Influence of an allogenic collagen scaffold on implant sites with thin supracrestal tissue height: a randomized clinical trial

OBJECTIVES

This randomized clinical trial focused on patients with thin peri-implant soft-tissue height (STH) (≤ 2.5 mm) and investigated the impact of an allogenic collagen scaffold (aCS) on supracrestal tissue height and marginal bone loss (MBL).

MATERIAL & METHODS

Forty patients received bone level implants and were randomly assigned to the test group with simultaneous tissue thickening with aCS or the control group. After three months, prosthetic restoration occurred. STH measurements were taken at baseline (T0) and reopening surgery (TR), with MBL assessed at 12 months (T1). Descriptive statistics were calculated for continuous variables, and counts for categorical variables (significance level, p = 0.05).

RESULTS

At T1, 37 patients were available. At T0, control and test groups had mean STH values of 2.3 ± 0.3 mm and 2.1 ± 0.4 mm. TR revealed mean STH values of 2.3 ± 0.2 mm (control) and 2.6 ± 0.7 mm (test), with a significant tissue thickening of 0.5 ± 0.6 mm in the test group (p < 0.03). At T1, control and test groups showed MBL mean values of 1.1 ± 0.8 mm and 1.0 ± 0.6 mm, with a moderate but significant correlation with STH thickening (-0.34), implant position (0.43), history of periodontitis (0.39), and smoking status (0.27).

CONCLUSION

The use of an aCS protocol resulted in soft tissue thickening but did not reach a threshold to reliably reduce MBL compared to the control group within the study's limitations.

CLINICAL RELEVANCE

Peri-implant STH is crucial for maintaining peri-implant marginal bone stability. Marginal bone stability represents a crucial factor in prevention of peri-implantitis development. German register of clinical trial registration number DRKS00033290.

LONG-TERM OUTCOMES OF IMPLANT PLACEMENT VERSUS TOOTH PRESERVATION IN PERIODONTALLY COMPROMISED TEETH MAY BE COMPARABLE

ARTICLE TITLE AND BIBLIOGRAPHIC INFORMATION

Sarafidou K, Lazaridi I, Gotsis S, Kirmanidou Y, Vasilaki D, Hirayama H, Michalakis K. Tooth preservation vs. extraction and implant placement in periodontally compromised patients: A systematic review and analysis of studies. J Prosthodont. 2022 Oct;31(8):e87-e99. doi:10.1111/jopr.13560. Epub 2022 Aug 2. PMID: 35794083 SOURCE OF FUNDING: No external funding was received for this research.

TYPE OF STUDY/DESIGN

Systematic review (without meta-analysis).

Immediately versus early placed bone-level-tapered implants supporting all-ceramic crowns on titanium base abutments: 1-year radiographic and pink esthetic outcomes of a multicenter pilot RCT

OBJECTIVES

Aim of this study was to assess survival rates, radiographic, and pink esthetic outcomes of a bone-level-tapered (BLT) implant following immediate or early implant placement.

MATERIALS AND METHODS

Patients in need of tooth extraction and one implant in the anterior or premolar area were recruited in five centers. Patients were randomly assigned to the immediate or early placement protocol. Implants were restored with all-ceramic crowns cemented to titanium-base-abutments. Radiographic bone levels, implant stability quotient (ISQ), and pink esthetic outcomes were assessed. Data were analyzed descriptively. Level of significance was set at 0.05. Differences between groups were tested using Wilcoxon-signed-rank and Mann-Whitney-U test as nonparametric tests.

RESULTS

A total of 60 patients received 60 BLT implants (Institut Straumann). At 12-months, 59 implants (98.3%) were osseointegrated. The mean distance from implant shoulder to first bone-to-implant contact was 0.15 ± 0.59 mm without significant differences between the groups. Median ISQ values increased from 75.5 to 78.5. A mean buccal recession of 0.1 ± 0.70 mm occurred with no difference between groups. The mean papilla height gain in both groups was 0.5 ± 1.47 mm mesially and 0.4 ± 1.36 mm distally.

CONCLUSIONS

After 1 year, immediately and early placed BLT implants exhibit similar bone level changes, ISQ values, and pink esthetic outcomes.

CLINICAL SIGNIFICANCE

The present research contributes to the knowledge on clinical outcomes of immediately and early placed BLT implants restored with buccally microveneered ceramic single crowns out of two different ceramic materials. The research shows that similar esthetic and radiographic outcomes can be reached by means of immediate implant placement compared to the conventional early placement protocol. The improvement of esthetic soft-tissue parameters over time was shown for both implant placement protocols.

Properties of three collagen scaffolds in comparison with native connective tissue: an in-vitro study

PURPOSE

To evaluate collagen scaffolds (CS) in terms of their in vitro resorption behavior, surface structure, swelling behavior, and mechanical properties in physiologically simulated environments, compared with porcine native connective tissue.

MATERIALS AND METHODS

Three test materials-one porcine collagen matrix (p-CM), two acellular dermal matrices (porcine = p-ADM, allogenic = a-ADM)-and porcine native connective tissue (p-CTG) as a control material were examined for resorption in four solutions using a high-precision scale. The solutions were artificial saliva (AS) and simulated body fluid (SBF), both with and without collagenase (0.5 U/ml at 37 °C). In addition, the surface structures of CS were analyzed using a scanning electron microscope (SEM) before and after exposure to AS or SBF. The swelling behavior of CS was evaluated by measuring volume change and liquid absorption capacity in phosphate-buffered saline (PBS). Finally, the mechanical properties of CS and p-CTG were investigated using cyclic compression testing in PBS.

RESULTS

Solutions containing collagenase demonstrated high resorption rates with significant differences (p < 0.04) between the tested materials after 4 h, 8 h and 24 h, ranging from 54.1 to 100% after 24 h. SEM images revealed cross-linked collagen structures in all untreated specimens. Unlike a-ADM, the scaffolds of p-CM and p-ADM displayed a flake-like structure. The swelling ratio and fluid absorption capacity per area ranged from 13.4 to 25.5% among the test materials and showed following pattern: p-CM > a-ADM > p-ADM. P-CM exhibited higher elastic properties than p-ADM, whereas a-ADM, like p-CTG, were barely compressible and lost structural integrity under increasing pressure.

CONCLUSIONS AND CLINICAL IMPLICATIONS

Collagen scaffolds vary significantly in their physical properties, such as resorption and swelling behavior and elastic properties, depending on their microstructure and composition. When clinically applied, these differences should be taken into consideration to achieve the desired outcomes.

Three-Dimensional Peri-Implant Tissue Changes in Immediately vs. Early Placed Tapered Implants Restored with Two Different Ceramic Materials-1 Year Results

BACKGROUND

A prospective multi-center randomized controlled clinical trial was performed to digitally analyze tissue volume changes in immediately and early placed implants with simultaneous bone augmentation restored with two different all-ceramic materials.

METHODS

A total of 60 patients received 60 bone-level tapered implants (BLT, Straumann AG) immediately (n = 30) or early placed, 8-10 weeks after tooth extraction, (n = 30). Implants were restored with all-ceramic single crowns fabricated out of zirconia (Lava Plus, 3M), or lithium disilicate (E.max CAD, Ivoclar Vivadent AG) bonded to titanium base abutments (Variobase for Cerec, Straumann AG). Impressions were taken at baseline (BL), 6 and 12 months, and STL data were used to define an area of interest (AOI) to analyze peri-implant volume changes and midfacial recessions.

RESULTS

For immediate placement, a mean volume loss of -5.56 mm3 (±5.83 mm3) was found at 6 months, and of -6.62 mm3 (±6.56 mm3) at 12 months. For early placement, a mean volume loss of -1.99 mm3 (±5.82 mm3) at 6 months, and of -3.7 mm3 (±5.62 mm3) at 12 months was found. The differences in volume loss at 12 months between the two implant placement protocols were significant (p = 0.005). In both groups, mean midfacial recessions of 0.48 mm (±0.52) occurred.

CONCLUSIONS

A more pronounced peri-implant volume loss can be expected 12 months after immediate implant placement compared with early placement.

Radiographic results of osteotome-driven maxillary sinus floor elevation without grafting materials after 17.5 years radiographic evaluation of minimally-invasive sinus grafting

BACKGROUND

There is growing evidence that minimally invasive sinus augmentation works without the use of filler materials. This study assessed the bone integration and sinus projection of single-unit implants in the maxilla, which were placed approximately 18 years ago using a modified filler-free osteotome technique.

METHODS

Sixteen of the 24 treated patients of a former publication (treatment was performed between 2001 and 2004) were reassessed after a mean implant loading period of 17.5 years. The treated posterior areas were evaluated using cone-beam computed tomography (CBCT), and as a primary outcome parameter, sinus projection was determined in sectional views at the mesial, distal, buccal, and oral sites. Additionally, the percentage of alveolar bone contact was determined with respect to the implant length. Conventional radiographs were used to determine marginal bone levels. Additionally, plaque, bleeding on probing, and probing pocket depth were measured. The reconstructions were checked for chipping and other technical complications such as loss of retention, screw loosening, and screw fracture.

RESULTS

The mean age of the included patients was 72.8 ± 8.5 years. Two implants were lost. Therefore, fourteen implants were available for CBCT evaluation. The highest sinus projection of 2.1 ± 1.7 mm was observed in the distal aspect, while it was 1.1 ± 1.5, 0.9 ± 1.2, and 0.9 ± 1.1 mm at the mesial, buccal, and oral sites, respectively. The maximal sinus projection in one case was 6.7 mm. The percentage calculation of osseous implant integration (in mm ± standard deviations) with respect to the selected implant length at the mesial, distal, buccal, and oral sites showed values ranging from, 87.9 ± 16.0, 78.4 ± 20.3, 91.0 ± 12.5, and 90.5 ± 11.1%, respectively. Five implants displayed probing pocket depths of more than 4 mm with bleeding; all implants had less than 1 mm of bone loss in the observation period, that is, implants had mucositis. Six of 14 crowns showed small chippings within the ceramic veneering. One case of screw loosening was reported in medical history.

DISCUSSION

This study showed that implant placement in non-augmented sinuses resulted in good clinical results. The sinus projection, even if persistent and present, leads to no functional impairments. Given adequate maintenance, marginal bone levels remain constant and peri‑implant health can be observed. Moreover, these results represent only a small cohort; and therefore, should be interpreted with caution. However, in view of the existing literature, these highly promising results are in line with other findings.

CLINICAL SIGNIFICANCE

To the best of our knowledge, this dataset is the report with the longest follow-up. Overall, implants placed in the sinus without fillers represent a valuable alternative for tooth replacement in a minimally interventional manner.

In Vitro Evaluation of the Permeability of Different Resorbable Xenogeneic Membranes after Collagenolytic Degradation

In this in vitro study, we compare the penetration of cells through different resorbable collagen membranes, which were collagenolytically degraded over different time periods. Three different resorbable collagen membranes were evaluated, including two non-cross-linked (NCL) membranes-namely, a porcine (NCL-P) and an equine (NCL-E) membrane-and an enzymatically cross-linked porcine (ECL-B) membrane. A special two-chamber model was fabricated, allowing for the placement of separating membranes, and a non-porous polyester membrane was used as a negative control (C), in order to verify the impermeability of the experimental chamber device. Round membrane samples with a diameter of 16 mm were fabricated. Eighteen membranes of each type were punched and placed on polyethylene nets as carriers. The membranes were then biodegraded-each on its carrier-in 12-well polystyrene plates: three samples of each membrane type were degraded for 1.5, 3, 6, or 12 h in 2 mL of a buffered collagenase solution, at 37 °C. For control purposes, three samples of each membrane type were not degraded, but only immersed in buffer solution for 1.5, 3, 6, or 12 h, at 37 °C. Another three samples of each type of membrane were degraded until complete dissolution, in order to determine the full hydroxyproline content for comparison. Liquid-preserved boar semen (containing at least 120 million sperm cells per milliliter) was used to test the cell occlusivity of the degraded membranes. At baseline and initial degradation, all tested membranes were tight, and no penetration was observed with up to 30 min of incubation time (results not shown). After 1.5 h, cells were partially capable of penetrating the NCL-E membrane only. One sample showed leakage, with a sperm volume of 1.7 million cells/mL over all samples. No penetration occurred in the test, NCL-P, and ECL-B groups. After a degradation time of 3 h, the NCL-P and ECL-B membranes remained occlusive to cells. All the membranes and measurements indicated leakage in the NCL-E group. After 6 h, four NCL-P measurements showed the first signs of cell penetration, as boar spermatozoa were detectable in the lower chamber (64 million cells/mL). The ECL-B membranes remained completely cell occlusive. After 12 h, four NCL-P measurements were cell penetration positive (14.6 million cells/mL), while the ECL-B group remained tight and showed no cell penetration. As the findings of our study are well in accordance with the results of several previous animal studies, it can be concluded that the surrogate model is capable of performing rapid and cheap screening of cell occlusivity for different collagen membranes in a very standardized manner. In particular, claims of long degradation resistance can be easily proven and compared. As the boar spermatozoa used in the present report had a size of 9 × 5 μm, smaller bacteria are probably also able to penetrate the leaking membranes; in this regard, our proposed study set-up may provide valuable information, although it must be acknowledged that sperm cells show active mobility and do not only translocate by growth.

Mechanical Stability of Restorations Supported by Titanium Base, Zirconia, and Polyetherketoneketone Abutments on One- and Two-Piece Zirconia Implants

PURPOSE

To evaluate survival, complication rates, and bending moments of one- and two-piece zirconia implants restored with different abutment materials and lithium disilicate crowns after aging, compared to titanium implants restored with titanium base-supported lithium disilicate crowns.

MATERIALS AND METHODS

Sixty anterior crowns were either screwretained on two-piece titanium implants (C) and two-piece zirconia implants (T1, T2, T3) or cemented on one-piece zirconia implants (T4), resulting in 5 groups with 12 specimens each. For the screw-retained crowns, different abutment materials and implant connections were tested: titanium base with internal conical connection and horizontal joint component (C and T2), zirconia with internal hexagonal connection and horizontal joint component (T1), and polyetherketoneketone with internal hexagonal connection and horizontal joint component (T3). After artificial aging with thermocycling (5°C to 50°C) and chewing simulation (1,200,000 cycles, 49 N, 1.67 Hz), the surviving specimens were loaded until fracture, and the bending moments were calculated. Survival rates and respective differences during aging were analyzed with the Kaplan-Meier log-rank test, while complication rates were compared with chi-square tests. Bending moment data were evaluated using the Kruskal-Wallis test (α = .05).

RESULTS

Survival rates after artificial aging ranged from 75% (T1) to 100% (C and T4) without significant differences between the groups (P > .05). Only 41.5% of the surviving specimens were free of complications, while the remaining presented screw-loosening, loss of retention of crowns, or cracks on the crown or implant level. The complication rates varied significantly among the groups (P < .05). The mean bending moments were 173.7 × 20.1 (C), 114.5 × 20.1 (T1), 171.1 × 46.1 (T2), 258.1 × 147.4 (T3), and 194.7 × 30.9 Ncm (T4), and group T1 exhibited significantly lower median bending moment values than the other groups (P < .001).

CONCLUSION

The zirconia one- and two-piece implants presented high survival rates after aging, yet the number of technical complications was high. New prosthetic solutions, such as titanium bases or polyetherketoneketone abutments, may offer a comparable treatment option to restore two-piece zirconia implants.

Clinical and radiographic changes at tissue level implants with either a machined or a modified transmucosal neck surface: A 3-year multicentre randomized controlled proof-of-concept study

BACKGROUND

Surface modification may yield enhanced soft tissue adhesion to transmucosal titanium implant necks.

AIM

To evaluate and compare changes in soft tissues around implants with a modified hydrophilic sandblasted and acid-etched neck (mSLA; test) to those with a machined neck (M; control).

MATERIALS AND METHODS

Implants with a diameter of 4.1 mm and a neck height of 1.8 mm were randomly inserted in healed sites with pristine bone of the posterior maxilla or mandible. The modified Sulcus Bleeding Index (mSBI) (primary outcome) was assessed at baseline (BL) and 6, 12 and 36 months. Secondary outcomes included the assessment of pocket probing depth (PPD), mucosal recession (REC) and clinical attachment level (CAL). Standardized radiographs were taken at time of implant placement, at BL and after 12 and 36 months.

RESULTS

Of the 43 randomized subjects, 38 (19 test and 19 controls) completed the 36-month follow-up. Implant survival rates amounted to 95.5% (test) and 100% (control) (p > .05). At 36 months, 77.6% of test implants and 78.9% of control implants were without any bleeding sites (mSBI = 0; p > .05). The 36-month success rate was 86.4% in the test and 85.7% in the control group, respectively (p > .05). At 36 months, the mean radiographic bone level change from BL was 0.33 ± 0.69 mm at test implants and 0.12 ± 0.3 mm at control implants (p > .05).

CONCLUSION

Tissue level implants with a hydrophilic mSLA transmucosal neck failed to yield clinical and radiographic benefits compared with implants with a machined neck up to 3 years.

Monolithic zirconia multiple-unit implant reconstructions on titanium bonding bases

The development of titanium bonding bases allows for the use of implant-supported monolithic reconstructions in a digital workflow. Different base configurations are available according to each clinical indication. In this case report, the selection of titanium bonding bases for crowns was considered for a multiple-unit fixed dental prosthesis (FDP).

Theoretical knowledge in implant dentistry for undergraduate students

Implant therapy has evolved into an important part of daily dental practice. Appropriate knowledge of diagnostic and therapeutic options with dental implant therapy is, therefore, mandatory for dental students. The present consensus paper describes the theoretical knowledge as a foundation to the teaching of implant dentistry at the undergraduate level. Students need a solid basic knowledge about biological prerequisites and clinical procedures leading to successful implant treatment and, in particular, an understanding of the importance of embedding implants into the overall treatment concept. Among others this includes aspects of bone and soft tissue integration of dental implants, as well as aspects of materials that are used in implant dentistry. The students should also be able to differentiate between low, medium and high-risk situations, which assumes that they have knowledge about a proper clinical examination. Furthermore, the students need to be able to inform the patient about the different treatment options and their advantages and disadvantages. Frequently, a choice has to be made between an FDP anchored on teeth and an implant-borne reconstruction. This is highly influenced by the long-term prognosis of the different treatment options. In order to perform implant placement in uncomplicated cases and to give appropriate patient information, adequate knowledge of surgical procedure and surgical complications is mandatory. Furthermore, the dentist needs to be competent in evaluating clinical situations and in advising patients about the suitability of the different options, e.g. removable or fixed reconstructions. It is possible that peri-implant tissue destruction may be a more common finding during long-term service of implant-borne reconstructions than was previously believed. The dentist needs knowledge about etiology and pathogenesis of peri-implantitis and should know how to provide an effective maintenance care programme. In cases of peri-implantitis the student should be knowledgeable regarding suitable interventions.