Axial displacement of external and internal implant-abutment connection evaluated by linear mixed model analysis.

PURPOSE: To analyze the axial displacement of external and internal implant-abutment connection after cyclic loading. MATERIALS AND METHODS: Three groups of external abutments (Ext group), an internal tapered one-piece-type abutment (Int-1 group), and an internal tapered two-piece-type abutment (Int-2 group) were prepared. Cyclic loading was applied to implant-abutment assemblies at 150 N with a frequency of 3 Hz. The amount of axial displacement, the Periotest values (PTVs), and the removal torque values(RTVs) were measured. Both a repeated measures analysis of variance and pattern analysis based on the linear mixed model were used for statistical analysis. Scanning electron microscopy (SEM) was used to evaluate the surface of the implant-abutment connection. RESULTS: The mean axial displacements after 1,000,000 cycles were 0.6 µm in the Ext group, 3.7 µm in the Int-1 group, and 9.0 µm in the Int-2 group. Pattern analysis revealed a breakpoint at 171 cycles. The Ext group showed no declining pattern, and the Int-1 group showed no declining pattern after the breakpoint (171 cycles). However, the Int-2 group experienced continuous axial displacement. After cyclic loading, the PTV decreased in the Int-2 group, and the RTV decreased in all groups. SEM imaging revealed surface wear in all groups. CONCLUSION: Axial displacement and surface wear occurred in all groups. The PTVs remained stable, but the RTVs decreased after cyclic loading. Based on linear mixed model analysis, the Ext and Int-1 groups' axial displacements plateaued after little cyclic loading. The Int-2 group's rate of axial displacement slowed after 100,000 cycles.

Surface alterations of several dental materials by a novel ultrasonic scaler tip.

PURPOSE: To assess the effects of a recently developed ultrasonic scaler tip, composed mainly of copper, on the surfaces of several dental materials. MATERIALS AND METHODS: Representative samples of dental materials, including titanium, type II gold, cobalt-chromium alloy, zirconia, and porcelain, were prepared. Three ultrasonic scaler tips of conventional metal (CM), carbon composite (CC), and copper alloy (CA) were prepared. To simulate ultrasonic scaling in an oral environment, 30 g of force was applied using a double-pan balance, and the scaler tip was allowed to move horizontally 5 mm for three consecutive cycles of 20 seconds each. The power of the scaler tip was set to intermediate according to the manufacturer's advice. The surface morphology of each dental material was examined using scanning electron microscopy and confocal laser scanning microscopy. Statistical analysis was performed through one-way analysis of variance and post hoc Scheffé test. All values were considered significant when P < .05. RESULTS: Surface alterations of titanium, type II gold, and cobalt-chromium alloy by the CM tip were much greater than those caused by the CC and CA tips. No alterations were created on the zirconia surface by the CM, CC, or CA tips. On the porcelain surface, surface roughness (Ra) induced by the CM tip was 1.86 and 1.72 times higher than that produced by the CC and CA tips, respectively (P < .001). CONCLUSIONS: Within the limitations of this study, the surface alterations induced by CC and CA tips on the surfaces of dental materials were comparable. Therefore, this novel ultrasonic copper alloy scaler tip may possibly be used for the maintenance of implant prostheses.

Full mouth rehabilitation of partially and fully edentulous patient with crown lengthening procedure: a case report.

BACKGROUND: In order to restore severely attrited teeth properly, surgical intervention in the form of a crown-lengthening procedure may be required. And also, proper diagnosis and treatment sequencing is critical to obtain a successful results. Adequate diagnostic wax-up ensures good esthetics and healthy periodontal tissue. CASE DESCRIPTION: This clinical case report describes a diagnostically based protocol for restoration on mandibular anterior teeth with crown lengthening procedure and the treatment of partially edentulous mandible combined with an edentulous maxilla. In addition, the effort to prevent the combination syndrome was described. CLINICAL IMPLICATION: An interdisciplinary diagnosis and examination through visualization of the desired results ensure conservative and more predictable outcome.