In vivo experimental study comparing alveolar ridge preservation versus guided bone regeneration after unassisted socket healing at intact and damaged sites in narrow alveolar ridges.

BACKGROUND: To compare bone regeneration and dimensional alteration of alveolar ridge at intact and damaged extraction sockets after alveolar ridge preservation (ARP) and implant placement versus unassisted socket healing followed by guided bone regeneration (GBR) with simultaneous implant placement. METHODS: In 6 beagle dogs, 3 types of extraction sockets in the mandible were created: (1) intact sockets, (2) 1-wall defect sockets and (3) 2-wall defect sockets. The sockets were allocated to undergo either (1) ARP and implant placement 8 weeks later (ARP group) or (2) GBR with simultaneous implant placement after 8 weeks of unassisted socket healing (GBR group). After an additional healing period of 8 weeks, bone regeneration and dimensional changes were evaluated radiographically and histologically. RESULTS: GBR showed superior bone formation and greater bone gains compared to ARP, regardless of the initial extraction-socket configuration. Although ARP maintained the preexisting alveolar ridge dimensions, peri-implant bone defects were still detected at 8 weeks of follow-up. Histomorphometric analyses confirmed that GBR increased dimensions of the alveolar ridge compared to baseline, and the augmentation and bone regeneration were greater with GBR than with ARP. CONCLUSION: Early implant placement with ARP can mitigate alveolar ridge changes in the narrow alveolar ridge. However, early implant placement with simultaneous GBR creates the conditions for enhanced bone regeneration around the implant and greater ridge augmentation compared to ARP, irrespective of the extraction-socket configuration.

Collagen Matrix for Increasing Peri-implant Mucosal Thickness in Smokers: A Prospective Case Series.

This prospective case series aimed to evaluate the feasibility of using a volume collagen matrix for soft tissue augmentation to increase mucosal thickness in single implants in smokers who consume more than 10 cigarettes per day. Participants had single submerged implants necessitating soft tissue thickening. Soft tissue augmentation was done using a collagen matrix in the second-stage surgery. The primary outcome was soft tissue thickness at 90 days post-surgery. Secondary outcomes included median thickness at 30 and 60 days, changes in buccal soft tissue profile (digital measurements) at 30, 60, and 90 days, and oral health-related quality of life using OHIP-14 up to 90 days post-surgery. Pain levels via VAS scale and adverse effects were also assessed. Ten participants (4 men, 6 women) aged 45.2 ± 13.18 years initially smoked 10-20 cigarettes daily (average: 14.70 ± 3.47 cigarettes/day). After 90 days, median soft tissue thickness increased to 3.00 (2.00;3.00) mm. Buccal soft tissue profile (median change in ROI) increased by 0.40 (0.25;0.62) mm at 90 days. Pain levels decreased, and oral health-related quality of life improved significantly. No complications were reported. The collagen matrix significantly augmented buccal soft tissue thickness at implant sites in smokers (>10 cigarettes/day), with favorable outcomes and no complications.

Association of Peri-Implant Mucosa Dimensions With Emergence Profile Angles of the Implant Prosthesis.

OBJECTIVES: The primary aim of this cross-sectional study was to investigate the association between prosthesis design and peri-implant mucosa dimensions and morphology. The secondary aim was to investigate associations between mucosal dimensions and the presence of mucositis. MATERIALS AND METHODS: Forty-seven patients with 103 posterior bone level implants underwent clinical and radiographic examination, including cone beam computer tomography and intraoral optical scanning. Three-dimensional models for each implant and peri-implant mucosa were constructed. Vertical mucosa height (TH), horizontal mucosa width at implant platform (TW), and 1.5 mm coronal of the platform (TW1.5), as well as mucosal emergence angle (MEA), deep angle (DA), and total contour angle (TA) were measured at six sites for each implant. RESULTS: There was a consistent correlation between peri-implant mucosa width and height (ß = 0.217, p < 0.001), with the width consistently surpassing height by a factor of 1.4-2.1. All three angles (MEA, DA, TA) were negatively associated with mucosa height (p < 0.001), while DA was negatively associated with mucosa width (TW1.5) (p < 0.001, ß = -0.02, 95% CI: -0.03, -0.01). There was a significant negative association between bleeding on probing (BoP) and mucosa width at platform (OR 0.903, 95% CI: 0.818-0.997, p = 0.043) and 1.5 coronal (OR 0.877, 95% CI: 0.778-0.989, p = 0.033). Implants with less than half sites positive for BoP (0-2/6) had significantly higher mucosa height (OR 3.51, 95% CI: 1.72-7.14, p = 0.001). CONCLUSIONS: Prosthesis design can influence the dimensions of the peri-implant mucosa, with wider emergence profile angles associated with reduced peri-implant mucosa height. In particular, a wider deep angle is associated with reduced mucosa width in posterior sites. Reduced peri-implant mucosa height and width are associated with more signs of inflammation. TRIAL REGISTRATION: Registered in Thai Clinical Trials Registry: http://www.thaiclinicaltrials.org/show/TCTR20220204002.

Two-Step Periosteal Releasing Incision for Tension-Free Flap Closure After Implant Placement With Simultaneous Guided Bone Regeneration.

We evaluated the effect of periosteal-releasing incisions on flap displacement in anterior maxillary sites following implant placement and simultaneously guided bone regeneration. Thirty patients, each requiring a single dental implant and guided bone regeneration in the maxillary esthetic zone, were recruited. After full-thickness flap elevation, the displacement of the flap was measured under a standardized tension of 1 Ncm. Then, a 2-step periosteal releasing incision was placed in the internal aspect of the flap, and the displacement was remeasured using the same standardized tension. Keratinized tissue width and mucosal thickness at the surgical site were recorded. Patient-reported outcomes were assessed at the 7- and 14-day recall visits. Flap displacement (primary outcome) was calculated before and after periosteal-releasing incisions. Multivariable linear regression models were used to evaluate the influence of mucosal thickness on flap displacement and adjusted for Keratinized tissue width. Primary wound closure was achieved in all patients. The mean difference in flap coronal displacement before and after the periosteal-releasing incisions was 8.2 mm (p < .0001). Adjusted regression models showed no association between mucosal thickness and keratinized tissue width with the amount of flap displacement (p = .770). Patient-reported outcome measures for pain, swelling, and bleeding amounted to 1.28 ± 1.93, 1.36 ± 1.87, and 0.0 ± 0.0 at 7 days and 0.11 ± 0.57, 0.56 ± 1.03, and 0.0 ± 0.0 at 14 days, respectively. Periosteal-releasing incisions using the 2-step procedure described here are a predictable technique to obtain coronal flap displacements >8 mm without increased surgical complications.

Immediate loading on two adjacent single dental implants with definitive nonsplinted restorations: A proof of concept in the posterior zone.

OBJECTIVES: To evaluate clinical, clinician- and patient-reported outcomes (PROs) of two adjacent single posterior implants immediately loaded with definitive single crowns up to 1 year. Ten patients in need of two adjacent posterior single implants were included. All implants were placed applying a fully digital workflow. Definitive screw-retained single zirconia crowns were delivered within 72 h after implant placement. Clinical parameters, patient- and clinician-reported outcomes were assessed up to 1 year of follow-up. CLINICAL CONSIDERATIONS: Clinical outcomes remained stable, with no implant failures or technical and biological complications throughout the observation period. Patient satisfaction was very high at baseline (crown delivery) and remained consistently high at 6 and 12 months of follow-up. Crown insertion 3 days after implant placement was rated as an easy procedure by clinicians. CONCLUSIONS: Two adjacent single implants with immediate definitive restorations (<72 h) in the posterior region appear to be a viable and easy treatment option to shorten the overall treatment time and potentially enhancing patient satisfaction. However, randomized controlled trials are needed to confirm the advantages of this treatment protocol over a delayed loading approach. CLINICAL SIGNIFICANCE: In selected cases, immediate implant loading with definitive restorations in the posterior region appears a valuable and straightforward option to shorten the overall treatment time.

The distance of insertion points from wound margins in interrupted and vertical mattress sutures influences the tensile load capacity: An in vitro experimental study.

AIM: To determine the tensile load capacity (TLC) and the tearing characteristics for interrupted and vertical mattress sutures with different insertion points from the wound margin, and the effect of the bite size when using vertical mattress sutures. MATERIALS AND METHODS: A total of 120 gingiva and lining mucosa samples obtained from pig jaws were divided into groups according to the suturing technique (interrupted and vertical mattress sutures), distance of the insertion points from the wound margin (margin, 1, 3, and 5 mm) and bite size (1, 3, and 5 mm). The TLC of the suture and the tearing characteristics were evaluated using a tensile tester device. RESULTS: The TLC was significantly higher for vertical mattress sutures than for interrupted sutures regardless of the distance of the insertion points from the wound margin (intergroup p < .001). This distance significantly influenced the TLC for vertical mattress sutures (p < .05) but not for interrupted sutures (p > .05). Testing the tearing characteristics revealed that no tissue tearing occurred in groups when the insertion points were more than 3 mm from the wound margin. CONCLUSION: The TLC is higher for vertical mattress sutures than for interrupted sutures, and it increases when the insertion points are farther from the wound margin.

The use of digital technologies in peri-implant soft tissue augmentation - A narrative review on planning, measurements, monitoring and aesthetics.

OBJECTIVE: To identify the different uses and modalities of digital technologies to diagnose, plan and monitor peri-implant soft tissue conditions and aesthetics. METHODS: A comprehensive narrative review of pertinent literature was conducted, critically appraising key digital technologies that may assist peri-implant soft tissue augmentation and assessment. An electronic search on four databases including studies published prior to 1st July 2023 was performed and supplemented by a manual search. RESULTS: Predominantly, tools such as cone beam computed tomography (CBCT), intraoral scanning (iOS), intraoral ultrasonography and digital spectrophotometry were commonly to assess and monitor peri-implant soft tissues. The main clinical and research applications included: (i) initial assessment of mucosal thickness, supra-crestal tissue height and keratinized mucosa width, (ii) evaluation of peri-implant soft tissue health and inflammation, (iii) monitoring profilometric changes and midfacial mucosal margin stability over time and (iv) aesthetic evaluation through colour assessment. While evidence for some digital tools may be limited, the integration of digital technologies into peri-implant soft tissue management holds great promise. These technologies offer improved precision, comfort and speed in assessment, benefiting both patients and clinicians. CONCLUSION: As digital technologies progress, their full potential in peri-implant soft tissue augmentation and their value will become more evident with ongoing research. Embracing these innovations and their potential benefits is recommended to ensure that during progress in implant dentistry, patient care is not hindered.

Alveolar ridge changes 1-year after early implant placement, with or without alveolar ridge preservation at single-implant sites in the aesthetic region: A secondary analysis of radiographic and profilometric outcomes from a randomized controlled trial.

OBJECTIVES: To assess both the radiographic and profilometric outcomes of early implant placement with or without alveolar ridge preservation (ARP) (using two different ARP techniques) after 1 year of loading. MATERIALS AND METHODS: Seventy-five patients with a failing single tooth in the anterior maxilla were randomly allocated to three groups (1:1:1): (a) ARP using demineralized bovine bone mineral containing 10% collagen (DBBM-C) covered by a collagen matrix (CM), (b) ARP using DBBM-C covered with a palatal graft (PG), and (c) unassisted socket healing (control). Eight weeks after tooth extraction, early implant placement was performed in all patients. Cone-beam computed tomography (CBCT) and impressions were taken 8 weeks after tooth extraction (ARP/unassisted healing) prior to implant placement and 1-year post-loading. Radiographic and profilometric outcomes were evaluated. RESULTS: Out of the 70 patients available for re-examination at 1-year post-loading, 55 datasets could be assessed (ARP-CM 19; ARP-PG 17; Control 19). The need for additional guided bone regeneration (GBR) at implant placement amounted to 31.6% (ARP-CM), 29.4% (ARP-PG), and 68.4% (unassisted healing). Adjusted models revealed that residual buccal bone height and additional GBR at implant placement significantly influenced the magnitude of the alveolar changes at 1 year (p < 0.05). In patients with ARP (group ARP-CM or ARP-PG) without additional GBR, the presence of bone convexity amounted to 36.0% (9/25) at 1-year post-loading. For patients that received ARP and additional GBR at implant placement, the frequency of bone convexity increased to 72.7% (8/11) (p = 0.042). Regarding profilometric measurements, a tendency toward agreement with radiographic outcomes was observed. CONCLUSIONS: Early implant placement with ARP can attenuate alveolar ridge changes at 1-year post loading by minimizing both radiographic and profilometric alterations. However, early implant placement with simultaneous GBR consistently yields superior radiographic and profilometric outcomes, regardless of whether ARP is performed.

Pilot Study: Periosteal Mattress Sutures as an Alternative to Pins and Screws in Guided Bone Regeneration in the Esthetic Zone.

OBJECTIVES: To quantify the buccal bone thickness, area, and perimeter following guided bone regeneration (GBR) using stabilizing periosteal sutures. The loss in hard tissue volume may impair proper implant placement. GBR has been used to regenerate the lost alveolar ridge prior to or at the same time as dental implant placement. The most important factor for GBR success is graft stability. The periosteal mattress suture (PMS) stabilizing technique is an alternative to pins and screws to stabilize bone grafting material and has the advantage of not requiring the removal of the fixing devices. MATERIALS AND METHODS: A CBCT was acquired before and 6 months after surgery from six patients who underwent GBR with the PMS stabilizing technique. Images were analyzed for buccal bone thickness, area, and perimeter. RESULTS: The mean change in buccal bone thickness was 3.42 mm (± 1.31 SD) and proved statistically significant (P = .005). The mean change in bone crest area also proved statistically significant (P = .001). No significant difference was found in bone perimeter (P = .12). CONCLUSIONS: The PMS technique delivered optimal results without clinical complications. This study shows the potential of this technique as an alternative to pins or screws for graft stabilization in the esthetic zone.

Epidemiology of mid-buccal gingival recessions according to the 2018 Classification System in South America: Results from two population-based studies.

AIM: The aim of this investigation was to estimate the prevalence, severity and extent of mid-buccal gingival recessions (GRs; classified according to the 2018 Classification System) and to identify their risk indicators in the South American population. MATERIALS AND METHODS: Epidemiological data from two cross-sectional studies-performed on 1070 South American adolescents and 1456 Chilean adults-were obtained. All participants received a full-mouth periodontal examination by calibrated examiners. GR prevalence was defined as the presence of at least one mid-buccal GR ≥ 1 mm. GRs were also categorized into different recession types (RTs) according to the 2018 World Workshop Classification System. Analyses for RT risk indicators were also performed. All analyses were carried out at the participant level. RESULTS: The prevalence of mid-buccal GRs was 14.1% in South American adolescents and 90.9% in Chilean adults. In South American adolescents, the prevalence of RTs was 4.3% for RT1 GRs, 10.7% for RT2 GRs and 1.7% for RT3 GRs. In Chilean adults, the prevalence of RT1 GRs was 0.3%, while the prevalence of RT2 and RT3 GRs was 85.8% and 77.4%, respectively. Full-Mouth Bleeding Score (FMBS; <25%) was associated with the presence of RT1 GRs in adolescents. The risk indicators for RT2/RT3 GRs mainly overlapped with those for periodontitis. CONCLUSIONS: Mid-buccal GRs affected 14.1% of South American adolescents, whereas they affected most of the Chilean adult population (>90%). While RT1 GRs are more commonly observed in a non-representative cohort of South American adolescents (when compared to Chilean adults), the majority of Chilean adults exhibit RT2/RT3 GRs.

Dimensional changes after horizontal and vertical guided bone regeneration without membrane fixation using the retentive flap technique: A 1-year retrospective study.

AIM: To evaluate the dimensional changes after horizontal and vertical guided bone regeneration (GBR) without membrane fixation using the retentive flap technique. METHODS: This study retrospectively examined two cohorts that received vertical or horizontal ridge augmentations (VA or HA groups). GBR was performed using particulate bone substitutes and resorbable collagen membranes. The augmented sites were stabilized using the retentive flap technique without any additional membrane fixation. The augmented tissue dimensions were assessed using cone-beam computed tomography at preoperative, immediately postoperative (IP), 4 months (4M), and 1 year (1Y). RESULTS: Postoperative vertical bone gain in 11 participants of VA group amounted to 5.96 ± 1.88 mm at IP, which decreased to 5.53 ± 1.62 at 4M and to 5.26 ± 1.52 mm at 1Y (intragroup p < 0.05). The horizontal bone gain at IP in 12 participants amounted to 3.98 ± 2.06 mm, which decreased to 3.02 ± 2.06 at 4M and to 2.48 ± 2.09 mm at 1Y (intragroup p < 0.05). The mean implant dehiscence defect height after 1Y was 0.19 ± 0.50 mm in the VA group, and 0.57 ± 0.93 mm in the HA group. CONCLUSION: GBR without membrane fixation using the retentive flap technique seems to preserve the radiographic bone dimensions of vertically augmented sites. This technique may be less effective at preserving the width of the augmented tissue.

The L-shape technique in guided bone regeneration with simultaneous implant placement in the esthetic zone: A step-by-step protocol and a 2-14 year retrospective study.

OBJECTIVES: To describe the methodology of the "L-shape" technique in guided bone regeneration (GBR) with simultaneous implant placement and report on the clinical, esthetic, and patient satisfaction outcomes up to 14 years of follow-up. MATERIAL AND METHODS: Fourteen patients treated with the "L-shape" technique were included in this retrospective study. The L-shape technique was performed by trimming and placing a soft-type bone block made of deproteinized bovine bone mineral with 10% collagen at the buccal-occlusal aspect of the dental implant. The remaining gaps were filled with deproteinized bovine bone mineral granules and the augmented area was covered with a collagen membrane. The following parameters were recorded:  probing depth (PD), bleeding on probing (BOP), plaque index (PI), keratinized tissue width (KT) and marginal bone level (MBL). Esthetic outcomes were assessed according to the pink esthetic score (PES) and the white esthetic score (WES). Patient satisfaction was evaluated by means of a numerical rating scale (0-10). The stability of each augmented site was assessed by measuring the volumetric changes between baseline (crown delivery) and the respective follow-up. RESULTS: A total of 13 maxillary incisors and one maxillary canine in 14 patients were included. The mean follow-up period was 7.7 ± 3.8 years. PES values amounted to 10.7 ± 3.3 and WES to 8.8 ± 1.4. Patient satisfaction reached 9.4 ± 0.8. Mean PD at implant sites were 2.7 ± 0.7 mm while BOP amounted to 15.0 ± 0.2% and Pl to 5.0 ± 0.0%. Volumetric analyses revealed minimal changes at the augmented sites irrespective of the region of interest. Radiographic MBL remained relatively stable. CONCLUSIONS: Within the limitation of the present study the L-shape augmentation procedure seems to be a reliable technique when performing GBR with simultaneous implant placement in the esthetic zone. Outcomes encompassed stable clinical and esthetic results accompanied by high levels of patient satisfaction. Future randomized controlled trials are warranted to confirm possible benefits of the L-shape technique over traditional approaches. CLINICAL SIGNIFICANCE: The L-shape appears to be a simple yet promising technique in GBR with simultaneous implant placement that can easily be translated into clinical practice.

Effect of collagen membrane fixation on ridge volume stability and new bone formation following guided bone regeneration.

AIM: To test the effect of membrane fixation on ridge volume stability and new bone formation using guided bone regeneration. MATERIALS AND METHODS: In eight beagle dogs, after bilateral extraction of the maxillary pre-molars, a box-shaped defect was created on each side. All defect sites were augmented with a particulate bone substitute material, covered with either one of two non-cross-linked collagen membranes (CM1 or CM2) with or without fixation (-F or -UF). Samples were collected after 8 weeks. Histomorphometric and micro-computed tomography analyses were performed. RESULTS: Membrane fixation made no significant difference to the total augmented volume for both membranes (p > .05). Histological data indicated that at the ridge crest the augmented tissue width amounted to 2.4 ± 0.4 mm in the group CM1-F and 2.4 ± 0.5 mm in the group CM1-UF, with no significant difference between the groups. Conversely, in CM2-F the augmented tissue width was significantly larger than in CM2-UF (2.3 ± 0.1 vs. 1.57 ± 0.27, p < .05). CONCLUSIONS: Membrane fixation in contained defects failed to improve ridge volume stability regardless of the membrane type. However, it may enhance the width of the augmented ridge at the coronal portion depending on the type of membrane.

Vertical ridge augmentation feasibility using unfixed collagen membranes and particulate bone substitutes: A 1- to 7-year retrospective single-cohort observational study.

AIM: To determine whether vertical ridge augmentation (VRA) can be obtained through guided bone regeneration (GBR) using exclusively resorbable collagen membranes and particulate bone substitutes without additional stabilization. MATERIALS AND METHODS: This study retrospectively examined 22 participants who underwent VRA with staged or simultaneous implant placement. The vertical defects of all participants were filled with particulate bone substitutes and covered with resorbable collagen membranes. The augmented sites were stabilized with unfixed collagen membranes and the flap without any additional fixation. The augmented tissue height was assessed using cone-beam computed tomography at baseline, immediately after surgery, and at annual follow-ups. RESULTS: The vertical bone gain of the 22 augmented sites amounted to 6.48 ± 2.19 mm (mean ± SD) immediately after surgery and 5.78 ± 1.72 mm at 1- to 7-year follow-up. Of the 22 augmented sites, 18 exhibited changes of less than 1 mm, while the other 4 showed changes of greater than 1 mm. Histological observation of three representative cases revealed new bone apposition on the remaining material. CONCLUSION: The present findings indicate that GBR procedures using exclusively collagen membranes and particulate biomaterials without any additional fixation are feasible options for VRA.

Membrane fixation enhances guided bone regeneration in standardized calvarial defects: A pre-clinical study.

AIM: To determine whether collagen membrane (CM) fixation enhances guided bone regeneration in standardized defects. MATERIALS AND METHODS: Four 8-mm-diameter defects were surgically made in eight rabbit calvaria, and randomly allocated into four groups: control (empty), unfixed-CM, fixed-CM, and unfixed-CM with bone graft (BG + CM) (positive control). After 1- and 4-week healing periods, the animals were sacrificed and quantitative reverse transcription polymerase chain reaction, micro-computed tomography, and histological outcomes were assessed. RESULTS: At week 1, the expression levels of BMP-2, FGF-2, VEGF, and osteocalcin were significantly higher in the fixed-CM group than in the unfixed-CM and control groups (p < .05). Conversely, cathepsin-K was significantly expressed in the unfixed-CM group. No significant differences in expression markers were observed between the fixed-CM and BG + CM groups (p > .05). At week 4, new bone formation was significantly higher in the fixed-CM group than the unfixed-CM and control groups (p < .05), but similar to the BG + CM group (p > .05). CONCLUSIONS: CM fixation enhances the expression of osteogenic factors similar to BG + CM, leading to significantly more new bone formation. This suggests that the osteogenic potential is greater when membranes are fixed, thereby limiting the necessity of membrane-supporting materials to enhance bone formation.

Two short implants versus one short implant with a cantilever: 5-Year results of a randomized clinical trial.

AIM: To test whether or not the use of a short implant with a cantilever results in similar clinical and radiographic outcomes compared to two adjacent short implants with single tooth reconstructions. MATERIALS AND METHODS: Thirty-six patients with two adjacent missing teeth in the posterior region were randomly assigned to receive either a single 6-mm implant with a cantilever (ONE-C) or two 6-mm implants (TWO). Fixed reconstructions were inserted 3-6 months after implant placement and patients were re-examined up to 5 years (FU-5). RESULTS: A total of 26 patients were available for re-examination at FU-5. The survival rate amounted to 84.2% in ONE-C and to 80.4% in TWO (inter-group: p = .894). Technical complication rates amounted to 64.2% (ONE-C) and to 54.4% (TWO) (inter-group: p = 1.000). From baseline to FU-5, the median changes of the marginal bone levels were 0.13 mm in ONE-C and 0.05 mm in TWO (inter-group: p = .775). Probing depth, bleeding on probing, and plaque control record values showed no significant differences between the two treatment modalities (p > .05). CONCLUSIONS: Short implants with a cantilever render similar clinical and radiographic outcomes compared to two adjacent short implants at 5 years, however, they tend to fail at earlier time points suggesting an overload of the implants. Considering the modest survival rates, the clinical indication of either treatment option needs to be carefully evaluated. ClinicalTrials.gov (NCT01649531).

Osteoconductive properties of upside-down bilayer collagen membranes in rat calvarial defects.

BACKGROUND: Bilayer collagen membranes are routinely used in guided bone/tissue regeneration to serve as osteoconductive scaffolds and prevent the invasion of soft tissues. It is recommended to place the membranes with their dense layer towards the soft tissue and their porous layer towards the bony defect area. However, evidence supporting this recommendation is lacking. This study aimed to determine whether the alignment of bilayer collagen membranes has an effect on bone regeneration. METHODS: In two groups of ten male Sprague-Dawley rats each, a 5-mm calvarial defect was created. Thereafter, the defect was randomly covered with a bilayer, resorbable, pure type I and III collagen membrane placed either regularly or upside-down (i.e., dense layer towards bone defect). After 4 weeks of healing, micro-computed tomography (µCT), histology, and histomorphometry of the inner cylindrical region of interest (4.5 mm in diameter) were performed to assess new bone formation and the consolidation of the collagen membrane in the defect area. RESULTS: Quantitative µCT showed similar bone volume (median 8.0 mm3, interquartile range 7.0-10.0 vs. 6.2 mm3, 4.3-9.4, p = 0.06) and trabecular thickness (0.21 mm, 0.19-0.23 vs. 0.18 mm, 0.17-0.20, p = 0.03) between upside-down and regular placement, both leading to an almost complete bony coverage. Histomorphometry showed comparable new bone areas between the upside-down and regularly placed membranes, 3.9 mm2 (2.7-5.4) vs. 3.8 mm2 (2.2-4.0, p = 0.31), respectively. Both treatment groups revealed the same regeneration patterns and spatial distribution of bone with and without collagen fibers, as well as residual collagen fibers. CONCLUSIONS: Our data support the osteoconductive properties of collagen membranes and suggest that bone regeneration is facilitated regardless of membrane layer alignment.

Proteomic and genomic analysis of acid dentin lysate with focus on TGF-ß signaling.

Particulate autologous tooth roots are increasingly used for alveolar bone augmentation; however, the proteomic profile of acid dentin lysate and the respective cellular response have not been investigated. Here we show that TGF-ß1 is among the 226 proteins of acid dentin lysate (ADL) prepared from porcine teeth. RNA sequencing identified 231 strongly regulated genes when gingival fibroblasts were exposed to ADL. Out of these genes, about one third required activation of the TGF-ß receptor type I kinase including interleukin 11 (IL11) and NADPH oxidase 4 (NOX4). Reverse transcription-quantitative polymerase chain reaction and immunoassay confirmed the TGF-ß-dependent expression of IL11 and NOX4. The activation of canonical TGF-ß signaling by ADL was further confirmed by the phosphorylation of Smad3 and translocation of Smad2/3, using Western blot and immunofluorescence staining, respectively. Finally, we showed that TGF-ß activity released from dentin by acid lysis adsorbs to titanium and collagen membranes. These findings suggest that dentin particles are a rich source of TGF-ß causing a major response of gingival fibroblasts.

Acid Dentin Lysate Failed to Modulate Bone Formation in Rat Calvaria Defects.

Autogenous tooth roots are increasingly applied as a grafting material in alveolar bone augmentation. Since tooth roots undergo creeping substitution similar to bone grafts, it can be hypothesized that osteoclasts release the growth factors stored in the dentin thereby influencing bone formation. To test this hypothesis, collagen membranes were either soaked in acid dentin lysates (ADL) from extracted porcine teeth or serum-free medium followed by lyophilization. Thereafter, these membranes covered standardized 5-mm-diameter critical-size defects in calvarial bone on rats. After four weeks of healing, micro-computed tomography and histological analyses using undecalcified thin ground sections were performed. Micro-computed tomography of the inner 4.5 mm calvaria defects revealed a median bone defect coverage of 91% (CI: 87-95) in the ADL group and 94% (CI: 65-100) in the control group, without significant differences between the groups (intergroup p > 0.05). Furthermore, bone volume (BV) was similar between ADL group (5.7 mm3, CI: 3.4-7.1) and control group (5.7 mm3, CI: 2.9-9.7). Histomorphometry of the defect area confirmed these findings with bone area values amounting to 2.1 mm2 (CI: 1.2-2.6) in the ADL group and 2.0 mm2 (CI: 1.1-3.0) in the control group. Together, these data suggest that acid dentin lysate lyophilized onto collagen membranes failed to modulate the robust bone formation when placed onto calvarial defects.

Short communication: Cemented implant reconstructions are associated with less marginal bone loss than screw-retained reconstructions at 3 and 5 years of loading.

OBJECTIVES: To analyse whether there is a difference in marginal bone levels (MBL) and the respective changes between cemented and screw-retained reconstructions at 3 and 5 years of loading. METHODS: Radiographic data from 14 prospective multicentre clinical trials following implant loading with fixed cemented (CEM) or screw-retained (SCREW) reconstructions with a 3- to 5-year follow-up were retrieved from a database. MBL and MBL changes were assessed at initiation of implant loading (BL), at 3 (FU-3) and 5 years (FU-5) thereafter. The presence of peri-implantitis was also determined. RESULTS: Data from 1,672 implants at BL, 1,565 implants at FU-3 and 1,109 implants at FU-5 were available. The mean MBL amounted to 0.57 mm (SD 0.87) at BL, 0.55 mm (SD 0.86) at FU-3 and 0.65 mm (SD 1.18) at FU-5. At FU-3, the mean MBL was 0.44 mm (SD 0.65) in group CEM and 0.63 mm (SD 0.99) in group SCREW showing a significant difference between the groups (intergroup <0.05). At FU-5, the mean MBL was 0.42 mm (SD 0.77) in CEM and 0.80 mm (SD 1.37) in SCREW, again with significant differences between both groups (p < .05). MBL changes between BL and FU-3 amounted to 0.11 mm (SD 1.02) (bone loss) in SCREW and -0.17 mm (SD 1.03) (bone gain) in CEM. Similarly, mean MBL changes from BL to FU-5 amounted to 0.23 mm (SD 1.31) (bone loss) in SCREW and -0.26 mm (SD 1.27) (bone gain) in CEM. The prevalence of peri-implantitis amounted to 6.9% in CEM and 5.6% in group SCREW (intergroup p = .29063) at FU-3. At FU-5, peri-implantitis amounted to 4.6% in CEM and 6.2% in group SCREW (intergroup p = .28242). CONCLUSION: Cemented implant reconstructions compared with screw-retained reconstructions revealed higher marginal bone levels and similar rates of peri-implantitis during 5 years. The difference in MBL and the respective changes between the two groups, however, appear to be clinically negligible.