The aim of this report is to determine the long-term histologic and histometric evaluation of beta-tricalcium phosphate (beta-TCP) and bovine cancellous bone grafted into the left maxillary sinus of a patient in order to augment the sinus floor to prepare it for receiving an implant. Beta-TCP and bovine cancellous bone (BCB) were grafted into the left maxillary sinus at the extracted sites of maxillary left first and second molars of a 62-year-old male patient. Using osteotome technique, 45 months later, core biopsies were taken for histologic and histometric comparison of the newly formed bone. Histometric and histologic evaluation of both specimens revealed a normal maxillary bone structure with 23.08% calcified bone and 76.92% marrow and connective tissue for the beta-TCP grafted site, and 24.81% calcified bone with 75.19% marrow and connective tissue for the BCB grafted site. No residual grafting material was seen in either specimen. Both beta-TCP and BCB were completely resorbed and replaced by new bone 45 months after grafting. Histologic results of the newly formed bone were similar for both grafting materials.

Introduction

Sinus floor augmentation is a well-accepted and predictable surgical procedure for increasing the volume of bone for placement of dental implant in areas of the posterior maxilla with insufficient bone quantity and quality.1,2 Successful implant integration in sinus augmentation is characterized by maximum bone formation at the implant interface, so that enough bone is provided for mechanical support and integration of the implant.3,4 

In the original sinus floor augmentation, autogenous bone was utilized.5,6 However, the use of autogenous bone requires a second surgical site, and this increases the surgical duration, surgical risk, and postsurgical complications, since healing is required at more than one site. Later, other grafting materials such as allografts, xenografts, alloplasts, and natural and synthetic hydroxyapatite were used by clinicians as bone substitute materials in sinus grafting.710 

A bone substitute material should allow integration of loaded implants and an optimal biomaterial should be resorbed and replaced by newly formed bone.7 Histologic and histometric evaluation of the newly formed bone in grafted sinuses is the only means to show the preference of one grafting material over the other.1113 Bovine cancellous bone (BCB) is a xenogenic and osteoconductive material that has been used successfully in sinus augmentation and repair of periodontal defects.14 

Beta-tricalcium phosphate (beta-TCP) is an alloplast material that has also been used in sinus floor augmentation and has dissolved homogeneously, mainly by the physiochemical process, and resorbed concurrently with the formation of new bone.14,15 

The purpose of the present report is histologic and histomorphometric analysis of the newly formed bone, 45 months after the left maxillary sinus was grafted with beta-TCP and BCB.

Materials and Methods

A 62-year-old white man with an unremarkable past medical history, who had lost his maxillary left first and second molars (teeth nos. 14 and 15) requested replacement of those teeth with implants supported by crowns.

The patient had previously undergone periodontal treatment and surgery by the author and had been seen regularly for check-up and cleaning. Radiographic examination showed approximately 1 mm of bone remaining between the sinus floor and the alveolar crest in the extracted site of the maxillary left first molar, and 3–4 mm at the extracted site of the maxillary left second molar (Figure 1a). Since there was not enough bone to provide the necessary primary stability for the implants, it was decided to proceed with the 2-stage sinus floor augmentation procedure, using the osteotome technique that had been described previously.1517 Using this technique, after administration of local anesthesia, a crestal incision with extension to the buccal and palatal aspect of maxillary second premolar (tooth no. 13) was made, and a full-thickness flap was reflected buccally and palatally to expose the alveolar crest. A no. 6 round bur was then used to penetrate the cortical bone in the areas of maxillary left first and second molars (teeth nos. 14 and 15) without penetrating the sinus. Then, 2- to 2.8-mm and 2.8- to 3.3-mm concave tipped osteotomes were used to widen the osteotomy site and penetrate into the sinus without damaging the sinus membrane. The grafting materials used were 0.25–0.50 g of beta-TCP granules (500–1000 µm) for the maxillary left first molar (tooth no. 14) and 0.25–0.50 g of bovine cancellous microchip granules (0.25–1 mm) for the maxillary left second molar (tooth no. 15).

These materials were placed under the schneiderian membrane through the osteotomy sites using osteotome with gentle pressure and care. The mucoperiosteal flap was then sutured without using any membrane and finally a postsurgical periapical X ray was taken (Figure 1b). Postsurgical medication included amoxicillin, 500 mg every 6 hours for 7 days. Analgesic and chlorhexidine mouthwash were also prescribed. Ten days later the sutures were removed and healing was uneventful. The patient was then evaluated every 3 months and periapical X rays were obtained at 6 and 9 months for evaluation and comparison.

During the healing period of the grafted sites, the patient developed cardiac arrhythmia, and his cardiologist prescribed warfarin and forbade any oral surgical procedure, unless emergency ruled otherwise.

Forty-five months after the sinus graft, the patient returned for placement of the implants. His cardiac condition had improved; therefore, warfarin was discontinued and his cardiologist approved the implant surgery. At this stage, panoramic and periapical X rays were taken and approximately 3–4 mm of bone was observed on the maxillary left first molar (beta-TCP) and 6–7 mm on the maxillary left second molar (BCB) (Figure 1c).

A surgical protocol, including 1-stage osteotome sinus floor augmentation and simultaneous implant placement was considered for the aforementioned teeth.16,18 After local anesthesia was administered, a crestal incision was made, and the mucoperiosteal flap was reflected as previously described. At this stage core samples were taken from both grafted sites using trephine bur with a 3-mm internal diameter. The samples taken were 3–4 mm in length and 3 mm in diameter from the beta-TCP grafted site and 6 mm in length and 3 mm in diameter from the BCB grafted site. The samples were then placed in 10% formalin solution and submitted for blinded histologic and histomorphometric analysis.

Then, a 2.8- to 3.3-mm concave tipped osteotome was used for widening of the osteotomy sites and perforation of the sinus floor, simultaneous with regrafting the sinus floor with BCB. This was followed by placement of 2 implants, 8 mm in length and 4.8 mm in diameter, single-stage tapered for the previously mentioned teeth. The mucoperiosteal flap was then sutured around the implant neck and a periapical radiograph was taken. Antibiotic and analgesic therapy with chlorhexidine mouthwash was prescribed for the patient. Ten days later the sutures were removed and healing was uneventful (Figure 1d).

Results

Five histologic sections from beta-TCP and 3 sections from BCB were studied. Histologic evaluation of both cores (specimens) showed a typical maxillary bone with large marrow space and blood vessels, and lamellar cortical bone with osteocyte lacunae. Specimen no. 1 (beta-TCP) showed no inflammatory cell infiltration, while specimen no. 2 (BCB) showed some mild infiltration of inflammatory cells. No residual grafting materials were seen in either specimen (Figure 2a through d).

Histomorphometric analysis of the core taken from the beta-TCP grafted site revealed 23.08% calcified bone and 76.92% marrow and connective tissue with no grafting material residue.

Similar analysis of the core taken from the BCB grafted site showed 24.81% calcified bone and 75.19% marrow and connective tissue with no grafting material residue.

Discussion

The sinus floor augmentation procedure adequately increases the vertical dimension of the resorbed alveolar process in the posterior maxilla, thus enabling placement of implants and achieving sufficient primary stabilization.

The graft materials used in sinus grafting generally include autogenous bone (intra and extra oral source), allografts (mineralized and demineralized) from different persons, xenografts (from different species), alloplast (synthetic like TCP), and hydroxyapatite preparations.

Literature shows a wide range of results for different grafting materials.11,12,19,20 

In the study by Kolerman et al,21 mineralized freeze-dried bone allograft was used and grafted into the maxillary sinus of 19 patients. Nine months later biopsies were taken and histologic and histometric study showed 29.1% newly formed bone, 51.9% connective tissue, and 19.0% graft material residue.

Froum et al19 used mineralized cancellous bone allograft (MCBA) in their study and Bio-Oss in bilateral sinus augmentation. The biopsies taken at 26–32 weeks demonstrated 28.25% of vital bone for MCBA and 12.44% for Bio-Oss. The residual graft material was 7.65% for MCBA and 33% for Bio-Oss; bone marrow was 64.10% for MCBA and 54.56% for Bio-Oss.

Yassibag-Berkman et al22 in their human study were also able to demonstrate a significant clinical attachment gain and radiographic bone fill (2.4 mm) in interproximal intrabony defects 12 months after grafting with beta-TCP.

Although the results obtained from different researchers helped clinicians to reach a decision as to which material to use in sinus grafting, more often this decision is based on the quality and quantity of the newly formed bone as well as the survival rate of the implants placed in the grafted sinus.

A study by Valentini et al23 and Hallman et al4 showed a higher survival rate of implants placed in a sinus grafted with 100% xenograft than in a sinus grafted with 100% autogenous bone or a composite graft of xenograft and autogenous bone.

A systematic review2 of implant survival in maxillary sinus grafts that included 6913 implants placed in 2046 patients revealed a 91.49% survival rate; this was 87.70% when autogenous bone alone was used, 94.88% when autogenous bone was combined with other materials, and 95.98% when bone substitutes were used alone.

Iezzi et al12 in their histometric study of a retrieved broken implant demonstrated 40% ± 2.4% bone, 12% ± 2.9% anorganic bovine bone (ABB) and 50% ± 6.9% marrow space 5 years after sinus grafting, using 100% ABB.

A similar study by Traini et al11 showed 46% ± 4.67% newly formed bone, 16% ± 5.89% ABB remnants, and 38% ± 93% marrow space 9 years after sinus grafting with 100% ABB.

The materials used in this report for sinus grafting were BCB microchips (Tutodent 0.25–1 mm) and beta-TCP (Cerasorb 500–1000 µm). The Tutodent is a Tutoplast-processed BCB, and consists of natural bone matrix, which is calcium mineral by 60%–66% and bone collagen by 35%, the latter being a xenograft material. The Cerasorb is a pure beta-TCP and is an alloplast graft material.

The histologic and histomorphometric results of this report demonstrated 23.08% calcified bone with 76.92% marrow and connective tissue where beta-TCP was used and 24.81% calcified bone with 75.19% marrow and connective tissue where BCB was used 45 months after sinus grafting.

Interestingly and unlike the other materials (Bio-Oss and allografts), no grafting material residue was observed in either of the grafted sites and apparently all the materials had undergone resorption and were replaced by new bone.

It was also interesting to note that the initial radiographic dimension of the space created and filled by the materials placed into the sinus had significantly decreased with regard to the sinus floor bone volume and height 45 months after grafting. This may be related to the faster resorption rate of BCB and beta-TCP in contrast to the materials such as Bio-Oss and thus some loosening of the original space created by the graft materials, although this theory is still controversial.

However, to the best of the author's knowledge, no histologic study of the sinus floor grafting, using the osteotome technique, and BCB and beta-TCP in the same sinus has previously been reported.

In conclusion, the histologic and histomorphometric result of this report demonstrated close similarity between the quality of the new bone replacing the 2 grafting materials 45 months after grafting into the same sinus of the same patient.

Abbreviations

     
  • ABB

    anorganic bovine bone

  •  
  • BCB

    bovine cancellous bone

  •  
  • Beta-TCP

    beta-tricalcium phosphate

  •  
  • MCBA

    mineralized cancellous bone allograft

Acknowledgments

The author wishes to express his deepest appreciations to Dr Mashadi-Abass from the Department of Oral Pathology, Beheshti Medical Science University of Iran, School of Dentistry for her assistance in histologic and histomorphometric analysis of this study.

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