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Biomedical subjects

J F Lownie

Publications and source records attributed to J F Lownie.

At least 19 recordsLinked to original sources
PubMed2003

The zygomaticus implant protocol in the treatment of the severely resorbed maxilla.

The zygomaticus dental implant, designed by NobelBiocare, was developed primarily for the treatment of the severely resorbed maxilla. Brånemark has reported an overall success rate of 97.6% with the placement of over 200 zygomatic implants during the period 1989 to 2001. There are well-defined characteristics within the patient's resorbed skeletal frame which guide the surgical placement of the zygomatic implant, thus determining whether the surgeon should use an implant with a 45 degrees or 55 degrees angulated head. This allows implant-supported restoration of the resorbed maxilla with a fixed cross arch prosthesis in the maxilla without a bone graft to the posterior maxilla. The use of a modified head angulation of 55 degrees, with implant placement as close to the crest of the edentulous ridge as possible, allows restorative clinicians to achieve an ideal restorative position in the posterior maxilla. The use of a zygomatic implant with a 55 degrees head reduces the buccal cantilever by 20%.

Bone Resorption↗
PubMed2002

Haematoma of the floor of the mouth following implant placement.

Placement of implants in the anterior mandibular region is generally regarded as a routine, safe procedure. This case report describes an extensive haematoma in the floor of the mouth, following such a procedure, which rapidly became life-threatening, requiring an emergency tracheostomy to establish a surgical airway. The anatomic, radiographic and surgical aspects to the problem are discussed. Finally, when undertaking such procedures it is advisable to perform them reasonably close to a hospital where such a complication can be effectively and promptly handled by suitably trained persons.

Airway Obstruction↗
PubMed2001

Inter-abutment and peri-abutment mucosal enlargement with mandibular implant overdentures.

A variety of terms have been used to describe changes in the oral mucosa around abutments underneath fixed and removable implant prostheses such as mucosal inflammation, peri-implant mucosal hyperplasia, gingival hyperplasia, hyperplastic tissue, mucosal proliferation, proliferative gingivitis and peri-implant mucositis. Although such terms have become part of the evidence-based literature, there is no histological evidence to support the descriptive terminology used by authors. The use of the alternative term mucosal enlargement for clinical observations underneath mandibular implant overdentures is proposed. Prospective and retrospective reports have failed to use similar criteria to measure periodontal parameters in relation to these mucosal changes, both in keratinized or non-keratinized tissues. Therapeutic remedies for mucosal enlargement are dictated by authors' opinions on the possible aetiology. This literature review, coupled with clinical observations during a 5-year prospective study, prompts this proposal of the term mucosal enlargement underneath splinted and unsplinted mandibular implant overdentures.

Dental Abutments↗
PubMed1999

Long-term histologic changes in the dental pulp after posterior segmental osteotomies.

OBJECTIVE: The purpose of this study was to examine pulp tissue for 18 months after segmental osteotomy in nonhuman primates. STUDY DESIGN: In this long-term experimental study, subapical, posterior, maxillary, and mandibular osteotomies were done in 26 baboons (Papio ursinus). Baboons were killed humanely immediately after operation and at 3, 6, 12, and 18 months, when tissues were perfusion-fixed. Longitudinal step-serial sections of dental pulps were examined. RESULTS: There was a loss of the odontoblast layer as early as 3 months after surgery. Inflammatory cell infiltrate was most marked in the early postoperative stages, and the formation of osteodentin and secondary dentin was evident after 6 months. Foci of necrosis were present in the 3-month and 6-month groups but were replaced by pulp fibrosis in the 12-month and 18-month groups. All these changes were more frequent in experimental than control teeth. CONCLUSIONS: The histologic changes seen should not affect the prognosis of teeth in subapical osteotomy segments if clinicians are careful not to damage root apices and do regular, careful, clinical, and radiographic follow-up examinations. Because many pulps healed spontaneously in the study teeth, endodontic treatment should be delayed until it is clearly needed.

Animals↗
PubMed1999

Standardization of radiographs for mandibular implant-supported overdentures: review and innovation.

Radiographic monitoring of marginal peri-fixture bone is mandatory during prospective evaluation of different dental implant systems. Unyielding, uni-directional focus towards identifying the credibility of implant-supported overdenture therapy for the management of the edentulous predicament, has often neglected correct standardization of follow-up radiographs. Techniques for truly accurate location of film-holding devices have often not been applied to both unicentre and multicentre reports on mandibular implant-supported overdentures using Brånemark implants. An innovative improvement on existing methods using conventional and custom-made components, shows a procedure to accurately and simply standardize follow-up radiographs, for both free-standing and bar designs for mandibular implant-supported overdentures.

Alveolar Process↗
PubMed1998

Vascularity of the dental pulp after segmental osteotomy in the chacma baboon (Papio ursinus).

OBJECTIVE: To assess the vascularity of the dental pulp after segmental operations with and without interpositional autogenous bone grafting. DESIGN: Experimental study. SETTING: University Department, South Africa. ANIMALS: 26 chacma baboons. INTERVENTIONS: Maxillary and mandibular posterior segmental osteotomies were perfused with barium sulphate 3, 6, 12 and 18 months postoperatively. The animals were killed at 3, 6, 12 and 18 months after surgery and perfused with barium sulphate. Barium-filled vessels were counted in histological sections from 189 control and experimental teeth. MAIN OUTCOME MEASURE: Number of blood vessels. RESULTS: Blood vessel counts in mandibular teeth in osteotomy segments ranged from 0 to 1.15 compared with 2.27 to 4.58 in control teeth, while in maxillary teeth counts ranged from 0.54 to 2.22 for experimental teeth and 3.3 to 4.65 for controls. For both jaws, the numbers of vessels in experimental teeth gradually increased between 3 and 18 months but remained less than those in control teeth. Numbers of blood vessels were similar in graft and no-graft groups but both were less than half the counts in control teeth. CONCLUSION: Blood flow is present in the teeth at all times after posterior segmental osteotomy but there is a risk of ischaemia.

Animals↗
PubMed1997

Demographic profile of patients who present for emergency treatment at Wits' Dental School.

The faculties of dentistry and medicine at the University of the Witwatersrand will soon amalgamate into a faculty of health sciences. To help plan service provision a demographic profile was determined for 500 patients who attended for emergency treatment in the dental faculty over all four seasons. Mean daily rates were Autumn 7.7, Winter 8.8, Spring 7.8 and Summer 3.3. Most patients (45 per cent) arrived by car, 23 per cent came by bus while 19% walked to the dental school. Over three-quarters (77 per cent) came directly from home and the same proportion had endured symptoms for more than 48 hours. Many (60 per cent) had been treated previously at the dental school of whom 31 per cent had received this within the previous month. No less than 85 per cent had no regular dentist. A third of patients had no symptoms, 26 per cent had chronic pain and in 10 per cent the pain was acute in onset. The most frequent treatments were temporary restorations (39 per cent) and pulp extirpation (34 per cent). An irregular daily work load, together with endurance of symptoms by patients, indicates that an emergency service Monday to Friday during normal working hours is adequate.

Adolescent↗
PubMed1997

Multi-planar and cross-sectional oblique scanning (CT) in implant surgery.

A comprehensive clinical examination followed by a radiographic assessment of the edentulous areas is a prerequisite to placing dental implants. Although radiographic assessment of the mandible is accurate using plain film radiography this is not so for the maxilla for which computed tomography is often necessary. In this study patients requiring the placement of maxillary implants were referred for multi-planar cross-sectional oblique and panoramic computed tomography (CT scan) in addition to standard radiographic views. After interpretation of the CT scans patients could be categorized into two groups. One group comprised those patients who could be treated with a standard protocol for implant placement; the second group required augmentation procedures to supplement bone volume. After implant placement, a minimum healing period of 24 weeks was adhered to prior to placing healing abutments. By 27 months 95.5 per cent of Brånemark System fixtures were osseo-integrated.

Adolescent↗
PubMed1996

Maxillofacial injuries in a group of South Africans under 18 years of age.

OBJECTIVE: To find out the incidence of maxillofacial injuries in South African children aged 18 years or less. DESIGN: Retrospective study of casenotes. SETTING: Six teaching hospitals affiliated to the University of Witwatersrand, Johannesburg, serving a population of about 5 million people. SUBJECTS: All 326 children treated for facial injuries in the maxillofacial and oral departments of the six hospitals between 1 January 1989 and 30 June 1992. MAIN OUTCOME MEASURES: Classification of the types of injury, associated injuries, cause of the injury, and methods of diagnosis. RESULTS: Of the total of 4192 patients of all ages treated for facial injuries, 326 (8%) were within the age range of the study. The female:male ratio was 1:2.3. Most of the injuries (227, 70%) occurred in the 13-18 age group, and assaults, fights and gunshot wounds accounted for 155 injuries (48%). Of the 326 children, 173 (53%) had single injuries and 153 (47%) had multiple injuries. Mandibular fractures were the most common (64%) followed by maxillomandibular fractures (25%). Violence was the most common cause of injury, as in the USA and Zimbabwe, but unlike the rest of the world in which it is motor vehicle accidents. Soft tissue injuries were the most common associated injuries, and conventional plain radiography was the usual investigation. CONCLUSION: The incidence of 8% compares favourably with those in other countries, but far too many injuries are the result of violence.

Accidents, Traffic↗
PubMed1996

Nerve degeneration within the dental pulp after segmental osteotomies in the baboon (Papio ursinus).

Following dentofacial surgical procedures, teeth in segments often do not sense thermal or electric stimuli. This study was undertaken to assess changes in the neural component of the dental pulp after posterior maxillary and mandibular segmental osteotomies, with or without interpositional autogenous bone grafting, in 26 Chacma baboons. Innervation was assessed histologically immediately after operation, and at 3, 6, 12 and 18 months. Statistically significant differences were present between the experimental and control groups. Even after 18 months no nerves were present in any of the mandibular teeth. In maxillary teeth, 50 per cent had demonstrable nerves in the graft group and 40 per cent in the no graft group. As nerve degeneration was present in the experimental teeth, patients should be warned of possible change in tooth sensibility, following these operations. Careful post-operative follow up for long periods in humans following dentofacial surgical procedures is thus essential.

Animals↗
PubMed1996

A radiographic analysis of the mandibular canal of the edentulous mandible in different racial and gender groups.

Studies on the mandibular canal in the edentulous mandible have rarely been correlated with mandibular canal position, mandibular body width, mandibular canal width, thickness of bony plates, gender and race. The aim of this investigation was to examine the above parameters by studying the bucco-lingual relationship of the mandibular canal in dry edentulous mandibles of Black and White, males and females (n = 13 in each group), of similar age (mean 58, 17 yrs). The mandibles were radiographed cross-sectionally. The position of the mandibular canal in relation to the buccal and lingual cortical plates, and the widths of the mandibular canal and mandibular body, measured at selected distances, were recorded and the values statistically analysed. Race and gender do not seem to influence the position of the mandibular canal in the bucco-lingual plane. The location of the canal is predominantly closer to the lingual cortex in the bucco-lingual plane. It was found that the widths of the left and right halves of the mandibular body are not statistically significantly different but widths of the left and right mandibular canal are significantly different.

Adult↗
PubMed1993

Oral manifestations of leprosy.

A total of 37 out of 187 patients with leprosy had oral lesions. All were biopsied. Oral lesions were found most frequently in patients with lepromatous leprosy. Prevalence of oral lesions was higher in males than in females (73%:27%). Oral lesions were recorded on the WHO topographical map, and in most cases (92%) several topographical locations were affected, including hard palate in all cases. Topographical locations affected increase with age; males are more extensively affected than females (p = 0.001); and patients with oral lesions who reported affected family members (11 out of 37) had more extensive oral lesions than those who did not. In 27 cases with oral lesions histopathological diagnosis was possible.

Adolescent↗
PubMed1992

Comparison of the safety and efficacy of a combination analgesic Myprodol and Ponstan in the treatment of dental pain.

A comparison of the efficacy of Myprodol, a combination analgesic (Ibuprofen, Paracetamol and Codeine phosphate) and Ponstan (Mefenamic acid) was undertaken in a randomised double blind trial of 52 patients who underwent surgical removal of impacted or unerupted teeth. Pain scores were measured for patients pre- and post operatively by means of a visual analogue scale and data was analysed using the BMPD package on the ISM main frame computer at the Medical Research Council. The results indicated that although Myprodol and Ponstan were equally adequate and well tolerated in the control of post operative dental pain, Myprodol exceeded Ponstan in duration of analgesia and in the degree of pain intensity control experienced by the patient.

Acetaminophen↗
PubMed1990

Relative efficiencies of various wiring configurations commonly used in open reductions of fractures of the angle of the mandible.

Many fractures of the angle of the mandible require direct intraosseous fixation in addition to intermaxillary fixation. In the past, various configurations of intraosseous wiring were used both at the lower and upper borders of the mandible. This study investigated which of four configurations offers the greatest mechanical resistance to a typical displacing force. Twelve baboon mandibles were cleared of all soft tissues and sectioned in the midline, and the most distal erupted molar tooth was extracted. Jigs were constructed to ensure that each mandible was sectioned in a standard fashion and that holes for wiring were drilled at a standard distance from the cut line. Mandibular halves, wired under standard conditions, were placed in an Instron tensile testing machine and subjected to a constant force that simulated the action of the major elevator muscles. Graphic recordings of force versus displacement were made. The results were subjected to an analysis of covariance, and to Scheffe's test for multiple comparisons. Results indicate that under experimental conditions, without jagged fracture surfaces, upper border mandibular wiring is less efficient than lower border wiring. At the lower border, a figure-of-eight wire is more effective than a combination figure-of-eight and straight wire, and at the upper border, the figure-of-eight wire is more effective than the straight wire.

Animals↗
PubMed1990

Provision of "comprehensive dental care" in various dental schools.

The purpose of this survey was to solicit information about comprehensive dental care (CDC) programmes in various dental schools. Seventy-four schools responded to a questionnaire which sought information about a range of topics pertaining to CDC. The 19 questions used were categorized under the following headings: implementation and success; physical nature of clinics; staffing; and, student involvement. The diverse nature of the responses is thought to be an expression of differing philosophies and of the presence of numerous constraints to the introduction of CDC. The various approaches to CDC make it very difficult to gauge the relative merits of the many systems reported. It appears from this study that departments will continue to play an important role in preparing students to participate in CDC programmes and that it would be safer to introduce students to CDC during the final year of study.

Comprehensive Dental Care↗