosal pathologies. CONCLUSION: Owing to the great potential of conditions for financial loss and litigation problems, dentists, particularly those who perform bite-changing procedures, should be aware of this condition. This case is presented to highlight many of the clinical characteristics of phantom bite.

Investigation of the Relationship between Increased Vertical Overlap with Minimum Horizontal Overlap and the Signs of Temporomandibular Disorders.

PURPOSE: The purpose of this study was to test the null hypothesis that there was no relationship between increased vertical overlap (vertical overlap ≥4 mm) with minimal horizontal overlap (horizontal overlap ≤2 mm) and the signs of temporomandibular disorders. MATERIALS AND METHODS: Thirty participants (20 women, aged 20 to 45 years) with increased vertical overlap and minimal horizontal overlap, and 30 participants (20 women, aged 20 to 45 years) with no contact between the anterior teeth (control group) were examined. Diagnoses, psychological status (depression and nonspesific physical symptoms), and chronic pain severity were judged according to the Research Diagnostic Criteria for Temporomandibular Disorders and then compared. For statistical analysis of quantitative data, along with the descriptive statistical methods (mean, standard deviation, frequency), Student's t-test was used to compare parameters that reflected a normal distribution. Comparison of qualitative data between groups was performed using Chi-square and Fisher's exact tests. The level of significance was set at p < 0.05. RESULTS: In this study, deviation upon maximum opening was found significantly more frequently in the increased vertical overlap group than in the control group (p < 0.05). Tenderness upon palpation of lateral pterygoid muscles was observed more often in the increased vertical overlap group compared with the control group (p < 0.05). Opening-closing joint sounds occurred significantly more often in the increased vertical overlap group than in the control group (p = 0.050). CONCLUSION: Within the limitations of this study, deviation upon maximum opening, tenderness of lateral pterygoid muscles (upon palpation), and opening-closing joint sounds occurred more often in the increased vertical overlap occlusions with minimum horizontal overlap compared to the control groups. These results indicated that clinicians should pay special attention to the tempormandibuar joint status of patients with significant vertical overlap anteriorly and position of the incisors when performing dental treatments that require reestablishment of incisor relationships.

Relationship between bruxism and smartphone overuse in young adults.

OBJECTIVE: To evaluate the possible relationship between bruxism and smartphone overuse and assess the potential role of anxiety and depression in this relationship. The null hypothesis was that there was no significant difference between sleep bruxism (SB) and/or awake bruxism (AB) and non-bruxers in the level of smartphone overuse, anxiety, and depression. METHODS: In total, 167 dental students were included in this study. They were evaluated using the American Academy of Sleep Medicine (AASM) criteria, Smartphone Addiction Scale (SAS), Beck Anxiety Inventory (BAI), and the Beck Depression Inventory (BDI). T-test and chi-square test were used to compare the means and percentages between groups. RESULTS: A higher percentage of sleep bruxers were high smartphone users (60.3%) compared to non-SBs (44.2%). The frequencies of high smartphone users among participants with high anxiety and depression were higher than those with low anxiety and depression. CONCLUSION: SB and high smartphone use were positively associated.

Periodontal mechanoreceptors and bruxism at low bite forces.

OBJECTIVE: In this study, we examined if 6-9 Hz jaw tremor, an indirect indicator of Periodontal Mechanoreceptor (PMR) activity, is different in bruxists compared to healthy participants during production of a low-level constant bite force. METHODS: Bite force and surface EMG from the masseter muscle were recorded simultaneously as participants (13 patients, 15 controls) held a force transducer between the upper and lower incisors very gently. RESULTS: Tremor in 6-9 Hz band for bruxists was greater on average compared to controls, but the difference was not significant, both for force recordings and EMG activity. CONCLUSIONS: The low effect sizes measured with the current protocol contrast highly with those of our previous study, where larger, dynamic bite forces were used, and where jaw tremor was markedly different in bruxists compared with controls. SIGNIFICANCE: We have now gained important insight into the conditions under which abnormal jaw tremor can be elicited in bruxism. From a scientific standpoint, this is critical for understanding the 'abnormality' of PMR feedback in bruxism. From a clinical perspective, our results represent progress towards the development of an optimal protocol in which jaw tremor can serve as a biological marker of bruxism.

Neuropathic pain after dental treatment.

The head and neck regions are the most common sites of the human body to be involved in chronic pain conditions. Neuropathic pain is a chronic pain condition, and refers to all pain initiated or caused by a primary lesion or dysfunction or transitory perturbation in the peripheral or central nervous system (CNS). Trigeminal neuralgia, atypical odontalgia (phantom tooth pain), burning mouth syndrome, traumatic neuropathies, postherpetic neuralgias and complex regional pain syndrome are neuropathic pain conditions in the orofacial region that can be encountered in pain and dental clinics. The majority of the time this problem is misdiagnosed by the dentist, which can lead to unnecessary treatments. These treatments may include endodontic treatment and extraction of the tooth or teeth in the region. In this review, only post-traumatic peripheral pain neuropathies seen after dental treatments will be discussed.