Accuracy of computer-assisted, template-guided implant placement compared with conventional implant placement by hand-An in vitro study.

OBJECTIVES: To compare free-hand to computer-assisted implant planning and placement (CAIPP) regarding planned to achieved implant position. MATERIAL AND METHODS: Forty-eight cast/bone models were mounted in mannequin heads. On each side, a tooth gap of different sizes was created. In the test group (T), study implants were placed using a CAD-CAM guide based on virtual planning. In the control (C), free-hand implant placement was performed. After CBCT scanning, the implant position was compared with the planned position. Descriptive statistics were applied, and ANOVA was used to identify differences between groups and gaps. (p < .05). RESULTS: In C, mean lateral deviations at the implant base amounted to 0.7 mm (max. 1.8) (large gap) and 0.49 mm (1.22) (small gap). In T, 0.18 mm (0.49) and 0.24 mm (0.52) were recorded. At the apex, 0.77 mm (2.04) (large gap) and 0.51 mm (1.24) (small gap) were measured in C, and 0.31 mm (0.83)/0.34 mm (0.93) in T. Mean vertical deviations in C measured 0.46 mm (1.26) (large gap) and 0.45 mm (1.7) (small gap). In T, 0.14 mm (0.44) and 0.28 mm (0.78) were recorded. Mean angular deviations of 1.7° (3.2°) were observed in C (large gap) and 1.36° (2.1°) (small gap). In T, mean values were 1.57° (3.3°) and 1.32° (3.4°). Lateral and vertical deviations were significantly different between groups (not gaps), angular between gaps (not groups). CONCLUSIONS: CAIPP protocols showed smaller deviations irrespective of the size of the tooth gap. In C, the gap size had an influence on the error in angulation only.

Implants sites with concomitant bone regeneration using a resorbable or non-resorbable membrane result in stable marginal bone levels and similar profilometric outcomes over 5 years.

OBJECTIVES: To assess clinical and radiographic outcomes as well as the profilometric contour alterations of peri-implant hard and soft tissues around single implants treated with simultaneous guided bone regeneration (GBR) at 5 years. MATERIALS AND METHODS: Twenty-seven patients presenting with a single tooth gap in the esthetic zone received a two-piece implant. GBR was randomly performed using a resorbable (RES) or a non-resorbable membrane (N-RES) combined with a bone substitute material. Follow-up examinations were performed at baseline (BL = crown insertion), 1 year (FU-1), 3 years (FU-3), and at 5 years (FU-5) including clinical and radiographic parameters as well as profilometric changes. Statistics were performed by means of parametric and nonparametric tests. RESULTS: At 5 years, 20 out of 27 patients (9 RES, 11 N-RES) were re-examined. Median values for probing depth changed insignificantly between BL and FU-5 in both groups. The median marginal bone levels were located 0.23 mm (0.06; 0.46; RES) and 0.17 mm (0.13;0.28; N-RES) below the implant shoulder at FU-5 (changes over time p < .05). The calculated median profilometric change between BL and FU-5 was -0.28 mm (-0.53;-0.20; RES; p = .016) and -0.24 mm (-0.43;0.08; N-RES; p = .102; intergroup p = .380). The horizontal bone thickness decreased significantly between re-entry and FU-5 for group RES at all measured levels (p < .05) measuring 0.87 mm (0.0; 2.05) at the implant shoulder, whereas the decrease for group N-RES was insignificant (p = .031) with 0 mm (0; 0.84) at the implant shoulder at 5 years. CONCLUSIONS: Implants sites with concomitant GBR using a resorbable or non-resorbable membrane revealed stable marginal bone levels and clinical outcomes. Profilometric changes were clinically negligible over 5 years. The observed change in hard tissue thickness was partially compensated by an increase in soft tissue thickness.

Hard tissue changes after guided bone regeneration of peri-implant defects comparing block versus particulate bone substitutes: 6-month results of a randomized controlled clinical trial.

OBJECTIVES: To test whether block bone substitute used for guided bone regeneration (GBR) of peri-implant defects leads to different thickness of the augmented hard tissue than particulate bone substitute. MATERIAL AND METHODS: In 24 patients, 24 two-piece dental implants were placed >4 months after tooth extraction. Following random allocation, 12 peri-implant bone dehiscences were grafted with an individually shaped block of deproteinized bovine-derived bone mineral (DBBM) and 12 bone dehiscences with particulate DBBM. All the sites were covered with a collagen membrane stabilized with resorbable pins. Immediately after wound closure and after 6 months, the horizontal thickness (HT) of the augmented hard tissue was measured at the level of implant shoulder using cone beam-computed tomography. RESULTS: After wound closure, the median HT measured 3.35 mm (mean: 3.38) in the block group and 2.85 mm (mean: 2.73) in the particulate group. At 6 months, the median HT decreased to 2.90 mm (mean: 2.71) in the block group and to 0.2 mm (mean: 0.52) in the particulate group. This difference was statistically significant (p < .001). CONCLUSIONS: Block bone substitute used for GBR of peri-implant defects was superior to particulate bone substitute regarding the dimension of the augmented hard tissue after 6 months of healing.

Randomized controlled clinical study assessing two membranes for guided bone regeneration of peri-implant bone defects: 3-year results.

OBJECTIVES: To assess two- and three-dimensional changes of the peri-implant tissues as well as clinical, biological, and radiological outcomes of implants having been treated with resorbable or nonresorbable membranes at 3 years. MATERIALS AND METHODS: Twenty-three patients were re-examined after having received a single-tooth implant in the esthetic zone in conjunction with guided bone regeneration (GBR) using either a resorbable (RES) or a titanium-reinforced nonresorbable membrane (N-RES) and demineralized bovine bone mineral. Volumetric and linear as well as clinical and radiographic measurements were performed at crown insertion (baseline), at 1 year (FU-1) and 3 years (FU-3). Statistics were performed by means of parametric and nonparametric tests. RESULTS: Minor, but ongoing buccal volume loss was observed in both groups during the 3-year follow-up. A slightly higher volume loss was observed in group RES (-0.22 mm) compared to N-RES (-0.14 mm) at 1 year (FU-1), but aligned at 3 years (FU-3) RES (-0.30 mm) N-RES (-0.32 mm). All changes over time were statistically significantly different within (p < .05), but not between the groups (p > .05). Stable median interproximal bone levels after 3 years (FU-3); 0.26 mm (0.04; 0.36) (RES) and 0.14 mm (0.08; 0.20) (N-RES) and healthy tissues (BOP, PD) were obtained with both membranes. CONCLUSIONS: Both treatment modalities resulted in minor, but ongoing contour changes of the peri-implant tissues. Stable interproximal bone levels and healthy tissues can be obtained with membranes up to 3 years.

Guided bone regeneration and abutment connection augment the buccal soft tissue contour: 3-year results of a prospective comparative clinical study.

AIM: To test whether implant placement with simultaneous guided bone regeneration (GBR) differs from implant placement without GBR regarding the change in marginal mucosal contour. MATERIALS AND METHODS: In 28 patients, single implants were placed >4 months after tooth extraction. Eighteen implants were completely surrounded by native bone, and no bone augmentation was performed. At 10 implant sites, bone defects and thin bone plates were grafted with deproteinized bovine-derived bone mineral and covered with collagen membrane. Impressions were taken prior to implant placement (baseline), at 3 months before abutment connection, at 6 months immediately after crown insertion, at 1 year, and at 3 years. Models were optically scanned and 3D images were superimposed for the evaluation of mucosal contour changes at the mid-buccal aspect. The nonparametric Mann-Whitney U-test was applied to detect differences. RESULTS: From baseline to 6 months, horizontal contour change at the level 1 and 2 mm apical to the mucosal margin measured 0.65 ± 0.74 mm and 0.55 ± 0.56 mm at sites without GBR, and 1.92 ± 0.87 mm and 1.76 ± 0.70 mm at sites with GBR (P < 0.05). In the period from baseline to 1 year, the corresponding values amounted to 0.81 ± 0.67 mm and 0.60 ± 0.55 mm in the group without GBR, and to 1.81 ± 0.86 mm and 1.37 ± 0.62 mm in the group with GBR (P < 0.05). From baseline to 6 months, mucosal margin moved 0.16 ± 0.49 mm in the coronal direction in the group without GBR and 0.82 ± 0.65 mm in the group with GBR (P < 0.05). In the period from baseline to 1 year, vertical change of mucosal margin amounted to 0.64 ± 0.54 mm in the group without GBR and to 1.17 ± 0.53 mm in the GBR group (P < 0.05). From 1 to 3 years, the mucosal contours remained stable. CONCLUSIONS: Implant placement with simultaneous GBR resulted in more gain of buccal soft tissue contour in comparison with implant placement without GBR. Abutment connection increased the contour of the marginal mucosa at the augmented and the nonaugmented sites. GBR procedure contributed more to the contour gain than did the abutment connection. The augmented and the nonaugmented ridges exhibited stable peri-implant mucosal contour over a 3-year period.

Randomized clinical study assessing two membranes for guided bone regeneration of peri-implant bone defects: clinical and histological outcomes at 6 months.

PURPOSE: To test whether or not one of two membranes is superior for peri-implant-guided bone regeneration in terms of clinical and histologic outcomes. MATERIAL AND METHODS: In 27 patients, 27 two-piece dental implants were placed in single-tooth gaps in the esthetic area. Buccal dehiscence and/or fenestration-type defects were regenerated using demineralized bovine bone mineral and randomly covered with either a resorbable membrane (RES) or a titanium-reinforced non-resorbable membrane (N-RES). Clinical measurements included vertical defect resolution and the horizontal thickness of regenerated bone at implant placement and at 6 months. Statistics were performed by means of nonparametric testing. RESULTS: The remaining mean vertical defect measured 4 mm (±2.07) (RES) and 2.36 mm (±2.09) (N-RES) (P = 0.044) at baseline and 0.77 mm (±0.85) (RES) and 0.21 mm (±0.80) (N-RES) (P = 0.021) at re-entry. This translated into a defect resolution of 85% (RES) and 90.7% (N-RES) (P = 0.10). The horizontal thickness after augmentation measured 3.46 mm (±0.52) (RES) and 2.82 mm (±0.50) (N-RES) (P = 0.004). The mean loss in horizontal thickness from baseline to re-entry measured 2.23 mm (SD ±1.21) (RES) and 0.14 mm (±0.79) (N-RES) (P = 0.017). The horizontal changes in thickness at the implant shoulder level were statistically significant between the groups (P = 0.0001). CONCLUSIONS: Both treatment modalities were clinically effective in regenerating bone as demonstrated by a similar horizontal thickness and vertical defect fill at 6 months. The N-RES group exhibited significantly less horizontal bone thickness reduction from baseline to follow-up.

In-vitro evaluation of the tolerance of surgical instruments in templates for computer-assisted guided implantology produced by 3-D printing.

OBJECTIVE: The aim of this in-vitro study was to compare the tolerance of surgical instruments in surgical guides produced by 3-D printing, without metal sleeves to a surgical guide with conventional metal sleeves from two different manufacturers. MATERIALS AND METHODS: Lateral movements of drill tips caused by tolerance between the sleeve and drill key and between the drill key and the drill were recorded after application of a standardized force to the surgical instruments. Four groups were tested: Control 1 (C1): metal sleeve from commercially available surgical system 1; Test 1 (T1): 3-D-printed sleeve for surgical system 1; Control 2 (C2): metal sleeve from commercially available surgical system 2. Test 2 (T2): 3-D-printed sleeve for surgical system 2. RESULTS: The mean total lateral movement was 0.75 mm (0.5-1.04 mm) in the C1 group and 0.91 mm (0.54-1.34 mm) in the C2 group. The mean amount of movement from tolerance between sleeve and drill-guiding key was 0.31 mm (range 0.22-0.41 mm) in C1 and 0.42 mm (range 0.29-0.56 mm) in C2. This lateral movement was in mean reduced by 0.24 mm (32%) in T1 and by 0.39 mm (43%) in T2 group. This reduction was statistically significant in both groups (P < 0.001). CONCLUSION: The tolerance of surgical instruments and the lateral movements of the drills were significantly reduced by the use of 3-D printing with reduced sleeve diameter. This reduction could improve the overall accuracy in computer-assisted template-guided implant dentistry. The lateral movement of the drill can be further reduced by using a shorter drill and a higher drill key. This can be considered during implant planning and CAD/CAM of surgical guides.

Influence of local administration of pamidronate on extraction socket healing--a histomorphometric proof-of-principle pre-clinical in vivo evaluation.

OBJECTIVES: To evaluate the influence of local administration of pamidronate histomorphometrically, adsorbed on a collagenated porcine bone substitute, on extraction socket healing. MATERIAL AND METHODS: Two American Fox-hound dogs were used within this proof-of-principle study. Following endodontic treatment of the distal root of the three lower premolars, the teeth were hemisected, and the mesial roots were extracted flapless. The sockets were then loosely filled, in a split-mouth fashion, with a collagenated porcine bone substitute (Osteobiol Gen-Os; CPB), rehydrated either with 90 mg/ml pamidronate (Aredia(®) ; test) or with sterile saline (control). Extraction sockets were sealed with connective tissue punches obtained from the palate and secured with sutures. After 4 months of healing, specimens containing the socket sites and remaining roots were retrieved and histomorphometrically examined. RESULTS: Histological evaluation of the sections revealed substantial differences in healing patterns. Control sites presented with various amounts of newly formed bone and no evidence of CPB inside the socket; in contrast, limited amounts of bone were observed at test sites, which were filled with CPB mainly embedded in connective tissue. Only minor differences were observed between test and control sites regarding vertical bone loss (buccal bone: -1.01 mm vs. -1.15 mm; lingual bone: -0.92 mm vs. -1.15 mm). Horizontal bone loss was nearly three times higher in control sites comparing to sites treated with pamidronate (-2.19 ± 1.81 mm vs. -0.80 ± 0.91 mm) at a level corresponding to 3 mm below the cemento-enamel junction (CEJ). CONCLUSION: Local administration of pamidronate adsorbed on a collagenated porcine bone substitute in particulate form appeared to delay extraction socket healing, but may also reduce post-extraction dimensional changes in terms of horizontal bone width. Additionally, pamidronate appears to obstruct resorption of the porcine bone substitute.

Tunnel technique with connective tissue graft versus coronally advanced flap with enamel matrix derivative for root coverage: a RCT using 3D digital measuring methods. Part I. Clinical and patient-centred outcomes.

AIM: The aim of this randomized clinical trial (RCT) was to introduce 3D digital measuring methods for evaluating the outcomes after surgical root coverage (RC) and to assess the clinical performance of the tunnel technique with subepithelial connective tissue graft (TUN) versus the coronally advanced flap (CAF) with enamel matrix derivative in the treatment of shallow localized gingival recession defects. MATERIAL AND METHODS: Twenty-four patients contributed a total of 47 Miller class I or II recessions for scientific evaluation. Clinical outcomes were evaluated at 6 and 12 months. Precise study models gained at baseline and follow-up examinations were optically scanned and virtually superimposed for digital evaluation of clinical outcome measures including percentage of RC and complete root coverage (CRC). Patient-centred outcomes were evaluated with questionnaires. Final aesthetic outcomes were assessed using the root coverage esthetic score (RES). RESULTS: At 12 months, RC was 98.4% for TUN-treated and 71.8% for CAF-treated defects (p = 0.0004). CRC was observed in 78.6% (TUN) and 21.4% (CAF) of the cases (p = 0.0070). Results for patient-centred outcomes were equivalent for both groups but evaluation of the final aesthetic outcomes using the RES revealed a significant difference (9.06 versus 6.92, p = 0.0034) in favour of TUN. CONCLUSIONS: TUN resulted in significantly better clinical outcomes compared with CAF. The new measuring method provided high accuracy and unforeseen precision in the evaluation of treatment outcomes after surgical RC.

Tunnel technique with connective tissue graft versus coronally advanced flap with enamel matrix derivative for root coverage: a RCT using 3D digital measuring methods. Part II. Volumetric studies on healing dynamics and gingival dimensions.

AIM: The aim of this randomized clinical trial (RCT) was to compare the clinical performance of the tunnel technique with subepithelial connective tissue graft (TUN) versus a coronally advanced flap with enamel matrix derivative (CAF) in the treatment of gingival recession defects. The use of innovative 3D digital measuring methods allowed to study healing dynamics at connective tissue (CT)-grafted sites and to evaluate the influence of the thickness of the root covering soft tissues on the outcome of surgical root coverage. MATERIAL & METHODS: Twenty-four patients contributed a total of 47 Miller class I or II recessions for scientific evaluation. Precise study models collected at baseline and follow-up examinations were optically scanned and virtually superimposed for digital evaluation of clinical outcome measures including mean marginal soft tissue thickness (THK). Healing dynamics were measured in a defined region of interest at CT-grafted sites where volume differences between time points were calculated. RESULTS: At 12 months, recession reduction as well as mean root coverage were significantly better at CT-grafted sites treated in the TUN group (1.94 mm and 98.4% respectively) compared to the non-augmented sites of the CAF group (1.17 mm and 71.8% respectively) and statistical analysis revealed a positive correlation of THK (1.63 mm TUN versus 0.91 mm CAF, p < 0.0001) to both these variables. Soft tissue healing following surgical root coverage with CT-grafting was mainly accomplished after 6 months, with around two-thirds of the augmented volume being maintained after 12 months. CONCLUSIONS: The TUN resulted in thicker gingiva and better clinical outcomes compared to CAF. Increased gingival thickness was associated with better surgical outcomes in terms of recession reduction and root coverage.

Labial soft tissue volume evaluation of different techniques for ridge preservation after tooth extraction: a randomized controlled clinical trial.

OBJECTIVE: To volumetrically evaluate soft tissue changes of different ridge preservation techniques compared to spontaneous healing 6 months after tooth extraction. MATERIALS AND METHODS: In each of 40 patients, one single-rooted tooth was extracted and four treatment modalities were randomly assigned to the following groups (n = 10 each): A) ß-tricalcium-phosphate-particles with a polylactid coating (ß-TCP), B) demineralized bovine bone mineral with 10% collagen covered with a collagen matrix (DBBM-C/CM), C) DBBM with 10% collagen covered with an autogenous soft tissue punch graft (DBBM-C/PG), D) spontaneous healing (control). Impressions were obtained before extraction and 6 months later, casts were digitized and volumetric changes at the buccal soft tissues were determined. One-way anova was performed and pair-wise Wilcoxon rank sum test with Bonferroni-Holm method was applied for comparison of differences between two groups. RESULTS: After 6 months, horizontal contour changes accounted for -1.7 ± 0.7 mm (A), -1.2 ± 0.5 mm (B), -1.2 ± 0.7 mm (C) and -1.8 ± 0.8 mm (D). None of the group comparisons reached statistical significance. CONCLUSIONS: Six months after tooth extraction all groups revealed a horizontal volume change in the buccal soft tissue contour. Application of DBBM-C/CM or DBBM-C/PG reduced the amount of volume resorption compared to ß-TCP or spontaneous healing without reaching statistically significant difference.

A randomized controlled clinical multicenter trial comparing the clinical and histological performance of a new, modified polylactide-co-glycolide acid membrane to an expanded polytetrafluorethylene membrane in guided bone regeneration procedures.

OBJECTIVES: To compare the clinical and histological outcomes of a resorbable modified polylactide/polyglycolide acid (PLGA) test membrane and a titanium-reinforced expanded polytetrafluorethylene (ePTFE) control membrane used for guided bone regeneration (GBR) around dental implants. MATERIALS AND METHODS: A total of 40 patients with peri-implant dehiscence-type defects were randomly allocated to a GBR procedure using either a modified PLGA test or an ePTFE control membrane. Soft tissue condition, implant integration, adverse events and quality of life were recorded during the 6-month healing period. At re-entry peri-implant bone defect dimensions were measured and compared with values recorded at implant/GBR surgery. A biopsy was retrieved for qualitative and quantitative histological analyses. A comparison between the groups was conducted using non-parametric statistical tests. RESULTS: Soft tissue complications were observed in five test patients and two control patients. Except for soft tissue complications and incomplete regeneration, no procedure- or device-related adverse events were observed. The vertical bone defect component was, in mean, reduced by-5.1 mm (95% CI -6.8, -3.3) in the test group and -6.9 mm (95% CI -8.2, -5.5 mm) in the control group. The mean residual vertical defect height measured 1.2 ± 2.4 mm in the test group and 0.3 ± 1.1 mm in the control group meaning a mean defect resolution of 81% in the test group and 96% in the control group (P = 0.161). The horizontal bone thickness at implant shoulder level decreased from a mean of 3.2 mm to 1.4 mm (-56%, mean -1.7 mm, 95% CI -2.3, -1.1) in the test group and from 3.3 mm to 2.5 mm (-24%, mean -0.8 mm, 95% CI -1.3, -0.3) in the control group (P = 0.022). Qualitative and quantitative histological analyses did not show significant differences in the tissue composition between groups. CONCLUSION: Peri-implant GBR was successfully performed using either of the membranes. The control membrane was able to better maintain the horizontal thickness of regenerated bone and revealed less soft tissue complications. No statistically valid evidence about the superiority of one membrane was found in any other parameters. Soft tissue dehiscences occur with both types of membranes and can impair the amount of regenerated bone.

Biodegradation and bone formation of various polyethylene glycol hydrogels in acute and chronic sites in mini-pigs.

OBJECTIVE: i) To test whether or not pH modifications of a PEG hydrogel matrix influence degradation time and bone regeneration in acute and unprepared (chronic) defects; and ii) to test whether or not the addition of a PEG hydrogel to hydroxyapatite/tricalciumphosphate (HA/TCP) can further enhance bone regeneration compared to HA/TCP alone in acute defects. MATERIALS AND METHODS: In 11 mini-pigs, three acute standardized defects and one chronic site were prepared in each hemi-mandible. The following treatment modalities were applied in acute defects: PEG hydrogel regular (PEG 8.7), PEG hydrogel pH-modified plus (PEG 9.0), PEG hydrogel pH-modified minus (PEG 8.4), PEG 8.7 mixed with HA/TCP granules (PEG-HA/TCP), HA/TCP granules (HA/TCP), and empty control (control). In chronic sites, PEG 8.7 and PEG 9.0 were applied. Subsequently primary wound closure was obtained and animals sacrificed at 10 (n = 6) and 21 days (n = 5). Descriptive histology and histomorphometric analyses were performed including measurements for newly formed bone, remaining hydrogel, and percent defect fill. Standard descriptive statistics were calculated, and regression analysis used to determine the difference between treatments, taking into account relevant factors and correction for multiple comparisons. RESULTS: In acute defects, the amount of newly formed bone increased statistically significantly over time for all treatments. The increase was higher for PEG 8.7 (35.9%) compared with PEG 8.4 and PEG 9.0 and was higher for PEG-HA/TCP (24.7%) than for HA/TCP (14.6%). The remaining hydrogel ranged between 7.6 ± 13.3% for PEG 8.4 and 17.7 ± 12.8% for PEG 8.7 at 10 days. At 21 days, no remaining hydrogel was found except for PEG-HA/TCP (11.5 ± 10.4%). In chronic sites, at 10 days, the remaining hydrogel covered 29.5 ± 10.3% (PEG 9.0) and 25.6 ± 21.8% (PEG 8.7) of the area. At 21 days, the amount of hydrogel (29.7 ± 31.7% for PEG 9.0; 1.4 ± 2.5% for PEG 8.7) decreased, while the amount of bone increased to 14.0 ± 16.3% for PEG 9.0 and to 37.9 ± 15.7% for PEG 8.7. CONCLUSIONS: The PEG hydrogel matrix with a mid-range pH (PEG 8.7) may serve as a matrix for localized bone regeneration with or without the addition of a bone substitute material. This was demonstrated by enhanced bone regeneration in acute and chronic defects compared with control hydrogels and HA/TCP alone.

Dimensional alterations of extraction sites after different alveolar ridge preservation techniques - a volumetric study.

OBJECTIVES: The aim of this randomized controlled clinical study was to assess soft tissue contour changes after different alveolar ridge preservation procedures. MATERIAL AND METHODS: Following tooth extraction, 30 patients were randomly assigned to the following treatments (Tx) - Tx 1: xenogenic bone substitute (pre-hydrated collagenated cortico-cancellous porcine bone) and free gingival graft; Tx 2: free gingival graft alone; Tx 3: xenogenic bone substitute; Tx 4: no further treatment (control). Impressions were obtained before tooth extraction (baseline) and 4 months after surgery. Cast models were optically scanned, digitally superimposed and horizontal measurements of the contour alterations between time points were performed using digital imaging analysis. RESULTS: All groups displayed contour shrinkage at the buccal aspect ranging from a mean horizontal reduction of -0.8 ± 0.5 mm (Tx 1) to -2.3 ± 1.1 mm (control). Statistically significant differences were found between Tx 1 and Tx 4 as well as Tx 2 and Tx 4. A significant positive influence of the free gingival graft on the maintenance of the ridge width was recorded (p < 0.001). CONCLUSION: In this study, alveolar ridge preservation techniques were not able to entirely compensate for alveolar ridge reduction. Covering the orifice of the extraction socket with a free gingival tissue graft seems to have the potential to limit but not avoid the post-operative external contour shrinkage based on optical scans.

Influence of the crown-to-implant length ratio on the clinical performance of implants supporting single crown restorations: a cross-sectional retrospective 5-year investigation.

PURPOSE: The aim of this study was to investigate the influence of the crown-to-implant length ratio (c/i ratio) on the implant survival, changes of the marginal bone level (MBL) and the occurrence of biological and technical complications. MATERIAL AND METHODS: This cross-sectional retrospective study included all patients with implants in the posterior segments supporting single crown restorations with a minimum follow-up of 5 years. All patients were questioned and examined clinically and radiographically. The technical and biological c/i ratio and the MBL were measured on digitized periapical radiographs. The following outcome parameters in relation to the c/i ratio and the co-factors were statistically analyzed: implant survival rate, MBL, occurrence of technical and biological complications. For statistical analysis, regression, correlation and survival analyses were applied (P<0.05). RESULTS: Seventy patients (mean age of 50.7 years [range 19.8-76.6 years]) with a total of 100 implants (24 Straumann type, 76 Brånemark type) were included in this study. The mean follow-up period was 6.2 years (range 4.73-11.7 years). Six implants failed during the follow-up period, yielding a cumulative survival rate of 95.8% at 5 years in function. The mean technical c/i ratio was 1.04 (±0.26, range 0.59-2.01). The mean biological c/i ratio was 1.48 (±0.42, range 0.82-3.24). No statistically significant influence of the technical and biological c/i ratio was found on the implant survival, MBL and occurrence of technical and biological complications. When adjusted for the biological c/i ratio, smoking was the only co-factor significantly associated with implant failure and biological complications. CONCLUSION: In the present study, the c/i ratio did not influence the clinical performance of implants supporting single crown restorations in the posterior segments of the jaw within the range tested.

Cemented and screw-retained implant reconstructions: a systematic review of the survival and complication rates.

OBJECTIVES: To assess the 5-year survival rates and incidences of complications of cemented and screw-retained implant reconstructions. METHODS: An electronic Medline search complemented by manual searching was conducted to identify randomized controlled clinical trials (RCTs), and prospective and retrospective studies giving information on cemented and screw-retained single-unit and multiple-unit implant reconstructions with a mean follow-up time of at least 1 year. Assessment of the identified studies and data abstraction were performed independently by three reviewers. Failure rates were analyzed using Poisson regression models to obtain summary estimates and 95% confidence intervals of failure rates and 5-year survival proportions. RESULTS: Fifty-nine clinical studies were selected from an initial yield of 4511 titles and the data were extracted. For cemented single crowns the estimated 5-year reconstruction survival was 96.5% (95% confidence interval (CI): 94.8-97.7%), for screw-retained single crowns it was 89.3% (95% CI: 64.9-97.1%) (P = 0.091 for difference). The 5-year survival for cemented partial fixed dental prostheses (FDPs) was 96.9% (95% CI: 90.8-99%), similar to the one for screw-retained partial FDPs with 98% (95% CI: 96.2-99%) (P = 0.47). For cemented full-arch FDPs the 5-year survival was 100% (95% CI: 88.9-100%), which was somewhat higher than that for screw-retained FDPs with 95.8% (95% CI: 91.9-97.9%) (P = 0.54). The estimated 5-year cumulative incidence of technical complications at cemented single crowns was 11.9% and 24.4% at screw-retained crowns. At the partial and full-arch FDPs, in contrast, a trend to less complication at the screw-retained was found than at the cemented ones (partial FDPs cemented 24.5%, screw-retained 22.1%; full-arch FDPs cemented 62.9%, screw-retained 54.1%). Biological complications like marginal bone loss >2 mm occurred more frequently at cemented crowns (5-year incidence: 2.8%) than at screw-retained ones (5-year incidence: 0%). CONCLUSION: Both types of reconstructions influenced the clinical outcomes in different ways, none of the fixation methods was clearly advantageous over the other. Cemented reconstructions exhibited more serious biological complications (implant loss, bone loss >2 mm), screw-retained reconstructions exhibited more technical problems. Screw-retained reconstructions are more easily retrievable than cemented reconstructions and, therefore, technical and eventually biological complications can be treated more easily. For this reason and for their apparently higher biological compatibility, these reconstructions seem to be preferable.

Popliteal vein reflux is associated with increased rates of thrombotic complications after small saphenous vein closure procedures.

BACKGROUND: Venous insufficiency in the small saphenous vein (SSV) is significantly less common than venous insufficiency in the great saphenous vein; the impact of popliteal vein reflux on SSV closure procedural outcomes has yet to be studied. METHODS: A retrospective analysis was performed on 150 SSV closure procedures from 2015 to 2019. Preoperative demographic analysis was performed, after which univariate analyses were performed for postoperative occlusion rates and combined rates of endothermal heat-induced thrombus (EHIT) and endovenous foam-induced thrombus (EFIT). RESULTS: The cohort had a mean age of 58 years, and 116 (77%) were female. Fifty-four patients had C2 disease, 76 had C3 disease, 15 had C4 disease, 1 had C5 disease, and 4 had C6 disease. Twenty-three patients (15.3%) were noted to have popliteal vein reflux on their initial venous insufficiency ultrasound study, compared with 127 (84.6%) who did not. Treatment modalities included 84 radiofrequency ablations (56.0%), 37 polidocanol endovenous microfoam (24.6%), and 29 laser ablations (19.3%). When comparing patients with popliteal vein reflux with those without, there was no significant difference in the occlusion rates at their immediate postoperative visit (99.2% vs 95.6%) or at their 6-month postoperative visit (92.1% vs 91.3%). EHIT/EFIT was noted in 4 of the 23 patients with popliteal vein reflux compared with 4 of the 127 patients without popliteal vein reflux (17.3% vs 3.1%; P = .01). All eight instances of EHIT/EFIT were classified as either arteriovenous fistula class I or II EHIT or EFIT, and all were successfully treated without progression to deep vein thrombosis. CONCLUSIONS: The presence of popliteal vein reflux has no impact on postoperative occlusion rates at 6 months; however, it is associated with a significantly increased rate in EHIT and EFIT. Patients should be counseled on this increased risk should they undergo SSV treatment with known popliteal vein reflux.

Antithrombotic drug removal from whole blood using Haemoadsorption with a porous polymer bead sorbent.

AIM: To evaluate the ability of the DrugSorb™-AntiThrombotic Removal (ATR) haemoadsorption device utilizing porous polymer bead sorbent technology to remove three commonly used antithrombotic drugs from whole blood. METHODS AND RESULTS: We evaluated the removal of apixaban, rivaroxaban, and ticagrelor by the DrugSorb-ATR haemoadsorption device in a benchtop clinical scale model using bovine whole blood. Blood spiked at clinically relevant concentrations of an antithrombotic agent was continuously circulated through a 300-mL DrugSorb-ATR haemoadsorption device at a flow rate of 300 mL/min. Drug concentration was monitored over 6 h to evaluate drug removal. Results were compared with a control circuit without the haemoadsorption device. Removal rates at 30, 60, 120, and 360 minutes were: apixaban: 81.5%, 96.3%, 99.3% >99.8%; rivaroxaban: 80.7%, 95.1%, 98.9%, >99.5%; ticagrelor: 62.5%; 75%, 86.6%, >95% (all P <0.0001 vs. control). Blood pH and haematological parameters were not significantly affected by the DrugSorb-ATR haemoadsorption device when compared with the control circuit. CONCLUSION: DrugSorb-ATR efficiently removes apixaban, rivaroxaban, and ticagrelor in a clinical-scale benchtop recirculation circuit with the bulk of removal occurring in the first 60 minutes. The clinical implications of these findings are currently investigated in patients undergoing on-pump cardiothoracic surgery in two US pivotal trials (ClinicalTrials.gov Identifiers: NCT04976530 and NCT05093504).

Bone regeneration using a synthetic matrix containing enamel matrix derivate.

PURPOSE: The aim of the present study was to test whether the delivery of enamel matrix derivate (EMD) via synthetic polyethylene glycol (PEG)-based hydrogels with and without RGD sequences enhances bone formation in vivo. MATERIAL AND METHODS: In each of 10 rabbits, four titanium cylinders were placed on the external cortical bones of their calvaria. The following four treatment modalities were randomly allocated: One of the four cylinders was left empty (control), the other three were filled with a combination of PEG matrix with hydroxyapatite/tricalciumphosphate (HA/TCP) granules and EMD in a concentration of 100 µg/ml (test 1) or 500 µg/ml (test 2) or 500 µg/ml and RGD peptide (test 3). After 8 weeks, the animals were sacrificed and ground sections were obtained for histological analysis. For statistical analysis, the Kruskal-Wallis test was applied (P<0.05). RESULTS: The histomorphometric analysis revealed a statistically larger area fraction of newly formed bone in the EMD 500/RGD group (54.8±14.5%) compared with the control group (28.7±10.3%) and the EMD 500 group (31.2±14.1%) and non-significantly higher area fraction compared with the EMD 100 group (38.2±10.4%). The percentage of mineralized bone showed no statistically significant differences among the four groups. The mean percentage of mineralized bone was 13.6±3.3% in the control group, 14.2±5.8% in the EMD 100 group, 11.69±5.9% in the EMD 500 group and 15.66±5.2% in the EMD 500/RGD group. No statistically significant difference regarding the bone-to-graft contact between the EMD 100 group (23±15.7%), the EMD 500 group (22.2±14.6%) and the EMD 500/RGD group (21.6±8.8%) was observed. CONCLUSIONS: The combination of a PEG matrix containing EMD with HA/TCP granules had no effect on the formation of mineralized bone tissue in rabbit calvaria. The addition of RGD peptide to the PEG/EMD 500 combination increased the area fraction of newly formed bone compared with the other treatment groups. Further studies are indicated to study a possible synergistic effect of EMD and RGD.

Volume gain and stability of peri-implant tissue following bone and soft tissue augmentation: 1-year results from a prospective cohort study.

OBJECTIVES: the aim of the present study was to evaluate the dimensional changes of peri-implant tissues obtained by implant placement, bone and soft tissue augmentation, prosthetic reconstruction and 1 year of function using a new, non-invasive method for volumetric measurements. MATERIALS AND METHODS: in 16 patients, the missing central or lateral maxillary incisor was reconstructed with an implant-supported single crown. Impressions were taken before (t1), after implant placement with guided bone regeneration using DBBM and a PTFE membrane (t2), after soft tissue augmentation (t3), immediately after crown placement (t4) and 1 year later (t5). The cast models were optically scanned and digitally superimposed allowing qualitative and quantitative analysis of alterations of the labial peri-implant tissue contour. In addition, the crown length and papilla height were measured at crown placement (t4) and after 1 year (t5). RESULTS: fifteen patients were available for recall after 1 year. During therapy, a mean gain in distance in the labial direction of 1.27 ± 0.67 mm was observed after the surgical procedures. One year after crown insertion, a mean loss of 0.04 ± 0.31 mm in the labial direction was recorded. During the same period, the crown length increased by a mean of 0.22 ± 0.57 mm and the papilla height by 0.07 ± 0.61 mm. The degree and pattern of tissue change following crown insertion were highly variable between individuals, irrespective of the amount and quality of previously augmented tissues. CONCLUSIONS: the clinical procedures were effective in augmenting peri-implant tissue volume that remained stable to a high degree within 1 year after crown insertion. Large inter-individual variations regarding the tissue alterations were observed.