Otto Zuhr

Peri-Implant Bone Level Around Implants With Platform-Switched Abutments: Preliminary Data From a Prospective Study

PURPOSE Several long-term clinical studies have shown a mean marginal bone loss around dental implants of 1.5 to 2 mm in the first year after prosthetic restoration. Currently, concepts to avoid bone remodeling around dental implants have been developed. The use of prosthetic abutments with reduced width in relation to the implant diameter (platform switching) seems to have the greatest potential to limit the crestal resorption. The purpose of this clinical trial was to show that crestal bone height around dental implants could be influenced using a platform switch protocol and that the bone level would remain stable within 1 year after final prosthetic reconstruction. MATERIALS AND METHODS Fifteen patients were treated with fixed implant retained prosthesis; 14 wide-diameter implants were supplied with platform-switched abutments and served as the test group. Eight implants with regular diameter were reconstructed with traditional abutments and served as the control group. Standardized digital radiographs were obtained for evaluation of the peri-implant bone levels at the time of installation of the final restoration and at 1-year follow-up. Marginal peri-implant bone levels were measured at the mesial and distal surfaces of each implant using digital image analysis. RESULTS The mean values of crestal bone height at baseline were -0.09 mm +/- 0.65 mm for the platform-switched implants and -1.73 mm +/- 0.46 mm for the nonplatform-switched implants. One year after final restoration, the mean value of crestal bone height was -0.22 mm +/- 0.53 mm for the test group and -2.02 mm +/- 0.49 mm for the control group. When tested with statistical means, the differences were significant for baseline and for follow-up (P </= .0001). Mean bone level change from baseline to 1-year follow-up was -0.12 mm +/- 0.40 mm for the test group and -0.29 mm +/- 0.34 mm, respectively, for the control group. On analysis using ANCOVA, this difference was shown to be significant (P </= .0132). CONCLUSION The concept of platform switching appears to limit crestal resorption and seems to preserve peri-implant bone levels. A certain amount of bone remodeling 1 year after final reconstruction occurs, but significant differences concerning the peri-implant bone height compared with the nonplatform-switched abutments are still evident 1 year after final restoration. The reduction of the abutment of 0.45 mm on each side (5 mm implant/4.1 mm abutment) seems sufficient to avoid peri-implant bone loss.

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.

Hard tissue alterations after socket preservation: an experimental study in the beagle dog

OBJECTIVES The aim of the following experimental study was to assess bone changes in the horizontal and vertical dimension when using different socket preservation procedures. MATERIAL AND METHODS In five beagle dogs the distal roots of the 3rd and 4th premolar were extracted without elevation of a mucoperiosteal flap and the following treatments were assigned: Tx 1: The extraction socket was filled with BioOss Collagen (Geistlich Biomaterials, Wolhusen, Switzerland) and interrupted sutures were applied.: Tx 2: The extraction socket was filled with BioOss Collagen (Geistlich Biomaterials, Wolhusen, Switzerland) and a free gingival graft was sutured to cover the socket.: Tx 3: The extraction socket was left with its blood clot and interrupted sututes were applied.: Four month after surgery the dogs were sacrificed and from each extraction site two histological sections were selected for histometric analysis. The following parameters were evaluated: (1) the vertical dimension was determined by placing a horizontal line on the lingual bone wall. Then, the distance from this line to the buccal bone wall was measured. (2) The horizontal dimension was assessed at three different areas measured from the top of the lingual crest: 1 mm (Value 1), 3 mm (Value 3) and 5 mm (Value 5). RESULTS The mean vertical loss of the buccal bone plate for the Tx 1 group was 2.8+/-0.2 mm. The Tx 2 group showed vertical loss of 3.3+/-0.2 mm. The Tx 3 group demonstrated 3.2+/-0.2 mm of mean vertical loss. The horizontal dimension of the alveolar process was 4.4+/-0.3/6.1+/-0.2/7.2+/-0.1 mm at the three different levels for the Tx 1 group. The Tx 2 group depicted bone dimensions of 4.8+/-0.2/6.0+/-0.2/7.1+/-0.1 mm. The horizontal dimension of the Tx 3 group was 3.7+/-0.3/6.2+/-0.2/7.0+/-0.1 mm. When the results from the horizontal measurements were tested with the analysis of variance (ANOVA), a clear significance could be found in particular for Value 1 mm between the test groups Tx 1 and Tx 2 and the control group (Tx 3) (P<0.001). Furthermore the mean of treatment 1 (Tx 1) was slightly significantly lower than of treatment 2 (Tx 2) (P<0.05). CONCLUSION The findings from the present study disclose that incorporation of BioOss Collagen into the extraction socket has only limited impact on the subsequent biologic process with particular respect to the buccal bone plate. The horizontal measurement of the alveolar ridge depicted that the loss of the buccal bone plate was replaced to a certain amount by newly generated bone guided by the BioOss Collagen scaffold. It seems that the mechanical stability provided by BioOss Collagen and furthermore by a free gingival graft could act as a placeholder preventing the soft tissue from collapsing.

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.

The addition of soft tissue replacement grafts in plastic periodontal and implant surgery: critical elements in design and execution

Soft tissue replacement grafts have become a substantial element to increase tissue volume in plastic periodontal and implant surgery. Autogenous subepithelial connective tissue grafts are increasingly applied in aesthetic indications like soft tissue thickening, recession treatment, ridge preservation, soft tissue ridge augmentation and papilla re-construction. For the clinical performance of connective tissue graft harvesting and transplantation, a fundamental understanding of the anatomy at the donor sites and a sound knowledge of tissue integration and re-vascularization processes are required. Possible donor sites are the anterior and posterior palate including the maxillary tuberosity, providing grafts of distinct geometric shape and histologic composition. The selective clinical application of different grafts depends on the amount of required tissue, the indication and the personal preference of the treating surgeon. One of the main future challenges is to volumetrically evaluate and compare the efficacy and long-term stability of soft tissue autografts and their prospective substitutes. The aim of this review was to discuss the advantages and shortfalls of different donor sites, substitute materials and harvesting techniques. Although standardized recommendations regarding treatment choice and execution can hardly be given, guidelines for predictable and successful treatment outcomes are provided based on clinical experience and the available scientific data.

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.

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.

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.

Experimental Peri‐Implantitis around Different Types of Implants – A Clinical and Radiographic Study in Dogs

BACKGROUND The influence of the implant micro and macrostructure on peri-implantitis is not fully understood. PURPOSE To determine the effect of ligature-induced peri-implantitis on three commercially available implant types. MATERIALS AND METHODS Five beagle dogs were used. Two months following tooth extraction, three different implant types (BIOMET 3i T3, BIOMET 3i, Palm Beach Gardens, FL, USA; Straumann Bone Level, Straumann GmbH, Basel, Switzerland; Nobel Replace Tapered, Nobel Biocare, Gothenburg, Sweden) were placed in a randomized fashion in each hemi-mandible. Peri-implantitis was initiated by ligature placement and soft diet. Ligatures were added every 2 weeks for a total of four ligature advancements. After 2 weeks, the ligatures were removed, oral hygiene measures initiated for 3 weeks, and clinical (probing depth, mucosal recession, bleeding on probing), intrasurgical (intrasurgical defect depth, intrasurgical defect width), and radiographic (radiographic bone level) parameters assessed. RESULTS Nobel Replace Tapered implants showed significantly higher intrasurgical defect depth, intrasurgical defect width, probing depths, and radiographic bone level when compared to BIOMET 3i T3 or Straumann Bone Level implants. Straumann Bone Level implants showed largely similar clinical outcomes to BIOMET 3i T3. No significant differences between the groups were observed for mean mucosal recession. CONCLUSION In an experimental peri-implantitis model, Nobel Replace Tapered implants are associated with pronounced tissue loss.

Xenogenic collagen matrix or autologous connective tissue graft as adjunct to coronally advanced flaps for coverage of multiple adjacent gingival recession: Randomized trial assessing non-inferiority in root coverage and superiority in oral health-related quality of life

Abstract Aim To evaluate the non‐inferiority of the adjunct of a xenogeneic collagen matrix (CMX) or connective tissue graft (CTG) to coronally advanced flaps (CAF) for coverage of multiple adjacent recessions and compare superiority in patient‐reported outcomes (PROM). Material and methods One hundred and eighty‐seven subjects (92 CMX) with 485 recessions in 14 centres were randomized and followed up for 6 months. Patients filled daily diaries for 15 days to monitor patient‐reported experience. The primary outcome was changed in position of the gingival margin. Multilevel analysis used centre, subject and tooth as levels and baseline parameters as covariates. Results Average baseline recession was 2.5 ± 1.0 mm. The surgery was 15.7 min shorter (95%CI from 11.9 to 19.6, p < .0001) and perceived lighter (11.9 VAS units, 95%CI from 4.6 to 19.1, p = .0014) in CMX subjects. Time to recovery was 1.8 days shorter in CMX. Six‐month root coverage was 1.7 ± 1.1 mm for CMX and 2.1 ± 1.0 mm for CTG (difference of 0.44 mm, 95%CI from 0.25 to 0.63 mm). The upper limit of the confidence interval was over the non‐inferiority margin of 0.25 mm. Odds of complete root coverage were significantly higher for CTG (OR = 4.0, 95% CI 1.8–8.8). Conclusion Replacing CTG with CMX shortens time to recovery and decreases morbidity, but the tested generation of devices is probably inferior to autologous CTG in terms of root coverage. Significant variability in PROMs was observed among centres.