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PubMed1999

Ceramic-coated implant systems.

Practitioners have used hydroxyapatite-coated (HA-coated) endosseous and subperiosteal implants in various forms for many years. These have included root forms in both screw and cylindrical shapes, blades, and subperiosteals. The clinical predictability remains controversial and subject to claims and counterclaims. The early days of dental implantology involving root-form implants recommended their placement in fully edentulous cases only, and anterior to the maxillary sinus and mental foramen. Today's philosophy and rationale of dental implantology include the placement of a single implant replacing a missing natural tooth (especially where the teeth adjacent to the edentulous site have no caries or restorative experience). Implants are used to replace the natural dentition in one quadrant/segment, often preceded or accompanied by ridge augmentation and/or sinus grafting if sufficient bone is not present. So we have to address the clinical predictability of survival in terms of indications, quantity, and quality of bone. Clinical data and experience suggest that hydroxyapatite-coated (HA) dental implants may (and possibly should) be used in (1) Type IV bone, (2) fresh extraction sites, (3) grafted maxillary and/or nasal sinuses, or (4) with short implants (< or = 10 mm in length).

Alveolar Process↗
PubMed1991

Reliability of hypocycloidal tomography for the evaluation of the distance from the alveolar crest to the mandibular canal.

When implants are to be inserted in the mandible posterior to the mental foramen, tomography is required to determine the exact location of the mandibular canal and assess the dimensions of the body and alveolar process. Previous studies have shown discrepancies between the true distance between the alveolar crest and the upper border of the mandibular canal and that measured from computed tomograms. This study evaluates the reliability of such measurements made from hypocycloidal tomograms. Six examiners, three radiologists and three oral surgeons, independently measured the distance from the alveolar crest to the upper border of the mandibular canal in transverse hypocycloidal tomograms of the mandible. Analysis of variance showed an average standard deviation between observers of 1.33 mm. This variation, which is the total of inter- and intra-observer variation conditional upon patient and radiograph, was mainly due to the latter which amounted to a mean of 1.04 mm. Calculation of lower confidence limits showed that these could be decreased by the use of several observers. Various confidence levels, equal to the probabilities of obtaining lower confidence limits which are below the true values, can be used to choose acceptable levels of risk in overestimating the true distance.

Alveolar Process↗
PubMed1996

Effect of head positioning in panoramic radiography on vertical measurements: an in vitro study.

OBJECTIVE: To assess whether it is possible to make accurate vertical measurements of the jaws from panoramic radiographs. METHODS: Five dry skulls were shifted 5 mm forwards and backwards and tilted 5 degrees up and down in the sagittal plane. Panoramic radiographs of each skull were obtained in nine different positions. In the maxilla, three reference lines were used and vertical measurements were made at the distal surfaces of the first premolar and first molar and in the midline. In the mandible, measurements were made at the distal surfaces of the first premolar and first molar, and at the mental foramen on both sides, and in the midline. The points and lines were marked manually and the radiographs were digitized, magnified and measured. RESULTS: Sagittal shifting and tilting had only a slight effect on measurements in the mandible. Sagittal tilting of the head had the greatest effect on all the measurements made from the line between the articular eminences to the alveolar crest, as well as measurements in the maxillary midline. CONCLUSIONS: The line between the articular eminences is unsuitable as a reference line for measurements of the tooth-bearing areas. A slight misalignment of the head does not significantly affect the vertical measurements in the mandible or of the posterior maxilla if the reference lines are in the same vertical plane as the teeth.

Analysis of Variance↗
PubMed2005

Accuracy of measurements of mandibular anatomy and prediction of asymmetry in panoramic radiographic images.

OBJECTIVES: Measurements of ideally positioned and systematically mis-positioned skulls were used to evaluate errors in linear measurements and symmetry ratios made with panoramic X-ray images. METHODS: Digital panoramic images of 30 skulls placed in ideal, shifted and rotated positions, were assessed by measuring distances between anatomic points and fiducial references. Differences between photographic measurements (control) and radiographic measurements were compared. Horizontal measurements included a 20 mm wire and the distance from gonion to mental foramen (G-MF). Vertical distances measured included a 40 mm wire, condyle to sigmoid notch length, and condyle to gonion (posterior mandibular height or PMH). A relative symmetry ratio comparing the difference between right and left PMH was also calculated. Distances measured in panoramic images were corrected using the left vertical wire distance or the panoramic unit's stated magnification factor (1.25x). RESULTS: Greatest differences were noted for horizontal measurements and shifted skull positions. Use of an arbitrary magnification correction was consistently less accurate than use of an internal calibration and resulted in general underestimation of actual dimensions. Measures of PMH varied significantly from expected values for each of the three skull positions (P<0.005). Panoramic accuracy for detecting asymmetry was 67% for ideal, 70% for rotated, and 47% for shifted skull positions when an internal reference was used. CONCLUSIONS: Panoramic radiographs should be used with caution in making absolute measurements or relative comparisons. Even when internal fiducial calibration for image distortion of anatomy is used, measurements such as those assessing posterior mandibular facial symmetry may be unreliable.

Cephalometry↗
PubMed2005

A 24-year retrospective study of bone growth after implant placement.

This study quantifies the changes in bone height noted in the body of the edentulous mandibles when the load of the complete denture is born by an RA Ramus Frame Implant (Pacific Implant, Rio Dell, Calif). Eighty-three patients with implants were followed for 3 to 24 years. Pre- and postoperative panoramic films were taken and again at each succeeding 5-year follow-up. The results of the bone changes were gathered retrospectively and calculated. The data revealed a significant increase in bone height from 4.413 to 13 mm and statistically significant P values of <.0003 were determined. The growth of bone appears to be influenced by the design of the posterior feet, dominant chewing side, and a range of extreme atrophy from 5.9 mm to 15 mm. Also, the previously lost anatomical structures appear to repair, such as the luman of the mental foramen and the superior wall over the inferior alveolar canal. All mandibles were loaded postoperatively with an appliance having cutting bars and porcelain teeth or just porcelain teeth in both appliances.

Alveolar Bone Loss↗
PubMed2001

Management of an implant case that required retreatment: a case report.

The presented case represents how the lack of a preoperative panoramic radiograph or any radiograph contributed to incorrect case planning, poor implant selection, and the careless surgical placement of an implant into or dangerously close to the lower left mental foramen, resulting in a paresthesia of 9 months duration. Two implants were surgically removed and the bone defects were grafted with a mixture of irradiated cancellous bone plus Biogran. One implant was sectioned and intentionally "put to sleep." The case was successfully completed with a lower bar overdenture supported by 4 screw implants placed in alternate sites, opposing a custom fabricated maxillary denture with a lingualized occlusal scheme.

Alveolar Ridge Augmentation↗
PubMed2005

Assessment of three-dimensional X-ray images: reconstruction from conventional tomograms, compact computerized tomography images, and multislice helical computerized tomography images.

Three-dimensional X-ray images (3D images) were used for imaging diagnosis in the oral and maxillofacial region. These images could be fundamentally reconstructed from various tomograms, though clinical 3D images were mainly reconstructed from computerized tomography (CT) images. In this investigation, 3D images were reconstructed from conventional tomograms with a panoramic unit, compact CT images, and multislice helical CT images, and the usefulness of each system was subjectively assessed for dental implant treatment. Three hemilateral dried human mandibles were used and were examined by linear tomography with a panoramic unit, compact CT, and multislice helical CT, and 3D images were reconstructed by using the rendering software for each system. The 3D images were visually evaluated on a 5-point scale covering the alveolar ridge, buccal and lingual bone surface, mental foramen, and tooth sockets. As a result, 3D images reconstructed from conventional tomograms with the panoramic unit were assessed as fair to unsure, compact CT 3D images were assessed as unsure to good, and multislice helical CT 3D images were assessed as good to excellent. It was concluded that compact CT 3D images and multislice helical CT 3D images were useful in dental implant treatment.

Dental Implantation, Endosseous↗
PubMed2004

Evaluation of mandibular implant sites: correlation between panoramic and linear tomography.

The reliability of the linear tomography and panoramic radiography made with X-ray equipment was evaluated (Vera View Scope X-600; Morita). The sample was composed of 20 dry human hemimandibles, in which the area selected for analysis was 1.5 cm distal from the limit set before the mental foramen. Four measurements were made. The images obtained were drawn on acetate paper and the hemimandibles cut at the demarcated area. The measurements were made using a digital electronic pachymeter. The values found for the radiographic images were compared to those obtained in the mandibular specimens and submitted to statistical evaluation by the Wilcoxon test. It was concluded that both techniques were reliable for the accomplishment of vertical linear measurements in the selected area. However, a 2.0 mm safety margin is recommended.

Alveolar Process↗
PubMed2004

Morphometric analysis of implant-related anatomy in Caucasian skulls.

BACKGROUND: Sequelae related to implant placement/advanced bone grafting procedures are a result of injury to surrounding anatomic structures. Damage may not necessarily lead to implant failure; however, it is the most common cause of legal action against the practitioner. This study aimed to describe morphological aspects and variations of the anatomy directly related to implant treatment. METHODS: Morphometric analyses were performed in 22 Caucasian skulls. Measurements of the mental foramen (MF) included height (MF-H), width (MF-W), and location in relation to other known anatomical landmarks. Presence or absence of anterior loops (AL) of the inferior alveolar nerve (IAN) was determined, and the mesial extent of the loop was measured. Additional measurements included height (G-H), width (G-W), thickness (G-T), and volume (G-V) of monocortical onlay grafts harvested from the mandibular symphysis area, and thickness of the lateral wall (T-LW) of the maxillary sinus. The independent samples t test, and a two-tailed t test with equal variance were utilized to determine statistical significance to a level of P < 0.05. Multiple regression analyses were performed to determine if each one of these measurements was affected by age and gender. RESULTS: The most common location of the MF in relation to teeth was found to be below the apices of mandibular premolars. The mean MF-H was 3.47 +/- 0.71 mm and the mean MF-W was 3.59 +/- 0.8 mm. The mean distance from the MF to other anatomical landmarks were: MF-CEJ = 15.52 +/- 2.37 mm, MF to the most apical portion of the lower cortex of the mandible = 12.0 +/- 1.67 mm, MF to the midline = 27.61+/- 2.29 mm, and MF-MF = 55.23 +/- 5.34 mm. A high prevalence of AL was found (88%); symmetric occurrence was a common finding (76.2%), with a mean length of 4.13 +/- 2.04 mm. The mean size of symphyseal grafts was: G-H = 9.45 +/- 1.08 mm, G-W = 14.5 +/- 3.0 mm, and G-T = 6.15 +/- 1.04 mm, with an average G-V of 857.55 +/- 283.97 mm3 (range: 352 to 1,200 mm3). The mean T-LW of the maxillary sinus was 0.91 +/- 0.43 mm. CONCLUSION: Implant-related anatomy must be carefully evaluated before treatment due to considerable variations among individuals, in order to prevent injury to surrounding anatomical structures and possible damage.

Aged↗
PubMed2005

Transmandibular approach to polycentric recurrent pleomorphic adenoma of the parapharyngeal space.

Surgery for tumors of the parapharyngeal space PPS) requires adequate exposure to identify and protect vital structures. Thus transcervical and transcervical-transparotid approaches to the PPS may be enhanced by mandibulotomy for better visualisation. We have chosen this approach with single mandibulotomy just in front of foramen mentale and without lip incision. We present a 39 years old male who was undergone surgery for policentric recurrency of a pleomorphic adenoma of the parapharyngeal space.

Adenoma, Pleomorphic↗
PubMed2005

Rare courses of the mandibular canal in the molar regions of the human mandible: a cadaveric study.

The inferior alveolar artery, vein and nerve send some branches to the molar teeth via the mandibular canal to the mental foramen. The present study attempted to define the presence and course of the mandibular canal in the mandible with the alveolar process by macroscopic cadaveric dissection and computerized tomography (CT) in order to provide information that might prevent injuries to vessels and nerves at risk during root canal treatment. We identified the position of the mandibular canal within a 30% ratio of the distance from inferior border of mandible to the apices of the root for 39 out of 131 sides (mesial root of first molar, 20%; distal root of first molar, 22.6%; mesial root of second molar, 27.8% and distal root of second molar, 47%) on panoramic X-ray observation. In one cadaver (male, 64 years old), the root apex of the second molar was in close proximity to the upper bony mandibular canal. Macroscopic dissection and computerized tomography showed that the main trunks of the inferior alveolar artery, vein, and nerve were in tight contact with the apex of the second molar. These observations of the anatomic course of the mandibular canal will be important to consider during root canal treatment of mandibular teeth.

Adult↗
PubMed1996

The measurements of some anthropometric landmarks of the mandible; a preliminary anatomical study.

In this study, the morphometric measurements were done on human cadaver mandibles including ramus height and width, angle between ramus and corpus, the relation between foramen mentale and teeth. The aim of this study was to establish some standards with the achieved results in order to expand these studies in some reconstructive surgical areas. As a result, the standard measurements were established under the heads of short and long ramus, acute and obtuse angle mandibles.

Anthropometry↗
PubMed1998

[Bone mineral density (BMD) distribution in edentulous mandible--a measuring system for bone mineral content with computed radiography (CR)].

The purpose of this study was to develop a measuring system for bone mineral density(BMD) using computed radiography and to measure BMD distribution in the edentulous mandible. Nine 2-3 mm thick sequential cross-sectional bone slices were obtained from five cadaveric mandibles. Each slice in cross-sectional view on X-ray image was divided into 64 elements and BMD distribution was investigated. The results were as followed: 1. BMD measuring system: The accuracy was 1.4%(relative error) and the reproducibility was 1.1%(CV). 2. BMD distribution in edentulous mandible: 1) BMD varied from slice to slice, decreasing from anterior to posterior in both cortical and cancellous bone on the inferior and lingual side. The BMD of buccal cancellous bone was relatively higher than that of the lingual side and remained fairly constant throughout. The BMD of buccal cortical bone showed a slight posterior increase. 2) Greater individual variation of BMD was observed near mental foramen and in incisor lingual and inferior cancellous bone. Our system demonstrated excellent precision and reproducibility BMD distribution varied near regions of muscle attachment and the mandibular canal. Further, it was suggested that strong implant stability in the molar region may be obtained by installation of the fixtures in the buccal cancellous area.

Bone Density↗
PubMedDate not supplied

Lateralization of the inferior alveolar nerve with simultaneous implant placement: surgical techniques.

In the event of moderate to severe mandibular bone resorption posterior to the mental foramen, repositioning of the inferior alveolar nerve provides a greater amount of available bone for implant placement and reduces the risk of nerve injury. While neural paresthesia may initially occur, this altered sensation generally resolves spontaneously. Alveolar nerve repositioning may be possible in cases in which other procedures cannot be performed due to the extent of atrophy of the posterior mandibular alveolar crest. This article presents the surgical technique to achieve this objective.

Dental Implantation, Endosseous↗
PubMed1999

[The architectural balance of the face: a 3D cephalometric concept].

The use of the c2000 software led us to develop a new 3D cephalometric construction, based on the selection on the axial CT Scans of 8 anatomical landmarks and of teeth, all of which were situated along the trigeminal neuro matriciel facial growth axes. The analysis of this construction is based on the use of an original mathematical tool in biology: the axes of inertia. Using the selection of both mental foramen, both infra and supra orbital foramen and the head of both malleus, the C 2000 software creates a geometrical construction called: "the maxillo-facial frame", as well as, a 3D cephalometric analysis: angles, distances, areas, volumes center of gravity and axes of inertia. Using the selection of teeth, the C 2000 software calculates the axes of inertia of each tooth or of groups of teeth. The use of the axes of inertia allow us to create of a hierarchy of anatomical levels the teeth, the half arches, the arches, both arches and the maxillo-facial frame. In addition, for each of these anatomical levels, the axes of inertia create a 3D landmark which allows the calculation of the orientation of each of these elements in relation to the others. The study of 28 orthomorphic people using this analysis revealed the existence of a maxillo-facial balance that is unique for each individual.

Adolescent↗
PubMed2000

[Mandibular atrophy and a screw-retained implant-supported prosthesis].

Prosthetic care for mandibular atrophy has raised many difficult problems, particularly in the most severe cases. The solution to most of these problems lies in the use of osteointegrated implants. Good results were obtained by using a small number of implants associated with adjustable overdenture prostheses or, alternatively, by using a larger number of implants (5 or 6) associated with a screw fixed prosthesis with posterior cantilever. Cantilever prostheses can provide support for the mental foramen zones and the posterior zones of the mandibular body where bone resorption is important after application of adjustable plates to the fibromucosa.

Aged↗
PubMedDate not supplied

Lateralization of the inferior alveolar nerve with simultaneous implant placement: a modified technique.

PURPOSE: Several nerve repositioning techniques have ben presented in the literature, each with limitations. This article presents a new technique involving the use of 2 osteotomies, with minimizes particularly the potential duration of sensory disruption and the risk of nerve paresthesia and inadvertent nerve transection or compression. MATERIALS AND METHODS: Ten patients ranging in age from 47 to 67 years were selected for nerve lateralization utilizing the modified technique. A total of 23 cylindrical implants were placed. An average follow-up period was 29.8 months. RESULTS: Of the 10 patients, 4 experienced total return of sensation within 3 to 4 weeks. One patient experienced complete recovery at 6 weeks. DISCUSSION: Creating 2 osteotomies as described minimizes the chances for postoperative neuropraxia and nerve paresthesia or anesthesia. CONCLUSION: When there is moderate-to-severe bone resorption of the mandible posterior to the mental foramen, repositioning the inferior alveolar nerve using both an anterior and posterior osteotomy allows for more bone to accommodate ideal placement and greater length of implant.

Aged↗
PubMed2003

[An experimental study on circadian rhythm of the proliferative index of mandibular osteoblast in goats].

OBJECTIVE: The aim of this study was to investigate the circadian rhythm of the proliferative index of mandibular osteoblasts of goats in a normal situation. METHODS: Twenty four healthy goats were selected and randomly divided into six groups. They were killed, and a piece of bone tissue with 2 cm x 2 cm x 0.5 cm was obtained from right mandibular mental foramen region at 0:00, 4:00, 8:00, 12:00, 16:00 and 20:00 time points, after they had been fed for one week. The primary cell culture method was used to cultivate osteoblasts from the bone. The method of anti-5-bromodeoxyuridine monoclonal antibody and the flow cytometric analysis were used to detect the proliferative index of the mandibular osteoblasts at different time. The data were analyzed using the method of single cosine rhythmometry. RESULTS: The proliferative indexes of the mandibular osteoblasts of goats were higher at the nighttime and lower in the daytime. The undulation of the proliferative indexes displayed a significant circadian rhythm (P < 0.01). The peak value was obtained at about 19:44, and the lowest value at about 7:44. CONCLUSION: The proliferative indexes of the mandibular osteoblasts of goats are not stable within 24 hours in a normal situation, but with significant circadian rhythm. There are different proliferative indexes at different time points.

Animals↗