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Biomedical subjects

R B Ross

Publications and source records attributed to R B Ross.

At least 19 recordsLinked to original sources
PubMed2004

Hildebrand and Hansen solubility parameters from molecular dynamics with applications to electronic nose polymer sensors.

We introduce the Cohesive Energy Density (CED) method, a multiple sampling Molecular Dynamics computer simulation procedure that may offer higher consistency in the estimation of Hildebrand and Hansen solubility parameters. The use of a multiple sampling technique, combined with a simple but consistent molecular force field and quantum mechanically determined atomic charges, allows for the precise determination of solubility parameters in a systematic way (sigma = 0.4 hildebrands). The CED method yields first-principles Hildebrand parameter predictions in good agreement with experiment [root-mean-square (rms) = 1.1 hildebrands]. We apply the CED method to model the Caltech electronic nose, an array of 20 polymer sensors. Sensors are built with conducting leads connected through thin-film polymers loaded with carbon black. Odorant detection relies on a change in electric resistivity of the polymer film as function of the amount of swelling caused by the odorant compound. The amount of swelling depends upon the chemical composition of the polymer and the odorant molecule. The pattern is unique, and unambiguously identifies the compound. Experimentally determined changes in relative resistivity of seven polymer sensors upon exposure to 24 solvent vapors were modeled with the CED estimated Hansen solubility components. Predictions of polymer sensor responses result in Pearson R2 coefficients between 0.82 and 0.99.

Algorithms↗
PubMed2001

The mandibular catch-up growth controversy in Pierre Robin sequence.

The purpose of this retrospective longitudinal cephalometric study was to investigate differences in craniofacial and especially mandibular morphology between patients with Pierre Robin sequence and isolated cleft palates. The experimental group comprised 96 patients (54 males and 42 females) with a history of Pierre Robin sequence. This group was compared cephalometrically with a control group of 50 patients (25 males and 25 females) with a history of isolated clefting of the palate. All 96 patients in the PR group had a lateral cephalogram at a mean age of 5.5 years. Thirty-eight of those patients had additional cephalograms at the mean ages of 10.3 years and 16.8 years. All patients in the cleft palate group had 3 corresponding cephalograms at the following mean ages: 5.7 years, 10.6 years, and 17.0 years. Twenty-nine cephalometric measurements were performed on each cephalogram with the use of computerized cephalometric software. Significant differences were identified between the 2 groups, particularly in the size and sagittal position of the mandible, which was consistently shorter in the Pierre Robin group at all 3 ages. Less severe differences were noted in the inclination of the palatal plane, the facial height proportions, and the midface depth. We conclude that patients with Pierre Robin sequence have a significantly smaller mandible as compared with patients with isolated cleft palate, and the difference does not change after the age of 5 years.

Adolescent↗
PubMed1999

Costochondral grafts replacing the mandibular condyle.

OBJECTIVE: The purpose of this study was to determine the success rate of costochondral bone grafts used to replace absent or nonfunctioning temporomandibular joints and the subsequent growth of these grafts when placed in young children. DESIGN: This is a retrospective study of all cases with adequate follow-up records that were treated at the Craniofacial Centre at Toronto's The Hospital for Sick Children from 1974-1986. A total of 55 patients were evaluated, of whom 13 were growing children. RESULTS: The findings suggest that there was increased success when surgery was performed at an early age. Poorer results were achieved when previous surgery had been performed or when pathology was present. Growth of the graft did not always equal the growth of the "normal" side, but in most cases a satisfactory symmetry was achieved. Several cases exhibited excessive overgrowth. CONCLUSIONS: Surgery at 4 to 5 years of age will alleviate the impact of a severe facial deformity on the child during the early school years, when self-esteem is fragile and patterns of social interactions are developing. Development of the dentition is better if the jaw relationship is close to normal at an early age. It would appear that early temporomandibular joint (TMJ) construction by costochondral grafting is, at present, the method of choice for severe hemifacial microsomia.

Adolescent↗
PubMed1998

Unilateral cleft lip with or without cleft palate and handedness: is there an association?

OBJECTIVE: The purpose of this study was to investigate the possibility of a relationship between the side of occurrence of unilateral clefting of the lip and/or palate and handedness, also taking into account the type of the initial cleft condition, a factor that has not been adequately assessed in previous studies. DESIGN: This was a retrospective study. SETTING: Division of Orthodontics, The Hospital for Sick Children, Toronto, Canada, and Cleft Lip and Palate Program, Children's Hospital, Winnipeg, Canada. PARTICIPANTS: Subjects were 289 patients (176 males and 113 females) 9 years of age or older presenting with a history of unilateral clefts of the lip with or without the palate. Of these patients, 217 were recruited from the patient pool of the Orthodontic Clinic at the Hospital for Sick Children in Toronto. The remaining 72 were selected from the registry of the Cleft Lip and Palate Program of the Children's Hospital in Winnipeg. Any syndromic cases were excluded from the sample. MAIN OUTCOME MEASURES: Assessment of handedness was performed by asking the patients to fill out a multi-item questionnaire in which patients were asked to identify which hand they would use for different tasks. The side and type of the initial cleft condition were identified by reviewing each patient's hospital chart and by cross-referencing with clinical examination. Statistical evaluation of the results was performed by using the chi-square test. RESULTS: There was a significantly larger number of left-sided clefts (198) in the sample than right-sided clefts (91), (p < .001). The proportion of left-sided clefts among left-handers (84.6%) was higher than that among right-handers (66.8%). However, the relationship between side of cleft and handedness was not statistically significant (p = .185). Clefts of the primary palate only seemed to occur on the left side 3.5 times more often than on the right, whereas the corresponding ratio of left:right manifestation for clefts of the primary and secondary palate was 1.8:1. The difference was statistically significant (p < .05). CONCLUSION: The findings of this study confirm the affinity of unilateral clefts for the left side but suggest that there are differences between clefts of the primary palate only and clefts of the primary and secondary palate. Also, non-right-handed patients show a greater predilection for having a cleft on the left side than do right-handed patients.

Chi-Square Distribution↗
PubMed1997

A retrospective comparison of frontal facial dimensions in alveolar-bone-grafted and nongrafted unilateral cleft lip and palate patients.

This retrospective study was undertaken to describe and compare frontal craniofacial dimensions in alveolar-bone-grafted and nongrafted complete unilateral cleft lip and palate (CUCLP) patients and in noncleft subjects with normal occlusions and good facial balance. Clinical data were obtained from the files of the Hospital for Sick Children, Toronto. Patients were eligible for inclusion if they had posteroanterior cephalograms (PA) taken at adulthood and no congenital anomalies other than CUCLP. A total of 86 adult Caucasian CULCP patients were studied, including 58 who had not received grafts, 28 who had received secondary alveolar bone grafts, and, for comparison, 60 noncleft Caucasian adults. The PA cephalometric radiographs were traced, digitized, and measured. Analysis of variance (ANOVA) was used to test for among-groups differences in the means of the ratios, proportions, and angular measures. Tukey-Kramer HSD procedure was used to conduct post-hoc pairwise comparisons following significant (p < or = 0.05) F-ratios from ANOVA. Sexual dimorphism was a common finding, with males demonstrating greater facial width. Despite primary surgical repairs, the anterior nasal spine in the nongrafted CUCLP patients was deviated to the noncleft side, and the alar base was depressed on the cleft side. The maxillary incisors close to the cleft site were irregularly inclined, and this irregularity was more severe in the nongrafted CUCLP patients. The long-term effects of secondary alveolar bone grafting on transverse craniofacial growth appears to be minimal and limited to the immediate area of the cleft.

Adolescent↗
PubMed1997

Effect of alveolar bone grafting in the mixed dentition on maxillary growth in complete unilateral cleft lip and palate patients.

OBJECTIVE: This study was conducted to evaluate the effects on facial growth of alveolar bone grafting in the mixed dentition for patients with UCLP. DESIGN: Retrospective cephalometric study. SETTING: Craniofacial Treatment and Research Centre, The Hospital for Sick Children, Toronto, Ontario, Canada. PATIENTS: The 58 patients participating in the study had a history of complete unilateral cleft lip and palate, all of which were repaired by the same plastic surgeon. INTERVENTIONS: Twenty-one patients received an iliac-crest alveolar bone graft at a mean age of 10.3 years, while 37 did not receive an alveolar bone graft. Lateral cephalometric radiographs were obtained on all patients at two different times:at a mean age of 9.4 years (prior to bone grafting in the grafted group) and at a mean age of 15.2 years. MAIN OUTCOME MEASURES: All radiographs were traced and digitized by the same person, using cephalometric computer software. Superimposition and cephalometric analysis was undertaken to investigate the differences between the two groups in the 5.6-year experimental period. A two-way analysis of covariance was used for evaluation of the statistical significance of the results. RESULTS: No statistically significant differences were found in 14 of the 15 cephalometric measurements performed. Harvold's maxillary unit length was statistically significantly shorter in the grafted group, although a lack of correlation with angular measurements and inherent problems with this specific measurement raise doubts in this finding. CONCLUSION: Mixed dentition bone grafting does not affect subsequent vertical and A-P development of the maxilla in complete unilateral cleft lip and palate patients during the first several postoperative years.

Adolescent↗
PubMed1995

Growth of the facial skeleton following the Malek repair for unilateral cleft lip and palate.

Variations in the surgical procedures used to repair a complete unilateral cleft lip and palate have differing effects on growth of the facial skeleton. In this study, cephalometric radiographs of the cases of Professor Rene Malek were analyzed. The sample consisted of 35 male patients with complete unilateral cleft lip and palate at a mean age of 10.1 years. Previous data from the cases of Dr. W.K. Lindsay in Ross (1987). Cephalometric data were compared with our sample. Results showed that the Malek protocol for surgical repair, as performed by Malek, produces excellent midface growth at 10 years of age.

Cephalometry↗
PubMed1994

Effect of presurgical infant orthopedics on facial esthetics in complete bilateral cleft lip and palate.

A sample of 40 teenage individuals with repaired complete bilateral cleft lip and palate, 20 of whom had received presurgical infant orthopedics, was obtained to test the effects of presurgical infant orthopedics on facial esthetics. All subjects had surgery by the same surgeon. The age and sex distribution was approximately equal between the two groups. A panel of five judges evaluated the lip and nose esthetics from full face and profile slides and a mean panel score for each subject was derived for six individual features and three total scores. No difference in the esthetic scores between the two groups could be detected. No differences were found in the number of revisionary surgical procedures required to the lip or nose. The findings indicate that conservative presurgical orthopedics for infants with complete bilateral cleft lip and palate has no lasting effect on the esthetics of the lip and nose, and does not alter the need for subsequent revisionary surgery.

Adolescent↗
PubMed1993

Craniofacial growth in bilateral cleft lip and palate: ages six years to adulthood.

The purpose of the study was to localize the characteristic craniofacial abnormalities in young children with complete bilateral cleft lip and palate, to average their growth changes, and to compare all these to observations from a normative sample. A longitudinal sample of 30 males with complete bilateral cleft lip and palate was obtained from the files of the Craniofacial Center at The Hospital for Sick Children, Toronto. An age-matched noncleft control sample was selected from the Burlington Orthodontic Research Center. All individuals had lateral cephalometric radiographs at approximately 6 years, 12 years, and as adults. These were analyzed by cephalometrics and by tensor biometrics. The results of the two methods of analysis were in agreement and tended to complement each other. In the cleft sample, there was little clefting effect on the midline structures of the cranial base; the premaxilla was initially protruded but became normal in the adult; the nasal bone was longer and more protruded; the posterior maxillary segments were hypoplastic and the bony pharynx narrower; there was over-eruption of the posterior teeth; and the mandibular gonial area was smaller.

Adolescent↗
PubMed1993

Soft tissue response to orthognathic surgery in persons with unilateral cleft lip and palate.

Individuals with cleft lip and palate often require orthognathic surgery to establish facial harmony and optimal occlusal function. Surgery to the skeletal components of the face can accomplish predictable alterations in jaw relations. The soft tissue response to those skeletal movements, however, is difficult to predict, as it is also for the noncleft individual. In addition there is the variability of the repaired cleft lip. The study included 30 persons with complete unilateral cleft lip and palate, operated for midface deficiency using a Le Fort I maxillary advancement at a mean age of 18.0 years. Some relapse occurred in the immediate postoperative period, but after 1 year the mean advancement of the maxilla was 4.9 mm (best fit of anterior maxilla) and 5.6 mm (incisal edge). Both skeletal and soft tissue changes were negligible after that time. The ratio of upper lip advancement to underlying incisor advancement was 0.65 to 1. Although the lip response was highly correlated to the underlying bony movement, the variation was sufficient to preclude accurate prediction. The upper lip thinned with maxillary advancement, but this was not related to the original lip thickness. Coincident mandibular surgery had no appreciable effect on upper lip movement.

Adolescent↗
PubMed1992

Soft tissue response to mandibular advancement and genioplasty.

Changes in facial esthetics after orthognathic surgery should be predictable if the results are to be satisfactory. The skeletal elements are moved in a planned and controlled manner, but the soft tissue drape is not as precisely managed. This study was on 31 patients who had undergone a mandibular advancement by means of a sagittal split osteotomy, 17 of whom had also received an advancement genioplasty and 6 received a maxillary impaction. The results showed a consistent 1:1 ratio of soft to hard tissue advancement at pogonion and B point, and that predictions could be accurate in both anteroposterior and vertical directions. When a genioplasty was added to the advancement, however, the results were much less consistent. The mean ratio was 0.9:1 of soft tissue to skeletal movement at pogonion, but the average difference between hard and soft tissue movement was +/- 2.6 mm. Thus the prediction of anteroposterior soft tissue changes was quite inaccurate. Changes in the vertical dimension were also more marked in the genioplasty group. The lower lip also showed a variable response, particularly in the genioplasty group, where the mean ratio was 0.5 mm lip advancement per 1.0 mm skeletal change, but again a range of 4.0 mm in either direction. There were no meaningful changes 1 year after surgery.

Adolescent↗
PubMed1989

Orbital measurements in 63 hyperteloric patients. Differences between the anthropometric and cephalometric findings.

Anthropometric and cephalometric orbital measurements were compared in 63 North American Caucasian patients (24 males, 39 females) aged 3 to 29 years who had 13 craniofacial syndromes involving hypertelorism. The hypertelorism, which was diagnosed anthropometrically, was mild in 11 patients, moderate in 25 and severe in 27. The surface intercanthal width was larger than the bony interorbital distance in all patients (mean 12.2 mm). The differences were smaller in mild cases and larger in severe cases. The soft-tissue binocular width was shorter than the bony lateral orbital distance in 53 patients, by a mean of 4.4 mm; in the other 10 patients the two measurements were identical. The hypertelorism was confirmed by cephalometry in 8 of the 11 cases identified as mild by anthropometry (72.7%), 24 of the 25 moderate cases (96.0%) and 25 of the 27 severe cases (92.6%). The abnormally wide surface intercanthal distance was matched by an abnormally wide bony interorbital distance in 57 of the 63 patients (90.5%). In the other six patients (3 with the mild form, 1 with the moderate form and 2 with the severe form) the bony widths were near the upper limit of the normal range (mean + 2 standard deviations).

Adolescent↗
PubMed1986

Maxillary growth following LeFort III advancement surgery in Crouzon, Apert, and Pfeiffer syndromes.

This was a cephalometric study of maxillary growth following LeFort III osteotomy in children with Crouzon, Apert, and Pfeiffer (CAP) syndromes. Nineteen children who had undergone LeFort III advancement osteotomies were followed postoperatively for an average of 5.3 years. Data for horizontal and vertical maxillary growth increments were obtained and compared with data of a control group of unoperated CAP children and with normal data. The findings indicate that horizontal maxillary growth following surgical treatment is negligible (less than 0.1 mm/yr), and differs from unoperated CAP children (0.7 mm/yr) and normal children (1.3 mm/yr). Vertical maxillary growth following surgery is identical to that in unoperated CAP and normal children, amounting to 1.3 mm/yr. The LeFort III osteotomy during childhood is a justifiable procedure for physiologic and psychologic reasons. Horizontal maxillary growth, for all practical purposes, is eliminated by this procedure and a subsequent maxillary advancement is invariably required at the completion of growth.

Acrocephalosyndactylia↗
PubMed1986

Stability of Le Fort III advancement surgery in children with Crouzon's, Apert's, and Pfeiffer's syndromes.

The records of 19 children who had undergone Le Fort III advancement surgery were used to assess the stability of the midfacial segment following surgery. Cephalometric radiographs of each individual were analyzed longitudinally. The average forward movement of the maxilla at the time of surgery was 12.4 mm. The average amount of relapse for the group was 9.4 percent in the horizontal plane of space and 5.5 percent in the vertical plane of space. The data obtained from this sample indicate that the Le Fort III advancement is a relatively stable procedure. The amount of relapse or stability that occurs following Le Fort III advancement is related to rigid stabilization of the midfacial segment with buttressing bone grafts, transosteotomy wiring, and intermaxillary fixation or bone plating during the postoperative healing phase.

Acrocephalosyndactylia↗