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Biomedical subjects

W P Rock

Publications and source records attributed to W P Rock.

At least 19 recordsLinked to original sources
PubMed2006

A cephalometric comparison of skulls from the fourteenth, sixteenth and twentieth centuries.

OBJECTIVES: To evaluate changes in the size and shape of the skull and jaws in British populations between the thirteenth and twentieth centuries. METHOD: Lateral cephalometric radiograms were obtained from skulls of three groups of subjects: 30 skulls were from the remains of those who died in the London Black Death epidemic of 1348, 54 skulls were recovered from the wreck of the Mary Rose which sank in 1545 and 31 skulls were representative of modern cephalometric values. RESULTS: Horizontal measurements in the base of the anterior cranial fossa and in the maxillary complex were greater in the modern group than in the medieval skulls. Cranial vault measurements were significantly higher (P=0.000) in the twentieth century skulls, especially in the anterior cranial fossa. CONCLUSION: Results suggest that our medieval ancestors had more prominent faces and smaller cranial vaults than modern man.

Adolescent↗
PubMed2006

Does mentoring have a role in orthodontic training programmes?

Changes within the dental profession have led to a possible need for mentoring and consideration is given in this paper to different structures for possible implementation of mentoring schemes. Further information is needed to determine whether or not mentoring may play a useful role in dentistry in general and in orthodontic specialist training in particular.

Education, Dental, Graduate↗
PubMed2006

A clinical comparison of bracket bond failures in association with direct and indirect bonding.

OBJECTIVE: To compare bond failure rates between direct and indirect techniques for bonding orthodontic brackets. DESIGN: A two-centre single blinded prospective randomized controlled clinical trial. MATERIALS AND METHODS: This study was undertaken at the Birmingham Dental Hospital and Good Hope Hospital, Sutton Coldfield. Thirty-three subjects meeting the inclusion criteria were selected from orthodontic waiting lists and assigned to either of two study groups according to a split-mouth study design. The number and site of bracket failures between tooth types was recorded over 1 year. Statistical analysis was carried out using chi-square tests. RESULTS: Brackets were lost from 14 of the 553 teeth bonded, giving an overall bond failure rate of 2.5%. There were no significant differences in bond failures between direct and indirect bonding or in the tooth types of the failures. CONCLUSIONS: There was no significant difference in the bond failure rates between direct and indirect bonding.

Acid Etching, Dental↗
PubMed2005

A jig for measuring incisor inclination.

The aim of this study was to design and construct a jig for measuring the inclination of the upper incisors to the maxillary plane and of the lower incisors to the mandibular plane. After several prototypes had been tested, the required properties for a successful jig were identified and a simple inexpensive device was produced. Measurements obtained when using the jig on 51 subjects were compared with cephalometric values by means of regression analysis. This revealed that measurements obtained using the jig against the upper and then the lower incisor crowns could be converted to cephalometric incisor angulations with 96 per cent accuracy to 10 degrees, by adding 23 and 3 degrees, respectively. The jig was accurate to 5 degrees on 69 per cent of occasions for the upper teeth. The 5 degrees accuracy with the lower incisors was only 27 per cent, although over a 6 degree range it improved to 78 per cent. For upper and lower tooth measurements combined, the jig was accurate to within 6 degrees on 75 per cent of occasions.

Cephalometry↗
PubMed2005

A randomized controlled trial comparing the quadhelix and the expansion arch for the correction of crossbite.

OBJECTIVE: To compare the use of the quadhelix and the expansion arch for the correction of crossbite. DESIGN: A prospective randomized clinical trial supported by preliminary laboratory measurements. The null hypothesis was that there was no difference in the clinical effectiveness of the two expansion devices in terms of crossbite correction. SETTING: Queen's Hospital, Burton on Trent and The University of Birmingham, School of Dentistry. PARTICIPANTS: The first 60 patients on the orthodontic waiting list at Queen's Hospital who required expansion of the maxillary arch as part of the treatment plan were allocated to be treated with either a quadhelix or an expansion arch by random allocation. Twenty-eight and 27 members of each respective group completed the study. MATERIALS: Commercial quadhelix arches (3M Unitek) and custom-made expansion arches METHODS: The force produced by the type of expansion arches used in the study was measured in the laboratory to be 1.8 N at 10 mm of expansion. Quadhelix arches of sizes 2 and 3 were found to produce equivalent forces at 5 and 7 mm of expansion respectively. Either expansion device was fitted to the 60 participants according to random allocation and expanded by the standard amount. Intermolar and intercanine expansion was measured after 4, 8 and 12 weeks. Patient opinion was assessed by using a questionnaire. RESULTS: The quadhelix and the expansion arch were equally effective in producing expansion (p>0.05). After 12 weeks, the two types of archwire had produced mean intermolar expansions of 4.54 and 5.09 mm and intercanine expansions of 1.41 and 2.12 mm, respectively. Both types of arch were reported as uncomfortable by a majority of patients, the quadhelix affected mainly the tongue and the expansion arch the cheeks. The appearance of the quadhelix was disliked by 25% of participants, while 70% disliked the expansion arch. CONCLUSIONS: The null hypothesis was confirmed. However, the expansion arch had several advantages that made it a cheap alternative to the quadhelix for crossbite expansion, because it can be made and fitted at the chairside.

Adolescent↗
PubMed2005

British Orthodontic Society, Chapman Prize Winner 2003. A novel in vitro culture model to investigate the reaction of the dentine-pulp complex to orthodontic force.

OBJECTIVE: To develop a novel mandible slice organ culture model to investigate the effects of externally applied force on the dentine-pulp complex. DESIGN: In vitro organ culture. SETTING: School of Dentistry, Birmingham, UK. MATERIALS AND METHODS: Transverse 2 mm thick sections were cut from the mandibles of five 28-day-old male Wistar rats. Serial sections were used for control and test pairs. Springs made from 0.016-inch and 0.019 x 0.025-inch stainless steel wires were used to apply a 50 g tensile or compressive force, respectively, to test specimens. Control and test specimens were cultured for 5 days in a humidified incubator with 5% CO(2) at 37 degrees C and processed for routine histological investigation. Nine more rats were used to provide control and compression test pairs where the pulps were extirpated after 3 days culture and total RNA isolated for gene expression analysis by reverse transcriptase polymerase chain reaction (RT-PCR). RESULTS: Histology showed the dental and supporting tissues maintained a healthy appearance in the control cultures after culture. Histomorphometric analysis revealed a 20-27% increase in pulp fibroblast density in test specimens compared with controls. Gene expression analyses revealed up-regulation in the test groups of PCNA, c-Myc, Collagen 1alpha, TGF-beta1 and alkaline phosphatase, whilst expression of osteocalcin was reduced. CONCLUSIONS: The results demonstrated that the present organ culture technique provides a valuable in vitro experimental model for studying the effects of externally applied forces. These forces stimulated a cellular response in the pulp chamber characterized by altered gene expression and proliferation of fibroblasts; the latter being unaffected by the nature of the force in terms of compression or tension.

Alkaline Phosphatase↗
PubMed2005

The effect of socio-economic status and ethnicity on the comparative oral health of Asian and White Caucasian 12-year-old children.

OBJECTIVE: To investigate the oral health of 12-year-old children of different deprivation but similar fluoridation status from South Asian and White Caucasian ethnic groups. DESIGN: An epidemiological survey of 12-year-old children using BASCD criteria, with additional tooth erosion, ethnic classification and postcode data. CLINICAL SETTING: Examinations were completed in schools in Leicestershire and Rutland, England, UK. Participants A random sample of 1,753 12-year-old children from all schools in the study area. MAIN OUTCOME MEASURES: Caries experience was measured using the DMFT index diagnosed at the caries into dentine (D3) threshold, and tooth erosion using the index employed in the Children's Dental Health UK study reported in 1993. RESULTS: The overall prevalence of caries was greater in White than Asian children, but varied at different levels of deprivation and amongst different Asian religious groups. There was a significant positive association between caries and deprivation for White children, but the reverse was true for non-Muslim Asians. White Low Deprivation children had significantly less tooth erosion, but erosion experience increased with decreasing deprivation in non-Muslim Asians. CONCLUSIONS: Oral health is associated with ethnicity and linked to deprivation on an ethnic basis. The intra-Asian dental health disadvantage found in the primary dentition of Muslim children is perpetuated into the permanent dentition.

Asian People↗
PubMed2004

The prevalence of tooth erosion in 12-year-old children.

OBJECTIVES: To establish the prevalence of tooth erosion in a representative sample of 12-year-old children in Leicestershire and Rutland. To determine if gender, ethnic group, deprivation or caries experience influences the prevalence of erosion. METHODS: A random sample of 1,753 12-year-olds resident in Leicestershire and Rutland were examined in 62 schools; 906 were boys and 847 girls; 1,379 were Caucasian and 316 Asian. Tooth erosion was assessed using the index employed in the survey of Children's Dental Health in England and Wales (1993). The Townsend index was used to record deprivation. RESULTS: Tooth erosion was found in 59.7% of the children, with 2.7% exhibiting exposed dentine. Significantly more boys than girls; Caucasian than Asian children; and those with caries experience, had erosion present (chi-square for all P<0.01). Overall no significant difference was found between deprivation categories, however socio-economically advantaged Caucasian children had significantly less tooth erosion than other groups. CONCLUSIONS: There was a high prevalence of tooth erosion in 12-year-old children. Significantly more erosion occurred in boys than girls, and culture appeared to influence prevalence. Children with caries experience had a higher prevalence of erosion than those without caries, which may reflect a lower level of dietary care. Deprivation seemed to affect the prevalence of tooth erosion in Caucasian children.

Asian People↗
PubMed2004

A multifactorial analysis of factors associated with dental erosion.

OBJECTIVES: This study prospectively examines the relationship of possible aetiological factors to the presence of tooth erosion in a cohort of children. PATIENTS AND METHODS: A random sample of 1,753 children was examined at age 12 and 1,308 of the same children were re-examined at age 14 years. The children were asked to complete questionnaires on both occasions, 1,149 subjects gave usable replies. The erosion index used was based upon the 1993 Survey of Children's Dental Health. Results were analysed using logistic regression. RESULTS: At age 12 significant positive associations were found between erosion and decay experience (odds ratio [OR] = 1.48), drinking fruit juice (OR = 1.42) or fizzy pop (OR = 1.59-2.52, depending on amount and frequency). The presence of calculus (OR 0.48) or eating fruit other than apples or citrus fruit (OR 0.48) reduced the chances of erosion. High consumption of carbonated drinks increased the odds of erosion being present at 12 years by 252% and was a strong predictor of the amount of erosion found at age 14. CONCLUSIONS: Of the factors investigated, a history of dental caries and a high consumption of carbonated drinks were most closely related to the presence of dental erosion. The risk of erosion bore a strong relationship to the amount and frequency of carbonated drink consumption.

Carbonated Beverages↗
PubMed2004

Factors affecting friction in the pre-adjusted appliance.

A jig was constructed to measure the frictional forces created by various tip and torque values in association with two types of straightwire bracket moving along tainless steel (SS) archwires. Forces were measured during translation of the bracket using an Instron machine. Steel and cobalt chromium brackets were tested in association with 0.019 x 0.025 and 0.021 x 0.025 inch steel archwires at tips from 0 to 3 degrees and torque values in 2 degree increments from 0 to 6 degrees. The mean values for static (2.2 N) and kinetic (2.1 N) friction were very similar (P = 0.71), as were the overall friction values for stainless steel (2.1 N) and chromium cobalt (2.2 N) brackets of similar dimensions (P = 0.44). Use of 0.021 x 0.025 inch wire produced three times as much friction as 0.019 x 0.025 inch wire, 3.0 N against 1.2 N (P < 0.01). Increased tip and torque were associated with highly significant increases in friction (P < 0.01). Every degree of tip produced approximately twice as much friction as comparable torque. The main conclusion of the study was that space closure should be completed on a 0.019 x 0.025 inch archwire before a 0.021 x 0.025 inch wire is used to complete tooth alignment.

Analysis of Variance↗
PubMed2004

A randomized clinical trial comparing the accuracy of direct versus indirect bracket placement.

OBJECTIVE: To determine the accuracy of direct or indirect bracket placement. DESIGN: A prospective, randomized comparison of 2 different methods of bracket placement. SETTING: Queens Hospital, Burton upon Trent, UK between February and May 2001. MATERIALS AND METHOD: Twenty-six consecutive patients requiring upper and lower MBT trade mark pre-adjusted Edgewise appliances had their labial segments bonded directly or indirectly according to a split mouth system of allocation. Before and after bond-up all brackets were photographed and measured from tracings to determine positional differences from the ideal. RESULTS: Using ANOVA (General Linear Model), vertical errors were found to be greater than those in the horizontal plane, which in turn were greater than angular errors (p<0.05). Errors were greater in the maxillary arch than in the mandibular arch. There was no significant difference between the mean errors produced by the two methods of bracket placement. CONCLUSIONS: Mean bracket placement errors were similar with both techniques.

Dental Bonding↗
PubMed2004

A comparison of three light curing units for bonding adhesive pre-coated brackets.

OBJECTIVE: To compare the effectiveness of three curing lights of different types. DESIGN: Prospective randomized laboratory investigations. MATERIALS AND METHOD: Adhesive pre-coated orthodontic brackets were bonded to 9 groups of extracted premolars and the adhesive was cured using three different curing lights, each at three different times. Bond strength was tested using a shear/peel method. RESULTS: The plasma light had 3 times the light intensity of the standard quartz halogen light. The curing times recommended by the manufacturers were 2 seconds for the plasma light, 10 seconds for the high intensity quartz halogen light and 20 seconds for the standard one. Mean debond stresses with these cure times were 9.36, 11.77 and 12.00 MPa, respectively, p<0.04. Increasing the plasma light cure to 4 seconds increased the mean debond stress to 11.19 MPa, similar to that for the other lights, p=0.62. CONCLUSIONS: Use of a plasma light confers worthwhile time savings when bonding orthodontic brackets, whilst producing bonds of equivalent strength to those found with quartz halogen lights.

Adhesives↗
PubMed2003

The progression of tooth erosion in a cohort of adolescents of mixed ethnicity.

OBJECTIVES: To establish the prevalence of tooth erosion in a sample of 12-year-old children and to monitor changes over the subsequent 2 years. METHODS: A random sample of 1753 children aged 12 years was drawn from all 62 state maintained schools in Leicestershire. A total of 1308 were re-examined 2 years later. Erosion was recorded on incisors and first molars using an erosion index based upon that from the Children's Dental Health in the United Kingdom 1993 survey. A score was also allocated to each subject according to the most advanced lesion in the mouth. RESULTS: Erosion was present in 56.3% of subjects at age 12 and 64.1% at age 14. Deep enamel or dentine was eroded in 4.9% and 13.1% of subjects, respectively, at the same ages. One hundred and sixty-one (12.3%) children who were erosion-free at 12 years of age developed erosion over the subsequent 2 years. Boys had more erosion than girls, as did white compared to Asian children. Associations were found between erosion experience and social deprivation. CONCLUSION: New erosive lesions developed in 12.3% of the subjects between the ages of 12 and 14 years. New or more advanced lesions were seen in 27% of the children over the 2 years of the study. Males, white children and social deprivation were significantly associated with erosion experience.

Adolescent↗
PubMed2003

Asthma and tooth erosion. Is there an association?

OBJECTIVES: To investigate whether there is an association between asthma and tooth erosion in a representative random sample of adolescents in the East Midlands. METHODS: A random sample of 1753 12-year-old children was examined in all schools in Leicestershire and Rutland. 1308 children were re-examined 2 years later. Tooth erosion was assessed using the index employed in the Children's Dental Health in the UK Survey 1993. Asthma presence was recorded on a self-completed questionnaire at the time of the 12 years examination. Data on asthma prescribing over a one year period was obtained from the Prescription Pricing Authority. RESULTS: Asthma was present in 16.8% of 12-year-olds. Tooth erosion was recorded in 59% of children with asthma and in 59.7% who were asthma free. There was no significant difference in erosion prevalence between asthmatics and asthma free in a cohort of children at age 12 or 14 years, and the incidence of erosion was 12.8% and 12.3%, respectively. 88% of drugs prescribed for treatment of asthma had a pH above the critical pH of 5.5. CONCLUSION: There was no association between asthma and tooth erosion. The majority of drugs prescribed for the treatment of asthma are not potentially erosive.

Adolescent↗
PubMed2003

The load/deflection characteristics of thermally activated orthodontic archwires.

The objective of the study was to investigate the load/deflection characteristics of three commercially available thermally active nickel-titanium orthodontic archwires using a standard nickel-titanium archwire as a control. The thermally active wires were Regency Thermal, Orthoform, and Eurotherm and the control was Memory. Round 0.4 mm and rectangular 0.4 x 0.56 mm wires were subjected to 2 and 4 mm of deflection in a water bath at temperatures of 20, 30, and 40 degrees C and forces were measured in three-point bend and phantom head situations. Analysis of variance revealed that, irrespective of the test set up and wire type, wire size had a significant effect (P < 0.001) on the forces produced. An increase in size from 0.4 mm round to 0.4 x 0.56 mm rectangular wire approximately doubled the force values for a given deflection. The effect of wire deflection on the force values varied according to the test system, forces being much higher in the phantom head tests than in the beam tests. In the beam tests, an increase in wire deflection from 2 to 4 mm had no significant effect on the forces exerted, but in the phantom head tests the forces produced by each wire at 4 mm deflection were four to five times greater than those at 2 mm deflection. Each of the thermally active wires produced less force that the non-thermally active wire. However, there was a large variation between the three types of thermally active wire. In the beam tests each 10 degrees C rise in temperature from 20 to 40 degrees C had a highly significant effect on the force produced by each thermoelastic wire (P < 0.001). In the phantom head tests there were significant force increases between 20 and 30 degrees C (P < 0.001), but between 30 and 40 degrees C the forces did not change significantly.

Analysis of Variance↗
PubMed2003

Orthodontic retention: why when and how?

Retention is normally required after active orthodontic tooth movement to hold the teeth in their new positions. This article reviews the principles of orthodontic retention and describes common retention regimes and appliances.

Humans↗
PubMed2003

Awareness of tooth erosion in 12 year old children and primary care dental practitioners.

OBJECTIVES: To compare the knowledge of tooth erosion in a sample of 12 year old children with that of the dentists responsible for their care and also to compare the giving and receiving of advice concerning erosion. METHOD: A random sample of 1753 children from all 62 state maintained schools in Leicestershire completed questionnaires. Questionnaires were also sent to the 257 General Dental Practitioners in Leicestershire. RESULTS: 1686 (96.2%) of children and 227 (82.5%) of dentists returned forms that could be analysed. 36% of dentists reported that they frequently noticed erosion on the teeth of their patients but 67.7% of dentists believed that less than 25% of 12 year olds had any erosion. 67.5% of dentists advised their patients about erosion only occasionally or rarely. Only 34.2% of the children had heard of tooth erosion and only 8.4% could recall their dentist mentioning the condition. 40% of children believed that the best way to avoid erosion was regular tooth brushing. CONCLUSION: The levels of awareness were low for both dentists and patients and the messages that were given by dentists were either forgotten or misunderstood by the children, or they were incorrect. Better communication and understanding is needed in this important area.

Child↗