Effect of print orientation, storage conditions, and storage time on intaglio surface accuracy of implant surgical guides fabricated by using a stereolithography technology.

STATEMENT OF PROBLEM: The accuracy of printed implant surgical guides can be affected by different factors that negatively impact the planned implant position. How print orientation, storage time, and conditions influence manufacturing accuracy remains uncertain. PURPOSE: The purpose of this in vitro study was to evaluate the influence of print orientation, storage conditions, and storage time on the intaglio surface accuracy of implant surgical guides manufactured by using a stereolithography (SLA) printer. MATERIAL AND METHODS: A tooth-supported maxillary implant surgical guide design (control file) was used to fabricate the specimens (N=40, n=10). Four groups were created based on the print orientation used: 0 (Group 0), 45 (Group 45), 70 (Group 70), and 90 degrees (Group 90). The specimens were fabricated using an SLA printer (Form 3B+) and a biocompatible dental resin (Surgical Guide Resin V1) following the manufacturer's recommended protocol. Each group was divided into 2 subgroups based on the storage conditions: light (L subgroup) and dark (D subgroup) settings. Each specimen was digitized by using a desktop scanner (Medit T710) at days 0, 1, 7, and 14. The control file and each digitized specimen were superimposed by using the best-fit technique with a metrology program (Geomagic Control X). The root mean square (RMS) error was used to calculate the discrepancies between the control files and specimen files. Three-way ANOVA and pairwise comparison Tukey tests were used to analyze trueness. The Levene test was used to assess precision (α=.05). RESULTS: Significant trueness discrepancies were found among the groups tested (P<.001), but no significant differences were found among the subgroups (P=.100) and the storage times analyzed (P=.609). Additionally, the Tukey test showed significant RMS error mean value discrepancies between Group 0 and Group 45 (P<.001), Group 0 and Group 90 (P<.001), Group 45 and Group 70 (P<.001), and Group 70 and Group 90 (P<.001). The Levene test revealed significant SD discrepancies among the groups tested (P<.05). CONCLUSIONS: The trueness and precision of the intaglio surface of the implant surgical guides manufactured by using the printer and material tested were affected by the print orientation. However, storage conditions over a 14-day period did not impact the intaglio accuracy of the specimens.

Flexural strength of denture base acrylic resins processed by conventional and CAD-CAM methods.

STATEMENT OF PROBLEM: High flexural strength is one of the desirable properties for denture base resins, yet only few studies have evaluated the physical properties of newer denture bases such as computer-aided design and computer aided manufacturing (CAD-CAM) milled products. PURPOSE: The purpose of this in vitro study was to compare the flexural strength of 3 different types of denture base resins: compression molded, injection molded, and CAD-CAM milled. MATERIAL AND METHODS: Three groups (n=10) of acrylic denture base resins were tested: injection molded, compression molded, and CAD-CAM milled resin. ISO-compliant, rectangular specimens were fabricated (64×10×3.3 mm) (n=30). Specimens were stored in water for 1 week, and flexural strength was measured by using a 3-point bend test until failure. The Student t test was used to evaluate differences in the flexural strength and modulus of elasticity among specimen groups. The Bonferroni formula was used to set significance at α=.017 to account for multiple comparisons among the 3 groups. RESULTS: The flexural strength of the CAD-CAM milled group was significantly higher than that of the other 2 groups (P<.001), while the strength of the compression molded group was significantly greater than that of the injection molded group (P<.001). The flexural modulus of the CAD-CAM group was significantly higher than that of the other 2 groups (P<.001). CONCLUSIONS: CAD-CAM milled denture bases may be a useful alternative to conventionally processed denture bases in situations where increased resistance to flexural strength is needed.

The Association Between Occlusal Status and the Soft and Hard Tissue Conditions Around Single-Unit Dental Implants.

The occlusal status of single-unit dental implants were evaluated using traditional and computerized methods. The type of occlusal contact in maximum intercuspation and the presence of occlusal contacts on the implant during eccentric movements were recorded. A digital sensor was used for computerized analysis of occlusion. Forty-four patients with 74 implants were included. Twenty-nine implants (39%) presented with "heavy" occlusal contacts, 40 implants (54.1%) presented with "light" contacts, and 5 implants (6.8%) presented with "no contact." No statistically significant association was found between the occlusal status and any of the soft and hard tissue condition variables (P > .05).

Effect of cement type on the clinical performance and complications of zirconia and lithium disilicate tooth-supported crowns: A systematic review. Report of the Committee on Research in Fixed Prosthodontics of the American Academy of Fixed Prosthodontics.

STATEMENT OF PROBLEM: Zirconia and lithium disilicate have been commonly used as materials for tooth-supported complete-coverage restorations. Adhesive and conventional cements have been suggested for cementation of these restorations. However, evidence on the effect of cement type on the clinical outcomes of teeth restored with zirconia or lithium disilicate restorations is unclear. PURPOSE: The purpose of this systematic review was to evaluate the clinical outcomes of teeth restored with zirconia or lithium disilicate restorations when adhesive or conventional cements are used. MATERIAL AND METHODS: This systematic review adopted the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement and was registered at the international prospective register of systematic reviews (PROSPERO) (CRD42018096493). An electronic search was performed in 2 databases (MEDLINE-PubMed and Cochrane Central), and a manual search, from January 2008 through January 2018. The primary clinical question was framed according to the Problem/Patient/Population, Intervention/Indicator, Comparison, Outcome (PICO) approach. The following question was the primary clinical question: "For patients requiring a single tooth-supported complete-coverage ceramic restoration, does adhesive cementation, as compared with conventional cementation, improve the clinical performance and limit the complications of this restoration?" The search included articles published in peer-reviewed journals in English and was limited to randomized clinical trials and prospective and retrospective clinical studies. RESULTS: Seventeen clinical studies met the eligibility criteria and were included for qualitative analysis. Included studies had 1280 participants who received 2436 zirconia and lithium disilicate crowns. The survival rates for adhesively cemented zirconia crowns ranged from 83.3% to 100%, whereas those reported for conventionally cemented zirconia crowns ranged from 82.0% to 100%. Survival rates for adhesively cemented lithium disilicate crowns ranged from 83.5% to 100%, whereas the survival rate reported for conventionally cemented lithium disilicate crowns was 98.5%. Commonly reported clinical complications included fracture of the veneering ceramic, crown fracture, and loss of crown retention. The mean follow-up time ranged from 25.5 months to 121.2 months. The studies that were assessed for risk of bias showed poor quality of evidence. CONCLUSIONS: Based on the available evidence and within the limitations of this systematic review, zirconia and lithium disilicate tooth-supported crowns exhibited comparable survival rates and complication patterns after adhesive or conventional cementation.

Preclinical Evaluation of a Crown-Splinted Custom Root-Shaped Implant.

OBJECTIVE: To test whether a Maryland bridge-type splint provides adequate stability for a custom root-shaped implant to osseointegrate in a manner substantially equivalent to that of a threaded implant. METHODS: Six beagle dogs were subjected to intraoral impressions and cone beam scans that were used to fabricate custom root-shaped implants (RTIs) and crowns. Premolars in the mandible (P4) and in the maxilla (P3) were extracted, and 24 RTIs were immediately placed in extraction sockets. Splint extensions of the crowns were bonded to mesial and distal teeth. Twelve mandibular molars (M2) were extracted, and threaded implants (DXI), serving as controls, were placed immediately. Animals were placed on a soft diet after surgery. Weekly intraoral photographs and radiographs were taken, and animals were sacrificed at 4 months. Fluorescent labels were injected 35, 21, and 7 days before sacrifice. Clinical implant stability and vertical pullout forces were tested, and loss of vertical bone height was measured on radiographs. Histomorphometric measurements of percent bone-to-implant contact (BIC) and mineral apposition rates were made from undecalcified sections. RESULTS: Three RTI splints broke or debonded, and the implants were removed. No loss of DXI implants was noted. All remaining implants were clinically stable. Mean pullout forces were 366.7 ± 182.8 N for RTI (no pullout data for the threaded DXI). Mean vertical bone loss was 0.4 ± 0.6 mm mesially and 0.2 ± 0.7 mm distally for RTI and 0.8 ± 1.1 mm mesially and 0.8 ± 1.0 mm distally for DXI, with no significant differences between groups. BIC values were 70.8% ± 12.7% for mandibular RTI, 68.3% ± 11.6% for maxillary RTI, and 78.8% ± 5.5% for DXI. Mineral apposition rates within local osteons were 1.9 ± 0.5 µm for RTI and 1.7 ± 0.3 µm for DXI; at the implant surface, they were 2.5 ± 1.2 µm for RTI and 3.3 ± 1.8 µm for DXI, with no significant differences between groups. CONCLUSION: All RTIs with intact splints exhibited clinically successful integration, similar to that of control threaded implants. The RTI may be a viable option for single-tooth replacement.

The Role of Occlusion in the Dental Implant and Peri-implant Condition: A Review.

Dental implants have become a widely used dental treatment approach. It is important to identify factors that can be detrimental to dental implants and the peri-implant complex. There is controversy regarding whether occlusion plays a role in the implant and peri-implant condition. The present study aims to review the scientific literature regarding this topic. Animal and human studies, and previous reviews on the topic are included and presented. There is a wide heterogeneity among study designs. Several articles demonstrated that occlusion and occlusion overload could detrimentally affect the peri-implant condition, while other articles did not support these results. More studies are needed to help understand the mechanisms by which occlusion might play a role in the peri-implant condition.

Effect of longitudinal flutes on miniscrew implant stability and 3-dimensional bone formation.

INTRODUCTION: The purpose of this study was to evaluate the effects of longitudinal flutes on miniscrew implant (MSI) stability and bone healing. METHODS: Using 11 skeletally mature New Zealand white rabbits, we placed 31 longitudinally fluted and 31 nonfluted, 3-mm-long MSIs in standardized positions in their calvaria and immediately loaded them with 100 g using nickel-titanium coil springs. Insertion torque values were obtained for each MSI placed; removal torque values were obtained for 28 MSIs that had been in place for 6 weeks and 20 MSIs that had been in place for 2 weeks. The bone volume fractions at 6 to 24, 24 to 42, and 42 to 60 µm from the MSI surfaces were evaluated using microcomputed tomography with an isotropic resolution of 6 µm. RESULTS: The success rate was 97% for both the fluted and nonfluted MSIs. The difference in insertion torque between the fluted and nonfluted MSIs was not statistically significant (P = 0.930). After 2 weeks, there was no statistically significant (P = 0.702) difference in removal torque between the fluted and nonfluted MSIs. After 6 weeks, removal torque values were significantly (P = 0.008) higher for the fluted (3.42 ± 0.26 N.cm) than the nonfluted (2.49 ± 0.20 N.cm) MSIs. Bone volume fractions of the 6-to-24-, 24-to-42-, and 42-to-60-µm layers were significantly (P <0.05) greater for the nonfluted than the fluted MSIs. CONCLUSIONS: Loaded 3-mm-long MSIs with and without flutes have high success rates. Longitudinal flutes placed in 3-mm MSIs increased their removal torque by 37% and decreased the amount of bone immediately surrounding them.

Elastic Properties of Chimpanzee Craniofacial Cortical Bone.

Relatively few assessments of cranial biomechanics formally take into account variation in the material properties of cranial cortical bone. Our aim was to characterize the elastic properties of chimpanzee craniofacial cortical bone and compare these to the elastic properties of dentate human craniofacial cortical bone. From seven cranial regions, 27 cylindrical samples were harvested from each of five chimpanzee crania. Assuming orthotropy, axes of maximum stiffness in the plane of the cortical plate were derived using modified equations of Hooke's law in a Mathcad program. Consistent orientations among individuals were observed in the zygomatic arch and alveolus. The density of cortical bone showed significant regional variation (P < 0.001). The elastic moduli demonstrated significant differences between sites, and a distinct pattern where E3 > E2 > E1 . Shear moduli were significantly different among regions (P < 0.001). The pattern by which chimpanzee cranial cortical bone varies in elastic properties resembled that seen in humans, perhaps suggesting that the elastic properties of craniofacial bone in fossil hominins can be estimated with at least some degree of confidence. Anat Rec, 299:1718-1733, 2016. © 2016 Wiley Periodicals, Inc.

Fracture resistance of compromised endodontically treated teeth restored with bonded post and cores: An in vitro study.

STATEMENT OF PROBLEM: It is unclear which post and core system performs best when bonded to severely compromised endodontically treated teeth. PURPOSE: The purpose of this study was to investigate the fracture resistance and mode of failure of severely compromised teeth restored with 3 different adhesively bonded post and core systems. MATERIAL AND METHODS: Thirty extracted endodontically treated maxillary anterior teeth were randomly divided into 3 groups, CPC, gold cast post and core; TPC, titanium prefabricated post/composite resin core; and FPC, quartz fiber reinforced post/composite resin core. All posts were adhesively cemented. All cores resembled a central incisor preparation with no remaining tooth structure above the finish line. Cast gold crowns were fabricated and cemented adhesively. The specimens were aged with thermocycling and cyclic loading. Two specimens per group were randomly selected for micro-computed tomographic imaging before and after aging. Failure was induced with a universal testing machine. The mode of failure was characterized by the interface separation. Data were analyzed with 1-way ANOVA (α=.05) followed by post hoc tests (Bonferroni). RESULTS: A statistically significant difference was found among the 3 groups (P=.002). CPC was significantly different than TPC (P=.008) or FPC (P=.003). The primary mode of failure for CPC and TPC was root fracture, and for FPC post debonding. CONCLUSIONS: Severely compromised endodontically treated teeth restored with bonded gold cast post and cores showed significantly higher fracture resistance.

Reduction in dental hypersensitivity with nano-hydroxyapatite, potassium nitrate, sodium monoflurophosphate and antioxidants.

OBJECTIVE: This clinical study aimed to evaluate effectiveness of a commercially available toothpaste containing potassium nitrate, sodium monoflurophosphate, and nano-hydroxyapatite as well as antioxidants phloretin, ferulic acid and silymarin in reducing dental hypersensitivity in adults. METHODS: The clinical trial enrolled patients with a history of dentin hypersensitivity. A test toothpaste was introduced into the daily routine, which included initial instruction on usage. Patients completed a five-question visual analog scale (VAS) at the inception/baseline, after two days and after two weeks of using the toothpaste to determine their level of tooth sensitivity at baseline with the use of the toothpaste over time. RESULTS: Patients that had significant sensitivity at baseline had a range of 52% to 76 % improvement after 48 hours and a range of 70% to 84% improvement after two weeks. CONCLUSION: A toothpaste containing potassium nitrate, sodium monoflurophosphate, and nano-hydroxyapatite plus antioxidants phloretin, ferulic acid and silymarin applied daily significantly decreased tooth pain of dentin hypersensitivity within a two-day and two-week time period. CLINICAL SIGNIFICANCE: Based on the clinical study results, a daily application of a toothpaste containing potassium nitrate, sodium monofluorophosphate, and nano-hydroxyapatite plus antioxidants phloretin, ferulic acid and silymarin can significantly and quickly reduce tooth pain of dentin hypersensitivity.

Dentate transport discs can be used to reconstruct large segmental mandibular defects.

PURPOSE: This study tested the use of a dentate transport segment for the reconstruction of a large U-shaped defect in the anterior segment of the canine mandible using a novel curved reconstruction plate. The quality and quantity of bone regenerate formed by dentate versus edentulous transport segments were compared. MATERIALS AND METHODS: In 5 adult foxhound dogs, a defect of 70 to 75 mm was created in the canine mandible by excising the mandible anterior to the right and left fourth premolars. Reconstruction was performed by trifocal distraction osteogenesis using a bone transport reconstruction plate (BTRP-02), with 2 transport units being activated simultaneously, one on either side of the defect, 1 dentate and 1 edentulous. Bilateral distraction proceeded at a rate of 1 mm/day until the segments docked against each other in the midline. After 39 to 44 days of consolidation, the animals were euthanized. The quantity and quality of bone regeneration on the 2 sides were compared using micro-computed tomography. RESULTS: The defect reconstruction was successful. The amount and quality of bone formed by the transport segments were similar on the 2 sides. There were no major differences in the bone volume fraction and density of the regenerate bone formed by the 2 transport segments. The bone volume fraction and density of the regenerate bone were considerably lower than those of the host bone in the distal segments, likely owing to the short consolidation period. CONCLUSIONS: Bone transport remains a viable option in reconstructing anterior segmental defects in the mandible. The use of dentate or edentulous transport segments for reconstruction provides options for the surgeon in often highly compromised patients requiring these surgeries.

A pilot histologic comparison of bone-to-implant contact between phosphate-coated and control titanium implants in the canine model.

PURPOSE: This study tested the null hypothesis that phosphate-treated titanium implants would perform no differently on mineral apposition rates (MARs), new bone-to-implant contact (new BIC), and total bone-to-implant contact (total BIC) compared to standard titanium implants. MATERIALS AND METHODS: Forty 3.3×8.0-mm titanium implants, either phosphate-treated or untreated, were placed in the mandibles of five foxhounds following 6 weeks of postextraction healing. The untreated implants (control) had sandblasted, acid-etched (SLA) surfaces, while the treated implants were electrolytically phosphorylated at 50 volts (T50) or 100 volts (T100). Confocal and histologic analyses were performed on all the implants after 4 weeks of healing. RESULTS: The MARs could not be analyzed due to a lack of delineation between the three bone markers. New BIC results for control implants ranged from 6.0% to 56.0% with a mean of 23.92% and standard deviation (SD) of 13.29%; T50 implants ranged from 8.0% to 43.0% with a mean of 22.29% and SD of 10.26%; and T100 implants ranged from 0.0% to 47.0% with a mean of 17.43% and SD of 11.40%. Total BIC results for control implants ranged from 8.0% to 68.0% BIC with a mean of 41.4% and SD of 19.3%; T50 implants ranged from 21.0% to 65.0% with a mean of 43.7% and SD of 15.2%; and T100 implants ranged from 5.0% to 68.0% with a mean of 38.0% and SD of 19.5%. CONCLUSION: Within the limitations of this pilot study, no significant differences in new BIC or total BIC were found between the three implant groups (C, T50, and T100). Given the very large sample size required to show clinically significant differences, phosphated surfaces do not appear to provide additional advantages to SLA surfaces.

Comparison of the effects of phosphate-coated and sandblasted acid-etched titanium implants on osseointegration: a microcomputed tomographic examination in the canine model.

PURPOSE: This study tested the effects of phosphate treatment of titanium on bone volume fraction (BV/TV) at 30 to 60 Μm from the implant surface using microcomputed tomography to analyze the mineralized tissue. MATERIALS AND METHODS: Electrolytically phosphated (50/100 volts [T1/T2]) or nonphosphated 3.3- X 8-mm titanium implants (C) with sandblasted acid-etched surfaces were placed in 40 mandibular sites in five foxhounds 6 weeks after the extraction of the premolars. After 4 weeks, the animals were sacrificed, and BV/TV was analyzed using microcomputed tomography. RESULTS: The mean BV/TV (± standard deviation) of the control implants was 31.4% ± 15.3% (range, 10.9% to 55.3%). For the T1 implants, a mean BV/TV of 38.4% ± 10.7% (range, 21.6% to 57.3%) was seen, and for T2 implants, the mean BV/TV was 40.3% ± 15.1% (range, 16.5% to 61.1%). Mean BV/TV values for the groups were not significantly different. For all groups (C, T1, and T2), there were no significant differences in BV/TV at the most coronal slices. For all groups, there was a positive slope showing more bone apposition as the slices moved from coronal to apical. The T2 group showed significantly increased mineralized tissue moving from the coronal to the apical section of the implant, compared to the control and T1 implants. CONCLUSION: Access to better blood supply and bone cells from the marrow spaces in the apical regions may lead to a better trabecular bone response. Increased mineralized tissue apposition may allow for accelerated loading and more predictable implant placement in sites with poor quality bone or patients with compromised bone healing.

Vacuum-induced Suction Stimulates Increased Numbers of Blood Vessels in Healthy Dog Gingiva.

UNLABELLED:  This study was designed to determine if vacuum-induced suction increased the number of blood vessels in healthy dog gingiva as a prelude to future studies testing vacuum therapy for improving local blood supply and controlling periodontal disease. METHODS: The buccal gingiva of five dogs was treated with subatmospheric pressure for 5 days, with untreated tissues acting as controls. Biopsies were analyzed for vascular endothelial growth factors (VEGF) and blood vessels were counted. RESULTS: VEGF and vessel numbers were elevated in treatment groups compared to controls (P < 0.05). CONCLUSION: A single daily application of subatmospheric pressure might be beneficial for healing damaged or diseased gingival tissues. .