Autogenous Dentin With Calcium Sulfate as Graft Material: A Case Series

Regeneration of atrophic osseous jaw ridges is a routine issue in oral implantology. There is a panoply of autografts and allografts available for osseous augmentation.^1,2  Autogenous bone is an essentially ideal augmentation material but there needs to be a second surgical site, which increases morbidity risk.^1,2  Bone augmentation healing basically enables osteoconduction and osteoinduction.^1,2  Some allografts may be osteoinductive by containing inductive cytokines.^1,2  The primary function of a graft material is to maintain space for bone regeneration.^1,2  Nonetheless, an autogenous graft material may be an important material for bone augmentation. A patient's own tooth may be appropriate for autogenous particulate graft material. Such a material would have no immune response and the retrieved particulate material is enough to fill the socket that it previously occupied.

Recent reports have advocated the use of fragmented autogenous tooth root for use as a graft material.^1–15  A tooth is extracted from the patient and prepared immediately by fragmentation. Infected or endodontically treated teeth may not be used due to the risk for infectious material being transferred to the surgical site with the tooth structure. The ground tooth structure provides an immune compatible particulate for osseous grafting.²  A small amount of enamel may be included in the harvested tooth structure but the primary material for grafting is tooth root and that is made of dentin.² 

The objective of this research is to add to the evidence for use of autogenous dentin as an osseous graft material.

A noninfected tooth is extracted, and all caries, cracks, and stains are removed. The pulp space and any canals are removed. The apical 4 mm is removed to prevent apical vascular tissue incorporation and to eliminate any possible cellular pathology or pathogens. Periodontal attachment and cementum are removed as well as partial removal of root soft tissue. The tooth can be cut into smaller pieces and placed in the pulverizing chamber. These fragments are then pulverized into small granules. The size of the granules can vary from 300 microns to 1200 microns, depending on the proprietary unit used. The granules are then rinsed in aqueous sodium hydroxide and buffered saline to remove cell debris. The granules are then blotted dry with a sterile gauze sponge and can be immediately used as a graft material.

The extracted tooth is sectioned into 1–2 mm segments and placed in the handheld pulverizing unit (Medentra, Sialkot, Pakistan) (Figure 1). The segments are then hand ground by manually turning the handle. The blades cut through the tooth pieces, fragmenting them. The tooth pieces placed in the grinding chamber must be small enough to allow the blades to cut through them with manual force. Large pieces may be too difficult to cut with manual strength and should be cut down to smaller pieces. The resulting ground particles are then rinsed with aqueous sodium hydroxide and buffered saline and dried with a sterile gauze sponge for immediate use. The resulting particles will probably not be consistent in size. Some are tiny, about 0.2 mm, and some are large, about 1 mm. When cutting the tooth into small fragments, drilling small holes into the tooth with a #330 burr facilitates the fragmentation process. The device is then cleaned and autoclaved for reuse. Refer to the manufacturer's instructions before use.

Another system available is an electrically driven grinder (Smart Dental Grinder, Integrated Dental Systems, Englewood Cliffs, NJ) (Figure 2). The extracted tooth is not segmented but all stains, caries, cracks, restorations, and debris are removed. The prepared tooth is blotted dry and then placed in the grinding chamber and pulverized with electrically driven blades for 3 seconds, then sorted for 20 seconds. A side tray accepts the resulting pulverized tooth (300–1200 microns). There are two particles sizes produced, about 300 microns and about 1200 microns, that are delivered in two different drawers. If the particles do not satisfy the clinician, regrinding is appropriate. The particles are then transferred to a surgical dish then rinsed with proprietary sodium hydroxide/ethanol and then buffered saline and dried for use. The particles are somewhat consistent in size, about 0.25 mm. The pulverizing chamber cannot be sterilized so reuse is not recommended. Replacement chambers are provided by the manufacturer for each case. Refer to the manufacturer's instructions before use.

The cases reported herein are a retrospective of routine cases treated in a private general dental practice.

1. Ridge preservation. A 58-year-old male (TM) sustained a lingual fracture of the maxillary right second molar to the osseous socket margin. The tooth was deemed unrestorable. He took metformin 500 mg, omeprazole 40 mg, lisinopril 20 mg, and aspirin 81 mg daily. The patient is a well-controlled type 2 diabetic with a HbA1c of 6. The prospective procedure was delineated, and informed consent obtained. The tooth was locally anesthetized with articaine 1.6 cc (Septocaine, Septodont, Lancaster, PA) infiltration at the facial and palatal. The tooth was sectioned according to the 3-root anatomy, removed, and the socket debrided. The tooth root fragments were debrided of debris, stain, caries, and pulp (Figure 3). These fragments were ground in a hand grinder (Medentra), pulverized, rinsed with sodium hydroxide solution, then buffered saline and dried with a sterile gauze sponge (Figure 4). The pulverized dentin was mixed with calcium sulfate (80:20), then loaded into a 1-cc syringe and delivered to the tooth socket and lightly packed (Figure 5). A collagen barrier membrane (Ossix, Datum Dental, Israel) was then festooned and placed over the site and retained with 3–0 chromic gut suture (Hu-Friedy, Chicago, IL). The site was allowed to heal, and the ridge thus preserved for future treatment (Figure 6). After 21 months a bone core biopsy was performed (University of Connecticut, Department of Oral Pathology, Farmington, CT) (Figure 7). Elements of viable reactive bone and trabecular bone with osteocytes (Figure 7.1), reversal lines (Figure 7.2), and intervening fibro-adipose marrow (Figure 7.3) were seen. There was no remnant dentin found. The pulverized dentin graft material apparently had been resorbed and replaced with bone.

2. Immediate implant placement. A 75-year-old male (JK) sustained a fracture-to-the-gingiva of the maxillary right cuspid (#6). The patient took no medications except 1000 mg of vitamin C daily. The tooth was deemed unrestorable, options were discussed, and informed consent obtained. The tooth was extracted under local infiltration anesthesia (articaine, Septocaine, Septodont) by sectioning mesial distally and the site debrided. The tooth was fragmented and placed in a hand grinder for pulverization. The pulverized dentin was then rinsed with sodium hydroxide and buffered saline and dried. An immediate implant was placed in the site (3.2 × 16 mm, Implant Direct, Ventura, CA) to 40 ncm. An impression was immediately taken with a fast-set polyvinyl siloxane (First Quarter, Darby Dental Supplies, Jericho, NY). The pulverized dentin with calcium sulfate (80:20) was then placed in the socket to surround the implant with the graft material. A collagen barrier membrane (Ossix, Datum Dental) was then festooned and placed over the site and contained with a 3–0 chromic gut suture (Hu-Friedy) (Figures 8 and 9). The patient was administered intraoperative 1000 mg amoxicillin and postoperative 400 mg ibuprofen (Advil) and 650 mg acetaminophen (Tylenol). The sutures were removed a week later. The healing was checked at the eighth postoperative week and found to be appropriate. After 4 months the gingival overgrowth was removed, and an abutment was torqued (32 ncm) into place and a porcelain fused to the noble alloy crown was cemented with a resin modified glass ionomer (RelyX, 3M). It has been in uneventful function for 10 months.

3. Multiple immediate implant placement. A 62-year-old male (CG) patient fractured the mandibular left cuspid. The remaining mandibular incisors were carious with a poor prognosis. His medical history was unremarkable. Treatment options were discussed, and a definitive plan derived. Informed consent was obtained. Subsequently, the anterior mandible was locally anesthetized by infiltration with articaine (Septocaine, Septodont), the left cuspid and incisors were simply extracted, and the sockets debrided. The teeth roots were processed for pulverization in an electric grinder and pulverized (Smart Dental Grinder, Integrated Dental Systems). The ground dentin was rinsed with sodium hydroxide and buffered saline and dried with a sterile gauze sponge. While the teeth were being pulverized, immediate implants (#0.2 × 10 mm, Implant Direct) were placed in sites #23 and #25 (Figure 10). The dentin particles were mixed with calcium sulfate (80:20) and the sockets filled with the dentin: calcium sulfate graft mix. A collagen barrier membrane (Ossix, Datum Dental) was placed with 3–0 chromic suture to contain the surgical site for healing (Figures 11 and 12). The site was checked at 1 and 8 weeks and found to be healing well. After 4 months, a fixed partial denture was cemented on the two torqued (32 ncm) abutments of the two supporting implants. The patient has been in uneventful function for 20 months (Figure 13).

4. A 57-year-old female (CP) dental implant patient took warfarin to prevent a deep vein thrombosis. Her international normalized ratio was 2.5. She was suspected to have an interleukin 1 polymorphism type periodontitis with chronic bone loss although no genotype testing was done. The mandibular right molar (#30) was missing, and the mandibular right second molar (#31) was mobile (Miller 2). The patient wished to restore function on her right side. A higher failure rate was explained to the patient due to the periodontitis. After options were reviewed and informed consent was obtained, implant treatment was decided. After preoperative preparation and a mandibular right block was obtained, #31 was easily extracted and the site thoroughly debrided. Implants were placed in sites #30 and in the mesial root space of #31. The extracted tooth #31 was prepared for pulverization and pulverized with a handheld grinder (Medentra). The particles were then mixed with (80:20) calcium sulfate and placed in the socket to fill the void and to cover the implant. Calcium sulfate was added to top off the fill. A collagen barrier (Ossix, Datum Dental) was used to contain the site and held with 3–0 chromic suture (Hu-Friedy) (Figure 14). Bleeding had completely ceased on completion of the procedure. The site was allowed to heal with follow-ups at 8 and 14 weeks. After 4 months' integration period, a 2-unit, splinted, porcelain fused to noble alloy, fixed partial denture was fabricated and installed with resin-modified glass ionomer cement (Rely X). She has had satisfactory function for 27 months.

5. A 67-year-old male patient (JF) with well-controlled type 2 diabetes (HbA1c: 6.5) had a first premolar removed and immediate implant placement and any gaps were filled with pulverized autogenous dentin (Smart Dental Grinder, Integrated Dental Systems) and calcium sulfate (80:20) (Figure 15). An implant was also placed at healed site #30. A 3-unit fixed partial denture (#28-29-30) was fabricated and delivered. The denture has been in uneventful function for 22 months (Figure 16).

6. An 88-year-old male (CP) fractured the maxillary left first molar and was deemed unrestorable. Options were discussed, and informed consent obtained. He took simvastatin 46 mg, atenolol 80 mg, aspirin 325 mg, fish oil, and a multivitamin daily. The first molar was extracted atraumatically by sectioning and then socket debridement. The roots were removed of any debris, stain, caries, and pulp. The roots were then sectioned for pulverization, pulverized, and chemically treated in the usual fashion (Medentra). An implant was immediately placed (Implant Direct) in the inter-radicular bone pyramid of the extraction socket. An impression was also immediately taken with a fast-set polyvinyl silane (First Quarter). The pulverized tooth particles, mixed with calcium sulfate (80:20), were placed in the site and contained with a collagen barrier membrane (Ossix, Datum Dental) and 3–0 chromic (Hu-Friedy). After 4 months' healing the implant was restored with a full porcelain fused to noble alloy crown. There has been uneventful function for 22 months (Figure17).

7. An 84-year-old female (JF) fractured #8 and #9. These teeth had suffered a traumatic injury at a young age and over the years sustained vertical and coronal fractures that rendered them unrestorable. After a discussion, the patient agreed to extraction and implant restoration. The teeth were subsequently atraumatically removed, preserving the facial cortical plate. Immediate implants were placed (3.2 × 13; Implant Direct) and impressed, and gaps at the facial were filled with processed, pulverized, autogenous dentin (Medentra) mixed with calcium sulfate (80:20) and placed in the gaps and covering the implants. Healing was checked at the first and eighth week and found to be appropriate. After 4 months of healing, the crowns were definitively cemented (RelyX, 3M). After 20 months of function there was no peri-implantitis nor other complications (Figure 18).

All patients were grafted with pulverized autogenous tooth dentin. All implants were successfully integrated and performed well under function.

There is an ongoing quest for the ideal graft material for oral surgery. Allografts, alloplasts, and autogenous bone have been used. Now, autogenous pulverized dentin may be added to this list.

Autogenous bone is considered by some to be the “gold standard” of osseous grafting.⁴  Autogenous bone material requires a second surgical donor site with its own set of morbidities. Autogenous bone may undergo severe late resorption.⁴  Autogenous dentin may be a better option depending on the results of long-term studies yet to be done.

Dentin has a composition similar to bone. Bone is composed of 10%–20% water, 10%–30% collagen, and 60%–70% mineral.¹  Dentin is composed of about 22% water, 33% collagen, and 45% mineral.¹ 

Dentin has calcium phosphate apatite as the mineral component. This mineral, octacalcium phosphate [Ca₈H₂(PO₄)₆ H₂O] (OCP) is an alloplast for alveolar bone grafting.¹⁶  OCP is a mineral metabolite in the formation of human dentin.¹⁶  Synthetic OCP has been shown to have osseous regenerative properties.¹⁶  OCP contains a substantial water component and an apatite chemical structure.¹⁶  It is easily metabolically and irreversibly converted to apatite.¹⁶  OCP induces local biochemical changes such as adsorption of serum proteins and induction of calcium and phosphate ionic concentration that are bioactive for osseous formation.¹⁶  Any OCP that may remain unchanged in autogenous dentin may be readily converted to apatite in a graft site.

The dental pulp contains stem cells and undifferentiated neural crest-derived cells that may be included in the tooth material pulverized for a graft.⁴  A study in rats demonstrated that pulverized teeth produced a similar amount of bone regeneration as iliac donor bone.⁴  These authors concluded that particulate tooth material may be an acceptable alternative to autogenous bone for treating alveolar bone defects.⁴  This study included dental pulp in the pulverization process. Dental pulp contains stem cells that may have osteogenic potential. These tissues need to be separated for testing to see which is the more potent bone former. Nonetheless, this study was done in rats and animal studies should not be extrapolated to human use.

Dental ankylosis is often seen after replantation of an avulsed tooth. There may be osteo-inductive cytokines that induce the ankylosis from dentin that could release bone morphogenic proteins that may induce bone formation.⁵  Nonetheless, a study by Al-Asfour et al in rabbits demonstrated that very minor amounts of heterotopic bone formation occurred after human dentin was placed in rabbit muscle connective tissue.⁵  Thus, dentin may not be able to induce significant bone formation in nonosseous sites in rabbits.⁵ 

The osteoinductive potential of demineralized human dentin matrix was studied in mice.⁶  Demineralized human dentin matrix implanted into the subcutaneous tissue of mice. The demineralized dentin matrix induced bone and cartilage formation independently in the murine soft tissues. There were osteoblasts and fibroblasts found at 2, 4, and 8 weeks in the surgical site. So, demineralized human dentin matrix may have osteoinductive ability and may have an autogenous graft function as found in this study in mice.⁶ 

A dog study of demineralized dentin matrix (DDM) fixed with recombinant human bone morphogenetic protein-2 (rhBMP-2) was done by Kim et al.¹³  Bone defects were grafted with DDM-rhBMP-2. Histological examinations that were done at 4 weeks showed 33% new bone compared with the autogenous bone graft of 52%. At 12 weeks there was 48% with the DDM and 75% new bone at autogenous sites. There was only 6.2% of residual unresorbed dentin that remained. The authors concluded DDM to be osteoconductive and osteoinductive.¹³ 

An evaluation of the healing of xenogenic demineralized dentin onlay grafts was compared to autogenous bone grafts in rabbit tibia.¹⁷  Both grafts had similar resorption after 12 weeks. New bone formation was found at the interface of the dentin graft and in situ natural bone.

Demineralized dentin can induce heterotopic bone formation.⁹  A study by Lee et al evaluated the effect a demineralization process for human dentin using vacuum ultrasonic power for use as an autogenous graft material in human alveolar defects. The processed dentin did indeed produce successful grafts.⁹  Since the demineralization process took a minimum of 2 hours, this technique may not be practical.

A retrospective human study by Kim et al compared the amount of bone resorption around implants between an autogenous tooth graft in bone and a synthetic bone graft for crestal approach sinus floor elevation with simultaneous implant placement.⁷  The authors found that autogenous pulverized teeth may be a good alternative graft material to a synthetic bone graft in sinus floor elevations.⁷ 

One report reviewed the long-term clinical outcome of using demineralized dentin matrix in 5 cases that were first reported in 2010.⁸  Cone beam computerized tomograms were used to measure the resulting bone volume after ridge preservation surgery and implant placement. Volumetric measurements were taken after more than 5 years of healing and function. Histological evaluation was also done. It was found that there was corticocancellous bone formation and it was stable over a 5-year time-period.⁸ 

Another Kim et al human study prospectively evaluated the clinical efficacy and histological outcome of autogenous tooth grafting (ATG) compared with anorganic bovine bone in postextraction alveolar bone augmentation in 33 human graft sites.¹⁰  They found that ATG from extracted teeth grafted to extraction sockets for the augmenting vertical dimension was as effective as anorganic bovine bone with similar implant stability and histological new bone formation.¹⁰  Thus, ATG may be an option for alveolar bone augmentation after dental extraction.

Yet another Kim et al human study of demineralized dentin matrix block found it provided a 3-dimensional scaffold and was incorporated well into the recipient site.¹³  There was little marginal bone loss after an average of 44 months of follow-up.

A review article by Um et al found that demineralized dentin matrix was osteoinductive and osteoconductive, efficacious, and safe for human use.¹⁸ 

Autogenous dentin particulate placed immediately into extraction sockets was found to be useful for socket preservation.^14,15  Calvo et al concluded that it protects the facial and lingual cortices and can help generate new woven bone formation after 60 days and lamellar bone after 90 days healing. Particle sizes were processed and separated at 300 and 1200 micron diameters using a proprietary device for pulverizing and separation of the particles (Smart Dentin Grinder, Integrated Dental Systems, Englewood Cliffs, NJ). No significant difference was found in bone formation between the two sizes.^14,15  The primary function of any particulate graft material is to maintain space for angiogenesis and osteogenesis. Thus, particulate size should provide gaps large enough for capillary ingrowth.¹⁹  Pulverized dentin, as with any particulate, should provide such spaces for angiogenesis and subsequent osteogenesis.

In an observational study by Schwarz et al, 14 patients had lateral augmentation of postextraction facial cortical deficient augmentation with autogenous dentin. It is important to note that the dentin was not harvested from infected teeth. The sites were primarily closed for 26 weeks of healing. All patients had successful implant placement. The authors concluded that autogenous dentin may be a feasible material for augmentation of deficient extraction sites for 2-stage dental implant treatment.² 

Since the dentin taken from the patient is autogenous, there should be no rejection immune response. The mineral portion of dentin would probably not produce an immune response and the autogenous collagenous organic polymers would not be expected to induce an antibody attack.²⁰ 

Infected donor teeth should not be used to graft osseous sites. An endodontically treated tooth is generally not a candidate for grafting material to avoid the risk for bacterial inoculation of the surgical site. Removal of potentially infected dentin may be done prior to pulverization, but complete debridement may be unlikely in endodontically treated teeth. Endodontically treated tooth dentin may contain penetrating pathogenic bacteria so these teeth probably should not be used as graft material.²¹  Bacteria have been known to penetrate dentin; thus, if this dentin is used as a graft material, it may inoculate the surgical site.²¹ 

Cracked teeth may be colonized by oral pathogens migrating from the oral cavity into the crack. Thus, a crack fissure should be debrided by cutting into and removing this dentin. Unrestorable fractured teeth that have pulpal exposure may be candidates if necrosis has not advanced to the tooth apex. However, dentin penetrating bacteria may be an issue. Thus, the pulp chamber and canal space should be excavated and debrided. Endodontic files and piezo drills may be used to accomplish this. The pulverized dentin is chemically treated before use but there is no assurance that all pathogens are completely removed or killed. Autoclaving suspicious dentin may be appropriate, but it is not known if any biological activity would be negated by autoclaving. One study in dogs used autoclaved autogenous dentin blocks for bone grafting.³  The authors found that autoclaving tooth root prior to grafting reduces “healing capacity.”³ 

Removal of the 4-mm apical cone of the donor tooth may be prudent. The tooth apical delta has vascular intricacies and complete debridement may be unlikely.²²  Thus, simple removal of the tooth apex may be best. Molars have more apical delta intricacies (15.8%) than anterior teeth (6.3%).²²  The mesiofacial roots of maxillary molars have a much higher incidence of apical delta intricacies than the palatal roots or the distofacial roots. While tooth apices have their complex channels in the apical 3 mm, about 13% may extend to more than 3 mm.²²  The diameter of these apical vascular branches can be as large as 934 microns.²²  These small channels could contain pathogens that could colonize a graft site. Thus, removal of the apical 4 mm may be most appropriate.

The resulting pulverized dentin particle size ranges between 300 and 1200 microns. The upper range is more than 0.1 millimeter. The dentin can be repeatedly pulverized to reduce the particle size. Nonetheless, large particles, up to 2 mm or 2000 microns, may better promote osteogenesis by allowing larger spaces for the preceding angiogenesis.²³ 

Demineralization of dentin is done by treating the dentin with acid for 6 hours.²⁴  It is yet to be seen if demineralized or nondemineralized dentin is the better graft material.²⁴  The tooth structure treated in the aforementioned protocol is not demineralized. Sodium hydroxide used in processing is a strong base and would not demineralize dentin or enamel.

As with any other immediate graft placement, a barrier membrane is used to contain the graft material and to minimize debris entry and fibrous invasion. The barrier is placed so that the margins are placed on the socket margin bone. The barrier margin should be at least 2 mm beyond the socket marginal bone. If a cortex is missing, the barrier should extend to the base of the defect.^25,26 

Calcium sulfate that was mixed with the autogenous dentin is quickly resorbed in about 8 weeks. It is resorbed before any allograft material and does not induce inflammation.²⁷  Since the primary function of graft material is to maintain space vascular sprouting for angiogenesis and subsequent osteogenesis pulverized dentin can meet this requirement.^28,29  Calcium sulfate does not provide such space and only acts as a calcium reservoir and inhibitor of fibrous invasion.³⁰ 

The graft in Case #1 showed complete dentin resorption and osseous replacement after 21 months. The dentin–bone replacement may occur in as little as 4 months.¹¹ 

The cost differential between dentin pulverizing devices is significant and may be taken into account, as well as the cost of consumable materials.

Autogenous pulverized dentin may potentially be used as a bone graft material as an alternative to autogenous bone or allograft or alloplast. Further study is needed to define the parameters for autogenous teeth as graft material.

The author reports no financial or political affiliations.