Mandibular Tissue Research Articles

Oral and dental rehabilitation after mandible reconstruction

Certain criteria in relation to tissue support must be met before the placement of a mandibular prosthesis. These criteria are as follows: (1) adequate lingual and buccal vestibular depth, (2) appropriate load bearing tissues over the reconstructed mandibular alveolar ridge, (3) adequate mechanical and functional tissue retention of the prosthesis, (4) adequate oral opening, and (5) proper alignment of the reconstructed mandible in relation to the maxilla and temporal mandibular joints. The mandibular reconstruction patient may require preprosthetic surgical procedures before oral and dental rehabilitation. The most common of these procedures include vestibuloplasty and dental implant placement. Once the criteria are met, the patient can be restored to function and aesthetics with a fixed or removable prosthesis.

Expression of bone sialoprotein mRNA by cells lining the mouse tooth root during cementogenesis

Adhesion molecules are considered to have an active role in controlling cell differentiation, although the mechanisms involved have yet to be determined. The developing tooth provides an excellent model to use for determining the factors/processes regulating cell differentiation. The studies presented here focused specifically on the timed and spatial expression of a bone-associated adhesion molecule, bone sialoprotein, during tooth root development. Mandibular tissues in the first molar region of CD-1 mice, at sequential stages of development, were analysed by in situ hybridization. The results demonstrate distinct expression of bone sialoprotein in surrounding bone at early stages of tooth development. At stages of active cementogenesis, bone sialoprotein transcripts were specific to cells lining the root surface, with limited expression in the surrounding connective tissue (periodontal ligament) region. The strong expression of bone sialoprotein, a mineral-specific protein having the capacity to act as a nucleator of hydroxyapatite in vitro, by cells lining the root surface at early stages of cementogenesis suggests that this molecule is operative in the cell/matrix events that accompany cementum formation.

ASSESSING THE DURATION OF MANDIBULAR SOFT TISSUE ANESTHESIA

Dentists often employ solutions of 3 percent mepivacaine or 4 percent prilocaine without a vasoconstrictor in pediatric patients in an attempt to reduce the duration of mandibular soft tissue anesthesia. The authors compared the time course of soft tissue anesthesia produced by these solutions with that of 2 percent lidocaine plus 1:100,000 epinephrine in 60 adults. They found no reduction in the duration of soft tissue anesthesia when employing 3 percent mepivacaine or 4 percent prilocaine instead of 2 percent lido-epi. Combining these observations with local anesthetic dosage considerations, the authors recommend that 2 percent lido-epi be used when performing mandibular block injections in young children.

OMENS-Plus: Analysis of Craniofacial and Extracraniofacial Anomalies in Hemifacial Microsomia

This review of 121 patients with hemifacial microsomia (HFM) revealed that 67 (55.4%) had extracraniofacial anomalies. Sixteen patients (13%) had one extracraniofacial anomaly and 51 patients (42.4%) had anomalies of multiple organ systems. There was no gender or side predominance in the cohort with the HFM "expanded spectrum." Central nervous system (CNS), cardiac, and skeletal anomalies were "associated" (i.e., had frequencies of 10% or more). Pulmonary, gastrointestinal, and renal deformities were equivocally associated. Statistical analysis indicated significant associations between several orbital, mandibular, ear, neural, and soft tissue (OMENS) variables and extracraniofacial anomalies. Patients with extracraniofacial structural defects had higher OMENS grades for individual craniofacial anatomic categories. Furthermore, patients with expanded spectrum had higher total OMENS scores. The frequency of cardiac anomalies (26%) supports the model of neural crest involvement in the pathogenesis of both hemifacial microsomia and conotruncal defects. The majority of the heart defects in this study were of either the outflow or septal type. We propose that the OMENS classification system for craniofacial anomalies of HFM be expanded to OMENS-Plus (+) to designate the presence of associated extracraniofacial anomalies.

Use of osteogenic bone-marrow precursor cells for reparative osteogenesis in the mandible of experimental animals

Using a model of “bony tissue tunnel defect” produced by the removal of a mandibular incisor in rats, it was found that closing the defect with a bioprosthesis prevented the washing out of osteogenic bone marrow precursor cells, which serve as a substrate for reparative osteogenesis, from the mandibular spongy bone. The reparative process was strongly stimulated if the bioprosthesis contained estrone; in this case, the time required for the tooth socket to be filled with osteogenic tissue was shortened by half. When no bone marrow elements were present in the socket, it was filled with fibrotic connective tissue, the number of bone marrow elements in spongy bone cavities was small, and the mandibular osteogenic tissue underwent atrophy.

Osteogenesis of the mandibular arch in Ts16 mice

Males and females homozygous for the Robertsonian translocation specific for chromosomes 16 and 17 Rb(16.17)Bnr and male and females homozygous for the Robertsonian translocation for chromosomes 6 and 16 Rb(6.16)24Lub were bred to produce double heterozygotes [Rb(16.17)Bnr/Rb(6.16)24Lub]. Experimental data were based on 156 features: 70 euploid (control), 86 trisomie. Affected fetuses were identified by decreased size, shortened faces (flattened snouts), oedema, petechiae, open eyelids, and dysplastic ears. Identification of trisomies was substantiated by karyotyping the metaphasic spreads. Five gestational days were studied (14–18). Fetal age was assumed to be accurate as fertilization occurred within half an hour of copulation. Euploid specimens followed normal developmental paths of chondrogenesis, osteogenesis and related tissues. In trisomies, developmental faults increased unequally between gestational days 15 and 17: some tissues were mildly and others acutely affected. Among the trisomic disorders were diminished growth, lagging mitotic activity, and retarded and poorly ordered tissue development, especially of bone. All of these contributed to hypoplasia, hypocellularity, reduced vascular supply and enlarged intercellular spaces. Intensities of the mandibular abnormalities varied among litters and littermates. The severity of the developmental disorders of an individual Ts16 specimen differed among the tissue components studied. Of the trisomic mandibular tissues, bone was most frequently involved and Meckel's cartilage least.

Regionally disturbed production of cartilage proteoglycans in malformed fetuses from diabetic rats.

Fetuses from normal and manifestly diabetic rats were obtained on pregnancy day 20. The fetuses from the diabetic rats were of normal or malformed morphology. Three tissue groups were dissected free; costal cartilage, the hard tissue of the rear, and of the frontal portion of the mandible. These tissues were maintained in vitro for 24 h during which time they were labelled with [35S]sulphate. After the culture period the tissues were extracted with guanidine HCl and the resulting residues were further extracted with alkali. The culture medium was saved and its macromolecular content was compared to that of the extracts. The proteoglycans recovered in all extracts eluted at two distinct positions after chromatography on a Sepharose CL-2B column (peak I: Kav approximately 0.4, and peak II: Kav approximately 0.8), but the elution patterns were markedly different in extracts from various tissues. Thus, in rib cartilage, the majority of the labelled proteoglycans were located in peak I (approximately 90%) with no difference between extracts of fetuses from normal and diabetic pregnancies. In extracts of mandibular cartilaginous tissue from normal rat offspring the peak I percentage (60-80%) was lower than in the rib cartilage extracts. In the extracts from the frontal portion of malformed mandibles of fetuses of diabetic rats, the peak I percentage (35 +/- 21%) was the lowest of all recorded and the only one to significantly differ from the other percentages in its (the frontal mandible) group. The results show an association between a congenital malformation, micrognathia, and a disturbance in the production of chondroitin sulphate proteoglycans in the malformed region.

Soft tissue changes associated with double jaw surgery

The purpose of this study was to evaluate the amount, direction, and predictability of the soft tissue changes associated with simultaneous maxillary impaction and mandibular advancement surgery. The results suggested that the soft tissue responses were similar to those seen in single jaw procedures, with the exception of the changes seen in the nasolabial angle and in the area of the lower lip and chin. The type of soft tissue manipulation employed, in particular the use of the alar base cinch suture and V-Y closure techniques, were important factors in determining the response of the upper lip to the surgery. The maxillary soft tissues moved forward 90% of the hard tissue change and showed 20% shortening of the upper lip, with the changes in the nasolabial angle being due primarily to the degree of the maxillary rotation. A predictable progressive increase was seen in the horizontal movement of the mandibular soft tissues ranging from 73% of the hard tissue change at the lower lip to 100% at pogonion. The vertical movement of the mandibular soft tissue was greater than that of underlying hard tissues, particularly in the area of the lower lip as it was freed from the effects of the maxillary incisors. (A M J O RTHOD D ENTOFAC 1992;101:266-75.)

結晶化ガラス（ＣａＯ‐Ｐ２Ｏ５‐ＭｇＯ‐ＳｉＯ２‐ＣａＦ系）人工歯根機能負荷による顎骨組織の組織学的変化に関する実験的研究

The purpose of this study was to investigate the time of change in the reaction between mandibular bone tissue and glass ceramic implants under functional loads.Two months after extraction of P2, P3, P4, and Ml, from the mandibles of 16 adult mongrel dogs, glass ceramic implants were implanted in each side, and the glass ceramic implants were under a functional load three months after implantation. Histological examination and tetracycline labelling of the specimens were made 10 to 300 days after initiation of the function. The results obtained were as follows:At 10 to 30 days after initiation of the function, new bone formation was found around the glass ceramic implant, the new bone increased in thickness and ankylosed, showing a network structure. After 60 to 90 days, there was new bone formation and bone remodeling, after 120 to 150 days, there was a supporting growth of spongy bone tissue, and the new bone was mature. After 300 days, the functional load was around the implant and the mandible bone.The tetracycline labelling method showed strong labelling after 10 to 30 days continuing up to 60 days and then decreasing gradually until 90 days.The results of this experiment confirmed that glass ceramics has high tissue affinity for mandibular tissue and the placement of the glass ceramic implants under functional loads caused no problems around the implant. We established that it is an appropriate material for implants.

Interface between hydroxyapatite and mandibular human bone tissue

Samples from intraosseous dental implants, removed from patients for mechanical failures, were examined to analyse the interaction between hydroxyapatite as plasma sprayed coating on titanium supports and human bone. The implantation time varied up to 8 years. No failures had arisen from problems at the interface between the hydroxyapatite coating and bone. The number of samples examined and the implantation times give good statistical conclusions. Histological and microchemical studies showed the good performance and compatibility of this sprayed hydroxyapatite. We present evidence from the best samples which show close bonding with the surrounding bone tissue. New bone is seen all around the coated implant. The composition of the calcium phosphate deposited on the hydroxyapatite and cellular approach were determined, and demonstrate the efficiency of the interaction between this plasma sprayed hydroxyapatite and the bone.

HVEM studies of the calcified bone interface with endosteal dental implants

Previous studies have suggested the prerequisite of bone interfacing successful endosteal dental implants. This is the concept of osseointegration of dental implants within the jaw. However, the ultrastructure of the actual bone interface is largely unknown. This current study is planned to elucidate with correlative high-voltage electron microscopy (HVEM) and conventional electron microscopy (TEM), the morphology of the interface of the support tissues to endosteal dental implants. All ultrastructural protocols involve undecalcified tissue sectioning.After 2 months healing following extraction of all premolars, 120 root form and blade-type endosteal dental implants were placed into the mandibles of 30 adult mongrel dogs. This report will be restricted to 12 implants retrieved from animals euthanized after 5 months of unloaded healing. Following perfusion with buffered 3% glutaraldehyde the implants were block resected with their encasement of mandibular tissues, fixed by immersion for 24 hr in glutaraldehyde and postfixed with 1% OsO4 for 2 hr.

Parascapular free flaps for head and neck reconstruction

We report our experience with single-stage, primary reconstruction of the head and neck in 29 consecutive patients using parascapular free flaps. The commonest indications were for craniofacial defects (9), oropharyngeal soft tissue defects (10), and combined mandibular and soft tissue losses (4). Ablative surgery was performed for squamous carcinoma (22), melanoma (2), and malignant fibrous histiocytoma (2). Seven patients died of recurrent disease during a 3 1/2 year follow-up. Seven patients are alive with recurrence. Flap complications included total loss (2) due to unsalvageable microvascular thrombosis, wound breakdown with oropharyngeal fistula (2), mandibular osteomyelitis (1), trismus (2), neck contracture (1), and donor site wound dehiscence (1). The overall success of this reconstruction was 93%. Primary wound healing was the general rule with lower morbidity than with other reconstructive techniques. The flap is thin, pliable, and conforms well to three-dimensional defects. The lateral border of the scapula can be incorporated on the same vascular pedicle for single-stage mandibular reconstruction. No muscle is sacrificed, and the posterior donor defect is an added advantage. The parascapular flap is our first choice for reconstruction of major defects in the head and neck.

Orthotopic homotransplantation of vascularized composite mandibular tissue in rabbits immunosuppressed with cyclosporine A

To develop the surgical model, composite mandibular tissue was transplanted at the same site. Revascularization was accomplished by end-to-end anastomosis of the facial vessels using standard microvascular techniques. A total of 33 vascularized composite mandibular tissue allografts were similarly performed between two incompatible strains of rabbit. In a control group of 9 animals, no immunosuppression was administered. All of these allografts were rejected acutely within 10 days after surgery. 7 allograft recipients were immunosuppressed with azathioprine and prednisone at 5 mg/kg.d and 2 mg/kg.d, respectively. Their allografts were also rejected acutely within 10 days. 17 allograft recipients were immunosuppressed with cyclosporine A (CsA). All allografts showed primary wound healing and hair growth and took on normal appearance. 8 of these recipients were given CsA at 5 mg/kg.d i.v. and their allografts were rejected at a mean time of 17.9 days. The remaining 9 recipients given CsA at 10 mg/kg.d i.v. rejected their allografts at a mean time of 36.1 days. In 3 of them, the rejection was reversed with CsA (20 mg/kg.d) injection for five days successfully, and one allograft survived more than 100 days. This pilot study suggests that the surgical model is reliable and that CsA will be useful as an immunosuppressive agent in the study of vascularized composite mandibular tissue allografts.

結晶化ガラス人工歯根埋入による顎骨組織の経時的変化に関する実験的研究

We implanted a glass ceramic dental root implant into the mandible of an adult dog two months after extraction, prepared specimens 5 days to 420 days after implantation, and histologically examined the reaction between glass ceramic and the mandibular tissue with an optical microscope. The result showed that the implant and compact bone were closely attached in the compact bone region 15 days after implantation.We recognized a new bone formation along the implant surface and also numerous osteocytes, 15 days after implantation.We found osteoclasts and a bone resorption image in a part of the bone attached to the implant 30 days after implantation. The resorption image, however, almost disappeared and the implant and compact bone completely ankylosed 60 days after implantation. The bone recovered its original structure 90 days after implantation. There were no changes in osteo-ankylosis of the implant and the bone 420 days after implantation.In the spongy bone region, a new bone beam was formed from the surrounding osseous tissue toward the implant, a part of which attached to the implant from 5 days to 10 days after implantation.We saw a new bone formation along the implant surface from 10 to 15 days after implantation.The bone increases in width showing a network structure near the implant surface and attached to the implant 30 days after implantation. The new bone formed on the implant surface increased in thickness and ankylosed to the implant 60 days after implantation.The bone beam decreased in number and shifted to the original spongy bone appearance while the medullary cavity expanded 90 days after implantation.The osseous tissue was formed in nearly the whole implant surface area and the osteo-ankylotic condition of the implant to the spongy bone was satisfactory 150 days after implantation.Further, there was no remarkable change in the condition until 420 days after implantation.The result of this experiment confirmed that a glass ceramic has a high tissue affinity or osseous tissues around the implant with an excellent osteo-ankylotic condition of the glass ceramic to osseous tissues. Thus, we confirmed that it is an applicable material for implants.

Maxillary chloroma: a myeloid leukaemic deposit

A chloroma is described in the left quadrant of the maxilla in a 4-year-old girl. This patient had previously completed a course of chemotherapy for acute myeloid leukaemia, but had been off all drug therapy and in remission for 1 year prior to presentation. Chloroma is a well recognised, if uncommon, mode of presentation of acute myeloblastic leukaemia and a previous case of chloroma occurring in the mandibular gingival tissues has been reported (Reichart et at., 1984). An unusual feature in the present case is the appearance of the chloroma as a form of leukaemic relapse and as a solitary deposit which is itself uncommon in acute myeloblastic leukaemia. It is suggested that this chloroma was a leukaemic deposit which had spread from within the maxillary antrum or the tissues adjacent to the meninges.

The influence of functional stress on the mandibular tissue around the apatite implant

To observe the effect of the apatite implant on the functioning jaw bone structure, we conducted an experiment. In the lower jaw bone (the sites corresponding to P3, P4 and M1) of adult dogs whose teeth were extracted several months ago, 3 or 4 pieces of 2-piece apatite implant each of the same size as the extracted one were placed on one side and the sites on the other side were left as they were extracted as controls. At about 4 months after the implants were placed, an occlusion having a normal vertical height was given to each implant and at 1 month and 10 months after occlusion began, specimens were taken for histological observation of the tissues surrounding the implants and around the control sites.Simultaneously, the sites on the implant-placed and control sides were compared and their the changes with time were also studied. As the result, the jaw bone with the sites left as they were after extraction tended to atrophy. But, the jaw bone on the functioning side showed various changes resulting from accommodating itself to the functional pressure applied to the implants. It was also observed that these changes were associated with the bone structure both in the implant-placed and opposite regions.

手術時における下歯槽神経保存の適応と限界

The pathology of mandibular nerve tissue underlying mandibular diseases was investigated on the basis of operative findings and histopathological observation of raected specimens to clinically determine the surgical limitations topreservation of the inferior alveolar nerve. The study was performed on 14 patients with cyst, 28 with tumor (19 benign and 9 malignant tumors) and 8 with osteomyelitis. Benign tumors consisted of 11 cystic type ameloblastomas, 5 solid type ameloblastomas, 2 myxofibromas and 1 cementoma. Osteomyelites consisted of 5 chronic osteomyelites of the lower jaw and 3 radiation osteomyelites.In cystic diseases, though nerves were frequently compressed to the cystic wall, the inferior alveolar nerve was distinctly separated from the cyst without any histopathological abnormality of the nerve tissue, indicating that preservation of the inferior alveolar nerve was possible. In cystic type ameloblastomas, despite marked compression of the nerve tissue by severely developed tumors, the tumor and nerve tissue were clearly demarcated. Notwithstanding histopathological evidence of minor fibrosis around the epineurium, no abnormal pathology existed in the nerve tissue, indicating the possibilityof preservation. In solid type ameloblastomas, the nerve tissue was surrounded by the tumor with partial adhesion, which precluded preservation. In rnolignant tumors, severe fibrosis and hyalinization were histopathologically found to surround the nerve tissue. Preservation was impossible because of severe perineurial adhesion to the surrounding fibrous connective tissue, close contact with the tumor and tumor infiltration. In osteomyelites, macroscopical changes were demonstrable, and histopathological examination disclosed severe fibrosis around the nerve tissue and also severe hyalinization and degeneration along the perincurium. Preservation also proved to be impossible.

Epithelial-mesenchymal interactions in the development of chick facial primordia and the target of retinoid action.

The development of the chick face involves outgrowth of buds of tissue, accompanied by the differentiation of cartilage and bone in spatially defined patterns. To investigate the role of epithelial-mesenchymal interactions in facial morphogenesis, small fragments of facial tissue have been grafted to host chick wing buds to continue their development in isolation. Fragments of the frontonasal mass give rise to typical upper-beak-like structures: a long central rod of cartilage, the prenasal cartilage and an egg tooth. Meckel's cartilage, characteristic of the lower beak, develops from fragments of the mandible. Removal of the ectoderm prior to grafting leads to truncated development. In fragments of frontonasal mass mesenchyme only a small spur of cartilage differentiates and there is no outgrowth. The mandible is less affected; a rod of cartilage still forms but the amount of outgrowth is reduced. Retinoid treatment of chick embryos specifically affects the development of the upper beak and outgrowth and cartilage differentiation in the frontonasal mass are inhibited. The mandibles, however, are unaffected and develop normally. In order to investigate whether the epithelium or the mesenchyme of the frontonasal mass is the target of retinoid action, recombinations of retinoid-treated and untreated facial tissue have been grafted to host wing buds. Recombinations of retinoid-treated frontonasal mass ectoderm with untreated mesenchyme develop normally whereas recombinations of untreated ectoderm with retinoid-treated mesenchyme lead to truncations. The amount of outgrowth in fragments of mandibular tissue is slightly reduced when either the ectoderm or the mesenchyme has been treated with retinoids. These recombination experiments demonstrate that the mesenchyme of the frontonasal mass is the target of retinoid action. This suggests that retinoids interfere with the reciprocal epithelial-mesenchymal interactions necessary for outgrowth and normal upper beak development.

Effects of dextrans, heparin and hyperbaric oxygen on mandibular tissue damage after osteotomy in an experimental system

The effect of heparin, dextran 40, dextran 70 and hyperbaric oxygen (HBO) therapy to reduce tissue damage after mandibular osteotomy was tested in an experimental system. Tissue damage was recorded morphologically and blood flow and vascular bed was determined by isotope techniques. Subcutaneously administered heparin reduced morphologically determined tissue damage in the incisor odontoblastema, pulp and ameloblastema. Furthermore, central and peripheral bone damage was prevented by heparin. Dextrans had no preventive effect on tissue damage. HBO treatment reduced tissue damage in a similar manner to heparin but also induced reparative events as osteodentin formation in pulps and chondroid reactions in bone. Effects on blood flow and vascular bed provided a basis for a possible role for HBO and heparin treatment in tissue damage after osteotomy.

The induction of odontogenesis in non-dental mesenchyme combined with early murine mandibular arch epithelium

First and second branchial arches were dissected from mouse embryos of 9–13 days gestational age. The epithelial and mesenchymal components were separated after enzymic digestion. Scanning electron microscopy did not reveal a dental lamina along the dental arches before day 12, after which the lamina was formed locally in the incisor and molar regions. There was no epithelial down-growth in the diastema region. Heterotypic recombinations of mandibular arch and second branchial arch tissues showed that early mandibular arch epithelia, before day 12, have odontogenic potential and can elicit the formation of a dental papilla in non-odontogenic, neural-crest-derived mesenchymal cells of the second arch. However, the mandibular mesenchyme must interact with mandibular epithelium in order to have the competence to induce teeth in non-odontogenic epithelium.