Effect of material type, torque value, and sterilization on linear displacements of a scan body: An in vitro study.

BACKGROUND: There is limited knowledge on the effect of scan body (SB) material type, torque value, and sterilization on linear displacements of implant SBs. PURPOSE: To evaluate the effect of material type, torque value, and sterilization on linear displacements of SBs during screw tightening by using digital image correlation (DIC) analysis. MATERIALS AND METHODS: One polyetheretherketone (PEEK, Zfx Intraoral Scan Body) and one titanium SB (Ti, MPS Zimmer Scanbody R1410) were tightened with 5 Ncm torque on two implants (Zimmer TSV ⌀4.7 mm) by using a digital torque limiting device. SBs' initial spatial positions relative to the implants were recorded by using 3D DIC technique. Measurements were repeated after initially increasing torque value to 10 Ncm and then to 15 Ncm, and these steps were repeated for a total of 10 PEEK and 10 Ti SBs on both implants (n = 20). All SBs were then sterilized 25 times by using an autoclave (STATIM 5000 S G4) according to manufacturer's recommendations and all measurements were repeated. Linear displacements on three axes were calculated for each SB with increasing torque values (from 5 to 10 Ncm and from 10 to 15 Ncm) before and after sterilization. SB displacements within each torque value-sterilization pair were compared by using Mann-Whitney U test, whereas Wilcoxon signed-rank test was used to compare SB displacements within each material-torque value pair between conditions and within each material-sterilization pair between torque values (α = 0.05). RESULTS: On x-axis, PEEK SBs had higher displacements than Ti SBs (p < 0.001), whereas sterilization (p ≤ 0.028) and 15 Ncm torque application (p ≤ 0.006) led to higher displacements of PEEK SBs. On y-axis, PEEK SBs had higher displacements than Ti SBs with 15 Ncm torque application (p ≤ 0.033). A total of 15 Ncm torque-applied PEEK SBs and 10 Ncm torque-applied Ti SBs had higher displacements after sterilization (p ≤ 0.028). Application of 15 Ncm torque led to higher displacements regardless of the material (p ≤ 0.002). On z-axis, PEEK SBs had higher displacements (p ≤ 0.015), except for 10 Ncm torque-applied sterilized SBs (p = 0.102). With 10 Ncm torque application, sterilization decreased the displacement values of PEEK SBs (p = 0.044). Greater displacements were observed with 10 Ncm torque-applied Ti SBs before sterilization and 15 Ncm torque-applied PEEK SBs after sterilization (p ≤ 0.033). CONCLUSIONS: Axial displacement of SBs was affected by material type, torque value, and sterilization. Ti SBs mostly had lower displacements than PEEK SBs. Application of 15 Ncm torque to tested PEEK SBs should be refrained from and a calibrated tightening tool may enable the application of 10 Ncm or lower torque values for lower displacements. Sterilization generally increased PEEK SB displacements.

In Silico Finite Element Analysis of Implant-Supported CAD-CAM Resin Composite Crowns.

PURPOSE: The aim of this study was to evaluate the mechanical behavior of an implant-supported crown made using computer-aided design and computer-aided manufacturing (CAD-CAM) resin composite (RC) blocks in the posterior region. MATERIAL AND METHODS: Four commercially available CAD-CAM RC blocks were used in this study: Cerasmart 300 (CS300; GC, Tokyo, Japan), Katana Avencia P Block (KAP; Kuraray Noritake Dental, Niigata, Japan); KZR HR3 Gamma Theta (HR3; Yamakin, Osaka, Japan), and Estelite P block (ESP; Tokuyama Dental, Tokyo, Japan). Katana Zirconia STML (ST; Kuraray Noritake Dental) was used as the control group. The elastic moduli of each material were determined by a three-point bending test. After the CAD models were designed, two different loading scenarios (oblique, vertical) were created. 3D finite element analysis was conducted with the prepared models. RESULTS: The elastic modulus of the material utilized for the implant restorations did not cause any change in the stresses transmitted to the implant or peripheral bone. An important difference was detected in the abutment-crown junction area. The minimum von Mises value at the abutment-crown interface was obtained in ST, which has the closest elastic modulus to the titanium abutment. CONCLUSIONS: The 3D finite element model designed in this study was used to demonstrate that implant-supported crowns fabricated with four different CAD-CAM RCs showed no critical stress concentrations in the bone or implant under all loading conditions. These results suggest that CAD-CAM RC blocks could be used as an alternative material for implant-supported restorations in the posterior region in terms of stress distribution.

Evaluation of strain values of critical anatomic regions for two different pterygomaxillary approaches in Le Fort I osteotomy: An experimental study

BACKGROUND: The purpose of this experimental study was to measure stresses both on the pterygoid plates and the skull base following two different pterygomaxillary approaches in Le Fort I osteotomy. MATERIAL AND METHODS: The prepared skull models were randomly divided into 2 groups of 7. In the first group (A), the pterygomaxillary area was left intact. In the second group (B), pterygomaxillary separation was performed with a fine bur. The stresses were measured by using strain gauges. These strain gauges were attached to 6 different anatomical sites. The skull models were mounted on a servo-hydraulic testing unit. Each model was then subjected to a continuous linear tension until a plastic deformation was seen. RESULTS: The statistical analyses showed that there were no significant differences (p > .05) between the 2 groups regarding the strain values. Moreover, no statistical differences (p >.05) were found between the two groups in terms of maximum applied forces. CONCLUSIONS: Considering the clinical conditions, the present study shows that when Le Fort I osteotomy performed without pterygomaxillary separation, there is no significant stress on the skull base during the downfracture. Moreover, it is considered that there is no need for an excessive force applied to perform downfracture in Le Fort osteotomies without pterygomaxillary separation

Stress distribution in reduced periodontal supporting tissues surrounding splinted teeth.

The aim of this study was to analyze the distribution of occlusal stresses for splinted and nonsplinted mandibular anterior incisors and to compare different splinting materials. A mandibular model was generated from a patient's computed tomography scan using three-dimensional (3D) software. The mandibular model presented with four periodontally compromised incisors and two canines with optimal bone support (two-thirds crown-root ratio). Three different splint materials (composite resin, metal-reinforced, and fiber-reinforced) were selected. Vertical and transverse loads were applied, and stress levels around the periodontal structures and splint materials were analyzed with 3D finite element analysis. The results showed that when bone levels around teeth decreased, the stress on the canine increased. Tested splinting materials were successful in stress distribution, and metal was better than the other splinting materials at distributing the stresses.

Macro design effects on stress distribution around implants: a photoelastic stress analysis.

OBJECTIVES: Biomechanics is one of the main factors for achieving long-term success of implant supported prostheses. Long-term failures mostly depend on biomechanical complications. It is important to distinguish the effects of macro design of the implants. MATERIALS AND METHODS: In this study, the photoelastic response of four different types of implants that were inserted with different angulations were comparatively analyzed. The implant types investigated were screw cylinder (ITI, Straumann AG, Basel, Switzerland), stepped cylinder (Frialit2, Friadent GmbH, Manheim, Germany), root form (Camlog Rootline, Alatatec, Wilshelm, Germany), and cylindrical implant, with micro-threads on the implant neck (Astra, AstraTech, Mölndal, Sweden). In the test models, one of the implants was inserted straight, while the other one was aligned mesially with 15° angles. The superstructures were prepared as single crowns. A 150N loading was applied to the restorations throughout the test. RESULTS: A comparison of the implant designs showed that there were no significant differences between the straight implants; however, between the inclined implants, the most favorable stress distribution was seen with the stepped cylinder implants. The least favorable stress concentration was observed around the root formed implants. Microthreads around the implant neck appeared to be effective in a homogenous stress distribution. Observations showed that misaligned implants caused less stress than straight implants, but the stress concentrations were not homogenous. CONCLUSION: As there were observable differences between the implant types, straight placed cylindrical implants showed better stress distribution characteristics, while inclined tapering implants had better stress distribution characteristics.

In vivo and in vitro assessment of an intraoral dental colorimeter.

PURPOSE: The purpose of this study was to assess the performance of an intraoral dental colorimeter. MATERIALS AND METHODS: In vivo repeatability of an intraoral colorimeter was assessed by performing color measurements of 30 individuals' right maxillary central incisor. Three consecutive measurements from each individual were made. In the in vitro part of the study, 25 metal-ceramic and 25 all-ceramic specimens were prepared. Five shades of metal-ceramic and all-ceramic specimens were selected for color determination. A widely recognized in vitro colorimeter was used as the control group for the in vitro performance assessment of the in vivo colorimeter. The color differentiation capability of two colorimeters was compared with the readings obtained from ceramic specimens. DeltaE values between shade groups of ceramic specimens were calculated and statistically analyzed with Student's t-test. The repeatability of the intraoral instrument was evaluated statistically with Intraclass correlation coefficient. RESULTS: The in vivo evaluation results showed that the overall repeatability coefficient values of L*, a*, and b* notations of the intraoral colorimeter were "excellent." The color differences (DeltaE) calculated between the colorimeters were significant only between shades A(1)-B(1) for metal-ceramic specimens (p= 0.002); however, from 5 of 10 shade couples of all-ceramic specimens, the color differences obtained from the readings of the in vivo colorimeter were significantly different from that of the in vitro colorimeter (p < 0.001). For all specimens, the differences between DeltaE values were within clinically acceptable limits (<3.5). CONCLUSIONS: Within the limitations of this study, the intraoral colorimeter exhibited successful in vivo repeatability; however, the color difference detection performance of the device varied depending on the translucency of the specimens.

The effect of different shades of specific luting agents and IPS empress ceramic thickness on overall color.

The color stability of both porcelain and luting materials is very important for the esthetics of laminate veneers and all-ceramic crowns. The purpose of this study was to determine the effect of different shades of resin-based luting cement and the thickness of IPS Empress ceramics on the final color of the restorations. Resin-based dual-polymerized composite cement in two different shades (RelyX ARC) and ceramic disks of different thicknesses were selected for the study. Forty specimens (ten each of four different thicknesses: 0.5 mm, 1 mm, 2 mm, and 3 mm) were used for the evaluation. Initial specimen color parameters were determined in a Commission Internationale de l'Eclairage L*a*b* color order system with a colorimeter. Two different shades of the cement were prepared as polymerized layers and applied to one face of the specimens in order. Color changes were calculated between baseline color measurements and measurements after cementation. Color difference data were analyzed statistically. All specimens showed a significant color shift (DE > 3.7) after cementation regardless of the cement shade. However, the differences in the cement shade did not significantly affect the final color of the ceramic specimens for any thickness, and color shifts were not perceivable between the different shades of cement. (Int J Periodontics Restorative Dent 2009;29:499-505.).

Restoration of endodontically compromised anterior teeth with fiber posts and zirconia all-ceramic system. Case study.

Deciding what material to use to restore endodontically treated teeth complicated by total or partial loss of coronal tooth structure is sometimes difficult for the clinician. It is important to use materials that minimize risk and best accommodate clinical conditions and patient desires. This report describes the restoration of endodontically compromised maxillary incisors with fiber posts and a zirconia all-ceramic system. The materials used for the treatment produced satisfactory esthetic and functional results.

The use of a computerized tomography-based software program with a flapless surgical technique in implant dentistry: a case report.

Successful implant treatment includes osseointegration, as well as prosthetically optimal positions of the implants for esthetics and function. The aim of this study is to evaluate a patient that was treated with an implant-supported fixed prosthesis with the help of computer-assisted three-dimensional planning. A 52-year-old edentulous man underwent computerized tomographic (CT) scanning, and the cross sections were reformatted. The cross sections were used to construct a surgical guide. Eight ITI Straumann dental implants were placed using a series of supramucosal surgical stents. Following a 5-month healing period, the stability of the implants was confirmed with the use of an Osstell device. Because satisfactory stability was observed, implant-supported fixed partial dentures, incorporating 12 units in all, were made. After 6 months, a second CT evaluation was carried out and the positions of the implants were compared with the treatment planning data. The CT-based software program and surgical stents contributed to the success of this case.

Interdisciplinary treatment of multiple maxillary anterior diastemas: case report.

This article describes an interdisciplinary (orthodontic and prosthodontic) approach for treating a 28-year-old woman who had multiple maxillary anterior diastemas, insufficient lip support, and inadequate anterior guidance. Although the patient also had diastemas among her mandibular anterior teeth, she declined orthodontic or restorative treatment for this arch. Initially, ceramic orthodontic brackets and polytetrafluoroethylene-coated arch wires were used. Orthodontic treatment involved leveling and aligning the maxillary dental arch, correcting the incisor angulations, and providing appropriate spaces for prosthetic restoration. After orthodontic treatment, IPS Empress 2 crowns were delivered to the six maxillary anterior teeth. This interdisciplinary approach produced a successful outcome and improved esthetics. The patient remained satisfied at the three-year follow-up examination.

Assessment of bone density differences between conventional and bone-condensing techniques using dual energy x-ray absorptiometry and radiography.

OBJECTIVES: We used dual energy x-ray absorptiometry (DEXA) and periapical radiography to assess bone density differences after conventional and bone-condensing dental implant techniques. STUDY DESIGN: Single-tooth dental implants were placed by both conventional and bone-condensing techniques in 14 patients with bilateral missing teeth. Dual energy x-ray absorptiometry was used to calculate bone mineral density (BMD) and bone mineral content (BMC) before and 6 and 12 months after implant placement. Furthermore, photodensitometry of periapical radiographs was also assessed. RESULTS: The success rate was 92.9% for the conventional technique and 71.5% for the bone-condensing technique. The BMD was observed to be significantly higher 6 and 12 months after implant placement. The BMC and photodensitometry were significantly increased 6 months after implant placement but showed no further after 12 months. CONCLUSIONS: There were no significant differences in BMD, BMC, and photodensitometry between the two implant placement techniques. However, success rate of the conventional technique was greater than the bone-condensing technique, which may be the result of trabecular fracture associated with the bone-condensing.