Prosthodontic management of the hydroxylapatite denture patient: a preliminary report

Histologic Evaluation of Tissue Response to Hydroxylapatite Implanted on Human Mandibles

The tissue response to hydroxylapatite implants was examined histologically in samples taken from four patients three to six months after the material had been used to augment deficient mandibular alveolar ridges. Minimal inflammation was found, but the implants had not induced new hone formation and were instead surrounded by a fibrous connective tissue scar.

Calcium orthophosphates in dentistry

Dental caries, also known as tooth decay or a cavity, remains a major public health problem in the most communities even though the prevalence of disease has decreased since the introduction of fluorides for dental care. Therefore, biomaterials to fill dental defects appear to be necessary to fulfill customers' needs regarding the properties and the processing of the products. Bioceramics and glass-ceramics are widely used for these purposes, as dental inlays, onlays, veneers, crowns or bridges. Calcium orthophosphates belong to bioceramics but they have some specific advantages over other types of bioceramics due to a chemical similarity to the inorganic part of both human and mammalian bones and teeth. Therefore, calcium orthophosphates (both alone and as components of various formulations) are used in dentistry as both dental fillers and implantable scaffolds. This review provides brief information on calcium orthophosphates and describes in details current state-of-the-art on their applications in dentistry and dentistry-related fields. Among the recognized dental specialties, calcium orthophosphates are most frequently used in periodontics; however, the majority of the publications on calcium orthophosphates in dentistry are devoted to unspecified "dental" fields.

Chitosan-based gastrointestinal delivery systems

Chitosan, a natural polymer obtained by alkaline deacetylation of chitin, is non-toxic, biocompatible, and biodegradable. These properties make chitosan a good candidate for the development of conventional and novel gastrointestinal (GI) drug and gene delivery systems. The objective of this review is to summarize the recent applications of chitosan in oral and/or buccal delivery, stomach-specific drug delivery, intestinal delivery, and colon-specific drug delivery. The use of chitosan for targeting of drugs to each of these sites in the GI tract is illustrated by examples supported by in vivo studies. Chitosan appears to be a promising material for GI drug and gene delivery applications as many derivatives and formulations are being examined.

The use of fresh frozen allogeneic bone for maxillary and mandibular reconstruction

The use of fresh frozen bone (FFB) alone, or in combination with autogenous bone (AB), for bony augmentation of the maxilla and mandible in preparation for dental reconstruction with endosseous implants has been studied. Ten patients received FFB +/- AB for augmentation of a severely atrophic mandible (n = 6) or for reconstruction of a jaw defect secondary to trauma or tumor resection (n = 4). Average follow-up was 26.3 +/- 5.4 months. At the time of implant placement, the bone grafts were found to be firm in consistency, well incorporated, and well vascularized in all 10 patients. Twenty-nine endosseous implants were placed an average of 8.3 +/- 3.1 months following bone grafting. One implant failed and was replaced, and one implant remains buried as a nonfunctional unit. All patients have been restored prosthetically by means of 28 of the 29 implants. This preliminary study indicates that FFB may be used alone or in combination with autogenous bone for augmentation or reconstruction of the atrophic maxilla and mandible. The resultant ridge is adequate to support loaded endosseous implants. A potential disadvantage is the minimal risk of disease transmission.

In vitro properties of a chitosan-bonded hydroxyapatite bone-filling paste

A possible bone substitute material for dental treatment was developed and tested. The material is composed of powdered hydroxyapatite (HA), ZnO and CaO, kneaded into a chitosan sol to make a quick-hardening paste. A composition was found which showed neutral pH, short setting time, and relatively high compressive strength. The use of such a paste for the treatment of periodontal defects or the augmentation of edentulous alveolar ridges may alleviate problems now associated with the implantation of particulate HA, such as early migration of particles and recontouring of the implant.

Augmentation of the atrophic edentulous maxilla with hydroxylapatite

A technique for augmentation of the severely atrophic edentulous maxilla is presented. This technique combines the mobilization of the available soft tissue of the labial vestibule with a subperiosteal reflection and "filleting" of the redundant crestal soft tissue to create ample space to accommodate the insertion of the desired amount of hydroxylapatite. The surgical development of a distinct labial periosteal flap by both a subperiosteal and supraperiosteal dissection allows a two-layered lapped closure of the mucosal and periosteal flaps. Fourteen patients were treated with this technique and have been observed for period of 8 to 40 months. Arch form was dramatically improved in all cases. Observation of panoramic radiographs disclosed an average initial increase in ridge height of 11.8 mm in the midline and 7.6 mm in the first premolar regions. During the first 6 months, consolidation of the ridge occurred, but the diminution in ridge height never exceeded 15%.

Surgical and prosthodontic residual ridge reconstruction with hydroxyapatite

The ultimate goal of a ridge augmentation procedure is to form a bearing surface for the denture that will provide stability, retention, and support. Residual ridge reconstruction with an implanted material must be based on an understanding of the variations of ridge atrophy. A problem-oriented classification describes the different forms of residual ridges. This classification of similar types of resorbed residual ridges can be used to establish a rational plan of treatment. The proper placement of hydroxyapatite is critical to obtain the desired reconstructed residual ridge. In the mandible, a lingualized placement of the alloplast is suggested. Careful use of an anatomic matrix to support and contain the hydroxyapatite particles eliminates the need for a splint. The surgical stage includes vestibuloplasty and skin grafting to provide the patient with an increased denture-bearing surface. The ridge created in the form of a comma posteriorly enhances retention and stability. The broad residual ridge with an improved interarch relation also enhances the support and provides a better foundation for balanced occlusion.

Alveolar ridge augmentation with bioactive glass ceramics: a histological study

A particulate BGC (bioactive glass ceramics), has been developed as a new bone graft biomaterial for alveolar ridge augmentation and has been evaluated by simulated animal models. Five beagle dogs were used in this investigation. Prior to augmentation the mandibular posterior teeth of the animals were extracted. Three months after the extractions, the porous BGC particles were packed into the subperiosteal tunnels in the ridges with a special syringe. The animals were killed at different time intervals and the specimens were examined by light microscopy, scanning electron microscopy (SEM), and X-ray energy dispersive analysis (EDAX), respectively. The results of this study indicate that the BGC particles are firmly combined with the adjacent hard and soft tissues by the bone bonding interface between the implants and the alveolar bone, and by the ingrowth of bone or fibrous connective tissue into the interspaces and the pores of the particles. The results have demonstrated that particulate BGC with pores is an excellent implant material for alveolar ridge augmentation because of its very good biocompatibility.

Calcium phosphate materials in restorative dentistry: a review

This report deals with some of the calcium phosphate materials which are currently used in preventive and restorative dentistry and other calcium phosphate materials which have potential for dental and medical applications. Such materials include those which form calcium phosphate in situ (e.g., Bioglass ceramics and calcium phosphate cements) and those originating from natural materials (such as corals and bones).

The reports on the development and current status of the calcium phosphate ceramics and glass ceramics presented here were based on recent reviews and recent evaluations of clinical studies for the period 1975 to 1986 (Table 3) with humans and with animals when reports on human studies were not yet available. Methods of preparation and relevant physico-chemical properties of some of the calcium phosphate materials were based on data reported in the literature and on other studies by the author. New calcium phosphate materials, e.g., calcium phosphate cements, calcium phosphate-coated implants, calcium phosphate/polymer composites, have also been briefly covered in this report.

Based on the information summarized in Tables 1 to 6 and on solicited comments from clinicians and researchers involved with calcium phosphate materials, several areas of basic and clinical research are recommended (Table 7).

Effect of hydroxylapatite, tricalcium phosphate, and collagen on the healing of defects in the rat mandible

The effects of hydroxylapatite and tricalcium phosphate alone or mixed with collagen on the repair of surgically created bony defects in the mandible of 30 rats were evaluated by gross examination and light microscopy. When specimens were examined 4 and 12 weeks after placement of the implants, bone was observed in direct contact with the implants at the periphery; however, in the central portion of the defects, the implants were surrounded by fibrous connective tissue containing macrophages and a few multinucleated giant cells. Neither the hydroxylapatite or the tricalcium phosphate induced bony healing in the defect, and the addition of collagen did not interfere with healing. Because collagen does not alter healing, it might be possible to use it as biocompatible resorbable binder to confine particulate ceramic implants and inhibit their migration.

Autogenous bone grafts for atrophic edentulous mandibles: a final report

While autogenous bone augmentations for atrophic edentulous mandibles are not the ideal solution for this problem, we do not share the pessimism of other investigators. The average loss of bone over the 92-month observation period was 60% for this small sample of eight patients. However, there was an 81% gain in bone height in the premolar-molar regions when compared with presurgical measurements. Seven of the eight patients believed these procedures were beneficial.

Using soft vinyl stents to facilitate augmentation of maxillary anterior atrophic ridges with hydroxyapatite

A technique has been described for fabrication of a surgical template made of soft vinyl mouthguard material. Use of this stent at the time of surgery can be of great value to the oral surgeon and the prosthodontist. The risk of excessive augmentation and migration of the particulate hydroxyapatite to an undesired area will be minimized if the stent is used as a matrix. Uniform results in size and form of the ridge can be obtained from the surgical procedure when the stent is used. The denture-bearing area of the maxillary anterior ridge will improve significantly, enabling the dentist to make a maxillary complete denture.

Collagen tube containers: an effective means of controlling particulate hydroxyapatite implants

HA has been used successfully as a hard tissue graft in alveolar ridge augmentation; however, its particulate nature limits its application to select cases. A study in rats was done to examine the feasibility of a combined system of HA encased in collagen film as a hard tissue graft. Gross, radiographic, and histologic examination showed that collagen film helped to shape and contain the HA particulate during healing for as long as 4 weeks. The collagen did not interfere with the normal tissue response around the HA particulate.

Mandibular augmentation with hydroxyapatite

This study investigated the success of hydroxyapatite mandibular augmentation in nine patients, the histologic response around hydroxyapatite, and the effect of collagen in localizing hydroxyapatite. It can be concluded that hydroxyapatite is biocompatible, causes minimal inflammatory response, and can increase denture retention. However, a large number of patients develop lip paresthesia, and hydroxyapatite migrates. Paresthesia might be avoided by altering the surgical technique to avoid manipulation of the mental nerve, and collagen might be a useful binder to confine hydroxyapatite particles. Further studies are in progress to develop new methods to place the hydroxyapatite and materials to confine it.

Hydroxylapatite alveolar ridge reconstruction: clinical experiences, complications, and technical modifications

Results of the reconstruction of 228 deficient alveolar ridges (208 patients) using hydroxylapatite with or without autogenous cancellous bone over a six-year period are reported. Complications included erosion, mental nerve neuropathy, migration and displacement of particles, overfill, and loose material. Modified techniques are presented that minimize the occurrence of these complications in Class III and IV ridge-deficient patients.

Compressive strength measurement and microstructure studies of hydroxyapatite cones

Compressive strength measurement and microstructure studies of standard, diamond bur-ground, and fracture surfaces of durapatite cones were reported. The compressive strength measurements of durapatite cones were variable and strongly dependent on the test method. The fracture force ranged from 1090 to 3692 N and the calculated compressive strengths ranged from 113 (16,333 psi) to 389 mN/m2 (56,462 psi). The outer surface of durapatite cones was rough, irregular, and dense. Sharp fracture lines occurred along the longitudinal axis of the cones. Isolated porosity was seen in the fracture surface of one specimen. Grinding hydroxyapatite cones using a high-speed diamond bur with water spray produced a surface grinding feature, an irregular surface topography, and microcracks. The microcrack directions were perpendicular to the direction of the diamond bur cutting features.

Hydroxyapatite for alveolar ridge augmentation: indications and problems

The increased use of hydroxyapatite for augmentation of residual alveolar ridges has created some problems in the subsequent fabrication of complete denture prostheses. Although hydroxyapatite appears to be an effective substitute for resorbed alveolar ridges, its use is not indicated for all patients. In addition, the premise that "if a little is good, a lot is better" does not apply. The following conclusions can be drawn. Augmentation should not be considered if vestibular extension will provide acceptable results. Placement of hydroxyapatite should improve the contour and amount of the residual alveolar ridge. Use as little as possible to accomplish the goal. Preprosthetic surgery should permit vertical as well as horizontal extension of the denture. Augmentation should not result in the need to use lining mucosa to support a complete denture. Vestibular extensions are indicated for most augmented alveolar ridges. The relative strength of the strong arch should not be increased in prognathic or retrognathic ridge relationships. Preprosthetic surgery should be a combined surgical-prosthodontic treatment endeavor. If a foundation is created that cannot be used effectively for the support, retention, and stability of an intended prosthesis, little benefit is provided for the patient. Small variations in intended treatment can significantly increase success of the prosthesis (Fig. 13). Unfortunately, the relative ease of hydroxyapatite placement has led to its use in patients who do not require augmentation and augmentation in amounts and regions that are not conducive to improving denture success. A coordinated effort between the surgeon and the prosthodontist will usually result in treatment that provides the best potential foundation for a specific patient.

Repair of anterior gingival deformity with durapatite. A case report

After the extraction of a maxillary anterior tooth, a gingival deformity may occur due to the loss of the labial plate of bone. This often creates an esthetic problem in the construction of a fixed partial denture. In the past, various surgical techniques have been devised to eliminate this gingival defect. A technique using durapatite is discussed.

Hydroxylapatite augmentation of the mandible with simultaneous mucosal graft vestibuloplasty

A technique is described that allows simultaneous posterior mandibular ridge augmentation and anterior sulcus deepening. This combined technique improves the denture-bearing area of the mandible more than vestibuloplasty alone and can be completed as one surgical procedure.

Use of durapatite for the rehabilitation of resorbed alveolar ridges

These investigations were undertaken to evaluate durapatite, a particulate, ceramic, nonresorbable bone-grafting material for augmentation of deficient alveolar ridges. A total of 207 augmentations were reported among 198 patients over 24 months. Subjective and objective data showed that durapatite alone was successful for all classes of ridges augmented; height, bulk, contour, and ridge form generally improved and soft tissue overlying the augmented ridges was firm and immobile. Impressions for dentures usually began 4 to 6 weeks after surgery and these dentures remained stable, retentive, and esthetically pleasing throughout the study. Other than transiently altered sensations resulting from mental nerve manipulation during surgery, no other important procedural complications were noted. No infection or bone resorption beneath the implant was observed throughout these studies. Durapatite used in an outpatient setting provides a less costly and more permanent method for alveolar ridge augmentation than do augmentation procedures using autogenous or banked bone.

Alveolar ridge augmentation using nonresorbable hydroxylapatite with or without autogenous cancellous bone

A four-year prospective evaluation of the use of nonresorbable, particulate hydroxylapatite (HA) to augment deficient alveolar ridges was performed. The material was used alone and in combination with finely crushed autogenous cancellous bone. Implants were delivered subperiosteally by syringe injection, usually using local anesthesia for Class I to Class III ridges and general anesthesia for Class III and Class IV ridges. The improved ridge height and width were stable. Postoperative resorption with significant loss of ridge height, frequently seen with rib and iliac crest onlayed grafts, was not observed with HA augmentation. Permanent denture construction began as early as three weeks postoperatively and by four to six weeks if HA was combined with autogenous cancellous bone. It was possible to place mandibular staple implants simultaneously or following HA augmentation. Visor osteotomy techniques were improved by use of HA to produce a wider, more convex stable ridge. Although skin, mucosa, or dermal vestibuloplasties were performed as early as three months postoperatively in a small number of patients, there appeared to be a lesser need for vestibuloplasty after HA augmentation than after onlay bone grafting. In addition, prosthodontists performed fewer denture relines after HA augmentation than after onlay bone grafts. The authors believe the most significant factor accounting for these observations is the firm, nonmobile mucosal base resulting from augmentation with HA. The resultant stable, soft tissue base and improved ridge height and contour have contributed to a comfortable, retentive, stable denture for these patients. The prosthetic and surgical procedures are easier to perform and have produced superior, more permanent results than onlay bone grafts and alloplasts. Preliminary studies also point to exciting possibilities for use of HA as a bone substitute/marrow extender in maxillary and mandibular defects, cysts, and clefts and in osteotomies for orthognathic surgery.