Effect of manufacturing techniques on the marginal and internal fit of cobalt-chromium implant-supported multiunit frameworks.

STATEMENT OF PROBLEM: Subtractive and additive computer-aided design and computer-aided manufacturing (CAD-CAM) systems have been used in the fabrication of cobalt-chromium (Co-Cr) long-span restorations. However, the accuracy of fit of multiunit frameworks is unclear. PURPOSE: The purpose of this in vitro study was to compare the marginal and internal fit of implant-supported, cement-retained 3-unit, 4-unit, and 5-unit Co-Cr metal frameworks fabricated by the lost wax (LW), CAD-CAM milling, and selective laser melting (SLM) techniques. MATERIAL AND METHODS: A total of 90 Co-Cr metal frameworks were fabricated for 3-unit, 4-unit, or 5-unit implant-supported cement-retained restorations on stock abutments with 3 different manufacturing technique subgroups (LW, CAD-CAM milling, and SLM). The silicone replica technique was used to evaluate the marginal and internal discrepancy values. By using a light microscope at ×45 magnification and a digital measurement program, the thickness of the silicone layer was measured at 16 reference points on each abutment for a total of 3360 measurements. The effect of manufacturing techniques and number of units (groups) on discrepancy values was evaluated using a full factorial ANOVA model. Group and manufacturing technique effects were analyzed separately by 1-way ANOVA in case of significant interactions. Pairwise comparisons were evaluated using the Tukey post hoc test (α=.05). RESULTS: The mean marginal discrepancy of 3-unit frameworks showed no statistically significant differences in the LW (35 µm) and SLM (25 µm) techniques; however, the frameworks manufactured by CAD-CAM milling (68 µm) had the highest marginal discrepancy values (P<.001). The mean marginal discrepancy values were 40 µm (LW), 33 µm (CAD-CAM milling), and 25 µm (SLM) for 4-unit frameworks, and no significant differences were found among the manufacturing techniques. For 5-unit frameworks, CAD-CAM milling techniques had the widest mean marginal discrepancy values (85 µm), and copings manufactured by the LW technique had the lowest mean marginal discrepancy values (36 µm). For all manufacturing techniques, axial discrepancy values were not affected with respect to the unit number (P=.526). The highest internal discrepancy values were measured at the occlusal area in all groups. CONCLUSIONS: CAD-CAM milling had the poorest marginal fit values for 5-unit frameworks, whereas the LW technique demonstrated the best results. Unit number had no significant influence on the marginal and internal fit of the LW manufactured frameworks.

Comparison of 3 luting agents on retention of implant-supported crowns on 2 different abutments.

BACKGROUND: For fixed prostheses, retention is one of the most important factors for clinical success. It is unknown whether grooves that increase surface area of implant abutment while retaining the diameter and wall height provide greater uniaxial retention force. The purpose of this study was to determine the retention of 3 different cements on 2 implant abutments with different surface configurations. MATERIALS AND METHODS: Thirty samples on 2 different abutments (a total of 60 crowns) with different margin and axial walls configuration and surface area were used. Metal crowns were fabricated on the abutment and cemented with 3 different (zinc-phosphate [ZP], glass ionomer [GI], or eugenol-free zinc oxide [ZO]) cements. After cementation, implant-abutment-casting assemblies were thermal cycled 1000 times with 1-minute dwell-time between 5°C and 55°C then subjected to tensile test with universal testing machine until decementation occurred. The mean force required to dislodge castings from abutment was determined. RESULTS: The luting agents influenced retention of castings on implant abutments, whereas different surface configurations and total surface area of the abutments did not influence the uniaxial retention forces. Among the cements tested, ZP exhibited higher values of retention, followed by GI and eugenol-free ZO. CONCLUSIONS: The increase in surface area of abutment did not result in improved retention. The present results suggest using ZP rather than GI and eugenol-free ZO in implant-supported crowns to provide higher retention.

A 12-month evaluation of nitrite oxide metabolism around immediate and conventionally loaded dental implants.

BACKGROUND: During bone remodeling, alignment of bone is affected by loading direction. Considerable amount of data also suggest nitric oxide (NO) to be involved in bone metabolism. This study was conducted to evaluate the potential changes in NO metabolism in relation to the loading style of dental implants by analyzing the nitrite content of peri-implant sulcus fluid. METHODS: Dental implants were placed in 12 patients who had first molar loss bilaterally in the mandibular area. One site of the patient determined as immediately loaded and the other side were conventionally loaded. Clinical parameters were recorded and peri-implant sulcus fluid samples were obtained. Peri-implant sulcus fluid nitrite levels were spectrophoto-metrically determined. Clinical measurements and nitrite analysis were repeated at 1, 3, 6, 9, and 12 months. RESULTS: In both groups, there was a reduction between baseline and 12 months in all clinical parameters, except probing depth. Although, steady decrease was noticed in total nitrite levels during the whole experimental period in immediately loaded implants, more fluctuations were observed in conventionally loaded ones. CONCLUSIONS: The findings of this 12-month follow-up study support the association of NO in the bone metabolism around dental implants and further suggest the impact of different loading regimens on NO metabolism.

In-patient comparison of immediate and conventional loaded implants in mandibular molar sites within 12 months.

OBJECTIVES: The aim of this prospective clinical study was to evaluate the clinical outcomes of dental implants placed in the mandibular molar sites and immediately functionally restored compared with conventionally loaded controls in an in-patient study. MATERIAL AND METHODS: Twenty-four dental implants were placed in 12 patients who had first molar loss bilaterally in the mandibular area. One site of the patient was determined as immediately loaded (IL) and the other side was conventionally loaded (CL). Resonance frequency analyses for implant stability measurements, radiographic examinations for marginal bone levels and peri-implant evaluations were performed during the clinical follow-up appointments within 12 months. RESULTS: During the 12-month follow-up period, only one implant was lost in the IL group. The mean implant stability quotient values were 74.18+/-5.72 and 75.18+/-3.51 for Groups IL and CL at surgery, respectively, and the corresponding values were 75.36+/-5.88 and 75.64+/-4.84 at 1-year recall, respectively. The difference was not statistically significant between the two groups during the 12-month study period (P>0.05). When peri-implant parameters were evaluated, excellent peri-implant health was demonstrated during the 1-year observation period and all implants showed less than 1 mm of marginal bone resorption during the first year. CONCLUSIONS: In the present study, immediate functionally loading did not negatively affect implant stability, marginal bone levels and peri-implant health when compared with conventional loading of single-tooth implants.

The impact of prosthetic design on the stability, marginal bone loss, peri-implant sulcus fluid volume, and nitric oxide metabolism of conventionally loaded endosseous dental implants: a 12-month clinical study.

BACKGROUND: Further clarification of the early and late response of peri-implant tissues to surgical insertion and loading of dental implants and the potential associations among the various implant-related measures are likely to improve the evaluation/monitoring of implant sites. Thus, analyses were made of the volume and nitric oxide (NO) profile of peri-implant sulcus fluid (PISF), implant stability, and marginal bone level in relation to different prosthetic designs. METHODS: Seven totally edentulous subjects and 11 partially edentulous subjects were included. Resonance frequency analysis (RFA), marginal bone level measurements, PISF volume, and spectrophotometrically determined nitrite levels were analyzed comparatively at conventionally loaded (CL) implant sites and at implants with removable prostheses (RP; N = 14) and fixed prostheses (FP; N = 11) for a period of 12 months. RESULTS: At implant sites with RP, PISF volume decreased gradually and its lowest level occurred at the end of the experimental period. The PISF nitrite content increased until 6 months and was followed by a significant decrease at 12 months. Compared to baseline, RFA values exhibited a significant decrease at 1 and 3 months. Marginal bone level was significantly lower at all follow-up visits compared to baseline. More volumetric fluctuations of PISF was noted at implant sites with FP. The PISF nitrite content had decreased, compared to baseline, at 6, 9, and 12 months. A general stability was observed for RFA. The marginal bone loss observed at 6 months was followed by a gain at 12 months. An inverse relationship was noted between RFA values and marginal bone levels. CONCLUSION: The prosthetic design particularly seems to affect the NO metabolism around CL implants, whereas it does not seem to have any impact on the stability of dental implants.

Myeloperoxidase as a measure of polymorphonuclear leukocyte response in inflammatory status around immediately and delayed loaded dental implants: a randomized controlled clinical trial.

BACKGROUND: As well as gingival crevicular fluid (GCF), peri-implant sulcus fluid (PISF) may have a potential diagnostic value for the early identification of metabolic and destructive processes. PURPOSE: The aim of this study was to analyze the potential impact of inflammation and loading on PISF myeloperoxidase (MPO) levels, in comparison with GCF. MATERIALS AND METHODS: A total of 220 sites, dental implant (immediately [IL] or delayed loaded [DL]), and natural tooth, either healthy/noninflamed or gingivitis/inflamed, were classified. Clinical parameters were recorded, and GCF/PISF samples were obtained. GCF/PISF MPO levels were spectrophotometrically determined. RESULTS: Clinical parameters demonstrated increases with the presence of gingival/peri-implant inflammation. Total MPO levels were higher at inflamed tooth and implant sites compared to noninflamed/healthy sites (p < .05). Although they did not reach a significance level, inflamed IL sites had higher total MPO levels than inflamed DL sites (p = .401). Gingival index and total MPO levels exhibited significant correlations (p < .05). CONCLUSION: Using implants and natural teeth in the same study design, the findings of the present study support the close relationship between MPO production and inflammation, and may speculate a potential for loading of dental implants, contributing to the MPO content of PISF.

Biomechanical Behavior of Implants with a Sloped Marginal Configuration.

PURPOSE: To evaluate the biomechanical behavior of implants with different neck designs. MATERIALS AND METHODS: Finite element models of implants with two different neck designs (OsseoSpeed EV and OsseoSpeed Profile EV) were generated. Implants and abutments were subjected to buccally and lingually directed 30-degree oblique loads of 200 N. RESULTS: Under buccally angulated load, the Profile implant model showed lower minimum principal stress when compared to the standard implant model (-63.4 vs -91.9 MPa), whereas the von Mises stress value of the Profile implant model was higher (342 MPa). CONCLUSION: This preliminary study showed that Profile implants placed in alveolar ridges with buccolingual bone height discrepancy showed similar stress distribution and stress value outcomes when compared to standard implants.