The effect of conventional, half-digital, and full-digital fabrication techniques on the retention and apical gap of post and core restorations.

STATEMENT OF PROBLEM: Conventional cast metal posts and cores are fabricated using direct and indirect techniques, both of which need impression materials and considerable laboratory work. Digital techniques have the capacity to substitute for conventional methods in fabricating the posts and cores. However, the accuracy of restorations resulting from a digital workflow is unknown. PURPOSE: The purpose of this in vitro study was to compare the retention of posts and cores fabricated using full-digital, half-digital, and conventional techniques and to define the accuracy of each technique in terms of the apical gap. METHOD AND MATERIALS: Thirty newly extracted mandibular first and second premolar teeth were selected for this in vitro study. Impressions were made using direct acrylic resin patterns (conventional), indirect silicone impressions of the intracanal which scanned with a 3Shape laboratory scanner (half digital), and intracanal scan posts captured with an intraoral 3Shape scanner (full digital). Casting and milling were conducted for the conventional impression and digital scans. The obtained posts were cemented using zinc phosphate cement. A universal pullout test was used to measure retention at a crosshead speed of 0.5 mm/min. The apical gap of each post in the canals was defined with parallel digital radiography. The data were analyzed using the Kruskal-Wallis test (α=.05) and Mann-Whitney test at the adjusted α=.016. RESULTS: Significant differences were found among the conventional, full-digital, and half-digital techniques in terms of the apical gap (0.11, 0.29, and 0.66 mm; P<.001) and retention (171.6 ±1.9, 107.1 ±5.6 and 91.8 ±6.6 N; P<.001). The correlation between gap and retention in conventional (P=.43), full-digital (P=.09), and half-digital techniques (P=.06) was not statistically significantly different. CONCLUSIONS: The conventional technique was more accurate and resulted in higher retention than both the full- and half-digital techniques. However, the retention and gap of all the posts fell within clinical guidelines.

Fracture resistances of zirconia, cast Ni-Cr, and fiber-glass composite posts under all-ceramic crowns in endodontically treated premolars.

PURPOSE: The aim of the present study was to evaluate the fracture resistances of zirconia, cast nickel-chromium alloy (Ni-Cr), and fiber-composite post systems under all-ceramic crowns in endodontically treated mandibular first premolars. MATERIALS AND METHODS: A total of 36 extracted human mandibular premolars were selected, subjected to standard endodontic treatment, and divided into three groups (n=12) as follows: cast Ni-Cr post-and-core, one-piece custom-milled zirconia post-and-core, and prefabricated fiber-glass post with composite resin core. Each specimen had an all-ceramic crown with zirconia coping and was then loaded to failure using a universal testing machine at a cross-head speed of 0.5 mm/min, at an angle of 45 degrees to the long axis of the roots. Fracture resistance and modes of failure were analyzed. The significance of the results was assessed using analysis of variance (ANOVA) and Tukey honest significance difference (HSD) tests (α=.05). RESULTS: Fiber-glass posts with composite cores showed the highest fracture resistance values (915.70±323 N), and the zirconia post system showed the lowest resistance (435.34±220 N). The corresponding mean value for the Ni-Cr casting post and cores was reported as 780.59±270 N. The differences among the groups were statistically significant (P<.05) for the zirconia group, as tested by ANOVA and Tukey HSD tests. CONCLUSION: The fracture resistance of zirconia post-and-core systems was found to be significantly lower than those of fiberglass and cast Ni-Cr post systems. Moreover, catastrophic and non-restorable fractures were more prevalent in teeth restored by zirconia posts.

Outcomes of management of early temporomandibular joint disorders: How effective is nonsurgical therapy in the long-term?

AIM: The first step in the management of Temporomandibular Disorders (TMD) is usually noninvasive, especially if the disorder is in the early stages. Clinically, pain and clicking are early signs and symptoms of TMD. The management of TMD usually includes "splint therapy" and analgesics. In this study, we report our long-term outcomes in the treatment of patients suffering from early TMD. MATERIALS AND METHODS: We assessed the records of 138 patients who were referred for management of TMD. Selection was based on pain and/or clicking of the Temporomandibular Joint (TMJ), no pathologic lesions of the TMJ, no anterior disc displacement without reduction (closed lock), no Degenerative Joint Disease, no history of migraine, trauma, osteoarthritis, metabolic disease, or malocclusion (deep bite, cross bite, jaw deformity, etc). The patients were treated with an acrylic maxillary Interocclusal Splint (IOS) cuspid-rise type and were told to refrain from biting, yawning and chewing hard food. The outcome of the treatment, potential etiologic factors (Bruxism), signs and symptoms and patient demographics (such as age, sex, treatment duration, etc.) were assessed. The data were analyzed using the Chi-square test to correlate significance. RESULTS: One hundred thirty-eight patients (26 males and 112 females) with early signs and symptoms of TMD (pain and/or click of the TMJ) were treated from 2001 to 2010; 81% were females and 19% were males. All the 138 patients used the IOS at night only. The patients were followed-up for 1-9 years. Data analysis showed that 64% of the patients were completely relieved of signs and symptoms; 22% were moderately relieved (decreased severity of signs and symptoms) and 14% had no noticeable post-treatment changes in clicking or pain (P = 0.001). Patients with bruxism and those presenting with both pain and clicking showed a better response to IOS treatment (P = 0.046 and P = 0.001, respectively). The results also showed that age, sex, severity of symptoms and duration of the treatment did not influence treatment results in this group of patients with early TMD. CONCLUSION: In this population, TMD was significantly higher in females. Treatment of early TMD with IOS was effective and moderately effective in long-term in over 80% of the patients during the follow-up period of 1-9 years. Bruxism had a significant etiologic role in TMD; occlusal attrition of the dentition, pain of all the teeth, early morning pain of the masticatory muscles and the TMJ are signs and symptoms to suspect nocturnal bruxism. Use of an IOS is recommended to prevent potential damage to the dentition, periodontium and the TMJ in early TMD.