Minimal invasiveness in the alveolar ridge preservation, with or without concomitant implant placement.

The aim of this systematic review was to evaluate the benefit of ridge preservation (RP) with minimally invasive (MI) approaches with or without concomitant implant placement on morbidity, esthetics, and patient-related outcomes. Three Internet sources were used to search for appropriate papers. The search strategy was designed to include any clinical study published on RP with MI approaches such as flapless surgery, socket shield and socket sealing techniques and, use of biological agents. Characteristics of the individual studies, regarding methodological aspects, quantitative and qualitative data were extracted. The potential risk of bias was estimated, and the acquired evidence was graded. Independent screening of 860 reports resulted in 26 included original articles. Nine publications evaluated MI approaches for RP without concomitant implant placement. Eleven studies evaluated interventions for RP with immediate implant placement (IIP). Six studies compared RP with IIP vs RP without IIP. This systematic review found that MI approaches in most of the studies failed to improve clinical variables regarding morbidity, esthetics, and patient-related outcomes. Based on the limited number of studies analyzed and the methodological discrepancies observed, it is not possible to confirm that MI approaches promote a significant benefit when applied to RP procedures.

Tunnel technique with connective tissue graft versus coronally advanced flap with enamel matrix derivate for root coverage: 5-year results of an RCT using 3D digital measurement technology for volumetric comparison of soft tissue changes.

AIM: Comparison of the clinical efficacy (digitally volumetric, aesthetic, patient-centred outcomes) of tunnel technique (TUN) with subepithelial connective tissue graft (CTG) versus coronally advanced flap (CAF) with enamel matrix derivate (EMD) 5 years after gingival recession therapy. MATERIALS AND METHODS: In 18 patients contributing 36 RT1 recessions, study models were collected at baseline and follow-ups. Optical scans assessed recessions computer-assisted [recession depth, recession reduction (RECred), complete root coverage (CRC), percentage of root coverage (RC), pointwise (pTHK) and mean areal (aTHK) marginal soft tissue thickness]. Root coverage aesthetic Score (RES) was used for aesthetic evaluation and visual analogue scales for patient-centred data collection applied. RESULTS: Sixty months after surgery, 50.0% (TUN+CTG) and 0.0% (CAF+EMD) of sites showed CRC (p = 0.0118), 82.2% (TUN+CTG) and 32.0% (CAF+EMD) achieved RC, respectively (p = 0.0023). CTG achieved significantly better RECred (TUN+CTG: 1.75±0.74 mm; CAF+EMD: 0.50 ± 0.39 mm; p = 0.0009) and aTHK (TUN+CTG: 0.95 ± 0.41 mm; CAF+EMD: 0.26 ± 0.28 mm; p = 0.0013). RES showed superior outcomes (p = 0.0533) for TUN+CTG (6.86 ± 2.31) compared to CAF+EMD (4.63 ± 1.99). The study failed to find significant differences related to patient-centred outcomes (TUN+CTG: 8.30 ± 2.21; CAF+EMD: 7.50 ± 1.51; p = 0.1136). CONCLUSIONS: Five years after treatment, CTG resulted in better clinical and aesthetic outcomes than CAF+EMD. Increased THK was associated with improved outcomes for RECred and RC.

Tunnel technique with connective tissue graft versus coronally advanced flap with enamel matrix derivate for root coverage: 2-year results of an RCT using 3D digital measuring for volumetric comparison of gingival dimensions.

AIM: The aim of this randomized clinical trial was to compare clinical and volumetric outcomes of tunnel technique (TUN) with subepithelial connective tissue graft (CTG) versus coronally advanced flap (CAF) with enamel matrix derivate (EMD) 2 years after gingival recession (GR) treatment. MATERIALS AND METHODS: Twenty-three patients contributed 45 Miller class I or II GR. At baseline and follow-up examinations, study models were collected. Their three-dimensional scans allowed precise computer-assisted measurement of recession depth (REC), complete root coverage (CRC), percentage of root coverage (RC), pointwise (pTHK) and mean areal (aTHK) marginal soft tissue thickness. Clinical examination delivered probing depths (PPD) and height of keratinized tissue. RESULTS: 24 months after surgery, digitally evaluated CRC was present in 60.0% of the TUN + CTG and 0.0% of the CAF + EMD-treated sites (p < .0001), meaning a certain relapse of the gingival margin ragarding both approaches. RC amounted to 94.0% (TUN + CTG) and 57.3% (CAF + EMD), respectively (p < .0001). REC reduction (RECred) was significantly higher for TUN + CTG (1.81 ± 0.56 mm) than for CAF + EMD (0.90 ± 0.45 mm) (p < .0001). pTHK and aTHK values were significantly greater in the TUN + CTG group (1.41 ± 0.35 mm and 1.11 ± 0.26 mm) than in the CAF + EMD group (0.78 ± 0.32 mm and 0.60 ± 0.26 mm) (p < .0001). Statistical analysis detected positive correlations between THK and both RC and RECred (p < .001). CONCLUSIONS: Two years post-operatively, CTG showed better clinical and volumetric outcomes than EMD. Increased THK values were associated with improved outcomes regarding RC and RECred.

Surgery without papilla incision: tunneling flap procedures in plastic periodontal and implant surgery.

Diverse clinical advancements, together with some relevant technical innovations, have led to an increase in popularity of tunneling flap procedures in plastic periodontal and implant surgery in the recent past. This trend is further promoted by the fact that these techniques have lately been introduced to a considerably expanded range of indications. While originally described for the treatment of gingival recession-type defects, tunneling flap procedures may now be applied successfully in a variety of clinical situations in which augmentation of the soft tissues is indicated in the esthetic zone. Potential clinical scenarios include surgical thickening of thin buccal gingiva or peri-implant mucosa, alveolar ridge/socket preservation and implant second-stage surgery, as well as soft-tissue ridge augmentation or pontic site development. In this way, tunneling flap procedures developed from a technique, originally merely intended for surgical root coverage, into a capacious surgical conception in plastic periodontal and implant surgery. The purpose of this article is to provide a comprehensive overview on tunneling flap procedures, to introduce the successive development of the approach along with underlying ideas on surgical wound healing and to present contemporary clinical scenarios in step-by-step photograph-illustrated sequences, which aim to provide clinicians with guidance to help them integrate tunneling flap procedures into their daily clinical routine.

Porcine dermal matrix in the treatment of dehiscence-type defects--an experimental split-mouth animal trial.

OBJECTIVES: To describe histometrical outcomes (tissue thickness, tissue height) of a porcine dermal matrix (PDX) and subepithelial connective tissue (CTG) in the treatment of dehiscence-type defects. MATERIAL AND METHODS: In five beagle dogs buccal dehiscence defects were created on both upper canines. The defects were covered in a split-mouth design either with a porcine dermal matrix or subepithelial connective tissue. After 4 months histometrical outcomes were evaluated using a nonparametric Brunner-Langer model. RESULTS: Neither in the test nor in the control specimen signs of inflammation or foreign body reaction was detected. Histometrically, no significant difference was found for tissue thickness and height between both treatment groups. CONCLUSIONS: Porcine dermal matrix can be used for grafting of dehiscence-type defects. Augmentation of tissue thickness seems to be comparable to subepithelial connective tissue.

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.

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.

Bone loss after full-thickness and partial-thickness flap elevation.

OBJECTIVES: the aim of this study was to histologically assess whether elevation of partial-thickness flaps results in reduced bone alterations, as compared with full-thickness flap preparations. MATERIAL AND METHODS: in five beagle dogs, both mandibular second premolars (split-mouth design) were subjected to one of the following treatments: Tx1: elevation of a partial-thickness flap over the mesial root of P(2) and performing a notch at the height of the bone. Tx2: elevation of a full-thickness flap over the mesial root of P(2) and performing a notch at the height of the bone. After 4 months, sections were evaluated for: (i) vertical bone loss and (ii) osteoclastic activity using histometry. RESULTS: elevation of both full- and partial-thickness flaps results in bone loss and elevated osteoclastic activity. Partial-thickness flaps can result in less bone loss than full-thickness flaps, but are subject to some variability. CONCLUSION: use of partial-thickness flaps does not prevent from all bone loss. The procedure may result most of the times in less bone loss than the elevation of full-thickness flaps. Further research has to evaluate the determinants of effective outcomes of partial-thickness flap procedures.

Local tolerance and efficiency of two prototype collagen matrices to increase the width of keratinized tissue.

AIM: to evaluate the local tolerance and efficiency of two experimental collagen matrices to increase the width of keratinized tissue. METHODS: in 12 pigs, two apically positioned flaps were prepared on both sides of the mandible. The denuded defect areas were randomly covered with one of two experimental porcine-derived collagen matrices (M1; M2). The other defect area was left untreated (control). At 1 and 6 months, clinical measurements for the width and thickness of the keratinized tissue were recorded. At 6 months, all animals were sacrificed. Descriptive and semi-quantitative histologic analyses were performed. For statistical analysis, the Kruskal-Wallis test and the Mac Nemar test were applied. RESULTS: the collagen matrices integrated well into the surrounding tissue without any signs of inflammation. The thickness and width of the keratinized tissue increased significantly over 6 months in all the groups, resulting in slightly more favourable results for M1 (compared with M2) with respect to the thickness and for M2 (compared with M1) with respect to the width of keratinized tissue. No statistically significant differences were observed for any of the evaluated clinical and histologic parameters among the three treatment modalities. CONCLUSIONS: within the limits of this animal study, the prototype collagen matrices can be used safely to increase the width of keratinized tissue.

The socket-shield technique: a proof-of-principle report.

AIM: Clinical studies have suggested that retaining roots of hopeless teeth may avoid tissue alterations after tooth extraction. Therefore, the objective of this proof-of-principle experiment was to histologically assess a partial root retention (socket-shield technique) in combination with immediate implant placement. MATERIAL AND METHODS: In one beagle dog, the third and fourth mandibular pre-molar were hemisected and the buccal fragment of the distal root was retained approximately 1 mm coronal to the buccal bone plate. Following application of enamel matrix derivate, a titanium implant was placed lingual to that tooth fragment either with or without contact to the buccal tooth fragment and a healing abutment was connected. Four months after implant placement, histological evaluation, and backscatter scanning electron microscopy were performed. RESULTS: All four implants were osseointegrated without any histologic inflammatory reaction and the tooth fragment was devoid of any resorptional processes. On the buccal side, the tooth fragment was attached to the buccal bone plate by a physiologic periodontal ligament. On the lingual side of the fragment, newly formed cementum could be detected. In the areas where the implant was placed into the fragment, newly formed cementum was demonstrated directly on the implant surface. CONCLUSIONS: Retaining the buccal aspect of the root during implant placement does not appear to interfere with osseointegration and may be beneficial in preserving the buccal bone plate.

Peri-implant bone level around implants with platform-switched abutments.

PURPOSE: The purpose of this clinical trial was to evaluate whether the crestal bone height around dental implants could be influenced by the use of a platform-switching protocol. MATERIALS AND METHODS: All implants placed in the year 2006 in healed bone without any need for ridge augmentation were included in this study. The following groups were created: (1) wide-diameter implants were placed subcrestally and regular-diameter cover screws were connected; (2) regular-diameter implants were placed at the crest and regular-diameter cover screws were connected. Standardized radiographs were obtained after insertion of the definitive prosthesis and after 1 year. Calibrated measurements were conducted initiating from the mesial and distal bone peaks to the implant-abutment junction. The average value of the mean medial and mean distal values was calculated and analyzed with an unpaired two-tailed t test. P values < .05 were regarded as statistically significant. RESULTS: In all, 89 dental implants in 36 patients were evaluated. The implants with a platform-switched configuration (n = 75) exhibited statistically significantly less bone loss at time of insertion of the definitive prosthesis (0.30 +/- 0.07 mm versus 0.68 +/- 0.17 mm; P < .05) and at 1 year (0.39 +/- 0.07 mm versus 1.00 +/- 0.22 mm, P < .01) when compared to the nonplatform-switched implants (n = 14). CONCLUSION: Platform-switched implants seem to limit crestal bone remodeling.

Stage-two implant surgery in the esthetic zone: a new technique.

The esthetic outcome of implant-supported restorations has become increasingly important, especially for single-tooth implants in the esthetic zone. Because of the morphologic alterations that occur following tooth extraction, augmentation procedures are often necessary before, during, or after implantation to achieve an esthetically pleasing result. This article describes a modified technique for augmenting the soft tissue during stage-two implant surgery. The technique uses a modified roll flap, in combination with a tunneling approach to the adjacent teeth and a coronally positioned palatal sliding flap, to achieve sufficient horizontal dimensions and a scarless and harmonious architecture of the peri-implant soft tissue.

Hard tissue alterations after socket preservation with additional buccal overbuilding: a study in the beagle dog.

OBJECTIVES: The aim of this study was to histometrically assess alterations of the ridge following socket preservation alone and socket preservation with additional buccal overbuilding. MATERIAL AND METHODS: In five beagle dogs four extraction sites were randomly subjected to one of the following treatments: Tx 1: The socket was filled with BioOss Collagen and covered with a free gingival graft from the palate. Tx 2: The buccal bone plate was augmented using the GBR-technique, the socket was filled with BioOss Collagen and covered with a free gingival graft. Tx 3: The buccal bone plate was forced into a buccal direction using a manual bone spreader. The socket was filled with BioOss Collagen and covered with a free gingival graft from the palate. Tx 4: The socket was filled with BioOss Collagen and a combined free gingival/connective tissue graft was used to cover the socket and for buccal tissue augmentation. For each experimental site, two histological sections were subjected to histometric analysis and evaluated for (i) vertical bone dimensions and (ii) horizontal bone dimensions. RESULTS: All treatment groups showed horizontal and vertical bone loss. The mean vertical bone loss of the buccal bone plate was significantly lower in Tx 4 than in the other groups, while no statistical significant differences could be detected among the groups in the horizontal dimension. CONCLUSION: Overbuilding the buccal aspect in combination with socket preservation does not seem to be a suitable technique to compensate for the alterations after tooth extraction.

Dimensional changes of the ridge contour after socket preservation and buccal overbuilding: an animal study.

OBJECTIVES: The aim of the study was to volumetrically assess alterations of the ridge contour after socket preservation and buccal overbuilding. MATERIAL AND METHODS: In five beagle dogs, four extraction sites were subjected to one of the following treatments: Tx 1: The socket was filled with BioOss Collagen and covered with a free gingival autograft from the palate (SP). Tx 2: The buccal bone plate was forced into a buccal direction using a manual bone spreader and SP was performed. Tx 3: The buccal bone plate was forced into a buccal direction using a manual bone spreader; SP was performed. Tx 4: The socket was filled with BioOss Collagen and a combined free gingival/connective tissue graft was used to cover the socket and for buccal tissue augmentation. Impressions were obtained at baseline, 2 weeks and 4 months post-operatively. Casts were optically scanned and superimposed in one common coordinate system. Using digital image analysis, the volumetric differences per area among the different treatment time points and among the treatment groups were calculated. RESULTS: Four months after tooth extraction, no statistically significant differences with regard to the buccal volume per area could be assessed among the treatment groups. CONCLUSION: Overbuilding the buccal aspect in combination with socket preservation is not a suitable technique to compensate for the alterations after tooth extraction.

The effects of recombinant human growth/differentiation factor-5 (rhGDF-5) on bone regeneration around titanium dental implants in barrier membrane-protected defects: a pilot study in the mandible of beagle dogs.

PURPOSE: This dog study sought to evaluate guided bone regeneration (GBR) in peri-implant defects following implantation of beta-tricalcium phosphate (beta-TCP) with and without osteoinductive recombinant human growth/differentiation factor-5 (rhGDF-5). MATERIALS AND METHODS: In five beagle dogs, all mandibular premolars and the first molar were extracted. After 2 months, six buccolingual critical-size defects were created, and an implant was inserted into the center of each defect. One defect was filled with beta-TCP coated with rhGDF-5 (600 microg/g beta-TCP) and covered with a titanium-reinforced e-PTFE membrane (GDF group). A second defect received the same treatment, but pure uncoated beta-TCP was used (TCP group). A third defect was filled with beta-TCP mixed with autograft and not protected with a membrane (control group). The remaining three defects were filled with other biomaterials. After 2 months, total new bone area, regenerated bone height, and residual amount of beta-TCP were determined histomorphometrically. RESULTS: All implants osseointegrated. One membrane in each group became exposed. Mean new bone area for GDF, TCP, and control sites was 43.9 +/- 18.7 mm2, 32.3 +/- 16.1 mm2, and 13.1 +/- 4.0 mm2, respectively, with a significant difference between GDF and control groups. Mean regenerated bone height was 103.8 +/- 29.7%, 75.4 +/- 36.6%, and 67.2 +/- 19.1% for the GDF, TCP, and control groups, respectively. Mean residual matrix volumes were 25.9 +/- 13.6%, 30.0 +/- 13.0%, and 13.4 +/- 6.5%, respectively. Membrane protection of peri-implant defects filled with beta-TCP resulted in a stronger effect on bone regeneration, although this was not statistically significant. The most pronounced regenerative results were achieved in rhGDF-5/beta-TCP filled membrane-protected defects. CONCLUSION: Delivery of rhGDF-5 on beta-TCP might have the potential to enhance the results of GBR in peri-implant defects.

Dimensional changes of the alveolar ridge contour after different socket preservation techniques.

OBJECTIVES: The aim of the following study was to assess contour changes after socket preservation techniques. MATERIAL AND METHODS: In five beagle dogs, the distal root of the third and fourth mandibular premolars was extracted. The following treatments (Tx) were randomly assigned for the extraction socket. Tx 1: BioOss Collagen. Tx 2: BioOss Collagen and a free soft tissue graft. Tx 3: No treatment. Tx 4: The internal buccal aspect was covered with an experimental collagen membrane, the extraction socket was filled with BioOss Collagen and the membrane folded on top of the graft. Impressions were obtained at baseline, 2 and 4 months after surgery. Bucco-lingual measurements were performed using digital imaging analysis. RESULTS: All groups displayed contour shrinkage at the buccal aspect. Only the differences between the two test groups (Tx 1, Tx 2) and the control group (Tx 3) were significant at the buccal aspect (p< or =0.001). No measurements of the Tx 4 group could be performed. CONCLUSION: Socket preservation techniques, used in the present experiment, were not able to entirely compensate for the alterations after tooth extraction. Yet, incorporation of BioOss Collagen seems to have the potential to limit but not avoid the post-operative contour shrinkage.

Covering of gingival recessions with a modified microsurgical tunnel technique: case report.

Recent advances in periodontal plastic surgery have encouraged reassessment of the envelope technique and its modified version, the tunnel technique, for root coverage. This article describes alterations in the technique-sensitive tunnel approach, which include an undermining split flap preparation of the buccal tissues with newly developed instruments to minimize trauma and ensure a better blood supply for the connective tissue graft. The use of a microsurgical concept, including microsurgical blades and suture material, improves wound healing and establishes a better esthetic result. Because these modifications simplify the tunnel approach, the spectrum of indications for the tunnel technique may be expanded and a broader application achieved.

A prospective multicenter clinical trial of 3i machined-surface implants: results after 6 years of follow-up.

PURPOSE: In this prospective multicenter clinical study, 1,179 3i standard threaded and self-tapping implants were followed for up to 6 years and monitored according to established success criteria. MATERIALS AND METHODS: A total of 493 patients (240 men and 253 women) with a mean age of 45.1 years at implant surgery were enrolled at 6 research centers after being screened for exclusion criteria. Implants were placed according to a 2-stage surgical protocol with a minimum of 4 months of submerged healing in the mandible and 6 months in the maxilla. Restorations included 633 prostheses, the majority of which were fixed partial dentures in the posterior mandible or maxilla or single-tooth replacements in the anterior maxilla. RESULTS: One hundred four implants (8.8%) did not meet success criteria and were designated as failures, and 222 implants (18.8%) were lost to follow-up. The cumulative success rate according to life table methods was 91.1% at 6 years. DISCUSSION: Sixty percent of the failed implants were short (< or = 10 mm long), and their cumulative success rate as a group at 6 years was 89.0%, compared to 93.1% for longer implants (P < .05). Thirty-three percent of all failures were implants placed in the posterior maxilla, for a 5-year cumulative success rate of 87.4%. CONCLUSION: It appears that limited bone dimensions and poor-quality bone have an impact on the performance of these machined-surface implants.

Distraction osteogenesis: a treatment tool to improve baseline conditions for esthetic restorations on immediately placed dental implants--a case report.

Replacement of two adjacent teeth in an anterior maxilla with deficient hard and soft tissues appears to be the utmost challenge in implant dentistry in the esthetic zone. In this case report, baseline conditions for implant placement were improved by alveolar distraction to enhance hard and soft tissues around the maxillary central incisors. Three months after the active phase of distraction, the roots of the central incisors were extracted and two screw-type dental implants were immediately placed into the extraction sockets. For immediate provisionalization, acrylic resin crowns were fabricated on UCLA abutments, providing the ideal emergence profile to support the periimplant soft tissue. Six months after implant placement, the prosthetic restoration of the case was finished with ceramic crowns cemented to individually fabricated zirconium oxide abutments. The described treatment strategy appears to have a great potential to restore natural esthetics in cases with major tissue deficiencies in the esthetic zone.

[Bioresorbable barrier membranes for guided bone regeneration around dental implants]. / Bioresorbierbare Membranbarrieren für die geführte Knochenregeneration um dentale Implantate. Eine Pilotuntersuchung am Beagle-Hund.

The aim of this study was to evaluate the efficacy of two bioresorbable barriers especially produced for guided bone regeneration. Six beagle dogs were used in this investigation. At the beginning of the study, all mandibular premolars were extracted and after a healing period of three months three screw-type machined implants were inserted in each side of the mandible. At the buccal aspect of each implant bed a dehiscence type defect with a coronoapical and mesiodistal extension of 5 mm was created. Then, one of the following four methods for defect treatment was applied: 1) guided bone regeneration (GBR) with a bioresorbable barrier (poly-L/DL-lactide) (test group 1), 2) GBR with a bioresorbable composite barrier [poly-L/DL-lactide reinforced with tricalciumphosphate (TCP)] (test group 2), 3) GBR with an expanded polytetrafluoroethylene barrier (GTAM) (control group 1), and 4) no treatment (control group 2). The animals were sacrificed six months after implant installation. During the healing period the most common problems encountered in the test groups 1 and 2 were soft tissue dehiscences and bioresorbable membrane exposures. Retrieved tissue specimens were processed for histological and histometric evaluation. The mean amount of vertical bone regeneration at the defect areas was 1.75 mm for test group 1, 1.82 mm for the test group 2, 2.38 mm for control group 1, and 1.93 mm for control group 2. When the amount of bone regeneration in contact to the implant surface was evaluated, the regeneration result was 1.45 mm for test group 1, 1.49 mm for test group 2, 2.08 mm for control group 1, and 0.91 mm for control group 2. For both measurements, no statistically significant differences could be observed between the different groups. The present animal experiment showed that the treatment of dehiscence type defects around machined implants with the two bioresorbable barriers showed only slightly superior results compared to the treatment without barriers (control group 2). The best results--although not statistically significant different from the other treatment groups--were obtained when nonresorbable barriers were used.