Biomedical subjects

W P Rock

Publications and source records attributed to W P Rock.

At least 19 recordsLinked to original sources

PubMed2000

Influence of orthodontic treatment on development of third molars.

We aimed to find out whether extraction of lower premolars and subsequent closure of the space by a fixed appliance influenced the chances of mandibular third molars erupting. We compared angular and linear measurements of lower third molars on dental panoramic tomograms in 30 orthodontic patients with similar measurements from 30 patients with impacted third molars in intact arches. We found that the mesial angulation of lower third molars was reduced from 50 degrees to 43 degrees by orthodontic treatment (P< 0.001). Distance to the occlusal plane was reduced from 12 mm to 10 mm (P< 0.001). The space available increased from 4 mm to 11 mm (P< 0.001). We conclude that extraction of lower premolars and orthodontic treatment to achieve complete closure of the space allowed the positions of many impacted lower third molars to improve significantly.

Adolescent↗

PubMed1999

An appraisal of the Peer Assessment Rating (PAR) Index and a suggested new weighting system.

The PAR Index was developed to measure treatment outcome in orthodontics. Validity was improved by weighting the scores of some components to reflect their relative importance. However, the index still has limitations, principally due to the high weight assigned to overjet. Difficulties also arise from the application of one weighting system to all malocclusions, since occlusal features vary in importance in different classes of malocclusion. The present study examined PAR Index validity using orthodontic consultant assessments as the 'Gold standard' and clinical ranking of occlusal features and statistical modelling to derive a new weighting system, separate for each malocclusion class. Discriminant and regression analyses were used to derive new criteria for measuring treatment outcome. As a result a new and more sensitive method of assessment is suggested which utilizes a combination of point and percentage reductions in PAR scores. This was found to have better correlations with the 'Gold standard' than the PAR nomogram.

Dental Occlusion↗

PubMed1999

An ex vivo investigation into the bond strength of orthodontic brackets and adhesive systems.

The aim of this study was to compare the shear bond strength of Adhesive Precoated Brackets (APC) with that of two types of uncoated bracket bases, Straight-Wire and Dyna-Lock. Two types of orthodontic adhesives were used, Transbond XT and Right-On. Three different curing times were evaluated with the APC brackets in order to find the best. Adhesive remnants on the enamel surface following debond were evaluated using the Adhesive Remnant Index (Artun and Bergland, 1984). Bond strengths ranged from 11.00 to 22.08 MPa. For both types of brackets Transbond produced a significant increase in bond strength compared to Right-On. The Dyna-Lock/Right-On combination produced the poorest results. APC brackets cured for 40 s had similar bond strengths to uncoated brackets fixed by means of Transbond. Overall, 79 per cent of specimens had less than half the tooth surface covered with adhesive following debond. Significantly more adhesive remained on tooth surfaces following debond of the Straight-Wire/Right-On group than any other bracket/adhesive combination. Bond strengths were higher with light-cured Transbond than with chemically-cured Right-On. When Transbond is used in association with APC brackets a 40-second cure time is recommended.

Adhesiveness↗

PubMed1999

Distortion of metallic orthodontic brackets after clinical use and debond by two methods.

The objective of this paper was to compare distortion of the tie wings and bases of metallic orthodontic brackets following clinical use and after debond by either of two methods, and took the form of a prospective random control trial. Five-hundred-and-seven brackets were debonded using either bracket removing pliers or a lift off debonding instrument (LODI). By a system of random allocation contralateral opposing quadrants were debonded with a 0.019 x 0.025-inch archwire either in place or removed. After debond brackets were tested for slot closure by the fit of rectangular test wires from 0.016 x 0.022 to 0.021 x 0.025 inch in size. The LODI produced few slot closures sufficient to affect the fit of all but the largest test wire. Bracket removing pliers used after removal of the archwire produced significantly greater numbers of distorted brackets in response to testing with all but the largest wire. With the 0.021 x 0.025 inch wire in place the presence or absence of the archwire at the time of debond made no difference to the number of slot closures. Ten per cent of the brackets debonded using bracket removing pliers had distorted bases, no base damage was produced by the LODI. The use of bracket removing pliers at debond caused significantly more slot closures than use of the LODI. When bracket removing pliers are used the archwire should be left in place at the time of debond since this reduces the number of distortions.

Dental Alloys↗

PubMed1999

Factors affecting the shear bond strength of orthodontic brackets to porcelain.

The aim of this investigation was to establish a regime for orthodontic bonding to feldspathic porcelain, which ensures adequate bond strength (6-8 MPa) with minimal damage on debond and consisted of an ex vivo investigation measuring the effects of porcelain surface preparation and thermocycling on shear bond strength of orthodontic brackets. One-hundred-and-twenty feldspathic porcelain bonded crown surfaces were divided into 12 equally-sized groups to assess the effects of: (1) glaze removal, (2) application of hydrofluoric acid, phosphoric acid, or omission of acid treatment, and (3) silane priming upon the bond strength of premolar brackets bonded with Right-on (TM) composite resin adhesive. Specimens were subjected to thermocycling and then to shear debonding forces on an Instron machine. Removal of the porcelain glaze, or use of hydrofluoric acid, prior to bonding were found to be unnecessary to secure the target bond strength. Hydrofluoric acid application was associated with increased porcelain surface damage. Thermocycling caused a significant reduction in shear bond strength to porcelain (P < 0*001). The best regime for orthodontic bonding to feldspathic porcelain was to apply phosphoric acid for 60 seconds, and prime with silane prior to bonding. Usually the porcelain surfaces could be repolished. Refereed Paper

Acid Etching, Dental↗

PubMed1998

Clinical performance of orthodontic brackets and adhesive systems: a randomized clinical trial.

The aim of the study was to evaluate and compare the clinical performance of adhesive precoated brackets (APC) with that of two types of uncoated bracket bases, Straight-Wire and Dyna-Lock, bonded using two types of orthodontic adhesives, Transbond XT, and Right-On. Forty consecutive orthodontic patients entered the trial and 607 brackets were bonded. The incidence and site of first time bond failures were recorded over a period of 1 year. The time required for bonding was also recorded. The overall bond failure rate was 6.6 per cent. There were no significant differences between the failure rates of the five groups, or between the upper and lower arch. However, significantly more brackets failed on the left side than on the right. Premolar brackets were lost most often, whilst incisor brackets failed least. No association was found between bond failure and time elapsed since bonding. Bonding time was least with Right-On adhesive. There were no significant differences between bonding times using APC or Transbond. Results of the present study conflict with those of a previous ex vivo study by the authors, using the same materials and bonding technique. Suggested reasons for this are discussed.

Analysis of Variance↗

PubMed1998

A comparison of clinical and photographic scoring using the TF and modified DDE indices.

OBJECTIVE: To compare the results of recording enamel opacities using the TF and modified DDE indices. DESIGN: Enamel opacities on the maxillary central incisors were recorded two weeks apart. On the first occasion scoring was according to the criteria of the TF index and on the second occasion the modified DDE index was used. An intraoral colour slide photograph was taken of the teeth of each subject and these were scored on two occasions in random order, first using the TF index and secondly using the modified DDE index. SUBJECTS: Three hundred and twenty-five 9-year-old children who were life time residents in an area where the domestic water was fluoridated at one part per million. RESULTS: Agreement between clinical and photograph scoring was good for both TF and modified DDE indices, Spearman's Rank Correlation Coefficients being 0.77 and 0.69 respectively. There was also good agreement between the distribution of scores for the two indices as indicated by Coefficients of 0.75 for clinical scores and 0.76 for photographic scores. CONCLUSIONS: There was good agreement between the TF and modified DDE indices when recording the distribution of milder types of enamel opacities in a population of 9-year-old children.

Child↗

PubMed1997

The relationship between reported toothpaste usage in infancy and fluorosis of permanent incisors.

OBJECTIVE: To examine a possible relationship between reported toothbrushing habits in infancy and fluorosis of permanent maxillary incisors at age 8-9 years. DESIGN: Comparison of clinical findings with retrospective survey data. SETTING: Five primary schools in the City of Birmingham where the water is fluoridated at 1.0 mg F/l. SUBJECT AND METHODS: Results of clinical examinations were compared with historical data collected via parental questionnaires. Maxillary central incisors of 325 consecutive children were examined for fluorosis clinically and photographically according to the criteria of the Modified Thylstrup and Fejerskov Index. 112 children had fluorosis and 213 did not. Information concerning toothbrushing habits in infancy was obtained via a questionnaire to parents who were also asked to add paste to a brush in a similar way to when the children were small. From a combination of questionnaire replies and paste weights the amount of fluoride that each child may have ingested from toothpaste each day was then estimated. RESULTS: Highly significant associations were found between estimated fluoride ingestion from toothpaste and fluorosis. The mean DMF score of the fluorosis group was half that of the fluorosis-free children. The prevalence of fluorosis among children in ACORN group A-C was significantly greater than in groups D-F. CONCLUSIONS: The results of the study suggest that toothpaste swallowing may be a factor in the production of fluorosis.

Child↗

PubMed1997

Bracket recycling--who does what?

At present there is debate concerning the practice of recycling orthodontic components. A survey of 300 members of the British Orthodontic Society showed that 47.5 per cent of respondents recycled metal brackets and that more specialist practitioners than consultants did so (p < 0.001). Only 7.2 per cent of the orthodontists who recycled brackets informed their patients that recycled brackets were used.

Equipment Reuse↗

PubMed1997

A Hypertext tutorial for teaching cephalometrics.

Hypertext is a non-linear method of text presentation. It necessitates the use of a computer to store data as a series of nodes that can be called up in any desired sequence and, as such, is a new form of discovery-based learning. This paper describes a Hypertext tutorial in cephalometrics and its subsequent testing on first-year clinical dental students. Students were divided into two groups: the first received a conventional lecture; the second used the Hypertext tutorial. Testing was by means of conventional multiple choice questions. The results showed that there was no statistically significant difference between the two groups, although the computer tutor was shown more consistently to improve the knowledge of the students than did the conventional lecture. Most students who used the computer program found it enjoyable, but time consuming; less than half found it easy to follow.

Attitude↗

PubMed1996

A study of letters between general dental practitioners and consultant orthodontists.

A survey was undertaken involving 268 general dental practitioners and 13 orthodontic consultants to determine the content of letters passed between them. There was good agreement between the two sets of respondents as to the appropriate contents of a letter. The feature of a letter least valued by both dentists and consultants was a detailed description of the case, although 54% of consultants described cases at some length when replying to referrers. The information that GDPs valued most highly was a treatment plan, the date on which the patient was seen and the name of the clinician involved, a short case description and the length of time before treatment would being if the patient was accepted for specialist treatment.

Communication↗

PubMed1996

A comparative study of fluoride-releasing composite resin and glass ionomer materials used as fissure sealants.

OBJECTIVES: The objectives of the study were to investigate the clinical use of two fluoride-releasing fissure sealants and to study fluoride release under laboratory conditions. METHODS: In the clinical part of the study the two materials, FluroShield and Baseline, were applied to matched contralateral caries-free first permanent molars in 86 children aged 7-8 years. In the laboratory study fluoride release from each material was measured using a model cavity system. RESULTS: After 3 years FluroShield was intact on 70% of teeth. Retention was significantly better on lower molars than upper molars. Baseline was lost from all except two teeth within 6 months. After 3 years, caries had affected four teeth sealed with FluroShield and 24 teeth sealed with Baseline; this difference was highly significant. The laboratory study showed that FluroShield released twice as much fluoride over 9 days than did Baseline. Long term studies using FluroShield showed a small steady fluoride release over 6 months. CONCLUSIONS: The conclusion of the study was that FluroShield was a much more effective fissure sealant than Baseline. The clinical performance of FluroShield was comparable to that of other inert composite resin sealants and superior to that of fluoride-releasing sealants used previously.

Bisphenol A-Glycidyl Methacrylate↗

PubMed1996

The effect of etch time and debond interval upon the shear bond strength of metallic orthodontic brackets.

Groups of orthodontic brackets were attached to enamel after etching for 15, 30 or 60 seconds. They were debonded by shear forces after 5 or 15 minutes, or 24 hours. The 15 seconds etch/5 minutes debond time specimens had much lower shear strengths than other groups. Sixty-second specimens showed evidence of tooth surface damage after debonding. Fifteen seconds of etching is therefore recommended routinely for bonding brackets. If a bracket is to be ligated within 5 minutes of placement, 30 seconds etching is recommended. A 60-second etch is considered too severe and should not be used.

Acid Etching, Dental↗

PubMed1996

Orthodontic treatment planning by general dental practitioners.

A group of 30 general dental practitioners were asked to plan treatment for a series of 10 Class II division 1 malocclusions of graded severity. The results were assessed against a gold standard provided by three consultants. Only 14 per cent of practitioner treatment plans agreed with the gold standard and agreement was worst for those cases requiring the use of headgear. When consultants and General Dental Practitioners (GDPs) were asked whether a case should be referred for advice before the GDP began treatment, 64 per cent of GDP decisions agreed with those of the consultants. On 13 per cent of occasions, however, the GDP would have initiated incorrect treatment without seeking consultant advice.

Adolescent↗

PubMed1995

A study comparing the prevalence and distribution of traumatic dental injuries among 10-12-year-old children in an urban and in a rural area of Jordan.

The aim of this study was to investigate the prevalence, aetiology and types of injuries to permanent incisors among 459 Jordanian schoolchildren aged 10-12 years, 234 from urban Amman and 225 from rural South Shouna. The prevalence of injuries in Amman was 19.2% (23.9% in boys, and 14.9% in girls) and in South Shouna 15.5% (19.1% in boys and 12.2 in girls). Significantly more boys than girls suffered injury. The difference in prevalence between urban and rural children was not statistically significant. The most common type of injury in both communities was enamel fracture, and the most common causes of injury were falls and collisions with other children. Children with an overjet greater than 5 mm sustained significantly more injuries to the incisor teeth than children with normal overjet.

Adolescent↗

PubMed1995

The effects of archwire forces on incisor intrusion.

The forces exerted by archwires were measured in association with both Begg and Straight-Wire attachments. Seven stainless steel and three nickel-titanium wires were tested at vertical deflections equivalent to 20, 30, and 40 degrees, these being incorporated via anchor bends or reverse curve of Spee as appropriate to each system. All seven brands of stainless steel arches demonstrated similar performance. An increase in archwire diameter from 0.016 to 0.018 inch increased intrusive forces by 64 per cent for stainless steel and 58 per cent for nickel-titanium. Increasing anchor bend or reverse curve of Spee produced considerable force increases across the range of specimens. Begg archforms produced more force than Straight-Wire archforms of similar deflection when attached to molars only. Attachment of archwires to second premolars in addition to molars reduced the intrusive forces produced by Begg arches, but increased the forces of Straight-Wire arches.

Analysis of Variance↗

PubMed1994

Young children and fluoride toothpaste.

Studies have shown a higher prevalence of enamel mottling in children who live in fluoridated areas than in those from low fluoride areas. It is possible that the additive effect of fluoride ingestion from water and toothpaste may be responsible since it is known that young children may swallow up to half of the toothpaste on the brush. Parents must supervise toothbrushing for young children, low fluoride paste should be used, and the brush merely smeared with paste. The commonly recommended pea-sized quantity may be too much.

Child, Preschool↗

PubMed1993

Dental caries experience in Jordanian and English schoolchildren.

The dental caries experience of 6- and 12-year-old children in Jordan and England was compared. The 6-year-old Jordanian children had significantly higher dmft scores than the English children, largely due to the greater numbers of decayed teeth in Jordan. Mean DMFT scores for 12-year-old children were similar in the two countries, however, the DMFT totals included more decayed and missing teeth in Jordan and more filled teeth in England. In both countries there were significant differences between the caries experience of children from different social classes.

Analysis of Variance↗