Specialist Prosthodontics Bahrain

• Total occlusal convergence of 10–20° is the clinically realistic target for crown preparations; retention falls sharply as convergence rises, and short walls need grooves, boxes or adhesive cementation.
• Margins that invade the supracrestal tissue attachment (formerly 'biologic width') cause chronic inflammation or recession. Keep about 3 mm from the planned margin to the bone crest, otherwise lengthen the crown surgically or extrude the tooth.
• Zirconia FDPs need larger connectors than metal: about 9 mm² posteriorly is the usual minimum for 3Y-TZP. Lithium disilicate FDPs are limited to three units ending no further back than the second premolar, with connectors of about 16 mm².
• Single-retainer cantilever resin-bonded FDPs show fewer debondings than two-retainer designs because differential movement of the abutments no longer stresses the bond.
• Immediate dentin sealing (adhesive applied to freshly cut dentin before the impression) improves bond strength and reduces sensitivity under indirect bonded restorations.
• With a pier abutment, a non-rigid connector is placed so that the keyway lies in the distal of the pier retainer and the key on the mesial of the distal pontic; mesial teeth drift mesially and the connector then seats more firmly.
• Secondary caries of an abutment is the most frequent biological complication of tooth-supported FDPs, followed by the need for endodontic treatment and loss of retention.
• Localised anterior wear without interocclusal space can be restored with the Dahl concept: restorations placed at a locally increased vertical dimension, after which the posterior teeth re-establish contact over months.

1. Abutments, biology and tooth preparation – Fixed prosthodontics replaces or restores teeth with restorations the patient cannot remove: crowns, inlays and onlays, veneers and fixed dental prostheses (FDPs, the current term for bridges). Every fixed restoration rests on three foundations. The abutment must be biologically able to carry load, the margin must respect the periodontium, and the preparation must give the restoration enough retention, resistance and material thickness. This chapter covers all three, because most clinical failures and most exam questions trace back to one of them.
2. Materials, design and the fixed dental prosthesis – Choosing a material for a crown or FDP means matching strength, available space, aesthetics, the patient's function and the luting method. Modern practice offers three broad families: metal and metal-ceramic, glass ceramics (feldspathic, leucite-reinforced and lithium disilicate) and polycrystalline ceramics (zirconia). Each family has typical minimum thicknesses and connector sizes, and examiners test these numbers.
3. Aesthetics, cementation, occlusion and complications – The final chapter follows the restoration from shade selection to the long-term recall. It covers how to choose shade, how to plan veneers so that bonding is reliable, how to lute different materials, how to transfer occlusion, how to treat localised wear conservatively, and what goes wrong over time.
4. Aesthetic analysis and treatment of the anterior teeth – Aesthetic dentistry is a planned discipline, not a matter of taste. The prosthodontist analyses the face, the lips, the gingiva and the teeth in a fixed order, sets goals with the patient, tests them in the mouth with a mock-up and only then prepares teeth. The order runs from outside to inside: face, then smile, then gingiva, then teeth. This chapter gives the reference values that guide that analysis and the least invasive ways to reach the goal.
5. Patient safety, ethics and professionalism in prosthodontics – Prosthodontic treatment is elective, often expensive, usually irreversible and frequently involves many teeth over many visits. That combination creates specific safety and ethical risks: preparing the wrong tooth, dropping a crown into the airway, overtreating a patient for profit, or failing to explain the long-term costs of maintenance. The Qatar specialty blueprint gives patient safety and professionalism together 10 % of the prosthodontics examination. This chapter brings the principles together.

• Guiding planes are parallel proximal surfaces, about 2–4 mm high, that define a single path of placement and removal and add stability and reciprocation.
• In the RPI system the I-bar contacts the tooth gingival to the height of contour in the mesiobuccal area; when the distal extension base is loaded it moves gingivally and mesially and disengages, which protects the abutment.
• A reciprocal arm must touch the tooth before the retentive tip passes the height of contour, so it lies on or above the survey line on the opposite surface.
• Cingulum rests on canines are preferred to incisal rests: the load is more axial, nearer the centre of rotation, and they are less visible.
• An implant placed at the distal end of a Kennedy class I edentulous area turns the distal extension into a tooth-and-implant-supported base, reducing rotation and improving support (implant-assisted RPD).
• Unilateral removable partial dentures without cross-arch stabilisation are contraindicated because of poor stability and the risk of aspiration.
• If pressing on a distal extension base lifts the indirect retainer from its rest seat, the base has lost tissue support and needs relining.
• Flexible nylon dentures lack rigid rests and are difficult to reline or repair; they suit interim use or patients allergic to methacrylates, not definitive tooth-and-tissue support.

1. Classification, biomechanics and the surveyor – A removable partial denture (RPD) replaces missing teeth in a partially dentate arch and can be taken out by the patient. Its design is a balance between support (resistance to movement towards the tissues), retention (resistance to movement away from the tissues) and stability (resistance to horizontal and rotational movement). To design well you must first describe the arch, then understand how the denture moves under load, then plan with a surveyor. This chapter covers those three steps.
2. Components of the RPD: connectors, rests, clasps and guiding planes – Every metal-framework RPD is built from the same parts: a major connector, minor connectors, rests, direct retainers (clasps or attachments), indirect retainers, guiding planes and denture bases. Knowing what each part does and the rules for its design answers most RPD questions.
3. Mouth preparation, special designs, delivery and maintenance – Once the design is drawn on the surveyed cast, the mouth is prepared to match it. Preparation proceeds in a set order, because each step depends on the previous one. Then the framework is tried in, the bases are added, the denture is delivered and the patient enters a lifelong recall. This chapter also covers designs for difficult situations: overdentures, swing-lock dentures, flexible dentures and the occlusion against a complete denture.
4. Maxillofacial prosthodontics: maxillary defects, obturators and speech prostheses – Maxillofacial prosthodontics restores parts of the mouth and face lost through surgery, trauma or congenital defects. Most cases follow cancer surgery. The prosthodontist works within a team that includes the head and neck surgeon, radiation oncologist, speech and language therapist and dietitian. This chapter covers defects of the maxilla and soft palate. The next chapter covers the cancer patient more broadly, mandibular defects and facial prostheses.
5. The head and neck cancer patient, mandibular defects and facial prostheses – Patients treated for head and neck cancer face a lifetime of oral problems. Radiotherapy damages salivary glands, blood vessels, muscles and bone. Surgery removes parts of the jaws, tongue and face. The prosthodontist helps prepare the mouth before treatment, prevents complications during and after it and restores function and appearance. This chapter covers those stages, mandibular resection and facial prostheses.

• The ACP Prosthodontic Diagnostic Index grades mandibular bone height: class I at least 21 mm, class II 16–20 mm, class III 11–15 mm, class IV 10 mm or less.
• The neutral zone is the space where tongue and cheek/lip forces balance; recording it is the method of choice for an unstable mandibular denture on a severely resorbed ridge.
• The mandibular occlusal plane runs from the canine tip posteriorly to about one half to two thirds of the height of the retromolar pad.
• Lingualised occlusion places the maxillary lingual cusps in the mandibular central fossae with no buccal contacts; it suits resorbed mandibular ridges and keeps forces lingual to the ridge.
• Generalised soreness and a mandibular denture that shifts forward usually reflect an occlusal error in centric relation, not a base problem; a clinical remount is the most accurate correction.
• Miconazole is contraindicated with warfarin because it raises the INR; nystatin is the safer antifungal for denture stomatitis in anticoagulated patients.
• Copy (replica) dentures reproduce the polished surfaces and tooth positions of well-adapted old dentures, which helps elderly patients adapt to replacements.
• Christensen's phenomenon is the posterior separation of occlusal rims or teeth during protrusion, caused by the downward path of the condyles; compensating curves allow balanced contacts.

1. The edentulous patient: anatomy, classification and impressions – Complete dentures replace all teeth in an arch and rest entirely on mucosa over bone. They have no teeth to hold onto, so success depends on how well the dentist understands the tissues that support them, the muscles that move around them and the patient who has to learn to control them. This chapter covers the anatomy of the denture-bearing areas, how the difficulty of a case is classified, and how impressions capture the tissues.
2. Jaw relations, tooth arrangement and occlusion – With the impressions done, the dentist must decide where the teeth will go. This requires three decisions: the vertical dimension, the horizontal jaw relation (centric relation) and the position of the teeth and occlusal plane. Then an occlusal scheme is chosen. Errors here cause most problems patients later blame on the 'fit' of the denture.
3. Insertion, problems, special techniques and denture-related disease – Delivering complete dentures is the start of a period of adaptation, not the end of treatment. The dentist checks fit, extension and occlusion, teaches the patient, and then works through the problems that arise in the first weeks. This chapter covers insertion, processing faults, common complaints and their causes, special techniques for difficult patients, and the diseases associated with denture wearing.
4. Overdentures, immediate dentures, copy dentures and digital workflows – The conventional complete denture is made on healed ridges after all teeth are gone. Many patients do not fit that pattern. Some still have a few teeth or roots that can be kept, some need teeth removed and want to leave the surgery with a denture, some are old and frail and have adapted to a worn denture they will not give up, and some can be treated with digitally designed and milled dentures. This chapter explains the logic of each option, when it is indicated and what goes wrong.
5. The older and medically compromised edentulous patient – Most complete denture wearers are older and many take several medicines. Their general health changes the oral tissues, the ability to adapt and the risks of treatment. Prosthodontic success therefore depends on medical history as much as on technique. This chapter covers the conditions examiners ask about most: xerostomia, candidiasis and denture stomatitis, neurological disease, dementia, anticoagulation, antiresorptive drugs, radiotherapy, nutrition and safe use of denture adhesives.

• 2017 case definition of peri-implantitis: bleeding and/or suppuration on gentle probing, increased probing depth and bone loss beyond initial remodelling; without baseline data, bone level of at least 3 mm and/or probing depth of at least 6 mm with bleeding.
• The EFP S3 guideline (2023) recommends non-surgical therapy first for peri-implantitis, then surgery if needed; adjunctive systemic antibiotics are not recommended routinely.
• In the aesthetic zone the implant shoulder lies about 3–4 mm apical to the planned mid-facial mucosal margin, slightly palatal, with at least 2 mm of buccal bone.
• Between two adjacent implants the papilla averages only about 3–4 mm in height, so adjacent implants in the aesthetic zone should be avoided where possible.
• Excess cement is a common cause of peri-implant disease; screw retention or a margin at or above the mucosa is preferred when margins would be deep.
• Implants are contraindicated in patients receiving high-dose intravenous antiresorptive therapy for cancer because of the high MRONJ risk.
• Implant-protected occlusion: light or no contact under light bite, even contact under heavy bite, no excursive contacts on implant crowns where possible, narrow occlusal tables and central loading.
• Short implants (6 mm or less) in the atrophic posterior mandible achieve survival comparable to longer implants after vertical augmentation, with fewer complications.

1. Patient selection, risk and treatment planning for implants – An implant is a titanium or zirconia root analogue that becomes anchored in bone by osseointegration. Osseointegration means direct structural and functional contact between living bone and the implant surface, without an intervening soft-tissue layer. Unlike a natural tooth, an implant has no periodontal ligament. This single fact explains much of implant prosthodontics: an implant cannot move physiologically, gives little proprioceptive feedback, cannot migrate to relieve load, and has a connective tissue seal that runs parallel to the surface instead of inserting into it. The prosthodontist plans the restoration first and places the implant where the restoration needs it. This is called restoration-driven or prosthetically driven planning.
2. The aesthetic zone, soft tissue and implant components – In the anterior maxilla success is judged not only by survival but by the appearance of the mucosa. The goal is a mid-facial margin at the level of the contralateral tooth, papillae filling the embrasures and no grey shine-through. These depend on three-dimensional implant position, bone and soft-tissue volume, and the restorative components.
3. Biomechanics, occlusion and multi-unit implant prostheses – Because implants lack a periodontal ligament, forces are transmitted directly to bone, mostly at the crest. A natural tooth intrudes about 25–100 micrometres under load; an implant moves only about 3–5 micrometres. This mismatch, together with reduced tactile sensitivity, guides how we design occlusion and frameworks. Overload rarely causes bone loss in a healthy, plaque-free site, but it is a major cause of technical complications: screw loosening, abutment fracture, veneer chipping and, rarely, implant fracture.
4. Peri-implant diseases: diagnosis, treatment and maintenance – Peri-implant health, mucositis and peri-implantitis were defined at the 2017 World Workshop. Peri-implant mucositis is inflammation of the soft tissue only: bleeding and/or suppuration on gentle probing, with or without increased probing depth, but no bone loss beyond the initial remodelling that occurs in the first year. It is reversible with plaque control. Peri-implantitis is a plaque-associated pathological condition with inflammation of the mucosa and progressive loss of supporting bone.
5. Surgical complications, mishaps and the evidence for implant decisions – Implant treatment has high survival rates, but complications are common enough that every clinician must prevent, recognise and manage them. Complications are usually grouped by time: during surgery, early (before osseointegration) and late (after loading). They are also grouped by type: biological, technical and aesthetic. This chapter covers surgical mishaps, early failure, technical problems and the evidence that should guide treatment choices.

• DC/TMD Axis I: myalgia requires pain in the masticatory muscles modified by jaw function and familiar pain on palpation or opening; myofascial pain with referral adds pain referred beyond the palpated muscle.
• Disc displacement without reduction with limited opening: history of locking, maximum assisted opening below 40 mm including vertical incisal overlap, deflection to the affected side.
• The 2018 bruxism consensus grades bruxism as possible (self-report), probable (self-report plus clinical findings) or definite (instrumental assessment, polysomnography for sleep bruxism).
• A stabilisation splint is a full-arch hard acrylic appliance with even contacts in centric relation and canine guidance; irreversible occlusal adjustment is not recommended to treat TMD.
• Steeper condylar guidance and steeper anterior guidance allow taller posterior cusps; a larger immediate side shift requires shorter cusps and wider fossae.
• Mutually protected occlusion: the posterior teeth protect the anterior teeth in maximum intercuspation, and the anterior teeth disclude the posterior teeth in excursions.
• Magnetic resonance imaging shows disc position and joint effusion; cone-beam CT shows osseous changes such as flattening, erosion, osteophytes and subchondral cysts.
• Chronic TMD with widespread pain, poor sleep and distress suggests central sensitisation and needs a biopsychosocial approach: education, self-care, cognitive behavioural therapy and, if needed, low-dose tricyclic antidepressants.

1. Functional anatomy of the TMJ and mandibular movement – The temporomandibular joint (TMJ) is a ginglymoarthrodial joint: it hinges (rotation) and glides (translation). The mandibular condyle sits in the glenoid (mandibular) fossa of the temporal bone, in front of which lies the articular eminence. Between them is the articular disc, a biconcave plate of dense fibrous connective tissue without vessels or nerves in its central intermediate zone. The disc has a thick posterior band, a thin intermediate zone and a thinner anterior band. In the normal closed position the posterior band sits at about the 12 o'clock position on top of the condyle.
2. Occlusal concepts and determinants for restorative work – An occlusal scheme is the planned pattern of tooth contact in closure and in excursions. For dentate patients the reference concept is mutually protected occlusion: in maximum intercuspation, the posterior teeth carry the vertical load and protect the anterior teeth; in protrusive and lateral excursions, the anterior teeth (incisors and canines) guide the mandible and immediately disclude the posterior teeth, protecting them from horizontal forces. Posterior teeth tolerate axial loads well; anterior teeth have a favourable position far from the muscles and good proprioception to manage lateral guidance.
3. Temporomandibular disorders and bruxism: diagnosis – Temporomandibular disorders (TMD) are a group of musculoskeletal and neuromuscular conditions affecting the masticatory muscles, the TMJs and associated structures. They are the most common cause of non-dental orofacial pain. Diagnosis follows the Diagnostic Criteria for TMD (DC/TMD, Schiffman 2014), which has two axes. Axis I is the physical diagnosis based on history and a standardised examination. Axis II screens psychosocial status and pain-related disability (for example the Graded Chronic Pain Scale, PHQ-4 for depression and anxiety, jaw function limitation scales). Both axes matter, because psychosocial factors predict chronicity.
4. Management of TMD: splints, conservative care and chronic pain – Most TMD is self-limiting or fluctuating, and conservative, reversible treatment helps most patients. Irreversible treatments such as occlusal adjustment by selective grinding, orthodontics or prosthodontic reconstruction aimed at curing TMD are not supported by evidence and are not recommended. The occlusion is not the main cause of TMD, and changing it permanently may create new problems.
5. The worn dentition and full-mouth rehabilitation – Tooth wear is the loss of hard tissue by processes other than caries or trauma. It is common, increases with age and is becoming more frequent in young people because of acidic drinks and reflux. Most wear is slow and needs only monitoring. Severe or rapid wear, however, can lead to sensitivity, poor appearance, fractures and loss of crown height, and may need complex rehabilitation. This chapter covers diagnosis, monitoring and the principles of restoring a worn dentition, including how to manage vertical dimension and choose the reference position.

• 5Y (cubic-containing) zirconia is more translucent than 3Y-TZP but has lower flexural strength and little transformation toughening, so it needs thicker sections and larger connectors.
• Low-temperature degradation of zirconia is a slow tetragonal-to-monoclinic transformation in moisture that roughens the surface and can reduce strength.
• Gracis 2015 classifies ceramics as glass-matrix (feldspathic, leucite, lithium disilicate), polycrystalline (alumina, zirconia) and resin-matrix (resin nanoceramic, polymer-infiltrated ceramic network).
• Polished monolithic zirconia causes less antagonist enamel wear than glazed zirconia or veneering porcelain; adjusted zirconia should be polished thoroughly.
• Polyether is stiff and hydrophilic and absorbs water, so impressions must be stored dry; it is useful for implant pick-up impressions.
• Intraoral scanners are as accurate as conventional impressions for short spans, but error increases over full arches, especially for multiple implants.
• Titanium castings form an alpha case, a hard, brittle, oxygen-enriched surface layer from reaction with the investment, which must be removed.
• Printed resins for dentures and splints must be cleaned and post-cured as specified, otherwise residual monomer and poor mechanical properties result.

1. Dental ceramics: classification, zirconia and material choice – Ceramics are inorganic, non-metallic materials. In the mouth they offer aesthetics, biocompatibility and chemical stability, but they are brittle: they have high compressive strength, lower tensile strength and limited ability to resist crack growth. Two properties guide clinical choice. Flexural strength (MPa) describes the stress at which a test bar fractures. Fracture toughness (MPa·m^1/2, K_IC) describes resistance to growth of an existing crack, and for brittle materials it is often the more meaningful number, because failures start from flaws.
2. Impressions, digital workflow, gypsum and resins – Precision of the final restoration begins with the impression. Elastomeric impression materials used in prosthodontics are addition silicone (polyvinyl siloxane, PVS), polyether, condensation silicone and polysulphide. Their key properties are accuracy, dimensional stability, elastic recovery, tear strength, stiffness and wettability (hydrophilicity).
3. Metals, alloys, titanium and resin bonding – Dental casting alloys are classified (ADA) by noble metal content: high noble (at least 60 % noble metal with at least 40 % gold), noble (at least 25 % noble metal), and predominantly base metal (less than 25 % noble). Noble metals are gold, platinum, palladium and others of the platinum group; silver is not counted as noble in this classification. Base metal alloys such as cobalt-chromium and nickel-chromium are stiffer (high elastic modulus), harder and cheaper, which suits thin long-span frameworks and removable partial denture frameworks, but they are harder to cast and adjust. Nickel can cause allergy, especially in women.
4. Luting cements and adhesive cementation – A luting cement fills the gap between a restoration and the prepared tooth or abutment. It must flow into a thin film, set in a controlled time, resist dissolution, and, depending on type, either rely on mechanical interlocking or bond chemically or micromechanically. The choice depends on the retention and resistance form of the preparation, the restoration material, the ability to isolate the field and the patient's caries risk. This chapter compares the main cement families and explains the bonding protocols for different substrates.
5. Physical and mechanical properties, biocompatibility and material testing – To understand why a ceramic chips, why a denture base cracks or why a clasp fractures, you need the basic language of material science. This chapter defines the properties examiners ask about, explains how they are tested and links each property to a clinical decision. It then covers biocompatibility, allergy and the standards that govern dental materials.

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Los temas principales son Fixed prosthodontics (20 %), Implant prosthodontics (20 %), Removable partial dentures (15 %). El curso abarca 6 temas con 30 capítulos en total.

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