Three-year analysis of Tapered Screw-Vent implants placed into extraction sockets grafted with mineralized bone allograft

With clinicians placing more dental implants, it is becoming increasingly important to maintain bone volume after tooth extraction. This article reports the results of implants placed into extraction sites grafted with particulate mineralized bone allograft (Puros). A total of 313 extraction sites were grafted with mineralized bone graft during a 36-month period. A total of 252 Tapered Screw-Vent dental implants were placed into the grafted extraction sites after a 4- to 7-month healing period. All reentries revealed a bony hard structure acceptable for osteotomy preparation. A total of 244 of these implants have been restored with fixed prosthesis and 6 with removable overdentures for a total of 250 loaded implants. A total of 6 implants failed, which required their removal (2 implants before load and 4 after loading), resulting in a 97.6% implant success rate. We conclude that mineralized human allograft placed into extraction sites is clinically useful to maintain bone volume. This material provided a bony hard structure acceptable for implant placement with good success rates.     

Maxillary Sinus Membrane Repair With Amnion–Chorion Barriers: A Retrospective Case Series

Background: Schneiderian membrane perforation is the most common complication of maxillary sinus augmentation procedures and has been associated with a variety of post‐surgical problems. Multiple techniques to repair perforated Schneiderian membranes with materials such as connective tissue, buccal fat pads, and resorbable collagen membranes have been reported in the dental literature. Although these reparative options have proven successful, they are technique sensitive and time consuming. The aim of this case series is to present a simplified method of Schneiderian membrane perforation repair with amnion–chorion membranes and results obtained from nine cases using this technique. Methods: A consecutive retrospective record review was performed of all maxillary sinus augmentation cases performed during the past 5 years by the same board‐certified private practice periodontist (DH). Results: Seventy‐seven cases were identified, with a total of 104 sinus augmentations, in which nine perforations were noted. None of the perforation cases were aborted midprocedure, and all perforations were repaired with amnion–chorion membranes. All cases were augmented with a combination of allograft and xenograft particulate bone. After an average healing time of 4.9 months, dental implants were placed in the grafted sinuses. Conclusions: This retrospective case series shows nine perforations during 104 lateral window maxillary sinus augmentation procedures. A total of 23 dental implants were placed in the augmented sinuses with perforated Schneiderian membranes, and one failure was noted according the Albrektsson success criteria. A total of 158 dental implants were placed in non‐perforated augmented sinuses, with a total of three failures noted.     

Effect of Maxillary Sinus Membrane Perforation on Vital Bone Formation and Implant Survival: A Retrospective Study

Background: The maxillary sinus augmentation procedure (SAP) using the lateral window technique has been documented to be a highly predictable procedure. However, the most common intraoperative complication has been reported to be maxillary sinus membrane perforation (MSMP). The present study evaluates the percentage of vital bone and implant survival in sinuses that had perforations repaired during surgery versus a non‐perforated sinus group. Methods: Data were obtained retrospectively from an Institutional Review Board–approved anonymous database at New York University, Kriser Dental Center, Department of Periodontology and Implant Dentistry, New York, New York, from 23 patients who had undergone SAP with a total of 40 treated sinuses. Sinuses were grafted with mineralized cancellous bone allograft, anorganic bovine bone matrix, or biphasic calcium phospate. Perforation complications occurred in 15 sinuses with 25 non‐perforated sinuses. All perforations were repaired during surgery with absorbable collagen membrane barriers. Histologic cores were taken from all treated sinuses 26 to 32 weeks after surgery. The implant success rate of 79 placed implants was recorded. Results: The average percentage of vital bone was 26.3% ± 6.3% in the perforated (repaired) sinuses versus 19.1% ± 6.3% in the non‐perforated sinuses. The differences were statistically significant (SS). The implant success rate was 100% (35 of 35) compared to 95.5% (43 of 45) in the perforated/repaired vs. non‐perforated sinuses, respectively. There was no SS difference in implant failure rates. Conclusions: The augmented sinuses in this study that exhibited MSMPs that occurred during the SAP (which were treated during surgery) show SS greater vital bone percentages compared with the non‐perforated sinus group. There were no SS differences in implant survival in the perforated versus non‐perforated groups. In this study, sinus MSMPs, when properly repaired during surgery, do not appear to be an adverse complication in terms of vital bone production or implant survival.     

Healing in smokers versus nonsmokers: survival rates for sinus floor augmentation with simultaneous implant placement

PURPOSE: Evidence suggests that smoking is detrimental to the survival of dental implants placed in grafted maxillary sinuses. Studies have shown that improving bone quantity and quality, using rough-surfaced implants, and practicing good oral hygiene may improve outcomes. In this prospective study, the long-term survival rates of implants placed simultaneously with sinus grafting in smokers and nonsmokers were compared. MATERIALS AND METHODS: Implants with roughened surfaces were immediately placed into maxillary sinus grafts in patients with 1 to 7 mm of residual bone. A total of 2132 simultaneous implants were placed into the grafted sinuses of 226 smokers (627 implants) and 505 nonsmokers (1505 implants). A majority of the patients received a composite graft consisting of 50% autogenous bone. In both smokers and nonsmokers, approximately two thirds of the implants had microtextured surfaces; the remainder had hydroxyapatite-coated surfaces. The implants were restored and monitored during clinical follow-up for up to 9 years. RESULTS: Cumulative survival of implants at 9 years was 97.9%. There were no statistically significant differences in implant failure rates between smokers and nonsmokers. DISCUSSION: Implant survival was believed to depend on the following aspects of the technique used: creation of a large buccal window to allow access to a large recipient site; use of composite grafts consisting of at least 50% autogenous bone; meticulous bone condensation; placement of long implants (i.e., 15 mm); use of implants with hydroxyapatite-coated or microtextured surfaces; use of a membrane to cover the graft and implants; antibiotic use and strict oral hygiene; use of interim implants and restricted use of dentures; and adherence to a smoking cessation protocol.     

Influence of Sinus Floor Configuration on Grafted Bone Remodeling After Osteotome Sinus Floor Elevation

Background: This study investigates influence of the sinus floor configuration on dimensional stability of grafted bone height after the osteotome sinus grafting procedure. Methods: Forty single‐tooth dental implants inserted after placement of bioglass and/or allograft into the sinus area using an osteotome technique in 37 patients were evaluated in this retrospective study. Periapical radiographs were taken using the long‐cone technique before and after implant placement. Specifically, radiographic measurements of grafted bone height at the mesial and distal side of each implant were taken, and the sinus floor configuration was classified into concave, angle, and flat according to the sinus floor profile at the implant site. Furthermore, the intruding angle, defined as the angle between the implant axis and sinus floor, was measured. Results: All implants were clinically stable during a mean follow‐up period of 39.2 months. Mean initial gain of sinus grafted bone height was 7.0 ± 1.9 mm, and later it was reduced to 4.6 ± 1.9 mm at follow‐up (P <0.001). A greater reduction in grafted bone height was revealed in the flat sinus group compared with the concave group (P <0.001). Results from the linear regression showed larger intruding angles were statistically significantly associated with a greater reduction in grafted bone height (r² = 0.55, P <0.001). Conclusion: All bioglass and/or allograft placed in the maxillary sinus after the osteotome technique underwent remodeling and shrinkage; however, the outcome of the procedure was more predictable in sinuses with a concave floor and small implant‐intruding angles.     

Maxillary sinus augmentation using different grafting materials and osseointegrated dental implants in monkeys. Part IV Evaluation of hydroxyapatite‐coated implants.

The aim of this study was to evaluate clinically, histologically and histometrically the use of hydroxyapatite-coated dental implants in conjunction with maxillary sinus augmentation procedures. In 4 adult male Rhesus monkeys (Mucaca muluttu) the 3 maxillary molars on 1 side of the jaws were extracted and the remaining bone between the alveolar crest and the floor of the sinus was reduced to 3–4 mm. After 3 months, maxillary sinus augmentation procedures were performed in each monkey and the sinuses were grafted with a porous hydroxyapatite bone graft (Interpore-200®). At the same time, 2 hydroxyapatite-coated cylinder implants (IMZ®) were immediately placed into the augmented sinuses (i.e. simultaneous-implants-loaded group). Four months later, 2 additional similar implants were placed into the previously augmented sinuses (i.e. delayed-implants-loaded group). After 4 months, the abutment connection was performed, and all 4 implants were loaded with a gold-alloy bridge for 6 months (i.e. until sacrifice of the animals). The contralateral side of each monkey received the same treatment with the exception that removal of the maxillary molars was performed 7 months after those in the opposite side, and that the implants in this side were not loaded. Thus, 2 additional study groups (i.e. simultaneous-implants-unloaded group and delayed-implants-unloaded group) were obtained. Clinically, all loaded and unloaded implants were stable the day of sacrifice. Histologically, the grafted sinuses exhibited a significant amount of new bone formation, with integration of the porous hydroxyapatite graft particles and hydroxyapatite-coat of the dental implants to the new bone. Histometric analysis indicated that on the loaded side the implants placed simultaneously with the sinus lift procedure exhibited greater direct mineralized bone-to-implant contact than the delayed placed implants. In addition, the percentage of direct mineralized bone-to-implant contact was significantly greater in the residual bone in comparison to the augmented area in all groups. Loading of the implants exhibited a positive effect on the percentage of direct mineralized bone-to-implant contact in the augmented area. It could be concluded that hydroxyapatite-coated implants may be of benefit when used in conjunction with sinus augmentation procedures.     

The use of a mineralized allograft for sinus augmentation: an interim histological case report from a prospective clinical study

A prospective clinical research study of various graft materials used for the augmentation of human maxillary sinuses is currently in progress at New York University Department of Implant Dentistry. This interim case report describes the healing response after a sinus augmentation procedure using a new mineralized cancellous bone allograft. The results after 9 months of healing demonstrated a vital bone content of 25.2% in the grafted sinus, as ascertained from a trephine core taken from the superior aspect of the lateral window area. Although the vital bone requirement for implant survival in an augmented sinus is unknown, the 25.2% vital bone demonstrated in this case compares favorably with that reported in the literature for other augmentation materials, including xenografts, alloplasts, and autogenous bone.     

Maxillary sinus augmentation using different grafting materials and dental implants in monkeys. Evaluation of autogenous bone combined with porous hydroxyapatite.

The aim of this study was to evaluate clinically, histologically, and histometrically the use of autogenous bone combined with porous hydroxyapatite (Interpore 200®) as a grafting material for maxillary sinus augmentation procedures. In 4 adult male rhesus monkeys (Macaca mulatta) the 1st, 2nd and 3rd maxillary molars on one side of the jaws were extracted. After a healing period of 3 months. maxillary sinus augmentation procedures were performed in each monkey, and the sinuses were grafted with autogenous bone from the monkeys' tibia mixed in a 3:1 ratio with porous hydroxyapatite. At the same time. 2 pure titanium plasma-sprayed IMZB cylinder implants were immediately placed into the augmented sinuses (i.e. simultaneous implants-loaded group). After 4 months, 2 additional similar implants were placed into the previously augmented sinuses (i.e. delayed implants-loaded group). Four months later, the abutment connection was performed and all 4 implants were loaded with a gold-alloy bridge for 6 months (i.e. until sacrifice of the animals). The contralateral side of each monkey received similar treatment with the exception that the extractions were performed 7 months after those in the opposite side and that the implants were not loaded. Thus, 2 additional study groups (i.e. simultaneous implants unloaded group and delayed implants unloaded group) were obtained. Clinically, all loaded implants were stable at the day of sacrifice. Histologically, the grafted sinuses exhibited a significant amount of new bone formation. The porous hydroxyapatite granules appeared integrated with the newly formed bone. Histometric analyses revealed that delayed implant placement resulted in a greater amount of direct mineralized bone-to-implant contact in the augmented area than the simultaneous implant placement. Furthermore, the percentage of direct mineralized bone-to-implant contact was far more significant in the residual bone than in the augmented area. It was concluded that the autogenous bone/porous hydroxyapatite graft combination enhanced bone formation and mineralized bone-to-implant contact in the augmented sinuses and that the delayed implant placement may be favorable for sinus augmentation procedures.     

Maxillary sinus grafting with anorganic bovine bone: a clinical report of long-term results

PURPOSE: The aim of the present retrospective study was to evaluate the survival rate of titanium plasma spray-coated cylindric and machined screw-type implants placed in sinuses grafted with anorganic bovine bone mixed with demineralized freeze-dried bone allograft (DFDBA) or with anorganic bovine bone alone. MATERIALS AND METHODS: The patients included in this study were treated with a 1- or 2-stage technique, according to the volume of residual bone. This determined the possibility of primary stabilization and the duration of the treatment, which was 9 or 12 months, respectively. RESULTS: The overall implant survival rate was 94.5% after a mean functioning period of 6.5 +/- 1.9 years. The Implant survival rate was better in sinuses grafted with anorganic bovine bone alone than with a mixture of anorganic bovine bone with DFDBA (96.8% versus 90%). The implant survival rate was similar for cylindric and screw-type implants in sinuses grafted with anorganic bovine bone alone. DISCUSSION: Because of the good bone quality, the implant survival rate was similar for cylindric and screw-type implants in sinuses grafted with anorganic bovine bone. CONCLUSION: Anorganic bovine bone used alone appears to be a suitable material for sinus floor augmentation.     

Maxillary sinus augmentation using different grafting materials and dental implants in monkeys

The aim of this study was to evaluate clinically, histologically and histometrically the use of anorganic bovine bone matrix (i.e. Bio-oss®) as a grafting material for maxillary sinus augmentation procedures. In 4 adult male rhesus monkeys (i.e. Mucaca mulattu) the 1st 2nd and 3rd maxillary molars on one side of the jaws were extracted. The remaining bone between the alveolar crest and the bottom of the sinus was then reduced to 3–4 mm. After 3 months, maxillary sinus augmentation procedures were performed on one side of the jaws in each monkey and the sinuses were grafted with the bovine bone matrix. At that time, 2 IMZ pure titanium plasma coated implants were immediately placed into the augmented sinuses (i.e. simultaneous implants-loaded group). After 4 months, 2 additional similar implants were placed into these previously augmented sinuses (i.e. delayed implants-loaded group). Four months later, the abutment connection was performed and all 4 implants were loaded with a gold-alloy bridge for 6 months (i.e. until sacrifice of the animals). The contralateral side of each monkey received the same treatment with the exception that the extractions were performed 7 months after those in the opposite side and that the implants in this side were not loaded. Thus, 2 additional study groups (i.e. simultaneous implants-unloaded group and delayed implants-unloaded group) were obtained. Clinically, all loaded implants were stable at the day of sacrifice. Histologically, the grafted sinuses exhibited significant bone formation with integration of the bovine bone matrix particles to the new bone. Direct mineralized bone-to-implant contact was greater for the delayed implant placement groups than for the implants installed simultaneously with the sinus augmentation. Furthermore, the percentage of direct mineralized bone-to-implant contact was greater in the residual bone than in the augmented area. It was concluded that the anorganic bovine bone matrix facilitated bone formation and implant osseointegration in the augmented sinuses and that the delayed implant placement in combination with the sinus augmentation procedure seemed to be preferable.     

Effect of sinus membrane perforation on dental implant integration: a retrospective study on 128 patients

A common complication of sinus augmentation is perforation of the sinus membrane during augmentation and/or implant placement. This retrospective study examines the effect of sinus membrane perforation with regard to graft survival and implant integration. A total of 175 sinuses were augmented with 115 of the membranes being reported intact at the time of surgery. A total of three infections occurred in patients who sustained perforated sinuses and one infection occurred in a patient who had an intact sinus. All four infections resolved after culture sensitivity and placement of the patient on an appropriate antibiotic for 10 days. Of 438 dental implants placed in the augmented sinuses, five implants failed, four of which were associated with perforated sinuses and and which was not associated with a perforated grafted sinus.     

Survival of cylindrical implants in composite grafted maxillary sinuses

Purpose: This retrospective study investigated the survival of dental implants placed in the maxilla after composite grafting of the sinus and an average of 55 months of loading.Patients and Methods: Maxillary sinuses of 88 patients were grafted with autogenous cancellous bone combined with dense hydroxyapatite particles. After an average healing period of 3.4 months, hydroxyapatite-coated titanium endosseous implants were placed. A total of 388 implants were placed in grafted sinus floors, and 82 were placed in onlay grafted nonsinus position in the canine region. The implants were loaded with overdentures and fixed bridges 4 months (mean) after implantation, with a follow-up for a mean of 55 months.Results: The cumulative implant survival was calculated according to the Kaplan-Meier method. Implant survival from the time of loading was 89% in full reconstructed cases and 90% in partially edentulous cases. The overall cumulative implant survival rate, including the loss in the surgical stage, was 82%.Conclusion: Implant loss in composite grafted maxillae after 70 months of follow-up was similar to loss in nongrafted maxillae.     

The use of mineralized bone allograft as a single grafting material in maxillary sinus lifting with severely atrophied alveolar ridge (1–3 mm) and immediately inserted dental implants. A 3- up to 8-year retrospective study

Objective

The primary aim of our study was to evaluate the efficacy of mineralized bone allograft alone in sinus floor augmentation with simultaneous implant placement in cases with severe atrophy of the residual maxillary bone (bone height <?4 mm).

Methods

Thirty-five dental implants were placed in 29 patients who underwent sinus augmentation via traditional lateral window technique from 2008 to 2013. Patients with residual alveolar height between 1 and 3 mm at the site of implantation were included in the study. The height of residual bone was initially estimated by plain panoramic X-ray and reevaluated intraoperatively by precise micrometric measurement at the site of implantation. Implants of 13 mm height and 3.5 or 4.3 mm in diameter were inserted simultaneously. Mineralized bone allograft was used alone to augment the sinus floor.

Results

No wound dehiscence was recorded. In one case there was a postoperative site infection which subsided with antibiotics without implant failure. One implant migrated during the postoperative period to the maxillary sinus and was removed. One implant failed. The remaining 33 implants were successfully loaded. Follow-up ranged from 3 to 8 years.

Conclusions

Maxillary sinus lift in severely absorbed alveolar ridges with simultaneous implant placement could be safely performed using mineralized allograft alone, rendering the procedure less invasive and less time-consuming.

     

Factors affecting the survival of implants placed in grafted maxillary sinuses: a clinical report

Many factors affect the survival rate of osseointegrated implants placed in grafted maxillary sinuses. This clinical report describes the retrospective evaluation of 60 patients with 228 implants placed in 84 grafted maxillary sinuses at the Loma Linda University School of Dentistry. The factors used to determine the survival rates of these implants were implant type, simultaneous/delayed implant placement, pretreatment bone height, oral hygiene, and cigarette smoking habits. Out of the total 228 implants, 205 (89.9%) remained in function after a mean follow-up period of 41.6 months (range 0 to 60 months). A higher failure rate was associated with the use of non-threaded implants, poor oral hygiene, and smoking. This information may facilitate treatment planning and enhance communication between the dentist and patient regarding the risk/benefit ratio and outcomes of implants placed in grafted maxillary sinuses.     

The effect of cigarette smoking and native bone height on dental implants placed immediately in sinuses grafted by hydraulic condensation

The purpose of this study was to determine the effect of cigarette smoking and residual native bone height on the survival of dental implants placed immediately in grafted sinuses. In this retrospective study, 334 subject records were screened, and 75 subjects (155 implants) were included. Data collection based on treatment notes and radiographs included age, sex, smoking status, sinus floor bone height, dental implant information, and implant survival. The survival rates of implants for nonsmokers and smokers at stage-two surgery were 93% and 84%, respectively. After 12 months of functional loading, the survival rates of implants for nonsmokers and smokers were 87% (81 of 93) and 79% (49 of 62), respectively (P < .000). Analysis revealed that the effect of smoking on implant survival is significant when the preoperative bone height is less than 4 mm, with an 82.4% implant survival rate in nonsmokers compared to 60% in smokers (P < .05). Smoking should be considered as a high risk factor when implants are placed immediately in grafted sinuses, particularly in areas of limited bone height.     

Augmentation grafting of the maxillary sinus and simultaneous implant placement in patients with 3 to 5 mm of residual alveolar bone height.

This study assessed the efficacy of augmentation grafting of the maxillary sinus with simultaneous placement of dental implants in patients with less than 5 mm of alveolar crestal bone height in the posterior maxilla prior to grafting, although the procedure has traditionally been contraindicated based on empirical data. A total of 160 hydroxyapatite-coated implants was placed into 63 grafted maxillary sinuses in 63 patients whose crestal bone height in this region ranged from 3 to 5 mm. Patients were followed for 2 to 4 years after the placement of definitive prostheses. There were no postoperative sinus complications. Following uncovering of the implants at 9 months after surgery, there was no clinical or radiographic evidence of crestal bone loss around the implants. Histologic examination of bone cores from the grafted sites revealed successful integration and a high degree of cellularity. All patients maintained stable implant prostheses during follow-up. These findings indicate that the single-step procedure is a feasible option for patients with as little as 3 mm of alveolar bone height prior to augmentation grafting, utilizing hydroxyapatite-coated implants and autogenous bone.     

Predictability of simultaneous implant placement in the severely atrophic posterior maxilla: A 9-year longitudinal experience study of 2132 implants placed into 731 human sinus grafts

PURPOSE: One-stage implant placement in the grafted maxillary sinus has traditionally been limited to patients with at least 5 mm of residual bone to ensure complete implant stabilization. The aim of this prospective study was to determine the long-term survival rates of implants with roughened surfaces placed immediately into maxillary sinus grafts in patients with 1 to 5 mm of residual bone. MATERIALS AND METHODS: A total of 2132 microtextured screw-type (n=1374) or hydroxyapatite-coated cylinder-type (n=758) implants were immediately placed into the grafted sinuses of 731 patients. The implants were restored and monitored for up to 9 years of clinical follow-up. RESULTS: Cumulative survival at 9 years was 97.9% (n=2091 implants); 20.4% of the implants were placed in 1 to 2 mm of residual bone. Discussion: Initial implant stability and parallelism were achieved through a combination of meticulous condensation of the particulate bone graft material around the implants, the frictional interface of the roughened implant surfaces and the host tissues, and selection of an appropriate graft material. CONCLUSIONS: Simultaneous implant placement into sinus floor grafts can be a predictable treatment option for patients with at least 1 to 2 mm of vertical residual bone height when careful case planning and meticulous surgical techniques are used.     

Maxillary sinus floor augmentation using bioactive glass granules and autogenous bone with simultaneous implant placement. Clinical and histological findings

This clinical study was undertaken to: 1) evaluate the use of bioactive glass Biogran combined with autogenous bone as grafting material for maxillary sinus augmentation with simultaneous implant placement using radiography and histology; and 2) document the short-term post-loading success of implants inserted in sinus cavities augmented with this material. Unilateral or bilateral sinus augmentation was performed in 12 patients with 3-5 mm of alveolar crestal bone height in the posterior maxilla prior to grafting. The sinuses were grafted with bioactive glass mixed in a 4:1 ratio with autogenous bone. Simultaneously, 2-3 threaded titanium implants were inserted into the augmented sinuses. Second stage surgery was carried out 9 to 12 months post implantation. At abutment connection, 10 core biopsy specimens were taken from different grafted sites and evaluated histologically. All 27 implants were clinically stable at second stage surgery. A mean increase in mineralized tissue height of 7.1 +/- 1.6 mm was evident when comparing the pre-surgical CT scans with those performed 9-12 months following the sinus augmentation procedure. Evaluation of the cores yielded a mean of 30.6 +/- 5.7% of bone tissue in the grafted sites. One implant failed during the prosthetic phase while the remaining 26 implants were stable 12 months post loading. This study suggests that Biogran/autogenous bone graft combination used in one-stage sinus augmentation yields sufficient quality and volume of mineralized tissue for predictable simultaneous implant placement in patients with 3-5 mm of bone height prior to grafting.     

Bone resorption around dental implants placed in grafted sinuses: clinical and radiologic follow-up after up to 4 years

PURPOSE: The long-term results of endosseous implants depend on the maintenance of bone support. The aim of this study was to evaluate radiologically bone resorption around dental implants placed in grafted sinuses after up to 4 years of function. MATERIALS AND METHODS: Between 1997 and 2001, augmentation of the maxillary sinus floor with alloplastic (Biostite) or xenogenic (Bio-Oss) materials was performed in 34 patients. RESULTS: Eighteen patients participated in the study. Twenty-six sinus augmentations were performed on these 18 patients, and they received 37 implants. The change in marginal bone level around the implants at the mesial side was 1 mm during the first year after the abutment connection, followed by an annual loss of 0.1 mm. The change in marginal bone level around the implants at the distal side was 1.1 mm during the first year after the abutment connection followed by an annual loss of 0.2 mm. DISCUSSION: The implant survival rate observed in this study is in line with data previously reported for patients treated with implants in the posterior maxilla without bone atrophy. The results for implants placed into sinuses grafted with Bio-Oss were similar to the results for implants placed in sinuses grafted with Biostite. CONCLUSION: Although this study involved a limited number of procedures, it confirmed that alloplastic and xenogenic materials can be reliable for bone regeneration in subantral cavities. The angular defects present both at the distal and mesial sides of the implants were comparable to those observed at implants placed in native bone.     

Porous hydroxyapatite for grafting the maxillary sinus in sheep: comparative pullout study of dental implants

PURPOSE: In this experimental study, dental implants placed after maxillary sinus grafting with either porous hydroxyapatite (HA) (Interpore 200) or autogenous bone were examined for their mechanical stress tolerance. MATERIALS AND METHODS: A total of 54 titanium plasma flame-sprayed cylindric implants were placed in the lateral sinus wall bilaterally of 27 mountain sheep. The bony sinuses were opened through an extraoral approach. Eighteen sinuses were grafted with porous HA, and another 18 were grafted with cancellous bone from the iliac crest. Eighteen non-grafted sinuses were used as controls. In the same operation, 2 cylindric implants were placed in each of the sinuses. One implant of each sinus was tested for mechanical strength of the bone-implant interface at 12, 16, and 26 weeks using pullout force. RESULTS: The mean pullout force was 259.3 N in the control group, 356.7 N in the autogenous bone group, and 376 N in the HA group. Pooled data for the grafted sites showed the pullout force to be significantly higher than in the empty control sites (P = .02). The pullout force increased significantly with ongoing healing time (P = .02), but there was considerable variation within the groups. While the force remained more or less constant throughout the follow-up time in the controls (248 N at week 12 to 276 N at week 26), it increased dramatically in the group augmented with autogenous bone (223.8 N at week 12 to 523.16 N at week 26). The pullout force was initially highest in the HA group (302.3 N at week 12) and increased to 423.5 N at 26 weeks, but it did not reach the levels recorded in the autografted group. DISCUSSION AND CONCLUSION: Mechanical tests of bone-to-implant contact in a sheep model showed that HA for 1-stage sinus floor elevation significantly increased the pullout force versus ungrafted sinuses, although it was less than that found with autogenous bone after 26 weeks.