Mandibular Distalisation for Tooth Wear in Patients Requiring Mandibular Protrusion for Sleep Apnoea.

BACKGROUND: Pathological tooth wear is an increasing concern and may require intervention and occlusal rehabilitation. Often the treatment includes distalisaton of the mandible to restore the dentition in centric relation. Obstructive sleep apnoea (OSA) is another condition treated my mandibular repositioning but in this case by an advancement appliance. The authors have a concern that there could be a group of patients with both conditions where distalisation for their tooth wear management would be contrary to their OSA treatment. This paper aims to look at this potential risk. METHODS: A literature search was carried out using the following keywords (OSA or sleep apnoea or apnea or snoring or AHI or Epworth score) and for tooth surface loss (TSL or distalisation or centric relation or tooth wear or full mouth rehabilitation). RESULTS: No studies were identified which considered the effect of mandibular distalisation on OSA. CONCLUSION: There is a theoretical risk that dental treatment involving distalisation may adversely affect patients at risk of OSA or worsening their condition due to the modification of airway patency. Further study is recommended.

Changes in Tooth Mobility and Position in an Established Dentition Following Placement of a New Restoration.

The aim of this study is to examine and evaluate physiologic tooth mobility and movement in different groups of patients. Four groups of patients were examined and recordings were taken. Group A1 consisted of 12 undergraduate students under the age of 30, A2 consisted of 11 members of staff over the age of 30 and A3 consisted of 9 patients with periodontal disease between the ages of 40-65 years old. The fourth Group B, 14 patients between 30-70 years old, received single-tooth restorations and recordings were taken immediately after, a month and four months following the cementation of the restoration. Patients in the first 3 groups showed no significant change in tooth mobility and movement between appointments. The fourth group demonstrated a non-statistically significant increase in tooth mobility following the cementation of the restoration due to the force applied on the occlusal surface of the tooth during the cementation process, while tooth movement was not observed beyond that of physiological tooth migration. Regardless of the age or the restorations a patient receives over the years, with careful occlusal consideration, no significant changes in tooth mobility and movement should be observed.

A Passive Noise Attenuation Earplug Designed to Minimise Unwanted Air Turbine Driven High-Speed Dental Drill Noise.

INTRODUCTION: Air turbine dental drill noise contains high-frequency components that are of concern for patients and dental staff. Meanwhile, verbal communication between the dentist and patient is essential. Conventional active noise-cancelling headphones are ineffective for dental drill noise and simply suppress all sound and hinder communication. METHOD: A compact passive earplug device was designed specifically to attenuate broadband high-frequency noise ranges from 5 to 8 kHz employing an array of quarter wavelength (QW) resonators. This device was 3D printed and tested against white noise to enhance the objectivity of analysis, using a calibrated ear and cheek simulator to effectively measure its performance. RESULTS: The results showed that the resonators produced an average reduction of 27 dB across the targeted frequency range. When compared with two proprietary passive earplugs, this developed passive device prototype was able to attenuate an average of 9 dB more across the target frequency range whilst delivering louder speech signals of 14 dB more. The results also show that using an array of resonators exhibits an accumulated effect of individual resonator performance. CONCLUSIONS: This low-cost passive device could have a place in the dental clinic to reduce unwanted drill noise equivalent to the white noise high frequency spectra tested.

Analysis of Posterior Zirconia Crowns with Vertical Margin Preparations.

BACKGROUND: The interest in vertical crown preparation is growing and several variations are presented in the dental literature but limited clinical outcome data exists for teeth prepared for a vertical finish line. AIM: To audit clinical outcomes for 73 teeth after vertical preparation for knife-edge zirconia crowns. METHOD: Seventy-three teeth had knife-edge zirconia crowns placed after vertical finish line preparation. The outcomes for these teeth were analysed from a retrospective audit of clinical records. RESULTS: The mean follow-up time was 21 months (SD: 10 months; range: 6-40). One tooth had to be extracted due to fracture at cervical level. One crown had to be re-made after margin fracture during try-in. No subsequent endodontic treatment was needed for any of the prepared teeth. No change in alveolar bone height was noted on radiographic follow-up. The mean bleeding score for the crowned teeth was higher than the mean bleeding score for a control tooth, but this was not statistically significant. CONCLUSION: This retrospective evaluation has shown favourable outcomes for 72 teeth after vertical preparation for knife-edge crowns. Longer follow-up is needed but the present results show that the technique is a viable procedure with potential advantages.

Survival of Direct Posterior Composites With and Without a Bulk Fill Base.

OBJECTIVES: Direct composite restorations are increasingly popular and a flowable bulk-fill base material (SDR, Dentsply) claims to minimise stress through a more flexible polymerisation process. This retrospective audit of restorations placed in general practice compares SDR based restorations with conventional composite restorations. METHODS: Restorations were all placed by one operator using a similar clinical technique and were audited as Group G, placed with a conventional layering composite (G-aenial, GC) and Group S which had a bulk-fill base of SDR (Dentsply) and then were covered with G-aenial (GC). Data regarding survival, post-operative sensitivity and mode of failure were recorded and analysed. RESULTS: In total 54 Group S restorations and 71 Group G restorations were followed for a minimum of 24 months. Group S had a 92.6% survival and Group G 93%. Group S was more prone to failure by tooth fracture (p=0.033). In both groups failure was more likely in larger cavities, in both those with an increased number of surfaces (p⟨0.001) and cuspal coverage (p=0.004). CONCLUSIONS: There appears to be similar survival of the two techniques in the short-term although there were significantly more tooth fractures in teeth restored with SDR.

Dimensional stability ofautoclave sterilised addition cured impressions and trays.

The aim of this study was to investigate the dimensional accuracy of impressions following sterilisation by autoclaving. Dental impressions (75) were of a dentoform containing 6 reference points. The impressions were split into 5 groups of 15, each group used a different impression technique. Groups were divided into 3 subgroups with 5 impressions as control, 5 for disinfection by Perform-ID and 5 being autoclaved. Measurements were made using a travelling light microscope. A minimal significant dimensional difference (0.010.05). The trays and materials tested were suitable for the autoclave sterilisation.

Do composite resin restorations protect cracked teeth? An in-vitro study.

Aims: To evaluate whether bonded resin composite restorations can effectively immobilise the tooth segments in teeth with a synthesised crack under loading, by exploring the impact of the restoration type (direct versus indirect composite resin) and restoration design (inlay versus onlay) on the fatigue resistance. Methods: Sound human third molars underwent large mesio-occluso-distal preparations and a groove was cut to simulate a crack. Standardised procedures were adopted and measures were taken during teeth selection so that systematic error and methodology bias were minimised. The teeth were randomly assigned to four groups. The specimens were submitted to cyclic loading and loaded until fracture or to a maximum of 185,000 cycles. The failure mode was recorded. Results: No failure was observed in 'direct' groups up to the 1000 N force. Survival analysis revealed statistically significant higher survival rates for 'direct' groups compared to 'indirect' groups (χ2 = 11.352, df = 1, p = 0.001) while there was no significant difference between 'inlay' and 'onlay' groups (χ2 = 0.015, df = 1, p = 0.901) (pooled data). Conclusions: Within the limitations of this in-vitro study, it can be concluded that the direct composite resin restorations sufficiently protected the cracked teeth regardless of the cavity design. As there was no statistically significant difference in survival rates between inlays and onlays it is not possible to favour one design type over the other.

Is the shortened dental arch still a satisfactory option?

Aims Dental practitioners may hold the view that missing posterior teeth should be replaced to ensure a healthy masticatory system and satisfactory oral function. However, the shortened dental arch (SDA) concept is still in use, but after 35 years is it acceptable? This review searches the literature for the evidence and opinions regarding the suitability of the SDA as a current treatment modality.Methods Medline and PubMed databases were searched for relevant terms, all the abstracts were assessed and articles selected according to the pre-set exclusion and inclusion criteria.Results The search yielded 1,895 articles and after the assessment of the abstracts and application of the exclusion and inclusion criteria, 44 articles were selected for this review. These included 11 cohort studies, two longitudinal studies, two animal studies, three cross sectional studies, eight clinical studies and 18 case control studies. There appears to be a trend over the past three decades for more papers to be opposed to the SDA concept.Conclusion Evidence that the SDA causes pathology is lacking. Clinicians, healthcare authorities and patients have shown favourable attitudes towards the SDA and this continues, although there is an increase in studies opposing the concept and some are dissatisfied with this option. The concept remains viable particularly for the medically compromised patient or where restorations are considered unsuitable but further more specific studies are warranted.

The management of cracked tooth syndrome in dental practice.

Cracked tooth syndrome is a commonly encountered condition in dental practice which frequently causes diagnostic and management challenges. This paper provides an overview of the diagnosis of this condition and goes on to discuss current short and long-term management strategies applicable to dental practitioners. This paper also covers the diagnosis and management of this common condition and aims to inform clinicians of the current thinking, as well as to provide an overview of the techniques commonly used in managing cracked tooth syndrome.

Eight year results with direct ceramic restorations (Cerana).

BACKGROUND: Single-visit system ceramic restorations are now in use to provide an alternative to resin-based materials. Inserts have been shown to improve characteristics of composite restorations. OBJECTIVE: To investigate the longevity of Cerana (Nordiska Dental, Sweden) in a prospective clinical trial. METHODS: Cerana restorations use matched drills with pre-etched and silanated leucite inserts cemented using a conventional restorative composite resin material. The results of 33 Cerana restorations up to eight years (25 Class I, eight class II) are presented. Restorations were reviewed and assessed by two examiners using modified USPHS criteria for anatomical form (AF) A-C, marginal adaptation (MA) A-D, surface roughness (SR) A-D, marginal discoloration (MD) A-C, colour match (CM) A-C and discomfort (DT) A-D as well as retention. RESULTS: The percentage of A scores for AF, MA, SR, MD, CM and DT at baseline (n = 33) were: 100, 100, 79, 100, 21, 100; after two years (n = 27) 100, 85, 33, 100, 19, 100 and after four years (n = 24) 96, 75, 17, 96, 25, 100. At six years (n = 20) 95, 70, 10, 95, 15, 100 and finally at the eight year recall (n = 18) 94, 61, 0, 94, 6, 100. AF was maintained in all except for one fractured marginal ridge. MA of the insert was good but composite was lost where exposed. SR increased to a B score for all inserts. MD at B grade was observed in 6% between composite and tooth but none between insert and composite. CM was stable in all cases. DT nil in all. There were no scores less than B. All reviewed restorations were retained, clinically acceptable and in function except for two lost for reasons not directly related to the Cerana insert. One class II restoration had a fractured marginal ridge but otherwise remains satisfactory. CONCLUSIONS: The results suggest that these restorations can be expected to perform well. Cerana is acceptable in terms of aesthetics, patient acceptance, occlusal wear and ease of use and is a good alternative for a single-visit, tooth coloured restoration in suitable cavity shapes.

Clinical performance of Rochette bridges used as immediate provisional restorations for single unit implants in general practice.

A retrospective clinical audit of the role and survival of 69 Rochette bridges used as immediate provisional restorations for single tooth, implant-retained crowns was carried out over the period between February 1991 and May 2001. In each case the extracted tooth was immediately temporised using a Rochette bridge with a single wing and pontic and cemented to the abutment tooth without any tooth preparation (Phase I). This bridge was removed at the time of implant placement and recemented (Phase II). At the implant exposure stage the bridge was removed and discarded. In Phase I, 15.9% of the bridges required recementation and 27.5% of the bridges required recementations in phase 2; 7.2% of the bridges required recementations in both phases. An 80% probability of survival was noted after an interval of 200 days for phase I and a 78% probability of survival over the same time interval was observed for Phase II. A significant debond rate was observed when the retainer was a canine in comparison to the other bridges in Phase I. In Phase I the spring cantilever debond rate was significantly higher than that observed on the other bridges. More debondings were observed in males (25.8%) compared with females (7.9%) in Phase I. More debondings were noted in the maxilla than in the mandible in Phase II. The performance characteristics of the metal acrylic Rochette bridge observed in this report supports the conclusion that this type of restoration is an effective means of immediate temporisation for patients undergoing single tooth implant retained restorations.

Mesencephalic innervation of the vibrissal follicle-sinus complex in the mouse embryo.

Peripheral projections of neurones whose cell bodies lie in the mesencephalic nucleus of the fifth cranial nerve, situated between the central grey and mesencephalic reticular formation, were studied in mouse embryos aged between day 9 and 15 and in postnatal day 1 mice. Nonspecific neural antibody staining allowed visualisation of the developing cranial nerves, in particular the descending mesencephalic tract. This facilitated successful dissection of the descending mesencephalic tract and trigeminal ganglion in the heads of fresh mouse embryos and postnatal mice. The fluorescent dye, 1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate (Dil), was injected into the descending mesencephalic tract in mouse embryos aged 12.5, 13.5 and 15 days of gestation and also into postnatal day 1 mice. Following a period of incubation, 100 microm sections were viewed under visible light and episcopic fluorescence. Mesencephalic neurones were observed to pass superiorly over the trigeminal ganglion and enter the maxillary division to innervate vibrissal follicle-sinus complexes, whilst none was observed innervating mandibular and maxillary intraoral structures. There was no fluorescent labelling in non-Dil injected control specimens. Using a highly specific neuronal tracer, this study shows that mesencephalic neurones in the periphery project exclusively to follicle sinus complexes in the developing mouse embryo and remain at least until postnatal day 1. These observations, contrary to those made in other animals, indicate a species specificity of mesencephalic peripheral projections.

A possible explanation for the response characteristics of multi-tooth periodontal ligament mechanoreceptors in the cat.

During the course of a study on the morphology of periodontal ligament mechanoreceptors it was observed that a direct relation, without intervening bone, existed between the mandibular canine and first premolar tooth roots in the cat. An area, representing a window in the alveolar septal bone, extended 2-3 mm from the apex towards the tooth crown. Ruffini nerve terminals were observed amongst the collagen bundles in the ligament between the roots of the two teeth. Light and electron microscopy were used to identify the receptors. It is proposed that a periodontal ligament mechanoreceptor can respond to forces applied to adjacent teeth; movement of both teeth need not occur. This may explain the observation made in the past that single periodontal ligament mechanoreceptors respond to forces applied to more than one tooth.

A comparative physiological and morphological study of periodontal ligament mechanoreceptors represented in the trigeminal ganglion and the mesencephalic nucleus of the cat.

A correlative morphological study was carried out on two electrophysiologically identified and located periodontal ligament mechanoreceptors in anaesthetised cats. One mechanoreceptor had its cell body in the mesencephalic nucleus and the other had its cell body in the trigeminal ganglion. Physiological recordings were made from each of their cell bodies. The two receptors were located by punctate and electrical stimuli in the labial aspect of the periodontal ligament of the left mandibular canine tooth. Both receptors had similar positions relative to the tooth apex and fulcrum and were situated in the labial part of the ligament in each tooth. The receptor loci were marked, and these regions were studied in a series of semi-thin and ultra-thin sections. Only Ruffini nerve endings were observed under each ink mark. Both Ruffini nerve endings branched, were unencapsulated and were incompletely surrounded by terminal Schwann cells with extensions projecting towards collagen bundles. The results indicate that periodontal ligament mechanoreceptors with cell bodies in the mesencephalic nucleus and those with their cell bodies in the trigeminal ganglion can both be Ruffini nerve endings. Furthermore, there was no apparent morphological difference between the two periodontal ligament mechanoreceptors.

The effect of rate of force application on the threshold of periodontal ligament mechanoreceptors in the cat canine tooth.

Mechanical stimuli in the form of ramp-plateau forces were applied to the tip of the crown of the left mandibular canine tooth in cats anaesthetized with alpha-chloralose. Electrophysiological recordings were made from functionally single fibres teased from the inferior alveolar nerve. The force threshold was determined for 34 periodontal ligament mechanoreceptors at different controlled rates of force application. Force threshold was dependent on the rate of force application to the crown tip. Rate sensitivity was present for all receptors across the range from rapidly to slowly adapting; the degree of rate sensitivity was graded according to the adaptation rate of the receptor. The results suggest that the velocity of mechanical stimulus application to teeth needs to be considered in studies involving periodontal mechanoreceptor responses and their reflexes.

The response characteristics of mechanoreceptors related to their position in the cat canine periodontal ligament.

The relation between threshold, adaptation properties and position of these receptors was studied in anaesthetized cats. Electrophysiological recordings were made from functionally single fibres teased from the inferior alveolar nerve as forces were applied to the tip of the left mandibular canine tooth. Receptors were located within the periodontal ligament by paring away the overlying bone. Threshold and adaptation properties were related to the receptor position relative to the fulcrum and apex of the tooth. These results support the hypothesis that there is only one type of periodontal-ligament mechanoreceptor, and that their response characteristics depend on position.

The effect of vibration on the discharge of periodontal ligament mechanoreceptors to controlled loading of the cat canine tooth.

This study observes the maximum 1:1 following frequencies of these mechanoreceptors, as well as their response characteristics before and after vibratory stimuli. Mechanical stimuli were applied to the tip of the crown of the left mandibular canine tooth in cats anaesthetized with alpha-chloralose while recordings were made from functionally single fibres teased from the inferior alveolar nerve. Vibratory stimuli were applied at various frequencies and durations at twice the threshold to that stimulus. Controlled ramp-plateau forces were applied before and after the period of vibration. A temporary rise in the receptor discharge was recorded and the threshold to ramp-plateau stimuli fell to about one-third of its original value. The increased post-vibration response was dependent on the frequency and duration of the stimulus. It is suggested that vibration has some temporary effect on the receptor environment.

Storage of polyacid-modified resin composites ("compomers") in lactic acid solution.

OBJECTIVES: The aim of this study was to determine the interaction of four polyacid-modified resin composites with aqueous lactic acid solutions, and to compare changes with those for a glass-ionomer cement and a conventional resin composite. METHODS: For each material, namely Compoglass F, Dyract AP, Hytac and Ana Compomer, plus AquaCem (glass-ionomer cement) and Pekafil (conventional composite resin), five cylindrical specimens of 4 mm diameter x 6 mm height were prepared and weighed. They were stored individually in 2.0 cm3 of 0.02 mol l-1 lactic acid solution for 1 week then the pH was determined and the specimens reweighed. The lactic acid solution was replenished, and the specimens were stored for a further week, after which the pH and specimen weights were again measured. This was repeated at 1 week intervals until the specimens were 6 weeks old. Differences were analysed by ANOVA followed by Newman-Keuls post hoc analysis. RESULTS: All four polyacid-modified composites increased the pH of the solutions at all time intervals by at least 0.26 pH units (significant to at least p < 0.01). This effect was similar to that of the glass-ionomer (but significantly less, p < 0.05) while significantly greater (p < 0.05) than that for the composite, Pekafil, which, by contrast, had no effect on pH. The observed rise in pH reduced significantly over time (ANOVA, p < 0.05). After 1 week, all pH changes were accompanied by net reductions in specimen mass, indicating susceptibility to acid erosion. Hytac was significantly more resistant to this erosion than the other materials; conversely, it had the least effect on solution pH. SIGNIFICANCE: These results show that polyacid-modified resin composites neutralise lactic acid in vitro but suffer erosion in the process.

In vitro caries inhibition by polyacid-modified composite resins ('compomers').

OBJECTIVES: The aim of this study was to compare the in-vitro caries inhibition of two polyacid-modified composite resins (PMCRs). METHODS: Three standardized class V cavities were prepared in eight extracted human molar teeth. Two of these cavities in each tooth were restored with Compoglass and Dyract according to manufacturers' guidelines. A conventional glass-ionomer cement restoration (Chemfil II) was placed in the third cavity in each tooth as a control. The teeth were submerged in an acid gel (lactic acid, gelatin, thymol, pH 4.5) for 28 days and then resin embedded. Ground sections were examined at x 160 magnification for enamel surface lesion depth, dentine surface lesion depth, wall lesions and evidence of caries inhibition. RESULTS: There was no significant difference between the depths of enamel or dentine surface lesions between the two compomer and conventional glass-ionomer materials. However, both PMCRs exhibited greater wall lesions than the conventional glass-ionomer material indicating less caries inhibition. CONCLUSIONS: These results suggest that PMCRs provide less caries inhibition than glass-ionomer cements.

Caries inhibition by a resin-modified and a conventional glass ionomer cement, in vitro.

OBJECTIVES: The aim of this study was to compare inhibition, in vitro, of a resin-modified and a conventional glass ionomer cement. METHODS: Standardized Class V cavities were prepared in extracted human molar teeth and restored with Fuji II LC (n = 14) or Chemfil II (n = 14) according to manufacturers' guidelines. The teeth were submerged in an acid gel (lactic acid, gelatin, thymol, pH 4.5) for 14 days and resin embedded. Photomicrographs of ground sections were examined for enamel surface lesions, dentine surface lesions, wall lesions and evidence of caries inhibition. RESULTS: There was no significant difference between the depths of enamel or dentine surface lesions between the two materials. No wall lesions were found. CONCLUSIONS: Fuji II LC proved more acid resistant than Chemfil II and both materials inhibited caries in vitro.