Clinical and immunological evaluation of peri-implant tissues around ultra-polished and conventionally-polished zirconia abutments. A 1-year follow-up randomized clinical trial.

PURPOSE: This is a randomized clinical trial to compare the clinical and immunological performance of ultrasmooth versus conventionally-smooth zirconia abutments placed subgingivally after a period of 1 year. MATERIALS AND METHODS: Sixty-two bone level platform-switched implants (NobelParallel CC) were placed epicrestally in the mandibular molar or premolar region in 62 patients. After osseointegration, implants were restored with auto polymerizing acrylic resin crowns and subsequently randomly allocated to two groups according to the type of screw-retained zirconia crown prescribed. The control group received custom zirconia restoration with the subgingival zirconia part conventionally polished, whereas the test group implants were restored with ultra-polished zirconia abutments. Periodontal parameters (PD, PI, and BOP) and marginal bone level changes (MBLC) were recorded for each implant 2 months after insertion (T0), 1 month after final delivery of the crown (T2), and at the 1-year follow-up (T3). Immunological mediators from gingival crevicular fluid (IL-1α, IL-1ra, and TNF-α) were inspected at 1 month after provisional (T1) and accordingly at T2 and T3. Data was analyzed statistically, and significance level was set to α = 0.05. RESULTS: After 1 year, there were no significant changes in PD control-2.18 ± 0.89 mm and test-2.5 ± 0.72 mm (p = 0.073). PD between T2 and T3 dropped significantly in the test group (p = 0.037) and remained stable in the control group. PI was not different in both groups at T0 (p = 0.518) and T2 (p = 0.817). At T3, the test group (0.9 ± 1.01) had a significantly lower PI than the control group (1.55 ± 1.23) (p = 0.035). There was no difference in BOP positive cases between groups after 1 year (control-61.3%, test-51.7%, and p = 0.455). The amount of IL-1ra decreased significantly in the test group (41.75 ± 57.58) (p = 0.001) but not in the control group (59.59 ± 70.43) (p = 0.177). MBLC for the control and test groups after 1 year were 0.68 ± 0.7 and 0.94 ± 0.65 mm (p = 0.061). CONCLUSIONS: PD dynamics, PI, BOP, and IL-1ra revealed better outcomes around ultra-polished zirconia abutments than around conventionally polished zirconia abutments.

Comparing effectiveness of rubber dam and gingival displacement cord with copy abutment in reducing residual cement in cement-retained implant crowns: A crossover RCT.

OBJECTIVE: To evaluate the amount of residual cement after cementation of implant crown abutments with rubber dam and retraction cord with copy abutments techniques. MATERIAL AND METHODS: Thirty single posterior metal-ceramic implant-supported restorations were delivered to 20 patients. The crowns were fabricated with occlusal openings obturated with composite, and then luted with resin-reinforced glass-ionomer cement on customised standard abutments. The cementation procedure was performed twice in the same specimens using rubber dam (group 1) and retraction cord with copy abutment (group 2). If no cement remnants were seen on periapical radiographs after cleaning, the crown-abutment unit was dismounted. All quadrants of the specimens were photographed to calculate the percentage proportions of residual cement area. Mann-Whitney and Kruskal-Wallis tests were used for statistical analysis. RESULTS: In each group, 120 measurements were performed (30 implants, 4 surfaces each). The median percentage ratio with interquartile range (IQR) between the cement remnant area and total specimen area was 1.39% (IQR 0.77%-2.29%) and 0.58% (IQR 0.31%-1.33%) in groups 1 and 2, respectively. Lesser cement remnants were found in group 2 with a statistically significant difference (p < .001). The comparison of the mesial, distal, buccal, and lingual surfaces in each group showed no statistically significant differences between them (group 1, p = .482; group 2, p = .330). CONCLUSIONS: The retraction cord and copy abutment reduced the excess cement more efficiently than the rubber dam did. Notwithstanding, undetected cement remnants were observed with both methods, and neither should be considered reliable in clinical applications.

Influence of titanium base, lithium disilicate restoration and vertical soft tissue thickness on bone stability around triangular-shaped implants: A prospective clinical trial.

OBJECTIVE: To evaluate how vertical mucosal tissue thickness affects crestal bone stability around triangular-shaped bone-level implants, restored with low profile titanium bases and monolithic lithium disilicate restorations. MATERIAL AND METHODS: Fifty-five bone-level implants of 4.3 mm diameter were evaluated in 55 patients (22 males and 34 females, mean age 48.3 ± 3.4 years) in prospective cohort study. According to vertical mucosal thickness, patients were assigned into three groups: 1 (thin, 2 mm or less), 2 (medium, 2.5 mm) and 3 (thick, 3 mm and more). Implants were placed in posterior mandible and maxilla in one-stage approach and, after integration, were restored with single screw-retained monolithic lithium disilicate crowns, using low gingival profile titanium bases. Radiographic examination was performed after implant placement and after 1-year follow-up. Crestal bone loss was registered mesially and distally, and mean value was calculated. One-way ANOVA and Tukey's HSD tests were applied; significance was set to 0.05. RESULTS: Mean vertical tissue thickness in 1 group was 1.76 ± 0.26 mm, 2 group-2.5 mm and 3.91 ± 0.59 mm in group 3, with statistically significant difference between all groups (p < 0.001). After 1-year follow-up, implants in group 1 (thin) had 1.25 ± 0.8 mm bone loss. Implants in group 2 (medium) had 0.98 ± 0.06, while implants in group 3 (thick) lost 0.43 ± 0.37 mm of crestal bone. Tukey's HSD test showed that differences between 1/3 and 2/3 were statistically significant (p < 0.001 and p = 0.0014, respectively), while between 1 and 2 was not significant (p = 0.310). CONCLUSIONS: Significantly less bone loss occurs around triangular-shaped bone-level implants in thick mucosal tissues (≥3 mm), compared to medium or thin tissue biotype. Crestal bone loss did not differ between medium and thin tissues.

Comparison of Different Cleaning Procedures for Decontaminating Zirconium Oxide Surface After Polishing.

PURPOSE: To evaluate the efficacy of cleaning protocols for the decontamination of organic compounds from polished zirconium oxide samples. MATERIALS AND METHODS: A total of 24 rectangular plate specimens were sintered from zirconium oxide. All samples were polished with commercially available polishers (coarse, fine, and superfine) and polishing paste. During the first step of the protocol, all specimens were cleaned with steam. Samples were then randomly assigned to one of three groups (n = 8 each): A, B, or C. In group A, no additional cleaning was performed, while specimens in group B underwent ultrasonic cleaning in distilled water. Group C specimens were cleaned in an ultrasonic bath with a special detergent solution. After washing, samples were subjected to energy-dispersive x-ray spectroscopy (EDX) and scanning electron microscopy (SEM) examination. In order to detect organic materials, the level of carbon atoms was measured. RESULTS: EDX analysis revealed that samples in group A had the highest percent of carbon atoms (9.57 ± 3.67) on the surface compared to other cleaning protocols. Following the Group B cleaning protocol resulted in lower carbon levels (4.73 ± 3.56), but this difference was not significant compared to group A (P = .439). None of the specimens in group C had detectable carbon atoms (0), which implies that all wax molecules were removed (P < .05). CONCLUSION: Total decontamination of organic compounds from a polished zirconium surface can be expected only following the C cleaning protocol; therefore, it is advised to employ an ultrasonic bath with detergent solution for cleaning procedures of zirconium abutments before delivery. Int J Prosthodont 2023;36:588-594.

Effect of Ti-Base Abutment Gingival Height on Maintenance of Crestal Bone in Thick Biotype Patients: A Randomized Clinical Trial with 1-Year Follow-up.

PURPOSE: To determine the effect of 0.7- and 2.4-mm transmucosal abutment height titanium bases on the crestal bone stability and peri-implant soft tissue condition of bone-level implants with platform switching in patients with vertically thick soft tissues. MATERIALS AND METHODS: Sixty bone-level platform-switched implants were placed in the molar and premolar regions of both arches in 60 patients. All epicrestally inserted nonsubmerged implants had a 4.1-mm diameter and, after osteointegration, were randomly allocated into two groups: (1) the short group, with a titanium base of 0.7-mm transmucosal abutment height, and (2) the high group with a 2.4-mm height. Monolithic zirconia restorations were fabricated for all implants. Parallel intraoral radiographs were obtained after the delivery of restorations (T1) and after 1 year (T2). Crestal bone levels and peri-implant soft tissue conditions were calculated for each implant. The significance level was set at α = .05. RESULTS: After 1 year, 55 patients were evaluated, with a mean bone loss of 0.6 ± 0.51 mm (median: 0.71, range: 0 to 2.09 mm) in the short group (23 patients) and 0.45 ± 0.59 mm (median: 0.65, range: 0 to 2.12 mm) in the high group (22 patients), showing no significant difference between groups (P = .168). A significant increase in marginal bone height was noted between the T1 and T2 time points in the short and high (P = .029 and .001, respectively) groups. The peri-implant soft tissue health parameters did not show statistically significant differences. CONCLUSION: Crestal bone stability after 1 year of follow-up around epicrestally placed platform-switched implants is not influenced by transmucosal abutment height, if the vertical soft tissue thickness is ≥ 3 mm.

The influence of new immediate tissue level abutment on crestal bone stability of subcrestally placed implants: A 1-year randomized controlled clinical trial.

BACKGROUND: The relation between implant abutment disconnection (AD) and increased crestal bone loss is still debated. PURPOSE: To compare bone changes below implant-abutment junction of subcrestally placed implants between: (1) implant level restorations, that underwent four ADs and (2) implants with immediate tissue level abutment with no AD, 1 month (T2) and 1-year (T3) after final restoration delivery. MATERIALS AND METHODS: Sixty-four patients received 64 bone level implants with platform-switching and conical connection in edentulous sites of posterior mandible and maxilla. All implants were placed 1.5 mm subcrestally and distributed among: (1) control group, that received a regular healing abutment and (2) test group with immediate tissue level (ITL) abutment, which was torqued to implants during surgery, transforming bone level implant to tissue level type. After 2-3 months of healing and a 1-month temporization, final zirconia-based screw-retained crowns were delivered to both groups. Crestal bone levels were calculated after final crown delivery (T2); after 1-year follow-up (T3) and compared using Mann-Whitney U test (p ≤ .05). RESULTS: Early bone loss of the test and control groups was 0.14 ± 0.27 mm and 0.64 ± 0.64 mm, respectively; the 0.5 mm difference was statistically significant (p = .0001). Late bone loss was 0.06 ± 0.16 mm and 0.21 ± 0.56 mm for the test and control group, respectively; the 0.15 mm difference between the groups was no more statistically significant (p = .22). Both groups displayed bone gain, 0.08 and 0.43 mm, respectively, and the overall crestal bone loss was reduced. CONCLUSIONS: Immediate tissue level abutments can significantly reduce early bone loss when measured 1 month after final prosthesis delivery, however, after 1-year follow-up, difference between the groups was no more statistically significant.

The influence of submerged healing abutment or subcrestal implant placement on soft tissue thickness and crestal bone stability. A 2-year randomized clinical trial.

PURPOSE: Aims of the study were: (a) to register crestal bone loss around 1.5 mm subcrestally placed implants and epicrestally placed implants with soft tissue tenting technique, (b) to record bone remodeling in subcrestal group, and (c) to determine the increase of vertical soft tissues after tenting. MATERIALS AND METHODS: Thirty-two patients with vertically thin tissues of 2 mm or less received 40 submerged bone level platform-switched implants, divided into two groups-(a) 1.5 mm subcrestally placed implants and (b) epicrestally placed implants with soft tissue tenting over 2 mm healing abutments. At the second stage surgery, implants received 4 mm healing abutments, soft tissue thickness was measured in epicrestal group, and later implants were restored with zirconia-based screw-retained single restorations. Radiological images were taken at the second stage surgery, restoration delivery and after 2 years of follow-up. Bone loss was calculated as a distance between implant neck and first radiographically visible bone-to-implant contact. Bone remodeling was calculated as a distance between the bone crest and implant neck. Mann-Whitney U test was used for statistical analysis, significance set to 0.05. RESULTS: After 2 years of follow-up, Group 1 (subcrestal) had 0.18 ± 0.32 mm of bone loss, Group 2 (epicrestal with 2 mm healing abutment) had 0.51 ± 0.4 mm of bone loss, with statistically significant difference (P = .001). Bone remodeling in Group 1 (subcrestal) was 1.17 ± 0.51 mm. Vertical tissue thickness in epicrestal group before the intervention was 1.85 ± 0.26 and 3.65 ± 0.41 mm after the use of 2 mm healing abutment, with a statistical difference (P = .005). CONCLUSION: Subcrestal implant placement can significantly reduce crestal bone loss, compared to vertical soft tissue thickening by tenting of epicrestally placed implants, although soft tissue tenting can significantly increase soft tissue thickness.

The Effect of a Polishing Protocol on the Surface Roughness of Zirconium Oxide.

PURPOSE: To evaluate the surface roughness values of zirconium oxide samples that were gradually polished using a commercially available polishing system and polishing paste. MATERIALS AND METHODS: A total of 50 rectangular specimens of predetermined size (10 × 10 × 3 mm) were sintered from zirconium oxide. Samples were randomly assigned to one of five groups (n = 10 each): control, coarse (Co), fine (F), super fine (SF), or polishing paste (PP). In the control group, no polishing was done; in the Co group, a coarse polisher was used; and the specimens in the remaining three groups underwent additional processing with a fine rubber abrasive. For SF and PP samples, subsequent treatment with a super fine polisher was applied. Finally, for the PP group, a goat-hair brush with diamond polishing paste was used. An optical profilometer was used to evaluate roughness average (Ra) in micrometers (µm). ANOVA and Games-Howell post hoc tests were utilized to detect differences between groups. The significance level was set to α = .05. RESULTS: Surface roughness gradually decreased with further polishing throughout the groups: control Ra = 0.525 ± 0.099 µm; Co Ra = 0.252 ± 0.038 µm; F Ra = 0.196 ± 0.035 µm; SF Ra = 0.114 ± 0.031 µm; and PP Ra = 0.054 ± 0.020 µm. Statistically significant differences were detected among all groups (P < .05). CONCLUSION: A surface roughness of 0.054 µm can be achieved if a full zirconia polishing protocol is used. Zirconium oxide can be polished to various surface roughnesses using commercially available polishing products.