Osteogenic potential of mesenchymal cells embedded in the provisional matrix after a 6-week healing period in augmented and non-augmented extraction sockets: an immunohistochemical prospective pilot study in humans.

PURPOSE: The aim of the present clinical study was the evaluation of the osteogenic potential of mesenchymal cells embedded in the provisional matrix of non-augmented and with Bio-Oss collagen-augmented human extraction sockets after 6 weeks of healing time. METHODS: Twenty-five patients with 47 extraction sites participated in the present study. After tooth removal, the extraction sockets were augmented with Bio-Oss collagen or not augmented. At implant placement, bone biopsies of the extraction sockets were obtained. The immunohistochemical analysis of the osteogenic potential of the mesenchymal cells in the provisional matrix was performed using three monoclonal antibodies: core-binding factor α1 (Cbfa1)/runt-related protein (Runx)2, osteonectin (OSN/secreted protein acidic and rich in cyst [SPARC]) and osteocalcin (OC). The statistical analysis was performed using two-factorial analysis for repeated measures, Mann-Whitney U-test and Spearman's rank-order correlation coefficient. RESULTS: Of 47 extraction sockets examined, 17 sockets demonstrated an almost complete ossification. Hence, the provisional matrix of the 30 remaining extraction sockets (21 non-augmented, 9 augmented) was immunohistochemically investigated. No evidence of acute or chronic inflammation was noted in any of the specimens. In the provisional matrix of the non-grafted socket, the median amount of Cbfa1/Runx2-positive cells was 72.3%, of OSN (SPARC) 66.9% and of OC 23.4%, whereas in the grafted sockets the median rate of immunopositive cells staining with Cbfa1/Runx2 was 73.3%, of OSN (SPARC) 61.4% and of OC 20.1%. There was no significant difference in the proportion of positive cells expressed by Cbfa1/Runx2, OSN/SPARC and OC between the grafted and non-grafted socket. Furthermore, the cell density did not correlate to the quantity of stained cells independent of the used proteins. DISCUSSION: After a 6-week healing period, the provisional matrix was demonstrated to have a high proportion of cells displaying a maturation of mature osteoprogenitor cells to osteoblasts. The grafting procedure did not influence the quantity of osteogenic cells in the extraction socket.

Rehabilitation of irradiated patients with modified and conventional sandblasted acid-etched implants: preliminary results of a split-mouth study.

PURPOSE: The aim of this study was to evaluate the success rate of chemically modified and conventional sandblasted acid-etched surface (SLA) titanium implants in irradiated oral squamous cell carcinoma patients. MATERIAL AND METHODS: Twenty patients with a mean age of 61.1 years were treated with dental implants after ablative surgery and radio-chemotherapy of oral cancer. All patients were non-smokers. The placement of SLA and modSLA implants was performed bilaterally according to a split-mouth design. All 102 implants (50 SLA, 52 modSLA) placed showed an unloaded healing time of 6 weeks in the mandible and 10 weeks in the maxilla. Mean crestal bone changes using standardized orthopantomographies and clinical parameters like pocket depths, mPII and mBI were evaluated. RESULTS: Of 102 implants, 55 implants (27 SLA implants, 28 modSLA) were located in the maxilla and 47 implants (23 SLA, 24 modSLA) in the mandible. The average observation period was 14.4 months. The amount of bone loss at the implant shoulder of SLA implants was 0.4 mm mesial and 0.4 mm distal. The modSLA implants displayed a bone loss of mesial 0.3 mm and distal 0.3 mm. Two SLA implants were lost resulting in a success rate of 96%. The success rate of modSLA implants was 100%. CONCLUSION: Regarding the data found in this investigation, we can conclude that implants with chemically modified and conventional SLA titanium surface show high success rates in irradiated patients. SLA implants with or without a chemically modified surface regardless of the location can be restored with a high predictability of success at least in the short time range observed.

Effect of dehiscences to the bone response of implants with an Acid-etched surface: an experimental study in miniature pigs.

Spontaneous early exposure of submerged implants during the healing phase as a factor for early crestal bone loss around the implants is still being controversially discussed. The aim of this study was to examine the potential impact of dehiscences on the osseointegration process of acid-etched dental implants with a shortened healing period in the maxilla. Five animals received a total of 15 titanium implants 8 weeks postextraction. Eight of these implants were placed in the maxilla to osseointegrate within a shortened healing period of 3 months, whereas the remaining implants were inserted in the lower jaw and served as controls with a regular healing time. Polyfluorochrome sequential labeling with xylenol orange, calcein green, and alizarin complexone was performed 2, 5, and 8 weeks after implant placement. After 12 weeks of unloaded and submerged healing, the animals were killed and the implants removed en bloc. After the processing of the undecalcified PMMA-embedded samples, thin ground sections (40-60 µm) were made. The histomorphometric determination of the bone-to-implant contact (BIC) was calculated using light microscopy. The peri-implant bone apposition rate and the direction of bone growth were determined with the fluorescence microscope. For statistical evaluation, the Mann-Whitney U test, Wilcoxon signed ranks test, and Friedman test were chosen. During the healing period, nonartificial dehiscences were observed at 9 implants. The average BIC was 54.19% (14.51%-68.97%). There were significantly lower BIC rates detected for the cervical part of the implants compared with the middle part. An influence of dehiscences on the osseointegration could not be proven. There were no significant differences between the BIC values of the upper and lower jaw. During the observation period from the third to the eighth week after implantation, the average new bone formation rate was 2.32 µm/d (1.76-2.82 µm/d). During this period, the amount of new bone growth decreased insignificantly. Based on the sequence of the polyfluorochrome labeling, an implantopetal (53.03%) as well as an implantofugal bone growth (46.97%) have been observed. It could be assumed that the acid-etched implants offered a prerequisite to osseointegrate under a shortened healing period. The observed dehiscences seemed not to have compromised the rate of osseointegration.

Retrospective analysis of bar-retained dentures with cantilever extension: marginal bone level changes around dental implants over time.

PURPOSE: The aim of this study was to retrospectively determine whether a relationship exists between the length of the distal bar extension and the amount of marginal bone loss around implants supporting cantilevered bar-retained dentures. MATERIALS AND METHODS: This study was performed using data from patients who had been restored with implant-supported cantilevered bar-retained prostheses. Panoramic radiographs were obtained annually starting at the time of prosthetic loading of the implants; the protocol included a 4-year observation period. Vertical changes in the bone level were measured on the mesial and distal of implant sites with respect to a defined reference point per implant system, and radiographic distortions were compensated. Statistical analysis was performed with the Wilcoxon signed-rank test, the Spearman rank correlation test, and the two-factor nonparametric analysis for repeated measurements. RESULTS: A total of 48 edentulous patients who were consecutively treated with 313 dental implants and rehabilitated with 66 bar-retained prostheses were included in the study. Implants were used to support 30 prostheses in the maxilla (172 implants) and 36 prostheses in the mandible (141 implants). These prostheses were supported by bars with distal cantilevers of up to 12 mm. Patients with bars without cantilevers served as the control group. After 4 years, mean mesial bone loss was 2.20 +/- 0.91 mm; for distal implant sites it was 2.31 +/- 1.05 mm. The number of implants inserted and implant length did not correlate with bone loss. Jaw (maxilla versus mandible) and implant system exerted a significant influence on the amount of bone lost within the first year. Cantilever length did not influence marginal bone loss. CONCLUSION: In this clinical study, no influence of the length of cantilever extensions on crestal bone loss was found. Within the limitations of the study, the results indicate that restorations with distal bar extensions up to 12 mm are an adequate treatment option for edentulous patients.

Effects of repeated manual disassembly and reassembly on the positional stability of various implant-abutment complexes: an experimental study.

PURPOSE: The purpose of this study was to evaluate rotational, vertical, and canting changes in the position of the rotation-safe component in the implant-abutment assemblies of five different implant systems (ITI, Steri-Oss, Camlog, Astra Tech, and Replace Select) after manual removal and reassembly. MATERIALS AND METHODS: Prefabricated stainless steel models were used for each implant system, into which six implants were fixated with polymethylmethacrylate resin. Rotation-safe abutments (components) were screwed into the implants according to the manufacturers' specifications. Three test persons with varying knowledge of the theory and practice of implant dentistry manually assembled and reassembled the implant-abutment joint using each system-specific screwdriver 20 times each. A coordinate reading machine was used to detect discrepancies in position after each reassembly in relation to a coordinate system. Rotational freedom, changes in vertical height, and deviations in angulation were assessed. Statistical analysis was performed based on the nonparametric analysis of variance of repeated measurements. RESULTS: The tested complexes showed rotational freedom that ranged from 0.92 to 4.92 degrees, with significant differences between the systems. Camlog was significantly different from all other systems tested regarding rotational freedom, whereas Steri-Oss, Astra Tech, and Replace Select showed no significant difference between each other because of their nondiscrepant mean degree of rotational freedom. Vertical alterations in position ranged from 1 to 83 microm. A statistically significant difference was detected between butt-joint and beveled implant-abutment connections, with ITI and Astra Tech showing no significant difference when compared to each other, but displaying a significant difference versus all other systems tested. Canting discrepancies were not significant, with no influence of implant system or test person clearly detectable. CONCLUSION: Three-dimensional changes in the location of the abutment in relation to the implant result after manual assembly and reassembly of the implant-abutment complex.

Maxillary sinus augmentation following removal of a maxillary sinus pseudocyst after a shortened healing period.

PURPOSE: Dome-shaped radiopacities on the floor of the maxillary sinus are commonly interpreted as a sinus cyst on radiographs during dental implant planning. They might present an obstacle in sinus grafting, leading to bone graft failure or implant loss later. The therapeutic approaches to the removal of such cystic lesions and the following sinus augmentation are still controversial. The purpose of this article is to present a modified technique that can be used for predictable removal of a maxillary sinus cyst and sinus augmentation after a shortened healing period in patients with maxillary sinus pseudocysts. MATERIALS AND METHODS: A total of 11 patients with a mean age of 43.7 years with a radiographic dome-shaped opacity in the posterior maxilla sinus were included in this study. A lateral sinus window (with a diameter of about 5 mm) was prepared, and removal of the cyst was performed with grasping forceps. Three months after removal of the cyst, a conventional sinus augmentation with xenogeneic material was undertaken. Dental implants were placed 6 months later. Panoramic radiography and coronal/axial computed tomography were performed to diagnose the sinus lesion preoperatively and for follow-up. RESULTS: A total of 11 pseudocysts were removed from the sinuses of 11 patients under local anesthesia. Histologic evaluation showed antral pseudocysts in all specimens. A soft tissue scar was evident after 3 months of healing at the time of sinus augmentation. No sinus membrane perforation was seen or occurred during the sinus augmentation. A total of 17 implants were placed and restored prosthetically. No clinical complications were observed. The patients were followed up for a mean of 29.2 months (range, 17-43 months) after prosthetic loading, during which no implants were lost and no recurrence of the antral pseudocyst was observed. CONCLUSION: The described modified surgical technique allows the minimally invasive removal of the antral pseudocyst and histologic verification of the diagnosis without compromising the nasoantral entrance as well as the anatomy of the sinus for future sinus augmentations. It can be performed under local anesthesia without endoscopic equipment while shortening the treatment period.

A prospective randomized split-mouth study comparing iliac onlay grafts in atrophied edentulous patients: covered with periosteum or a bioresorbable membrane.

PURPOSE: In this prospective study, solid monocortical iliac onlay grafts of the maxilla were randomly covered with a bioresorbable membrane and periosteum within the maxilla. Histologic specimens were analyzed by light microscopy after a healing period of three months and the rate of resorption of the grafts were measured. MATERIALS AND METHODS: Fourteen patients (9 females and 5 males), with a mean age of 56 years (range 25-72) underwent augmentation with avascular iliac onlay bone grafts. The grafts were randomly covered either with a bioresorbable membrane (MC) or periosteum (PC). Resorption was measured with a digital caliper at the microscrews (slashed circle 1.5 mm) used to fixate the graft. Histologic evaluation of the specimens derived from the graft with a trephine bur (slashed circle 2 mm) from the implant site at implant placement after a 3-month healing period. Statistical evaluation of the data was performed using Analysis of variance and the Wilcoxon signed rank test. RESULTS: Clinical appearance of the augmented bone after 3 months showed a dense cortical layer with good vascular perfusion. Thirty-three sites in 13 patients (one dropped put) were analyzed histomorphometrically and showed an average of 46% newly formed bone with no significant difference between the groups (P=0.46). The mean resorption rate at 56 measured sites was 1.2 mm (range 0.3-3.4 mm) after 3 months, with no significant difference between the MC sites and the PC sites (P=0.38). DISCUSSION: Histomorphometry of new bone formation after 3 months demonstrates no significant difference between the PC and MC groups. Initialization of graft resorption can be seen after 3 months with no significant difference as to whether the graft was covered with a membrane or the periosteum. CONCLUSION: This study provides evidence that after avascular iliac bone grafting, the revascularization of the graft was sufficient after 3 months regardless of the graft coverage with no effect on the amount of initial resorption of the graft.

Clinical evaluation of a modified method of vestibuloplasty using an implant-retained splint.

PURPOSE: Oral rehabilitation of resected tumor patients often requires, besides the use of dental implants, the improvement of the soft tissue condition. In this clinical report, we describe a simple and effective surgical and prosthetic treatment procedure to achieve adequate long-term soft tissue conditions. MATERIALS AND METHODS: Seventeen tumor patients were selected for this evaluation. A total of 68 implants were placed in the mandible. At implant placement, a closed impression was taken from the implants for the fabrication of an implant-retained surgical splint. At second-stage surgery, vestibuloplasty by use of a split-thickness skin graft from the upper thigh was performed and an implant-retained splint was positioned. Pocket depths at the implants and the size of the graft were monitored over a period of 2 years. Statistical analysis by use of nonparametric 2-factorial analyses for repeated measures was performed. RESULTS: The mean mesial and distal pocket depths remained stable and measured 2.56 mm and 2.64 mm, respectively, at 24 months postoperatively. The graft showed an overall shrinkage of 18.5% in the vertical direction and 10.4% in the horizontal direction after 24 months. The shrinkage of the vertical direction compared with the horizontal direction showed a significant difference (P= .035). The shrinkage tendency was less than that described in the literature. CONCLUSIONS: The applied method described an easy, sufficient surgical procedure that minimizes shrinkage and creates a denture-bearing area that is stable over the long term, thus representing an improvement over previous methods.

Analysis of soft tissue display in Chinese subjects during an enjoyment smile.

OBJECTIVE: Due to global migration, clinicians often see patients with different ethnic backgrounds. Planning esthetic prosthodontic treatment for patients with different ethnicities can be a challenge. The aim of this study is to analyze the smile features of Chinese individuals. METHOD AND MATERIALS: Sixty-two Han-Chinese subjects with a mean age of 28.5 years were enrolled and photographed. Standardized digital photographs were made to measure the height of displayed maxillary gingivae, papillae, and teeth during an enjoyment smile. The data were then compared with the data acquired from Caucasians in a previous study. Statistical analysis was performed using the Mann-Whitney test and two-factorial nonparametric analysis. RESULTS: The mean display of the central incisors was 10 mm, with no significant difference between sexes (P = .74). The mean amount of display of the molars and premolars was significantly lower in Chinese (P < .001) than in Caucasians. The mean displayed gingiva in all subjects (n = 62) was 1.3 mm (0 to 8 mm). There was no significant difference between sexes (P > .05), but there was a significantly lower display of gingiva at the molars in Chinese (P < .001). Of all the subjects, 16.1% (n = 10) displayed gingivae from the central incisor to the first molar with a mean gingival height of 2.8 mm. The subjects showed a mean papilla height of 3.4 mm (0 to 11.6 mm) with no significant difference between sexes (P > .05). Again, a significantly lower display of papilla at the molar (P < .001) was found in Chinese. Of all subjects, 43.5% (n = 27) of all subjects showed papilla from the central incisor to the first molar. The mean papilla height of these subjects was 3.9 mm. All subjects displayed at least one papilla. CONCLUSION: The results indicate that pink esthetics is a prime factor for both Chinese men and women in the esthetic restoration from the central incisors to the premolars.

[Measurement and analysis of smile line of 62 Han-Chinese].

OBJECTIVE: To analyze smile features in maximum lip-dynamic in Chinese. METHODS: Sixty-two Han-Chinese, travelling in Germany, with a mean age of 28.5 years were enrolled and photographed. Standardized digital photos were made to measure the height of displayed maxillary gingiva, papilla and tooth during an enjoyment smile. Statistical analysis was performed using Mann-Whitney-U Test and non-parametric analysis. RESULTS: The mean height of tooth display for the central incisors was 10 mm, with no significant difference between the gender (P > 0.05). The mean height of gingival display was 1.3 mm and the mean papilla height was 3.4 mm. There was no significant difference between the genders (P > 0.05). 31% (19/62) of the subjects belonged to high smile line type, 50% (31/62) to medium smile line type and 19% (12/62) to low smile line type. CONCLUSIONS: The red esthetics is a paramount factor for Chinese men and women in the esthetic restoration. 81% of the Chinese studied showed various degree of gingival exposure from central incisor to the premolars, which defined the esthetic area for Chinese people. Papilla is a critical parameter for esthetic evaluation and treatment design. The ratio of high smile line in Chinese may be higher than that in Caucasian.

Healing of ungrafted and grafted extraction sockets after 12 weeks: a prospective clinical study.

PURPOSE: In this prospective study, bone formation in human extraction sockets augmented with Bio-Oss Collagen after a 12-week healing period was quantified and compared to bone formation in unaugmented extraction sockets. MATERIALS AND METHODS: Selected patients with four-walled extraction sockets were included in this prospective study. After extraction, the sockets were randomly augmented using Bio-Oss Collagen or left to heal unfilled without raising a mucoperiosteal flap. At the time of implant placement, histologic specimens were obtained from the socket and analyzed. Statistical analysis was performed using the Wilcoxon signed-rank test. RESULTS: Twenty-five patients with a total of 39 sockets (20 augmented, 19 unaugmented) were included in the study and the histologic specimens analyzed. All specimens were free of inflammatory cells. The mean overall new bone formation in the augmented sites was 25% (range, 8%-41%) and in the unaugmented sockets it was 44% (range, 3%-79%). There was a significant difference in the rate of new bone formation between the grafted and ungrafted sockets and a significant difference in the bone formation rate in the apical compared to the coronal regions of all sockets, independent of the healing mode. CONCLUSION: This descriptive study demonstrated that bone formation in Bio-Oss Collagen-grafted human extraction sockets was lower than bone formation in ungrafted sockets. Bone formation occurred in all specimens with varying degrees of maturation independent of the grafting material and was initiated from the apical region.

Miniature pigs as an animal model for implant research: bone regeneration in critical-size defects.

OBJECTIVE: Standardized experimental investigations determining the critical-size defect (CSD) in the mandible of miniature pigs are still lacking. The aim of the present study was to obtain information about the new bone formation in created defects of varying sizes. STUDY DESIGN: Marginal resection of the alveolar crest of the lower jaw was performed in 3 female miniature pigs. The animals used in the study were 3 years of age and weighed approximately 55 kg. For histologic evaluation the dental implants were harvested with the surrounding bone tissue 10 weeks after implant placement. For this, bone segments including the implants were removed from each side of the mandible. The sizes of the resected bone blocks varied, showing the following volumes: 10.1 cm(3), 4.2 cm(3), and 1.9 cm(3). Periosteal coverage of the defects was performed. Computerized tomography (CT) of the skull of the miniature pig was performed immediately after the surgical procedure as well as 6 weeks later using a 64-channel mult-slice scanner. RESULTS: The CT showed that 6 weeks after obtaining the biopsies, the filling of the defects with new bone varied. The percentage of newly formed bone in relation to the size of the original defect was 57.4% for the small- and 87.2% for the middle-sized defect. The large-sized defect showed 75.5% newly formed bone compared with baseline. CONCLUSION: Considering the amount of new bone formation found within this study, it is questionable if the critical defect size of 5 cm(3) stated in the literature is valid. Further research concerning the mandibular model in minipigs is required and more refinement needed to assure a standardized CSD, allowing qualitative and quantitative evaluation of bone grafts and bone graft substitutes.

Stable vertical distraction osteogenesis of highly atrophic mandibles after ablative tumour surgery of the oral cavity--a salvage pathway for mandibular reconstruction prior to oral rehabilitation with dental implants.

Mandibular reconstruction is still a challenge for surgeons. Distraction osteogenesis (DO) might contribute in certain instances to solve this problem. A principal advantage of DO is the expansion of the surrounding soft tissues that accompanies the bony regeneration. In addition there is no donor site morbidity when compared with reconstruction by autologous bone grafting. However its application may be limited by the thinness of the mandible and the attendant fracture risk. This article describes a technique that combines stable internal fixation with vertical distraction of the alveolar ridge in six patients with critical mandibular thickness after ablative surgery for cancer of the oral cavity. Prior to implant insertion for further prosthodontic restoration stable vertical mandibular distraction produced an additional 11-20mm. Improvement of the surrounding soft tissues, especially intraorally was achieved and dental implants were inserted after bony consolidation. This method can be a useful salvage technique for the augmentation of the atrophic mandible in patients who are not able or willing to undergo the risks and disadvantages of established methods such as free autologous bone transfer or microsurgical techniques.

Survival analysis and clinical evaluation of implant-retained prostheses in oral cancer resection patients over a mean follow-up period of 10 years.

STATEMENT OF PROBLEM: Dental implants have been increasingly used for prosthodontic rehabilitation of patients following oral tumor resection and postsurgical radiotherapy. However, only a few long-term studies have examined the implant survival rate and other factors related to prosthodontic treatment in oral tumor resection patients. PURPOSE: The purpose of this study was to evaluate the long-term survival of dental implants and implant-retained prostheses in oral cancer resection patients. MATERIAL AND METHODS: Ninety-three patients (63 men, 30 women) with a mean age of 59 years (range of 26-89 years) received 435 implants after the resection of a head and neck tumor. Twenty-nine patients received postsurgical radiotherapy prior to implant placement. The factors related to implant survival or failure were monitored over a mean observation period of 10.3 years (range of 5 to 161 months). Prosthodontic rehabilitation was evaluated with respect to the rates of technical failures and complications. Data were analyzed using a Kaplan-Meier curve and comparisons were made with the log-rank test or the Wilcoxon test (a=.05). RESULTS: Of the 435 implants, 43 implants were lost; the cumulative survival rate was 92%, 84%, and 69% after 3.5, 8.5, and 13 years, respectively. Twenty-eight implants in 6 patients were counted as lost since the patients had died. Twenty-nine irradiated patients received 124 implants, of which 6 implants were lost prior to prosthodontic rehabilitation. In 68 patients with 78 rigid bar-retained dentures, only minor technical complications were identified. However, all 25 fixed implant-supported restorations had no technical component failures and did not require technical maintenance. CONCLUSIONS: This study demonstrates that implant-retained and -supported prostheses in oral cancer resection patients, irrespective of the cancer treatment procedure, show lower long-term survival rates than those in patients without prior cancer surgery. Rigid fixation of the implant-supported prosthesis appears to minimize the complication rates. The poor implant survival rate was due to the higher mortality rate among these patients, and not to a lack of osseointegration.